If you're interested look at the International 14s. They have the systems you just need to link them.

Hi all,

seems to me the only people that think that, T foils on rudders have drawbacks are those that have not used them.

Mind you I have not used them, but the improvement in performance that I witnessed racing against Barret's F14 with and with out them, has convinced me. Probably the most surprising improvement in performance was upwind, which most people seem to ignore. The reduction in pitching or "Hobby Horseing" allows the flow to stay attached to sails, keeping the boat driving through chop.

Can't see why it wouldn't be the same for F16's most cats hobby horse to some extent, particularly one up when you don't have the weight and power to press the bows through the waves and it rises over them.

Hi twicebitten,


this correct, the other big improvement comes from the fact that if the boat is pitching the T-foil on the rudder generates thrust (e.g. a forward directed force) as well. I don't want to go into the details of this effect, but it is similar to the fin of a dolphin.
However F16 racing results doesn't reflect, that the Stealth F16 are that much superior, so I wouldn't conclude that T-foils are a game changer.
For the downwind benefit of T-foils, I am not sure at all, since there are many other ways to avoid nose diving (more volume in the bows, more aft positioned rear beam to allow crew and helm to be more aft, even water ballast at the sterns) without generating tha much drag as T-foils. If the boat starts to nose dive, you can always sail deeper, a bit slower but same vmg.

But I have no T-foils, so I must see the drawbacks

Cheers,

Klaus

OK then there are those for and against T foils, I count myself definately a convert having sailed with both on the same hulls, for me its the lack of pitching and lack of bow down moments which swings it.

To move on one more stage then what about inclined foils and T foils AKA the A class where inclined or banana board seems mandatory at the moment.

A designer once likened inclined boards as the same advantage as when you rail a windsurfer with a centre board ( OK not so many around these days ) to incline the board and the baord will lift to promote earlier planning, it does seem to work.

yes agreed, for the same hulls. But if you have the choice between a boat with unsufficient bow volume and T-foils or a boat with proper volume distribution and without T-foils, what would you take? T-foils producing 20kg downforce is the same as a boat with 20 kg lead in its sterns. (I should mention that I think that ballast can be something good in some cases)

On a A-class we have lifting foils, which means lifting the bows and reducing the drag, while rudder-T-foils raise the bows and increase drag. There is now doubt about the benefit of lifting foils, once your boat can reach a certain speed. Many designs have shown that (Hobie Trifoiler, Raven, etc.)

Cheers,

Klaus

So how about my bolt on/bolt off question? Is such a system in compliance with current rules?

What if I had two sets of rudders; one with foils one without?

The T foils on the Stealth are symmetrical, when the hull is level it doesn't behave as a foil ( but has some drag ). However when the hull starts to dive the angle of attack increases the lift in a normal conventional way ( basically it tries to keep the hull level ). To check my rudders were working properly and at the right position to the horizontal I simply undid the locating pin, transferring the weight along the boat would raise or lower the rudder ie the rudder was trying to maintain its own level in the water regardless of the hull.

Getting back to the inclined foils, would the class limits give enough benefit on lifting the hull ( less hull in the water means more speed ) versus extra drag caused by the angle of the foil creating lift.

As long as you dont switch rudders during an event (except if you break something etc and apply the RC in writing for the change), I dont see why you can not do that.

Personally, I still think we dont have enough data to decide what pays off, and when tough. Good luck with it if you decide to experiment with it. Dont forget the old "time on the boat" advice

For T-foils on the rudders, perhaps time to take a look at the 14 ft skiffs. They have it higher up the blade. Way of smoothing the transition flow (or something technical like that) of the water leaving the transom. Also adjustable, and removable.

Pix can be found here.

http://www.fastcomposites.ca/gallery/index.php?pid=I14R

But looking at the rules for dagger/centreboards. There are ways in the current rules to make the boards act like hydrofoils. Noone really mentioned any of that yet in the discussion...

Jeez, do you ever think about anything else than trying to find a loophole in the F16 rules. Good luck with your hydrofoils. Let me know when you make it work.

Haha Rolf. The usual bitter reply from you. Was trying to see if anyone had thought of any ways to improve performance. I know I have.

Bitter is your choice of words, tired of the endless harping on topics alread beaten to death is my view on it. Why dont you go and build your ideas and clean up in the next regatta.

I'll have a boat on the line whenever you guys host an event in Singapore (or somewhere in Asia).

But my comments weren't beating to death a topic, and I provided info/link to how another class has adapted T-Foils on their rudders. In the 14s you can easily remove the foil bit (even do between races) and adjust the angle of attack. You just went straight negative as usual.

So go build the thing then instead of tossing up variations on how to "cheat the F16 rules".

Cheat? Yeah right. If it passes the rules, how cheating?

And as i said, when the GC organise something in Singapore or Asia, i will be there.

I'd guess we'd like to come. It's really down to the local club(s) putting a proposal together and presenting it to the GC; which would then suggest options to the membership if more than one local pitched up for an event.