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Author Topic: Best Way of Cutting Balsa pieces?  (Read 881 times)
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Vaughan
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« on: September 13, 2017, 04:24:58 AM »

Hi Guys
I'm new here and I'm starting to build my 1st RC Sailplane. I have the plans printed and I'm about to go about cutting the wing formers and wondering what the best way is? So, I thought I'd ask those who've been before me.
I thought the best way might be to cut them out with scissors and then glue them onto the piece of Balsa and 3mm Ply that I will be making them out of. Then, use my Scroll Saw to cut the pieces. Then, I thought that weight may be a pre requisite and that all that paper may add up so?Huh?

Can anyone tell me their best way?? Thanks from Australia

 Vaughan
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p40qmilj
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« Reply #1 on: September 13, 2017, 06:37:46 AM »

 Grin nothing works like a lazer

jim Grin
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packardpursuit
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« Reply #2 on: September 13, 2017, 07:06:02 AM »

When all the ribs are the same, I like to stack cut and sand to shape. Good band saw and sander make it a pleasure. Balsa sheet(s)can be glued together with plain clear dope as the adhesive. When shaping and sanding is done, brush on lots of pure acetone or dope thinner to separate the ribs.

It's also possible to stack and drill many rib blanks so they can be bolted between two plywood rib templates and finish sanded.

Or a template of ply or aluminum or cardboard or...Huh can be placed over your balsa sheet and traced with a ball point pen. BP pen ensures ribs will be sliglghtly oversized for hand cutting and stacked and pinned together for group sanding. I like to cut spar notches with the template, so a piece of spar stock can be fit in thr stack, so that all the ribs have common point of reference.

When ribs are different (tapered wing etc) and the rib spacing is equal distance apart, one can stack and sand between root and tip templates, thus imparting a rough (but close enough)approximation of individual rib development. Careful spar  notching is possible to ensure everything key's in proper order. Final sanding after assembly with T-bar sanding stick will reduce any high edges.

Paper rib outlines (from a plan) can be temporarily fixed to sheet bals with spray adhesive rubber cement. Just enough for a heavy tack. Cut paper/balsa sandwitch to printed line, then separate paper from balsa part before assembly. Brush on rubber cement works too.

finally, one can make copies of whatever parts on a plain paper copier. Place the image face down on the balsa  and then rub the back of the paper with an acetone soaked cotton ball swab.  This will transfer the lines from the paper to the balsa. You may have to experiment with the amount of acetone applied. Too wet and the lines can turn out fuzzy. OR you can dry transfer the same images with application of a hot iron, instead of acetone.
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Vaughan
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« Reply #3 on: September 13, 2017, 07:12:16 AM »

Thanks for your detailed answer and inside information Packardpursuit,
I will start the effort tomorrow and report how I go.

Thanks!
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fred
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« Reply #4 on: September 17, 2017, 12:54:32 PM »

Or use a glue stick to stick printer paper images to rib blanks . Removal is easy just dampen the paper and it peels off.
 I find image transfer, acetone or heat to produce fuzzy and imprecise lines.
 Also  one can leave the paper on the finished rib  as a bit of reinforcement (think plywood).. Useful for keeping the ribs from splitting at a V low weight penalty.
 But in that case.... watered white glue  is stronger /longer lasting
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Vaughan
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« Reply #5 on: September 17, 2017, 01:21:46 PM »

Cheers Fred!

I'm frustrated at the moment waiting for delivery of scroll saw blades. Typically, I bought the Scroll Saw from the Multi National "Bunnings" who are happy to sell the Saw but fail to carry the blades for that saw.

So, I've had to order them from a Brisbane supplier and awaiting postage. I will eventually post the results. Thanks again!
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kukailimoku
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« Reply #6 on: September 18, 2017, 01:33:50 PM »

I used to use the glue-the-paper-to-the-rib method but was never happy with the results. Using the pattern to make a template out of thin ply and then stacking the ribs for shaping and sanding changed the world in a big way for me.
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Scratch
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« Reply #7 on: October 07, 2017, 05:29:13 PM »

Like Vaughn, I'll be starting my first balsa scratch build from plans.
Wonder what the opinion might be concerning the use of vellum paper for making copies of ribs and formers.
Cut out the vellum copy and use a glue stick (restickable) to attach the copy to balsa.
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Crabby
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« Reply #8 on: October 07, 2017, 05:42:27 PM »

Boy easy gets harder everyday!
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« Reply #9 on: October 07, 2017, 09:08:14 PM »

When it comes to wing ribs (only) I made up a set of Simplex rib templates and easily slice my ribs from them. They give an airfoil with the high point at about the 40% point but I have never seen a difference in the flyability of the airplanes using them. At the small Reynolds Numbers we fly at, it doesn't seem to matter much.
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« Reply #10 on: October 08, 2017, 12:07:13 PM »

When transferring lines from a Xerox copy transfer the image to the balsa using Xylene.  This is a much better solvent to use for this operation as it releases the ink very well but does not make it run.  I got mine from Home Depot years ago.
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I used to like painting with dope but now I can't remember why!    Steve Fauble
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