Hi
Wondered whether you guys could help? I dont sail a F16 but a monohull v similar to a small cat, a Vortex. The class has historically had a problem with nose diving whilst reaching and downwind. We are considering use of t foils to solve the problem.
Ive read some good stuff about the experience on the F16 and wondered whether you could give us some advice. Ive seen photos (on this site) of the fins that have been glassed to the side of the foil. How long are they? and how have you come up with the shape (aspect ratio etc). Are the t foil fins symmetrical? What angle of attack is used i.e to the static waterline of the hull? Thanks for your help.

The T foils AKA Stealth would be spot on, I think the Vortex actually had the same rudder ( 49ER )as the earlier Stealths, alas John doesn't build the older ones any more so you would need both rudders and stocks. Don't try and recreate the wheel, just buy a set as they are not that expensive if you put your time and development into the equation.

What do they do for the sailing, I'm not convinced they work quite as we think but slightly in a different manner, that of just calming things down a bit sufficiently giving enough time for the club racer to do something about the impending nose dive, ie turning downwind a bit to take the loading off the bow. For me its the noise the T foil start to make as you get a little bow down, its enough for you to start to think things are not happening as they should.

A lot of the more experianced skippers seem to feel though the T foils are just drag but if it avoids the dreaded time of swimming and righting the boat then I'll put up with a bit of drag.

There is another builder as well who regularly is on this forum S Barrett from Australia, if you are down that way then he maybe the port of call.

talk also with the International 14 guys. If you are sailing a skiff type boat this is the standard currently.

Also Bloodaxe in UK has a T foil for their Cherubs.

Our experience has been that “T” foils do all and more than we expected from them. They dramatically reduce the pitch of a hull (which after all nose dive is just pitch to the extreme) and they do all this without any noticeable drag or detriment in any other area of performance. The also make the rudders more efficient by reducing the effect of “tip vortex” (which effectively reduces the usable area of the rudders). If you want to know the effect of T foils on monohulls talk to the sailers in the International 14’s, their whole class has been revolutionised since the added T foils to their class.

don't forget the narrow moths were running around with T foil rudders for years before going to foiling configurations. the little rudder foils were very effective and were on many world championship winning boats.

Thanks for your comments. It seems to be a question of not if, but how. As I understand it the monohull sailors are primarily using t-foils to promote early planing whilst in your boats you are using them to prevent nose diving/pitch poling, which is the problem on the Vortex. What I would like to know is how long are the fins which you use on the F16 ie from centre line of foil to end of fin, and what is the chord length at the base of the fin? Are the fins set up to give zero angle of attack during normal upwind sailing and are they symmetrical or assymetric? Ive seen the photos you have posted here but its very difficult to get an idea of scale from them. Any help gratefully received.

ncik "bob miller" had T foils on his "Venom" 18teen well before he changed his name to Ben Lexcen

v you assuming incorrectly.
the I14, Cherubs, Moths .. The I 14s had t foils that Bieker used to lengthen the wave and "trick the water to believe the hull was 16 rather than 14 foot.. Semi worked.

Since then the hulls have become very fine in the bow. So longitudinal stability has been compromised. The main purpose of the Cherub, moth foils is to stop nosediving.. The latest I14s have the same issue.. But with the kite skiffs when the kite is up there should be an upward force if the kite is well designed. What they do have is the ability to help uphill by keeping the bow down uphill by slight modification of the angle..

Size of the foils.. width the the transom of the hulls in general in skiffs..

Another avenue to pursue may be the i14 skiffs. They have been running adjustable T-foils for quite a while and have them pretty much down pat.

Tiger Mike

On the early Stealth rudders the horizontal fin is about 12cm long each side of the rudder with a root width of about 5cm and they are symmetrical.
The newer ones are much smaller with a fin length of about 9cm and a root of 5cm.
I set mine up by adjusting the stock so that the fin is neutral with the boat very, very slightly bow down. This way I theorise that the T foil doesn't interfere until it absolutely needs to - maybe that's why there's that 'famous' picture of me with a bow wave at the mast base?????

Has anyone ever put a lifting foil on the bow?

They made a lifting foil for the H16 to try and make it pitch pole proof - NOT

You never have crashed as hard as you will when those things pass verticle.

We broke both bows right off one trying this out.

That's the big drawback to any -fixed- foils, front or rear, you cannot adjust the angle of attack so if you do go "nose down" you're going to go VERY nose down if it's on the front, or get a ton of drag if they are on the rudders.

I was not having a problem with nose diving at the NA's, as long as I saw the big puffs coming and bore off deep before they hit, ease the spin sheet out, etc. It was only when I overstood the gate and was trying to keep up high in the gusts that I was stuffing it to the mast.

BUT...Boca Ciega Bay is small and very lake like, we were not sailing downwind in big waves like you would have at any open water venue in 20knots of wind. I'm not sure T foils on the rudders would "save you" when surfing down a big wave anyway, you are going to stuff it to the mast when you hit the wave in front of you, no matter what!

I do not "feel" a ton of drag when sailing with T's in the gusts; I get get more acceleration! IT IS important to understand what is happening with T's.

As the bows dive; the T's SING the whole hull; you are balancing the pitching fore by opposing it at the back of the boat; all that can happen is the hull SINKS.

Is there More drag than if they were not there? Yes; but you are not upside down or stuffing the front beam in the water and dumping power!!!!

IMO T's allow you to drive the boat harder and so you over come the small amount of extra drag.

yes but driving harder is not necessarily faster.
Anyway, anybody should use what he thinks fits him best. A lesson I learnt in many sports.

Its all a trade-off.. A standard pre-flying skiff moth is almost impossible to sail downwind without T foils.. One plants your butt over the transom and lean back.. Hope the wind doesnt tip you over sideways.. If you counteract the side effort you will nosedive..
The latest UK cherubs look like they would have the same issues.. I14s went to the T when they started decreasing the bow buoyancy.

Just put a set of curved foils in, much better performance gain than T foils will ever be. Plus they are much easier to live with (launching etc)

Oh, hang on... this free and open development class doesn't allow them... Shame

macca the question was about a vortex skiff. A single curved foil will work how on a skiff? I will give you a hint.. it wont be pretty.

As for curved foils in F16s.. So now you want
1:carbon banned,
2:weight increased but
3:allow curved foils.
You should return to taking those meds mate..

Quote "Just put a set of curved foils in, much better performance gain than T foils will ever be. Plus they are much easier to live with (launching etc)

Oh, hang on... this free and open development class doesn't allow them... Shame smile"
end QUOTE

You really do shoot off your mouth sometimes giving inflammatory self indulgent opinions on subjects of which you have apparently no real knowledge or understanding, which I can only conclude is to either increase your sense of self importance, promote argument simply for the sake of argument, or to promote some self serving agenda. You certainly don’t, in my opinion, participate for the betterment of understanding, why is that?

I don't mean to be pedantic Darryl.. or maybe I do....

Either is an English pronoun, adjective, conjunction and adverb. As a pronoun or adjective it means one, or the other, of two choices.

you can't say either and give three choices!

Macca, you failed... the test by not reading the question. that is the OLDEST trick in the book!

Hi. Thanks again for all your ideas and for correcting my misunderstanding re Cherub t foils. I had a chat with John Pierce yesterday who was very helpful. The Vortex has aluminium foils chord length c.180mm..heavy but totally bombproof and as a first effort to see whether they are going to work, Im going to have a section of foil TIG welded to the base of the rudder. Once again thanks.Will let you know if there are any amusing consequences.