How do you paper fins to make them stronger?

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Mushtang

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I've recently seen the method for double gluing fins repeated on here, and in the past I've seen the method for avoiding bubbles in launch lugs. I've asked for, and received, tips for various things in this forum so I thank all of you that offered the good advice.

Today's question is what are the steps for papering balsa fins? Is there more to it than just gluing paper on both sides and painting?
 
I've done this a few different ways:

1) tissue paper and dope - you know the kind that makes your head spin! I mean the Aerogloss dope used for making RC airplanes. This works, but it is really stinky. Tissue paper is really only useful for small models (mmx) which might need more support but the thickness of paper just doesn't make sense.

2) white glue thinned with water and computer paper. Thin the glue a little so is spreads better. Put a coat on the balsa, then rub the paper into it. Though I've done this, I don't really like it. white glue shrinks and can pull the paper into the grain.

3) avery label paper. I use full sheet labels with permement or "pressure activated" glue. This works fantastic! Cut the label a little larger than the fin, peel the back, and press into the fin. Work slowly applying from one side to the other so you don't get air bubbles. After you rub it for a bit to activate the glue, trim the excess with a knife. You can gently sand off the excess. Sometimes it doesn't stick all that well right at the edge, so I will coat the exposed edges with thin ca to incourage the bond.

Good luck.

kevin
 
I have papered the last 20 rockets ive built from scratch, One thing ive noticed is that a mixture of white glue (elmers) and water works great.

1-Dont make the mixture to watery
2-DO NOT put to much on the fins or the paper will wrinkle.
3-I have used the paper for my transition from the fin to the tube and some I have acually overlaped (one seam is easier to hide then two seams)
4-I paper my fins AFTER mounting them on the tube !
5-Any defect in the fin will usually show through the paper
6-Dont be afraid to leave alot of overlap on the fin edge as its going to be trimed, I cut out TWO templates with alot of overlap one for each side..
7-after the paper is dryed (make sure its 100% cured and dried or else it will be bad bad bad) I take a razor blade and trim the overlaps off. and sand down the seams
8-I airfoil the leading edges and then I sand the paper off until I reach the edge of the airfoil.


Have fun !!!!

airfoil.jpg

bad fin.gif

leading edge.gif
 
I like using Elmer's glue all for the skins. Never tried mixing it with water or applying the skins while the fins are mounted to the rocket?
 
I like using Elmer's glue all for the skins. Never tried mixing it with water or applying the skins while the fins are mounted to the rocket?

I dunno... that sounds like the HARD way to do it...

I mean, there's more than one way to skin a cat, so if the technique works for you, go for it... but then there's little sense in making things harder than they need to be...

I've seen NO need to thin the Elmer's white glue. It's pretty thin already. You want a VERY THIN layer of glue anyway. If the glue layer is too thick, the paper will absorb too much water from the glue and get "mushy" and will get waves in it that will turn into wrinkles as you try to burnish the paper down tight to the fin surface. Extra water is the last thing you want on your balsa as well, ESPECIALLY if it's thin, (3/32 or less) because as it's absorbed into the fin it may well warp it. The key is a THIN, even coat of white glue on the paper, then wrapping it over the fin, and burnishing it down TIGHT and squeezing ALL the excess glue out from between the paper and wood. This actually makes the strongest joint, anyway, because excess glue actually weakens the joint between the paper and wood.

Doing the papering after the fins are on the rocket just seems more difficult as well, for no good reason that I can see... It's POSSIBLE, sure, but why do MORE WORK for the same result?? Papering first just makes it SO much easier to cut/trim/dress the edges of the fins... that's why I prefer the "White glue n printer paper" method to avery labels... a white glue/paper/wood joint is permanent... label adhesives, not so much... the fin can be sanded to the EXACT airfoil you want before papering, and the paper applied directly to the fin and rolled over the leading edge, which is subjected to the most force in flight trying to rip the paper away from the fin... no loose joints, CA hardened or otherwise, along the leading edge to turn loose from the slipstream ripping past in flight... and no "paper fuzzies" after sanding in the airfoil after the paper's applied, and having to clean that up.

Imperfections in the fins will show through, but only if they're bad enough. If you have dinged up balsa, switch to cardstock for papering the fins... it will cover the dings. Thicker white glue (undiluted with water) will help in this regard too, IMHO... I don't use thinned white glue, just 'straight' white glue, and I don't have grain or dings showing through... Besides, a couple good coats of primer and some 220 sanding followed by 440 should eliminate ANY show-thru's anyway...

Like I said, if it works for you, go for it, but I think it's taking something simple and making it complicated...

Later! OL JR :)
 
I dunno... that sounds like the HARD way to do it...

