One thing you dont seem to have taken into account Wouter is the total surface area of the Stealths "T" foils, remember we have 4 (four) foils to an INT 14's 2 (two) so we're probably a lot closer than you think ! Also the Stealth is designed as a "PLANING" cat and the foils are angled to correspond with the optimum planing angle. As i'm from a Motor Racing background the beneficial side of the "T"s caught my attention although i was lucky to have a friend working for a F1 team who advised me on a more suitable section - glad i didnt have to pay for the use of their C.F.D. programming time ! anyway what are friends for ?

Mate,
The idea behind trim foils from a moth or a stealth is different to the original idea that inspired the 14's foils.
The International Moth is highly unstable in all directions. Without a trim foil the skipper needs to be somewhere behind and to windward of the hull. ie they are not the easiest to sail normally and downwind almost impossible. A trim foil makes the impossible almost possible (while still being impossible to old fat slow guys like me)

However the I14 while difficult beasty isnt that bad really. What the I14 has, is an issue with is length to power ratio. Biecker came up with the idea to use an assymetrical foil to modify the stern wave. Sort of similar to the bulb one sees on ocean carriers, but in reverse. By flattening out the stern wave, the theory goes the water "thinks" the hull is a much more acceptable 16 foot long. The longer the waterline length the faster the hull.. This is more important uphill than downhill. (Hopefully one doesnt have much hull in the water downhill). To accomplish this the trim foil needs to be the same width as the stern. Also the deeper the foil is below the stern wave the larger the surface area required to modify the surface wave.

Secondary is the anti mining aspect.

hope this makes sense.. I know what I mean anyway.

Stewart

Thanks for the welcome, this group seems to communicate very well.

I will dig out some mid to low resoltion photo's of the Blade F18 during construction & give some of the reasons why I belive the platform is very rigid.

I will attempt to create a new thread for this info & add my personal profile with all of yours.


I notice there is a good spread of people stretched to most corners of this planet & its good to see a couple of sailors close by ( Gipsland & WA).

Talk soon

Marcus

For clarification, the Stealth T foils are strictly for anti-pitchpole purposes. They do little for the stern wave--they're just too deep. When I sailed with the T-foils they did prove to be very potent at preventing nose diving. But they were also very unforgiving to any surface grass, fishing line, or as we encountered, rope from a crab pot. (At least we had the second rudder to steer us home.)

Off the subject...a really nice aspect of the Stealth rudders is the cassette up/down design. This allows you to push the rudders only part way down in light air or shallow water. Of course, there's not way to do a kick up mechanism with the T foils. But a standard rudder that had both cassette up/down movement and a kick-up mechanism would be very handy and safe. I believe some of the new Farrier trimarans have such a rudder.

" Of course, there's not way to do a kick up mechanism with the T foils."

Eric, we use the Dotan rudders, the mechanism allows for very quick "pump-action" push down and pull up of the rudders. If you`re moving slowly i`d assume you could use T-foil rudders on a system like this. Then again that doesn`t allow you to sail into the beach in sizeable waves, since you can`t surf a wave slowly ! (I`ve tried.) Also can`t have rudders partially down for steerage while launching. OK, I`ve just explained to myself why the cassette stocks are the only option with T-foils. Thanks !
Steve

I have asked the Dotan people about being able to have the rudders partially up/down for launching and beaching, and they claim you can do it by keeping the tillers raised partway up (not locked either up or down). Are you saying this does not really work?

The Paper Tigers here for many years used the cassette type rudder stocks, But with a safety "kick up" system.
The stocks were similar to the Stealth BUT the aft end was not joined but open instead. there were two bands of shock cord fitted around the stock, one at the top of the stocks and one one at the bottom. This would allow the rudders to be pulled up and pushed down as per normal but if the rudders hit anything the shock cord would allow the rudders to pivot backwards and upwards in an arc without breaking. it worked exceedingly well.

Would there be any benefit or drawback to adding T foils to the dagger? They are already in a cartridge?

Many drawbacks, no advantages. Daggerboards are to close to center of bouyancy to have any damping effect on rocking about. Also the T-foils on teh daggers will lower and raise the boards automatically with different boattrim possibly you can see them move almost continiously. The T-foil rudders are pinned into place.

Wouter

"I have asked the Dotan people about being able to have the rudders partially up/down for launching and beaching, and they claim you can do it by keeping the tillers raised partway up (not locked either up or down). Are you saying this does not really work? "

No Mary, they do work like this, no problem. Only problem is with T-foils you`d have to put rudders down quickly and pull them up quickly if they are kick-up, since while the rudder is halfway down the T-foils would create excessive drag and would likely break off the rudder in this position.

