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Re: Canard Alignment

 Carl- I would caution you about the washer setup you described. First, the
ID of a washer is larger than the bolt it's used with. That means that if
it's in contact at all it will be in a relatively small area rather than
evenly distributed. Washers are stamped, not bored and they're rough on the
inside. This further reduces contact area and can damage the bolt. I had
epoxied the wing attach washers in the strake and found that they could nick
the bolts. This is just from installation, no flight loads! A nick
concentrates stress and makes failure more likely, possibly at lower loads.
I reinstalled the strake washers, being careful to center them on the
bushing so they don't come in contact with the bolt shaft, only the head.
  In your case the washers are right in the area where the bolt is under the
most stress. The best solution is to have a continuous bushing the whole
depth of the bulkhead and any shimming pad. Maybe you could get one from
Velocity as I did. The canard tab acts in shear against the bushing and you
need to get that load transferred to the bulkhead. If the end closest to the
tab is inadequately supported it will have a certain amount of leverage
which would tend to wiggle the bushing from the bulkhead. It might not be
critcal in this situation but I don't like it. Bushings can be removed by
applying heat until the epoxy softens- I had to do it several times as the
Main Gear bolt sizes increased with resulting retrofits. Be careful not to
overheat the surrounding glass.
  The canard tab is a somewhat different situation from a prop. The canard's
lift pulls the tab perpendicularly against the shaft and acts to cut through
it using the bushing as an anvil, like scissors. You need proper tension to
keep the pieces from fretting against eachother, but at the same time be
sure not to overtension which can stretch the bolt and lead to failure. A
prop bolt is in tension to keep the prop from fretting against the crank
flange and to pull the plane (if it's a puller installation), but it's also
in shear. Shear on the bolts and prop/flange interface is what makes the
prop turn.  -Bill
-----Original Message-----
From: Carl Hoffman <hoffman3@erols.com>
To: Brian K. Michalk <michalk@awpi.com>
Cc: reflector@awpi.com <reflector@awpi.com>
Date: Wednesday, April 29, 1998 8:32 AM
Subject: Re: Canard Alignment

>I to discovered the need for 4 washers, after lining up the canard
>equidistant to the strake. (The canard bulkhead was lined up to the
>nose.) I just put milled fibers around the washer, tapering to the
>forward side of the bulhead. Covered both forward sides with 1 fine BID.
>The fuseloge is banana shaped and also requires that you center the keel
>with respect to the sides of the fuseloge not the center of the
>As for the concern about ripping the bushing in turbulence, I believe
>the tapered fibers are going to be just as strong. Also I remember
>reading on the reflector concering prop bolts. You want the bolt to
>be in tension, not shear.
>Carl Hoffman