How important is relative boat weight?

Having been in one-design classes where boat weight difference can be up to 30+ pounds, I am wondering how important this is to people.

Also, something I have observed is that as fiberglass boats get older, they tend to get heavier (from absorbing water). And their original sails seem to get fuller (blown out). That combination seems to work well -- heavier boat, fuller sails.

But then the sailor decides he wants to get new sails. The new sails are flatter and sleeker, but they don't have the power needed to propel the heavier boat.

What do you think about all this? Especially, whether you think it is a big deal if your boat is heavier than somebody else's boat in the same one-design class -- or formula class, for that matter.

I think you have a couple of issues to deal with on this question. Construction methods have changed a bit and now "newer" boats don't gain weight as badly as the older boats. The reason being is the core or lack of core. A H14/16/18 has a foam core that absorbs water and that's where the weight comes in. H20's, I20's, 6.0's and most the other newer designs don't have cored hulls and don't absorb as much water. I can say that my old H20 was still under class weight even as a 10 year old boat.

The issue with those boats becomes stiffness and that can make a difference.

To those that care enough to change hardware to remove weight, yes it matters and is important. Relative speed difference? Typically it's a game of inches out front but good sailing will overcome 5-10 lbs or more of boat weight.

Hi Mary,

good idea to bring this topic to the general forum.

The impact of weight on performance is much smaller than many people think. Why? The first reason is, because heavy weight hurts only in light winds. As soon as you have to de-power the sails, the extra weight gives you more righting moment and you can use more pressure in the sails and hence you are faster (up wind). Down wind you are slighly slower in any wind conditions. But you win a race on the up wind leg anyway. (okay I have to say: I assume that the weight difference is in the hulls, not in the rig).
The second reason: If your 150kg boat is 5% over weight, then your total weight (assuming 150kg crew) is just 2.5% over weight. Somebody may play with texel or schrs calculators to find out, how many percent performance are equal to 2.5% more total weight. I guess below 1%. How big is the skill difference between sailors? Something over 10%, I guess.

Common understanding says heavy weights win in strong winds and light weights win in light winds. At least that is my experience in any sailing boat.

Another common understanding is: The reason why we lose races is because our boat is too heavy. The reason why we win is because of our skill of course. That's the reason why some people concentrate so much on weight. <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

As long as you don't sail races only at light winds I would not care about these weight differences.


The impact of weight on boat handling at the beach however is another story. On our beach with soft sand and steep slope, we removed even the rudders of our Dart (which is only 140kg). Maybe we are too weak...
Last comment on weight: Every kilogram you can save in the rig is worth doing it, because it helps to righten the boat after capsizing.

About the new and sleeker sails, I don't know... I think that even a new sail has more camber than required. You have to pull it flat anyway. I have never had the problem of a too flat sail, but I know only a few boats of course.

Cheers,

Klaus

On the contrary, most modern boats do have cored hulls. And yes, all polyester/epoxy materials absorb water (they are hygroscopic) and gain weight. The boat doesn't even need to be in the water to gain weight...moisture is drawn out of the air and over time, it adds up (increase is something like 1-3% of the weight of the resin). Only way to really combat this is to put in the boat in an arid climate for weeks/months to dry out.

yeah but they're not the soft open cell foam of yesteryear and that was my point. the new materials are not as bad as the old ones.

Are you kidding? Boat weight makes a HUGE performance difference! (in your head)

[/quote]Are you kidding? Boat weight makes a HUGE performance difference! (in your head) [/quote]

That must be why Nigel/Alex beat us a Spring Fever our boat was 6pounds heavy and also my winter fat. I need to put myself and boat on a diet if I am ever going to have a chance of winning.

I guess the reason we came in 6th was that we had the next to heaviest boat at 409 lbs.. What's the best way to lose 10 lbs with your boat.

Sawsall.

Don't forget that each extra lb. of weight in the boat/crew is another lb. of water that water that has to be moved out of the way for each boat length travelled, plus additional skin friction/drag. Also within the same hull design a lighter displacement boat will generally turn more easily. The heavier boat/crews have to generate more power from the rig and have higher sheet loads.

Cheshirecatman

We race one of, if not, the heaviest boat in our class. The difference in weights, from lightest to heaviest, is minor (3.5%). Our crew weight is 20 to 30 pounds over minimum. We've had our best finishes in less than 10 knots of wind. This boat seems to be very negligable of crew weight. For us (weekend warriors) no big deal.

Relative boat weight? None of my relatives own catamarans so I guess I am OK. <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />

In my experience, boat/crew weight doesn't hurt performance in the light stuff and heavy stuff. Heavy weight hurts you worse in the medium conditions, where lighter crews can begin to fly a hull easier and earlier while you're still trying to power up.

Weight is major and to state otherwise is deluding yourself.

Mary, your assumption that the old sails better suit the old boat also has issues but lets keep it to one argument at a time.

A couple of case studies.

2 boats get perfect starts on a perfectly laid line. Assuming both boats are travelling at the same slowish speed when they cross the line the boat that gets to full speed first will have a definite advantage. If its the windward boat it will overhaul and then gas the leeward. If its the leeward boat its foils will generate more lift sooner (due to its increased speed) and it will pull ahead and then lee bow the windward boat. Either way the light boat wins.

You go around the top mark a boat length apart. If the lead boat is lighter it will accelerate away and the aft boat won't get a chance to attack. If the aft boat is lighter it will make up ground on the maneuver and be sitting in an attacking position when the two boats reach full speed.