That, I`m sure, is why Stealth have them in cassette type stocks.

Steve

Then it seems that a normal rudder system would work if the trim fins can be articulated so they stay level even when the rudder is tilted in a halfway up position. Gotta keep you engineers busy.

Bear in mind that cassette rudders have been a Stealth feature from the time the boat was put into production - which was some time before the T foils were added to the boards. I've always looked at it from the point of view that if you're going to hit something with the rudders, you'll have already hit it with the dagger boards....

Hi all,

is scratching of blades a big problem, many cats in OZ use to use dagger type boxes, but I thought one of the reasons they stopped was scratching of blades. As far as kick up is concerned this is easily fixed as Darryl Barrett suggests.

Many cats I have seen have deeper rudders than centreboards, I know on the mossie I have hit rudders on bottom without hitting centreboards. Mind you kick up rudders are not of upmost importance, I sailed a Contender dinghy with a 3' deep fixed rudder for years and survived, mind you a cat is harder to steer to deep water without the rudder than a dinghy.

Regards Gary.

It seems that everbody thinks the Stealths "T" foils are only a down wind advantage - NOT - Just to clarify things i had a chat with Jon Pierce (Stealth Designer) and this is what we came up with. Going upwind with the "T"s the boat adopts a rather "different" feeling about her, when a gust comes and the boat heels/accelerates and whereas before you had that feeling through the rudders that she was trying to "screw up" into the wind now you dont. Jon reckons that its a combination of a) by keeping the bow up you reduce the forward wetted area thus leaving the centre of effort and the centre of pressure pretty much where they were designed and b)because of the angle of inclination of the "T"s as the boat heels they operate like mini-rudders and try to keep the bows off the wind. All i know is that it just improves the overall feel of the boat.

Is it possible to design T-foils that are removable -- clamp on somehow?

Those T-foils are kind of wicked-looking. What happens to your body if you are on the trapeze and slip off the back of the boat and are trolling in the water right by or behind the rudder? I know...leave it to a woman to think about a thing like that -- but men might have more to lose.

This was in Scuttlebutt:

HIGH PERFORMANCE SAILING
(Following is a brief excerpt from a feature on The Daily Sail subscription website presenting an update on the International 14 class from the UK perspective.)

Like the Moth class, the International 14s are entering a 'period of consolidation' after inclinable rudder T-foils became de rigeur a couple of years ago transforming the performance and the necessary technique required to sail the boat. After attempts at putting foils at the bottom of the rudder, the class norm is now to fit the foil half way up and there is a general trend towards thinner foils. At present there are still essentially two systems for altering the pitch of the rudder T-foil: the Paul Bieker set-up which contains an internal push rod, the foil moving independently of the rudder blade and the RMW Marine/Morrison system where the foil and rudder are one part that is inclined in its entirety relative to the hull. Bieker it seems may be moving towards the RMW system as at the Worlds he was trialing a one part system - the advantage of this is that with no moving parts to squeeze in and the foils can have a thinner section.

At present 'period of consolidation' does not equate with the 14s following the Moths in going fully foiling. At the Dinghy Show we spoke to the class' Dave Spragg who in fact has successfully tried fully foiling his 14 using the exact same gear as the Moths (lifting foils and the wand made by John Ilett's Flatacraft company in Perth) but all of it 50% bigger. "I've got one. I've flown it, but I don't think it is way forward for the class in the short and medium term," says Spragg. - The Daily Sail, full story and pictures: www.thedailysail.com

Marcus, Wouter and all,

Thanks for the info and pics.

If possible, could one of you provide a measure of some sort?

For example, the width of the rudder ( fore and aft) at the bottom.

From that data, we could approximate the rest of the dimensions.

Thanks again,

Bruce
I17
St. Croix

MAry and All,

1. The idea of 'removable' was interesting.

2. IF one were to make a fitting with rubber grommets and a 'pin'(s) to attach. Of course, it would have to be a nice job design to reduce induced turbulence.

3. IF this was possible, the one could fit to a rudder and/or a d-board.

..thanks again for a great line.

regards,
Bruce
St. Croix

in a word yes. David Lugg's fully foiling I 14 had plug in foils. Simply put two 1/4 inch rods into the foiling foil and two corresponding female 1/4 sockets. If the fit is tight enough you shouldn't lose the foiling foil. When one isnt using the foiling foil just put a piece of tape over the holes.

I guess locking grub screws could be used on this princple if one wants surity the foiling foils arent going to drop off in surf.