Does anyone have a file for a unifoil shim they would be willing to share?
Would like to print up a couple of shims in the .1 to .25 range.
Following as I’d like to see if we could tweak the design of the Unfoil shims to work with my KD Marlin.
Thank you! Now I just need to tweak them to be less than 0.5.
@Erik you’ve mentioned .25 deg shims. What are you using?
KD Maui has .25 degree shims
@Clifford I’m riding a unifoil 140 and at my weight (100kg) i’m looking to go more negative than 1.5 Anyone have print files in Negativ 2 and negative 2.5?
whoaa never had anyone ask for such a low angle of incidence , your back leg is gonna burn , or you cruizing at slow speeds ?
if you just want to give it a try then id just cut a tin can up and insert a piece under the minus 1.5 shim
Being a bigger rider i’ve always negative shimmed pretty agressively for efficiency and made up for it with a more forward placement. I’ve kind of gotten used to that mast pivot point in my tracks and even with -1.5 i’m still not able to go as far forward as i like without blowing up my takeoffs. I atleast want to try going to more negative to see what it does. I might also try negative plate shim and see if that helps.
As I go more negative and mast farther forward, as I see it I’m getting more efficiency and less stability in the foil(loose and pivot in yaw). What other trade offs am I making doing that?
I’ve got a buddy with a 3d printer who’s messing around with those thingiverse files, i’ll have him post the -2 and -2.5 if someone else wants to try.
at a certain negative angle aren’t you going to start creating some weird drag? I would imagine there is diminishing returns beyond the point where the tail stab matches the front foil’s angle… but I don’t know very much!
Eg picture below, this is how I understand it anyway
(0.5 as the front foil Angle is from this thread)
Very curious to learn what the -2.5 feels like… I’ve never tried a negative shim on the 140, maybe I should
Ride an Omen foil and see what you think of it. Angles are not set like a normal foil.
couldn’t you clip off the front “nub” from a Uni +2.5 shim and flip it around backwards to get this angle?
So, in your drawing, the front wing angle of attack is fixed and the rear wing is variable. In reality, it’s more of a blend of the two. The rear just has so much more leverage being on the end of that stick. Most of what the rear is doing, is setting the angle for the front.
Pretty much every foil I’ve ever written I end up significantly negative, shimming the tail and moving the mass forward heaps to get it where I want it. As I make those adjustments pumping gets easier from increased efficiency and turning gets twitch year. The thing you lose his stability as the foil moves forward it gets much more unstable.
Also, At the end of the day if the rear is making any down force at all, it’s just adding drag to the equation.
As far as riding omen goes, I wish I had the money. I’m as close as I’ll get now, riding a knock off omen tail that somebody made for me!
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What’s the size and thickness of that knock off tail youre using with the 140? I’ve gone to 1.5 negative on a 14" Shiv and it slightly improved the effeciency but screwed up the turning for me. Then went back on negative 0.5.
What did make a massive difference to efficiency was sanding down the belly of a 14" Shunt, reducing the thickness and loosing about 3mm off the trailing edge / chord. Riding that one with a zero deg shim it’s alot faster but still has all the glide and pump. And more pitch control on steep drops. 95kg on 140 and 170P.
My point is maybe try a smaller more efficient stab?
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I’m not feeling that. I started out with the stock g10 3 pack in 13" and found them to be too thin(from a flex perspective) and thats why i moved to the more robust carbon tail i’m on now. The new tail is definately thicker, but is noticably better for me.
That makes sense, so you can get the front to an lower effective angle by reducing the tail.
I’m surprised you can run so much negative shim and still have decent turn, but I’m going to try it out. Certain tails don’t really work for me at 0, or at least aren’t as intuitive.
Its important to remember it comes with more forward foil placement.
At my weight on older foils, getting that efficiency was a matter of necessity to pump the way i wanted. After some time my riding style developed around the forward mast placement that came with it (forward pivot point) and i’m now tuning to get the mast where i want it.
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I rode the negative 2.5 today and it was great. Better efficiency and glide, let me ride the foil farther forward where I like it. It DOES require some board/plate shim(shim thick part forward board up foil down) - really helped put that board at a better angle on takeoff to prevent pearling.
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