Papering with Epoxy

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aviserated

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No results needed, it is common sense that this is no heavier after finishing (primed, sanded and painted). I could easily weigh and lie about it, but not worth it. If i were building for super lightweight (not strength) i would use primer only to finish fins.

Here are the sanded flat fins ready to be cut out and edges sanded.
DSCF0530.JPG
 

heada

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Common sense says that a glue like white glue or yellow glue, that dries and thus loses mass, would be lighter than epoxy that cures (cross linking long chains) and doesn't lose mass if we assume the same mass of added glue/epoxy. The difference could be slight, but the glue based will be lighter assuming the same weight of added glue/epoxy before drying/curing. It doesn't answer if the strength per mass added is greater with glue vs epoxy, that would involve destructive testing.

On models that are weight sensitive, adding heavier fins to the aft end could change stability enough to make a rocket unflyable.
 

dhbarr

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"I don't need to measure things, my gut tells me how much tiny stuff stuff weighs."

Please note I'm not criticizing your build technique our outcomes. But accuracy matters even if you yourself aren't chasing an ultralight build.
 

Bill S

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I don't appreciate aviserated calling me a liar. Of course a fin with epoxy is going to be heavier than one with wood glue. Since he won't post his numbers, I call bullshit. I'm out of here.
 
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prfesser

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Common sense says that a glue like white glue or yellow glue, that dries and thus loses mass, would be lighter than epoxy that cures (cross linking long chains) and doesn't lose mass if we assume the same mass of added glue/epoxy. The difference could be slight, but the glue based will be lighter assuming the same weight of added glue/epoxy before drying/curing. It doesn't answer if the strength per mass added is greater with glue vs epoxy, that would involve destructive testing.

On models that are weight sensitive, adding heavier fins to the aft end could change stability enough to make a rocket unflyable.
I fully agree with the last statement.

I also agree that glue that loses mass when it dries is likely to weigh less than epoxy. Added to that is the fact that thin laminating epoxy soaks into balsa much more than does most white or yellow glue, so even without the paper and with scraping off excess epoxy or white glue, there ought to be a weight change. However...

...For me, sense is rarely common. ;) I don't know how much liquid actually evaporates from each type of glue. Carpenter's glue is almost certain to have a greater solids content than white glue, though not as great as epoxy which is 100% solids when cured, as you say. I'll accept Bill S's values but wouldn't mind seeing more data. As I told a young woman who wanted to give up dating after a bad experience, most scientists like at least 20 data points in order to have a reliable value. So keep going! 😁

Best -- Terry
 

prfesser

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I once measured TBII as losing about 1/2 its weight when drying. For what it's worth.
Thank you! More education, and more data, is almost always better than less. It sounds a bit high but opinions cannot argue successfully with fact.

Best -- Terry
 

John Kemker

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This discussion thread has me seriously considering using Aeropoxy laminating resin and paper to paper the fins on my LOC Goblin. The fins are already installed in the rocket and I'm in the process of applying fillets. I'll paper after the fillets, but before the sanding of the fillets to see how that turns out.
 

CalebJ

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Why not then, at this point, just go with .25 or .5oz cloth & glass it with proper finishing resin.. lighter & stronger than paper, and the finishing resin levels out nicely..
Wouldn't you need -less- epoxy with fiberglass than paper anyway?
 

heada

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Fiberglass cloth acts like a sponge to epoxy and really soaks it up. Paper should absorb much less. If you use the right paper, you could get close to the strength of fiberglass but with less epoxy soaked in. I've used 40# kraft paper, 60# kraft paper and washi kozo (Japanese mulberry paper) in tip-to-tip on some Estes kits and while not quite as strong as epoxy/fiberglass, its much stronger than 20# bond paper with yellow glue.
 

dr wogz

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Depends on teh weight of teh cloth. Hence why I say .25oz or .5oz cloth really thin, really light. A skim of resin, then lay this on & squeegie it in place. no need for weights & all the other stuff..

Done this on R/C boats & R/C planes..

get the kit:

and their .56oz cloth
 

aviserated

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I found the easiest method is to epoxy hand selected balsa sheet. Then cut out fins after paper/epoxy has cured flat. I found some really stiff 1/16" balsa that works perfect.

Water in Wood glue sometimes causes fins to warp during papering. Epoxy does not cause warpage.

Epoxy is much more simple to use.
 

prfesser

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Why not then, at this point, just go with .25 or .5oz cloth & glass it with proper finishing resin.. lighter & stronger than paper, and the finishing resin levels out nicely..
I tried glassing the fins of my Interceptor G with 0.5 oz cloth. Far more work than if I'd used paper and epoxy. The finished fiberglass surface still must be filled and sanded and filled and... At least, I had to do so.

I bought a second Interceptor G kit and will cover the fins with paper and epoxy.

