All in good fun, boys.




The answer to that is partially yes. Alot of classes do have rules like the overall width rule that prevent T-foils from being used. Other reasons are that builders don't want the additional hassle, so don't expect Hobie or Nacra to develop and introduce stuff like this into the cat scene. Other reasons may well be pure scientific in nature. As I wrote in an earlier post; it can be quite possible that longer boats do not get the same boost from fitting T-foils then the shorter boats like the 16's and 14's. It was tried in the A-cat class and discarted. However the length to width ratio of the A's is far higher then the other classes. The A's are just alot longer and also alot smaller then the other boats. And of course they have less weight in that carbon mast. All factors that limit the possitive effect that T-foils can have.

I have personally sailed with T-foils a couple of times and I must say they truly make the platform very stable. I own a boat without T-foils and I do feel a significant difference despite both being F16's. I dare not quote an performance increase % but I'm convinced that the T-foils can't be just waved away. I wouldn't be surprised if well designed T-foils turned out to be an advantage that just a score of sailors overlooked for such a long time.

Afterall how long did it take before the bulk of (professional) sailors and classes started using wingmasts ?

In this line of thinking I have no special regard for professional classes. More often then not they are more conservative then non-professional classes. Most development is done in small and tinker oriented environments.

Wouter

“More often then not they are more conservative then non-professional classes. Most development is done in small and tinker oriented environments.”

Wouter I think you have stated that very tactfully…

I would go so far as to say the “Professional” classes…as well as established 1 design in general… take an adversarial position on innovation…“It’s all about the sailor”… the boat is just a means to an end…To others it’s all about the advancing of boat design regardless of the repercussions to established classes.

There is plenty of room for both points of view…and lots of room in the middle…but please Stephen do not use “professional classes” as any indication whether a new innovation has merit or not. Even if proven positive beyond a shadow of a doubt…those with the mind set of “it’s all about the sailor” will vigorously resist any change to boat design which redefines the level of the playing field.

Regards,
Bob

I have only one sail to support this in a Stealth F16.

All IMO of course.....

The T foils make the ride down wind very much smoother and you can drive the boat much harder. There were times while I was getting used to it that I was thinking that "I'll need to bear off in this gust to stop the bows going too deep, when in fact I did not; the foils gripped and the boat just went faster.

I agree 100% with T_A that they are adding drag as they are holding the back of the boat down and you could go faster with crew weight further back.


but you run out of crew weight ! At some point you have to shed power to keep the bows out (and so not going at full speed). Yes, by adding weight to the back of the boat by moving back you fix this, but you can only get so far back.

From sailing the boat only once, I can see that it will by critical to sail the boat all the time with the foils not dragging until you need them. The foils could make people lazy as the bows just don't dip anywhere near as much.

Consider this

2 boats are exactly the same except one boat has T foils on the bottom of the hulls.

Boat A and boat T (has the foils)

In light wind with NO waves

Boat A should be slightly faster than boat T as the T foils have more drag.

In light wind with waves

Boat A might be faster as it has less drag, but, boat T will slop around less on the waves as the T's prevent some of the wave action moving the boat around (so the rig shakes around less), but boat T has more drag and this will be compounded by the wave action.

In moderate wind and small waves

Boat A should be slightly faster as it has less drag, but boat T may have some small benefit from the more stable platform

In moderate wind and waves

Boat a might be faster as it has less drag, but, boat T will slop around less on the waves as the T's prevent some of the wave action moving the boat around (so the rig shakes around less), but boat T has more drag

In strong wind with smallish waves

Boat A might be slightly faster as it has less drag, but boat T will have benefit from the more stable platform and will also be able to drive the boat much harder downwind as there is less probability of pitchpole.

In strong wind with big waves

Boat A might be slightly faster as it has less drag, but boat T will have benefit from the more stable platform and will also be able to drive the boat much harder downwind as there is less probability of pitchpole.





Now my views are thus :

1, T foils add a little (and it is very little) drag as you have more area in the water.
2, T foils make a massive difference sailing downwind in the windier stuff as the boat is much less tippy for/aft and so can be driven MUCH harder. Once you are standing at the back of the boat, you cannot go any further back.
3, When the wind is lighter, crew positioning is vital to ensure the foils are not dragging.
4, I've not sailed the boat in waves yet so cannot comment.



Another thing, over the last 8 years, I have gone from sailing a 20 foot boat (Hurricane 5.9) that was a dream to sail down wind in the big stuff, loads of volume up front and so we did not really factor in pictpoling into many sailing days

Then I moved onto a 17 foot 6 boat were you do have to be a little more carefull (still loads of volume up front). I've now gone to the Stealth (waiting delivery) and we'll see how that goes, but on my first sail,it was behaving more like and 18+ foot boat than the 16 foot boat that it is.

