On Oct 15, 10:10 am, Frogwatch wrote:
On Oct 15, 3:45 pm, " wrote:

On Oct 15, 6:57 am, Frogwatch wrote:

...Now, one of the advantages of a 2 blade prop is that you can align it
with the keel for lower drag....

Correct me if I am wrong but I believe the S2 8.5 is a fin keel, spade
rudder set-up with the prop just ahead of the rudder. In this case
there will seldom be any drag reduction advantage to aligning the
blades of the prop with the keel.

-- Tom.

why not?

Because, unless the leeway angle is near zero the prop will not be in
the keel's wake. In cases where the prop is right behind the keel or
is in a cut-out in a two bladed prop can be hidden behind the keel or
skeg by aligning it. In your case the prop is a long way from the
keel and even a small amount of leeway will move it into the free
stream and in any case if the keel is well designed and in good
condition the wake two cord lengths back will be insignificant. So,
in your case alignment isn't likely to make a difference you can
measure most of the time. If you are concerned about drag I would
recommend a two bladed geared folding prop.

-- Tom.

On Mon, 15 Oct 2007 21:20:57 -0000, "
wrote:

If you are concerned about drag I would
recommend a two bladed geared folding prop.

The earliest screw propellor equipped ships had props you could raise
out of the water to avoid drag while under sail, which was nearly all
the time.

Casady