Drive Angle

[TRUCKPULL]

I have a question for Sport Hydro builders.
I have found that with the speed we are achieving with the rudder and turn fin set straight in line, that you have to adjust the strut to get the boat to run in a straight line.

As of right now I am using a 1.5degree wedge between the transom and the strut mount.

Seeing that 1 degree is .210" per foot.
From the rear of the strut to the back edge of the ride pads is 18.5 inches.
So my drive force is at 31/64 inches off center. (or 1/2 off center)
at the rear of the sponsons.

If I was to move my strut sideways off center to mount it square to the transom.
How much would I have to move it?

Larry

[NativePaul]

That sound about right, I haven't run 1 in years but used to be 5-6mm on 12cells and your probably running 3x the power now, so a good chunk further makes sense.

[TRUCKPULL]

That sound about right, I haven't run 1 in years but used to be 5-6mm on 12cells and your probably running 3x the power now, so a good chunk further makes sense.

Paul

Are you saying that you move the strut sideways 5 to 6mm, or using a wedge or bending the strut and move the thrust angle 5 to 6 mm from center at the rear of the sponsons.

Larry

[NativePaul]

Move it sideways, so the the thrustline is still parallel with the direction of travel.

[srislash]

I have a question for Sport Hydro builders.
I have found that with the speed we are achieving with the rudder and turn fin set straight in line, that you have to adjust the strut to get the boat to run in a straight line.

As of right now I am using a 1.5degree wedge between the transom and the strut mount.

Seeing that 1 degree is .210" per foot.
From the rear of the strut to the back edge of the ride pads is 18.5 inches.
So my drive force is at 31/64 inches off center. (or 1/2 off center)
at the rear of the sponsons.

If I was to move my strut sideways off center to mount it square to the transom.
How much would I have to move it?

Larry

Larry, do you have any counterweight in either sponson? Just thinking this may affect the tracking. I am just laying out a hydro now and am contemplating all of this.
Shawn

[TRUCKPULL]

Larry, do you have any counterweight in either sponson? Just thinking this may affect the tracking. I am just laying out a hydro now and am contemplating all of this.
Shawn

Yes Shawn -_ have 3 oz on the right side at the CG.
This is for my "P" Sport Hydro - right now my GPS has been coming back in at 80 - 81 MPH - MAX.

Larry

[srislash]

Yes Shawn -_ have 3 oz on the right side at the CG.
This is for my "P" Sport Hydro - right now my GPS has been coming back in at 80 - 81 MPH

Larry

Man that?s cooking!! I have an AC Edge hydro (45?)here that I?ll be happy with anything around what my R42 does (70mph). What size is P sport?

[srislash]

Man that?s cooking!! I have an AC Edge hydro (45?)here that I?ll be happy with anything around what my R42 does (70mph). What size is P sport?

Another thing would be to shim the turn fin to straighten it out.

[Mike W]

Another thing would be to shim the turn fin to straighten it out.

Why are turn fins asymmetrically sharpened?

[TRUCKPULL]

"What size is P sport?"
"P" Sport Hydro is 4s Max - 34" max length.

"Another thing would be to shim the turn fin to straighten it out."
I have tried that -Also my fin is adjustable - I like to have it square with the inside of the sponson.

In the picture, you can see the stainless-steel threaded rod, coming from the side of the body.
The apposing locknuts, on each of the fin make adjustable.
This also stops side Flex in the mount.
Then I add one of my Titanium Turn Fins;
https://forums.offshoreelectrics.com...-s-and-Riggers

From Mike

"Why are turn fins asymmetrically sharpened?"
Because you are only turning in one direction.
I have seen people try to put a very dull angle on the front of a turn to help with prop walk.
That is not the way to correct the problem.

Our problem is that we have gone above a beyond the speed design of the hull.
It seems that every time a race hull is improved, we as builders and racers find a way to make them faster.

I found the 1.5 degree setting by bending the strut. After about 10 tries it ran straight as it should with the fin and the rudder set straight.

Larry

[TRUCKPULL]

Shawn
You mentioned your R42 Cat
What ?s and motors (Twins?) are you running.

My 8S Twin 42" Falcon Cat, Setup for oval racing, my last Max on the oval was 86MPH.
My 6S Twin 36" Avenger, also setup for oval racing, my last Max on the oval was 80MPH.

Larry