IMO T foils are the dogs danglies....

Scooby,

I agree with ost of your points except that a more stable rig will have more power because the reduction in "hobby horsing" will leave the rig powered up more of the time. Add that factor to all of your wind and wave ranges and it seems that the T-foils would be a better solution around the bouys.

I don't know much about the rules in the Tornado Class, but F18 Rules don't specifically rule T-foils out, except Rule A.2 which includes "Formula 18 class rules are closed class rules, what is not expressly permitted is prohibited."

T foils are forbidden on the Tornado as they are not expressively permitted in the class rules. Chief measurer himself confirmed this some time ago.

I probably have missed it somewhere, but is there a reason why T-foils cannot be used on kick-up rudders?

The reason they won't work on "conventional" rudders is that you wouldn't be able to use the rudder in anything other than the fully down position - there would be too much drag otherwise when you have the rudders down just enough to sail out of shallow water.

I am (trying) to say that the rig stability helps.

I currently believe T foils are the way to go !

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

But why would there be water drag if they are in the fully "up" position? Maybe a little air drag.

And being able to flip them up briefly would help to get grass off the rudder blades. Grass is a major problem in many areas of the United States.

I thought maybe the reason for needing a casing so the rudder can go straight up and down was because the foils cause increased stresses on the transom?? Or maybe too much stress or "drag" for existing rudder systems to keep from kicking up??

OK foil fans…… I am not having a shot at you and commend what Darryl and the Stealth boys are doing……. However I have some questions and am asking for answers.

You do not have to address my questions and can side step as much as you like, but if you do, you will not convince me of the benefits.

Wouter’s comment about foils possibly having a greater effect on a smaller boat was very interesting and was constructive feedback.

Below are my queries and it would be appreciated if someone knowledgeable could comment on them.

1) I believe these rudders will catch weed and other debris and be difficult / slow to remove compared to non foil, kick up rudders. Do you agree or disagree. If you agree, then have you thought about how to rectify this. If you don’t agree….. Then why.

2) I am not doubting that the foils reduce pitching or allows you to load up the boat more...... I am questioning at what cost (drag). Whilst there would be minimal (still some) drag when perfectly trimmed, what about the drag when the foil loads up at the top or bottom. The reduced pitching and ability to load up the boat more may feel like you are going quicker…… But are you.

3) How much drag is produced from them in large chop when pitching is inevitable?

4) What testing has been done. Tank testing???? Have you done extensive side by side 2 boat testing with boats identical in set up and crew weight. Taking results from racing is far from an accurate way to gather data.

5) How experienced are those doing the research in controlled environments and gathering data.

I will try Steve,
1. We have sailed through weed with two identical F14’s, and both caught weed on their rudders and were forced to extract that weed. One cat had T foils the other didn’t. The T foil cat slid the rudder up in the case and extracted the weed, slid the rudder back down and continued sailing. The other one had “kick” up rudders and swung the rudder up cleared the weed and swung the rudder back down. Conclusions were that the swung rudder was quicker BUT the difference was very little. Definitely not enough to be a deciding factor in “rejecting” the T foils.
2. When you look at the so called “drag” from T foils, you have to approach the question not from a “static” two dimensional perspective as if the boat was standing still and the bows went up and the transoms went down, (or visa versa) if this was the case there would be enormous loads (not drag) transferred from the foils directly to the transoms, but instead the hulls are moving forward THROUGH the water when the bow “dips” (or rises) and therefore we have a three dimensional “global” situation. Think of the foils not so much as resisting the vertical movement of the hulls, but more so as directing the direction of the hulls through the water in the vertical plane, exactly the same as the rudders do on the horizontal plane. Because of this the change to the angle of incidence of the T foils to the actual direction of the movement of the hulls is very small (only a few degrees) and as such the resulting drag is approximately the same as that caused by the rudders when steering in a straight line (which never in actuality really happens as even in a straight line we are always steering a little up to counter leeward drift) This is why when you calculate (quite simply) the potential “load” that the area of the foils can generate (IE for the Stealth numbers have been bandied about of 100 or more kg’s) it would appear that the transoms need to be substantially reinforced to take that extra load, BUT in reality due to that “force” not being by any means a static vertical load the transoms can handle the T foils without any additional reinforcing.
Our testing so far, between two identical F14’s, one with foils and one without showed that over the full range of our extensive testing the cat without foils could never match the cat with foils under any sailing condition.
3. The so-called drag does not seem to be a “variable” with the different sea states. The drag is a constant relatable to the actual speed of the foils through the water. The greater the hull speed the better they work I.E their efficiency goes up with speed greater proportionally than the increased induced drag.
4. Read my original posts you will see that we yardsticked TWO identical F14, one with and one without T foils
5. I think that my academic qualifications together with my lifetime spent designing, testing, building, and selling catamarans may just qualify me to perhaps have my “testing” practises accepted as valid.

