EMAIL REGARDING WING BOLTS SITUATION

-----Original Message-----
From: Gus Funnell [mailto:gusf@vansaircraft.com]
Sent: Friday, May 19, 2006 12:57 PM
To: Brian Meyette
Subject: Re: wing mounting

I guess I'm puzzled why you didn't put bolts into the holes common
to the wing spar when the gear weldments were fitted initially. I know
it tells you to do this in the 04 version of the fuse manual. Not sure if
that was the case with whatever vintage you have, but you had to
remove the powder coat from the holes you did put bolts in, and I'm
sure most guys are curious enough to look at the alignment of the
other holes when fitting the weldments. If you've never touched them
til now you may well find there are burrs around the holes that need
to be cleaned up.

There will be some small variation in the fit of the bolts. The bolts
themselves vary in size, the alignment of the front/rear will vary, and
the tools used at each hole to ream them may also vary slightly. Put
that lot together and you can expect that some will go in easily, some
not so easily. Lubrication and driving them through with a hammer
will get them in OK (it's also OK to freeze them), but use the drift
pins to align them as well as possible before you use the CT bolts.
You can hit drift pin very hard, not so much on the bolts because
you can damage the threads/hole more easily.

It would be better to remove the weldments to clean up/enlarge the
holes as necessary, but if you don't want to do that you'll just have to
get as many bolts in as possible then very carefully clean up the
others. There's really no good way to do it from the rear, but if you
use the ground down reamer idea below, measure the hole carefully
and then use a reamer 1-2 thou less than that, or the same size as
the bolt you're installing. Nominally, the holes are reamed to .247,
but as I said, you'll see some slight variation.

The fit of the weldment holes on the bolts is not that important, so
you could pull the weldment slightly forward off the spar, put some
thin aluminum between the spar and weldment and attack the
problem holes with a small rotary file on a flexible drive. That way
you avoid any potential damage to the spar.

Vans


On 18 May 06, at 15:43, Brian Meyette wrote:

> I was looking at the wing mounting for my plane, and I may have a
> serious problem to resolve somehow.  I am hoping you can help.
>
> This is for 7A  #71008 QB  tri-gear
>
> I am concerned that getting the bolts in to hold the wings on is going
> to be very tricky.   I understand that no reaming is allowed on the
> spar bolt holes.  I see several difficulties with this.  The gear leg
> mount frame holes do not line up perfectly with the holes in the spar.
>  If I’d known of this problem beforehand, it would have been trivial
> to enlarge the holes in the frame a bit – at least to knock off the
> powder coating inside the holes. With the gear frames final-installed,
> gear legs mounted, brake lines in, and engine installed, it is not an
> option to remove the gear leg frames. Anything I do to the gear leg
> frame holes will have to be done in place.  I can probably do the top
> holes from the fwd side, using a rotary file.   But the bottom holes
> are completely blocked from the front by the gear leg tube and braces.
>  If I have to do anything to the bottom holes in the gear leg frames,
> it will have to be done from the rear, unless you have some better
> suggestion.
>
> It is my understanding that no reaming is allowed, because the holes
> in the spar bars and web are very precisely made.  Yet, that does not
> appear to be the case on my plane.  For example, if I use one of the
> ¼” NAS bolts and try slipping it into the ¼” holes by hand, on most of
> the ¼” holes, the bolt slips into the hole up to the bolt shank, then
> requires more force to go any further, as expected.  But if I put the
> ¼” NAS bolt into either the LT or RT upper side ¼” hole, I can easily
> slip the bolt by hand all the way through both fwd & aft spar webs,
> right up to the bolt head.   I’d even say it’s a bit of a sloppy fit.
> That tells me all these ¼” holes are NOT reamed to exactly the same
> diameter.
>
> The NAS bolts are 0.436 diameter.   I have some hardware store bolts I
> am testing this with.  The one I am using has a 0.433 diameter.  I
> have been seeing how well these hardware store bolts go through the
> 7/16” holes, to give me an idea of where problems will be when I do
> the NAS bolts for real. I see inconsistencies there, too.  On the top
> two 7/16” holes, the cheap bolts will go all the way through both spar
> bars OK, then have some mild interference with the holes in the gear
> leg frames.  This is the same on both sides.  Not a big problem.  I
> can grind the 2 top 7/16” holes on the gear leg frame a bit from the
> front to fix that.  But on the bottom 2  7/16” holes, on both sides of
> the plane, the hardware store bolts go through the aft spar bar OK,
> but they won’t even start into the fwd spar bar.   This tells me the
> holes must not be lined up right and/or they are of different
> diameter.
>
> Also, IF I need to do anything to the lower 7/16” holes in the gear
> mount frames, it will have to be done from the back.  I thought
> perhaps you could tell me the exact diameter these holes are reamed
> to.  I could get a reamer that is 0.0005 or 0.001 less than that, and
> dull the cutting edges except for the first 1/8”.  Then I could
> carefully work the oiled reamer through the bottom spar bar holes and
> let the front edges of the reamer blades work against the gear leg
> frame.  The dulled blades would cut little, if anything, in the spar,
> and would serve as a guide for the reamer against the gear leg frame.
> That’s the only idea I can think of.   Do you have a better one? 
> What exact size reamer do you use for these 7/16” holes through the
> spar bars?
>
> Also, do you have an explanation for why the same cheap bolt will go
> cleanly through both upper 7/16” holes, fwd and aft spar bars, on both
> sides of the plane, but will not even start into the lower two fwd
> spar bars after going through the aft spar bars from the rear?
>
> Is there any limit to how much force can or should be used to drive
> these NAS bolts home for the final installation?   On the 3 gear leg
> mount bolts, I carefully reamed them until the threads, but not the
> shank, would just barely slip in.  Then I used a 6x rivet gun with
> brass tip to drive them home.  They are in tight.  These bottom wing
> mount bolts look like they may be a problem, and there is no room
> behind them for much force.  I will probably have to take up the floor
> to get a hammer or gun behind them with enough force to drive them in,
> once the above questions are resolved.  Will it help to heat the spar
> with a heat gun and freeze the bolts first, or will that make the
> bolts too brittle to be driven?  I’d sure hate to have one shatter!
>
> I urge you to update the 7A manual or issue a bulletin to tell people
> to run a 7/16” bolt through the gear leg mount frame holes before
> installing them. This simple step would eliminate a huge problem down
> the line.

 

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