Is over "stiffness" of a boat that desirable

Over stiffness in structures can lead to more problems than solve, glider design ( who probably lead the world in composite construction ) have now gone away from very stiff structures, it was leading to structural failure at key points ( stress fractures ) and many pilots felt that they were taking such a physical battering, they couldn't cope physically over longer flights. Food for thought and I would guess the super stiff boats must be nearing this point or is boat design still catching up.

Stiff..... http://www.youtube.com/watch?v=TGyDd_3Eoug&NR=1

I have always seen boat stiffness as a field of diminishing returns. Each progressive step (increase in stiffness) results in less gains and at some point the additional increase is simply not worth the effort (cost).

Therefore, it is my opinion that the best approach is to find a good optimum here. One where the stiffness is sufficient to provide for a nice sailing feel and good performance without going overboard with respect to say weight or costs.

Just to give an example ; a 180 kg F18 can be made very stiff and perform well with that but I doubt that any such stiffness increases are enough to results in more performance then say a slightly less stiff but 30 kg lighter platform of the same dimensions.

Boat design is always a game of balancing one benefit (or drawback) against another. The designer who does this the best will produce the boat that performs the best over a wide range of conditions and thus be most competitive in the long run.

Wouter

in BIG boats there is still a never ending search for stiffness. Punching through waves a volvo 70 will still get a slack forestay.
The latest America's cup multi's were still capable of producing more power than their structure could handle.

So scale up and stiffness becomes more of an issue.

*yes that is very "stiff"

Now scale everything down (as we did on the F16's) and ... !

Wouter

Nice reposte Mark, your library of videos is uber cool

As an engineer going for the ultimate goal always incurs penalties of some form or other. My worry is that we are totally into trying to get the ultimate platform stiffness but incurring penalties such as weight and cost for what may or maybe not be small incremental gains.

But will we push through the point where it suddenly gives problems to us as humans. I remember flying a pretty state of the art glider in the 90's with carbon wings, it was so stiff that every bit of air turbulence was transmitted into the **** and litterally was jaw chattering at times. Flying the less state of art glider with glass and carbon was like flying a comfy arm chair where you could feel every thermal and puff of uplift. Now myself and others were pretty agreed that over a day the softer platform would be a much more forgiving and hence better aircraft to fly.

There is only two downsides to making a platform more stiff.

1. It generally costs you some weight
2. More fatigue on other parts. Something has to give, or at least it will more expose weaknesses in parts.

You get more of a return from stiffening up the platform, than removing weight.

You can't state that without including some quantification.

I'm quite sure a F18 that is 50 kg lighter and only "invest" a 1% loss of stiffness is going to be faster overall then the regular F18.

There is always a balance point to be found somewhere. A point where the effects of one change are not enough to counteract the effects of another (but linked) modification.

Wouter

ok some real life reports about stiffness:

one or two years ago, I tried to use dyneema for the shrouds. Because of the creep, I never could setup the rig as tight and stiff as with wire. It felt different, but it wasn't slow. I run the same speed, the same vmg. But the stiffer rig felt much better, more precise and predictable.

Some years ago, when I did a load of road cycling, there was a huge trend to stiffer frames claiming for a more efficient transmission. I had a stiff bike and a very flexible one. You could really feel the difference, but I could never messure any difference in speed. Funny enough, some time later, there was new trend to new super light weight wheels with 16 or so spokes. Everything you gained with the frame you lost with the wheels. Most people still was convinced that the "stiffer" bike was faster.

I remeber some peolple quoting to must have a low stretch sheet material, and now on some A-class the trend is to use a mid sheeting, supported by the floppy trampoline...

Wasn't the mast section of the Fx-1 too stiff to tune the sail adequately for a single hander? Never sailed one seriouly but was is your expierience with it?

Cheers,

Klaus

Just repeating what I've been told by some one who knows cats well.



Yes, it was too stiff, barn pole stiff in fact. I wasn't clear I guess, I was thinking more just the hulls/beams, and not neccessarily the rig. Although a flexible set of blades/rudders doesn't sound too appealling either.

So referring to bikes on a sailing forum.
The stiffness was very important in the bb for power transmission and also solving the down hill wobbles a major problem with some designs.
The wheels are moving so the weight savings in wheels are seen as very important- particulary the rim,tyre,tube combination as they are the furthest away from the centre of rotation. less spokes doesn't solve this problem in many cases as the rim has to be built stronger, but they look nice.
Back to boats, in Australia we have carbon rudder boxes mated with foils that are heavier and more expensive than aluminium but they're popular because they have the "porn" factor

And still Eddy Merckx did his one hour record on a ultra flexible frame, and light btw, but he was cycling on flat indoor race track.
Once my friend asked me, if I can give him my new aero wheels (flat spokes, v-shaped rim). After the race he told me, he pushed harder, because of the better wheel. Some weeks later the wheels among others were mearsured by a German university. They had the highest drag and was among the heaviest.
But they look good, I still use them. It is the placebo effect who counts more than 100gr and 1 or 2 drag counts. It is all about believing like religion.

Keep always one hull out of the water, than you don't need to care about stiff beams.
As an aerodynamic specialist, I can tell you that you can neglect the stiffness of the boards and rudders. Catsailor are so stupid and mount tons of lead on tip of a daggerboard.

So it boils down to hull stiffness, which is not a problem for beach cats with sandwich skins. I remember my Dart 18 and early Ts were a bit flexible, but nevertheless fast boats.

Cheers,

Klaus

Yes, that is my opinion (and another example were using an F18 component on a non F18 design didn't work out). Some consider the Superwing alu mast we have as a noodle but it sails like a dream. Especially when compared to the FX-one setup.

Again, it is in de balancing between the mast and the sailcut. That is the true pathway to success.

Wouter

Bike frames are quite a good example of what I am wondering about. 20 years ago we were building the first of the real MTB ( off road) bikes out of steel, really supple and bendy, gave the really poor first generation suspension a bit of hand and the overall package was a quite supple but user friendly bike. I still have the bike 20 years on and still no sign of frame breakages or stress fractures.

Now I've since had two very stiff aluminium frames with pretty top class suspenders on, great bikes, but already I have broken both frames at the critical stress points.

My latest frame is built like a barn door weighs a ton but is considered to pretty bullit proof, and then I look at my skinny little lightweight bendy steel frame and think have we got things right here.

The Tornado got faster, as they got stiffer.

Sounds like you are saying that tornados got faster because they were built stiffer. Can you prove it? Tornado teams from the 84 games through 92 are still undecided.

For those who dont know those years were the transition period. State of the art was Gougeon cold moulded hulls and small diam beams. The boats from Goran was not faster in the beginning but they did not break all the time. The boats from sweden might also have been just a tiny bit faster in chop but the difference was probably in the maxed hull volume of those hulls. What killed the woodies and small diam beams were not performance but reliability, and initially price.

Keeping the rig stable is what makes the difference. I have not seen theoretical or real life proof on what is faster. A platform that bends and moves softly in seas or a stiff one bouncing and crashing through waves.
In flat water it makes no difference at all. Sailors are like sheep at times, following the leader instead of asking the whys and hows.

Bundy is smarter than jumping into this. There is no winning game here, only ways to loose business. The rest of the AHPC gang should take note and act as if they had brains.

And by the way. Those cold moulded cedar hulls from 83 are still as stiff if not stiffer than Gorans spaceships and still at min weight.
Talking about carbon masts, carbon hulls and carbon crap is pretty silly. Good engineering and skilled builders is what it takes to build anything good. Even wood can outperform a fresh engineer who throws carbon at whatever challenge he see.
Set untrained farmers to laminate hulls and it takes half a year before they have the skills. Then they are due a raise so they get replaced.
What really is discussed here is how to maximize profits. The rest is smoke, mirrors and spin as Wouter says. Smart butt spin doctors making stir fry to paint a pig.