Thanks Darryl, that has swayed my opinion some....

I do still not like the idea of the rudders catching weed though. Most places we sail, weed is really a problem. Forster is a problem and will see how they go there. As you said, the problem may not be enough to justify dismissing them. There is obviously a potential problem there, that those developing the systems will or may have already have looked into. A solution may be found, or it may be just a case of bearing with this disadvantage whilst gaining advantages else where.

Look forward to watching the continued development and see if bigger classes start experimenting with them too. Wouters comment about boat size does have me intrigued.

Steve, I think not only boat size would be a deciding factor, but also hull shape. The Tornado dont have much volume along the keel line compared to current designs, so even our "big love" might benefit from T-foils. A design like the F-18 Blade with lots of volume low down will probably benefit less, except for keeping the boat under control downwind in wild conditions.

I sail a Stealth without 'T' Foils and would love to try the T's just too feel the difference. I only have two conerns about T's the first is the nodding dog syndrome. I cann't see how they could reduce this due to how waves are formed (sea swell not lake waves) in the first place. Infact, T's could be slower in some instances. The other concern is that I quite often find myself sailing downhill with my windward rudder tip just flicking in and out of the water. When a gust hits using T's and before I can react the windward rudder might still lift out and when I bear away would the T prevent the rudder/hull to come back down as quickly as I would like whilst trying to bear away. If so this would counteract sailing 'harder' downwind. In saying this I have spoken to John Pierce, Jalini and Wayne and I don't think they would ever go back to normal rudders so their advantages must out weigh their disadvantages.

Has anyone addressed how these rudders are used in water of unknown depth? I've kicked up a rudder or two in areas I thought were deep enough (the Keys mostly), and while it's a pain to run back and reset, at least it didn't break the rudder.

The same is true for hidden lobster trap lines that aren't marked or are somehow sitting below the surface. If the T-foil rudder caught one at full tilt, would it kick up (or out, or something), or just bring the boat to a screetching halt?

If there is no provision to kick up, would it be prudent of the sailor to keep the minimum daggarboard depth greater than that of the rudders?

The problem is that you have to be at a complete standstill to kick them up - or the foil will want to drive the rudder down as the boat moves forward. The solid rudder trunk does also allow very precise control over the angle of the t-foil while under way - and that's got to be really important. This kind of trunk is used on skiffs like the 49'er (throwing stones <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />). Even our I20 style kickup rudder systems will allow the rudder to angle back just from loading (especially when the springs wear a little).

I also sail a Stealth without T-foils although I have on a few occasions borrowed a pair.

I don't believe they cure the "nodding dog syndrome" - that's based on racing alongside a T equipped boat and noticing that it was pitching up and down in the same way that my boat was. Mind you, we do get a pretty nasty short chop quite often which doesn't help.

I've always thought that the problem would be with the increased drag in light winds. That doesn't appear to be borne out in practice however with boatspeed for "T" and "non-T" boats being very similar.

I've not noticed any additional problems with weed. Where I sail (the Firth of Forth) the problem tends to be with floating seaweed around spring tides. Whilst the damn stuff does get caught on the rudder and usually requires a guddle over the back to clear it, I've not noticed any getting caught on the foils.

If you hit something with a cartridge rudder (with or without foils) something may break. But as you'll have already hit it with the daggerboard you probably won't be going too fast!

I've only briefly sailed with T-foils in strong breeze - about an F5 as a squall line came through as I was on my way out to the race course. In those conditions you cannot understand how amazing the foils are until you've tried them. There is no tendancy for the bows to dig in at all (even with no spinnaker up), you just make the boat go faster!

My conclusion is that in big breeze the T-foils are faster because they let you push much harder. In light breeze I don't think they're faster - but I'm not convinced they're slower either!

From what I am reading from guys who have/are sailing with the Stealth system, it appears to me that they perform much better with stronger wind (greater speed) and have a far less noticeable effect in the light?? To me that would indicate that the working surface of those foils could be a "little on the small side". We had a similar effect with smaller foils early, and it was only after I did some recalculations and we enlarged the foils that an appreciable performance improvement was documented throughout the full range of speed, BUT most dramatically in the light (and particularly choppy)

They seem to be trying "foils" on everything! try this link for a video of an 18' skiff (in a very old and battered condition) completely hydrofoiling, does 14.7 knots in a windspeed maximun of 6 knots on Lake Geneva Switzerland. First sail on the water with foils.
http://www.jeanpierreziegert.ch/video/FirstFlight.mov