I am not building mod78, but it sounds to me like a joggle may be
better than an arc. Instead of bending, you could weld the joints or
use elbow fittings. In any case, I would go with a thick wall tube. I
got some of these for linking my autopilot servos.
http://www.aircraftspruce.com/catalog/mepages/alumtube_6061t6.php
In any case, I can't envision any scenario where the aileron forces
are so strong as to bend a metal tube, unless your passenger is
fighting you at the controls :-)
Speaking of tank swelling, if your tank is currently dry, you may want
to take extra precautions when filling. Most tank failures have
occurred exactly in these instances. One option might be to fill it
slowly, over several days to allow the tank to slowly expand, before
putting much weight on its supports.
On Fri, Dec 6, 2013 at 11:03 AM, djaflyact <djaflyact@gmail.com> wrote:
>
> Well, I found the problem with interference with my right wing fit. I had
> forgotten
(until I pulled the left wing out again) that I had a swelling fuel tank
problem early on in the flying of the airplane. The brackets that hold the tank
back worked great - in the area of the bracket, but in between the tank swelled
until it rubbed on the aileron cross link between the CS08 arms. My solution
at the time was to move one end of the cross link forward of the CS08. That
allowed it to clear the tank, but that is now the reason I cannot get the right
wing to fit. It has to go back to the original position.
>
> I've got two choices: The cross link rubs the fuel tank or the I fly with only
one wing.
>
> Since there is no reasonable choice there, I think there are also now 2
> possibilities:
I move the fuel tank wall back or I bend the cross link bar to clear
the swollen tank.
>
> Right now, I only see the arcing of the cross link as the answer. If it is not
straight, it will not be as strong in compression. I doubt the loads are very
high, but there is the issue of jammed controls and the ability to provide force
in a situation like that.
>
> Would I make a contestant arc in the tube?
> Would I make a joggle in each end so that most of the rod is straight?
> Would I replace it with steel?
> Would I fill it with something like epoxy to make it stronger?
> Can the tank wall be pushed back? I can only imagine coating it with
> fiberglass
or carbon cloth and some sort of hydraulic press holding it while it cures
(I doubt this is possible).
>
> Has anyone experienced this issue with the fuel tank?
>
> Of course, the temperatures here have dropped to 0F at night, which is making
progress more difficult. I am getting close, however.
>
>
> Thanks,
>
> Dave
> A227
> Mini U2
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=414977#414977
>
>
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