I would buy US made at min weight.

an idea...

drop a state of art F18 rig on a B2 platform and see how far we have really come in platforms.

Be an interesting test but what would be interesting is to time the boat around successive courses, I think you would be surprised at how little the differnce there would be.

Certainly the Stealth which I have has got stiffer over time, largely due to better reinforcing around the beam areas, is the latest boat any faster than the older boats, certainly they feel different in handling, but around the race course the oldest boats still can win pretty regularly.

My main concern though is to stiffen a structure then you put increased loadings on other areas which then in turn means they have to be beefed up to take the loadings. I would guess it has to be a balance between immediate pleasure ( better handling ) or long term pain ( increased weight and perhaps less long term durability )

This thread is awesome, you are seriously debating if stiffer is slower?


Then we have the theory that wood is as good as carbon to build a boat with?? try building a M20 in wood at the same weight and stiffness...
I heard that Groupama are looking at wood as an solution for their new VO70 and BMWO are planning to limit the use of exotic woods for the next americas cup.... If you seriously think that you can build the same weight for weight stiffness in wood compared to carbon then you are certainly on drugs..

Macca the parallels between you and Frank Lord over on SA is just so similar. At least he has now done the honourable thing and left the foiling topics alone to be discussed rationally.

Macca:
But how do you explain the design of BMWOs Dogzilla?
According to the designers they decided that a bendier platform is faster in certain conditions.
Alinghi was extremely stiff even up to a point where it was causing damage.

Read again, it is about stiffer is not automatically faster.
By what physics a beach cat should be faster, if it has stiffer beams?

And by the way, did you know that Gougeon 60ft Proa Slingshot weighted 1800lbs, build in wood 1977 or 1978. Compare this with a 40ft Marstrom x40.
For smaller boats wood is an excellent material, and if used correctly can be lighter than CFRP in some areas.

Cheers,

Klaus

Stiffer:- maintaining rig tension....

how did the slingshot go upwind? in waves?

Ever picked up a boom from an X40? its not so heavy for the amount of load on it..

Doug Lord was banned by SA. Nothing honourable about that. And things were certainly not rational when it came to his topics. When he tells the Moth world champ he doesn't know what he is saying, certain amount of delusion.

And stiff is good.

One the things Sailcraft of Canada did starting around late 70's was adding more bulkheads which increased sales by the way. One of many that made a huge difference was the one about 20 inches in front of the main beam. SoC had taken measurements and found the cantilever load at this location distorted the hull section. My T without the bulkhead toed in 2 inches, my friends with the bulkhead toed in 3/8" with the mainsheet full on. The beams were the same. Less toe in is faster.

Haven't we reached the point with Macca that often the threads aren't rational any longer to the common sailor but rational to Macca, one of the party has to be "delusional", in your words not mine. From experiance of some fifty odd years of life I can only say that very often world champions make poor communicators and have a poor understanding of the needs of those much further down the chain ( those who actually buy all the goodies and thingies which keep the world champion as world champion ), in Bora's case he has been very good at promoting and helping those involved in foiling.

On the subject of stiffness, yes any rig tension is good and maintaining that tension is a good thing. But to do that will have far reaching consequences, at some point we will have to admit that further " stiffness and that is such a terrible decription of what we are talking about ) will have no further gain or limited gains without harming the structure overall.

When designing the boat I built I always envisaged a central beam taking all the rig loads including the forestay and an x beam ( plus single tube rear beam taking the side loadings, the AC then started to use a Y beam with additional wires as support. My reasoning was that for the extra 4-5 kilos of central beam the reduced loadings on the hulls and beams would easily be compensated. There were other advantages taken from windsurfing of allowing the mast base to slide forward (and sideways to reduce righting moment ) on the upwind legs. Time limits and cost dictated that this was just an idea but perhaps this year I might have a go.

Wood can be just as good as carbon if it is built correctly. It will never be as stiff and light as a composite carbon / glass structure in my opinion but I have seen many a discussion on this on the internet with arguments for and against such that if you take all things into account such as cost and availability, in small boat building it is a very good material to use, take the many Blade projects within the F16's as an example.

Firstly there is no such thing as over stiffness in a catamaran platform. Any one that sails hobie 16s at the top level will tell you that. The h16 platform is bendy no matter what you do to it but it has been proven to death that a stiff 16 is a fast one. Don't bother rocking up to an Australian h16 nats if your boat is not glued together and your tramp is not as tight as you can pull it. You'll be lacking boatspeed if you do. Basic lessons about catamaran sailing need to be learned by a fair few of you guys.

Secondly comparing macca to Drug Lord is just stupid. Unlike druggie Macca can walk the talk. What druggie and Macca share is that they are both characters. Every sport needs characters or it would quickley get boring. I put forward the opinion that anyone who doesn't think very carefully about bagging out macca is being Irrational.

Got any proof of your claims that are not anecdotal? Would be very interesting but I dont think you got them.
Nice of you to say that multiple olmpians and world champions of multihull sailing need to be get some basic catamaran sailing lessons. Perhaps you better pull your head out of your butt and realise that you dont know it all?


Characters have redeeming character traits. All I see in macca pacca is a FIGJAM offering nothing but abuse and bad PR while indirectly pushing the AHPC product.

Yep, there is no proof that a stiff (glued & super tight tramp) H16 is faster than a soft one.... so why do people bother? I think NASA should do a study on the subject.

I'm not aware of any multiple Olympians or world champions in multihulls that would say that a stiff boat is not faster than a soft one. Got any proof otherwise? The only World champ I know from the H16 said that you should always have a fresh boat for a nationals (ie, dont take a 2 year old boat to a nationals because its not as quick as a new one..) Maybe they get too stiff over that time and hence slower???

As for me offering abuse, I think you will find that I am staying relatively calm in a face of outright abuse from people such as yourself resorting to name calling and labeling.

First of all, are we taking advice on boat design from Hobie 16 Single Manufactorer One-Design sailors ?

Many designers still scratch their heads over the "unique" design choices made with that boat.

Other then that your example only explains that a badly designed platform with unbelievable amounts of flexibility is not what we are looking for. Not that "overstiffness" is impossible.

In fact ORMA tri designers and those of larger offshore multihulls tend to disagree with you and your H16 sailors. Now, please don't make the error of putting up the strawman argument that these designers are saying to lots of flexing is good, they don't. They are mere saying that overdoing it on the other side of the spectrum is not desireable either. As so many times in life the optimal point is somewhere in the middle of both extremes.

Other then that your argument resembles the situation where a man who is exhausted from thirst is best helped by thowing him into a large lake. I dare wager he will die either way. If one thing is "not good" then chance are that 100% of the opposite is not good either.

Wouter

Are you really claiming credit for admireable personality traits after having been the main abuser yourself for years ?

Man, your FIGJAM complex really doesn't know any bounds does it ?

Truly unbelievable !

Wouter

"Perhaps you better pull your head out of your butt and realise that you dont know it all?"

Might be time to take some of your own advise buddy.

Wouter. When i sold my H16 it had significantly less flex than the "minimum wieght" F16s ive checked out.

I can quantitatively prove this but that would get me in trouble.

Tris don't need to be stiff to maintain rig tension or to keep their bows facing the right way.

