Prod, prod, prod

So, what have John and Charlie done with their spi pole here?

Picture is from the "Delta Loyd" regatta, formerly known as SPA regatta

Have a look at some photos of 12' skiff prods, they all have a dolphin striker. It allows for a reduction in tube size, and probably takes some load off the bows.

When I rigged up a spin to my 6.0 I did something similar to the 14 foot windsurfer mast I used as a spin pole. I think it would have assumed an s shape if I hadn't rigged up a pole dolphin striker.

On a skiff I understand the usage of a dolphin striker: the pole is not end supported as on a cat, hence it will see high bending moments and hence it needs a structure, which transfers the bending moment in compression loads on the tube and tension on the wire. If not, the bending moment would destroy the pole.
On a cat however, the pole is supporte at the end (where the spi is attached and at the jib. The pole will not see bending moments, but only compression: The spi up and side forces are taken by pole shrouds. Since they are in a forward direction, they produce a compression load in the tube. The efficient buckling length of the pole is reduced by the bridle wires at the jib.
So I do not understand why they are using a dolphin striker.

Cheers,

Klaus

I noticed this on Mitch's T also.
I will be in town later this afternon, if the guys are still there I will go and ask.

Spot on Smithscat !

Wouter

If I see correct, the tack halyard of the spin also runs differently, or is this common to run it via the bridle?

I can imagine the forces on the hull are quite high when you run the halyard in that way.

Gill

The way I see it, they are trying to improve strength and stability at the pole end. The luff loads on the kites is quite high and there can be a quite a bit of movement up and down at the end of pole. Easily demonstrated by lifting a boat on the beach by its spinnaker pole. A F16/F18 would have 5 to 10cms of movement quite easily. So by minimising this movement then it could give them that extra x% needed. It is an Olympic year and Booth/Lovell both tried exotic sail material in the lead up to Athens. And with it potentially being the last time for a multihull gold to be offer, trying these kind of things could be difference.

Have you tried lifting a Marstrøm Tornado by the tip of the spi pole?

Taipanfc,

I'm sorry to say that your comments are utter nonsense.

First of all the pelican striker (as the setup in the picture is called) is whole fitted to the pole itself and therefor can not improve the displacement of the pole tip under load. The shown setup still wholely dependents on the pole tip and bridle support wires to limit tip movement and as such is absolutely no different from a setup without the pelican striker.

Secondly, I have no seen a F16 yet where the tip is displaced 100 mm under (spi) load. If that is the case for a given F16 spi setup then an error has been made in constructing it. A simple 40x2 mm alu tube with 3 or 4 mm dyneema support line to the tip and midsection of the pole is enough to lock the pole up in quite a stiff sense.

Wouter

The only reason I can think of is that it adds some additional stiffness.
Something they would probably want for the light winds at Qingdao.

You are hilarious Wouter. I guess I just know nothing and should give up sailing.

That isnt my experience or understanding..
On an 18teen the pole end is supported by side wires from the wings. I am not sure if they still do but they used to run a tripod as well as wing lines. A third line runs through a dolphin striker to the tip. I believe the 12s still use a tripod still as they have no substantial wings. So to gain lateral stiffness there is a lower dolphin striker and two spreaders. These take the side forces and the under takes the lifting forces.
Now understanding the pole on a "12" is 14 foot past the bows and they have up to 30" of mast above deck the forces on the rig tend to extreme. Even a small rigged 18 pole being around the 14 foot level past the bows is extreme in cat terms. Also the poles on a skiff is generally straight out not lifted as on a cat..


Cats have tiddlers for poles (past the bows) then the forces are far less (for the size) but still significant. Placing things into 12 foot perspective a T would have a pole that would be 20-24 foot past the bows.

What I suspect is they are increasing the luff length by bending the pole down with a striker..

Tornado spis are already at ~max luff length as defined in the class rules, so I dont think that is it?

Wouter,
Have you forgotten about the compression strut above the pole that goes to the bridle wires?

The way I see it this set up will allow the spi pole to be carried lower or make the setup stiffer for the height the pole is carried.

As the pole is lowered the spi pole bridle is less affective at taking the vertical loading while quite adequate at handling the horizontal loading. So the striker below the pole will help transfer the vertical loading on the tip of the pole to the standard fore stay bridle wires via the compression strut above the pole between the spi pole and the normal bridle.

Just the way I see it.

Regards,
Phill

We sailed with less mast rake than most, mega rake did not work for us, and probably the lowest spi pole in the fleet. What Phill describes was an issue solved by fine tuning the lower bridle wires for good performance to windward. It was quite visible when beating if these were not perfect, but not while using the spi as far as I remember. Pre-bend in the spi pole was our way of lowering the tip while keeping the compression strut at the same length.

Will be interesting to find out where the advantage is and how well it works.

Explained it better than I Phil. The lower the pole at the bow, the less effect the front bridles will have.

Perhaps they are also using new cut kites that are flatter and closer to a Code Zero and require extra assistance in keeping the luff tight and consistent. The Pelican striker is a good option to assist in achieving this.

Rolf, Not sure what you mean by tuning the lower Bridals for windward work. Surely they are D12(or similar) so streach more than the wire of the upper bridals?

