rigger turn fin lift?

[larryrose11]

Hello team.
I have a new turn fin that came unsharpened, with both the leading and trailing edges flat.
So, to I sharpen the interior edge, or the Exterior edge?

The point of the turn fin is to provide just enough lift t keep the sponson out of the water
the prop wants to push the right sponson into the water, and lift the left side.

Most turn fins I see have the exterior edge sharpened.
turn_fin.JPG

IN addition to the subtle turn fin angle adjustment,
don't we want to approximate a Super Cavitation hydrofoil?
If this is the case we would want the sharpened edge on the interior surface.
in the immage below, the life points up.
turn_fin_foil.JPG

Source:

https://youtu.be/K3m06731BQY?t=109

Can anyone with experience on the matter comment?

[RandyatBBY]

Hi Larry
I allways use the bottom of the turnfin for lift or to pull down a little if needed. This summer I built a ficture 1.75"radius and a 1"radius to keep bends the same all the time. Now I tested the new bends with riggers and Sports with different profiles. I ended up with faster speeds in turn with the P LTD Rigger and slightly less speed with the Sport. Both saw increased speeds and the rigger was the touchiest.

[larryrose11]

Hi Larry
I allways use the bottom of the turnfin for lift or to pull down a little if needed. This summer I built a ficture 1.75"radius and a 1"radius to keep bends the same all the time. Now I tested the new bends with riggers and Sports with different profiles. I ended up with faster speeds in turn with the P LTD Rigger and slightly less speed with the Sport. Both saw increased speeds and the rigger was the touchiest.

Can you tell me about these profiles you tried?
Was the leading edge tapered on the exterior (like the first picture in my post), or the something different?

[RandyatBBY]

Can you tell me about these profiles you tried?
Was the leading edge tapered on the exterior (like the first picture in my post), or the something different?

I will take some pictures and get back to you.

[RandyatBBY]

Ok the basic shapes are in paper they make all sizes of turn fins by proportionally making larger or smaller. The bends are small radius = small fin. The larger the fin the larger the raidus.
IMG-3363.jpg
IMG-3364.jpg
IMG-3365.jpg