Originally Posted by Twill
I would like to use a fixed prop. I don't really care about the slight lose of speed under sail. I need more speed under power. I can only get about 4 knots at the moment (5) with a clean bottom (maybe). The prop on my T30 is about 12 inches across. Will a three bladed prop give me another knot
? or not...(ha ha). I do like the idea of smoother ride with the three blades. What is the best way to proceed? Thanks, you guys sure make this fun. I appreciate all the feed back.
A 3 blade
will give you quicker acceleration & stopping/reversing.That is worth a lot in maneuvering.
Hull speed limits your top speed,unless you have more HP than the avg sailboat of similar length. You can push a knot or so beyond hull speed with enough HP,but you pay in fuel
My 28Ft pilothouse motorsailer
has a hull speed of 6.2 kts. The sails
will drive it that fast,with enough wind
So would a 12-15HP diesel
with 2 blade-the standard for 30 ft. sailboats.It would take awhile to reach hull speed,but it would get there.
I have 28HP 2.x reduction & 17D x 14P 3 blade & can reach 7.3kts at W.O.T., & get up there fairly quick.
Lots of squatting & extra fuel
& the engine probably wouldn't last as long.
On the other hand,I can cruise
at hull speed at 60% throttle/RPMs,so fuel consumption
is excellent-1.5 Ltr/hr
It's a trade-off. 3 blades will cut your sailing speed by 1/2 + kts.,but you will be able to accelerate,dock,stop & maneuver with a lot more confidence.
If you go 3 blade,you will have to calculate a new dia. & pitch based on HP & reduction gear
Find a well respected prop shop & google
for info/feedback on your boat model with 3 blade.