Fabricating Multiple Copies of Wing Ribs

Stack the balsa as tall as my band saw will allow. Cut.

-- Ray

For identical ribs I make a template out of plywood (I use 1/32" plywood for 1/16" wood), then cut with a nice sharp X-acto knife.

For tapered ribs (which I assume isn't what you're asking about, but I'll answer anyway) I make two templates -- one for the wing root, one ever so slightly undersized for the tip -- then I cut a stack of blanks, bolt the pile together, and carve and sand to shape.

If I had a band saw I'd certainly give the stack-sawing thing a try.

On Sun, 18 Oct 2009 07:15:47 +0800, Ray Haddad wrote in :

Tack the blanks with a drop of CA at each end.

Do the bandsaw thing, missing the line by a little bit.

Sand to the line.

Cut the rib notches carefully.

Sand the notches to a perfect fit.

Carefully break the ribs apart.

Marty

As below, but I use pins to hold the stack of balsa together for band sawing.

On Sun, 18 Oct 2009 06:23:47 -0400, Randy wrote: (top posting fixed)

A variation is to drill holes in the blanks and bolt them, then thread the blanks on to music wire for a wing jig.

I've only done it once, but it worked very nice.

Sort of as above but with the following exceptions. I precut a pair of ribs on 1/4 inch ply (not AC ply) and sand them to perfect shape and size. This includes a dowel hole near the LE or the TE on a drill press so it is to be as near square as possible. Part of the trick is to maintain the spatial orientation of the stack and the dowels help with that. Glue the dowel to the plywood guide. Stack the wood and using a drill press drill the first hole for a dowel then stack it on one of the precut plywood guide with a dowel installed. Straighten up the wood, put the other plywood guide on, tack the dowel to the top guide, and carefully drill the second hole on the drill press and add the second dowel tacking both guides to it while the stack is under pressure. No other glue is used so the ribs are clean and undamaged when you break the packet apart.

CA usually will not hold well to ply and that 'feature' is being used.

On Sun, 18 Oct 2009 15:43:51 -0500, "Six_O'Clock_High" No other glue is used so the ribs are clean and

Yes, that is definitely a problem with the CA tack-glue approach.

Neat!

Marty

A good sharp Forstner bit will cut a remarkably clean hole in balsa -- unfortunately you can't find them in sizes smaller than 1/2 inch.

I've used the brass tubing trick, but you have to clean out the tubing quite often.

I bought a set of Forstsner bits down to 1/4" ebay # 190341714221 mk (you get what you pay for)

I am surprised a respondent has not tried cutting them with a template and trim router like cabinet makers use. Thanks for the replys. Jim.

Trim routers are normally used free-hand. A band saw is as well but is far easier to control. Small things near router blades spinning at

-- Ray

Cut rough oversized rib blanks.

Make an accurate template from some fine grained wood like cherry that is 1/4th inch thick. Aircraft grade ply is ok also for the template. In either case harden the edges with CA. Include any slots needed for ribs on the template.

Drill holes in template and rough blanks with a forstner bit. Use same size bit as the rods on your wing building jig. And with the same spacing as the rods in your wing building jig.

Bolt the template and blanks together with a bolt that just fits the holes drilled above.

Cut them to size with a router mounted in a table. Use a router bit that has a flush guide bearing that rides on the template.

Hand cut any needed slots for ribs with a dremel or coping saw while still mounted on the template.

Takes 20 minutes to make the template and about five minutes to make all the ribs including slots. Then two hours or less to build the wing.

I have used a few different methods over the years. This is my version of the above methods to make wings with ribs all the same size:

1. Use Profili software to print a pattern
2. Cut the spars to suit
3. Cut two rectangles of 4mm acrylic to become the templates
4. Use Post-it glue to stick the paper pattern to the top template
5. Bind together with masking tape
6. Cut roughly to shape on a band saw - replace the masking tape as I go to keep it all together (much easier than bolting with countersunk screws)
7. Sand exactly to shape on a disk sander - once again replacing the masking tape as required
8. Drill two holes to suit my jig (an old Adjust-o-jig, but a home made one is OK)
9. Use templates to cut out oversize ribs
10. Drill holes in the ribs to match the holes in the templates. I do it one by one which is a pain and I welcome ideas to do it faster without tearing the balsa
11. Bolt ribs between templates with threaded rod
12. Sand ribs to exact shape
13. Saw and file slots for spars - use the precut spars to get the size exactly right.

It sounds a little long winded but, with my current collection of tools and jigs, it is quite fast. Once the ribs are on the jig, everything comes together beautifully and the plane then flies well.