Ben Hur surface drive

[Lil Stinker]

Was the Ben Hur designed for a Center fin? like the old Swift big B and D .

[stupidbaker57]

I'll check the plans, but I think the turn fin is incorperated into the left aluminum air trap. I'mm not running the air traps. I might not need the extra lift.

[zul8tr]

Kelly designed the turn fin into the left air trap.

http://www.boatsport.org/PDF/BenHur1.TextMark.pdf

[JohnsonM50]

A center fin would work just a matter of where & how big. A pal has a Wetback from Clark Craft, it origionally had a center & sponson fin. Whenever the sponson fin left h2o the boat would straighten till it re-set. made for some wild anticipations. Removing the center fin cured this so Id say one or the other.

[stupidbaker57]

For now, I just wanna go staight and work out any trim. If I wanna turn, then I'll slow down.

[Lil Stinker]

A fin may help you go Straight.

[JohnsonM50]

A fin may help you go Straight.

Gotta agree there but at least w/o air traps & fin its not likely to hi-side ya if it prop walks, might crab a little tho.. Also if you need to turn some to hold straight in effect you'd be giving up speed in that of many trade offs

[stupidbaker57]

Cool rig
Take it slow first time till you get the feel and behavior
Tell us about the drive shaft lubrication means. Simply greased or?
Do you have other props to try?
What is the pitch and diameter of the prop in the pic?
It is direct drive, right?
What Hp?
How did you determine the length of the engine straight pipes?
What rpm are you shooting for?
Couldn't see in the pics but do you have a left sponson fin?
Based on steering performance and desired speed consider trimming some length off the rudder.

Good luck on test day

Sorry, I missed some of the questions.
It's not 1 to 1 ratio. I've got it geared down 16 to 21 which can be changed easily by swapping the sprockets or changing the number of teeth.
The Honda engine is 27 HP with an automatic trans. (at least I have neutral) with high and low speeds.
As for the exhaust pipe length, that was easy. I found a piece of SS tubing in the scrap yard, cut it in half and welded it on to the bike pipes.
These bikes rev high at 60 MPH, so I think 6000 is just about where it should be.

[zul8tr]

You will find that the straight pipe length is very critical to the power and torque output and the rpm where these peaks occur.

[stupidbaker57]

Here's the first picture of the final drive. I can change the ratio just by changing the sprockets.surface drive.jpg