Sponson angle of attack?

[kacordy]

On a p-limited rigger, what is the best angle of attack for the front sponsons and the rear ski. If the tub is sitting flat and parallel on a board, with the back of the sponson sitting on the table, what is the best angle of attack for a heat racing boat. I personally would have to research what tool to use to measure degrees. If I took a 1/4 inch thick block and slid it under the sponson, how far forward would it be in front of the sponson transom. The reason I ask is I believe my attack is to steep. What I'm fighting is my rigger starts to sponson walk at wide open throttle to the point that it walks back and forth to the point it walks the boat all the way over in a blow over. It's fine on flat test water but on racing water it has a violent walk that ends in an up and over.

Thanks for the help, Allen

[rol243]

Allen, a good sponson angle is approx 5 degrees also the ski should be the same 5 degrees. now if you put the rigger on a table and make sure its parralell with table the front sponsons will only be touching the table at the rear ends , now if you slid a piece of 1/4 inch wood under the front of sponson and slowly moved it back until it touched the sponson riding pad there should be about 2- 3/4 inches between the edge of wood and the rear of sponson riding pad so what i mean is 2 3/4 inches from the rear of pad to the 1/4 inch piece of wood face. what is this rigger ? and have you got the c.o.g. correct ?

[Fluid]

Is this a rigger design which is known to run well? While sponson aoa is important, it sounds to me that the underlying cause of the violent sponson walk is something else. If this is a JAE 21 then the cause is most definitely not sponson aoa (assuming it was built to plans).

- is the CG at the recommended location? Too far back can cause the issue
- is the strut angle correct? angled up at the prop end can cause light sponsons
- is the prop appropriate? A prop with excess diameter for the hull can cause sponson walk
- is the turn fin at the correct angle? This can cause sponson walk

.

[kacordy]

151927It's my CF Raptor that I want to get dialed in. I want to start running it on Sundays in D-9.

Allen

[RandyatBBY]

I think you were really fast Sunday, the boat looked good.

[kacordy]

I think you were really fast Sunday, the boat looked good.

Randy, 2 DNF' s, 1 heat the boat flipped 4 times but landed right side up to finish. Finished 1 heat at 3/4 throttle. Perfect water.

[kacordy]

Fluid and Rol243, I appreciate the advice and will check everything. What is the suggested CG?

Thanks, Allen

[rol243]

Allen, i don,t know much about your rigger but see where the balance point is now, i know the jae fe has its balance c.o.g. at the 60 - 40 percent marks but this is due the the under tub ski so i would think you balance should be around the trailing edge of turn fin. let us know where it is now.