Boat Speed & Prop performance calculators

[Deiter]

Found these while trolling for motor info. Its all aimed at yankee boaters, but some could find it relevent, if not quite bloody interesting. I tried a few calc's with known info from my rig, and was surprised how accurate they were! :o

First one takes a few variables such as rpm and prop pitch to give you an estimate of boat speed.

http://continuouswave.com/cgi-bin/propcalc.pl


This one is a bit more complex and is meant to determine boat speed potential based on a hull's weight, its engine's horsepower, and a hull configuration. I filled in all the fields with known info to get the "hull factor" then played to see what h.p. i would need to get a certain speed. Again interesting, though i make no claim it will be accurate with all vessels, as does the author.

http://continuouswave.com/cgi-bin/crouchcalc.pl

Good luck ;)

Damo

[Chimo]

Hi Damo

I ran both the calcs for my setup and they are damn close to actuals.

The second one was probably right too but I was only estimating total hull weight (which I know) plus included accumulated gear plus liquids plus batteries etc. The 180 factor is probably fine for the type of boat most of us fish out off.

Frightening number of lbs / kgs that I am pushing around and considering the fuel economy I'm getting I'm rather happy.

Should be very useful to those setting up or considering making changes to props, power and the stuff carried in the boat.

Well done.

Cheers

Chimo

[Deiter]

Hey Chimo, you run twins don't you? this might work for cats aswell.
Your 'hull constant' must be a combo of hull and leg drag aswell, for the extra g'box.

Would be interesting to see what a single on a similar hull with similar combined h.p. would work out to.

Damo

[Chimo]

Damo

Possibly

I used the 180 factor as it seemed to fit more closely to the hull type ie Seafarer Vagabond

Don't know about cats. Are they not supposed to be more slippery?

Really not sure but if guys on the site fed their numbers in with real experience it should be possible to fine tune the hull constant as thats the only unknown.

The first formulae was very close to my actuals even with twins.

Cheers
Chimo

[RayB]

I think the first calculator seems quite accurate. Haven't tried the second one.

cheers
Ray