Dunlap 27'' O/B tunnel hull bow bouncing up and down ?

[Andris Golts]

Hi all the other night got a chance to try out my Dunlap 27 the boat is set up on 4s 5000 mah lipo UL-1 motor on top of a R.E.K lower unit spinning a x440/2 prop with its c/l a 1/4'' above the sponson bottoms. I noticed running down the straight aways the bow bobs up and down gently. I tried to move the lipo around to change c of g but did not make any difference! How can i eliminate this problem ? The speed is not there also maybe low 40's my 30'' tunnel with 4s full P" set up is in the mid 50's any help would be great. Regards Andris Golts.

[JestDanny]

I've have a Dumas 24" sprint running on 4s 5000, UL-1 motor atop a K&B lower, spinning a P-215 or X640 to a top speed of 45 mph (gps). CoG at 30% my ride height is about half of what you run an I got a couple degrees negative trim. My VS-1 hull runs a similar set up(P-limited), uses a TFL large lower, get the same results mid 40's. Lower your ride height a 1/16 or add a degree of negative trim, see what happens, one change at a time if it don't work, go back try something new.

[Andris Golts]

Hi JestDanny thanks for the suggestions i will give these a try. Regards Andris Golts.

[Fluid]

There can be a big difference between a “limited” setup and full “P” power. With that small prop and motor, low-40s is a good speed for the OP’s boat, and is actually slightly above the design speed of the original nitro hull. You’ll need more prop to go faster, but mid-50s with decent run time and motor life is probably not gonna be there.


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