Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Fri, 07 Feb 2003 02:26:17 -0500
Message-ID: <redirect-2011581@logan.com>
From: Jeffrey Peterson <jbp@fire.phys.cmu.edu>
Subject: Re: LNC2 extended wing tanks
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII

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