Best way to paper long fins?

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Bill S

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I've been working on a new rocket, with long fins, and have decided that I'd like to paper them to strengthen them up, particularly at the top section. The fin assembly is 16" long, which I am thinking may be a bit tricky. The fin edges will be square (not rounded). Any suggestions as to the best way to paper this fin assembly? I was thinking just plunk it down on the paper, trim a little larger than the fin (except on the root edge, which would be flush), make 2 pieces and glue it, working fast.

I haven't had much success with printer paper, as it wrinkles and shows surface defects too well once it shrinks down. I have had better luck with thicker card stock (65lb), but I also don't have any pieces that big (I have 8.5x11" pieces). I did find a roll of paper at Hobby Lobby that I'm going to check out (24" x 100 feet).

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Sooner Boomer

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Why not just use two pieces of paper? I think as long as one piece covers all the jpined balsa, it should work. You might have a small line showing where the two pieces of paper meet, but a bit of putty and some sanding should fix that. Or use lighter weight paper that's commonly available in the length you need?
 

cbwho

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I just (black)papered a rather large fin.

The tricks:
1. White glue the paper not the wood.
2. Smooth paper on wood with fingers
3. Use a spare paper sheet and an iron to flatten/activate the glue.
4. If the fin warps apply iron

The hot iron will reactivate white glue. I used it to get out a warp too!

I remember office supply stores had 17 inch paper or something like that.
 

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Bill S

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I found some rolled paper from Hobby Lobby that looks like it'll do the job. 18" wide x 50' long, $8.

CBWHO: did you put the glue on the paper, leaving it on the work area, then put the balsa fin on top, pressing down? Or did you wet the paper and pick it up, draping it over the fin on the table?
 

cbwho

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I found some rolled paper from Hobby Lobby that looks like it'll do the job. 18" wide x 50' long, $8.

CBWHO: did you put the glue on the paper, leaving it on the work area, then put the balsa fin on top, pressing down? Or did you wet the paper and pick it up, draping it over the fin on the table?
Since the fin is huge, I placed it on top. There was some bubbles to my dismay but I remembered someone mentioned ironing so I grabbed our regular clothes iron and an extra sheet of paper as a temporary buffer, warmed it up and presto magic, flat as can be. I also used it to get the warp out perfectly. :)

Normally on smaller regular fins, I place the fin on top in an angled fashion by leading edge and then using fingers smooth away from leading edge.
 

afadeev

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I've been working on a new rocket, with long fins, and have decided that I'd like to paper them to strengthen them up, particularly at the top section. The fin assembly is 16" long, which I am thinking may be a bit tricky. The fin edges will be square (not rounded). Any suggestions as to the best way to paper this fin assembly? I was thinking just plunk it down on the paper, trim a little larger than the fin (except on the root edge, which would be flush), make 2 pieces and glue it, working fast.
Yes, good plan.
One single sheet of paper, shape of the fin outlined on it, and glue (TBII for me) spread evenly across the target area, and 1/4+" beyond the target.

I gave up on aiming to be flush with the root edge, since that would require perfect aim during application.
Once the paper attaches to the large surface area of the balsa fin, it 'grabs', and you will not be able to move it without wrinkling or tearing (BTDT). Thus, I expect some error in aiming, and spread the glue a little beyond the target area. Then cut-off or sand-off overhangs after everything is fully dry (12-24 hours later).
If you want to keep edges square (painting those will be a PITA), consider trimming overhangs with a cutting blade right after the glue starts gelling (1-2 hrs?), then stick the fin back under the press until if fully dries.

I haven't had much success with printer paper, as it wrinkles and shows surface defects too well once it shrinks down. I have had better luck with thicker card stock (65lb), but I also don't have any pieces that big (I have 8.5x11" pieces). I did find a roll of paper at Hobby Lobby that I'm going to check out (24" x 100 feet).
Yes, try slightly thicker paper (don't go full card stock, as it will make fins too heavy and effect CG).
There are different qualities of printer paper, and the cheaper stuff is the thinnest and wrinkliest.
Consider buying something of slightly higher quality and weight, and do NOT flood it with glue. Put down just enough glue on paper to spread over the entire target area (multiple finger passes), then remove any puddles (with a finger), then mate paper to the balsa fin. Do both sides as quickly as possible (to avoid warping) and place it under an object heavy enough to keep it from warping while glue fully dries.

I found table cutting mats to work great for longer sci-fi fins that would not fit under a book. You can easily position all fins under the mat at once, and pull them in/out for trimming at will.

The Screaming Eagle build thread I did last year has a few relevant illustration pictures that might of some help:

On the Estes Shuttle pictures below, you can see the areas that got papered (wings) and those that did not (fuselage). On the finished model picture, you can see residual balsa grain showing through the fuselage (after multiple rounds of sanding/painting/sanding/etc.), while the wings are nice and smooth.
1614975395480.png 1614975422979.png

HTH,
a
 
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BABAR

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Lots of ways to skin a cat or a fin.

I am also of the “apply glue to paper” school.

key to getting a thin layer is actually a KEY, in this case a plastic hotel card key. If you travel much you may have a bunch of these. I use it like a squeegee, applying glue to the central aspect of the paper and then squeegeed outward. I usually use an old magazine or a junk mail catalogue behind it, after I do one fin I wrap the top sheet with all the displaced glue off and I have a new sheet for the next fin.

once paper is on the fin, To press it down WITHOUT tearing it with my bare fingers, I put wax paper over the paper and press on the fin Paper through the wax paper. I also keep it in wax paper when I stick it in a book with non glossy paper. Since your fin is too big for a book, you could put in wax paper and out that between several sheet of newspaper, then underneath something heavy and flat. You need something absorbent to wick away the moisture.

haven‘t tried the iron yet, does that dry it faster?
 