If you do some quick back of an envelope calcs you'll see that without even considering the added drag while at speed at boat+crew that is 10% heavier will loose about 1/2 a boat length on every maneuver.

I didn't say weight didn't matter, or wasn't "major". My statement was that in light air weight doesn't hurt as much as people think. I'll stand by that. I said extra weight hurts more in medium conditions, and I'll stand by that as well. I don't believe extra weight is automatically helpful in heavy air, but that's more boat dependent. So we're almost in agreement.

I'll say that every Hobie I've sailed/raced (14, 18, 20) wanted lighter crew (and boat) even in heavy conditions to sail better. The only time that being heavy didn't hurt was in light air.

The Nacras I've sailed and raced (5.8, 6.0, 20) haven't minded the extra weight as much in heavy conditions, in some cases it's helpful. But again, where it hurts most is in medium conditions, not the light stuff.

In light air so many other things matter. And, for almost everytime I've seen a lighter boat/crew out accelerate me as a heavier crew/boat I've coasted through the next lull as they slowed earlier. Actually keeping boats moving though maneuvers is key, and reduces the acceleration difference coming out - most people don't do it well in light air. If you're smooth a heavier boat can keep momentum better through a light air tack or jibe.

That's been my experience, spoken as somebody who has sailed ~400lbs of crew weight on a regular basis. If that makes me deluded than so be it!

Here's my reason to lose a few pounds.

From the F16 Forum

If weight was not an issue, then why do (most) manufactures strive to reach min weight and why do you see all the top sailors working very hard at reducing overall boat weight as much as they can espesially aloft. The serious sailors will even seek out removing grams from their boat.

Are they wrong, wasting their time or do they know something some others don't.

Just for arguments sake....

The quote above references 2 crew weights, which (to me) may mean two dfferent crew members. Could the performance difference you experience be related to having different crew onboard? Certainly crew work would reflect on your ability to get around the course/manuever/etc.

Just asking, as your assertation seems to be fairly general and COULD be misleading to the exact cause of the decreased performance.

No disrespect to the crews involved, of course.

EDIT: BTW I try to keep my boat down to minimum. I think it is challenging and it gives a mental edge. I just wanted to point out that there MAY be an issue with the general logic of the above-mentioned quote. End Lawyer-speak.

Sorry mate,

I wasn't addressing you in particluar, your's just happened to be the last post.

ive built a few solo ocean race boats in my time. the current thinking is that every extra kilo is worth about 4 hours on a rtw race.

There is a very good statistical analysis on the web:
http://www.geocities.com/f16hpclass/F16HP_optimal_crew_weight_analysis.html
I recommend to completly read it, because the author actually made two analyses. One simple normalised time to finish over weight (light boats are better even in strong winds). In a second attempt he realised, that the good sailors have in general lighter boats. He compared than the relative performance of each boat in different wind conditions and found that light crews/boats perform better in light wind and heavy crews/boats better in strong winds.

Another proof is, that top sailors are in general not lighter than average and that female crews (which are lighter in average) are not the faster sailor in average.

If you can't use the benefit of a heavy crew in strong wind, than maybe because you don't have the right heavy weight trim for your boat.

Cheers,

Klaus

Basic marketing: If you want to sell a boat, you have to satisfy the wishes of the customers. There are also golf clubs out of CFRP and titanium and cars with four wheel drive which will never be driven outside of big cities, and so on. What counts is that they sell.

Every kilogram of resin, fibres or whatever is your boat from costs the builder something. Hence there is no interest in building heavy boats. BTW: manufacture costs and selling price are not the same.

Of course if somebody is convinced by the weight issue, his mind will be blocked until he get rid of the last gramm. As a marketing guy I would put even more fuel in this fire and offer extra sets of CFRP rudders and boards, dyneema sheets and so on.

Don't understand me wrong, I am very happy, that there are lightweight boats, because you can handle them so easy on the beach. But I concentrate on sailing and not on material.

Cheers,

Klaus

A heavier boat may in some conditions generate a higher righting moment however it is the ratio of righting moment to weight that drives performance. If Klaus is right I should be adding weight to my boat on heavy air days. I've never seen anyone do that.

A heavier boat only adds half of the extra weight to the righting moment, and multiplied only by the width of the boat: say 10 kgs of extra boat weight give 5kgs*2.5m=12.5 Kgm of righting moment; 10 kg of extra crew weight add 10kg*3.4m=34 kgm, practically the double of righting moment; boat of 2,5m width and crew of 1,8m assumed. This is why extra boat weigth is much more important than extra crew weight. Downwind it gives more or less the same disadvantage, at least for cats that go on two hulls downwind.

From my personal experience I we have found that older sails don't pay on a older boats in all but very light wind conditions. We gained a lot when we got new sails on our 1991 H16.

F=m*a...

This has been experienced over many different crews, all very good sailors.

With my crew I sailed with for 7 years, we steped onto the Capricorn at 186 kg, and by the time the AUS Worlds came about, we were 164kg. We could feel the difference in the boat as we became lighter. Just after the Worlds, I had several different crews jump on ranging from 85kg to 65kg. VMG was better as the crews got lighter.

Exactly. It is quite obvious that the weight should be added to the crew and not the hull.
Also, bigger boats should increase the water ballast in the back of the windward hull.

Thanks for the reply, it certaily makes sense to me. 18 kgs seems significant.

One more question.... let's use 10 kgs wieght difference in this example. What order would you place the following (from most important to least important - obvioulsy all would help)?

