Are washers necessary?

In article ,
cavelamb himself wrote:

Orval Fairbairn wrote:
In article
,
Lou wrote:


On Aug 13, 11:03 pm, Orval Fairbairn
wrote:

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.


I hate to show my ignorance, but it won't be the first time,
What would you seal the bolt and sleeve with?
Silicone?
Lou


No -- you seal the sleeve to the wood with epoxy (I would use T-88); the
paralketone seals the bolt. Actually, I would also use some zinc
chromate past around both ends of the bolt, too.

If no moisture gets in, the wood will not rot, nor will the bolt corrode.


Next question is - what to make the sleeve from.

Aluminum could possibly set up a coorosion problem.

I would suggest steel tube - cleaned and dipped in a 2 part primer like
RandoPlate or EpiBond.

Then, you are gluing to the primer (which works well) rather than the
steel surface.

4130 tubing, reamed to the correct ID. Try some gun blue on to and epoxy
it in place.

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