I dont remember what line we used there. It was some synthetic line (4mm, no uncover, silver colored) but I do remember the need to tune them to make the lower part of the jib set properly going to windward. Lining up the spi pole so it was straight and perfecting tension and length of the lines was a chore. The hulls also flex to a certain degree, so you rarely get perfect trim on the lower part of the jib even if perfections is the goal.

I think a flatter kite would give better VMG around the course, but there are limits due to measurement rules. Spis have been the area for most experimentation, but it is still the Gran Segel MK4 which is the choice. The sail John and Charlie use in the picture is a Performance cut. Interestingly enough, the reason the Gran mark 4 is the weapon of choice is that you can go quite high with it. Gran themselves say a slightly deeper and different cut will be faster VMG wise around the course if there are no other boats there. Contradicts my opening statement of course but that is part of the fun with sailing.

If the question is "do a flatter cut spi need less movement of the tip of the spi pole?" I would say the movement is so small already today that it dont make much of a difference.

That picture turned into an interesting discussion for us gearheads <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Ah; OK, so it was positining of pole / tensions to get the best set in the jib correctly.

Mk 5 is the weapon of choice for the Games. Bit deeper and can run better VMG. Suited to smaller fleet racing. The leaders don't mind it also as they can sprint away from the rest of the field in bigger fleets.

Also a bit better when lumpy with lighter winds.

Think Bundy and Glenn use a mark 4 and they are definately leaders? For a low-wind event like the games seems to build up to, they might be looking at flatter shapes to get a better L/D ratio when going downwind. Power dont always equal speed so that might be it. Dont see why they are not happy with the existing spi poles though.

It is so sad to know that multihulls are out of the games. I'll miss the experiments done in the Tornado class and the mind-food they have created.

Rolf,
Just wondering if you had measured the amount the distance between the bows of your Tornado would decrease when the forestay was loaded right up.

Just looking a 1 possible perceived advantage of running the pole lower when chasing the last poofteenth of a percent apart from the spinnaker.

The more induced tow in that you get when loaded the more the lower bridles that centre the middle of the pole and therefore tac of the jib slacken or loose tension.

This may affect the shape of the bottom of the jib as the luff may tend to get a kink in it with apex at the forestay, compression strut and bridle intersection.

Interestingly the lower the pole the lower the angle of the lower bridles to the mid pole and the less the lower bridle wires slacken with any given tow in so the better the bottom of the jib will hold its shape. This is assuming the Marstrom Tornado hulls are like other boats and give some toe in when fully loaded. I hear they are now running 15:1 main sheet so this may have started to become a problem.
No doubt there are many other influencing factors and the differences I'm talking about are so small I think we really need the guys who started the trend to spill the beans.

Regards,
Phill

Hi Stewart,

you are right, the pole on a 18 skiff is end supported as well of course. Because the angles of these wires are not very efficient they need the lateral stiffening. On cats, the supporting wires of the pole (the spi "shrouds") have a more efficient angle, hence no tripod and dolphin striker is need in my opinion. If I lift a cat on its pole I see very small displacement in fact. No skiff to lift up on our beach however...

Cheers,

Klaus

There are some big developments going on in 12's atm. Hulls are the main area (four new boats built in Brisbane for the interdominions), but the rigs are being modified to suit the faster hulls

A couple of the top boats are going with pole launchers and using large diameter carbon poles with no stays. These are matched up with spinnaker chutes which makes boat handling a bit easier, which is very important for skiffs.

I have noticed the new kiwi hull is a slab sided design to cut down on wave and spray resistance. This thinking is based on the current top Javelin hull and uses racks. All I can think of is this type of development must be a change in rules to allow racks.
Do the briz boats have racks?
I also notice that the UK "cherubs" seem to have modified their rules to become almost 12s!!

Using a chute and extender pole would mean a smaller kite or a very large chute entrance!! That long pole gave a little grief if the water was choppy I suspect.

Great to hear that 12s are on the rebound!! They are awe inspiring to watch.

Hey Stewart, see attachment. Pics of new 12 ft skiffs mould which shows the slab sides you are mentioning.

Ok. that looks more like a modern take on the "wedge". Which is similar to the bloodaxe.. I wonder if Mathews is the designer?

The new kiwi hull is even more vertical and doesn't have the wings but has racks. http://www.sail-world.com/cruising/index...=&nid=38128

This kiwi development I guess means the hulls are no longer "R" class compliant. Not an issue in Au but is in kiwiland. Again unless the "R" class has changed rules. Also great to see that the "R" & 12 classes in NZ have a requirement for 2nd hand boats!! Fantastic news for sailing!!
As they say.. start sailing get old enough and good enough and get onto a 12 then get too old and retire to 18s and finally when very old retire to cats!!

Hey TaipanFC, had a good chat with someone you may know in Brisbane today. Interesting to here what he has planned for his 12.

No, that won't be necessary.

Wouter

Phill,

You comments are indeed interesting. It could well be the explanation for using the pelican striker.

Although Rolfs comments about the tornado spi's already being limited in luff length by class rules will go against your explanation a bit.

Wouter

The fool is you Wouter.

I do not have a problem with what TaipanFC wrote and share a similar view from what I have experienced in real life.

