Post by markgraham on Feb 12, 2018 0:43:36 GMT -6
Hello,
Presently, we are working our way against the trades in the DR now and so having to motor extensively for the first time since we got the boat. We are grossly overloaded.. we are sitting about 4 inches low and we have a dinghy tied on the foredeck. With a 71HP engine at 2500 RPM, I only get 6 knots in nil wind. This seems about 20 % low to me. I have worked through the arithmetic in Dave Gerrs book on propellers and the estimated HP at the prop at 2500 RPM should have given me hull speed of 8.2 knots. Clearly that's in the mythical perfect world and will never happen in real life. But surely 7+ knots should not be an unreasonable expectation? Bottom is clean, prop is clean and Maxprop blade angle is set slightly coarse to produce about 8% less than max rated RPM at WOT.
Thanks
For More Details:-
Workforce Analytics Video
Presently, we are working our way against the trades in the DR now and so having to motor extensively for the first time since we got the boat. We are grossly overloaded.. we are sitting about 4 inches low and we have a dinghy tied on the foredeck. With a 71HP engine at 2500 RPM, I only get 6 knots in nil wind. This seems about 20 % low to me. I have worked through the arithmetic in Dave Gerrs book on propellers and the estimated HP at the prop at 2500 RPM should have given me hull speed of 8.2 knots. Clearly that's in the mythical perfect world and will never happen in real life. But surely 7+ knots should not be an unreasonable expectation? Bottom is clean, prop is clean and Maxprop blade angle is set slightly coarse to produce about 8% less than max rated RPM at WOT.
Thanks
For More Details:-
Workforce Analytics Video