I've seen posts that reference applying paper to fins for strength and a smooth finish. My question is exactly how to do this? What kind of paper and glue? Quanity of glue to use? Trim balsa after paper is applied? How well does the balsa and paper sand?

Thanks

You have a lot of choices.

I've used CA and silkspan, and yellow glue (carpenter's glue) and silkspan.

I've heard of others using white glue and good quality bond paper.

The trick is to apply the stuff after all sanding is done. Use the fin template as a pattern to cut out a "skin."

If the fin shape is simple, you can make a double skin that wraps around the leading (or trailing) edge.

Another possibility is to make the skin slightly undersized. This will leave the fin's edges exposed. You can cover them with seperate rectangular wraps.

Apply a thin coat of glue, apply the skin, and place between two pieces of waxed paper. Weight down with books and leave it be for a few days.

Follow up with some coats of slightly thinned glue.

Raw paper doesn't sand well, but if it has been "stiffened" with glue or filler you can work with it.

I've done this on a few models with some really good results.

It works best on scale fins. Usually scale fins have a diamond ore similar cross section which is relatively hard to sand accurately.

I use 110# cardstock and use straight out of the bottle white Elmer's glue but spread thin and evenly. I use a piece of plastic like a cradit card and squeegee it even on the surface.

I usually draw the fin in CAD and print the cardstock out first then I cut it to fit.

The balsa is cut "slightly" oversised then sanded to fit the cardstock when ther glue is dry.

The LJ II fins are "wedge" shapped and are made from R/C airplane trailing edge stock so all that was left was to add the leading edge. Trhe pic should show how they came out.

BTW, this was my prototype.

The great part about using this method is the simplicity. No more sanding after trimming the balsa to fit the paper. Just paint.

I will admit it doesn't work on every design.

It will work on teardrop shaped fins but it's harder to do.

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Zeke,

Some of the posts were using the paper-over-balsa technique more for the simplification in finishing it offers than for the reinforcement (although that is an added benefit). One method that I've started using, and which others have been using for a while now, is to pick up a package of full-sheet self-adhesive printer label stock from Staples, Office Max, Office Depot, etc. Use the house brand, as it does just as good a job and is less expensive. If you print the fin pattern onto the sheet first, you can peel and press this label onto one side of your balsa sheet, and apply a blank label to the other side. Rub the label down onto the wood thoroughly, but not so hard that you leave ruts or gouges in the surface. Cut through the sandwich from the printed side, using a sharp #11 and a steel ruler, then seal the outer edges with thin CA glue (do not coat the root edge -- you need this edge raw for the white or yellow glue to sink in). If you have a multi-piece fin, you can still apply a solid-outline label after the fin has been cut out and assembled. You simply print two labels -- one in reverse -- and carefully apply them on each side. Seal with CA, and give the outer edges a buffing with 220-grit paper to smooth them off.

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I just finished a Comanche 3. The thought of sanding and sealing all nine fins was overwhelming, so I used the paper method. I used some heavy bond printer paper and 3M Super 77 spray adhesive. I sprayed the adhesive on the paper and stuck the fin to it. I then stuck that to another piece of pre-sprayed paper and placed the "sandwich" under a weight for a little while. Then I used a rotary cutter to trim away the paper. The rotary cutter worked much better than a standard razor knife. After trimming, I sanded the edges.

It worked well.

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Zeke,

I just finished building 6 Fliskits Acme Spitfires that use the label paper technique for both body tube sections and fins.

I modified the fin "skins" posted on the Fliskits website so they would cover all but the fin root.

I think the attached photostrip shows the technique pretty well.

First photo in strip shows label paper design cut to shape, backing removed, sticky side up.

Fin edge is placed into position (note that in this example the root edge is facing the top of the picture and will not be covered) and fin is then "folded" onto label paper to make nice crisp edges. When completely wrapped, any overhang on the root is trimmed with an exacto.

I have used this technique frequently on other rockets. It is surprisingly durable and allows for designs not possible with painting.

Once attached to the rocket, I spray everything with several coats of Rustoleum Clear. The clear coat creates a "shell" which permeates and bonds the label paper very well.

Be aware that you should check whatever clear coat you use to make sure it will not make the inkjet-printed label paper run (I've had that happen with some versions of Krylon clear).

Also, be aware that when the clear coat is added, it tends to make any white areas somewhat translucent so whatever is underneath will show through (fin grain). I sometimes paint the underlying object white (or use white tubes) before applying the label paper.

Have fun.

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Thanks for all the info! I wondered how to handle the process of folding over the paper at each edge. In picture 3 and 4 on the Guss approach, there is an overlap on two sides. Is the overlap then cut parallel to each edge or the paper to be applied to the "up" side just laid over top the overlap?

How well does the self adhesive paper stick to the balsa wood? When painting, is the paper prone to blister in any of the processes described?

In any case, it sure looks like the paper method is superior both in strength and in producing a smooth surface.

I just finished a TLP Nike Ajax and the paper method sure would have helped!

Question: What are the advantages/disadvantages of self adhesive vs applying glue to paper, if any?

When Sandman makes his Nike Hercules model available, I'll use the paper process!

Thank you

Just laid over the overlap. Looks fine, and way better than leaving the fin edges undone.

The label paper sticks fine to the balsa, but it does need an overcoat.

I've never had the paper blister.

The self-adhesive labels stick well as long as they are rubbed down, and the edges are sealed so that they cannot pull up. The easiest way is with thin CA, which penetrates both the wood and the paper. Just remember to stay away from any root edges (fin-to-tube joints). You want the yellow (or white) glue to penetrate into the wood, and it cannot do this if it has been hit with the CA.

Blistering is usually a result of not firmly rubbing the paper down to the wood; it also happens when the label's adhesive is too old, or (if you're using plain paper with 3M77 spray adhesive) there isn't enough on the paper to adaquately hold it. If you see this happening before you've applied any primer, take a "T" Pin and poke a few tiny holes through the blister and apply thin CA. Let it wick through the holes and grab the paper from the inside. Press the blister back down before the glue "smokes", then sand the surface to eliminate any sharp ridges.

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Craig McGraw

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SAM 0044
AMA 352635

For my 4" diameter upscales I've either used 1/4" balsa laminated with heavy card stock or 1/8" ply cores laminated with 1/16" balsa that is then laminated with card stock. The card stock adds a lot of strength and eliminates a lot of finishing on the fins, i.e. no balsa grain to fill. I use thin coats of yellow glues and for each layer. I do both sides at the same time and wrap the fins in wax paper. Then I put them between two sheets of blue foam and throw a lot of weight on them for 24 hour min.

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