I mean, there's more than one way to skin a cat, so if the technique works for you, go for it... but then there's little sense in making things harder than they need to be...

I've seen NO need to thin the Elmer's white glue. It's pretty thin already. You want a VERY THIN layer of glue anyway. If the glue layer is too thick, the paper will absorb too much water from the glue and get "mushy" and will get waves in it that will turn into wrinkles as you try to burnish the paper down tight to the fin surface. Extra water is the last thing you want on your balsa as well, ESPECIALLY if it's thin, (3/32 or less) because as it's absorbed into the fin it may well warp it. The key is a THIN, even coat of white glue on the paper, then wrapping it over the fin, and burnishing it down TIGHT and squeezing ALL the excess glue out from between the paper and wood. This actually makes the strongest joint, anyway, because excess glue actually weakens the joint between the paper and wood.

Doing the papering after the fins are on the rocket just seems more difficult as well, for no good reason that I can see... It's POSSIBLE, sure, but why do MORE WORK for the same result?? Papering first just makes it SO much easier to cut/trim/dress the edges of the fins... that's why I prefer the "White glue n printer paper" method to avery labels... a white glue/paper/wood joint is permanent... label adhesives, not so much... the fin can be sanded to the EXACT airfoil you want before papering, and the paper applied directly to the fin and rolled over the leading edge, which is subjected to the most force in flight trying to rip the paper away from the fin... no loose joints, CA hardened or otherwise, along the leading edge to turn loose from the slipstream ripping past in flight... and no "paper fuzzies" after sanding in the airfoil after the paper's applied, and having to clean that up.

Imperfections in the fins will show through, but only if they're bad enough. If you have dinged up balsa, switch to cardstock for papering the fins... it will cover the dings. Thicker white glue (undiluted with water) will help in this regard too, IMHO... I don't use thinned white glue, just 'straight' white glue, and I don't have grain or dings showing through... Besides, a couple good coats of primer and some 220 sanding followed by 440 should eliminate ANY show-thru's anyway...

Like I said, if it works for you, go for it, but I think it's taking something simple and making it complicated...

Later! OL JR :)

JR I don't thin the glue with water or apply the skins after the fins are mounted....I'm in agreement with you.
 
From Luke Strawwalker's post
"I grabbed some printer paper and cut it into pieces sufficient to cover both sides of each fin at once, folded over the leading edge, with a healthy margin all the way around."

For me this seems to be the best way to go. Rolling the paper over a rounded leading edge makes for an easier application and prevents delamination on the edge most exposed to the windstream.
I've used both spray adhesive and glue. The spray adhesive gives you a second chance to apply the paper covering but you get more lifting on the edges. The raised edges can be hit with CA and sanded.
With white glue you've got one shot at getting the paper or cardstock covering in place. The paper cover stays down on the edges better with white glue.
 
From Luke Strawwalker's post
"I grabbed some printer paper and cut it into pieces sufficient to cover both sides of each fin at once, folded over the leading edge, with a healthy margin all the way around."

For me this seems to be the best way to go. Rolling the paper over a rounded leading edge makes for an easier application and prevents delamination on the edge most exposed to the windstream.
I've used both spray adhesive and glue. The spray adhesive gives you a second chance to apply the paper covering but you get more lifting on the edges. The raised edges can be hit with CA and sanded.
With white glue you've got one shot at getting the paper or cardstock covering in place. The paper cover stays down on the edges better with white glue.


I have used this technique before and it works well especially if your leading and trailing edges have an airfoil sanded into them, but on certain shape fins it doesn't work as well...no biggie just go back to the other method and not roll them.
 
From Luke Strawwalker's post
"I grabbed some printer paper and cut it into pieces sufficient to cover both sides of each fin at once, folded over the leading edge, with a healthy margin all the way around."

For me this seems to be the best way to go. Rolling the paper over a rounded leading edge makes for an easier application and prevents delamination on the edge most exposed to the windstream.
A development of this is to make the paper smaller than would fit round both sides of the fin, and cut a second piece which will fold over the trailing edge and fill the gap. The first piece should slightly overlap the second. The result is that both leading and trailing edges are sealed, and the fin looks as though it has an aileron.
 
I have used this technique before and it works well especially if your leading and trailing edges have an airfoil sanded into them, but on certain shape fins it doesn't work as well...no biggie just go back to the other method and not roll them.

Yeah, for elliptical fins or fins with a compound angle on the leading edge (like strake-fins, sorta like those on a Semroc Hustler) it's very difficult to do the 'fold over the leading edge' method... since most fins we use have straight leading edges, though, it's usually not a problem.

