abufletcher

Does someone have a neat trick or (homemade) tool for cutting diagonally through thicker balsa (say 4-6mm)? I'd like to be able to cut tapered balsa spars (for why, see my DrI thread) but I'm not having much luck cutting them square with my exacto knife. I always seem to end up cutting at a slight angle. And trying to sand them level with a sanding bar after cutting is next to impossible.

So imagine this situation. I need to make a balsa spar that tapers from about 3/8" down to 1/8" over a distance of about 20 inches. The taper is only on one side of the spar (thus forming a greatly elongated right triangle). It's critical that all the sides be square all along the spar. And I need to be able to make four absolutely identically tapering spars.

Any ideas?

willey

My Feedback: (32)

try clamping the piece between two pieces of hard wood and sand flush.

R8893

My Feedback: (20)

You could take the opposite approach and laminate the spar from three pieces of 1/8". Top piece 20" long, next one 14" last one 7"

Laird SS

A laminated spar would probably be stiffer than a tapered one made from one piece of wood.

abufletcher

Both great ideas! [sm=thumbs_up.gif][sm=thumbs_up.gif]

TFF

They have taper jigs in woodworking that hold the wood at an angle when cutting with a saw.

TFF

http://www.woodcraft.com/product.asp...&FamilyID=3184

Here is a picture of one you might make something like it on a smaller scale.

abufletcher

Ah! One problem with the laminated spar idea: I need a straight surface rather than a "step" because this side will get a 1/64 ply cover. I could probably make up a "sandwich" of some kind which would hold the spar stock and let me sand down to the edges of the jig. A couple of flat bars of aluminum and some bolts ought to do the trick.

Since I'd need 24 of these tapering spars on the DrI box spars, making up a jig would be worth the effort.

Boomerang1

I used tapered spars on both the tail & wing of my B-36. I juat stripped them to the largest size needed then used a razor plane to taper them. - John.

BobH

My Feedback: (2)

I agree a razor plane and then some sanding is an easy way to go. Balsa's soft so it shouldn't take long.

Chad Veich

My Feedback: (60)

I use laminated spars quite often on tapered wings where the tip ribs get too thin to maintain the original spar thickness. Works great and is much stronger than a single piece spar.

Sethhunter

Another idea to consider, laminate a wide plank and rip the individual spars from it. For example, laminate 1/16 or 1/32 thick 4" wide sheets, plane or sand the wide face of the plank to remove the steps, then rip 1/4 wide spars off of it. You should get 10 spars from a 4" wide stack, depending on your saw kerf width.

dbarrym

My Feedback: (47)

Bingo....I made a copy of this tool years ago for ripping laminated CF/balsa spars to final size for bagged sailplane wings in lengths from 24" up to 48". If you have access to a table saw, use a very fine tooth "smooth finish" blade meant for laminates and/or veneers and your spar will be straight, accurate, and smooth enough not to require any sanding before use. Stack your wood blanks and make them in one pass.

You can also use a large bandsaw but you'll need to set up a suitable length table and fence, and the spars will require some finish sanding (cut them 1/32 or so oversize and sand to final finish with a block).

Barry

abufletcher

I appreciate all the suggestions everyone had and they definitely got me thinking. I ended up making jig that allowed me to sand the cut balsa spars to a uniform taper. Mission accomplished!