Originally Posted by FF
Firts of all any boat cruising at hull speed is very very expensive. Hull Speed is a sailors concept , enough free wind and even a Tahiti Ketch can do it.
Cruising at SL, (the square root of the waterline) is the usual cheap spot,actually .9 to 1,15 times SL, depending on the boat.Light skiney boats do better than fat heavy roomarans.
Cruising at hull speed, SL times 1.34 will cost at least 2x the fuel, and on many boats 3x the SL fuel burn.
On some lighter boats it is actually cheaper to get up on the plane , where wave making resistance drops , and the nautical MPG goes down.
Puttering about at trawler crawler speeds is fine in an old high speed vessel, just forgetabout hull speed, you cant afford it.
I think I understand your point, but I'd say words like "very, very" can cover a very, very
Our hull speed (LWL of about 39') is approx. 8.4 kts, and our nominal fuel burn at ~8.2 kts gives us about 1.7 NMPG. SL is about 6.3 kts, and we get about 2.9 NMPG at ~6.5 kts.
Yes, 1.7 is very, very
bad compared to 2.9. And yes, cruising at SL is relatively cheap (in the grand scheme of "things boat" compared to theoretical hull speed.
OTOH, when we cruise at ~22-23 kts, where the hull is usually most comfortable when were on plane, we're only getting about .7 NMPG.
So there's very, very... and then there's very, very.