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Ian,
Thanks for the advice.
IMHO I would not try to extend the tanks outboard of the aileron bell crank area, given the fact that the skins are on and sealed, unless you are prepared to also access the inboard side of the inboard aileron compartment bulkhead in order to seal it.
right. I do plan to open the inboard compartment. I will cut out the
existing gas cap, creating an opening large enough to reach in
to seal the inboard ends of the Al. tubes to the rib.
I'll make a closeout panel for the hole I have just created in the inboard
compartment. I'll do that by doing a layup on the wing top near the old
gas cap, then cut that to fit the new hole. then make a reinforeced flange
on the inside of the wing skin, paint everthing with sealer, and put the
cover in place with hysol.
does that sound OK?
The part of the process that concerns me is the fact that you will also have to cut the bulkhead on the inboard side of the bell crank compartment to allow you to fit the "flow channels. You can only seal the outboard side of the bulkhead. This would mean that you would have gas migrating down through the honeycomb core on the inboard side of the bulkhead. Where it would end up and when it would arrive there is a matter of conjecture but I would bet that migrate it will. If you cut open the wing skin on the inboard side and seal the hole for the "flow channels" then that would be fine.
I have tank extensions but I built them in before fitting the bottom skin. I would make the bottom flow channel as large as you conveniently can. I have the Lancair recommended installation and the gas is a liitle slow to flow into the inboard section of the tank. The vent portion at the top of the tank I believe, is large enough to vent the gas whilst filling the tank and more than large enough for normal operations.
what tube sizes do you reccomend?
You already have an Al tube running through the tank and into the aileron bell crank area. Obviously Lancair do not worry about flexing. They also recommend an Al tube for the vent portion of the extended tank so again I do not see why you could not use tube for the bottom channel.
Right, of course. Had not remembered that tube. I can see no reason for "flapper valves" in that area. In fact I would not recommend them as all they would be is a possible restriction to the natural flow of the fuel into the main portion of the tank. If you fit slosh doors at the most inboard end of the main portion of the tank, when the tank is first built then these are invaluable to help stop the fuel from unporting when the tank is low. I fitted slosh doors.
In my plan (so far) I dont think I'll have sufficient access to add anything at the inboard end of the main tank.
I am not sure I understand slosh doors. what I had in mind is a hinged cover on the inboard end of the fuel tube, so that in turbulence,
or a slip, or a spin (no I'll never DO that) this one way valve prevents
fuel from being thrown to the outer tank. I was calling that a "flapper valve". a slosh door is something else?
also, your point about restriction is well taken. didnt a stuck valve of
this sort possibly contribute to a recent fuel starvation accident? a part
cant fail if it is absent.
Hope this helps
Very much.
--
Jeff Peterson
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