So What are you doing to Cut Your Boating Costs

is there a simple formula to calculate hull speed? Though slow it is obviously a very affordable way to motor!!!!!!

 

Take the square root of the waterline length in feet (or sq.rt of 3x the WL length in metres).
Multiply by the speed-length ratio:
-- 0.9 to 1.1 for most efficient displacement speed
-- 1.34 for 'normal' hull speed of an average boat
-- up to 2.0 for hull speed of a very slim hull such as a racing trimaran
Results are in knots if you used feet for LWL.
However, if the hull is a planing type, it will most likely be horrendously inefficient at displacement or semidisplacement speeds compared to a real pure-displacement craft.

 

The amount of fuel costs "saved" will seldome PAY for any modifications.

Recently we changed the 28 inch prop to a 32X32 to bring the engine loading and efficency up , but at $1400 for the prop (Ahoy Marine in LA) and only 200 to 300 hours of annual use it will be a long time!! to break even if we burn 1/2 gph less..

Most folks can just attempt to keep the bottom clean and remember for most boats the fuel cost is MINOR, compared to the rest.

FAST FRED

 

A better option, for a sailing boat, is a propeller like the autoprop, an automatic variable pinch propeller. With one of those you have a better efficiency while motoring (about 1/3 in settled whether) but ,mainly you will have a 50% more efficiency while motorsailing, not to speak of the increased range of the boat. And you will have also a better efficiency while sailing because it is also a folding propeller.