I stumbled on this thread and initially thought it was just a p**s taking exercise. After reading it carefully and a few other threads on this part of the forum it seems there are some people who actually believe there are no speed advantages for stiffer OTB cat platforms.
Those with short attention spans please continue Twittering - for the rest grab a cuppa and I'll offer my views.
I come from a background of thirty years sailing OTB cats at regional, national and world level. I've built and refurbished both timber and foam sandwich boats.
I note the undercurrent of personalities here and provide the disclaimer that I don't know Macca but have sailed against his Super Taipan with Griffo as skipper.
I'll ignore the red herrings in comparisons with gliders and bicycles. The references to mast stiffness are also irrelevant as masts should be matched in bend characteristics, to sail shape, boat type, sailcloth, crew weight, usual sea conditions etc. That is where the beauty of carbon masts comes in. They can be laminated to suit the exact needs.
Platform stiffness though I believe has a significant impact on boatspeed, particularly on acceleration and through choppy water. Going back to basics, the platform is the structure which transmits the power of the rig to the lateral resistance provided by the hull and the foils in the water. Any bending or twisting in the platform absorbs energy which would have been applied to forward motion by a stiffer platform. The class I know best is A Class cats where stiff platforms are the holy grail. The sloppier platforms simply don't cut it - the stiffer platform just inches forward in each gust as the acceleration is more efficiently applied.The timber boats we built in the eighties just could not be built as stiff as foam boats and the last timber A to win a worlds was Billy Anderson in 1980. I agree that stiffening one area sometimes leads to showing up a weakness somewhere else. Simple - beef up the weak area - thats development.
As far as Tornados are concerned, if a cedar T is so stiff where are they over the last twenty years in the Olympics and Worlds. Haven't seen them winning there.
I agree with Aido about H16's. In the eighties the Metcalfe boys pretty much dominated World titles in 14's, 16's and 18's. They had a standard procedure with the supplied boats. It revolved around making the boats as stiff as possible in the short time available. Even to this day the local and very experienced Hobie dealer sets each new 16 up to improve stiffness over the standard factory delivery.
The recent AC saw Alinghi use significant structural bracing to get platform stiffness. Oracle mainly kept it's centre hull as it gradually morphed in to a cat so that it was stiff enough to limit forestay sag
It is true that building stiffer platforms has diminishing returns. However in a restircted development class you would expect people to keep trying for that extra bit. That's the beauty of formula development. Look at the F18's. Would you rather sail the latest C2, Infusion or Wildcat as opposed to the first Tiger with pinhead sail and fat boards and not so stiff platform.
Now, cuppa finished and off to the shed to do the winter maintenance on a bloody timber boat.

Cheers

There are so many arguments against the platform being overstiff outside of sailing, for instance why do rally cars have suspension, mtb bikes, its all about using the power from the rig, engine, human wisely and efficiently. Having an over stiff platform will simply transmit that efficient power into unefficient areas.

I do suspect however that the platforms of the past have been so poor in terms of stiffness that we are now playing catchup and learning that stiff platforms are good. Where do we go then, in design terms it would have to be the end of the two beam setup as just in engineering terms they will never be able to cope with the torsional loadings without being over engineered.

Agree we need to be more innovative in improving platform stiffness. I have two OTB cats designed in the 60's which have three beams which helps bow stiffness and forestay stability. Also larger cats often have three beams. The Alinghi approach with diagonal strengthening is interesting. We've been gluing beams in A's since the eighties and some recent designs have beams integrated with hulls. There must be plenty of ways yet to be implemented for extra stiffness. I tend to disagree that you can overdo it, cost and weight notwithstanding.

Cheers

Hello pot......

Oh, and well said ACE. I have never met a half decent OTB cat sailor that does not think stiffer is better. But let them believe what they want to.

That's a bit harsh Wouter. Some very good sailors have campaigned H16's over the years. They weren't reponsible for the design - the example was about how people with relevant skills were able to improve the performace of an OTB cat by stiffening the platform. I believe the "better" designs still have some improvement in them. There is still twist in the platform of the best A's on the bearaways going wild and I'm sure the kite boats get twist when bearing away wth a gust downwind. It would be good to utilise that lost energy. What is overstiffness and how do you measure it? I would think everyone would want to transfer the power of their rig to the water with no loss - we aren't there yet.

SOME stiffness is good. The stiffness of a component or complete platform is just like every other feature in a boat’s design; it is compromise for one feature over another. To universally apply “stiffness” as something that is better no matter what is a false premise, same as saying more hull volume, or weight or anything other item is universally better in all conditions.

A telephone pole stiff mast has a very limited useful wind range. Composites under load will flex some and if they do not then there are stress concentrations that will fail in time, unless the structure is just totally overbuilt for its conditions (read weight). There are a lot of water forces acting on a boat and not very many of them are in a useful direction to help our sailing. With a very stiff platform these are transferred to the rig. “Shaking” the rig disrupts the wind flow, which is bad for your performance. So now we dampen the rig or sail or something else to make up for the added “negative” forces imparted with a super stiff platform.

Do not get me wrong, I will sail on a stiffer boat given a chance, but it is not a universal constant that makes everything better.

Ok, I admit, I have sailed uni rigs for so long, that I forgot about the sagging jib. Well, take higher gauge bridle wires and stiffen the hulls in front of the front beam, and your job is done... or sail uni.

And by the way I touched a X40 boom as much as you sailed on Slingshot .
I would never propose to replace a CFRP boom or mast by wood. But a wooden hull of a small beach cat... as long as you or your builder knows how to build it. Today it is hard to find someone who can.

Oh wow, a boat is a black whole which absorbs energy. Did you ever thought what happens, when structures reflect after removing a load?

Oh wow, a boat is a black whole which absorbs energy. Did you ever thought what happens, when structures reflect after removing a load? [/quote]

I think you may have misunderstood what I was saying. The structure of the platform absorbs the energy as it twists. As it flexes back again not all that energy is transferred to smooth foward motion. Some of it simply results in the boat bobbing up and down in the water. The objective is to not have that twisting and untwisting motion at all so all the energy is applied to forward motion. Much as we try to sail a boat as smoothly as possible in choppy water by such things as footing off a bit, powering the rig up slightly and structural things like lighter masts and sails.
If the theory of not worrying too much about flex in platforms were correct we would all be happy sailing two year old Hobie 16's!

It's only a problem if it lasts over 4 hours!



Stiffness is preferred as long it is not to the extreme. As a reoccurring theme on this forum, we can always come up with examples and analogies that are exceptions. Absolutes are never the rule.

Another view on platform stiffness from someone who might have a clue about these things. This is from a recent published interview with Bob Baier, current German A Class number one and current European champion.

"In my opinion, what is crucial here is simply the honeycomb construction. Here you have much greater stiffness than on a foam boat. Although I am no boat builder, I notice this in the steering. On a stiff boat, one has the feeling that the boat is moving as a single unit. The hulls do not work against one another, rather they move synchronously through the waves, which is how it should be."

The class rules in F16 don't seem to define or measure stiffness. So this seems an area of unrestricted development which would be persued by builders over time. The Viper seems a step ahead in that area. It has certainly provided some impetus for F16 in the so called land of the dog. Before it came along F16 was going nowhere here.
Cheers

Wouter, you either don't know are are not telling the full story with the ORMA 60 issues.

The reason they had to allow the boats to flex was simply that they could not make the entire structure stiff and strong enough without developing a hard spot in which the failures occurred. Generally this was in the float to beam joints. The boats that had this problem were the full nomex cored boats that were stiffer (and faster) than the foam core boats. So then they moved to a mix of nomex and foam to ensure the longevity of the boats. This was a compromise with the speed... I will say this very clearly: The foam (softer boats) were not as quick as the nomex (stiffer) boats.

On a small beach cat where you can build a very stiff platform without the risk of breakage in 10 meter seas.. Stiffness is good, simple as that. But it costs.... I think I have stated many times in here that a full nomex cored, carbon boat will be stiffer and faster than a foam core, carbon boat.

This would appear to be in line with the statement of Bob Baier and I think any of the top level sailors will agree. You can however continue to think otherwise, it makes no real difference to the world of sailing as you are never on the water anyhow..

