Speed under engine?

[mick]

My Sadler 26 can reach hull speed under engine with a calm sea. Straight into a chop in strong winds I get half of that, and sometimes less. How does that compare to others' experience?

 

[rob2]

Sounds good to me. You have a pretty low drag hull, so the windage is probably more significant than any other influence and a chop can stop any boat dead... In fact, I suspect that you would hardly notice much difference under the more trying conditions until you had more than twenty horses at your command and, of course, a whacking great prop to transmit the power. Then you wouldn't be able to sail in anything less than Force 4!

 

[oldharry]

Depends on engine size, and how well matched the prop is. Under 12 - 15hp what you get is probably normal. If you have 20 - 30hp under the steps, then prop size needs checking.

 

[Evadne]

It all depends on the propeller and the horsepower.

For comparison, I have about 2hp per ton and a small diameter 2-bladed prop., and I get exactly what you say you do. I expect no more, although I know a 3-bladed prop. would provide more oomph in adverse wind and sea. It only takes a couple of horsepower to push your boat at hull speed in no sea.

I suspect you will have about 4-6hp per ton, typical for a more modern boat, but not as much as today's yachts, some of which would have been classed as motor sailors in the 60's. The more extreme of these will be able to go faster under power than they can under sail, in either light or strong winds.

The Sadler is a nice looking boat, the smug answer is that if you want to go faster under power you may have to get an uglier boat, or try sailing instead.
/forums/images/graemlins/wink.gif

 

[boatmike]

I agree generally with what others have said but it depends very much on the propeller pitch. A propeller with course pitch may do extremely well in favourable conditions but start to overload under adverse conditions that requires more power to drive it. Slightly dropping the pitch might affect your "favourable" performance but increase performance under "adverse" conditions. Its a common failing to choose a prop thats too course and not meet max RPM in adverse conditions. If you have a 50% reduction in speed under these conditions my guess is you are over pitched.

 

[johnalison]

And the prop needs to be clean. I'm nearly 3/4 knots down at this end of the year.

 

[morgandlm]

I have a Sadler 26 with a Bukh 10hp diesel and a two bladed prop. My experience is pretty much the same as yours. I also totally agree with the comment about keeping the prop clean. The performance drops off sharply if the prop starts to foul up.
Morgan

 

[SvenglishTommy]

Sounds very good to me, I never get more than 4.5knots in my 28'er under engine, strong winds into a chop and I get about 1-2 knots.

 

[Victorious]

Would you want to bash onto a rough chop at 5 knots?
It aint no fun and I suspect you would soon ease off the power if you had it available.

 

[mick]

Thanks, all.

 

[Spyro]

Very similar story, I notice it's the chop or waves that kill my speed most.