Nose diving HELP!

I’m riding my foil assist SUP on F1 board 120 liters with Armstrong 85 mast 1850 wing and 195 tail…on bigger faster waves the nose of the board dives and I can’t bring it back up…I find myself 100% on back foot just to keep the ride alive…I’ve shimmed, moved mast forward etc but it keeps happening only on big fast waves…any suggestions?

You’re maxing out the speed of the foil. Pretty sure that’s what @Erik is referring to with “forward pitching moment”. You need a faster foil that won’t do that can handle the higher speeds of those waves.

Yeah that’s what I assumed too but I’m reaching the same speed winging on flat water and it does NOT nose dive…that’s why I’m baffled

MPH on flat water vs water speed of a wave. It’s not always the same thing. Plus, curves.

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As your speed increases, so does the drag on the foil. You can fix this with tail size and angle as well as fuselage length. More negative shim is the first thing to try. Than a longer fuse or bigger tail. A shorter mast and baseplate shim (nose-up) can also help.

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I tried a 4mm and 6mm base plate shim and didn’t help…I have been riding a 70 fuse but also have a 60, which one would be less likely to dive the nose?

Also I was riding a 232 tail and switched to 195

Try the 70 fuse and 232 to start then the baseplate shim. That will probably fix it. Are you using straps?

I don’t use straps because it’s a SUP foil assist and you need to place your feet far forward to counter the motor thrust then hop backward after catching the wave and getting on foil. Can you please explain negative shim and base plate shim nose up? Thanks

Never thought about a foil assist much but is it maybe when you go from high to low on the mast and the motor setup suddenly introduces a ton of drag causing your weight to go forward as you slow down?

No it’s 100% when I get going very fast on a big wave…every wave i catch feels perfect until I get going maybe 25+ mph then the nose dive starts and it’s almost impossible to pull it back up…the assist is pretty fun as I can get 30 waves in an hour versus 10 prone waves…the bigger board sucks but it’s fun to switch it up

Once in foil the motor never touches the water again…I’m on a 85 mast

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