Sanding paper laminate fins
 

Hello all:
Quick question for you as I've searched the forum and a little unsure as to what grit to use on my newly papered balsa fines. I used Elmers multipurpose white glue, typing paper and sealed the edges with super thin CA. All looks good but unsure as to how not rip the paper! Thanks in advance, Jeff

What is the purpose of this sanding?

Shaping an airfoil?

Sanding off primer?

Thanks for your reply, Stephanj:
I think your questions answered my own. I have just a bit of glue residue left from the CA. My next step would be to prime and paint directly over the fin paper. Take care, Jeff

You mention ripping the paper. Did you glue the entire area of the paper? Or only the perimeter?

Normally, for pre-prime sanding, I use 220 grit, maybe 320.

Doug

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"220, 221, whatever it takes."

http://www.imdb.com/title/tt0085970/quotes

Hi Doug:
Yes, I first smeared a very light coat of elmers onto the fin. Once dried overnight I then sanded the edges then applied the CA. I've since applied duplicolor primer/filler and the fins look pretty crappy as in I've got a few of the horrid airpockets. I'm going to allow a good dry time, sand and see if I can just put on some sanding sealer first, then F and fill and call it done! Hope this makes sense! Take care, Jeff

Have you got a MonoKote iron?

Pop that blister with a T-Pin, several places, then heat up the iron. Press it down flat onto the fin for a few seconds, then check it.

If the white glue has completely dried, then heating it up will liquefy the glue briefly, allowing a complete bond. When you take the iron up and it solidifies again, you'll break the fin trying to get the paper off.

Which leads to another trick -- apply the glue in a thin layer to both the paper and the fin, then let them dry first. Use the iron trick to make the final bond.

I used this trick to apply 1/16" balsa wing skins onto foam cores...

Craig has some interesting information there, and is worth a try. I've heard of guys making homemade body tubes using that method, of applying the glue, allowing it to dry, winding the tube around a suitable mandrel, then ironing the tube to set the glue and seal the layers together. It would probably work at least as well for papering fins.

I go for a more "standard" approach. Sand the fins to the airfoil desired. Cut paper a little over double the size of the fin, and apply then apply a VERY THIN layer of white glue to the paper and spread it out into a very thin, even coat. Apply the fin to the paper, so that the leading edge of the fin is toward the center. Apply another very thin layer of glue to the exposed surface of the fin, and fold it over the leading edge of the fin onto the other half of the paper, and press the fin down against the paper firmly. Using the round end of a Sharpie marker, gently "burnish" the paper down tightly to the surface of the fin, starting at the center of the leading edge and working out to the root and tip edges, and from the leading edge center to the trailing edge of the fin. Using the barrel of the Sharpie marker like a kitchen rolling pin helps as well, especially if you have a little more glue on the fin or paper than you should have. Work gently but smoothly and you'll remove 100% of all air bubbles and make the paper smooth and slick as glass on the fin. Flip the fin over and repeat for the other side.

Allow the fins to dry overnight, and cut off the excess paper with scissors to within about 1/4 to 1/8 inch of the fin edge, and then using a SHARP hobby knife blade, gently shave the edge of the paper down flush with the root, tip, and trailing edge of the fin. The paper is wrapped over the leading edge tightly so the slipstream won't tear it off the fin or cause the paper to come loose. No CA applications are required, but can be done if you want, but then the CA will require sanding down. The fins are ready to use as-is with NO CA, so that's how I do it. I usually "dress" the edges of the fins by drawing them gently across a sheet of 220 grit sandpaper at a SLIGHT angle to the edge, to use the paper to 'shave off" any excess hairs of paper and make it completely and perfectly flush to the edge of the fin.

The fins are now 100% ready to glue onto the rocket, and can be glued on using a standard double-glue joint with regular yellow carpenter's glue, and can be filleted as you desire (I prefer Titebond Moulding and Trim Glue here-- it's an absolute SNAP to fillet with and does a perfect job!)

The fins thus papered take a regular primer coat or two used to prep the rocket for paint and sanding quite well. I sand the primer with 220 grit and then move on to 400 grit wet/dry paper dampened with water to keep the paper from clogging. Works like a champ and produces fins that look just like plastic when you're done!

Good luck! OL JR :)

OL JR:
I can't thank you enough for this beautifully written guide: its just what I needed to hear this morning! I picked up some aerogloss filler last night at my LHS and so for the paranoia and toxicity are enough to want to make try papering again! Take care, Jeff

Hi Craig:
No, no irons here except for the ones for pants and shirts! Would this work if no moister is used?