1. New set of sails
2. Completely faired hulls, rudders, boards
3. Get boat/crew to minimum weights (10kgs)
4. Extra 5 hours practice each month

What else should be added to the list?

Thanks for the input.

4
1
2
3

Time on the boat is always the key. 5 hours extra is not a lot but it helps. I would rather spend more time on the water than working on the boat to get it completely fair, to min. weight etc. etc.

Actually we do this on landyachts and several larger racing Cats and Tris have waterballast in this way.

It is being done; you were just never around to see it. <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Wouter

"the only place where weight improves performance is in a steam roller" ... Uffa Fox <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

water ballast is very different from static weight.

5. get the sail and rig trimmed
6. having a positive attitude
and I would split 2) in
2a. faired rudders, boards
2b. faired hulls *)

My ranking is:
6
4
5
nothing
1
nothing
nothing
2a
nothing
2b

*) long bodies are less sensitive to roughness than short bodies (i.e. rudders and boards) due to Reynolds number effects.

Cheers,

Klaus

4
1
3
2

Water ballast in the transom.... Or what the big Multi sailors like to call them, the 'Oh [censored] Tanks'.

If they had a choice, they would prefer to run without them but are necessary for saftey

Apparently Uffa Fox (designer of the laser dinghy) didn't look around too much.

Many racing mono's have waterballast (Volvo ocean, Classe Mini (the open fleet), large cats and tri like Orange). Many competition landyachters put (bags of) sand in their **** during days with strong winds and competition glider planes use a significant amount of waterballast to improve both airspeed and distance covered before having to find another thermal to regain altitude for the next leg.

Of course keel boats need weight on the end of their "fin" to even be able to make forward progress and sailing ships or a past era (galjons and clippers) used massive rock or brick ballast placed inside the hull on the keelline to stablize the boat, they would capize otherwise. Actually these bricks would be transported in the otherwise empty ship to the colonies where part of it was unloaded and used to build the settler towns. This was possible as the return cargo of species and other goods would make up for the reduction in this ballast.

I guess the designers of all these championship craft are just misguided.




But they don't have that choice as the alternative is to cut down on the saildrive and that loses more performance. Therefor it is not only a matter of safety, it is a matter of performance where they are unwilling to solve the issue by powering down the rig (loose performance)

Wouter

Well put Jimmi.
<img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />

C'mon Wout, that's not fair! The man was brilliant.

http://www.uffafox.com/uffabiog.htm

btw- I can't find any mention of his having designed the Laser. I'm not saying he didn't! Just can't find a citation.

There are alot of misconceptions associated with boat weight, some falsehoods even.





First of all, the same water that is pushed out of the water pushes back against the hull on the rear part of the hull and thus negates a very large portion of the "push-away" drag on the front part. The form drag is actually ONLY the net difference between the "push-away" and "push-back" phenomenon and in a frictionless fluid this net difference would be zero, resulting in zero drag. In real life fluids like water are not frictionless and the amount of internal friction forces for a given fluid determines the amount of form drag. That is why the same hull in water has less form drag then say in oil.

Therefor the popular representation ;"each extra lb. of weight in the boat/crew is another lb. of water that water that has to be moved out of the way for each boat length travelled" is misleading as it omits the part where the same additional lbs pushed back later and gives back some of the energy lost on the front part of the hull.

Secondly for some factor to be very important for the overall performance of a sailcraft it needs to constitude a significant part over the overall drag. If a given component only makes up 10% of the total drag then a 25% reduction of that factor only amounts to 2.5% drag reduction of the total with an even less performance gain (= for floating objects typically (1-1.5%)

The team for the C-class catamara Miss Nylex publized some of their research data and I give some of their conclusions regarding drag factors.


Hull drag (subtotal = 35%)

-1- wave/form drag = 15%
-2- skin friction drag = 20%

Sail drag (subtotal = 25%)

-1- form drag = 9%
-2- induced drag= 16 %

Centreboards = 20%

parasitic drag (group of 7 subcomponents like rigging and crew each less the 4%) = 20%


Note that even form and skin drag combined only make up for 35% of the total drag on a C-class catamaran with a highly efficient wingsail. On our catamarans the rig is less efficient and the sail associated drags will increase reducing the relative magnitudes of the hull form and skin drag factors.

35% may sound like a large portion but we still haven't completed the analysis yet. 1% additional weight doesn't increase the hull related drag by 1% of 35% = 0.35%, it is less. This is because of the non-linear dependence of volume (weight) and surface area upon size. We all know this to be true as a bottle that is twice as large will have 4 times the surface area and 8 time the enclosed volume (weight).

Assuming the hull can be optimized for a given boatweight and crewweight then for each 1% of additional weight you only have to entlarge the hull by 0.33% resulting in similar fractions (0.66%) of increased hull area and crossectional area. Also the fractions became smaller within increased additional weights, again due to the non-linear behaviour.

Basically (a simple example) an additional kg on a 100 kg boat + 75 kg crew (0.57% weight increase) results in a hull drag reduction from 35.00% to 34.86%. Which on the total drag of a sailcraft like Miss Nylex results in a less then 0.140% reduction => ... => on average 0.1% performance increase for a waterborne craft (= about 3 second per hour racing). Of course this is for lightweight boat with a singlehanding crew with everything else like sailcut and windconditions being perfectly equal. When looking at doublehanded crews on heavy boats the difference becomes MUCH smaller as 1 kg difference here will be a much smaller fraction of the total. In effect the solo sailor on a lightweight singlehander is the worst case scenario. However, allowing different sailcuts (formula classes instead of One-design) is so potent that it is able to complete ofset this weight dependancy, as proven over and over again in the A-cat class where 85kg skippers are competitive with 65 kg skippers on a world championship level. That is how small the dependence of weight in the larger picture can be and why OD garanteed equality in performance is such a myth. In several cases the OD character of a class makes the differences in performance worse !