The problem with you Doug Lord..... Sorry, Wouter is that you will base your discussion on what you have ‘analysed’ with little practical experience. Why don’t you go out and sail and learn a bit from a practical point of view.

You consistently tell very good sailors that they are wrong, they should do this to their boat and should sail their boat this way. It is very hard to treat anything said from a sailor who could not sail out of sight on a dark night with respect.

Pull your head in, go out and sail. Earn a bit of respect before knocking down sailors that have forgotten more than you know.

Max luff on a Tornado spi is 9150mm I seem to remember. We started out with 9100mm from the mast turning block to the tack block but went to something like 9130mm later on or even more. That was with less rake than most so our pole went pretty low and had quite some pre-bend. All taken from imperfect memory, so..

Think of it this way..... A 500mm strut runs from the bridal to the spin pole. The pelican (Not Wouter but the other pelican) striker is effectively an extension to this strut, running down to the pelican striker wire. The pole is very ridged in the vertical at mid pole distance and is held secure from horizontal movement by the lower bridal lines.

The pole tip is normally supported in the vertical by the bow lines, however they are not very efficient in the vertical due to stretch and the angle they run. They are very efficient in the horizontal though.

The addition of the pelican striker will greatly assist the support of the pole tip in the vertical by supporting it at to pole base, mid way and the pole tip.

Back to skool Wouter
May I suggest sailing skool first though.

Got first place prize in a 650 boat fleet a couple years back doing 24 hours of continious sailing and navigating, did you ? I also did a night passage of the English Channel in certified windforce 12 winds while helming a 3 masted barge (under sail) during the dog watch (midnight to 4 a.m.), captain got an official hearing afterwards as this really shouldn't have happened. Is that "... out of sight on a dark night ..." enough for you ?

But I don't need huffing and puffing to inflate my stature.

First place in any event still doesn't say squad when it comes down to engineering.

If the tip of your spi pole flexes up by 500-100 mm (as TaipanFC says is common) then the setup on YOUR boat is wrong; it is not that all boats in the rest of the world are wrong.

When I write down actual experience derived from sailing my boat then that is not "analysing when little to no practical experience"

Lets face it here guys, you guys think you know me but you really don't. You have no idea of what I have done and what boats I have sailed or for how many years and under what conditions. I'm no Ashby or Bundock but neither are you guys ! Your own race results aren't that impressive.

Wouter

I'll go head to head with you any day mate...... I would even do it on a 4.9 and let you keep the kite on yours. I don't hide in fleets that make me look good, but will take on the worlds best. Taipanfc the same.

Before we get into a pissing match, I must confess that I never noticed any significant flexing sideways or upwards of the spi pole tip. To put our Tornado on the beachwheels it was my job to grab the pole and lift the front part of the boat a meter or meter and a half so it rested on just the aft support. Frode would then roll the beachwheels in place under the hulls. If the hulls or stays flexed significantly, I think I would have noticed. Sadly, I never tried measuring distance between the bows like Phill suggested, then sheet in the main hard and re-measure. That would have given us something more real to speculate about.

Looks like it is time to get in touch with some of the big guns and ask what the idea is..


Edit: Oh, I notice I am too late about the pissing match..

HI Rolf, When myself and others at our club lift our F18s and Tornadoes, we do notice some tip movement in the vertical. Under spinnaker load, the movement is a lot greater (have not measured it though) and the tip flex is significant. FYI, we run quiet tight luffs with less then a quater fist twist in them.

Could you do the measurement test described above on your Capricorn and perhaps also on a Tornado? The same numbers from different F16s would also be nice to have. Then we would know a bit more about what we are discussing here and that would be great.

Good to hear. They are certainly looking to try new ideas in the 12s. The hull shapes were certainly in need of an update so will be interesting to see how the class develops.

He was also involved in a pretty cool 40ft yacht as well recently, so he gets involved in interesting concepts. That 40fter can do 9knots upwind which is better than a Farr40, with half the rail-weight. The foils on that one were certainly different (and not-canting as well)...

And Wouter, you seem to live by the adage "There is something wrong on the Internet and I must fix it!" Remember that it can be people's opinions and observations. We all live in various parts of the world and this is a place to note and discuss.

Not easy to measure under full load whist sailing. See what I can do on land though.

The test Phill and I would like the measurements from is taken on land. Just measure the distance from bowtip to bowtip. Then hoist the mainsail and sheet in hard (could we come up with an easy and repeatable way to sheet in with a known force?). After you have sheeted in, say enough to flatten the sail as good as possible, take the measure again. This would give an indication on how much flex there is in the hulls under load.

The extra width on a Tornado would make the angle of the lines from the bows to the pole tip flatter than on a 8.5' wide boat for the same height of pole tip above bows. So you aren't get as much help from those lines in resisting vertical deflection of the pole tip.

Which is why a pelican striker might be very helpful on a Tornado, but not so much on a narrower boat.

Sounds logical, but we just will not know until we at least have some measurements. Anybody up to do the same on their F16s or other boats while we wait for the F18 and Tornado numbers?

Whatever mate. I'm not dumb enough to believe a win in that contest will ever solve anything. If I win then you will just claim I got a lucky shift; if you win then that will be claimed as proof that you are next Bruce Farr or whatever famous boatdesigner you can think of. Both would be equally silly.

