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[Fwd: tank skins]

Posted: Fri Feb 17, 2012 8:56 pm
by klehman
Hi Mike
I forwarded this to the list in case anyone else was curious. My bottom
tank skins are 39"x20.8" for the three bay tank. 27.5"x20.8 for the two
bay tank. Top skins are about 1/4" more front to rear. Yours may well be
different but that is what I used after a great deal of thought. I did
scallop the wing skin slightly at each stringer but I did not eliminate
any rivets.

Another thing that surprises me is that I've never seen any one cut the
wing skin into a 9' length and use a separate piece behind the tank. The
joint would have to be done properly and approved by MAM but no one
would hesitate to do a repair like that at a later date, and it would
make things easier...

Bobp - regarding you concern about the number of rivets in the leading
edge that some of the guys used in their tank variations: Originally I
think MAM only halved the rivet spacing in the tank bottom along the
main spar (doubled number of rivets). I seem to recall asking them and
getting approval to add the extra rivets on the top of the tank as well.
Even farther back, before wet tanks, I don't think they doubled the
rivets in the bottom either (could be wrong about that though). I think
all the wings I've seen have at least the number of rivets that those
original aircraft called for. I assume the static wing test was done
before the wet wing was developed, or was it??

cheers
Ken

"Jones, Mike" wrote:
Hi Ken

After reading all this stuff about tank skins was wondering if you could
give me dimension of size you used as i most likely have small skins as well
and might want to replace with larger size as you did

got fuselage almost back together now, on to the controls very soon

mike


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[Fwd: tank skins]

Posted: Fri Feb 17, 2012 8:56 pm
by Bob Patterson
Hi Ken !

There were later static tests done, at the time of the upgrade
from 1,450 to 1,650 gross, with the wet wings, to prove out all of
the additions. That's when I saw the failure pattern that occurs
when loads exceed the absolute limits.

My concern wasn't the number of rivets specified, but the
suggestion that some builders scallopped the leading edge and just
didn't rivet it in the tank area, because they couldn't slide it
into place because of dried ProSeal. I guess this was because they
didn't know about sliding it in temporarily covered in Saran Wrap
or waxed paper to prevent ProSeal sticking, or using something else
to keep the space open..... The missing rivets would definitely
weaken the leading edge.

You might want to expand on your idea of cutting the wing
skin for easier installation. As you know, the present method was
pioneered by Brian Cross, who submitted drawings which the factory
then adapted as standard procedure. Before that, you had no way of
completing the tank and inspecting/repairing it without the whole
top skin being installed ! I'm sure they are still receptive to
any suggestions that will improve the building experience - and
might even make it easier to manufacture.

......bobp

--------------------------------orig.-------------------------------------
At 11:14 AM 5/22/01 -0700, you wrote:
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Hi Mike
I forwarded this to the list in case anyone else was curious. My bottom
tank skins are 39"x20.8" for the three bay tank. 27.5"x20.8 for the two
bay tank. Top skins are about 1/4" more front to rear. Yours may well be
different but that is what I used after a great deal of thought. I did
scallop the wing skin slightly at each stringer but I did not eliminate
any rivets.

Another thing that surprises me is that I've never seen any one cut the
wing skin into a 9' length and use a separate piece behind the tank. The
joint would have to be done properly and approved by MAM but no one
would hesitate to do a repair like that at a later date, and it would
make things easier...

Bobp - regarding you concern about the number of rivets in the leading
edge that some of the guys used in their tank variations: Originally I
think MAM only halved the rivet spacing in the tank bottom along the
main spar (doubled number of rivets). I seem to recall asking them and
getting approval to add the extra rivets on the top of the tank as well.
Even farther back, before wet tanks, I don't think they doubled the
rivets in the bottom either (could be wrong about that though). I think
all the wings I've seen have at least the number of rivets that those
original aircraft called for. I assume the static wing test was done
before the wet wing was developed, or was it??

cheers
Ken

"Jones, Mike" wrote:
Hi Ken

After reading all this stuff about tank skins was wondering if you could
give me dimension of size you used as i most likely have small skins as well
and might want to replace with larger size as you did

got fuselage almost back together now, on to the controls very soon

mike
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