I love coming to the forum..

I haven't read all the comments but I cant believe people are putting up arguments that a stiff platform is not better.

I would go so far as to say it is impossible to have a F16 platform to stiff.

I'm not a engineer, but practically from testing and testing and a bit more testing.. Stiffer is faster.. no question.. Glue it together... next topic!

Fascinating reading the differences of opinions between groups of people. On one hand we have the professional racers saying that stiffer is better regardless of cost. I guess thats the win at all costs attitude which has made them top racers.

On the other hand we have the guys from engineering backgrounds going OK stiffer maybe better but it is at a cost, usually reliability and lifespan of the structure, that argument looks as though it is supported by the Orma 60's "The reason they had to allow the boats to flex was simply that they could not make the entire structure stiff and strong enough without developing a hard spot in which the failures occurred"

So which is it to be then carry on stiffening the boats until things start to break or allow a bit of flex and get longevity of the structure. Coming from an endurance racing background reliability was more important as soon as my bike was damaged I was out of the race. Damage a part of a boats structure and it can mean weeks and months out of action. And that failure maybe not in say the first year or two of the boats lifespan but further down the road.

I'm still not convinced yet that we have reached the balance of stiffness ( ie more stiffness maybe better ) to reliability that is acceptable to most people, but one only has to look at the problems some of the F18's are getting such as bridle mountings delaminating and I guess the weight ( mass )/ strength / stiffness / reliability question is not far away. Its not to say with a slightly revised engineering solution that those problems wouldn't dissappear at the cost of a bit more weight or investment ( stress analysis ).

Nobody is saying that, it is a retorical trick that is played by the side who favours eternal chaos in the F16 class. By the way, I'm not saying that you are part of that side, Darren.

What is said is that increasingly improving platform stiffness is a project of diminishing returns. At one time a point is reached beyond which additional stiffness is not worth the investments.

Compare it to double glassing in your home. A single layer of glass lets out a sizeable amount of heat from your living quarters. Getting double glazing cuts this loss in half. An errrornous but understandable reaction to this gain could be to get 10-double glassing. Afterall, each time the loss is cut by half, right, so more is "always" better !

Yet, we hardly see any triple glassing in the real world and anything beyond that is unheard off. The reason for this is simple. Triple glassing will only cut in half of what was left after cutting it in half the first time. So if the first time the energy savings amounted to a reduction from say 100 to 50 bucks then the second time the reduction only amouted to a savings of 25 bucks. The fourth and fifth times would result only in respectively 12.5 bucks and 6.25 bucks.

Obviously a reduction of 50 points is easily noticed but a reduction of 12.5 points much less so. Afterall it is only 25% of the the first reduction and 1/8th of the total costs initially incurred with single glassing.

Say the first F16's flexed 64 mm when layed up on their sterns with one hull lifted (note that the standard Hobie Tiger and Nacra F18 flexed in this test by 92 mm !). In fact, my homebuild Taipan F16 (small beams) flexes by about that amount. The first Blade (small 80x2 beams) flexed 40 mm and the newer Blades flexed by about 30 mm. The Falcon with newly designed custom beams is stiffer still and the Stealth always flexed in the order of 20-25 mm (was a very stiff boat from the beginning). Lets say the Viper flexes by about half that amount say 10 mm (on a par with the very best all-carbon A-cats and way better then the modern F18's).

Say my own boat losses 60 seconds per hour bouy racing relative to the Viper due to platform flexing alone. This is a huge amount in my opinion but lets assume a large difference for arguments sake. Note how the Viper is over 6 times stiffer then my own homebuild. Using these numbers we can calculate the relative differences between different F16 makes.


Relative differences (rounded off)

30 seconds / hour gain : Taipan F16 to prototype Blade F16 (80x2 beams)
10 seconds / hour gain : Prototype Blade to Alter cup Blade
5 seconds / hour gain : Alter Blade to Stealth or Falcon :
15 seconds/ hour gain : Stealth/Falcon to Viper :

Absolute differences (rounded off)

30 seconds / hour gain : Taipan F16 to prototype Blade F16 (80x2 beams)
40 seconds / hour gain : Taipan F16 to Alter cup Blade
45 seonds / hour gain : Taipan F16 to Stealth or Falcon
60 seconds/ hour gain : Taipan F16 to Viper F16


So obviously, this example does not disproof that in the F16 situation more platform stiffness makes a boat faster. That is NOT the point. The point is that a gain of 15 seconds between the new generation F16's and the Viper F16 is not much at all. Certainly not when running the numbers on loss of performance by putting 23 kg additional weight on the platform (and get to such a high level of stiffness). Who is not to say that that alone losses 10 seconds of the 15 seconds stiffness gain already, leaving only a negligiable difference of only 5 seconds ! Note that Texel handicap system assumes a 4.752 second performance loss per hour bouy racing per SINGLE kg of added weight; resulting in over 72 seconds per hour (2 points) over 22 kg. So anyone may run the numbers of the example above for any number of minutes the difference is between my home build Taipan F16 and the professionally build Viper F16. The end result will be discouraging every single time.

Therefore many of us here argue that platform stiffness on F16's has already progressed so far that the performance differences are too small to matter. The base line stiffness set by the Stealth, Falcon, Aussie Blade and most likely the AquaRaptor as well is already at such a level such that there is simply not enough performance loss due to flexing left to make a big difference.

The very same reason why no-one is ordering quadriple glassing for his home.

Wouter

I didn't realize that other F16 flexed that much. Where did you get those numbers from? I'm going to measure the flex on my Stealth next Saturday as I'm curious now. I have an original Stealth: narrower than the F16 box rule and designed with a custom front beam with no dolphin striker, I wonder how much difference this makes.

I wouldn't lump the F18 with that label. I believe some F16s (as well as other cats) suffering from structural problems also. Mainly during the early stages of development of a new boat or it is a manufacture error, not common to the class and is rectified through dealer warranty. I could pull some pics of some F16 failures if you like, but that would benefit no one.

As for stiffness, I see your point. Too stiff can cause failure in other areas, however I do not believe OTB cats are even close to that. The Viper is very stiff. It could be made stiffer again and much lighter but that would come at a cost. To some, they would not be willing to explore those limits. To others, if the prize was great enough, then they will go to extraordinary (including financial) lengths to achieve their goals.

The other current F16s are close to minimum weight but could do a lot more work in the platform stiffness department. If the higher volume hulls are more beneficial, then they could do further work there...... however it would come at a great cost.

Raising the minimum weight will not solve this problem (at least alone). The reduced use of exotics is the only way to keep the cost in check. The class has not seen this yet because it is still a very small class produce predominantly by small localised manufactures and are nearly invisible on the sailing scene despite being perhaps the most visible on the internet. If the class really starts to make a strong presence on the water and attract much larger fleet numbers, increase competition, then this will change.

Correct, however this point will vary from person to person. One person may be happy with a standard Taipan 4.9, narrow and small beams. The next person may be willing to make a carbon/nomex min weight Viper. You allow this freedom in the rules and someone or even a few may pursue it.

Pepin,

There are different ways in measuring platform stiffness.

The way we (in F16 land) do it is to lay the boat up on its sterns (check it is perfectly horizontal in both planes) and then lift the boat by one bow only. At some point the other bow will loose contact with its support. When that happens lower the boat a little bit till the bow hanging down is just above its support and then measure the difference of the raised bow above its support.

In the past this measurement was performed by F16 enthousiasts for a series of boats. All the gethered data is useful because we used the exact same procedure for each boat.

The boats were : Hobie Tiger, Nacra F18, Reg White Tornado, Taipan 4.9 (both homebuild and AHPC), (Homebuild) Taipan F16, prototype Blade F16, Blade F16 (both VWM and Aussie), Stealth F16.