Besides, the last placed crew in the final F18 worlds listing can also claim to have "taken on the worlds best". I'm officially registered as a 1st place winner in a major event (650 boats). If you really want to compare penis size then all I have to say is that I didn't just take on the worlds best but actually came out on top as well. Come back when you achieve parity with that.

Personally I find this pissing absolutely rediculous. Again, personal results achieved on the race course say diddly about the validity of the engineering comments made by the same person.

I wonder how many (major) races the head engineer of the Multiplast yard has won !

So I say, come back with some actual measurements of spi pole tip flexing using the normal setup and prove that that is significant to sailboat performance before mouthing me off.

I claim two things :

-1- That the absolute flexing of the tip is not at all that much, given normal dimensions and stiffness of hulls and support wires.
-2- That the relative flexing of the tip under varying spinnaker luff loads when properly sheeted is too little to matter much in performance. Meaning the amount of flexing while sailing is to small to matter.

Note that -1- and -2- are two different things !

That will be all from me.

Wouter

Rolf,

Darren Bundock once told me that the luff length on the Gransegal kite was very important & any deviation to that length (while sailing) either thru pole lifting slightly & mast flexing above the hounds was detremental to speed. So I believe the striker on the picture you posted would be a mere additional support to help stop the pole springing under load.

FYI - When we sailed Sail melbourne regatta (Tornado's) against Darren a few years back, he gave us some halyard measurements to use on our Mk4 GS kite & the difference was amazing. That is when he also gave some advice about how important it was to keep the setting from being affected by rig & pole movements.

I was reframing from posting this info, but since Wouter & Steve are having a slinging match, thought I might try and help change the tone of the thread <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" />

Nice one Marcus! As far as I am concerned if Bundock says/does it then its gospel!

Makes me realise how big the difference between a good club sailor and a world champ is!.... Shame I'm not even a good club sailor.

All conjecture. No real data there. Wouter won't accept this kind of thing. Need evidence, and numbers, lots of them!!!

Gee taipanfc, I have a good thread with good information rolling here.

Marcus, when we went from 9100mm to 9130mm we noticed the difference, no doubt about it. I never noticed much flexing when going downwind so I find this discussion very interesting. Having those "hull flex" indications from measurements will be very interesting!

Rolf,
I've done some tow in measurements several years ago to evaluate the benfits of fitting a sub deck to hulls.
I used a loose guage on the forestay to ensure the loading was the same and I was comparing apples to apples.

On a very light weight timber platform the hulls towed in 30mm.
A glass platform was around half that and a timber platform with a sub deck in the hulls was half that again.

Unfortunately I don't remember the loose guage setting but if I find my notes on this subject I'll let you know.

Regards,
Phill

I missed this in all the fun. Bundy uses the 5 and I currently have one of his 'Games' kites.

Apologies Rolf, was just trying to pre-empt Wouter.

Thread is good and is something quite interesting and probably overlooked/assumed to be right when a boat is set up. Regularly sail on TPs and other raceboats (either as bow or spi/jib trim) and see how critical a stable pole and rig can be on an A-Sail. If the pole is not stable and is bouncing, it has a massive effect on the rest of the sail. Now, I know that this is a cat forum and we are talking about different boats, but the general concept of creating a stable luff is there. And with the kites going flatter (and those pix from Delta Lloyd are certainly looking flatter compared to a few years back), the luff stability is an issue. I think it is a take on moving in the right direction.

Rolf,
I've found my notes:
32 on a loose guage on the forestay will yeild a tow in of 25mm on the glass T4.9 platform that I measured and 30mm on
the timber T4.9 platform without a sub deck.

Regards,
Phill

Very true. I am more mid fleet (International) than a world beater, but have beaten World Champions in races as well as regattas. As I said, I will prove my worth against a quality fleet rather then hide in fleets that flatter sailors.



My Girlfriend is an Engineer and helms my Capricorn now...... Don’t make me drag her in here and bitch slap you down buddy.

Engineers are only as good as the models they create. Engineers are also at times WRONG...... Which is something you never will admit to yourself.



You came here and slagged off a mate of mine resulting in me coming in to bitch slap you. He made a claim based on personal experience by himself and many others including rock star sailors.

You came here and accused him off speaking “utter nonsense”

How about you go out and do the test, record the results and publish them with someone verifying the accuracy of them before calling BS on someone. You call yourself an engineer but have nothing to back up your claims on this except for “because I said”

I am sick of you coming here and kicking down peoples valid opinions stating they are wrong and you are right because you are an Engineer and others are not.

Not winning many friends here mate.

Pull your head in or this will continue.

This thread was started about a Tornado setup.

With the main comments comming from f18 and Tornado setups.

Why not post on the open forum and give more people the benefits of your knowledge.

FWIW I am currently looking at fitting a pelican striker to my Stealth. I was already playing around with it when this thread came up!

