Shapeable airfoil/wingmast for an ice boat

[556Geoff]

I posted a thread last year and for drawings look there. My current foil has a five foot chord and is fifteen feet tall. The hounds are at the top of the mast to allow free swinging of the foil underneath. The individual full length batten adjustment lines (twelve lines for each tack) are run to two separate travelor cars, which are controled by two separate magic boxes. The rig is sized for a Nite Ice Boat, which is a popular ice boat class. Weather permitting, I'll test the rig on a boat in two weeks and I can see what breaks and maybe what works too. Here are some before photos:

[eponodyne]

Looks badassed, dude. What do you reckon the whole lash-up weighs?

[daiquiri]

Looks great but also a bit fragile. That airfoil has quite a big camber. Are you sure one tiny spar will be enough to counter the aerodynamic moment?

[kach22i]

Very sexy looking, what is that clear covering material you are using and how is it attached to the solid spar structure?

[eponodyne]

I'm not sure at all, but I think you'll find you need a spar toward the rear third of the wing. That's a pretty long cantilever from the man spar to the trailing edge, a little structure there might help (though I don't know what that would do to your camber sheeting system).

[556Geoff]

EponoDyne: Yes I have concerns, I haven't weight it yet, but one person can easily carry it.
Daiquiri: I expect this whole rig to die at some point. I followed the old websites recommendations for a narrow foil section and a slightly larger than the site recommended (free standing rig). Ice boats can go 4-6 times the speed of the wind, so I like stays thankyou.
Kach221: The sail material is a sailboard/window material from SailRite Site and its attached to the custom carbon/glass molded battens with the top 3M basking tape product. The multitude of lines are the smallest Amsteel made, to reduce weight and any stretch. The paired battens are free floating around the spar with a lashing or loop of Amsteel to hold it against a block of glegicell. There are many questions about what will break first: the basking taped joint with the battens or sail, the many knots, the SS wire loops that all the lines are tied to on the battens, the twist in the upper leach from lack of support while under way, and the leading edge tautness or lack of it at 60+ knots of apparent wind (if the rig even gets that far).
Eponodyne: This rig is a Westernized version of a Chinese two sided lug rig. The spar is placed close but just ahead of the point of effort of the rig (so the rig is still self tacking). Yes, one of the many questions is where is the center of effort going to shift as you change the shape of the foil? But in a static world (HA HA) the mast should take most of the load (compressive).

[tom28571]

Looks like you have spent some serious hours working this out. I laid out a couple of these long ago and they got very complicated too. I suppose that the two halves of the sail surfaces work independently with shaping tension being applied to the battens.

Have you figured out what happens to the sail shape when the mast bows between the step and hounds? Can you control the camber at different height independently? How do you think it will compare to a rigid segmented wing?

Good luck.

[nero]

I am working on something like this for my catamaran.

Are your trailing edges fixed or sliding joint on the battens?

From my tests the trailing edge has to slide but leading edge can be solid ... if the sail is not intended to open up.

regards

[556Geoff]

Tom28571a: Yes, the mast or spar bending and its effect on the foil shape and resulting wrinkles is a question I want to see play out. At this point, all the control lines are pulled the same amount so incremental adjustments for twist or changes in foil shape havent been allowed for.

Nero: Yes, there is a sliding flat surface on the inside of the battens to keep them in register when they slide by on the back end of the foil. The original softwater-foil was two-sided, dousable, and opened up for down-wind sailing.

[BWD]

That's a cool wing.
If/when you have to redo the tensioning lines, you could probably use thinner/lighter/cheaper thinner spectra braid than the (2.5mm?) amsteel there. They make good braid for fishing as well as power kite sports, for example, 1.34 mm diam./500# spectra, $55 for 150 yards. (Price from a fishing place). Plenty strength and lighter/cheaper than amsteel. Of course, you already have all those little pulleys, but I just thought I would mention it...

[556Geoff]

Thanks for the info. I expect to build a number of upgrades.