Today's Message Index:
----------------------
1. 04:10 PM - Z-bracket height (again) - Help! (Michael D. Cencula)
2. 06:06 PM - Re: Z-bracket height (again) - Help! (Charlie England)
3. 08:05 PM - Re: Z-bracket height (again) - Help! (Michael D. Cencula)
4. 09:51 PM - Re: Z-bracket height (again) - Help! (Charlie England)
Message 1
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| Subject: | Z-bracket height (again) - Help! |
Guys, I'm stumped!
My when I set my leading edges on the spar, the leading edge skin butts right
up to the main wing skins (both top and bottom) perfectly. With the tanks,
it's a different story. I've been trying to figure out what's causing the
gap and the only thing I can come up with is that the Z-brackets are a little
too high.
If y'all have a couple minutes and would be willing to look at what I've
tried, I'd sure appreciate any feedback how to fix it. At this time, the
only solution I can think of is to put a joggle in the web of the Z-brackets
which will effectively shorten them by .040 inch. That seems like it'll be
pretty difficult, though so I'm really hoping for a better solution.
Here's some pics that document the problem:
http://www.our7a.com/20070315.html
http://www.our7a.com/20070317.html
Thanks,
Mike Cencula
Message 2
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| Subject: | Re: Z-bracket height (again) - Help! |
Michael D. Cencula wrote:
>
> Guys, I'm stumped!
>
> My when I set my leading edges on the spar, the leading edge skin butts right
> up to the main wing skins (both top and bottom) perfectly. With the tanks,
> it's a different story. I've been trying to figure out what's causing the
> gap and the only thing I can come up with is that the Z-brackets are a little
> too high.
>
> If y'all have a couple minutes and would be willing to look at what I've
> tried, I'd sure appreciate any feedback how to fix it. At this time, the
> only solution I can think of is to put a joggle in the web of the Z-brackets
> which will effectively shorten them by .040 inch. That seems like it'll be
> pretty difficult, though so I'm really hoping for a better solution.
>
> Here's some pics that document the problem:
>
> http://www.our7a.com/20070315.html
> http://www.our7a.com/20070317.html
>
> Thanks,
>
> Mike Cencula
Have you tried pulling the tank down (back) on the spar with ratcheting
strap clamps? (You'll need a spacer at the rear spar to keep from
bending the trailing edge skin.) Run the straps directly over ribs; I
think I put them one bay in from each end of the tank.
With the ribs, it's easy for slight flange irregularities to add up &
push the back baffle back.
Have you checked to see if the back baffle is totally flat (not bowed to
the rear) when it's assembled to the ribs & skin? If it's not, that
would be another indicator that the flanges are pushing the baffle back.
Charlie
Message 3
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| Subject: | Re: Z-bracket height (again) - Help! |
<snip>
> Have you tried pulling the tank down (back) on the spar with ratcheting
> strap clamps? (You'll need a spacer at the rear spar to keep from
> bending the trailing edge skin.) Run the straps directly over ribs; I
> think I put them one bay in from each end of the tank.
>
> With the ribs, it's easy for slight flange irregularities to add up &
> push the back baffle back.
>
> Have you checked to see if the back baffle is totally flat (not bowed to
> the rear) when it's assembled to the ribs & skin? If it's not, that
> would be another indicator that the flanges are pushing the baffle back.
>
> Charlie
Charlie,
Thanks for the response. Indeed I have tried pulling it down with ratcheting
strap clamps. I can close the gap up by doing that, but doing so flexes the
baffle. Is it normal to need to pull the tank towards the spar before
driving the screws into the platenuts?
With no clamps on, the baffle is mostly straight, but the center is bowed *up*
a little. I believe that bowing is because the weight of the tank is resting
on the Z bracket.
Mike
Message 4
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| Subject: | Re: Z-bracket height (again) - Help! |
Michael D. Cencula wrote:
>
> <snip>
>> Have you tried pulling the tank down (back) on the spar with ratcheting
>> strap clamps? (You'll need a spacer at the rear spar to keep from
>> bending the trailing edge skin.) Run the straps directly over ribs; I
>> think I put them one bay in from each end of the tank.
>>
>> With the ribs, it's easy for slight flange irregularities to add up &
>> push the back baffle back.
>>
>> Have you checked to see if the back baffle is totally flat (not bowed to
>> the rear) when it's assembled to the ribs & skin? If it's not, that
>> would be another indicator that the flanges are pushing the baffle back.
>>
>> Charlie
>
> Charlie,
> Thanks for the response. Indeed I have tried pulling it down with ratcheting
> strap clamps. I can close the gap up by doing that, but doing so flexes the
> baffle. Is it normal to need to pull the tank towards the spar before
> driving the screws into the platenuts?
>
> With no clamps on, the baffle is mostly straight, but the center is bowed *up*
> a little. I believe that bowing is because the weight of the tank is resting
> on the Z bracket.
>
> Mike
Are the tank holes/spar holes offset by the same amount as the skin gap?
(I've 'over-prepped' an edge or two & that could leave a gap at the
point in question.)
Is the gap between the tank skin & wing skin perfectly consistent along
the entire length & on both top & bottom of the wing? If not:
Is the spar perfectly straight? (Jack under middle of trailing edge spar
& tweak it up/down to see if the tank will fall into place with a little
help from the straps.)
Is there any twist in the spar?
If you haven't riveted on the outboard leading edge, have you tried the
tank without the outboard leading edge in place?
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