Background is this: I got a new kite from Grant Piggott that is the same as Scooby's and Mark_P's. It has a much longer luff than my other kites and although it fits the new style Stealths, it won't fit on mine. The pole needs to be lowered to where it is on the newer Stealths and they use tangs fitted low down on the inside of each bow. Mine are on top of the already higher bow of the old style Stealth. As a result, although I can get the pole down low, the steadying wires are now almost horizontal and doing nothing to resist upward deflection of the pole tip. On shore I can get the spin set up beautifully with a nice tight luff but as soon as we're on the water the pole prebend turns into an S-bend!!

I looked at the possibility of fitting lower take off points for the pole wires and that is what will happen when I remodel the bows this winter (if I keep the boat). In the meantime however, I needed a 'quick and dirty' solution and the obvious one was a striker arrangement which is exactly what I was working on when this thread started.......

Jalani, also fit a strop (as on the Tornadoes) from the bridal to the pole to assist in vertical stability in the mid section.

Better pic

Yes, Steve - thanks. I already have a compression strut fitted. I just need to now make it longer.

Has anyone experimented with solid fwd strutts as seen on the M20? Thoughts?

The M20 dont have a forestay with bridle but a stay going down to each hull. Marstrøm needed something to hold the spi pole up, and solid stays was the solution. But as there is very little stretch in carbon.. Hmmm..

Not in F16 that I know of.
They look a bit fragile.





BTW:
Technically this is not an M20 because of how it is rigged.

Rolf,

It wouldn't take much for the distance between the pole tip & the halyard block on the mast to vary by upto 50mm.

From memory the "toe in" of my marstrom T decreased by 12mm when the rig was tensioned & you would only need 5mm to 10mm additional "toe in" to loose the desired setting on the luff of the kite.

Added to this is the potential of the mast to move forward with the gusts also affecting the distance between the head & tack.

The movement would be noticed (performance wise) after about 20-30mm of movement

I reckon the funniest thing about this thread is the fact that there is so much discussion about the boring part (simple strut system to control pole tip flex) and nothing about the interesting detail in the initial photo...

But you seem to be enjoying the banter so carry on <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />






















Why would you paint a boat that colour if it was going to China in very hot conditions.....?

Hey, we enjoy the banter, and good to see you back here.

And China at the time is just brutal temp wise.

But the paint job same as what was used by Pete Melvin (guessing/conjecture so Wouter won't like one bit) at the recent A-Cat worlds. Some new hi-tech thingymejig to help lower water friction or something. Was mentioned in Seahorse magazine recently explaining the qualities etc etc. Boat certainly felt different compared to normal paint jobs. Wasn't across the whole boat, just the bits in the water. Couldn't take any stickers in those sections, just fell off.

So what do I win if I guessed right? Something from your desk?

Linky linky here:
http://www.morrellimelvin.com/webyep-sys...seP1Jan2008.pdf

Explains what I prob confused in previous post, that is if I am right.

Good move, I'm done with respect to Stephen; no point in continueing there I'm afraid as nothing good can come of it.

Wouter

So Phill produced some good numbers and a way to repeat the test in a good way. Who is up for measuring different F16s, F18s and Tornado? I am hoping Stephen will do his own boat and perhaps a Marstrøm Tornado.. Then it would be an exercise in geometry to find out how much the tip can move vertically.

Actually you make a good point here when trying to "pre-empt something".

Without quantification you haven't got much at all. Afterall, no-body is saying that a springy pole is beneficial to performance. And absolutely no flexing is impossible in real life. So we are comparing different amounts of flexing and trying to assign different levels of performance loss to those. At some point the differences in loses is too small to matter. We can only find this point after quantifying "the info". And we need to gether these numbers (quantification) in an orderly, scientifically and most certainly reproducable manner (= evidence).

Otherwise we'll end up with the situation analogue to those 2 guys claiming they had achieved nuclear fusion in a glass of water at room temperature. Remember that story ?

There is a reason that mankind has developped so much new technologies over the last 4 centuries out of 30 millenia of existance and that reason is called the Scientific Method (= part of the entlightenment).

Wouter

I make good points? Wow, I am impressed.

But all I have been conveying is past experience on my own boat (in the early days of F16), and also what I see in the local F16 fleet here in Singapore (which is still the world's largest).

Next time I am at the club (not this weekend, surfing in Bali instead) I will give you "beach measurements" of the Taipans and Vipers, and the Blade if that is out and about.

A personal thing first, adressed to us all. I dont think there is much value in digging into each other on any forum. I am here on the forum for a purpose, and I think most others also are. Purpose would of course be different from person to person but if a post dont have any value, the forum would be better without that post.


Sounds great that you can do some measurements! Can you do it with the tension meter on the forestay?

Yes, but these problems are not solved by the pelican striker setup as shown in the initial picture. This is actually the second tangent of my argument.

The hulls flex right ? Then they also do so at the bridle fittings allowing the bridle strop and strut to move upwards and taking the pole with it. The strut is about 40% of the full pole length so any movement upwards at the bridle strop will get amplified by 250% at the tip of the pole.

Additionally, the total relaxation of the spi luff is the result of multiple factors like tip flexing, toe-in hulls, mast flexing forward and stretch in the halyard and cloth itself. To name a few, every element in the rig is in movement and varying, yet we implicetly assume that luff relaxation is mostly determined by the tip of the pole flexing as a result of the "small" angle of the tip support wires. And then we also assume that the full pole flexing is also seen due to relatively small variations in luff tension while the spinnaker is sheeted. Why not have the tip of the pole flex upward by say 30 mm after hoisting and sheeting and then only see it flex continiously between say 25 mm and 35 mm while sailing ? Causing what ? 10 % differences in spinnaker draft ? Is that alot compared to other disturbances like waves hitting the hulls and shaking the platform ?

