setback 101, prof needed

[nelsoncat]

I need to figure out how much setback a 16' flatbottom needs. Is there a rule of thumb or do I need to try different combinations and see how it reacts. What do I look for and why. I'll take this on a pass/fail basis.
Thanks
Craig

[amityray]

http://forums.screamandfly.com/forums/showthread.php?t=100526&highlight=setback

[David]

Does the flatbottom have a skeg?
You'll want enough set back to get it out of the water if it does.

[nelsoncat]

Yes it does have a skeg, in the middle of the bottom. I never thought about that. It would create a turbulence I would imagine. I measured it today per the Rickracer formula on the link and with the 1400 bolted to the transom its like 3" setback. It is getting a 220lazer short shaft on a Bobs Jack. I am guessing thats not enough. The boat will be mainly used for skiing. I have owned this boat for 28 years and it only broke 50mph once. I am on a mission to make it faster, just because!!!!!!!

Craig

[msm]

The boat will be mainly used for skiing.


Craig, the more setback you add, the slower it will plane. If it were mine, I'd buy a jack with minimum setback. Going from 140 to 220 hp will give you a massive speed increase anyway. Then throw on a trophy prop and you'll get some bow lift when you trim it out. Heck, it's only 16 feet long anyway. :eek:

[David]

True more setback could effect planing, but 220 HP on 16 foot? Plenty of power to plane and take the boat to its limit of stability.

Where is Flat Out when we need him?