Master Rib

[BigRob]

I had to share, I completed the sanding for the master rib. I know its the just the beginning but, I'm feeling good.IMG_0969.jpg

[BravoGolf]

Looks great! You have really started

[NSLaw]

Looks great!

[geraldmorrissey]

Consider using drill bushings with serrations on the O.D. installed at strategic locations on your master templete as well as the trim/forming tooling. Use T pins or L pins to index all your trim/forming tooling back to your master templete to insure the curves match. Better yet, use the master templete to route your tooling. Bond the bushings in with epoxy. Use .0005 under pins if you can find them. They slip in and out much easier. .1875 I.D. bushings work good. Nice work so far.
Gerry
Patrol #30

[Sir Newton]

Sharing is caring! My B wings are in the final stages of completion. 1500hrs yippers! Please Feel free to ask me questions.

[alaskabearhawk]

Very nice. If you are going to use it for forming ribs, make sure the edge has a bit of an undercut to compensate for springback as you form the rib flange.

[sjt]

I made dozens of forms from the master. The bottom mdf is undersize. Then I had the metal master. Then another spacer of undersize masonite. Finally the new rough cut mdf. Routers do not work well unless the mdf is already close to size.


In the case of the patrol - the spars are 32 inches apart. What I did was to cut a mdf blank that was 32-0.016-0.016 wide. That way the center rib blank can be centered between the spar lines of the metal template, and routed using the metal master. A table saw has cut the center rib mdf in such a way that it has parallel cuts of the correct length. The router for the center ribs only cuts the curve side.

There are mdf forms for cutting metal blanks accounting for the flange. And, there are mdf forms for forming the flange.

[sjt]

about 5$ for a bearing on amazon (B3U)

There is a fast way of making mdf copies that are slightly smaller then the master. The B3U bearing is smaller then 1/2 inch. Used with a 1/2 router bit it will reduce the copy with each pass.

If you start with a mdf copy, of the master, you simply run the copy multiple times using the router bit with the smaller bearing in place.

This quickly makes smaller cover, or backing mdf forms used to sandwich aluminum.




bearing.jpghalf.jpg

[sjt]

In retrospect I would have preferred my 1/4 tooling hole to be a little further from the edge. If you look at the angle bracket used to rivet to the spar, you will see that the 1/4 hole is closer to the rivets then they would have to be. If you put the tooling holes to close to the edge, you will eventually have problems with distance from rivets.


PLUMB.jpg

[sjt]

Example of cover sheet for use in forming edge. The cover sheet is smaller and cut back on a 45 so that the hammer blow is not compromised.

I preferred using the 1 inch thick mdf sheets that can be purchased from cabinet shops. It has better grain and form blocks can be made with rounded edges on both sides. One form block can make either the right or left rib. I probably needed another cover plate with opposite 45 for the other half of the ribs. I just used a single mdf form block that was 1 inch thick.

cover.jpg

Aluminum needs about 11 degrees of over bend. I bent them as close as I could setting the corner and used a lever type device to set 90 degees.


lever.jpg