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Re: "T" foils on F14 [Re: Rich] #76972
06/15/06 04:45 PM
06/15/06 04:45 PM
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Sydney Australia
Berny Offline
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Berny  Offline
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Sydney Australia
Yes, get the 'rake' sorted first. Foils shouldn't have any effect on weather/lee helm.

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Re: "T" foils on F14 [Re: Berny] #76973
06/15/06 08:26 PM
06/15/06 08:26 PM
Joined: Feb 2004
Posts: 1,012
South Australia
Darryl_Barrett Offline OP
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South Australia
The rudders are set up the same as any rudder system. That is to balance the helm there has to be a small proportion of the leading edge of the blade in front of the pivot point line of the rudder stocks to keep the helm “load” as neutral and light as possible. If that percentage is too much the helm will “dart”. If that percentage is way too much, as you turn (either up or down) the tiller will be ripped out of your hands. If there is too little percentage in front of the pivot, the helm will be “heavy” both pointing up or down (this is not “weather helm” which has entirely different causes) If the rudders “trail” fully behind the pivot line, the helm will be so heavy (with extreme trailing) that the boat will be almost impossible to steer, so assuming that the helm “balance” is correct, then the foils are positioned, as I said earlier, parallel to the water surface.
When we made these foiled rudders, we moulded new stocks that let the rudders be pulled up or down vertically in the stocks, (as opposed to a “kick up” system) but with an angle that slightly “tucks” them forward under the transom to balance the helm, this allows us to position the height of the rudders at any level that we like to allow for launching, retrieving, sailing in deep water or in shallow, the rudders are placed at the appropriate height at the time and are simply “pinned” there. This was the simplest and most cost effective way of incorporating T foils. With the rudders fully up on the beach, they are completely clear of the sand.
As far as I have been able to ascertain at this time, too have an effective T foil system on a kick up system the foils would have to be automatically mechanically articulated so that as the rudder swings through it’s arc, the foils will pivot and still maintain their parallel attitude to the water. This is not a great problem of design, but it would make for a rather complex mechanical solution, not to mention, expensive.
The angle of the foils to the angle of the rudder will be determined by the rudder position, which as you say RICH, is when you have the rudder in the correct position on the boat to balance (or “tune”) the helm, then set the T foils parallel to the water surface.
On any other plane, the Foils can be “raked” backwards, forwards, or with dihedral either up or down, or they can be curved. Those alternatives mainly depend on personal preference.
The T foils themselves seem to have no effect on the balance of the helm at all; their only noticeable effect is in greatly reducing the pitch of the boat.

Re: "T" foils on F14 [Re: Darryl_Barrett] #76974
09/12/06 01:48 AM
09/12/06 01:48 AM
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South Australia
Darryl_Barrett Offline OP
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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.

Re: "T" foils on F14 [Re: Darryl_Barrett] #76975
01/17/07 11:50 AM
01/17/07 11:50 AM
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waynemarlow Offline
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Interesting to see that the foils are getting both bigger and longer, does this not sort of make one think that most of the gain is not coming from actual foil section but surface area in the water resisting up and down motion which sort of leads me to ask is this not just the same as adding hull length which then leads me on to ask is this not then making your F14 more like a F16. I am not against foils as my Stealth has them but eventually someone somewhere is going to grumble when the rear of the foil is some 400 - 500 mm behind the boat.

Re: "T" foils on F14 [Re: waynemarlow] #76976
01/17/07 01:05 PM
01/17/07 01:05 PM
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Posts: 695
Ft. Pierce, Fl. USA
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Ft. Pierce, Fl. USA
"I am not against foils as my Stealth has them but eventually someone somewhere is going to grumble when the rear of the foil is some 400 - 500 mm behind the boat."

If you are honest with yourself people who sail boats (I won't include sailboarders or kite boarders in this) have more than their fair share of crybabies...LOL...

If you have been on this forum or any other sailing forum for more than 10 min you know what I mean...

Your boats lighter than mine/more expensive than mine/larger sail than mine/is wider than mine/ has carbon hulls/has carbon beams/has glued in beams/has carbon mast/has carbon dagger boards/has Kevlar hulls/has canted dagger boards/has canted hulls/has longer dagger boards/has bigger sails/has better sails/has a taller mast/has a longer spinnaker pole/has a self taking jib/has a wave piercing hull the list goes on and on ad nauseas...it's amazing any progress gets made at all. Your probably right add the "T" foils to the list LOL...