Interesting detail here is that the Taipans all flexed by as good as the same amount (only a difference of 2 mm over an average of 64 mm). Therefore my WIDER homebuild F16 flexed by the same amount as the AHPC build standard (narrow width) Taipan 4.9. My boat has only modest reinforcements at the beam landings (a few carefully placed strips of carbon fibre cloth) and a 80x2 mm rearbeam instead of the square rearbeam of the Taipan. That was enough to compensate fully for the "loss of stiffness" that is normally related to making a platform wider (30% stiffness loss). Additionally, my set of beams weight a a fraction less then those on the standard Taipans. The prototype Blade F16 used 2 80x2 mm beams and its set of beams was significantly lighter while also achieving noticeably better stiffness (by 33%) then the Taipans (both versions). A similar improvement was again had by redesigning the F16 beams (used on Aussie Blades and Falcons). 1.5 kg increase in weight against additional 40% stiffess. ... etc.

In the end, it is all about careful engineering. Any knucklehead can make a stiff boat by adding 10's of kg's to the beams. A true boat designer does it by careful analysis and being smart.

Wouter

Indeed, I'm very happy with my 64 mm flexing Taipan F16 (when put to the rather heavy flexing test, this is not the flexing on the water while sailing, mind you !)

I would love to have a modern Falcon, Aussie Blade or a Stealth who all flex three times as little as my poor homebuild.

But I don't delude myself in thinking that I can win anything more then 30 seconds per race that way and I admit that my F16 is not very stiff when compared to the new boats. It still sails like a dream though.

You are also right to "the next person" may persue an all carbon/nomex/diamond inlays F16 and indeed I think that is fine as I can buy a competitive boat to his one-off for just 17.500 bucks.

In the end, his glitter one-off F16 will present the biggest example of how to waste lots of good money on what amounts to a gain of 15 seconds per hour racing. When faced with the same choice I think that I will spend my money on expert coaching and lots of training (lost income).

As such the FORMULA F16 class rules will have done their job. For it is not the responsibility of such class rules to prevent stupidity in its class members but to merely level the playing field and allow normal people with normal budgets to have a fair chance.

Wouter

The fact that you keep saying that doesn't make it true.

I posses several stiffness measurements and these do not support your statements at all.

In fact, the modern lightweight F16's are at their worst on a par with the modern F18's.

Nobody seems to bitch about stiffness there so why do you hold the F16 class to a different benchmark ?

Wouter

F18 is 2 foot longer and a lot heavier, so of course it will flex a bit more. The Viper has the same beams as the Capricorn, is shorter and lighter so should flex less.

Wouter

I don't favour "eternal chaos in the F16 class". Neither I'm sure does the current Australian F16 champion who has posted an opposing view to yourself on the concept of "over stiffness". I love formula class sailing - that's why I've been sailing and building in it for over 30 years. I wish F16 every success.
However none of the proponents of over stiffness including yourself have defined what you consider is "over stiff" and how that is measured. Of course as platforms are made stiffer in one area failures will occur in other areas. You simply strengthen or change the engineering in that area. Builders and manufacturers do that all the time - even in SMOD classes. You are in a development class so better get used to it. It's called continuous improvement in 90's management speak.
Your measure of stiffness you set out is only valid for platforms of the same weight and length. Anybody with a rudimentary knowledge of engineering will tell you that you can't compare the bow deflection of an A Class with an F18, a Tornado, and an F16. Weight and length have a big influence there. So taking your figures for F16's in isolation, that is a static deflection under only the weight of the boat - not under stress of the rig in sailing conditions. Your extrapolation of times over an hour of sailing is completely erroneous. The differences would be far greater as the deflection is greater under sailing conditions.
I'm sure F16 platforms haven't reached anywhere near over stiffness yet - whatever that is!!!

Cheers

There are no restrictions in any class as to what can be done within their current rule set. A lot of money can be spent to make the ultimately stiff F18 platform (and this is possible within your rules). Carbon is cheap compared what it costs to develop, engineer, manufacture and a product. Judicious use of carbon to achieve what MAY be considered a better product is often a less expensive alternative than restricting yourself to older technology.

More small builders and individual/groups developing “uber” boats on the side can only help the class. This is free development and experimentation that if it works will make the class better. Small builder development of techniques and material use prove in systems that in time become the standard and all classes (should they choose) have the possibility of benefit. Shy of mounting an engine on one, races are still going to be won by the best sailor.

The few F18 and other guys who keep coming to this forum claiming this class is in chaos and doomed because we are not following their rule set, or placing ridiculous restrictions that do nothing, should look at their own classes. Costs keep coming back, if you really want to limit this; then kill all development. Pick your ride and go 1 design. Look at how many new models of boats are being designed, tooled and marketed to keep on top the leader board. Pro drivers being sponsored so their models sit on top. And probably one of the bigger items, sail and rig development. These are the things that are expensive and manufacturers WILL recover these costs if they stay in business.

Yes, but as the overall displacement of the F18 hulls during a dive is ALSO much larger it NEEDS MORE STIFFNESS too. A F16 will typically sail with only 75% the displacement of a F18 [(107+143)kg/(180+15)kg]. Add to that the larger overall rig loads and the fact that it is wider and has longer hulls which both are providing for larger leverage and you'll see why putting F18 beams on a F16 are basically overkill.

For example, those 100 mm of extra width already makes the F18 platform flex 18% more even if it had the same weight and same hull length as the F16's. Now look at any 3.00 mtr wide Tornado or M20 and the flexing will go through the roof unless the beams are made very large. There are several of such factors that all need to be multiplied with eachother and that quickly adds up. That is also why going smaller (with teh F16's) was such a smart idea, because if going bigger and wider has such detrimental consequences then going small will result in equally large ... ... ...

You see, it is very dangerous to make conclusions about these things without doing the physical modelling. It is most definately dangerous to base any such conclusions on your gut (which many people seem to do anyway)

Some people even see proof for the benefits of stiffness in the very sharp feel of the Viper while sailing. It has a very crisp feel to it I'm sure. Sadly, the same comments are also made when such people test sail my own homebuild Taipan F16; and that one flexes 6 times more then the Viper ! Of course, even at that level its stiffness is (relatively speaking) better then any commercial F18 like the Tiger. Hence, I seriously doubt whether the Viper needs that much stiffness at all.

I forgot to give the Tornado flexing last time; it did 45 mm in the described test setup.

Wouter

I teach engineering for a living mate, what's your excuse ?

I guess you also think that a wave treats a F18 bow that flexes 40 mm downward differently then a F16 bow that flexes 10 mm downward. Afterall, the wave is concious and knows that this is caused by the difference in beam length and overall weight, thus forcing him to behave differently.

I say the measurements are surprisingly to the point. A 140 kg F18 platform flexes more in the test then a 70 kg F16 platform, that is true, but its 340 kg displacement (compared to 250 kg or less for F16) will very much put it under higher loads while sailing too. The same in reverse when comparing to A-cats. Such opposing phenomena go a very long way in compensating for eachother, making the test dependable again.

Besides, the whole idea of stiffness in both cycling and sailboat design is to reduce the amount of energy that is "wasted" in flexing the platform. A F16 with 10 mm flex while sailing leaks less energy that way then a F18 that flexes 40 mm; the causes that result in this difference are of no importance what so ever to the wave.

Wouter

OK, so we've decided stiffer is better, now, my question to the Engineers is: Which shape beam would be stiffer in our application, a round beam or a square beam or a trapazoid? I mean, our beams have (at least) two different directional forces acting on them, up and down type flex, but twisting as well.

If there were some way to make them stay perfectly seated to their hulls with zero movement there (glued, like the A cats) would a box beam twist and flex more or less than a round beam, or oval beam, given the same relative size, weight and wall thikness?

