"T" foil rudders - Pitchpoling is History !

Hi Mike,
- Did you put glass the T-foil onto the existing rudder, or make a new rudder in Balsa, add the T-foil bit and then glass the whole thing ?
- Got any pics of the rudders, either finished or under construction ?
- Do the cassette type stocks ever get jammed, a big concern while surfing a 4ft wave towards the beach.....

Steve

I am looking at T foils for my next boat. No good in this situation as they do not kick up !

Mike added foils to an existing pair of blades. The Stealth originally used the same foils as rudders and daggerboards (I think they were actually 49er rudders) - then most owners got the bigger R dagger boards and so had a spare pair of rudders!

I've never had a problem with rudders sticking. As Simon says, they don't kick up. But the big advantage is that you can sailo with them well up without the steering becoming really heavy - because you still have the correct profile of blade in the water.

I'm still not entirely convinced by the T foils though - in light conditions I'm sure they must crate more drag.

What if you were able to change the angle of the horizontal blade slightly so that it holds the sterns down in heavy air and lifts them a little in light air? (Or be able to change the fore-and-aft angle of the whole rudder slightly to achieve those effects?)

I guess I am thinking of sort of how the fins/wings work on outboard motors to control trim of the boat.

Currently John (Mr Stealth) has a Set and leave set up with approx 2 degrees of drag (I think) on the Stealth range.

Hi all,

on Int.14' Skiffs Lindsay Irwin uses a twist grip type tiller extension to adjust the angle of the vanes on the bottom of the rudder blade. Angled down to lift bow pull transom down downwind, angled up to give lift to transom upwind. He swears by it and claims it is easy to operate once set up. But it must create more drag as it has more surface area than standard blade and when used to trim boat must create drag, I guess not as much as transom dragging or bow under water though.

Yet again played around with this sort of thing on sailboards years ago, but found for speed you couldn't beat a properly foiled straight fin with no extra bits on bottom. Of course sailboards weren't battling nosedive or transom drag though.

Maybe I will talk to Linsay some more? Definetly would be a weed catcher though a big problem on my home waters.

Regards Gary.

G'day All F16 Enthusiasts. This is my first post to cat sailor, so here goes....

My Name is Marcus Towell & live in South Australia.

I have been perusing some of the many posts within the F16 forum & have found the discussion interesting.

The Blade F18 was our project here in Aus & I am now looking to build two Blade F16 to replace my Marstrom Tornado.(If anybody is interested in any photo's of the blade just ask)The Blade F18 is going well & continues to improve when our development timetable allows.

I too am very keen to see some photo's of the T-foils as there some serious 14 ft skiffs at our club that use a similar system ( their trim foils are actually bigger than the steering foil !!)

Looking forward to reading future posts.

Marcus

The horizontal foils are bigger than the vertical rudders?! Bigger in what way -- in volume, in fore-and-aft dimension, in side-to-side dimension? (Sorry, but I don't know the correct terminology for describing these things in engineering terms.)

Marcus, Welcome! Look forward to hearing more from you in the future.

I'm interested. In fact I think I could speak for many here and say we're interested. Would appreciate it if you could post some picture here.

Thanks in advance.

Mark.

What a perfect time to use this image.

And here you have them :

Note the white foils are of 2002 the Black ones are newer and more faired.

And now for a work of art !

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I second Marks comments

Wouter

Wouter,
What are those pictures of? The Stealth?

Pictures are all of Stealth F16's; The white ones are off a UK based boats and the Black ones are off a US based Stealth F16 in California. Of Mark Talla. Eric Poulsen took them when he went up there for a sail in 2003 I believe.

There are quite a few T-foils in the F16 class at this moment. Currently all on Stealhs but a large portion of all of the Stealths produced have them. The other builders (except VWM) have looked at the setup and even had a test sail with them. I don't know wether they will go for the T-foils as well, maybe Marcus will. I personally still have to test sail these but that is planned for this spring at the Dutch Stealth Agent.

All very exiting.

Wouter

Welcome to the group Marcus,

It is a great honour to welcome you and your friends to the F16 class. To be honest; guys like you are very valuable especially at this time of growth. I'm thrilled with your decision to go with the F16's for your personal craft. And I'm quite sure the baby Blade (to the F18) will proof to be a little kitten with a big roar.

I've posted a few pictures of the T-foil rudder system in reply to your request. The foils on the stealth are much smaller than the I-14 because their function is a little different. The F16's are not as nervous as the 14's and more control can be left to the pilots. To foils on these cats only slow down the undesired movements to a level where the crews can adjust the trim in a comfortable way. That is all that is needed. Any excess funtionality will only lead to unnecessary drag and level-off the peak performance of the craft. Everything is a trade-off and one can loose as well by overdoing on a good thing. I really don't there is any benefit to large surfaces as the F16's are more controllable in basis and don't have to fear a wipe-out as much as the little skiffs.

And I second Marks comments that we all love to see pictures of boats in production/assembling.

Good luck,

Wouter

(co-founder & Chairman F16-class , 32, The Netherlands)

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