We should now do the analyis on 1% difference in sailarea and see the difference between that and the dependency on weight. That tells an interesting story as well and why water or sand ballast can be an advantage on sailboats and landyachts.

Wouter

Do you want to just check up on Uffa Fox and correct comments?
Uffa Fox did wonders for the development of lightweight planing dinghies. I dont think Bruce Kirby will be too pleased about about the laser comment either.

I haven't looked it up but I may well be wrong about Uffa Fox having designed the laser.

The rest of my posts still stands however.

Wouter

Bruce Kirby designed the Laser.

Wouter,

Its a lot simpler than that buddy. You can have as little or as much friction as you want. It doesn't really matter. Is all about the sum of the forces (F) which includes your very impressive friction component.

So i F equals 1 newton just for aguments sake. Then that will acclerate 1 kg at 1 m/ssq. The more mass an object has the slower it accelerates. Simple physics. Forget your crazy friction analysis it doesn't mean [censored] in the end.

So if your boat is heavier. Your going to have to come up with that extra power to keep up with the lighter boat coming off the start line and in general manouvers around the race course. Thats how real life works Wouter. We dont race in straight lines in some dutch test tank.

Sue

I was sailing on a really narly day in Newport, it was the day that one of the 40ft racing tri's went head over.

We stuffed it going up wind and my crew stuck the trap ring thru the hull getting the boat back up.

Upwind on the tack with the hull with the hull full of water was unbelieveable. The boat was fast and flat in 30knots, with bigger puffs, Luckily we sailed back on a tack with the holed hull in the air, but the hole was forward, and we kept the bow up, and the hole out of the water, so the water that was in the hull stayed in the hull. Back at the ramp we discovered that the hull was almost FULL of water. Unbelieveable, I cant believe we didnt lose the shrouds with that much weight.


I've always thought we could/should have a way to suck up water on the tack and use that as ballast in the windward hull.


Bill

Sue,

Are you explaining junior grade secondairy education physics to me and then misapplying it ?

You really have no idea of what I do in my professional life do you ?



of which the drag forces are an very important part as the accelleration is only the result of the net difference between drag forces and drive forces. When both are equal and opposite to eachother the boat stops accellerating and had achieves max sustained speed (=topspeed).

Newtons second law of motion is therefor not a factor with respect to sustained straight line speed (=topspeed) which is what racing catamarans spend by far most of their time doing.

Of course, in reverse, a heavier boat decellerates (slows down) less then a lighter boat in the lulls and when encountering waves. A light boat may win at the start-line but will loose in the lulls by the same token.

You cherry pick concepts and then simply ignore the reverse effects to argue your case. A failing grade skill level even for a junior secondairy level pupil/student.

Wouter

I would like to know what Sue is doing in her professional life though.
It is well known to the regulars here what Wouter do <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Basically the loss of performance due to increased weight was more then offset by the increase in performance due to ability to hold down a more powered up rig. According to Uffa this is comparable to sailing a steamroller.

I rest my case.

Wouter

Sue,

Life is not as simple as you say. But okay, I will use your simple formula f=m*a.
If your boat accelerates slower because it is neavier, then it deaccelerates also slower.
Let us assume, both boats (one is 10% heavier) sail with 17kts. Both boats are hit by a wave (or a lull or make a manoeuvre or whatever) at the same time.
The speed of the normal boat slows down to 15kts. (17kts - 2kts/s * 1s)
The heavier boat slows only down to 15.2kts, right? (17kts-0.9 * 2kts/s * 1s)
Now the boats accelerate again.
After one second the normal boat reaches again 17 kts. (15kts + 2kts/s * 1s)
The heavier boat accelerates slower, but because it has only lost 10% less speed, both boats reaches at the same time the speed of 17kts. (15.2kts + 0.9 * 2kts/s * 1s)
During all this time, the heavier boat had have an equal or a higher speed than the lighter one, and hence traveled a longer distance.
It is logic that a boat has to accelerate after each de-accelertaion. Hence from start to finish we have n de-accelertions and n+1 (the +1 is at the start of the race) accelerations. So the hevaier boat makes n times something good and looses only one time something.

Of course life is not only F=m*a, the hydro- and aerodynamic characteristics cannot be neglected. But even in your simple model, a heavier boat is faster.


Not only to Sue:

So far, it is an interesting discussion with good arguments from all participants. Let us discuss in civilised way, without insulting each other please.

Cheers,

Klaus

I think you will find that Bruce Kirby was the designer of the Laser.... But I might be wrong.... I have been known to spread crazy talk in the past <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

The designers of the above craft were not misguided, they just had an understanding of how sail boats work... unlike some on this forum...

I will attempt to explain but dont freak out if you get lost along the way, its complex and involves thought <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

on a Displacement boat (not a performance catamaran/multihull as the displacement rules dont fully apply to such a craft) once you reach hull speed then weight is good. it helps stabilise the boat and allows you to carry more power. it also helps with keeping speed during direction changes such as tacking. more momentum into a tack equals more speed on the way out.

in the AC boats they have huge water bladders to fill with ater once the wind speed is such that the boat will be travelling at hull speed upwind. On the Farr 40's we put as much water as allowed in the bilge if the wind is strong enoug for us to reach our max VMG upwind.

