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Date: Sat, 01 Sep 2001 15:37:49 -0400
From: John Schroeder <jschroeder@perigee.net>
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Reply-To: lancair.list@olsusa.com
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To: lancair.list@olsusa.com
Subject: Re: Aileron counterweights
References: <3B90EFF8.5E454F14@tin.it>
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          <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>>
          <<  Lancair Builders' Mail List  >>
          <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> 
>>
John -
After much frustration of pounding lead, we concluded that
casting would be the best way to go and that a trapezoid
shape might be good. We used a piece of angle iron and
pushed that into wet bondo. After taking the piece of steel
out, we then filled the apex of the V with some very thin
bondo and, scraped the excess to the width of a tongue
depressor. The mold is 9 inches long, so we can easily cast
a weight with no voids. Three weights fit nicely on the
inboard section of the flange and one on the outboard
section. The weight to slightly overbalance balance the left
aileron (trim tabbed) is about 2880 grams and each weight
protrudes about 1/2" from the leading edge of the flange. To
get the correct up movement (down in the jigged left wing)
of the aileron, we had to trim back the flange to 1.5" on
the inboard end and .75" on the outboard end.

It appears that we are now in the ballpark for a solution,
but the trapezoidal shape may be wrong. It is too thick and
we can't get the required down aileron (up on the jigged
left wing).

A couple of questions:

How does plaster of paris hold up to the heat of the lead?

Does it interact or distort?

How thick are the walls of the mold? The bondo is OK,
especially the thin stuff (Thin Ice), but it gases a bit,
which may be toxic, is expensive and sets a bit too fast.

What shape did you use for your wood mockup?

How far beyond the leading edge of the flange did you extend
the weight?

2880 grams of lead is a lot (6.64#)

Did you flox the weights on then put BID over them (ES
manual calls for this). Walter Dodson used a trapezoidal
shape, bonded them with Hysol and screws and no BID on his
IV.

Many thanks in advance,

John



"John F. Herminghaus" wrote:
 >>
> I made a wood mockup of the weights, made plaster mold of the model and
> then lead castings.  So doing I was able to maximize the use of the
<SNIP>
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