In article
,
Orval Fairbairn wrote:

In article
,
Lou wrote:

I'm building a wood and fabric plane that uses plenty of aluminum
fittings and
hinges. If I have an aluminum block on one side of a spar made of wood
and the aluminum hinge on the other, with a bolt going through, is
there
any reason for washers? It's not that I wouldn't use them, but it
helps when
ordering the correct size bolt. The plans don't mention washers but
the plans
don't call for a few items that seem to me to be necessary.
Lou

Good practice in wood structures calls for a sleeve through the wood
(epoxied into place), slightly shorter than the thickness of the wood,
and large-diameter washers on each side, to distribute the compression
loads from the bolts. It doesn't mater if you have a block or a washer,
as long as there is a means of distributing the loads on the wood.

I forgot to mention sealing the bolt, to protect it and the sleeve from
invading moisture.

Another age-old practice is to dip or brush the bolt with paralketone
(available from Aircraft Spruce, but I did not see it listed). I bought
some from them this year, so I know that they have it. It is a waxy
liquid, like Cosmoline, that evaporates some of the lighter stuff and
never really dries. It will keep moisture out of the bolt, however.

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