Here, I have a simple way to look at this and exclude the discussions about physics, fluid dynamics etc.

Look at the US Sailing Portsmouth numbers and compare these three boats; M20, CFR20 and I20. They have different rigs (uni vs. sloop) but carry similar sail areas both upwind and down wind (I know the M20 is 1' wider but it's still a good reference point). I probably should have pulled the Texel numbers and compared the I20 to the Eagle 20 Carbon but.... I did this....

Key
Boat - weight, SA up x SA Down, Portsmouth numbers

M20 - ~255lbs, 24m^2 x 25m^2, 58.0 61.0 59.0 57.5 55.0
CFR - ~265lbs, 24m^2 x 25m^2, 58.0 61.5 58.2 58.1 57.3
I20 - ~390lbs, 24.25m^2 x 24m^2, 59.3 62.0 60.2 58.5 57.5

Notice that in light/med conditions the light boats are rated faster. As wind speed goes up the gap closes for the I20 and the CFR but not the M20 (the beam starts paying off).

I think the conclusion should be obvious. Lighter is faster. (don't rake me over the coals a/b the sloop vs. uni, I know I know....)

One more anecdotal account. I have sailed with some upper upper level sailors. If weight didn't matter, I don't think they would be so anal about using small light lines and keeping the garbage off the boat.

well... yanno..
Uffa Fox was as instrumental as Bethwaite Snr, Charles Sparrow, John Spenser, Ben Lexcen and Richard Court in the development of high speed sailing. Debate all you want but I am confident the marine architects will back my statement.

Uffa if I recall basically made the International Canoe class the speed machine it is.. He was the father of the modern planing dinghy with his International 14 "Avenger". Her record stands today winning almost all the races in the first year she entered. Only Darkie is in her class as a 14teen legend. He was involved in developing the trapeze..

Maybe if land yachts used a trapeze they wouldn't need the sand ballast.

Im not an engineer.. I only vaguely recall my sckoolin but isnt there a formula that equates force is equal to mass times acceleration? So for a given force the greater the mass the less the acceleration..
<img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />

From http://stanschreyer.com/?cat=7

"Of course, the C-Class is now most widely known because of the wing sails which all boats use. The first wing sail appeared at a C-Class championship in 1974 on Miss Nylex, and it was made of spruce and balsa. Miss Nylex won the title that year, but was defeated by a soft sail boat (Aquarius V) the following year, mostly because Aquarius V was lighter."

So the less efficient rig with greater drag from the rig beats the more efficient boat with no hull drag penalty and weight has nothing to do with it! Or maybe they weren't sailing in a tank and had a non- uniform wave pattern. Maybe like me when I go sailing I cannot optimise my hull shape for different crew weights. I have to cope with the non-optimised increase in drag. At a 10 knot average your 1kg example still gives a significant boatlength difference. let alone the opportunity for position on the water. I am sure that most sailors would not quibble about your 1kg difference but 10, 15 or even 20kg! I do however find that when I have a lighter crew/boat combination I power up earlier and once overpowered I can use rig control to reduce power and drag from the rig.

Your posts are very interesting, Wouter. Could you send me a pm where you do a complete analysis of the drag forces and the driving forces acting on a cat moving through the water? thanks!

One important point to keep in mind is that weight can not be considered by itself. You have to consider the power to weight ratio. Look at two of the fastest sailing craft in the world- Yellow Pages and the windsurfers. One weighs about 350lb and the other weights about 30. Both have achieved virtually the same speed while the first being about 10 times heavier than second. It's all about power-to-weight.

This is why having a heavy boat is generally not beneficial, because the added weight contributes mostly to drag and little to righting moment (which equals power). However having a heavier crew (movable weight) contributes to more power generated from the rig (as long as the wind is strong enough to support the fully hiked crew).

sm

No doubt that the power to weight ratio is important, but comparing beach cats to a windsurfer or yellow pages to me seems wrong. Yellowpages travels at nearly 50 knots, and as the wind-drag goes by the velocity squared, the wind-drag is by far the biggest drag component in those speeds. At 15-20 knots however, I think the picture is rather different.

Air and water are both fluids, so the hull drag goes up with respect to velocity squared as well. That's why planing and hydrofoiling craft are able to get up to these high speeds- they reduce surface area as their speed increases. So in this case, a catamaran does not act the same way as a planing craft because it's surface area does not decrease with increased speed.

My point however was that you can't look at weight alone because here we have two craft (YPE and windsurfer) that are able to travel at roughly the same speed yet one weighs about 10 times as much as the other. We could throw Hydroptere into the equasion and probably have another boat that weighs about 10 times what YPE weighs.

The critical issue (and one that effects catamarans as well as any other sailboat) is that the total weight essentially contributes to both drag and power. The trick is to maximise the power-to-weight(drag) ratio something that YPE and windsurfers have done quite well. This means having minimum boat weight, but not necessarily minimum overall weight.

sm

Sorry, insufficient spare time.

Besides I've typed up large sections of it already on this forum in the past; maybe do a search ?

Also writing out a COMPLETE analysis of drag and drive forces is a major project in itself.

Wouter

Finally some persons who are using their brains !

You guys are spot on, Smiths_cat and SRM !


And both of you give perfect example of where an overly simplified rule of thumb like "less weight is always better" falls flat.

