Back in my racing days I used a Martec II folding prop. It I remember right
(Martec recommended) it was a 14x12 and replaced a 16x10 2 bladed and worked
ok. It was on a Yanmar 2GM20F. Less power in forward and significantly
less power in reverse. You need to be much more aggressive in reverse when
docking. Lots more walk to port also. Still had to line up the shaft (I
used the keyway since the two were inline) to get it to fold in light air
since the weight of the prop would cause it to open. I have even heard of
folks jumping overboard and putting a rubber band around them to keep it
closed. If it got fouled with growth so it would not open all the way it
would let you know by vibrating when trying to go forward. This is just
some of the things you need to put up with when you race.

I believe it did fold when going from forward to reverse. You could hear it
go "clunk."

With my current cruising boat I would look at feathering props if I were to
upgrade. I need a good reverse and these provide it.

I guess the question is did it help? I would guess so. Could I tell? No
not really.

I agree with JAX. There is quite a bit of stuff you can do to the bottom of
the boat for speed. But bolting on a folding prop is definitely easy. The
other speed improvements require hard work.


"Rosalie B." wrote in message
...
(Shen44) wrote:

Subject: What are the pros and cons of a folding prop?
From: Rosalie B.

We have a feathering prop (vs a folding prop) and we do get an
increase of about 1/2 knot under sail, and it also backs better under
power. I haven't tried to quantify the backing under power - it is
just what we feel.

Disadvantages are - you lose a bit of power forward because the blades
are flat and the prop takes a bit more maintenance than a fixed prop.

[We were sailing but had the engine on in neutral so the prop was not
feathered - we were running the refrigeration- and when we had
finished that, we turned off the engine and feathered the prop, and
our speed increased 1/2 knot - same wind and current. Now I know this
is not a completely scientific test, but it is significant to us.
There are also people in our group who did tests with a fixed prop
over a measured course, and then did the same tests with a folding
prop over the same course and found a similar result.]

Question. Your engine was running but you were in neutral gear. Why wasn't
the
prop feathered? i.e., does the prop "unfeather" when the engine starts or
when
you put it in gear? What causes the prop to feather?
This is an area I'm not familiar with, though I frequently use VP/CP
props.


I don't know what a VP/CP prop is.

When our engine is running the shaft is spinning because we have a
Borg-Warner transmission. Our shaft spins whenever the engine is on
regardless whether it is neutral or not. The prop feathers when the
engine is turned off and the shaft stops spinning. The stopping of
the shaft spinning feathers the prop if I understand it correctly.
You really wouldn't want the prop feathered if the engine was on - if
it feathered when you went through neutral when docking or something
it would be very awkward.



grandma Rosalie