For fins that are, I think I'd use two sheets of paper and white glue and sandwich the fins between them, burnishing the paper down tight against them.

Later! OL JR :)
 
I have used this technique before and it works well especially if your leading and trailing edges have an airfoil sanded into them, but on certain shape fins it doesn't work as well...no biggie just go back to the other method and not roll them.

The first rocket on which I papered the fins was a Semroc BatRok. lots of curves, impossible to do with that single sheet method. :)

I will have to try it on something with a non-curved leading edge.
 
oh, and make sure you ge the paper on nice and smooth. Burnish it down and make sure you get the air bubbles out. In other words, don't do what I did:

Fin Preparation

:blush:
 
I've done this a few different ways:

3) avery label paper. I use full sheet labels with permement or "pressure activated" glue. This works fantastic! Cut the label a little larger than the fin, peel the back, and press into the fin. Work slowly applying from one side to the other so you don't get air bubbles. After you rub it for a bit to activate the glue, trim the excess with a knife. You can gently sand off the excess. Sometimes it doesn't stick all that well right at the edge, so I will coat the exposed edges with thin ca to incourage the bond.

Good luck.

kevin

Does the label paper impart the same strength to the fins as glued on paper? I had always assumed that labels that can be stuck on can be "unstuck" at least somewhat easier than something bonded differently. For purposes of providing a good finished surface free of grain markings, seems like label paper would be perfect, just the right amount of adhesive exactly where you want it.
 
In the past, I've always used thinned wood filler to finish my fins.

After reading this and other posts, I went ahead and papered the fins on my Quest Harpoon (without filling). There are 12 fins on that rocket, and I discovered two things:
1) The grain shows through more than filler.
2) It takes a heck of a lot longer than filler.

Read on... I'm not knocking papering, I'm just stating my observations. :p

I'd like to know how much added strength does papering really impart? I have had "filler finished fins" crack along the balsa grain on a hard landing... Does papering the fins substantially lower the risk of this happening?

I am now working on my next build (a Quest Navaho). I've already applied filler to the fins (I fill and sand while they are still on the carrier sheet, to make my life easier), and am probably going to give papering another shot. I will use a better quality paper this time (presentation weight vs eco-copying weight), use white glue vs carpenter's glue, and wick the outside edges in thin CA. (and I'm not going to worry about papering the "strakes")

My goal is to build good looking rockets that fly well, but that I haven't invested so much time into building that when (not if) they crash or vanish, I'm crushed. Right now, that takes about 6 hours per rocket, spread over a week, with papering adding another hour or two, (and an extra day)...
 
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1) The grain shows through more than filler.
2) It takes a heck of a lot longer than filler.

My goal is to build good looking rockets that fly well, but that I haven't invested so much time into building that when (not if) they crash or vanish, I'm crushed. Right now, that takes about 6 hours per rocket, spread over a week, with papering adding another hour or two, (and an extra day).
I use self stick label paper for the purpose of making the fin easier to finish, not necessarily for strength, although I believe they are stronger.

Papering with label paper adds a little time to fin prep before assembling but there is no filling and sanding of fins afterward. So the only filling and sanding I do is balsa nose cones and/or transitions and they can be started first and be done with by the time the rest of the rocket is done. If you are building a rocket with a plastic nose cone, you can skip that altogether.

Do not use label paper marked "removable" or "re-positionable". I have had some that say "permanent" and others that say nothing.

Make sure you wipe off all sanding dust before papering. I have used the "fold over leading edge" method as well as the "paper each side separate" method and both work good.

Make sure you rub the label down real good and I CA the edges (except root edge, of course).

When priming, don't put the first coat on too wet. A couple of light coats a few minutes apart is better than one heavy coat.
 
I have found the exact opposite. :p
Papering is faster, no grain shows, and the overall result is smoother and easier to finish. I assume its stronger, but I have no empirical evidence.
I guess it one of those things where YMMV.
:D
 
I've had label paper bubble up during extremely hot weather at launches. Maybe I should use a monokote iron next time to see if that helps.
 
I have found the exact opposite. :p
Papering is faster, no grain shows, and the overall result is smoother and easier to finish. I assume its stronger, but I have no empirical evidence.
I guess it one of those things where YMMV.
:D

Exactly the reasons I do it... it is somewhat stronger, especially on smaller fins, but I've still had a bigger fin crack over, though it was an easy repair... and thicker cardstock would have probably prevented that break (it was papered with regular printer paper). Thicker cardstock would solve any 'grain showing thru' problems as well... (can't even figure out why the grain would be showing through, except perhaps because the poster who mentioned this used YELLOW glue instead of WHITE glue... because yellow glue shrinks considerably as it dries, I suppose it's possible that it pulled the paper down into the grain more and allowed it to "show through"... using yellow glue also explains a lot of the problems he described about it 'taking a long time" and being hard to apply and all... white glue is MUCH easier to use (and just as strong if not stronger in this application) than yellow glue...)

