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flybynightkarmarepair wrote:
> Wag-Aero has a special this month on quick drains:
> http://www.wicksaircraft.com/catalog/product_cat.php/subid=6879/index.html
>
> I am building a mongrel dog of a low wing airplane that uses wing tanks,
> pretty much like the Hummel Ultracruiser Plus. The tanks themselves
> are .032 aluminum. The question of the day is how to mount the drains
> to the tanks.
>
> 2 styles and several sizes of drains are offered. The use either
> tapered pipe thread or straight threads.
>
> Obviously, a doubler will be needed to provide enough meat to fasten
> the drains to. The question is to whether to make a fairly thick
> doubler, and tap it for the tapererd pipe thread, or to use a somewhat
> thinner doubler, tap it for straight threads, and put a shear nut on
> the inside of the tank, before pro-sealing it up.
>
> How thick should a piece of 6061-t6 be in order to securely hold 1/8"
> NPT threads? I think I am leaning toward that solution, with the
> doubler OUTSIDE the tank skin to keep the un-usable fuel down a bit.
> Looking at my "Machinery's Handbook", I would need 0.2639" for full thread
> engagement. Can I live with less than that? What do RV's use in this
> area?
>
> OR, am I barking up the wrong tree entirely, and I should grab a
> welding flange, drill some holes in it, and slap it on with rivets and
> pro-seal, and let it hang down.
> http://www.aircraftspruce.com/catalog/appages/alumflange.php
>
a/c building is like plumbing work; sometimes it pays to just pay
instead of doing it yourself.
Van's a/c has pipe threaded flanges, predrilled with rivet holes just
for this purpose. s&h will probably cost more than the parts.
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Re: Drains in Wing Tanks