Wouter

Interesting thought here. When the 18HT was used in the Tybee5 a huge complaint about the boat was that it didn't have the momentum to have much punching power. It just sat and bobbed back and forth.... in that cast it was a boat that was too light. The 20' light boats don't seem to have that problem, I suspect it's b/c of the longer waterlines.

You are right of course (take de Morrison's equation on forces on cylindricals for instance, the same is the case there for the "drag-part" of the equation). What I was thinking is that on these wessels, the wetted surface is relatively small compared to the sail area/area causing wind drag. Hence, the wind drag should be the biggest drag factor..?

Racing catamarans may spend most of their time at sustained speed. But any good cat racer knows that its Blasting off the startline and smooth tacks and bouy roundings are where most of the ground is made in a steady breeze. Accelertion to top speed is essential for this.

I know what you do for a living, you've told everyone it seems. I just believe you are grossly over complicating the argument. Im suggesting that you should go back to the basics to get a better understanding of whats going on.

I try not to spend too much time decelerating when racing so i dont need a heavy boat.

Sue

Are you explaining junior grade secondairy education physics to me and then misapplying it ?

You really have no idea of what I do in my professional life do you ?



of which the drag forces are an very important part as the accelleration is only the result of the net difference between drag forces and drive forces. When both are equal and opposite to eachother the boat stops accellerating and had achieves max sustained speed (=topspeed).

Newtons second law of motion is therefor not a factor with respect to sustained straight line speed (=topspeed) which is what racing catamarans spend by far most of their time doing.

Of course, in reverse, a heavier boat decellerates (slows down) less then a lighter boat in the lulls and when encountering waves. A light boat may win at the start-line but will loose in the lulls by the same token.

You cherry pick concepts and then simply ignore the reverse effects to argue your case. A failing grade skill level even for a junior secondairy level pupil/student.

Wouter [/quote]

It is not so much a factor of being lightweight but more of being insufficiently damped.

It is the same with a car that has worn down dampers in its shock absorbers; it is very difficult to keep that car on the road in corners or uneven roads as well for exactly the same reason.

A long hull will introduce disproportionately more damping then the increase in mass-a-top and sailarea. All these dependencies are highly no-linear and that is why so many people become confused when the only look at the specs of boats and not model the behaviour mathematically.

Wouter

In the context of beach catamaran's (and high performance dinghies) which is what I beleive this thread is all about, Uffa Fox's comments still hold true, a lighter boat is always better than a heavier one.

Of course that does not mean that you can't design a lighter boat that is slower than a heavier boat, and you will be able to find examples where this does not hold true, but that is only because the lighter boat was not properly optimised.

Gareth

>>>Hence, the wind drag should be the biggest drag factor..?

I can't comment on the relative proportions of all the drag components, but consider that if you take a high performance rig and stick it on an ice boat it is capable of going 4 or 5 times faster than on a beach catamaran. To me, that's convincing evidence that the hull drag is still the highest contributor to overall drag.

sm

You can have a light boat, even one built without exotics. But it won't be as strong or as stiff as one thats built with high modulus materials.

I mention this here because I have been banned from the F16 Forum and there was an active discussion happening there until the moderators decided that it wasn't in the class' best interests.

no prizes for guessing what this boat is <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Another pic of a lightweight boat...

Macca,



You have not been banned ! (yet !)

It is only that your posts concerning F16 class rules and F16 boat weight are being locked down or deleted as you refuse to adhere to official F16 class procedures regarding rule changes and common respect for factual discussions. Many times over you have been both invited to submit official proposals for processing and warned of the next steps in the disciplinary path when continuing to grandstand.

Stop playing the victom !

Wouter

Macca makes a good point, when I said a light boat is better than a heavy one, I meant in terms of performance only, if you can't finish the race then you have gone too light <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

I should have said a lighter boat is always quicker than a heavier one all other things being equal, but not necassarily better.

Gareth

That kind of cracking does not just happen on lightweight boats. That same kind of vertical hull crack, aft of the front beam, happened to us on a Hobie 18. I, as crew, was out on the trapeze, and it was maybe a couple of minutes after the start of the race when all of a sudden the hull just started to split open right in front of my forward foot. Very unusual location for a crack like that.

We managed to get the boat to the beach on the same starboard tack, keeping the starboard hull as far out of the water as possible. (Still got full of water, though.)

Mary,

Did you ever find out what caused the failure?

Such a crack will happen on any catamaran irrespectibally whether it is a 180 kg F18, 75 kg A-cat or a 18 ton Groupama 3 when an internal element like a bulkhead or subdeck comes undone or cracks due to production errors and no longer supports the hull skin.

As a result such damage has happened to pretty much any design out there in the world today and will continue to happen in the future. Boat builders are still not applying aeronautical or space-age quality control systems; as such these incidental mishaps are recurring.

More importantly is whether the company building/selling the boat takes responsibility and handles the warrantee in a proper way. That has always happened thus far.

Wouter

Mary's right - I have seen a very similar-looking issue on other "heavy" boats. Showed up on my old Mystere 4.3, which could never be confused with a high-tech lightweight boat. Not nearly a fatal issue, either - it was a straightforward repair and was completely invisible when complete. I sailed the boat for another two or three seasons without recurrence.

In the right hands, boat repair is not a death knell for racing boats - I think too many boats are "totaled out" after collisions and failures. Effective repair doesn't necessarily mean significant weight added.

