Be careful that it’s not so big it becomes a scoop to dig into the water when the bow goes under.
also have to be careful as the boat heals that the foil doesn’t change the direction of the boat… thus requiring you to add rudder inputs to keep on course…
Any underwater vane of this type has multiple effects. A vane at the bow will have a reduced lifting effect as the bow depresses, eventually promoting submarining (positive feedback leading to instability). A vane at the stern (in the opposite orientation) will have increasingly beneficial effects as the bow depresses, so may be preferable (negative feedback, inherently stable). But the stern vane will also increase the effective displacement of the boat because of its downward thrust. Either one of these will also cause a lee helm as the boat heels, which may be beneficial to the extent that it balances the weather helm that naturally occurs when heeling, providing that the vane parameters are selected properly. Either one of these will also create additional drag, which may reduce windward performance sufficiently to negate any benefit.
But the fun part is trying out these things, or at least analyzing the possibilities; sometimes they actually work. There is a detailed analysis of the sizing needed on a stern vane in an earlier thread, but the side effects were not analyzed.
Walt H.
The polar Foil took to the water again this weekend all be it in a different shape. The raised edge was too acute and so i made a new Polar Foil to see how it reacted. The resultant change was barely noticable in the light winds we had this weekend so no real results to report.
It was interesting to note that WaltH’s comments on this and I remembered that I had used a foil on my first Bottle Boat Rudder ~ the action of this was quite marked and visably kicked the stern down to compensate for the bow attitude.
Rgds
AndyT
This is a “developmental” class, right? 
We’re now in “developmental mode…” :graduate:
Andy,
This idea sounds as if will have the effect you intend: - thank you for being open about it.
I have done a little background reading and found something rather similar (apparently) in a patent published by an Olaf Prilo in the spring of 1900. Being a patent it was more tantalising than informative:D
Please keep us updated.
BTW do you have a reliable method of emptying the bottles before use as boats?:D?
andrew
Hi Andy,
If this thread is all about the rudder foil as depicted in your photo then I doubt you will have much success with it. It is cute though.
I tried using a rudder mounted foil in an early test on one of my Bantams. The foil that I used was left over from my first (and curtailed) F-48 trimaran build. It was a lot larger than the one your bottle boat sports. It did nothing to counteract the nose diving effect but rather exacerbated it by vastly increasing drag.
The problem with gimmicks to resist diving is that the sail area that we are asking these boats to carry will overwhelm any contrivances. A rudder mounted foil (even of gargantuan size) is too close to the fore and aft center of bouyancy to be of much use. The arc of nose down pitch is radical and irregular from moment to moment, so a small foil (and here I refer to the one I tried) will just cavitate and stall.
Even if a rudder foil were to work effectively for a particular nose down angle a small variation (and in Footies there are almost no small variations in relation to its length) will make the foil a liability. The reason that they are used on 48 inch long multihulls is that the multihull’s length dampens the fore and aft pitch variations to a narrow margin. Their width (with the outriggers) also helps to keep the rudder more or less vertical and the foil immersed and in a horizontal plane where it can have the most bite. Footies aren’t so well behaved.
Neil
The rudder mounted foil is a nonsense ~ clearly the bow mounted Polar Foil is the way to go ~ trials on Pussyfoot were clearly a success despite her forward mounted bow sited mast position the polar foil managed to lift the bow significantly out of the water and stop the usual Footy tradition of submarining ~ there has to be something significant here as to why this Polar Foil is having this effect when previous attempts have not worked.
This is clearly some sort of breakthrough for boats of our size ~ we have a fantastic chance to ~ (now you are going to think me really mad) have a Planing Polar Foil Footy ~ I kid you not this is cutting edge, the curled edge of a Depron plate seems to have the right section and flow to lift the bow. I am amazed at how well it works.
Has any one else tried a Polar Foil yet clearly this is something that needs to be given plenty of thought. I am so pleased with the way that this has improved the performance of PussyFoot I feel sure that others will find a benefit with the way in which this shape helps to stop the submarining effect Footy’s have been renowned for
Best wishes
AndyT
So Andy, can you get someone to videotape the polar foil in action.
It would be great if you could mount one on a design that has a sistership to function as a control. A true comparison on different points of sail between otherwise identical boats would make believers out of the skeptics like me.
Let me see what i can do to help you ~ not alot of wind about today but tomorrow about midday it might pick up a bit
Rgds
AndyT
Andrew H ~ your research into the patent published by Olaf Prilo in the spring of 1900 sounds very interesting it makes me wonder how close it is to my Polar Foil?
As for emptying bottles I have my own patented method but generally involves the use of a glass :zbeer:
I had better go and charge the batteries ready for tomorrow ~ I would love to be there to see Neil’s and a few other faces when they see how well the Polar Foil really works!
I do hope they are principled enough to accept the Polar Foil and not poo poo it ~ I think it works quite well for what it is, after all I have always tried to be open about these things and share my findings and it’s the thing I enjoy about Footydom.
Footys are for fun and seeing people laugh and enjoy them selves ~ sadly some people are far too serious about some things and seem to have forgotten how to smile
If Olaf Prillo were alive today I’m sure he would have enjoyed seeing the Polar Foil as well
Anyway tomorrows another day and I will have to juggle the camera with one hand and the sticks with the other.
I feel sure that once Neil and others see how the Polar Foil works they will be astounded, I know I was.
Rgds
AndyT
Ok well I was fortunately able to take advantage of the change in wind and shoot this sequence that I hope will convince others of the advantage of a Polar Foil.
http://www.authorstream.com/Presentation/AndyT-169913-polar-foil-entertainment-ppt-powerpoint/
Thank you for your forbearance
You can count me in among the skeptics, Andy. The polar foil looks like some kind of water brake!
funny video! :devil3: 
Well Done Andy.
A successful venture, I`m convinced.
Best wishes and good hunting. :lol: :devil3: :witch:
Hello fellow Footyers ~ I do hope that you have now seen the funny side of this it took ages to plan and execute do go and have a look at the video
Olaf Prillo would have been proud of me
Hope I did not offend too many of you ~ if I did then sorry
Best wishes
AndyT