We have now sailed two Alpha F14's (one with "T" foils and one without, and we have even swapped the "T" foils from one boat to the other), over several races and just out together "testing", for some time. We have "swapped" boats as well, all with the object of a "yardstick" test against each other. So far the results that we have obtained is that the "T" foils, throughout the full range of conditions, make a consistent and definite improvement over an identical boat sailing without “T” foils of between 9% and 11%. This is better than any results that we had anticipated and has completely justified all the R & D, design and mould work that it has taken to finish this project. Now we will just have to see what results are obtained from racing against all the other classes in “open” competition.

Are they providing lifting force or just making the rudder more slippery through the water?

They'll have two benefits Jake. One will be the reduction of tip drag as the rudder is turned (they will act as end fences). The other is grip on the water to prevent the bows from diving.

The only drawback I can see from these is storing them. You can not just throw them into your sailbox.

Other than that, these look like a sweet sweet upgrade. I wonder if this will be eventually used on more boats? I know Stealth F16s have T foils, now the Alpha F14s. This is great news!

Have you experimented with the rake of the (horizontal) foil for optimum performance <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Now, now Robi. Surely you're not telling us that you simply 'throw' your (non-foil) rudders into your sailbox? <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" />

<img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

I am a little concerned with drag, when the boat is not at optimal trim. Also drag when you turn the rudders whilst flying a hull.

Would also pick up a lot of weed and be hard to clear.

Yes, if you get a weed or a trash bag, lobster bouy line or anything else wrapped on there you will have to stop, lift it and clear it. That won't be too fast! Unless that sweep is enough to let it slide off.

Oh, and I could see where it would help keep from a picth pole but as for the speed improvment, 9-11% of what? <img src="http://www.catsailor.com/forums/images/graemlins/confused.gif" alt="" />

Adding a spinnaker to a boat gives roughly 5% improvement to a boat's yardstick, give or take less than a 1%...... So your figures may be out.

How about adding T foils to the daggerboards too? Admittedly, it would make installing and removing the daggerboards a hassle, but it would also reduce tip vortices.

D. Ho
TheMightyHobie18 1067

There is no "detectable" extra drag from the foils, in fact the opposite seems to be more the “consensus”, the actual “T” foils don't hold any weed (their rake lets any weed “slide” off) but the rudders (or any other rudder system for that matter), will catch weed, in exactly the same way they would normally with or without T foils. The helm is balanced at all times with or without both hulls in the water. The foils primary function is that they reduce "pitch", both nose down and nose up, (from 2 knots to 20 plus knots) and keeps the hull platform sailing virtual horizontal to the ambient water surface at all times, and thereby stopping the mast and sail from "darting" forward and back as the hulls pass over surface undulations, this keeps the sail working more consistently (and efficiently). It greatly surprised us when looking at sailing attitude comparisons between the two cats on video, of just how much the mast of a cat without foils oscillates in relatively “flat” water and light winds when compared to a cat with foils that showed next to no pitch. Then, of course, there is the bonus of being able to make radical “bear away” (or up) manoeuvres with or without kite, and the bows never dipping more than a couple of inches.
The performance figures ARE slightly subjective as some were taken from race “finish time” differences between the two cats and calculated against the elapsed time of the races, while many more were taken “free” sailing over a variety of distances and comparing the two different times between the cats to their overall times for those distances, and as such I am not “claiming” them as being “written in stone”, but, the greatest difference we had was 12.5% and the least difference was 4%. More importantly, there never was any time that we tested, in any condition, where the cat with T foils was equalled by the non-foiled one, which would seem to indicate definitively that, what ever the exact difference is, there is a distinct advantage using T foiled rudders.
As an aside Stephen when we added the spinnaker to the F14 our yardstick dropped 11%. (And the F14 is one of, if not the only cat with spinnaker where the area of the spinnaker is quite a bit less than the area of the working sail(s))
And ROBI you are absolutely right, it’s a “pain in the butt” not being able to put them in the standard sail box, that’s why we are altering our moulds for our sail boxes so that we can do just that (quote) “just throw them into your sail box”.

I think they look SEXY. Good work Darryl.

True, however when a standard rudder catches weed, you can kick the rudder up quickly to clear, or fly a hull enough to get the rudder out of the water. With the T foil, you can not kick the rudder up and flying a hull will not see the weed fall off the bottom. The only way to clear it would be to lift the foil partly up, hang over the back and use your hands... = SLOW


They may reduce pitching, however when the boat is not trimmed with the foils perfectly horizontal..... ie too much nose down or nose up..... What about the resulting drag as the foils are fighting the trim of the boat???? It may not be pitching but it would be like running with the hand break on if not trimmed correctly. These foils are non adjustable also. I believe the I14s will trim their foils neutral for down wind raking the rudder further back (nose up) as the breeze increases. Then they rake the rudder forward (nose down) for the upwind legs.

I here a lot of 'Talk' about how good they are, but am yet to see it backed up by hard data after controlled professional testing. Hence why I am the skeptic.



This is effectively using the foils to fight against the boats tendency to drive the nose down. The foils fighting against this = drag..... Better to use crew weight more effectively to control the boat trim and better seamanship on the maneuvers ie smoother maneuvers instead of using the foil as a hand break to keep the bow out.

Also, sometimes you need to round up quickly, lifting the bow up…… Such as when you are surfing down a wave in pressure and want to flick the nose up over a wave before plowing into the back off it.



