The Murphy Builders Site

Here's Murphy's response to my query and it looks like with my edge
allowance I can attach the wing skins separate. Their only concern seems
to be stress during testing so I'll probably cleco the main skin on
during testing. Ken Lehman also sent me a note regarding the inter
pitching of the row of rivets along the top of the main spar, which
allowed the leading edge skin to be closed up after tank testing. I'll
include it here for consideration.


Ken Lehman said:
"I haven't looked at the issue of the number of rivets in the main spar
flange yet. Phil said that Murphy is aware of what he did, which was to
seal the tank while omitting every second rivet on the top spar flange.
He then drilled out the nose skin holes that covered those rivets to 1/4

inch or whatever it took to clear those rivets. After pressure testing
he then installed the nose skin using the (so far) unused rivet holes.
Maybe this procedure is common now, I don't know."

Has anyone else done this? TNX ...Wray
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To: Wray Thompson <wrayt@ibm.net>
From: Murphy Aircraft Tech Department <murtech@murphyair.com >
Subject: Re: [Fwd: Wing skin to tank skin]
Date: Wed, 14 Jan 1998 11:38:23 -0800

Hi Wray,

On the tip end of the tank skin, if you follow the rivet pattern suggested
that is suffiecient to attach the tank skin to the wing skin. You may have
to offset the rows from each other in order to maintain adequate edge
distance clearance and still keep within rivet to rivet distance
requirements. Also the wing skin is not sandwiched between the tanks skin
and the rib. the stregnth of this area is suffiecient. As far as testing
the tanks without having to install the wing skins, it can be done, however
you may over stress the rivet that attach the tank skin to the rib as now
all of these rivets will be taking the load during the test. Finally, the
main spar rivet line on the top skin can be interpitched as per the bottom
skin. I hope this helps,

Bijan

At 09:30 PM 1/13/98 -0500, you wrote:

Haven't had a reply yet on my previous query ..maybe because I sent it
to sales instead of tech? I would still like to be able to install both
main skin wings separate from the tank if possible.
On another note my wet tank instructions (dated 07/27.94) call for
adding additional rivets between the existing, on ribs 1 & 4 for both
the bottom and top tank skins but only for the bottom along the main
spar. Is this correct or should there be additional rivets put in along
the main spar for the top tank skin as well?
Many thanks ...Wray R306
Message-ID: <34B7DEF8.E24DF347@ibm.net>
Date: Sat, 10 Jan 1998 15:50:00 -0500
From: Wray Thompson <wrayt@ibm.net>
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Subject: Wing skin to tank skin
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Hi
When it comes to the instructions for attaching the wing skins to the
tank skins my instructions are a bit confusing. The instructions for
the top skin seem to indicate that all attachments takes place outside
the tank. ie the wing skin is not sandwiched between the tank skin and
the rib. The instructions for the bottom have the wing
skin sandwiched. I have the same 1" of free board of the tank skin out
side the last tank rib on top and bottom. It would appear that if I use
a rivet pitch of about 3/4" and offset 2 rows of rivets out side the
tank that I can maintain 5/16" edge distance and at least 4 rivet
diameters between rivets.
My question is - will 2 rows of rivets parallel but equally offset from
each other with a pitch of 3/4" be sufficient to attach the wing skin to
the tank skin, out board of the tank? or would even fewer be sufficient?

I would prefer to attach the tank skins and test for leaks without
having to permanently attach the main wing skins until after the tanks
are tested.
I would appreciate your insight
many thanks ...Wray Thompson R306

Murphy Aircraft Mfg. Ltd.
Ph: 1-604-792-5855
Fax: 1-604-792-7006
e-mail: murtech@murphyir.com
Web Site: http://www.murphyair.com