Bill S

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I tried to paper the long fin. What a fiasco. I used Elmers School glue on the suggestion that it would be easier to work with and scrape off. I did one side, flipped it over and the fin was already warping. I hurredly papered the second side, and put under some parchment paper and heavy books. Checked it the next day, lots of wrinkles. I recalled that using an iron would work to get out the wrinkles, so I tried that. It worked moderately well on the wrinkles, but it also caused the fin to develop a bow from the fin base upwards, like a smile, rendering the fin useless.

I will not use the school glue again, that's for sure.

I looked at using the thicker card stock I have, but the sheet isn't long enough. In any event, it adds so much weight to do it with that, that I said nope.

In the end, I decided to skip papering on these long fins; its too much trouble.
 

Ted Cochran

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You might try diluting yellow glue with water and brushing it on with a paint brush. You'll also get more working time that way. I've also had luck using a wooden wallpaper seam roller to smooth out wrinkles after applying the paper to the fin.
 

afadeev

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I used Elmers School glue on the suggestion that it would be easier to work with and scrape off. I did one side, flipped it over and the fin was already warping.
The bad: Elemer's school glue dries way too fast, as you had found out.
The good: it is water soluble (actually that's also bad for rocketry), so take the damaged fin into the bathroom while someone is taking a shower, and the humidity will dissolve the glue and help you peel the paper off. It will be messy, but salvageable.

I hurredly papered the second side, and put under some parchment paper and heavy books. Checked it the next day, lots of wrinkles. I recalled that using an iron would work to get out the wrinkles, so I tried that. It worked moderately well on the wrinkles, but it also caused the fin to develop a bow from the fin base upwards, like a smile, rendering the fin useless.
You can fix the warping, if you choose to go that rout, by:
1). Exposing the fin to either water or Windex/ammonia (even better - spray on top, let it sink in).
2). Optionally - scrape the crappy layer of poorly glued paper off the surface
3). Put the fin under press, let it dry. It should come out straight.

You might try diluting yellow glue with water and brushing it on with a paint brush. You'll also get more working time that way. I've also had luck using a wooden wallpaper seam roller to smooth out wrinkles after applying the paper to the fin.
The more water you introduce to the fin, the more it will warp.
Thus the recommendation to apply glue to the paper, not the fin. Ideally, 2 pieces of paper at once, then apply both to each side of the fin in quick succession.
This is trickier to do with large sci-fi fins, so working with a slow curing glue (e.g.: TBII), helps.

I will not use the school glue again, that's for sure.
Good call.

In the end, I decided to skip papering on these long fins; its too much trouble.
Your choice.
 

cbwho

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I tried to paper the long fin. What a fiasco. I used Elmers School glue on the suggestion that it would be easier to work with and scrape off. I did one side, flipped it over and the fin was already warping. I hurredly papered the second side, and put under some parchment paper and heavy books. Checked it the next day, lots of wrinkles. I recalled that using an iron would work to get out the wrinkles, so I tried that. It worked moderately well on the wrinkles, but it also caused the fin to develop a bow from the fin base upwards, like a smile, rendering the fin useless.

I will not use the school glue again, that's for sure.

I looked at using the thicker card stock I have, but the sheet isn't long enough. In any event, it adds so much weight to do it with that, that I said nope.

In the end, I decided to skip papering on these long fins; its too much trouble.
The iron will get rid of the frown and make that fin flat. Trust me. Have the iron on the hottest setting. It will warp back and forth a bit, but you'll get it flat. I got the wing/fin on my 2nd Leo Space Train perfectly flat. It's a huge surface for me.


Also white glue allows do overs. Simply run the fin under hot water, the paper will peel away. Then wipe off with paper towels, then I put it in between paper to dry (making sure all the original paper and glue is removed).

As for white glue being bad for rocketry since it's water soluble, simply seal the rocket. I brush water based outdoor polyacrylic on the inside and around the engine bay after completion since I launch in snow.
 
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H-MINUS

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I’ve had good luck with 3M Super 77 spray adhesive on low power rockets. I have not tried it on fins as large as you are attempting.
 

Bill S

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Curious, who suggested that?
I believe it was Babar and Scott 650 I got the idea from.

CBWHO: The fin warped like a smile vertically. Pretend you are holding it against the body tube and attaching it. It warped vertically, not horizontally (which would at least be fixable in theory). I got so disgusted that I threw the fin away in bits, shall we say.
 

Bruiser

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I'll just stick with avery label paper and thin CA. No warping to worry about and a great surface to paint.

-Bob
 

mbeels

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haven‘t tried the iron yet, does that dry it faster?
Yes.

The iron will get rid of the frown and make that fin flat. Trust me. Have the iron on the hottest setting. It will warp back and forth a bit, but you'll get it flat. I got the wing/fin on my 2nd Leo Space Train perfectly flat. It's a huge surface for me.
I'll second that.
 

neil_w

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I'll just stick with avery label paper and thin CA. No warping to worry about and a great surface to paint.
For very long fins that require multiple sheets, I've had a hard time getting a smooth seem between the sheets. Not sure why. My unsuccessful attempts have included CWF followed by filler/primer. I think red Bondo might be next.

But yeah, I'm a big fan of label paper where you're not explicitly looking to maximize strength.
 

rklapp

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