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I have a Nov 2013 lift
when riding through Swells it has a tendency to track sideways , this I believe is caused by the pressure wave under the surface .
I have heard this from others as well.
To over come this added a small win tip Fin to work as a vertical stabilizer .& it works great .
Also to improve performance used glass putty to file in he hole on the fuselage where the retaining Nuts are .& also in the gapes between the foil & the fuselage .
the workmanship is not real good , but it works well .
Happy foiling . .

Looks like a good idea how did you attach the twin tip fin? Also can you still detach the front now that you used the filler?

the foils still are easily removed as the screw heads are on the other side
the fins came with 2 small post & one screw hole
removed the rear foil , removed one of the positioning posts , positioned the fin so the post was over one of the foil screw holes & then drilled a hole in the fuselage between the 2 mounting screw holes .
Counter sunk the hole a little & counter sunk the foil a little as well .
Attach the fin with the screw & then mounted the rear foil ,
then used some 5 minute 2 part epoxy on the edges of the new fin for additional strength , ,this epoxy is brittle so easy to remove if you want to try a different fin .
I tried 3 different ones & positions before I was happy with this .

backwards?!

on my hydrofoil I also decided to install the tail fin

you should notify MHL about the problem and your fix. they may not have known. you should get a free T shirt at least.

PS it work much better when you put the fin on front wards .
turned the fin 180 & it works much better

lodwik wrote:PS it work much better when you put the fin on front wards .
turned the fin 180 & it works much better

You mean you turned it opposite from your picture, so it is turned like on a TT ?

Yes, the fin has a round leading edge (at the diagonal so to speak), and usually sharp at the trailing edge - so for the yaw stabilisation to be good and smooth, it has to be turned that way.

Althoug - a "rudder" as it is here, would be even better (more stabilisation less drag) if it was turned exactly like your picture, just with a sharp TE and a round LE (which is the opposite of what TT fins are...)

But it is so small, that it really does not matter - as long as it is not too sharp at the LE (no matter how it is turned), which will work worse

Peter

yes it is small ,but turning is has the effect of moving it backward & it made a good improvement .
Also Lift is now putting vertical fins on there new foils

@lodwik