Hey group,
My original equipment propeller for my 25 hp Johnson is beginning to show
wear and its that time that I should look into a replacement or spare prop.
Has anyone had any experience with Comprop (www.comprop.com) for small motor
applications? They advertise similar performance and durability of a typical
aluminum prop but with 4 blades. I like the idea of a four bladed propeller
for the low end performance. I'm not a speed freak but like to load the boat
to its maximum limit on occasion.

What is this groups opinions? I see they are relatively inexpensive in cost,
are they cheap? If not recommended, where near Crystal River, Ocala, or
Tampa or even on the internet is a discount prop resource?

Thanks for any assistance.

Halon

On Sun, 26 Oct 2003 21:26:14 GMT, "Ken" wrote:


What is this groups opinions? I see they are relatively inexpensive in cost,
are they cheap? If not recommended, where near Crystal River, Ocala, or
Tampa or even on the internet is a discount prop resource?


As far as I know about props, which isn't very far, the fewer blades
it has, the more efficient it is. That is, the perfect prop has 2
blades. More blades are usually used to get the same blade area to fit
into a smaller diameter for practical considerations. My free advice,
which is worth every penny, is to stick with a three-blade.

-m

On Sun, 26 Oct 2003 23:37:22 -0500, "sour (max camirand)"
wrote:

On Sun, 26 Oct 2003 21:26:14 GMT, "Ken" wrote:


What is this groups opinions? I see they are relatively inexpensive in cost,
are they cheap? If not recommended, where near Crystal River, Ocala, or
Tampa or even on the internet is a discount prop resource?


As far as I know about props, which isn't very far, the fewer blades
it has, the more efficient it is. That is, the perfect prop has 2
blades. More blades are usually used to get the same blade area to fit
into a smaller diameter for practical considerations. My free advice,
which is worth every penny, is to stick with a three-blade.

Actually, Dave Gerr claims a one-bladed prop would be even better, if
you could only solve that pesky vibration problem.

- Rick Tyler

--
"Ignorant voracity -- a wingless vulture -- can soar only into the
depths of ignominy." Patrick O'Brian

If you want a composite prop that gives you a little insurance for when you
hit something, why not take a look at Piranha props. I've got a friend that
uses them and swears by them. If you damage a blade, you just spin off the
cap, slide the bad blade out and a new one on, then spin the cap back on.
About as easy as an in-boat prop repair will ever get. And extra set of
blades can be stored flat, in a Ziploc bag. Piranhas cost about the same as
a regular aluminum prop. Note that most composite props lose efficiency
because they tend to flex, and Piranhas are no different, although they are
very stiff and the lost efficiency seems to be academic. My buddy's boat
gets great mileage and pops up on plane in an instant. Note: NO affiliation
with any prop makers or sellers. My friend has been pretty happy with his
prop and with Piranha and talks about them all the time. See
http://www.piranha.com/ . They are very helpful in prop selection and will
even let you try different diameters and pitches until you're convinced the
prop works as you desire ...just send back the blades that you tried and
didn't want.

Brian

--
My boat project: http://www.advantagecomposites.com/tongass


"sour (max camirand)" wrote in message
...
On Sun, 26 Oct 2003 21:26:14 GMT, "Ken" wrote:


What is this groups opinions? I see they are relatively inexpensive in
cost,
are they cheap? If not recommended, where near Crystal River, Ocala, or
Tampa or even on the internet is a discount prop resource?


As far as I know about props, which isn't very far, the fewer blades
it has, the more efficient it is. That is, the perfect prop has 2
blades. More blades are usually used to get the same blade area to fit
into a smaller diameter for practical considerations. My free advice,
which is worth every penny, is to stick with a three-blade.

-m

On Mon, 27 Oct 2003 05:44:36 GMT, Rick Tyler
wrote:



Actually, Dave Gerr claims a one-bladed prop would be even better, if
you could only solve that pesky vibration problem.

- Rick Tyler

Hehe
I read that too, and I reckon he's right. If I had to take a wild
guess, I'd say the reason this composite prop is using 4 blades is
because it allows for shorter blades and therefore less flex.

-m

There's an airplane motor with a one-blade propeller on it in Portland,
Oregon at a museum. The propeller and motor are from a real airplane that
flew, and apparently it the one blade prop is the most efficient for
aircraft too. On the side where the second blade should've gone, there was
a short stub that acted as a counterweight. The prop ran smoothly and had
zero problems, but never sold well because people just didn't feel
comfortable with the idea.

I'd almost bet that something along the same lines has been used for boats,
and I'll be there's more to it besides counterbalancing. No matter what
though, even if efficient, the one bladed prop will put a side load on the
bearing because the forward thrust creates leverage from one side only.

Brian


"sour (max camirand)" wrote in message
...
On Mon, 27 Oct 2003 05:44:36 GMT, Rick Tyler
wrote:



Actually, Dave Gerr claims a one-bladed prop would be even better, if
you could only solve that pesky vibration problem.

- Rick Tyler

Hehe
I read that too, and I reckon he's right. If I had to take a wild
guess, I'd say the reason this composite prop is using 4 blades is
because it allows for shorter blades and therefore less flex.

-m

I don't know if they still do but back in the 50's and 60's they used
one blade props on model airplanes for speed records. The prop was
balanced with a metal counter weight. I think I remember seeing them on
high speeds boats too. Isn't a two bladed surface piercing prop
essentially only one blade in the water to reduce drag?

Regards, Ron

Another option for composite props is ProPulse (www.propulse.se). This are a
Swedish product apparently being sold through West Marine in the US.

Regards,

Don MacPherson
HydroComp, Inc.