All I can add is that it works for me, and works extremely well... others may have different opinions which is perfectly fine... :) YMMV...

Later! OL JR :)
 
I've had label paper bubble up during extremely hot weather at launches. Maybe I should use a monokote iron next time to see if that helps.

I ironed the self-adhesive label paper on my Super Alpha fins after I applied it, with the thought that the heat would help the adhesive really "get all up in there". No adverse effects noticed yet - about two years later.
 
Thicker cardstock would solve any 'grain showing thru' problems as well... (can't even figure out why the grain would be showing through, except perhaps because the poster who mentioned this used YELLOW glue instead of WHITE glue... because yellow glue shrinks considerably as it dries, I suppose it's possible that it pulled the paper down into the grain more and allowed it to "show through"... using yellow glue also explains a lot of the problems he described about it 'taking a long time" and being hard to apply and all... white glue is MUCH easier to use (and just as strong if not stronger in this application) than yellow glue...)

This was helpful, thanks.

As far as the grain showing, is was apparent from the time I started burnishing the paper down, before the (yellow) glue even set. This time around, with the filler pre-applied, I'm sure the finish will be flawless... :p

In the grand scheme of things... I like to fly my rockets, and they are going to get grungy from the BP and dinged up from the landings, so its all kind of in vain anyways :D Get the fins on straight, and try not to screw the rest up too bad, and get it in the air....
 
This was helpful, thanks.

As far as the grain showing, is was apparent from the time I started burnishing the paper down, before the (yellow) glue even set. This time around, with the filler pre-applied, I'm sure the finish will be flawless... :p

In the grand scheme of things... I like to fly my rockets, and they are going to get grungy from the BP and dinged up from the landings, so its all kind of in vain anyways :D Get the fins on straight, and try not to screw the rest up too bad, and get it in the air....

Interesting... I don't know why your grain would show through paper... that's a new one on me... unless you had some balsa with some positively HUGE grain in it or something... I've NEVER had that happen.

Seems to me that if you have to fill the fins first with filler and then paper, it's just a waste of time... if you're going to use filler, just use the filler and go with that... if you're going to paper, do some experimentation until you find a method that works... maybe use less glue... (less is more when it comes to papering fins... the thinner the glue layer, the stronger the bond, so long as the paper or wood is uniformly and very thinly covered with glue that is).

I've done both and both methods work... it's largely a matter of choice as to which you use...

Later! OL JR :)
 
Aleene's Quick-Dry Tacky Glue is my adhesive of choice for this task. It is far less watery compared to Elmer's Glue-All, yet it spreads out easily. I use a flat spreader to squeegee the glue across the paper covering, which creates a smooth, even layer of glue. Doing so avoids wrinkles and bubbles. Wrinkles occur in areas that absorb too much moisture, which can happen when you drool out a puddle of glue in the middle of the paper before spreading it out, or when you drizzle out a spiral of glue around the surface. (That last technique works well for gluing, say, two pieces of wood together, but not for attaching a thin, very absorbent and easily deformed material like paper.) Bubbles occur because there were dry spots on the paper or areas where the glue was too thin. Applying the glue with a spreader avoids both issues.

By the way, as implied above, you apply the glue to the paper and then press it onto the wood (or press the wood onto it). Do not try to do this by applying the glue to the fin, because it will soak into the wood too quickly and unevenly. (This can also lead to bubbles.)

I would advise against using wood (yellow) glue for this. White glue works extremely well and with provide a strong, durable bond when it has been properly applied (spread out in an even layer on the paper covering).

There are differing opinions about this next point, but personally, I do not recommend using spray-on adhesive to attach the paper. It is difficult to use it to get an even coating of adhesive onto the paper. You are very likely to get lumps and dry spots, which lead to wrinkles, bumps and bubbles.

If you are feeling adventurous, try using freezer paper. Apply the adhesive to the uncoated side. You end up with fins that are not only toughed by the paper, but which also wear smooth microthin plastic coatings. :cool:
 
If you are feeling adventurous, try using freezer paper. Apply the adhesive to the uncoated side. You end up with fins that are not only toughed by the paper, but which also wear smooth microthin plastic coatings. :cool:

+1 on the freezer paper.

While I rarely paper fins, I've noticed using freezer paper this way makes for a nice surface ready to be primed.

And as mentioned above, avoid Carpenters wood glue. It tends to shrink down and you see your grain.
 
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