I've read this thread and it's esoteric theory, anecdotal evidence, suppositions, etc. Simply proof to me that too much time is spent on worrying about reasons for a poor showing. There was a glimmer of light when people started ranking time on the boat above other issues, but then the wheels came off again. Full-circle, we're back to F16 sniping? *yawn*

Thanks for the numbers, that brings some light in the discussion. I don't worry about cat/sloop. Also the quality of Portsmouth numbers may be debated, but for our discussion it is fine.
In light winds, where we all agree that lighter is faster, 125lb heavier is just a 2.2% penalty. So 12.5lb weight increase is 0.2% penalty. That is just nothing, at least for me.
Maybe you talk with your upper skill sailor friends about this 125lb = 2.2% slower relation. Could get another anecdote.
What is the beam and mast height of a CFR20?

Cheers,

Klaus

Sue,


It must be very calm with no waves, that you can maintain a constant boat speed (and ones again, I agree, that in light wind the lighter boat is faster). I have attached a speed vs time gps track. Medium off-shore winds, waves 0.5m, Dart 18, data points are spaced every 15s. You can see the tacks as deep low speed points. But between these points there is not really a constant speed. Well, maybe I am a bad sailor... <img src="http://www.catsailor.com/forums/images/graemlins/frown.gif" alt="" /> then again I spend better my time in sailing the reducing the weight.

No, I don't, I think about about acceleration and de-acceleration, about light and strong wind, about steady movement and dynamic movement, so please don't blame me.

Cheers,

Klaus

The CFR currently has a beam of 8.5' and the same mast/main sail as the M20.

I have yet to see a F18 with such a failure. but to build a boat down to a very light weight and not use exotics will increase the chances of such a failure. Hence the Photos I posted of a F16 with catastrophic hull failure.

Macca, you did not say what brand of boat that was, and where, when, and how it happened.

I could give the details but then I would be accused of picking on a particular class...

They know who they are and they also know my position on their boat weights and current class rules.

macs - I respect you a great deal. I'm nearly a fan. But you're cherry picking the facts to support a position that has no bearing on the topic of this particular thread, unless your point is merely a cautionary statement that pursuit of lighter-weight platforms can be taken too far. I've seen structural failures (as have you) in "tough" boats like the Hobie 20, the Mystere 4.3 and the Nacra 6.0 - boats that some would contend are not good race platforms because they're "overbuilt," even though each of them enjoyed excellent class racing in their day. I remember, not long ago, there were rancorous posts from people that seemed dead set on forcing the F18 Class to begin a phase-in of reduced weight boats because manufacturers "can." I think that was just as much of a dead end as debating what they "can't."

On topic and paraphrasing a couple of great sailors - Bethwaite and Melges; Remove the excuses. Prepare your boat and kit as best you're able so that you'll have that confidence when you're on the race course. People carry this advice out to varying degrees. I know having a boat that is a specific weight is part of that preparation for people that I race often. I'm fortunate that it isn't something that worries me anymore with my current boat - at first I obsessed over it, but racing in the US F18 fleet has shown me there are other areas that require more of my attention.

my point is that the F16 class get on their high horse (lets call it a shetland pony) about the fact that the min weight they have set is perfectly easy to achieve and can be done so without increasing cost or reducing longevity.

Now at the last F16 intergalactics or whatever the event was called there was one boat that met the min weight set by the class. The average boat weight was more than 5kg over the min weight!

There are a good percentage of "professionally" built F16 platforms that are not withstanding normal use. Now I am certain that its possible to build a F16 to min weight by not using exotics but do do so takes an innordinate amount of time therefore increasing costs far above what is commercially acceptable.

To speak of realtive boat weights in terms of performance you must also factor in platform longevity. spending a lot of money on a light platform is one thing, having it last more than a season is another part of the equation.

You're sawing a familiar tune, but it's no toe-tapper. Point made, and time will tell - maybe sooner, maybe later. <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />

Exactly.

When structural materials seem to be failing, new methods of strengthing them should be sought out. Here's an idea that might help an issue apparent in this thread. <img src="http://www.catsailor.com/forums/images/graemlins/frown.gif" alt="" />

UCLA research

LOL

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Everyone has read your "opinion" of weights and class rules. Your agenda to contiue harping on it does reflect badly on both yourself and your sponsors. Catamaran sailing is in decline and rather than expending effort in trying to use youre skills and position to grow something you feel the need to berate others and tear down what at least a few people feel is a good concept.

If you must bash boats on-line then you had better upgrade your conection speed becuase there is not any line of boats that I know of that have been built problem free no matter how heavy or light.

I have owned 2 H16s which had to have hulls replaced and this is a boat in production for almost 40 years and considered the benchmark for a "tank" beach cat. (I have owned 7 varying as much as 15 lbs in weight bty) Most of the first H20s had their rear beams pull out, a bunch of the first Caps in Europe all had to have hull defects repaired. I have fixed my fair share of other hull defects and failires on Hobie, NACRAs and all of the Trac 16's I have ever seen had their deck plates rip off sooner or later. One of the new Infusion owners I know spent 3 weekends putting his boat togther due to missing and incorrect parts, only to have his hull split in half on his very first sail. Your new V40 ride seems to be a little sensitive as well.

My point is, everyone involved in sailing can add stories to this list. Boats are built by people and there will be issues from time to time. NO class is free of problems no matter the weight. I do not agree with censorship, but a lot of people spend a lot of time effort and money all across the catamarn community to try and keep it alive. Rick and Mary have spent a lot to provide this forum as a place to promote and share ideas. Ideas are one thing and no one has to agree with them, thats the beauty of it. Deliberate and repeated cut downs of something though maybe provides a legitimate case for being banned.

