Attaching Wings

The first step in attaching the wings is to level the fuselage. I used a combination of a digital smart level and a water hose.  I leveled side to side by bringing the water level to the bottom of the pre-drilled holes in the fuse for the front wing attach point. A bit of food coloring and a few drops of dish soap (gets rid of the meniscus which is the curve you see where the water ends in the tube).  Then you level the fuse fore and aft on the bottom longeron between stations C&D.

The holes are pre-drilled undersize to 1/4 inch in the fuselage and to 3/16 in the wings.   The first thing I did was run a 1/4 steel rod between the fuse attach points to see what angle of incidence the holes were at. I was getting a reading of 2.5 degrees on the left and 2.8 on the right. Bob specs 2 degrees on the plans so I was a bit concerned about this.  I gave Bob a call and his actual number in the design is 2.3 degrees but he spec’d 2 to keep it simple.  He said, from a designing point of view, that it is a bit of a guess as to the actual number to use, so as long as you are close you will never notice a difference in half a degree or so. The most important thing is to get both wings as close to the same as possible.  So I left the left side alone and filed the right side holes until I got 2.5 degrees. I filed the bottom of the front hole and the top of the rear, this made the holes oblong but when you open them up with a bigger drill, the bit automatically finds the centre and drills the hole to the new centre. Once I had both sides the same I opened up the front to 3/8.  There were not any drill guides available from Avipro and I didn’t want to spend the time making up my own. I have drilled and reamed thousands of holes in my career so I just laid out a reference line and used that to drill and ream. The rear hole was opened up just enough to make the hole round again which turned out to be 9/32 so that still left 1/32 to go.

Knowing the forward holes in the fuse were now set, I was able to drill and ream the  holes on the wing main spar on the bench. I made up a drill guide with a couple of holes in it to guide an undersize drill and then the reamer, so I was assured squareness.  This would make the wing install much easier as the front holes were done so I could bolt the wings on with the 3/8 in bolts and just make any small adjustments to the rear. I spanned a four foot level across the bottom spars with the digital level attached to this and set the wing to 2.5 degrees. I only had to file a small amount of the hole in the rear spar to have it match up to the fuselage hole, when this was done I drilled and reamed the rear holes to 5/16. Both wings now read 2.5 degrees so I was happy with that.

The next step was to attach the wing struts. I made up a stand that I could move in and out to get the required dihedral of 1 degree and again, the most important thing is to get both wings the same. I did this pretty much the same as Eric outlines on his site so you can check out the details there. I used the water level method again with a gauge made up of the right length to check both ends.

The one thing I have a hard time with is the squeezing down of the struts at the ends. I know most, if not all, the Bearhawks and the few finished Patrols are done this way with no issues at all, but putting those nice extrusions in a vice and squeezing them down just doesn’t compute with me.  It is probably my Toolmakers brain that is responsible for this, but my thinking is why not just have the strut end blocks made to the same size as the distance between the pads on the strut extrusion. I wasn’t about to remake them though, so I made spacers up for both sides that are .080 each, which made the total height just a few thou under the size of the opening in the struts. It took me about an hour to make up the eight for me and eight for another builder.  I discussed this with Bob before doing it and he had no problem with me going this route.

So both wings are on and set up the same so she should fly nice and straight.

Wings done.

Finished lift strut.

Assembled with spacers. Yes, you need next size longer bolts.

One for each side.

Making the spacers for the strut ends.

Clamping top end.

Initial mounting of strut ends.

Ends deburred and polished.

Cutting struts to length.

Water level for measurement. It’s just under 2 15/16 difference in height from root to tip to get the 1 degree dihedral.

With no helpers around I used a tiedown strap to hold the wing in position, along with some clamps, while I drilled out the rear hole.

Brian couldn’t wait to sit in plane and see what the sightline looked like with the wings on.

Wings are square within 1/2 inch.

Wings attached with front bolts in and stands under wings.

Brian and his buddy Clifton were here to help. We used a drywall lift which certainly made things easy.

Wings ready to go on.

Drilling and reaming 3/8 hole in main wing spar using a guide.

Measured to bottom of hole, it’s easier to judge than going to center.

Leveling side to side. Adjusted air pressure in tires to set level.