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Building Tips and technical articles. => Building techniques => Topic started by: Don Curry AMA 267060 on September 27, 2011, 02:19:03 PM

Title: Laser burning
Post by: Don Curry AMA 267060 on September 27, 2011, 02:19:03 PM

I have been working on a Super Firecat purchased from Frank Macey in 2005. It is a laser cut kit. I pre sanded all the part before assembly to remove the scorching. After assembly and more sanding I coated the wood with Balsaloc, which is the adhesive used for the Litespan covering I am using. After coating the rib edges to wood turned black in spots again. There was no black anywhere after sanding and now the black refuses to leave after sanding again. Since the covering will be semitransparent the stains will show through. Anyone have any ideas?

Don

Title: Re: Laser burning
Post by: Randy Powell on September 27, 2011, 02:37:36 PM

You could try bleach. I did this once on a transparent finish where some of the wood was discolored. It worked pretty well. At least it evened the color out a bit.

Title: Re: Laser burning
Post by: Pat Johnston on September 29, 2011, 06:59:32 AM

Don.
How about painting the edges of the ribs with a contrasting color to make them show out.  This solves the problem of irregular coloration through the covering.
BTW, I use as little power on the laser as it takes to make the cut.  On 1/16" ribs, this is about 12-15% power, depending on the density of the balsa.  Much reduced ash that way.
Pat Johnston
Skunk Works

Title: Re: Laser burning
Post by: Don Curry AMA 267060 on September 29, 2011, 09:46:12 AM

I already have the Balsaloc on the rib edges which caused the color to show. The adhesive does not sand well so if I paint the edges and re-glue I am not sure of the adhesion between the layers of glue and paint when the heat is applied .

Title: Re: Laser burning
Post by: Tim Wescott on September 29, 2011, 11:10:40 AM

I'm not sure what you can do.  I'm pretty sure that what happened is that the carbon was in the wood, hiding down in the grain.  Then when you put on the Balsaloc it made the top layer of wood translucent and -- (expletive deleted).

Sanding out the dark spots and reapplying BalsaLoc is probably all you can do.  You may end up with little flat spots in your ribs everywhere that you have to do this, though.  Whether it's worth your while is your call.

Title: Re: Laser burning
Post by: Steve Helmick on September 29, 2011, 06:40:25 PM

1/64" x 3/32" balsa cap strips? Iron them onto the coverite stuff & apply more coverite stuff after sanding. Well, that's my 2 centavos.  H^^ Steve