I don't see any racing bicycles built with box shaped tubes, or perfectly round tubes any more, most are oval. I know some of that oval shape is for less wind resistance, but we could all use less wind (and water) resistance when we stuff the front beam into a wave, right?

With dolphin striker or not? Makes a huge difference. If you have a dominant load direction you would go for box section. Since you want not get injured or cut your trampoline, take something with round edges. CFRP should not be build in to tight curves anyway. Common problem, most people think it is material only, but each material needs it specific design.

Apart from a sagging jib, I am still not convinced why I should look so much for stiffness. I agree about the better feel (see my very first post). But as an engineer, I don't have a problem if one hull drops 40 mm or so, as long as I keep one hull out of the water.
For the jib, I would look for stiffer rigging (i.e. rod or dyform) and stiffer front hulls, before I look for the beams.

For the lost energy theory: the energy loss due to flexing structures is lower than 1% (if you bend something you get 99% or more back). A spring in a watch is a nearly perfect energy storage, ask yourself why. So from the little bit energy which is stored shortly in the structure due to bending, you loos only a liitle bit. A little from a little bit is how much?
The best way to improve speed is to concentarte on the import thinks: Skill, sail shape, foil shape, hull shape, deck layout.

and btw, I like the flexing wings of the B777. It saves tons of structureal weight.

Cheers,

Klaus

"I like the flexing wings of the B777. It saves tons of structureal weight."

That and it makes the ride much smoother for me and the peeps in the back!

http://www.airliners.net/photo/Delta-Air-Lines/Boeing-777-232-LR/1702407/L/

Those that can do "do" those that can't "teach"

I have issue with the way your measuring flex.

your test is measuring the flex of the beam, the beam joints and the supporting structure around the joints. but you completely failing to measure the stiffness of the hulls.

for example, when I press on the side of the capricorn it is very hard to make it flex at all but by comparison my old nacra 5.8 was very flexible in the sides.

not 100% sure on how to measure these stiffness levels but they do contribute to the overall speed of the boat!

I pity the poor students then if this is the standard of tripe you trot out as engineering gospel. I'll be sure to advise my engineering student daughter not to consider the land of the clog in her options for a semester transfer. The crafty old b**tard with 30 years sailing and building experience has some very interesting discussions on these things wth the bright young theory bound student!

Timbo is on to it. He now understands most of the sailing world prefers stiffer platforms and has moved on to consider some ways to achieve them.

Klaus - I like your explanation about beams. I think in isolation a round beam is strongest in all directions but then you have to consider the direction of the greatest forces. I think that is vertical. In A's some have approached that issue by firstly making the beam a larger diameter for overall mechanical advantage then having thicker walls top and bottom. This is easy to do with carbon by filament winding. In alloy of course the dolphin striker does the job. In bigger cats the pelikan striker does the same for forebeams subject to forestay load. I disagree on the amount of energy lost though when the platform twists and returns. Unlike the watch spring that return energy isn't applied to the original job - that is forward motion. I think a substantial amount of it is lost by the platform "wriggling" about in the water rather than applying it to smooth forward motion. I certainly agree with you that there are many other very productive ways to improve speed - probably the most significant for most of us being operaor skill. However the topic of this thread was the merit of varying levels of boat stiffness. I believe a good sailor on a stiffer platform will always beat an equally good sailor on a less stiff platform.

I'm over this now - off to sail on my glued carbon beamed rocketship. Mmmmm - wonder how I can make it stiffer!

Cheers

Feel, think, believe. Theories and anecdotes. That is all thats presented as proof that stiffer is always faster. Question this and closed minds blows their egos all over their keyboards.

A stiff boat feels different and more responsive. It feels easier to sail and it might so. Still no proof that it really is faster or easier to sail. Until proper two boat testing is done under different conditions we dont know ****. Flat earth society mindset lives on.

I`ve read all 7 pages..
I think Macca is trying to say that a stiffer platform is a good thing.
I think Wouter is trying to say that he`s right, but that no-one would double the cost of the boat to get a 2% gain.
I think they`re both right.
Doesn`t the F16 class rules stipulate the boat can`t be glued (ie must be take-apart-able for transport?) I think this sorts out the arms race a bit.

In the quest for ever-diminishing returns :
The Viper seems to have proved (by their results) that higher volume hulls (for 2-up sailing) is beneficial over smaller volume. Of course they must have put the volume in the right places as well.
Now they NEED bigger beams to stiffen a platform which has higher volume hulls, when compared to a boat with lower volume hulls.(This is independent of hull weight, since higher volume boats will be subjected to higher loads.) The bigger beams make the boat heavier once again. So the cycle repeats itself until the boat arrives at it`s weight (which in many folks opinion is way too heavy), but is still as fast as the lightest boats, meaning that the trade-offs seem to have worked slightly in their favour. (I say slightly as they have a highly developed rig and top sailors on their boats, which also gives them an edge).
This is EXACTLY what the F16 class rules are there for, and they seem to be working - Equalising boats that are built differently, but fitting into a boxrule.
If there were NO rules, Playstation would have won the F16 intergalactic champs, as they have taken the above to the other extreme. Bigger truck needs a bigger engine to make it go. Right, the engine is so big it made the truck heavier. "Frank, we need a bigger engine for the now heavier truck." Ok, but the truck will have to be bigger to take the new engine Oh wait...

Now for the case of ever INCREASING returns.
I have no doubt that Darren Bundock on a min. weight Viper would be faster than Darren Bundock on a standard Viper, and the min. weight Viper would cost a LOT more to produce. I won`t argue with Mr. Goodall on this since he seems to have built a boat or two.
If the hulls were built down to 15kg each, they would require a smaller set of (full-carbon) beams, so lighter hulls would require lighter beams, and the whole boat could be built to min. weight, or even 20kg lower, quite easily, if enough money were thrown at it. Min. weight mast with super-light sails that last a regatta or two will help.
Would this cost more than a standard F16 design ?
I think that`s what Macca and Tornado Alive have been trying to say all along. (But I`m not sure).

Excellent synopsis!

Summed up nicely in one post....... Who needed the 7 pages



This is the only part I disagree with.

Well done Steve, excellent sum up.

I would agree with TA, 2% of the population would pay the extra for the 2% gain.

No, we've established that increasing stiffness up to a certain point is better.

Note, that there is an important difference between both statements.

The first statement is open ended where the other is not.






Indeed and therefore the distance between the beams is factor here. In my models the largest component resisting the bows moving up and down independently is flexing of the beams in the up and down plane and not torsion. Torsion resistance is actually only a small component overall.

Therefore box-like (rectangular) beams with lots of material in the top and bottom sides is most efficient. However some shaping is needed on the front to allow for fairing of the beam into the hull. Waves hitting a beam with flat frontsides is not a good idea. Of course, flat backsides and top or bottom sides are desireable; that uses less material (weight savings) and makes it easier to fit blocks, dolphinstrikers and other stuff to the beam. Now look at the Falcon and Aussie Blade beams and you'll see these considerations being implemented. That is the reason why for example the trampoline track (the only things implemented for convenience) is situated in the upper backside corner. Here it allows for easy and clean tramp fitting but also adds the most to the stiffness of the platform. Designs with such tramp tracks halfway up the beam are simply not smart.

From memory those custom made F16 beams are equivalent in stiffness to 90x2 mm round beams but they are smaller and fitted with a more practical overall shape. The rectagular shape also looks the beams better in place in the beamlandings then a round beam that can more easily twist in its beam landings.

Wouter

Not when dealing with non-ideal springs that are submerged in fluids that act as dampers (the water surface or the rig flapping about). In such case the flow of leaked energy (grag) can be significantly greater.

