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Old 03 January 2005, 16:10   #1
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Composite Props

Firstly , as a new member, may I say hello to forum members. Over the Holiday period I have spent several hours looking at current and past threads finding a lot of them to be of interest and also some quite amusing.
A bit of advice though, or perhaps the benefit of others experience. After destroying an aluminium prop to about 10% of it's normal blade length and just managing to creep back to terra firma, I needed a replacement quickly to continue my holiday boating fun. A like for like replacement was not available 'off the shelf' and I pondered for some time before purchasing a composite, adjustable pitch prop. I viewed it as a temporary use prop, though the vendor assured me that lots of people now use them permanently. I must admit the performance seemed no different, maybe even better. I'm now unsure whether to go back to an ally prop and keep this one as a spare, or continue with the composite. On first thoughts the idea of a plastic prop didn't seem right, but then lots of products made today are plastic rather than metal. Another thought is whether the replaceable composite blades would shear off flush and leave less chance of getting back to base. I know it would be sensible to carry spare blades, but then you've still got to fix 'em in a possibly dodgy situation. I am hoping I will learn the pros and cons through this forum, to enable me to arrive at a more calculated decision.

Thanks,
Chris Martin
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Old 03 January 2005, 19:36   #2
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Thanks for the info Chris - have lthought about these myself - it is mainly the variable pitch that interests me - though wether or not suitable for 225hp don't know!

As to composites being suitable as you said loads of things going down that road now - including helicopter rotor blades and plane props.
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Old 03 January 2005, 19:52   #3
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spare props

you must be running a different prop as the normal one supplied with engine as that one is a very popular size and carried by most dealers.

As for non metal ones, would be nice to know what hp they will take and what sort of price difference to bog standard alloy ones.
Paul
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Old 03 January 2005, 19:54   #4
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Hi Chris,

Interesting to hear your experience with the composite prop. I must warn you that you are now the RIBnet composite prop expert - I hope that is not too daunting a prospect after your first post!

We have carried a spare composite prop since we've had the current boat, but never used it - perhaps after your positive comments we'll give it a go, although we do carry a spare stainless steel prop anyway.

Codders/Paul F - our Piranha is supposed to be suitable for up to 260hp (their website now says up to 280hp). See www.piranha.com But if you're interested in a variable pitch, you should ask jwalker about his Torqueshift which sounds very impressive - he may still have it for sale!

Welcome, Chris!
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Old 03 January 2005, 21:51   #5
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Quote:
Originally Posted by Richard B
We have carried a spare composite prop since we've had the current boat, but never used it - perhaps after your positive comments we'll give it a go, although we do carry a spare stainless steel prop anyway.

Codders/Paul F - our Piranha is supposed to be suitable for up to 260hp (their website now says up to 280hp). See www.piranha.com But if you're interested in a variable pitch, you should ask jwalker about his Torqueshift which sounds very impressive - he may still have it for sale!

Welcome, Chris!
You actually HAVE one and haven't used it!!!! Come on - just not good enough - we need ALL the details we can get!!!!
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Old 04 January 2005, 01:19   #6
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Sorry! I'm not sure if it's got the correct hub splines for our motor!
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Old 04 January 2005, 05:13   #7
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I've been using a variable pitch composite four blade prop fitted to my Suzuki Df140 18 thru 22 pitch is available manually adjustable and can be done with the prop still fitted on the engine.

Carry the Ali prop as a spare

See http://www.propulse.se/ for the one I am using
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Old 04 January 2005, 05:17   #8
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Regarding plastic props...
I also do alot of boating with Kent Scouts. We operate off a shingle beach that has a lot of shallow bits with lots of different helms and some are more careful than others...
We were getting through a few props in a year so decided to try the Piranha range. Performance was virtually unchanged, although we were only running on a 30hp yam 2str and not too intersted in flat out speed. We chucked a spanner and a few spare blades into the safety box and waited with baited breath.
When you wrap a rope it would seem to survive ok, but I would guess most rope wraps are at low rpm. But come into a hard sand or shingle beach, even at tick over and twang there goes another blade. They would shear off at the narrowest part, which is right down at the hub, and would not leave anything to get you home. I dont remember ever seeing all 3 blades gone, but I suppose it would be easy to trash 3 blades.
The cost of blades against a new prop is gonna be a long debate, but it seem to boil down too how often do you ever touch bottom- the hard type! An ally prop will suffer from a grounding but would normally get you home, and can generally tolerate much more abuse. A plastic prop gives up alot easier.
After a season we went back to ally props. It seems to work better for us for where we are and what we do.
Last year I ran aground once in my own boat. I was a safety boat for a large Scout event where we had 100 kids afloat, when a squall blew through. We initiated an 'all in' rescue and everyone was recovered quickly. We were in about 2-3 metres of water before the squall but a 1 metre chop meant we started clipping the bottom. Every single boat dinged a prop to some extent. In this case had I a plastic prop I would have been severlly hampered or even disabled. As it was all I did was bend two blades, one through the middle of the cup! This was easily straightened out as it wasnt chewed.

So if you have a soft bottom and dont touch it, the plastic option may work for you.
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Old 04 January 2005, 05:37   #9
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Quote:
Originally Posted by Richard B
Sorry! I'm not sure if it's got the correct hub splines for our motor!
Not a great deal of point in carrying it then
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Old 04 January 2005, 14:20   #10
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Sorry, my post might have been slightly misread. I was not offering advice or experience, as Richard B may have thought, regarding composite props but rather asking for any advice or thoughts on these props. Hence let's make it clear that I am no expert on the subject!
Sounds like 'Swifty' might have confirmed my suspicions that on impact you can lose too much of the composite prop to be able to limp home.
Although I think the prop on my engine is pretty common in size, it was not easy to find a stockist in the Pembroke area of Wales. Maybe others had already obliterated their props and beaten me to the parts counters in the area.
Perhaps the answer is to carry an ally prop as well. Just in case.

Chris Martin
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