Hull Speed

[g36]

That's why I posted the link it would give you a starting point and you could compare your actual readings

[Senorjeem]

I would have thought that there was more to this than simply entering your waterline length. Won't beam have a great influence here? Narrower the wedge that you are pushing through the water, the easier, and so the higher the hull speed for a given length???

[tomschauer]

Rick, start slow and creep up the rpm, you have had your boat long enough that you should be able to "feel" when it starts to squat and plow water. When that happens, back off a bit till she is on top again, that would most likely be your most economical hull speed.

[km1125]

Just for grins, I put in the measurement for the old Cort (one of the first 1000' freighters on the Great Lakes)....

comes out to 42MPH hull speed!!!

[tomschauer]

That's one fast freighter!

[RGrew176]

Source of the post Rick, start slow and creep up the rpm, you have had your boat long enough that you should be able to "feel" when it starts to squat and plow water. When that happens, back off a bit till she is on top again, that would most likely be your most economical hull speed.

Great advice. I played with it a bit last year and I am thinking that my hull speed is somewhere between 1400 and 1600 RPM. I do need to spend some more time figuring that out.

[bud37]

Source of the post I would have thought that there was more to this than simply entering your waterline length. Won't beam have a great influence here? Narrower the wedge that you are pushing through the water, the easier, and so the higher the hull speed for a given length???

Good point, there are much more complicated calculations for many different hull designs, but for our boat hulls that calculator posted seems to be pretty darn close, we have planing hulls and are trying to estimate hull speed in a displacement use, as has been said before the hull starts pushing water.

Rick , its amazing how that 1400-1600 rpm shows on different boats I have had......you can really see the tipping point with fuel flow meters on the engines.

[Senorjeem]

Good to know. Thanks

[Ed Schumacher]

Haven't looked at your hull speed formula
but sounds like your using a displacement hull model , planing hulls are a different beast . If your puddling along with your strern dragging half the harbour along with it your burning fuel
. I can drive a 33 foot sailboat under power at 6.5 knts and burn 1.5 litres an hr
because its a very efficiant displacement hull . Your Carver is going to burn less on plane because that's where it's designed to be. still going to burn fuel , its a big heavy boat and there's nothing much less efficient than a large planing power boat.
other than maybe an s71 blackbird or perhaps an M1 tank, cause someone thought a turbine engine was a good idea
to get away from the Russian hordes .
Besides they stuck twin 350s in my 3007 if I was supposed to puddle along at 6 knts, all I would have needed was two yanmar 15 hp diesels . And they could have put another bedroom down there.

[Ed Schumacher]

Haven't looked at your hull speed formula
but sounds like your using a displacement hull model , planing hulls are a different beast . If your puddling along with your strern dragging half the harbour along with it your burning fuel
. I can drive a 33 foot sailboat under power at 6.5 knts and burn 1.5 litres an hr
because its a very efficiant displacement hull . Your Carver is going to burn less on plane because that's where it's designed to be. still going to burn fuel , its a big heavy boat and there's nothing much less efficient than a large planing power boat.
other than maybe an s71 blackbird or perhaps an M1 tank, cause someone thought a turbine engine was a good idea
to get away from the Russian hordes .
Besides they stuck twin 350s in my 3007 if I was supposed to puddle along at 6 knts, all I would have needed was two yanmar 15 hp diesels . And they could have put another bedroom down there.