In our case it is not just the spring itself (the beams etc) that we are concerned with. In our case these are attached to large surfaces that flap about in the water or air. Fit a spring to an object with a large surface area (and low weigt) and see whether you can still recover 99% of the stored energy while having it oscillate.

Other then that do this mind experiment.

Lets lay our boat motionless in the water. Then flex the platform, forcing one bow 40 mm down. Let go of the depressed bow and see whether the boats starts to move forward. I say that I see waves being created and the boat and rig shaking about but not much forward motion if indeed any. Now use the same amount of force (and travel) needed to flex the platform to push the boat forward. Spot the difference in the resulting motion ?

So our boats are not designs that recover much of the energy stored in flexing the platform at all.

Wouter

I don't know what kind of **** education you have over there but when I make mistakes students get electricuted, get seriously injured or loose an eye. Ever seen a hydraulic robot go beserk or see a see a steel support wire snap ? I promise you, you'll see people dive for cover and it'll make a big impression on everyone around.


In answer of your other points. I know of no F16 that comes anywhere near the (wall)flexing of the nacra 5.8 hulls. But if they do then that is just another (independed) drag component in the overall picture. At this time we were discussing platform stiffness (not wall stiffness of the hulls) as that is closely related to the choice of beams.

Wouter

Well Ace,

I remember the old geezers saying that a 16 foot High Performance boat would never work and that I was a fool to start such a class back in 2001. It could never be as fast as an F18, just couldn't be. You couldn't offer such a lightweight boat for less then a F18. It could never carry 2 males in a competitive sense. It couldn't ... ... ... etc

But we're here now and the old geezers are still on their fence.

The fruits of my labour are out there for all to see. Yours are, well, what are your achievements exactly ?

I often remember this qoute by Niels Bohr (co-founder of the quantum mechanics theory)

"If you think quantum theory isn't totally insane, then you haven't studied it properly yet."

Still, it is one of the most important theories in town; explaning everything from transistors to the way the universe behaves. Without it we wouldn't have our High Powered computers and mobile phones.

So please forgive me if I put you on the fence next to all the other old "good for nothing" geezers.

I hope your daughter has more brains then that.

Wouter

We know the answer to that question already.

No F16 can be lighter then 107 kg and a standard alu/glass 110 kg Falcon costs 16.000 bucks in the USA. With a 3800 buck carbon mast the boat will be at min. weight.

Now, Macca can build himself a 20 kg lighter F16 using whatever he wants and pay 100.000 bucks but then he can't race it in the F16 class. Not even when putting 20 kg of lead under his mainbeam, thus preventing him from using smaller beams or hulls as refered to in your example. Why ? Because he is only allowed a max of 7 kg of corrector weights and he still needs to design the boat to carry 107 kg + 145 kg of crew weight.

So what he can do is pay 100.000 bucks to basically make a boat that will be identical in specs to say a 19.800 US$ Falcon. Last time I checked, boats with identical specs were also of the same performance.

There is simply no way around that limit.

Wouter

You just don’t get it. Yes, both boats will be same weight and dimensions, but one would be a Glass boat with alloy beams and carbon mast, the other would be a full nomex/honeycomb boat with increased hull volume.
Catamaran designs lately are showing the larger hull volume boats (to a certain point) are proving quicker. A great deal of the reason why the Viper is competitive with boats much lighter boats is because of this and the increased platform stiffness.
If you think a 107kg all carbon /nomex Viper would not be quicker than the current Viper and other F16s, plus significantly more expensive, then you are delusional and this argument will just keep turning a full circle....... However, that is where I feel we are now.

[quote=ACE11I disagree on the amount of energy lost though when the platform twists and returns. Unlike the watch spring that return energy isn't applied to the original job - that is forward motion. I think a substantial amount of it is lost by the platform "wriggling" about in the water rather than applying it to smooth forward motion.
I'm over this now - off to sail on my glued carbon beamed rocketship. Mmmmm - wonder how I can make it stiffer!
[/quote]

A flexing body in a fluid can create propulsion, think of the wings of a bird or a fish swimming in water. I don't say you will recover all the energy. But if your foils are moving around, this is much more efficient as you might think.

The more I think about the stiffness subject, the more I see it is a not explored and understood subject.
Image I am sailing on one hull and a puff hits the boat. What happens. More lift from the sail, which will heel up the boat and create more leeway. The increased leeway increases the forces on the boards, which will heel up more the boat. As a result I open the sheet/change the course to reduce the heeling.
Now, I have a properly designed flexible board:
The puff hits the boat, more forces in the sail, more leeway, but now the board flexes in a c-shape. It produces less sideforce, hence lessheeling moment, but some lift. The lift pushs the hull a bit out of the water, which generates less drag.
Thus with a flexible board I could have less additional heeling moment and less drag, which might be faster...

You can only improve a design if you open your mindset and if you don't get blinded by simplistic and too early conclusions like "stiffer is faster"

Anyway enjoy your sailing on whatever stiff boat.

Cheers

Klaus

Well Wout

It's ACEII - Ace was my boat 30 years ago with many in between. I don't have much imagination with names.

I haven't criticised F16 or F18 in this thread or anywhere for that matter. In fact earlier in this thread I said "I love formula class sailing - that's why I've been sailing and building in it for over 30 years. I wish F16 every success."

Who are these old geezers still on the fence you speak of on this thread?
The debate on this thread has been about platform stiffness not the merits of particular classes of boat.

I have plenty of achievements, the most relevant to this topic being that I sail a lot. Around 100 races in the last 12 months - my wife would say more. I sail in the ultimate development cat class mainly. We are often doing boat on boat testing and always trying things looking for performance improvement. I feel qualified to express a view - take it or leave it.

Cheers

Steve, great summary of the debate.

I would add that the Pink Elephant in the room is the obvious but unstated realization that a One Up F16 and a Two Up F16 require different technical solutions. I think you were referring to this disconnect.


Obviously, the A class (1 up) and the F18 (2 up) are both 18 feet in length but the technical solutions are quite different (very crude comparison). This technical gap is much smaller at the 16 foot scale and one of the key insights of the founders as they looked at the marketability of the F16 concept.

The more important twin of the technical pink elephant that is not explored are the merits of a formula class that believes that fair racing between one up and two up teams is possible.

Assume perfect technical equivalence between a one up and two up F16 boats. Clone a sailor a couple of times and put them on the two boats. The single handed clone would have to magically come up with a lot more skill to get his boat around the course then his two clones on a two up F16 for the desired dead heat. It's damn hard to sail the one-up boat to it's number over the wind range and you have to really be at the top of the game to do this. (Some estimates of F16 1-up racers is that it takes 30% more skill to get back to your spot in the pecking order). Consequently, it would be better to race as two classes

Now you can acknowledge this disparity and deal with it, dismiss the disparity as "so be it", or not deal with it at all but this is simply politics. Without resolving the fundamental disconnects... the debate will continue.

I suspect that if you focused the debate on two up F16' class growth, the winning solutions will be clear. My solution... Follow Bundy and Caroljn.. F16 is a perfect solution for Light weight and mixed teams, Women teams and Youth teams! Hell... the Hobie 16 market was enormous world wide and you can't quibble with the experience of those two and other world class racers who want to develop this niche of the sport.

The single handers need a different solution for growing the single handed class....

Builders will offer their best equipment to meet the TWO needs as the TWO classes develop!

What a load of drivel!!!

That's a hell of a crystal ball you've got there Mark - you haven't even set foot on an F16 have you?

All you've done is made assumptions and drawn further assumptions based on those first assumptions.

No mate, YOU just don't get it.

There is no meaningfull difference in hull volume between the modern F16's and the Viper.