In scientific discourse this is called "jumping to conclusions". There is too much going on to be able to derive a foundation for such a conclusion upon inspection of the setup itself. Ergo we need specific test and numbers (=measurements) which many people feel is a dirty word these days.

Personally I don't really understand the long luffed spinnakers either. I see no real benefit to dropping the pole and luff down to between the hulls or just above it. Lots of turbulance down here due to waves and the lifted hull and also the wind speeds are really low so low above the water surface. I feel the longer luff HERE is not worth the additional hassle of securing the pole that low. But I have nu numbers to support that either I'm afraid.


Wouter

Ummm, tension meter, Singapore. If you want it Sailing Anarchy style I can get a local girl to help out, but don't expect the results to accurate or consistent, but will be worth it for the pics!

But realistically, it is hard enought to buy decent blocks and ropes locally, let alone something like that. Can try and work something out and it maybe a different method/style of measurement.

Long luff = speed and depth (both good things.)

The fun is in trying to improve, even if we have to do it with small steps and incrementally. Looking at the tip of the spi pole is one area. We do what we can where we can <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" /> Good point though! Looks like Johnny and Charlie though it was worth to check out.

Well, you shouldn't be.

I'm absolutely stringent in applying the scientific method to these situations and indeed won't accept generic gutt based story-like explanations. More often then not these are wrong by mechanism of oversight. Several people on this forum however take this stringent stance as some personal affront when indeed it isn't.

On the other hand when comments are well founded in science then I will say so immediately without having earlier dealings colouring this judgement. Afterall, a person can be wrong at one moment and absolutely right at another. We all learn and we all have moments of absolute glarity. Therefor each comment should be judged on it own.

By the same token, I will readily and publically admit to being wrong when proven so. And indeed I have done so in the past in the few instances were this has turned out to be the case. To my own relief these instances have been rather few indeed.

I have been around in academic circles for quite a while now. I have worked on real life test setups many times (where models are validated or disproven), have instructed people and students in such environments and indeed this is what I have learned. Sometimes the teacher learns from his pupil even when this pupil had been wrong many times over in the past.

The only "completely unbiased" and "fail-safe" judge or criterium in all of these cases is the scientific method and that is why application of it is soooo important. Hence my total dedication to that.

Now back to the numbers and thinking up tests. Maybe we all together can advance catamaran design understanding this way.

Wouter

Let me clearify.

Indeed "Long luff = speed and depth", but is lengthing the luff at the bottom of the spi so it moves between the hulls just as beneficial as lengthening the luff at the top.

I think you'll find a great difference here. Therefor I postulate that "Long luff = speed and depth" is not accurately enough in describing the situation and therefor possibly misleading or indeed wrong for a given seet of setups.

We need to get away from overly simple (Neatherthaler) statements of the kind "Steel and concrete = good, wood = bad"

Wouter

Lighten up dude. Life is not meant to be that serious. For the majority of us sailing is a hobby and this is a place we like to discuss it. Maybe you need to go over to www.boat-design.net as that is for those who are into the technical aspects you crave. For the rest of us, stumbling around, passing ideas, this place is ideal for us.

agreed.. the speed of a asymmetrical kite is linked to the luff length much more consistently not the sail area...

Monkey did a lot of work on this area in the early years on Prime.. Doubt if its changed.

I would suspect that an 18teen pole is actually closer to the water than a cat pole when sailing in "flat" mode.. Since the poles on the standard skiff classes are parallel to the waterline..

Then the assy on a skiff seems to lift the bows far greater than the cat... Not sure if this is just the cut?

John a quick query here as I have also the same spinnaker and will have the same problems when I get around to fitting mine, have you maxxed out the length of the pole as the early Stealths had a shorter pole than later models ? Also the later models tangs maybe lower but also angle foward more than our tip wires which go through the bow ? putting them at a worse angle than ours.

Sorry guys I hate seeing people getting kicked in the goolies for simply stating engineering fact, I reckon Wouter is right and in theory the tip should not move a mm up down sideways whatever if all dimensions remain constant, it will only change if one of the 3 dimensions of the triangle change. <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />

It appears the Spi made as an evolution from my last Spi has been polular!


Hopefully the same will be true from the Mainsail Grant and I are working on. I'll hopefully have evolution 1 at Rutland and be in a position to take orders.

Simon: How does that process work? (developing/improving a mainsail).

Hi Wayne,
Pole is not quite max (measures at 3.47m). Also all of the pole lines and bridle come off the same tang on the top of each hull. IIRC later versions of the same hull had the forward pole wires separate to the bridle.

I'd prefer not to separate the wires and have to create an additional mounting point on the bow for the tip wires.

Tony,

I've known Grant for ages (we’ve grown up sailing against each other for the last 30 years or so) and I trust his skill in making sails totally. He's made my last 3 kites for my Inter 17, and my last kite is the one Grant is now selling as his "F16 Kite". He's also made other sails for boats I've used and they have all been good.

