Wings Fit

If you have been following my progress building a Bede BD-4C airplane for awhile, you might have been wondering where I have been and why I have not posted anything for several months. Frankly, I hit a terribly frustrating phase and have been too discouraged to write about it. I finally got past it, though, so here is the story.

Back in July, I got a lot of help from my friends and we installed the wings for the first time.

Lifting the right wing into position
Lifting the right wing into position

The large hole in the end of the wing is the spar, a tube with a 6.5 inch inside diameter which runs the whole length of the wing. It slides onto the center section of the spar, attached to the fuselage, which has a 6.5 inch outside diameter. Here is a close-up so you can see a little better. (You can click on any of these photos to see them larger.)

Wing spar and center section of spar
Wing spar and center section of spar

This would have been well and good if the spar in the wing and the center section of the spar in the fuselage were perfectly round. They are not. Nothing in life is perfect. Each is slightly oval.

This would even have been OK if the ovals were close to lined up. They are not. By sheer bad luck, the narrow part of the oval tube in the wing was lined up with the wide part of the oval tube in the fuselage. This was the case for both wings.

Installing the wings should have gone pretty easily. It turned out to be a royal PITA. It was a huge struggle to get them onto the center section of the spar. Once on, they were thoroughly stuck. It took a lot of muscle and “persuasion” to get them off again.

The solution, I was told, was to hone out the spars in the wings, enlarging them slightly so that they would slide onto and off of the center section. What do you use to hone the inside of a 6.5 inch aluminum tube? A 6.5 inch Flex-Hone, of course.

6.5 inch Flex-Hone
6.5 inch Flex-Hone

Here is a picture of me using a smaller version.

Using a Flex-Hone
Using a Flex-Hone

A friend was amazingly kind and lent me his 180 grit, well used Flex-Hone. I crammed that into the spar on the left wing and honed and honed and honed until I literally burned up my DeWalt 1/2 inch drill. We’re talkin’ smoke pouring out of the machine and it didn’t turn any more. It takes a lot o’ power to turn a big Flex-Hone. I bought a cheap 9 amp drill from Harbor Freight and it survived the abuse I gave it.

What made this so discouraging was that I could only work on the wings when I could get a couple of other people to help and when the weather was nice and I had several hours to get the plane out of the garage. It takes three people to wrestle the wings off of the sawhorses (see above) and put them onto the plane or into a position where I could hone them. So every once in a while, I would muster the troops and work on the wings. I would hone and hone and hone and then try to install the wings and find that they were still too tight and then get help wrestling them off the fuselage and putting them away. It only takes a few lines to write it but it was a several hour job every time.

Finally, I purchased a new 120 grit Flex-Hone. Between being new and having coarser grit, this one did the job. After a couple more honing sessions, the wings finally slide on and off the center section of the spar very easily.

Once I could install and remove the wings, I was able to set the aileron controls and install the flap controls. The ailerons work right. The flaps need a little more tweaking. I will have photos of those soon.


4 thoughts on “Wings Fit”

  1. Hi Art, I feel you pain. I test fitted my spars to the center spar in the fuselage a few months back. much to my displeasure, they went on way too easy. Right away I knew this not to be a good sign. When I grabbed the sar at the wimg tip, I could move it up and down by about one inch. Not sure if there is anything I can do other than replacing the center spar. By the way, I should have explained that I have an origional center spar 2024-T3 and the new style spars 6066-T6. I believe the reason they are too loose is that the center spar was turned down for the origional 2024-T3 spars. So I guess I will have to bite the bullet and buy a new center spar. That is if I can get the good people at Bede to return my calls.
    Keep up the good work Art.
    mike Lamb

  2. Glad you got them to fit. I was getting worried not seeing updates for a while. I am working on the wife to start in the next 3 years sometime.

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