Regards,
Bob

Re: "T" foils on F14 [Re: waynemarlow] #76977
01/17/07 06:17 PM
01/17/07 06:17 PM
Joined: Feb 2004
Posts: 1,012
South Australia
Darryl_Barrett Offline OP
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Darryl_Barrett  Offline OP
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For T foils to be effective they don't have to be behind the transom of the boat.
That is accepted, at the moment, as the most logical and easiest place to put them, but if they were placed as a fixture under the boat finishing at the transom or fitted as a retractable "small" dagger board (with T foils) through the hull behind the rear beam of the hull, they would be just as effective.
You are correct in saying they make the boat “feel” as if it is longer, but that is only symptomatic, the effect that they have on the handling of the boat occurs in quite a different way than it would if a couple of feet was added to the waterline length. The foils control the horizontal directional way in which the hull travels through the water in a more efficient and controlled way than the extra length and buoyancy of a lengthened hull would. To look suspiciously at the addition of T foils would be similar to arguing that dagger boards should not be allowed as they improve the performance of the boat and a smaller boat with “boards can out point a larger boat without boards so that the smaller boat can sail as if it has a couple of feet more in waterline length?

Re: "T" foils on F14 [Re: Darryl_Barrett] #76978
01/18/07 02:17 PM
01/18/07 02:17 PM
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waynemarlow Offline
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You sort of missed the point Daryl, I will clarify my thoughts a little better ( please bare in mind that I'm not against foils on cats ). Your T foils are in effect not really foils ( as in lift creating foils ) at all, simply extensions of the rudder as a flat blade towards the rear of the boat. If you faced that same blade forward under the boat would you achieve the same result, probably not as you wouldn't have the same leverage / damping effect.

You could also ask the same question in a slightly different way, if that same T foil was attached to the rear of the hull say 200mm down on a small foil section where it should almost have the same effect and by the vary nature of the V shape allow the rudder to still Pivot, would it be deemed to have increased your water line length ?

Great it works, probably works very well if your calculations are correct and good on you for doing it, I'm very tempted to do it on my F16, but is it really in the spirit of things ?.

It is a bit of a conundrum for me as I think personally any help that a F14 can get, the better as I do think we will all end up sailing smaller and smaller length boats ( less weight and mass to lugg around off the water )but I do think also that in truth we are just adding to water line length, mmmmmm.

Re: "T" foils on F14 [Re: waynemarlow] #76979
01/18/07 08:25 PM
01/18/07 08:25 PM
Joined: Feb 2004
Posts: 1,012
South Australia
Darryl_Barrett Offline OP
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Darryl_Barrett  Offline OP
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You are completely correct Wayne. The farther aft that a horizontal foil is placed the more leverage effect it will have (like putting much less weight on a very high aspect keel and extending it much deeper in the water – it becomes a much lighter displacement boat with greater righting moments), BUT that is not the primary effect that you are trying to achieve from a T foil which moves in relation to the water in an entirely different manner (and T foils ARE true foils acting as a two directional lifting system – both up and down, not merely as a “leverage” plate akin to a cavitation plate on an outboard motor). The foils function is to “guide” the horizontal direction of the hull through the water and in so doing “dampen” the tendency to pitch, not beat it into submission, and as such there is not a great deal of difference in the actual effect of the foil whether you place it forward, up to approx’ 600mm of the transom, or 300mm aft (and any position in between). The leverage effect that you refer to is not of any great gain (or loss) as it only comes into full effect if the boat is not moving forward but instead stationary and pitching bow up then bow down on any wave action. Then the leverage of an extended aft foil will greatly dampen that pitch. Once there is any forward motion that same leverage effect is virtually nullified. I have said this before, you have to visualise the effects of a T foil in a global form and not in a two dimensional form to understand the way in which it is effective. Personally I find it difficult to relate the inclusion of T foils even remotely to any effect of waterline increase. T foils do improve the overall performance of a given hull, but then there are many things that improve a given hulls performance that are never looked at as undesirable. The example that you give I.E fix the T foil to the underside of the hull on a small vertical foil just forward of the transom so that the trailing edge of the foils came level with the transom, is one of the preliminary tests we conducted, and the resulting effects were exactly the same as we have achieved with the foils on the bottom of the rudders, and by doing it that way (attached to the underside of the hull) there could be no argument that there was any hull length increase. The only reasons that we didn’t go with that scenario was “sailer perception”. We found that most sailers would accept the concept of foils on the rudders but not foils attached to the hull.
Still an interesting argument and one that I am sure will continue to be debated into the future.

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