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Re: Canard Alignment

  When I made the discovery I added a pad of triax to the front of the
canard bulkhead. It ended up about 1/4 " thick and I tapered it to match the
canard tab. I used some microglass on the pad to get a good seat for the
tab. (Glad Wrap the tab). The other side will need to be built up slightly
as well to compensate for the angle. Scott very kindly made me an overlength
bushing for the pilot side that went all the way through. I would not use
washers as you suggest. They would slide past eachother so the bolt would be
unsupported in the area of the washers. The strength of the joint comes from
shear between the tab and the bushing/bulkhead.
  My canard tabs were short enough that the bushings ended up 3/8" from the
top of the bulkhead. Didn't seem like enough depth (plywood) to withstand
12g's, at least from what I could calculate. Scott said Wim Huisman made
straps that brought the loads lower into the bulkhead. I made some that put
the canard tabs into double shear and brought the attach points down to the
center of the bulkhead doubler. Double shear evens the forces on the bolt
and tab so that the tendency for each to bend is eliminated. I still use the
bushings but these straps go front and rear of the bulkhead so the bulkhead
is also in double shear at the strap attach points. The straps should be
able to handle the strain by themselves. Maybe overkill but I feel better
about it.   -Bill
-----Original Message-----
From: Brian K. Michalk <michalk@awpi.com>
To: asterisk@idsonline.com <asterisk@idsonline.com>
Cc: reflector@sisko.awpi.com <reflector@sisko.awpi.com>
Date: Tuesday, April 28, 1998 10:20 AM
Subject: Re: Canard Alignment

>> That dimension sounds about right.
>> When I discovered my asymmetry, I chose to make the canard wingtip to
>> distance equal on both sides. I doubt it really matters, though. Rather
>> using washers, I added thickness to the bushing and added additional
>> thickness for support. Of course, that was in the days when the whole
>> bulkhead was made of plywood anyway.
>Okay.  I've taken the same measurements as you then.  I'm concerned
>about a torque through the lift tab bushing.  If the lift tab
>is spaced four washers away from the lift bearing bushing, is
>that okay?  The last thing I want is to rip out that bushing
>in turbulence.
>I could lay up a pad of triax with some webbing down the front side
>of the CB that would be in tension.  This should arrest the torque
>that I'm concerned about.
>Do you think it's necessary?  I could do it, but if all it's going
>to do is add weight, then I'd rather not.  Of course there is the
>peace of mind factor.
>Brian Michalk  <http://www.awpi.com/michalk>
>Life is what you make of it ... never wish you had done something.
>Aviator, experimental aircraft builder, motorcyclist, SCUBA diver
>musician, home-brewer, entrepenuer and SINGLE!