I've always just given Grant what I am trying to get from a sail and he has delivered. So the kite spec was basically:

1, bit flatter overall
2, similar luff length to my previous one
3, Ability to carry high, yet still power for low


Now having sailed with it a couple of times, both in about 12kts of wind, I can say that it feels faster and has improved in the consistancy of my speed. Initially I thought while out sailing it was crap as I did not get "kicks in the back" I was getting from the Landy as the boat accelerated, but when I looked at the GPS, I noticed that the speeds were more constant around 17kts and I reaslised that the boat was just not slowing down as much.

I also feel that the kite needs more trimming to get the best out of it. Its more effort, but the GPS is (I think) showing that it's faster as boat speed is more consistant.



Now the mainsail development is more complex. Again Grant and I have discussed what I want from the sail, we’ve made some decisions on Luff length and curve, foot length, head length and profile of the leach. For the record, luff will be longer but the overall luff curve will be very similar to my current Landy. The head will also be longer. Foot will be shorter as we plan to add area to the top of the sail, draft will be a bot further forward and the sail will be very slightly flatter.
we are yet to be 100% certain about the leach profile, and we’ll be looking at some different battens.

I have to say that most of this, again, has been me explaining what I want for the sail to be able to do and Grant giving me options.

I do not expect we’ll get it 100% right first time, so we’ll evaluate it and then (maybe) make a few changes if needed. Should be right well before the GC.

If people are interested in sails from Grant, either drop me a PM and I'll get in touch and can keep you up to date as to how developments are going or contact Grant directly at his website, Google "GP Sails" and mention my name when you do.

A really simple test to prove whether or not the pelican striker as shown in the photo will reduce tip movement is to remove the bow to pole tip lines, while keeping the pelican striker setup normally, and then try to move the tip up and down.

Looking at the original photo, it appears as though the whole pole with pelican striker will pivot about the main beam connection, just like a normal pole without pelican striker would do.

If the pelican striker wire went through another "spreader" under the dolphin striker and continued to somewhere like the rear beam, then it would influence the tip movement because the pivot point of the pole is separated from the wire. This is how skiff poles are setup.

What the pelican striker does at mid pole is another matter and probably more to do with the jib than the spinnaker.

Gero,
You may not have noticed it but the Pelican striker is beneath a compression strut going to the bridle apex. This will stop the pole in its upward movement.

Don't all tornadoes already have that though? Wouldn't it negate the need for the pelican striker?

Wouter,

Given that there are physical constraints such as keeping the mast in one piece (therefore limiting the height of the halyard hoist) you will still see a gain in performance by lengthening the luff length, even if it means dropping pole tip height.

Been tested and proven.

Actually the strut is a standard item on F16's ever since the beginning of the class.

And Phill is right Ncik, your test won't work well because of this strut. You reasoning with regard to the difference between the pelican striker on cat pole and skiff poles is correct again. On skiffs the pelican striker setup is fixed to another point then the beginning of the pole itself and thus secures the pole in the vertical plane. On the cat pole this is not the case and all is dependent on the importance or not-importance of the strut under the bridles relative to the influence of the tip support wires.

Additionally the strut does indeed negate the need for a pelican striker in the way of shoring up the spi pole in the buckling failure mode. In fact, the strut and bridle support wires to the pole are even more effective in this way then just the pelican striker on its own.

The only way out of this situation is to just rig up the boat on land and actually measure the spi pole tip displacement of both setups when sheeting in the sails relative to the top of the decks. The difference in flexing (if large enough to be measureable) can be scientifically attributed to the pelican striker setup. When devided by the total amount of flexing one can surmise the relative contribution of the pelican striker setup.

Wouter

How about some examples

Ok, if the pole tip lines AND the strut is removed, but the pelican striker is left in place, the whole pole will still move. Therefore the pelican striker is not designed to reduce pole tip movement.

So there's either some other reason or it is useless/over complicates the pole...

I believe the pelican striker assits with the pole tip flex. If you remove the pole tip lines, the peican striker will offer more resistance in the vertical movement of the pole tip, then if it was not fitted at all.

Steve, think through it again. If the problem is hull flex, it will not matter how stiff the pole is as the geometry will change anyway. If the problem is pole flex, then it is different.

Ok I must be missing something.. If the hulls toe then the prod lines must slacken and allow movement of the tip.. The pelican would stop vertical movement at least.. Lateral movement isn't such an issue..
Guess I'm missing something..

If the hulls toe in, they do it not only at the tip but also at the bridle wires. Hence the bridle wires slacken as well and the pole is turning around the beam and not the jib tack.
However they are slacken not as much as the foremost pole shrouds, hence there will be a bit, but not much, bending in the pole and the pelican striker may help a bit, but not much, depending on the pre-tensioning and wire diameters.

The point I am missing is, if you dont want -let say- 50mm of displacement, why not just rig the pole 50mm lower as already suggested? Or retension the spi halyard? And actually doesnot the halyard stretche as much as pole tip, or even more?
Anyway, better spend the time on the water than discussing on the internet. Tomorrow will be a great sailing day in northern Germany, 4 to 5 Bft, sunshine and 20 to 25°C., Sunday as well...