To use the Tornado as an example which saw a yardstick adjustment after not only a kite was added, but a larger main sail and addition of extra trapeze........ The big T's yardstick dropped initially 4.35% from a VYC off 69 to 66. Later adjusted down to 65 which is a 5.8% drop from the original yardstick.

So if you were seeing differences anywhere near this let alone in the double figures.... You have other factors adding such a large influence on the results, that it renders your results inconclusive.

I doubt very much that the addition of foils will see anywhere near the performance increase that adding a spinnaker to a boat would.

We know first hand through strenuous testing just how they do perform and I did not start this thread to get into an "answer and question, bun fight" session concerning the pro's and con's of some "sceptical theorising" of how or how not foils do or do not work. I have simply posted our FIRST hand experiences of our testing of them "out in the real world", under an enormous variety of sailing conditions. Now any one can draw on all sorts of theoretical situations where they can extrapolate as to "will they do this" or "I feel they will do that" or any thing else that they can imagine, but before "digging too deep at hole" perhaps it would be prudent to actually see how they perform first hand, then these opinions may carry the weight of proof and not just supposition theories.
It’s not just some theory but documented fact that we took the YV yardstick of the 4.3 Alpha Omega from 88 down to 77 in twelve months. Now that was also something that the majority of sailers said was "impossible" as well.

I do remember one particular sailor, having done more then a little scientific modelling of beach cats, who was derided as delusional when the quotes his estimate of final performance. I'll bet he is grinning from ear to ear with this validation.

Wouter

Not a 'bun fight' mate.... I am genuinely interested and throwing my thoughts out there. Am very interested in peoples reply and would love nothing more to see it proven. I am not big on the ‘It works because I say so’ but am after at least some well thought out answers. I have an open mind but will not be lead blindly into believing. I was hoping what I was giving was constructive criticism.

If anything…… Some of what I have said could be thought about and if it is valid, used to improve systems or sailing techniques. We all learn through each other.

We currently see the F16 and now F14 class using foil rudders. No offense but these 2 classes are far from professional classes. Why have we not seen other more professional classes trial these. May be most of these other classes have something in their class rules forbidding this ????????

Also, this is not directed personaly at you but the entire foil / no foil debate.

Personally I see no fundamental scientific reason why the F14 can not acquire bigger performance increases from the upgrades then the Tornado.

As a shorter platform it is more held back by depressing the bow during gusts and short wavelets. It is a widely accepted phenomenon that shorter boats do tend to behave more nervously. Mathematics with respect to bouyancy distribution clearify this. The f14 is at the other end of the spectrum when compared to the Tornado and as such is will receive proportionally the greatest benefit from T-foils.

Also the boat was relatively slow at VYC = 88 is is always easier to make a slow boat more fast in absolute sense then making an already fast boat equally faster. This is also an effect of proportionality.

10 % of 88 = 9 points
10 % of 64 = 6 points

But also the aerodynamics involved will stimulate such a discrepency. The Tornado is more held back now by limits in efficiency while the F14 was more held back by limits in power and the ability to sustain that power in a low drag attitude.

I've noticed mayself plenty of times on a 14 ft boat that each time a gust came in I needed to sheet out alot to prevent the bows from diving. Noticeably more then on a say an 18 footer or 20 footer. With the T-foils this could well be negated allowing the driver to drive the F14 ALOT harder then before.

Reasons like this can easily acount for bigger gains to the F14 when using an upgrade then when using the same setup on a 16, 18 or 20 footer.

Personally I feel the 16's can still do well with a T-foil upgrade but 18 foot and higher it could be insufficient to make application attractive. I know for certain that it was proven ineffective on a A-cats. But then these boats are alot longer for their width then the F14's are.

Wouter

As far as yardstick goes..... I guess Forster will be a test.

F14 - 77
H17 - 82.5
H16 - 81.5
Mozzie (sp) - 80
TheMightyHobie18 - 78.5
Taipan cat - 76.5

F14s without foils - Berny's 430
F14s with foils - AO

I am not doubting the yardstick of the F14 and Forster will be interesting.

I am questioning the effectiveness of the foils and to this date am not convinced. But hey, if you want to believe, then go right ahead, and I will continue to doubt until convinced otherwise.

Also I am not doubting that the foils reduce pitching or alows you to load up the boat more...... I am questioning at what cost (drag)

Good job

I did not think the reduction in drag would be worth the effort. I did not think about the increase in stability.


Did you reduce the area of the rudder, when you added the T-Foil?


A few thoughts:

The thought 10 years ago was to reduce the area by tapering the foil. I don't know what they found when they tested actual aircraft. The test data is controlled.

I have noticed that the newest aircraft have smaller winglets and there is no abrupt transition between the wing and winglet. It looks like a decreasing radi curve.

I also wonder if you need a end foil on both sides of the rudder. i.e. instead of a T could it be a L or an almost J.

I would not argue about this. It is beginning to look like the waxing or not waxing the hull debates



Carl

Hi Darryl
Can you post some of the video of the two F-14's saling together...one with and one without? Sounds like you put some serious effort into the evaluation of the T-foils.

Whether or not a "professional" class came up with the concept... uses the concept in its class... or approves of the concept... has nothing to do with whether the concept is valid. Keep up the research and thank you for sharing with us your findings.

Regards,
Bob