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Building Tips and technical articles. => Paint and finishing => Topic started by: Steve Thornton on March 24, 2015, 05:04:34 AM
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I sanded a 10" sheet of 1/8" balsa with 600 grit paper, to practice Monocote technique. no matter how smooth, I could not seem to get the 'Cote to adhere without the wood grain showing through. What am I doing wrong?
Steve
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To get a great Monokote finish requires as much work as a dope finish. All of the grain has to be sealed. Many use carbon fiber veil. I'm cheap and use 1/2 oz F/G cloth. Seal the weave with primer and sand it almost all of the model leaving only what remains to fill the weave of the cloth or nap of the veil. When the surface is smooth then you can cover it with film. Many also pre cover the wing with silkspan but you do not have to dope the wing after the silkspan is applied. An advantage of that is you can cover a wing in pieces to accomplish a complex finish and additionally film adheres tenaciously to silkspan so wrinkles or lifts are a true rarity.
This is only a brief synopsis of one method there are others. But you have to remember that the finish is the result of all of the preparation that goes before it.
Dennis
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I agree with Dennis there. You could also use Minwax polycrilic as a sealer, and no FG cloth. If that's not quite enough, what Dennis said is probably the best way to do it. I use 3/4 cloth on profile fuses.
I'll just add a little to making wing shapes with different colors also... I put the colors together before applying the monokote as one sheet.http://stunthanger.com/smf/index.php/topic,36529.0.html
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I read somewhere on the forum that after sanding you were ready to attach the 'cote...and it worked okay on the wings, but the fuse looks it was sanded with a file and covered with old carpet...maybe not quite that bad.
This is for the Baby Flite Streak and I'm concerned about weight. I used glass on a couple of FS Trainers, solid wings, and they look great and are tough as steel, but the weight may be restrictive. I also have some Polycriylic and I think I'll go that way. Should I use it on the LE and TE of the wings as well?
I have read many posts from both of you and you have answered many questions, thanks again!
Steve
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I read somewhere on the forum that after sanding you were ready to attach the 'cote...and it worked okay on the wings, but the fuse looks it was sanded with a file and covered with old carpet...maybe not quite that bad.
This is for the Baby Flite Streak and I'm concerned about weight. I used glass on a couple of FS Trainers, solid wings, and they look great and are tough as steel, but the weight may be restrictive. I also have some Polycriylic and I think I'll go that way. Should I use it on the LE and TE of the wings as well?
I have read many posts from both of you and you have answered many questions, thanks again!
Steve
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Get Faye Stilley's book.
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The trouble with wood is that it is a porous material. NO amount of sanding will leave a surface that is solid.
It may be smooth to the tough but without a filler to span the gaps it will always reveal its grain.
Just pointing it out.
Under a micro scope even many non-porus materials have a texture.
Usually from what ever method is used to make them flat...
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Jim is spot on. And depending on your grain, dictates just how much work you'll need to do for a good finish! Lol. I'm doing a SIG shoestring now and the grain is wide and deep! I've been sanding and sealing for hours and hours!
Steve, i would use the polycrillic on the LE and TE. Just treat it like primer and sand most away. Have fun!!
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One method I've used was to have tight somewhat hard sheeting for the wing, this usually doesn't need pre-covering. For the fuse and solid tail surfaces I have applied 1/2 oz fiberglass with balsarite for film. Let it dry for at least a day or two then apply the film with low heat (don't us a heat gun it will bubble the substrate/glass). This adds stiffness to the fuse and tail surfaces (flaps also) and is very smooth under the film.
Best, DennisT
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Read Faye Stilley's book. Problem solved. Oh, and follow his instructions.