The Murphy Builders Site

Although still interested in the Prince prop I'm beginning to consider
that I may be better off buying used metal prop right now. I know of a
Sensenich for sale that does not meet certified standards in width (
slightly below Sensenich recommended specs). I wonder how important
that is? I've heard that many home builders buy these out of spec props
without any concern. Are these props safe to use?

Clay



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Clay.....they usually come off someones Cherokee etc because the IP/AI/AME
pulled it for a 5 year corrosion inspection and during so it gets measured
and found undersize OR the overzelous overhauler grinds it just enough to
say it's below limits so they can sell them a new propellor. Considering it
was flying before hand at these dimensions, and quite possibly for over 4
years.. there is nothing really wrong wiht putting one of these on a
Homebuilt unless you are suspect if it's been a prop strike and
restraightened by someone that didn't know what they were doing.

Biggest thing is check that the length is actually what it is supposed to
be...IE; 74DM-0-XX should be within an 1/8 or so of 74" in length. a
74DM-2-xx is factory shortened to be 72" etc. Just make sure you don't get
something that someone used a hack saw to take 2 " or more off of!!

Cheers,
Wayne

----- Original Message -----
From: "Clay Smith" <cbsmith@nf.sympatico.ca>
To: <rebel-builders@dcsol.com>
Sent: Friday, September 17, 2004 6:46 PM
Subject: Non-certified Metal Prop

Although still interested in the Prince prop I'm beginning to consider
that I may be better off buying used metal prop right now. I know of a
Sensenich for sale that does not meet certified standards in width

slightly below Sensenich recommended specs). I wonder how important
that is? I've heard that many home builders buy these out of spec props
without any concern. Are these props safe to use?

Clay



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I think it's Sensenich that has a good article on metal props on their
site that will make anyone think twice before using an out of spec metal
prop. Recall that all aluminum props fatigue even on a certified metal
prop/engine combination. The approved combination and spec means that
the fatigue will not be excessively fast. Out of spec is essentially
russian rulette... It will break you just don't know how soon.

There was an interesting article in Contact magazine (alternate engine
magazine) that denigrated the theory behind bent tip props. Essentially
claimed that bent tips (and wide prop tips) wasted large amounts of
power. The gentleman demonstrated impressive efficiency with thin
narrow tips as another way of reducing tip drag. Probably part of the
explanation for the good performance of tapered tip Warp props.

Ken

Clay Smith wrote:

Although still interested in the Prince prop I'm beginning to consider
that I may be better off buying used metal prop right now. I know of a
Sensenich for sale that does not meet certified standards in width (
slightly below Sensenich recommended specs). I wonder how important
that is? I've heard that many home builders buy these out of spec props
without any concern. Are these props safe to use?

Clay

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