Thanks for that input. I understand your reasoning, but it would be a
better solution to countersink only as necessary and use a longer bolt.
The spar is only about 1" thick, and I don't like the idea of boring
60% of it away with a 3/4" drill. In fact a diameter of 11/16" to a
depth of 1/4" will comfortably fit the AN4 bolt head and the EURO
washer. So I ordered different lengths of AN4 bolts and will try them
out. They are only 50 cents each. I don't know why the manual wants us
to drill a deeper hole instead of giving us a longer bolt.
--- Kingsley Hurst <hurstkr@growzone.com.au> wrote:
> <hurstkr@growzone.com.au>
>
> > Wouldn't this cause the spar to become
> weaker, which is probably the most critical structure of the
> airplane?
>
> Andrew,
>
> The counter boring is done in the timber in the middle of the spar.
> When a beam is under load, the centreline takes no load. In the case
> of
> the spar under normal +ive G loading, the top of the spar is in
> compression and the bottom is in tension. The middle is neutral.
> The
> timber is only a spacer to hold the top and bottom spar rovings
> apart.
>
> Suggest you just use the bolt called out in the manual and
> countersink
> the hole until the other end of the bolt is just long enough to hold
> the
> parts it has to hold. If it is too long, it will conflict with the
> other bolt in the aluminium bracket when the wings are rigged.
>
> Regards
> Kingsley
> Mono Classic 281 in Oz.
>
>
>
>
>
>
>
>
>
=====
Andrew Sarangan
http://www.geocities.com/asarangan
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