On Oct 16, 4:29 am, "Dennis Pogson"
wrote:
Frogwatch wrote:
Anybody have experience with these? I am about to replace my fixed 3
bladed prop on my 8.5M S2. This looks like a potentially good
candidate replacement because they have already figured out which prop
works for a given boat and because they say they can put a larger prop
on with their "Extendo" system.
I am a little worried about the plastic of this prop not being able to
take my aggressive barnacle removal method. Is it easy enough to
remove that re-painting it every so-often works?
My old bronze prop has succumbed to corrosion and many impacts with
oyster beds and with a Laser mast in the water.

Now, one of the advantages of a 2 blade prop is that you can align it
with the keel for lower drag. How does one do this? Do you simply
mark the prop shaft inside the boat and then rotate it till your mark
is in the right place? This really seems like a PITA considering the
gawdawful engine installation on most boats. Even on my boat it
requires removing an engine panel and peering down into a dark space.
Is there any other system? Would the prop left in neutral auto-rotate
to the lowest drag position (I have never had a two blade prop so I
dont know) and stay?
Could I attach a magnet to the shaft so that it engages a magnetic
reed switch (non-contact) to tell me when it is in correct position?
Can you get it in correct position by "bumping" the start switch?

Ever heard of a thing called paint? You can even mark a prop shaft with it.
I won't charge for this piece of wisdom as I learned it about fifty years
ago. (and the piant is still there!) You could easily fit a small glass
spyhole in the cockpit floor. However, some sailors would argue that
allowing the shaft to rotate in neutral causes less drag than locking it in
the upright position, particularly on a modern fin/skeg design.

Dennis.

Dennis.

My primary motivations for being interested in CDI is that I hear so
many stories of ppl who get new props and they just are not right and
thye just live with it due to the cost of hauling to change them. CDI
seems to have gotten it right and their props are supposed to be easy
to change if not. They can be changed in the water .
Another reason for considering a two blade instead of simply replacing
my existing 3 blade is that I have been in a few races lately on
other boats and I might want to do club races in mine.

On 2007-10-16 11:15:38 -0400, Frogwatch said:

Another reason for considering a two blade instead of simply replacing
my existing 3 blade is that I have been in a few races lately on other
boats and I might want to do club races in mine.

The 2-blade will probably be considerably less drag as I recall the CDI
blades being fairly high-aspect compared to the older 3-blade props.
They can afford to be because of the improved foil shape.

If you club race, you'll get a few seconds allowance for NOT having a
folding/feathering prop, but more important, in normal sailing, you'll
find yourself being able to sail in lighter air than you're used to.

We went from 2 blades to feathering 3-blade (to get rid of a harmonic
vibration) and move in amazingly light air. The only justification I
could give for getting that expen$ive prop was to amortize it over the
number of years we expected to have the boat, but it's proven to be
worth the investment -- to me.

--
Jere Lull
Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/