oil-canning

[Mike Davis]

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To: murphy-rebel@dcsol.com
From: piquette@golden.net
Subject: oil-canning

Upon inspection of the SR2500 at the Toronto Air Show we noticed that the
elevator, rudder and vertical stabilizer had some "raised indentations"
formed in the skin between the ribs. Our kit (003SR) does not have this
type of skin. Why would the prototype have this type of skin and not our
kit? Any suggestions? Our concern is oil-canning upon completion.

Peter Kopasovic & Monica Piquette
SR2500 003




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[Mike Davis]

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Date: Wed, 20 May 1998 12:18:59 +0000
From: David Ricker <ricker@dbis.ns.ca>
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To: " (Murphy Rebel)" <murphy-rebel@dcsol.com>
Subject: Re: oil-canning
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Hi Folks

We don't have a SR but we have (what we believe to be) an early Elite,
#583, which is supposed to be built much like the SR. Our rudder has
the creases you mention but the El and Stab. don't.

The reason you see these on the prototype SR is that they may have been
experimenting with them to determine if they were required. Of course,
it would be less expensive to manufacture without the creases so they
may not have made it onto the production parts. On the other hand, we
have found some descrepancies (undocumented at Murphy due to unfortunate
circumstances at key moments etc.) in our parts compared to the present
production issue because they were early production parts. We have been
able to overcome these descrepancies but they have caused some head
scratching.

Do you need the creases? well, Murphy should have the final say on that
as official designer but on our Elite, we have found that if we are
careful to not spread the skins (widening the angle of the bend at the
trailing edge, you get a nice smooth and apparently robust part that
probably won't oil can. Keeping the angle tight is most important as if
you don't, the skin will be pulled into "dimples" at the ribs and you
will get oil canning.

Hope this answers your questions.

Dave R.



piquette@golden.net wrote:

Upon inspection of the SR2500 at the Toronto Air Show we noticed that the
elevator, rudder and vertical stabilizer had some "raised indentations"
formed in the skin between the ribs. Our kit (003SR) does not have this
type of skin. Why would the prototype have this type of skin and not our
kit? Any suggestions? Our concern is oil-canning upon completion.

Peter Kopasovic & Monica Piquette
SR2500 003

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