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General control line discussion => Open Forum => Topic started by: Garf on July 12, 2010, 04:18:23 PM
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I am going to have to use plans to make ribs. This is the one part I have never been able to do from prints. I always break the balsa at some point. What is the best method of making intricate parts in balsa from prints?
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Not sure exactly what you are asking but here goes.
I always photocopy the ribs (full sized), cut out the individual paper copies, use a bit of rubber cement to attach them to the balsa sheet and run them through my scroll saw. That is unless they are an even taper from the root rib to the tip rib. If that is the case, I make templates of the root and tip ribs and match them up to drill two holes for my wing jig rods. I then stack balsa sheets for each rib and top the stack with the tip template. I then drill two holes through the whole stack and bolt them together with tip template on one side and root template on the other. Then I remove the balsa down to the the level of the templates. It seems easier to do that to explain. LOL
Guess this may or may not help.
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Are you having trouble with the ribs splitting when you cut spar notches in the upper and lower surface? If that is it, you can wait and sand them in after you cut the outline, or sometimes after glue the ribs to the LE / TE.
Make a sanding stick the width of the spar, and long enough to span 5-6 bays with a taper on each end. the taper is to reduce the chance of catching the end of the stick in a rib and breaking it.
Sand the notches in carefully, and check their alignment with a nice straight piece of spar material, or a string. Work the notches down to full depth gradually across the entire span.
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If all the ribs are shown, I copy the plans and glue the paper "templates" to wood, like many others do.
Some laugh, but scalpels are cheap, the blades are cheap, and they are LOTS sharper than out of the box #11 blades. Breaking/crushing balsa is drastically reduced when cutting with them.
Big Bear
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If all the ribs are shown, I copy the plans and glue the paper "templates" to wood, like many others do.
Some laugh, but scalpels are cheap, the blades are cheap, and they are LOTS sharper than out of the box #11 blades. Breaking/crushing balsa is drastically reduced when cutting with them.
Big Bear
Scalpels huh? Amateur surgeon? Heres ribs 8 & 9. Now I know why laser cutting is so popular.
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Scalpels huh? Amateur surgeon? Heres ribs 8 & 9. Now I know why laser cutting is so popular.
Never used a scalpel on anyone, had a couple used on me......... they DO cut balsa so much easier. Razor blades with a handle!!!! When I was building customer planes, time was important, and scalpels are quicker, over all.
I rough cut out the templates, staying about 1/16th from the line, and then sand them to the line with a block an 100 grit paper, much quicker than trying to cut them accurately.
Big Bear
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I understand that some sort of spray glue is used to attach the pattern to the balsa. Exactly what is it and where is it sold?
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I am going to have to use plans to make ribs. This is the one part I have never been able to do from prints. I always break the balsa at some point. What is the best method of making intricate parts in balsa from prints?
No one's mentioned stack cutting yet.
Make templates for the tip and center rib out of some suitable material -- i.e. linoleum, 1/16" ply, aluminum, etc. I've used ply, aluminum and 1/32" steel from an old microwave oven case. Aluminum sheet has the best balance (IMHO) of strength & durability, although the steel I'm using has the dual advantages of being free and having an attractive fake woodgrain finish. Drill holes in the templates on the horizontal centerline, beyond the line holes. Make them the same size as your wing jig rods, if you're going to use one.
Drill holes in the rib blanks, of the same size and spacing as your templates. I cheat and use an X-Y table on my drill press, because I have one, but there are other nifty ways to do this that don't involve expensive machinery. At worst you can use a template as a drill guide.
Stack the templates and one wing panel's worth of blanks on brass tubing the same size as the holes and the same length as the size of the stack, then bolt the whole stack together. Now carve, sand, saw, and generally make balsa scrap until the ribs and templates form a smooth block. Take it all apart -- voila! you have ribs for half a wing. Repeat once (or three times for a biplane), and you're done.
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I understand that some sort of spray glue is used to attach the pattern to the balsa. Exactly what is it and where is it sold?
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3M repositionable spray is the best - not sure where you can get it in the States tho.