Ok, lets change tack here.

If I put two Blade F16 on a beach, identical hull shape and setup. Both boats had the same overall weight and complied with the F16 rules.

One boat was a std Blade as delivered by Vector works, glass hulls, alloy beams, boom, spi pole and mast.

The other was build using carbon hulls, beams, boom, spi pole and mast.

Which boat are you going to choose? (anyone who says the std boat can leave the room right now)

So you are banning me from the room? <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

I'm not leaving the room, but I'll probably take the standard one. Why?

- The all carbon one would have the weight better centered around the mast and may be a little more rigid, but that's all really. Not sure it's a win for a non pro-guy like me.

- There is no way I can get my wife to buy an all carbon boat. Too pricey.

Now if you are flush with money, by all mean use the all-carbon one. Don't expect to win all the races however, some people in a 7 year old Stealth will probably outpace you because they know their boat better and have been sailing it for ages. Skills are more important than money...

And you know Macca, you really are annoying repeating the same thing over and over again. I don't know who you are, but now I'm really curious because you seem to really have an agenda and it's unclear to me what it is.

No need to wonder...

http://www.sailing.org/biog?memberid=57184

http://www.catsailor.com/forums/sho...Number=133556&page=&vc=1

Like the automobile industry models change every year, the boat builders are free to do whatever they want in the way of modifications,
whether it is in the name of development, cost savings, safety, or sales.

Can vestal one design be maintained forever? (Even the Laser has changed it's rigging, oh my deity)
Over the years we have all seen product innovation (PI) at what cost?

PI continues to sell new boats, or new sails. Again, no one complains when sail shape changes, and chalk it up to maintenance?
If the perfect boat & sails could be built to a level where they are maintence free, NO fibreglass fatigue, no rigging revisions,
no one would need to rotate boats, and the manufacturers would SINK?

The price of keeping the manufactures afloat is PAID by the sailors sacrificing virginal one design or formula?
Product innovation is what keeps the manufacturer at SEA?
If there is NO incentive to buy a new boat/sail/innovation how are the manufactures going to stay afloat?

Your vestal one design/formula throughout the lifespan of a boat (or sails) is a MYTH.
Boats (& sails) get a little better every year, and after racing a year or two requires new. The cost of new set of sails on some boats can justify the cost of buying a new boat and supporting the manufacturer.
The price can be to high to play for some..... the builders will make a buck$ via market/product innovation resolving your issues?

Why, what possible motivation do you have to continue this? You have expressed your dislike for the rule set so move on. You have a 40 gig and an association with F18 builders so why even look at the lowly F16?

2 brand new A cats sitting on the beach
1 - 27,000 Gel tek made in Kevlar
1 - 21,000 MM A3 made in full carbon

Which boat are you going to choose? The use of exotics or more exotics for performance is more perception than reality. There is amin weight so building expensive is only really going to buy you bling factor. You can not honestly come on here and tell people that Glen or Mitch beat you around the course becuse their boat was 3 or 4 kg lighter.

Macca,

Thats a disgracefull attempt at undermining a manufacturers product to support your agenda against the F16 class.

Just when I thought you could not stoop much lower......

Shall I post some picures of F18 hull failures (new boats)here to prove a point?

Not going to lower myself that far.

Good luck in your future endeavors - your off my x-mas card list. <img src="http://www.catsailor.com/forums/images/graemlins/mad.gif" alt="" />

Marcus

I would choose the A3, the platform is stiffer and I think the boat is better built. Oh and its cheaper too <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

OMG! Evidence please? What is a "good percentage"? Just stating something doesn't make it true.

And what about all the brand new Infusions from your employer that had to have new centreboards because of a HUGE percentage of failures?

Go on, come clean about your REAL agenda macca.

Lets look at from another point of view. In Europe now the customer is protected by various laws that protect their investments...eg the buying of a boat.

Each boat is normally sold with a warrenty eg 12 months and this protects the customer against the failure of the equipment...however the customer is also protected in another way...ie is the goods fit for purpose, in the UK we call it the sales of goods Act...It is part or Euro legislation. Simply put if you paid £1,000, cheap boat,(just change the symbol for appropriate currency) for a boat would you expect it to last as long as a boat that you paid £50,000, expensive boat, Both boats float initially and do their job...however if the cheap boat breaks we say what do you expect...but if the expensive one does you get upset. Now if we make the cheap one 5-10kgs lighter than the expensive one what do you say?

So certainly in Europe boaty builders have to be careful what they do...build a boat 5kg heavier and it is robust or build it lighter and it breaks and they get sued!!!!

However it has been said before on this thread boathandling is key to a lot of things. 1 bad tack costs you 5-10 boat lengths each time...a heavier boat will loose you possibly 5 in a race.

BTW Macca I was going to say the red one...do I have to leave the room?

G'day Stuart,

Boat handeling will cost you more boat lenghts then an extra few kgs and training will pay bigger dividense than removing a few kgs from your boat..... However, whether my boat or crew weight is on min weight or not, I will still put work into boat handeling.

Ensuring my boat and crew weight is at min weight, weight aloft is reduced and boat is sound for the job are esential ingredients for boat preperation for any event.

I will take the most competitive platform out there as I do not want to disadvantage myself from the start. Then I would work on my sailing skills to futher my chances.

Yes, enhancing ones sailing skills is much more important, however going into an event without best preparing your boat is not going to help either.

Post Deleted by MTOWELL