Wing and strut installation

[rodsmith]

Just finished installing my quick build wings on my plans built fuselage. All in all went pretty well. I had Mark send me the wing attach hole drill guides. He mistakenly sent the LSA guides initially, which has a 1/4" and 5/16" drill guide. I hung on to those as I was happy to also have a 1/4" guide. Both my fuselage fittings and wing fittings had 3/16" pilot holes. I made some hole locators for the back side of the guides. They were 3/16, 1/4, and 5/16 pins welded in sleeves a 16th larger (1/4" pin in 5/16" sleeve etc). I drilled the holes in 1/16" increments, final size was done with reamers after drilling 1/64" under. I bought a 12" drill extension and was going to machine the base of the drill bits to 1/4" to fit it. Unfortunately when I put a 1/4" bit in it, it had some run out which was unacceptable. I ended up welding the bits and reamers to 4130 tubing, way cheaper than buying 12" bits. I initially planned on renting a dry wall jack but made some sturdy supports for both inboard and outboard wing locations with height adjustment. With three friends it was easy to get the wings up and into position. Installed the right wing first with 3/16th bolts and everything was perfect. Angle of incidence was exactly 2.0 deg, wing was exactly perpendicular to fuselage centerline. Used the drill guides with locator pins in the backside and drilled to size without having to make any adjustments. Left wing was another story. The vertical tube the rear fitting is attached to was slightly forward of where it should have been. The backside of the rear fitting interfered with the wing fitting. We had to put the wing back on the table. I cut off the rear side of the rear fitting and replaced it an 1/8th of an inch aft. Only took a few hours but it was 10 days before I could get everyone together again. On the second try was able to get the 3/16th bolt through the rear fitting. On the front fitting there was some misaligment, the bolt wouldn't go through the back side of the fuselage fitting. The wing was aligned great so opened up the hole on the rear fitting and proceeded to drill to size. Ended up with a 1.9 deg angle of incidence on the left wing. Measurement from wing tips to tail post were different by 1/8". 2" is considered good enough so I was really surprised how close it was. I built the wing struts according to Bob's instructions. Found it difficult to clamp the flat fittings to the curved outside of the strut and align them parallel with the flats inside. Took several attempts to get the clamps in the exact right position. When transferring the fittings to the inside I had some minor misalignment on a couple holes and ended up with some loose holes. I highly recommend starting out with 3/16" holes and bolts. When everything is measured and drilled, re drill to 15/64" and ream to 1/4". As far as getting the strut length correct, it was easy with the water level to set the wing tip to 2.9" higher. I drilled the struts for the inboard fittings and bolted them to the top of the strut, that way only had to clamp the outboard fitting to get the correct length, with the wingtip at the correct height. Be very careful that you don't get fittings mixed up from side to side, or flip them top to bottom while taking measurements or drilling. I was afraid of doing that so marked everything real well.

[rodsmith]

One other bit of advise. Don't install 1 strut and pull the wing tip support before measuring for the other strut. It flexes the fuselage enough it could throw off the measurement for the other strut and makes it hard to keep the fuselage level side to side for that measurement. Fortunately I noticed what was happening, put the support back under the wing and pulled the bolt at the fuselage to "unload" the frame to get the other side measured.

[rv8bldr]

Excellent description, Rod. Thanks for this.

[DRLPatrol]

Thanks for the write up.

Not really following your "I made some hole locators for the back side of the guides. They were 3/16, 1/4, and 5/16 pins welded in sleeves a 16th larger (1/4" pin in 5/16" sleeve etc)."
Could you give some more details how you used them.

Doug

[tbaylx]

They way I understand it is the pin fits into the undersize hole on the backside and locates the drill guide for the front. Then because the pin is in a sleeve as the drill runs into the pin as it drills the hole it pushes the pin out the back side.

[DRLPatrol]

OK. That makes since. Maybe I was half asleep because it was to late last night. I should have been able to figure that out.

Thanks
Doug

[Brandaoandre]

Rod, from your experience, how late can we install the wings? I ask this because I have limited space at home. Can it be the last thing? After covering the fuselage, engine installation and painting the wing? Andre

[rodsmith]

They way I understand it is the pin fits into the undersize hole on the backside and locates the drill guide for the front. Then because the pin is in a sleeve as the drill runs into the pin as it drills the hole it pushes the pin out the back side.

That's exactly it. Keeps the backside of the drill guide exactly where you want it.

[rodsmith]

Rod, from your experience, how late can we install the wings? I ask this because I have limited space at home. Can it be the last thing? After covering the fuselage, engine installation and painting the wing? Andre

I guess it depends on your confidence in accurately mocking up the position of the wings for things like windshield installation, flap pulley installation etc. My quick build wings came with the inboard arm of the flap torque tube welded on. I wanted to make sure the arm was in the right position and the pulley angles were good (pulley mounts tack welded only at this point) before drilling and bolting the arms at the outboard end. I'm installing a skylight and wanted to make sure I installed the support for the back of the windshield/front of skylight at the correct height and angle. I just got through fitting the windshield and feel much better with it matched in height and position to the actual wings versus a mock up location. While the wings are on I am going to complete the aileron and flap control cable installation. Then they will come off and I will be sandblasting and painting the fuselage to get ready for fabric.

[svyolo]

I am finishing up final assembly. One thing I can't find an answer to, is do you fully torque the wing bolts. I tend to think I should, but the front and rear are made concentric for a reason - movement. Are the main bolts torqued to an5-6 specs or just snugged like a bolt meant to act as a pivot?

[Frank]

I determined that the wing attach mounting holes and bolts are not concentric, at least for the LSA. Am I wrong? https://bearhawkforums.com/filedata/fetch?id=87574

[svyolo]

IIRC the instructions I followed had me first make the holes concentric in the fuselage fittings, then elarge them. Mine were very very close from the factory. I used a piece of 3/16 and 1/4" piano wire/tubing as a guide.

[rodsmith]

Once the struts are installed, they aren't going to pivot. I fully torqued all wing and strut bolts.

[alaskabearhawk]

FWIW we left the wing spar bolts loose as we had to move the wing just a bit to get the lower strut fitting in place. Once everything was attached all the bolts were tightened.

[jaredyates]

Full torque before first flight, but like Paul says you would probably do that after all four bolts are in place.

[svyolo]

Another issue was there are gaps between the spars and fuselage fittings. They are significant. If I just torqued them, the spars would not be tightly captured. I filled the gaps with washers, but I think I should replace them with either bigger fender washers, or shims.

[alaskabearhawk]

That's concerning. Are both sides like that?

[jaredyates]

I would talk to Bob or Virgil about this.

[svyolo]

Yeah the fuselage mount-spar has gaps at all 4 spar mounts eyeball cal says both rear spars have about 1/8" combined gaps, main spars a bit less. It just seems to me those gaps should be filled (they are)before torquing (which they are not), I will call Bob on Monday.