The F16's simply don't need hulls as big as say the nacra Infusion because they don't require anywhere near the displacement of those designs. The F16 hulls are 10% shorter in length and only need to carry 75% of the weight of a F18. Ergo F16's hulls are more narrow for the given length.

The Viper performance comes from the development of the rig and not because it is pushing fatter hulls through the waves. Last time I checked, fat hulls actually amount to more drag in such situations.

The stiffness argument is BS, If the standard F18's (Tiger, NF18) flex by as much as 95 mm in the test then there is no way that a large performance difference can be explained due to 10 mm difference in flexing between a Falcon/Stealth/Aussie Blade and the Viper with all of the latter below 30 mm flex anyway. Note that if the F16's had been of the F18 platform weights then they would only flex in the test to 60 mm or less, still 50% better then the F18's !

Last time I checked the Tiger crews were by far most often World Champions F18: Hell that fact could even be used to argue for reductions in stiffness !


I state and truly believe that a nomex/carbon/unobtainium/diamond inlays 100.000 bucks F16 with a few hookers as pit crew will be just as fast on the water as a 19.800 bucks race version of the Falcon/Stealth/Aussie Blade F16's or indeed any of the modern F18's

That is all the formula F16 class rule set has to do.



No Stephen, you have been beating this dead horse for 4 years now. I can't count how many times you've hinted that you would buy a F16 for yourself but eventually didn't.

Give it up mate, your are not going to impress your world view on the F16 class. So make a decision, get-with-the-program or get lost !

Wouter

Ace,

You are welcome to this forum and I have nothing personal against you.

However, anybody creating or maintaining any chaos on this forum with respect to the F16 class rules or imaginary killer boats will get a cold shoulder.

The time has come to permanently deal with these distractors.

It is up to you to decide on which side you are on; the way I treat you is directly linked to this choice.

Wouter

You got me there !

However, the F16 class only does this to be inclusive of all sailors and increase the fun. I don't think mixed racing is really in our future when we ever get to hard core racing. I expect we'll split in two seperate fleets at large important events when the numbers allow that. Of course while still using the same boat design (with sails cut for the different uses).

Right now we all seem to agree that the performance is close enough to make mixed racing fun for all, not because we believe the two versions are perfectly equal over the full range of conditions.

Wouter

Actually... sailed and raced the Bim 16 in the US, Spent a lot of time with Jim Boyer as this this thing was coming together and helped him rig his Taipan with the chute and did some playing on Lake Michigan with the two boats. There is a reason I have a long standing interest in the class but haven't bought in.

Not so fast! We haven't seen a "rock star" on an optimized Uni rig yet.

You're probably right, but I want to see more real world challenges before we p!ss on the fire and call in the dogs!

Oh my god, some really don't understand.
If you want to debate various aspects of boat stiffness, post in this thread.
If you want to have a personal pissing contest and you really have the need to do this in a sailing forum, go to the "ban Macca" threat (sorry Macca nothing against you, it is just that this threat is there right now). But you make yourself ridiculous.
If you want to continue telling why F16 fails, or what has to be changed, create your own class or at least your own forum "the better 16ft class" and post it there. If not you make yourself ridiculous.

Are you talking to me or Mark?

I'd be interested to hear how you would rig an optimized Uni.

Not to you. I used the quick replay button.
Though your question is worth it's on thread.

Cheers,

Klaus

Well, thanks Wouter, very kind of you. I have though only commented on the topic of this thread - relative stiffness of platforms. I don't wish to get involved in F16 class politics. As our US friends would say - I have no dog in that fight. I agree with Klaus's comment about keeping to the thread topic and cetainly enjoy the range of views there. A nice summary has been provided and it seems to have been done to death.
I'm not on any "sides" and have stated twice on this thread my strong support for formula racing. I have no issue or comment to make on F16 class rules.

One thing which occurs to me while reading this thread and some others is that perhaps not everyone in F16 has fully grasped the concept that it is a development class, and the implications which arise from that. While there are restrictions in some areas, there are many others for individuals and manufacturers to explore. This in my view is a wonderful attribute and ensures the class will remain fresh and close to state of the art. Otherwise you remain one design and miss out on exploring exciting developments over the years. The downside is that costs may increase from time to time.

Let's try "tolerance and understanding" of different viewpoints and get on with the sailing. May it include over-stiff, sloppy or just right platforms.

Cheers

See Wouter....It doesn't hurt to be nice.

4 years ago, I was an F18 sailor preparing for the 07 Worlds with no intentions of owning an F16. 2008, I finally sold my Capricorn sailing on OP boats whislt I get married and build a house. With as little as weeks left on the house, I will know how many $$$$ I will have in the kitty to buy another boat. I am looking at a 4.9 with kite, If I have a little more $$$$, then it will be a Viper. To be honest, if there is a few more extra $$$$ left over, then it will be an A Class, because that is where the larger fleets and more competitive racing lies, particularly in the state I live.



And this is where our view differs. I am sorry you believe this.

I, as one of the original "Gang of Three", that came up with the concept and started this class, can attest to Mark's racing on the BIM in Michigan when I brought up my 4.9 uni. In fact, that was the only time I had actually seen the boat and may have been the last time it was raced or heard from?

Kirt

I too confirm Marks claim to sailing the Bim.

We discussed it at length at the time, especially the differences between it and the Taipan.

Indeed, some F16 class rules were changed partly because of the input by Mark.

Wouter

so why is a F18 so stupidly heavy?

My 2cents...

Don't underestimate the gains to be achieved through stiffness! I think Wouter's earlier estimates of a minute over an hour are probably too conservative by far!

My reasoning: On my windsurfer, I have two 30cm fins which are almost identical in chord, profile and plan, but one is noticeably stiffer (I can feel it flex maybe 5mm when I push with all my strength, whilst the other feels like a brick!). That might not seem much, but it's enough to get me planing in almost 3 knots of wind speed earlier (11 as opposed to 14 knots) OR get me going in 15 knots with a sail that is almost 1 sqm smaller (6.0sqm vs 6.9sqm).

That is a HUGE difference from one small fin. These results are consistent over the 4 years I had both fins, always using the same anemometer and board. Sure, fins aren't the same as hulls/platform, but you get my point.

Sorry don't get your point at all, foils and stiffness of foils is a completely different issue than what we are speaking about.

no its not, it has everything to do with how the boat as a whole deals with forces.

If a platform flexes or a foil flexes, you are not utilising the energy as efficiently as a very stiff platform or foil.

Not only that but in the case of the foil on a windsurfer, you are losing your latteral resistance with every 'flex'. That's the reason the Hobie guys started buying the stiff EVO rudders.

Maybe I'm way off the mark, but my point was, don't underestimate the gains achievable though stiffening. Around 5mm of flex in a 30cm fin (~1.5%) when I was trying as hard as I could is still pretty stiff, but going to a rock hard fin still made a big difference.

An interesting read about developments in the A class fleet with reference to the DNA.

http://forums.sailinganarchy.com/index.php?showtopic=108776&st=50

Adjustable angle off attack on the boards, how cool is that?

YES - 1 more thing to have set wrong on your boat

Good to experiment with though, particularly if you are not sure if they are at the right angle of attack for the conditions. Fixed cases = 1 option.

Pops up every couple of year, never breaks through.
How is a person called who doesn't learn form mistakes in the past?

Persistent.

Depends if you ever figure it out. Thomas Edison failed at making the lightbulb, (I think), over 1000 times.

Ok but Edison was looking for the bigger picture. He wanted to make electrical light and was looking for the technical solution. The reason why adjustable boards fail, is because people just look to make things different or adjustable boards for the reason of adjustable boards. If you look how to make your boat faster you will come up with good ideas.
By the way there is still a huge potential in board design, if I look at the current "state of the art" at beach cats...

Cheers,

Klaus