RV-6a Wing Installation

[Jerry Cochran]

Listers,

Since my -6a is a QB, I have never mounted the wings and am about to, having just moved to a hangar. It appears that in order to mount them, I must support the fuse in some manner rather than totally on the gear. Am I right? If so, what's the prefered method, with a hoist on the engine mounts or supports under the spar area?

It just looks like I'd have to have enough weight off the gear to wiggle them about while installing bolts...

Thanks in advance for those who've been there done that on -6a models..

Jerry

[painless]

Hi Jerry:

I used big aircraft jacks that a friend had and jacked the airplane off the ground at the spar. Then I made a cradle that would stabilize the aft end of the airplane and keep it from letting the airplane sway back and forth while I wrestled....er....installed my wings.


Regards,

[rvpilot]

Jerry-
We used an engine hoist attached with a nylon strap to the engine mount right next to the firewall. As stated previously, you must have a saw horse, or other stabilizing means, toward the rear of the fuse.
You are correct in that you want to get the gear barely off the ground, just enough to allow you to remove and reinstall the bolts thru the main gear weldaments.
Key elements to the whole proceedure...prior planning, don't rush, and have plenty of help!!
Good luck!

[pierre smith]

Jerry,
Yet another method, the one we used, is to weld 2 cheap hardware store bolts two pieces of 2" X 6" long channel iron and stick them into the lower motor mount bosses and into the fuselage. We used bottle jacks under the channel irons to jack the airplane off the floor and supported the rear of the fuselage with a padded sawhorse.

We also used a builder's transit to level the fuselage fore and aft/sideways by placing it about three feet from the right wingtip and sighted to the sills and the rear deck, looking at a vertical ruler, levelling it fore/aft/sideways. When the wings were ready to be drilled at the rear spar location, we stood a three foot ruler vertically on the spar and my buddy sighted through the transit and I marked the rule with a fine point marker at the crosshairs. Then we added around 3 1/32" (or whatever Van calls for) above that mark and drew a line there to locate the rear spar up and down, setting the incidence.

You'll need some cheapo bolts ground to a point to help align the wings to the carry-through box. We used two in the center and two near the outer ends of the spars. Use Boelube or any good lube to help prevent galling as you drive them in and then out again.

It is also a good time to enlarge the hole in the center web of the spar to around 1" or more for wires to later pass through. Believe me, you'll be surprised at the amount of wires there!
Regards,
Regards,

[Vern]

Depending on how tight the fit is, you might want to take a file and bevel the inboard ends of the spar and grease the spar stubs that go into the fuselage to aid in getting them in place. Several long punches will help align the holes. Be sure to clean out the holes on the fuselage former if there is primer or paint on it. The bolts are a very tight fit. It is not unusual to have to ream one or more bolt holes. It's good to mark the nuts with torque marker or fingernail polish as you torque them so you will not forget one. Be sure to run a drill bit or ream thru the gear mounts to remove any paint or powdercoat before trying to install the bolts.

! DO NOT LIFT THE PLANE USING THE ENGINE LIFT EYES! USE THE MOUNT, NOT THE ENGINE!

[Bob Axsom]

I built two 2"x6" wood horses and padded the tops with cheap carpet from home Depot for the fuselage. Then I built four horses out of 2"x4" pine for the wings and padded them. Then I bought a good grade 4'x8' sheet of 3/4' plywood and set it under the fuselage. I put the fuselage horses on the plywood. I bought four sissor car jacks from an auto parts store and put them under the plywood near the corners. I positioned the wing horses and had a neighbor help me move the wings from my wall storage location to the wing horses. Jacked up the fuselage, stacked blocks of wood under the plywood to stabilize it, removed the MLG bolts and inserted the main spar ends into the fuselage mating location. I went through this twice and the second time I cut out a significant area in the spar webs where they butt together in the center to clear the wire and trim tab control cable routing through there (preplanned so that they did not go through the laminated spar cap area). Then came the difficult part, getting all those bolts inserted in those close tolerance holes and springy not perfectly aligned MLG weldment holes. Reaming, sacrifical ground to a point bolts, lubricant, a big plastic mallet, patience and persistence are all required. At times it seems absolutely impossible. Once you get a few of them in the rest go in easier.

I used the jacks at this point to precisely level the canopy deck to establish the reference plane for the rigging of the flying surfaces. It is really important that the incidence angle of both wings ar set exactly as called for in the plans book. The fuselage or the drilling of the mating holes may be off and you cannot allow this to mislead you into letting the wings "look right" with respect to the fuselage structure - they have to be right with respect to the level reference plane. You just have to accommodate the physical interface problems. On my plane the trailing edge of the left wing had to be lifted to achieve the correct incidence angle while the right wing was correct in its natural position. The lower skins of my flaps overlap the fuselage to close the gap when the flaps are up. This required the skin to be formed like a "Z" with the center member straight up instead of at an angle and I had to rivet on a small extension tab to cover the flap pushrod hole in the bottom of the fuselage. My plane flies straight hands off but if I had drilled the rear spar holes in the "natural" position for both wings there would have been a rolling force applied that would have had to be overcome with aileron in flight. Plan on taking your time with this to get it right - what you do here directly effects performance forever.

Bob Axsom

[Rick6a]

Originally Posted by Jerry Cochran

........I have never mounted the wings and am about to......It appears that in order to mount them, I must support the fuse in some manner rather than totally on the gear........It just looks like I'd have to have enough weight off the gear to wiggle them about while installing bolts......Jerry

My plane flies straight hands off.......Plan on taking your time with this to get it right - what you do here directly effects performance forever....Bob Axsom

Bob's words should be written in bold print in the builder's manual. These pictures cannot convey nearly 3 weeks of checking, worrying, and rechecking measurements before I finally mustered the wherewithal to drill for the rear spar attach bolts. As you can see, to achieve level the main gear clears the floor. I used digital leveling tool presumed accurate to 1/10th of a degree. A series of four plumb bobs were dropped from the inboard and outboard leading edges to a straight line on the floor. I had a minor forward sweep to work out. The wings were in and out about a half dozen times to make the necessary material trims and adjustments. The result is "Darla" is truly a perfectly balanced and hands off performer when flying in calm air....well....for up to 15 seconds anyway. Stalls are met with a distinct "thud" and falls through straight ahead with no tendency to drop a wing. Rig your plane wrong during this vital step and you will forever regret it.

[Jerry Cochran]

Wow!, Just the info I was looking for... Thanks to all who replied, and Rick is right, something as critical as this should be in the manual. Of course, if we had a manual with *everything* in it, It'd take up the entire garage...

Thanks again, guys!
Jerry