Martec Slipstream Stainless Folding Propellor

[David Sanner]

Just wondering if anyone has a Martec Slipstream all
stainless folder on their boat?

If so how does it perform and what pitch did you select.

For those not familiar with the prop it is a geared folder
(2 or 3 blade, I'm looking at the 2 blade) that is all
stainless so it wears better and has less issues with
electrolysis.  It's also, supposedly, has an improved
blade shape compared to the other martec folders.

I'm comparing this prop to the kiwi prop. 

If you don't have this prop but have another large
bladed 2 blade prop what pitch did you select?

I currently have a 15x9 3 bladed fixed prop with my
M25XP.  I figure it could handle at least another degree
of pitch so I'm wondering how a 15x10 translates to a
2 blade folder...  11 pitch or more.

[George Pyrpiris]

Go with the Kiwi, much better when motoring vs a 2 blade (cavitation!!!!), vibration was reduced to almost zero due to the weight being kept away from outer ends of the prop.  Under sail it's as good as anything out there, transformed our boat into a fast boat that can sail with almost anything out there until the wind gets to 18+, then the 49 footers do catch us.  It's made of 316 stainless which is as noble as stainless gets.  Just can't say enough about the Kiwi prop.  It changed the boat completely!!!  Beware the 2 blade props THEY CAVITATE TO THE POINT OF WANTING TO RIP THEM OFF YOUR BOAT AND THROW THEM AWAY!  Also, a friend has a 3 blade martec and has severe prop walk in reverse.
My comments are founded on having experienced 2 blade props....never again.  I can't believe manufacturers put these things on sailboats.
George

[lazybone]

If your primary concern is racing I would opt for the lower drag two blade, but if your doing mostly cruising I would think a three blade with its extra punch would be the proper choice.

[Steve Sayian]

Dave,

I put a Kiwi on this spring.  Immediately noticed a VAST improvement when sailing!  Last year I had the Michigan 3-blade fixed prop.  The boat would not 'ghost' in light winds under 8 knots.  This year, with 6 knot winds we were doing 2.9 knots (main and 135 jib)!  It feathers great and is easy to adjust under water.  It also weighs the same as the bronze 3-blade where most feathering props weigh quite a bit more.  Highly recommend it both in performance and cost!

Steve

[David Sanner]

Thanks for the responses.

I will be racing the boat, which is one reason I'm getting a folder though I'm looking for all around sailing improvements (one of the easiest ways to get a 10-20% sailing performance increase!) including under power as a 9" pitch is a bit low.

Kiwi Prop:
        Pros: power in a seaway, pitch adjustable. 
        Cons: slightly more drag than a folder, flat blades not as efficient

Stainless Martec Folder:
          Pros: very low drag, efficient on flat water.
          Cons: not as powerful, not pitch adjustable.

Now it's just a level of degrees...  does the large hub and base thickness of the kiwi blades significantly increase drag when sailing (race mode) compared to a folder?  Also, how inefficient are the kiwi blades under power?  Being able to perfectly adjust the pitch for the boat/motor probably makes the kiwi efficiencies a non-issue but I haven't seen and numbers or direct comparisons.  Kiwi says less drag than a max-prop, more than a folder.
I've seen this approx drag: 40lbs 3blade fixed, 7lbs max-prop, 4lbs folder.  So... non-issue?

My first choice was the Kiwi but I'm wondering if anyone has used the newer all stainless Martec props as they've received some good reviews for use under power... some say their large and 'updated' blade design provide similar performance to a three blade sailor.

Since both use stainless neither require zincs and the Martec wears much better
than the brass folders that have been available.... basically no/low maintenance as
the gears are stainless & the bushings are user replaceable (ever 5-10 years).
The Kiwi requires some cleaning a greasing but minimal as well.

If I was going to only be cruising the obvious answer would be a Kiwi but
the new Martec with it's efficient all stainless blade design looks good
to me as well... especially from a racer's perspective.

http://www.seahawk.com.au/content/folding.php?menu=products
http://www.martec-props.com/info_Slipstream.htm

[John Langford]

I have a kiwi prop which has transformed my light air sailing. One comment on the conversation so far, I believe the prop is quite a bit lighter than a traditional Michigan wheel. After all, the blades weigh practically nothing and the hub is half composite and half stainless steel. There is certainly no clunking or shaking - both of which seem to be standard features when you have a heavy Max or Auto prop.

A friend has the Slipstream 2 blade on a C and C 99sail drive. The boat sails incredibly well and I can only keep up on a broad reach. It also motors very well (no reports of cavitation) and appears to back beautifully. On the other had, when it comes to backing I doubt that anything can compare to the Kiwi. The backing power is amazing.