Wing install to center section

chrishalfman · #1 09-04-2012, 05:49 PM

Hi! I am nearing the fit up of the wings into the fuselage. While fitting up the gear mounts (7A), I put the wood spacers in the center section I had made up (a long, long time ago, in a land far away). Then, I verified the spacers were the right thickness. It seems my center section is about 1/16" too narrow. I pried and wrenched the center section apart (with pieces of wood) but am extremely concerned with trying to the wing's spars in there. They've spread a bit, but it's still gonna be a tiiiigggghhhht fit. In fact, had to touch up the gear mount holes before I put the gear in as the lower flange on the front assembly moved forward a bit in the gear mount hole. Is this normal? I asked Van's and basically they said, it's a pre-punched kit and it should fit. First, let me say I'm a mechanical engineer that did product design for 6 years and am completely _amazed_ at how things fit without tooling, but I'm skeptical. Don't really want to jack up the mating surfaces trying to get it together.

Any suggestions or 'other knowledge' that may be relative?

Thanks in advance,
Chris
RV72079

Rupester · #2 09-04-2012, 06:10 PM

.... wood is notorious for not being dimensionally stable. (temperature, humidity, phase of the moon, etc.). OTOH, the wing spars are. I would not worry about it if I were you.

Ironflight · #3 09-04-2012, 07:54 PM

I'd get out some calipers and measure the wing spar and center section slot dimensions now - it will either tell you that you have a problem, or relieve your worries! If I understand you correctly, what doesn't fit is the wood - and yes, that can change dimension.

One of my recurring nightmares during the -3 build was that the wing spars wouldn't fit into the center section (which is built from all NON-prepunched parts), even though I slid the completed center section bulkhead onto each wing spar (on the rack) before we incorporated it into the fuselage. It was a huge relief when we slid the wings in, and they fit great.

Measure - then you'll know what you've got.

Paul

LettersFromFlyoverCountry · #4 09-05-2012, 07:11 AM

I've often wondered what the value of the wood spacers are given that everything is prepunched? I tend to think this is mostly a holdover from the old days.

I can't tell from your message whether you've actually tried to slip the wings in or not. Take a file to the outside edges, grease 'em up, grease up the top of the fuselage skin, and slip it in there.

It'll be fine.

RV7ator · #5 09-05-2012, 07:54 AM

The wood spacers are one of many inappropriate carry-overs from the -6 instructions from which the -7 instructions were derived. Loose 'em. The pre-punched holes define and completely control the opening and, yes, it's tight. Chamfer the leading corners of the wing spares, lube up and cram them in. The two spacers with the AN4 bolts across the top of the center spar set the top gap primarily for matching the seat pan holes.

John Siebold

RV8MW · #6 09-05-2012, 08:34 AM

Chris,

I just mated my wings on my 8 and I also was concerned I measured the opening and the spar and the opening was smaller. I slightly tapered the spar as the plans said and lubed it. It will fit tight but it will go.

chrishalfman · #7 09-05-2012, 06:45 PM

Thanks for the replies. I have no idea why I didn't get my calipers out and check (was just using a steel rule). Well, the center section is 20 to 25/1000 small. Not a lot, but it might be interesting sticking the wings in. I guess, lube it up and see what happens. I've also quickly browsed a couple of your suggested links and websites looking for how others did it. Thanks again! Chris