Thom Stewart wrote:

OK Group,

What happened to the original statement; "Useless propeller" Let's get
back to that! Why is a Two Blade Folding Prop a Useless propeller and a
Four Blade fixed going to work better in rough, choppy sea?


Well, a two-blade folder isn't really useless, it has it's
own uses and unfortunately that means it will not do as good
a job driving the boat under less-optimal conditions. OTOH
it will allow the boat to sail much better.

The problem with most folding props is
1- they are expensive, leading most people to buy the size
smaller than they really need
2- the hubs often develop some play, allowing the blades to
twist unfavorably and lose power

These two things are why they don't work well in reverse and
don't work well in choppy water.

I have a little experience with the Luke three blade
feathering prop, which is expensive but a very practical
alternative.

A good friend of mine had a small keelboat with a big
2-blade folder... the boat was very slow under power. This
was the opposite case of above, the previous owner had gone
for "conspicuous consumption" and outfitted the boat very
expensively but not efficiently. Among other things, the
prop was pitched for much higher RPM. When we were motoring
out to a race one time, we discussed the issue and since
thenengine reached full RPM easily, there was no reason not
to adjust the pitch. After two successive adjustments the
boat went almost 2 knots faster under power. It also motored
quite well in rough water... certainly much better than the
same type boat with an outboard.

Fresh Breezes- Doug King