Cheers,

Klaus

Hey Rolf,

Remove both the bow lines and lower bridal wires, leave the pole supported at the front beam and at the bridal strut. With the pelican stricker, you will still have prebend and will still have resistance in the vertical.

Without the pelican striker the pole tip will flex greatly in the vertical..... Therefore the pelican striker must offer some additional resistance in the vertical to the bow lines.

Steve,
I do not disagree with your statements but just for fun lets complicate the issue by also considering the movement
of the hull bridle fittings.

Lets assume the hulls are flexing around the main beam when they tow in.
This will mean the bridle fittings on the hulls come closer together.
So the apex of the Bridle wires between bridle fittings on the hull and forestay will move up.
This in turn will allow the compression strut above the pole move up which will allow the pelican strut to move up.
Which in turn will allow the pole tip to move up.

I asked myself how does this influence the situation?

Intuitively, I don't think very much.

But I don't know so I dug up the Tornado rules to get some dimensions to do some rough calcs.

Supposing the Tornado bows towed in 30mm under load.

The movement of the apex of the bridle wires will allow the pole tip to move vertically by approx 22mm with the pelican strut.

However without the pelican strut the pole tip lines would allow the pole tip to move approx 60mm.

As I said the calcs are rough because I don't have the exact height of the pole above the bow attachment point but this would be close.

So just for fun they maybe minimising the pole tip movement to 1/3 of what they would get without the pelican strut.


Regards,
Phill

Phill,

From memory our marstrom T flexed around 12mm toe in from unloaded to fully loaded - measured at the bow tips.

Whatever the end result on the pole tip, the reduction will equal stable luff length which = performance.

Marcus

Phil,

I'm guessing that you considered vertical movement only, and simplified by ignoring the small vertical movement of the compression strut under bow tow-in. Still, thanks for the calculations.

For comparison, it would be interesting to know of effective it would be to simply have a third bridle between the bow tips straight to the pole (not the tip).

More than 2 years ago, I asked Charlie O' how they liked the Eeeles snuffer (the one used in Athens). He seemed less than enthusiastic about it, but said it provided the best foretriangle stiffness, and they found that that was vital.
So, we know they are worried about foretriangle stiffness.

I was thinking that perhaps the black boat was simply a charter, because

• both of their boats were white 2 years ago, and their Nats boat 2 years ago used
• the Eelles snuffer,
• a different jib downhaul along the bridle to the hull
• a non-cascaded main sheet.

However, the connection to M&M design is strong, since they used custom centerboards at the Nationals 2 years ago designed by M&M and built exclusively for them by WaterRat, and Glaser's loft is near M&M in Long Beach. (Glaser is their coach.) So, they certainly may have painted their boat with the new slick black paint that Pete Melvin is using. It's interesting to see a Glaser jib on the boat, because Glaser is their coach, but Ogletree works for Ullman and I thought I saw all-Zucholli sails before. Maybe they are going all-out for weight savings, and water-shedding paint would certainly help there, assuming the paint itself didn't add weight (old paint was sanded off prior to painting).

--Glenn

The boat in the picture is their boat and is NOT a Marstrom

Glenn,
I kept it simple by just looking at the vertical movement but I did take into account the small movement of the compression strut due to bow tow in.

Regards,
Phill

Where is your unrefutable scientific and demonstratable evidence stating that the boat is NOT a Marstrom? Otherwise this is all hearsay and I have to discount your assertion.

I have a sworn affidavits from Graham Eales, Goran marstrom, John and Charlie, GOD and some random muppet from the beach. All confirming my statement <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

But still I seem to be lacking the science bit....

Better work on getting that then <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

And at least you guys stayed upright on the weekend unlike others.

Ogltree & Lovell were using a Marstrom snuffer with the large solid section:



The Elees snuffer is a two part...standard 2" pole with a carbon/kevlar tube fitting alongside the pole:



If the pictured boat is in fact not a charter, then they must be trying out the less sophisticated ring & bag setup due to lighter weight reasons, perhaps trading off some foretriangle stiffness.

In the light conditions expected for Quidong, it may be the best compromise.

So, if the boat is not Marstorm, then a Graham Elees? What's the advantage for the Games?

Mike.

Jikes, look at all the patches on the Eeles snuffer. An argument for the ring and bag.

Sorry it is Qingdao, not Quidong. There are 2 Quidongs that I know of in China and both are inland and not near Qingdao.

They brew the beer in Qingdao (thanks to the Germans), and that is the most important thing to know as there won't be too much sailing going on I suspect in August.

Yes, I beleive the class rules for T allow down to 2.25 kg for the pole & snuffer setup...My original Guck Snuuffer (all carbon scoop on a Hall Spars 2.25" carbon pole with mylar bag) came in just a little over this. So a full carbon snuffer must be a fair bit over the limit. Not surprising that they are a bit fragile with the builders trying to remove as much weight as possible.

They do bring a better windage profile than a floppy bag to the table...but perhaps this is less significant in lighter airs.

Check that...Qingdao for sailing & beering, Quidong for Blowcart Racing <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Absolutely. But wouldn't guarantee wind either at Quidong! Go to the beer place instead.