While we're on this topic, what other kinds of paper might be stronger? I was thinking of vellum or some other drafting paper. How about the paper that is used to wrap sticks of butter? I don't know how it would take up epoxy but it's darned hard to tear, compared to other paper. Tyvek is incredibly strong but doesn't seem to like to play with epoxy. :(

Best -- Terry
 

dhbarr

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47 lb bond gloss should be pretty strong, but no idea on strength vs. weight. Scrim paper could be interesting.
 

Daddyisabar

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I'm old and lazy and Purdy stupid, but ain't the bond only as strong as the weakest layer of paper on your low power Kraft tube? I just score up the tube, use big sheets of lable paper cut to rough size, slap on unsanded balsa, no warping ever, Xacto trim, seal edge with CA, put a drop of CA on each end of root edge with tacky glue in between, slap on the fin and give a quick fillet of tacky glue all at once. Four finished, light and strong fins put on in only minutes. I can still brag low power bulletproofing to the fellers! No pain, no pain. Ain't as cool as glassin', but that is fer the real top men. Low power bulletproofing ROCKS! Finding speed of balsa ROCKS HARDER 🎸 😎!
 

Daddyisabar

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The best is breaking the fin off and reattaching the large torn paper surface area with super thin soaking CA. CA for fins, NEVER I SAY! I just tell em it's an ancient Chinese Secret. CALGON Take me away! You have to be old as dirt to understand this silly post. Love to see the steam come off the paper! Breathe in those super toxic CA fumes, cough hard and eyes water. Beg to use cool, non toxic, heavy epoxy! Just a little dog breath smell ain't gonna hurt! No silly and uncomfortable gloves, I'm LPR bulletproofing!
 

aviserated

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20 pound cotton paper maybe? Cotton paper is known for its long term durability. Money is printed on cotton paper. I have not used it with epoxy, so I do not know.

Lots of ways to finish fins...so what ever floats your boat.

Bob Smith industries makes a very good sandable finish resin also. Most hobby shops sell it and prefer it over ZPoxy.
 

John Kemker

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20 pound cotton paper maybe? Cotton paper is known for its long term durability. Money is printed on cotton paper. I have not used it with epoxy, so I do not know.

Lots of ways to finish fins...so what ever floats your boat.

Bob Smith industries makes a very good sandable finish resin also. Most hobby shops sell it and prefer it over ZPoxy.
Where would I find said cotton paper?
 

DigBaddy

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I've been using 24# resume paper (cotton) with Titebond II and it seems to work very well. I can sand leading edges to shape without any of the paper peeling off the balsa/basswood. I press them for a few days after gluing and they come out perfectly straight and solid. 1/8" balsa this way really seems strong, 3/32 basswood even better.
 

John Kemker

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I've been using 24# resume paper (cotton) with Titebond II and it seems to work very well. I can sand leading edges to shape without any of the paper peeling off the balsa/basswood. I press them for a few days after gluing and they come out perfectly straight and solid. 1/8" balsa this way really seems strong, 3/32 basswood even better.
Thanks! I'll check for it. (I used to work in a print shop. I should have remembered about resume paper!)

EDIT: Hmmm....100% cotton is expensive, but 100% linen is less expensive. I wonder...
 

rklapp

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With papering, the fin is more likely to snap off the cardboard. This is easily fixed with Quick&Thick. The fin tip has suffered damage despite reinforcement with thin CA.

1620671418872.png


Another aspect is that glue dries and epoxy cures. The glue is more flexible and epoxy cracks.
 
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Dane Ronnow

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I've been using 24# resume paper (cotton) with Titebond II
I was planning on using 24lb. copy paper and Elmer's Glue All, but I'm a little concerned about Glue All getting too sticky, too fast, when applied in a very thin coat. Does TBII stay wetter longer? Also, is shrinkage with TBII less than with Glue All?
 

heada

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TBII has an open working time for about 5 to 10 minutes with the time being on the shorter end when spread thin. There is shrinkage with TBII but only noticeable when thick. When spread very thin like you would have when papering fins, there is no noticeable shrinkage.
 

DigBaddy

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I was planning on using 24lb. copy paper and Elmer's Glue All, but I'm a little concerned about Glue All getting too sticky, too fast, when applied in a very thin coat. Does TBII stay wetter longer? Also, is shrinkage with TBII less than with Glue All?
What @heada said 😃
 

neil_w

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I've always found Glue-All to have more working time than TBII. Both shrink plenty, enough so that 20 lb copy paper will conform somewhat to the grain in the wood (so the finished fins will still benefit from filler/primer). Great bond, though, and strong.

I still don't get why working time is even an issue. You spread the glue (to paper or fin, depending on your preference), and then attach the paper to the fin. This takes no more than 1 minute, tops; well within the working time of either of these glues. What am I missing?
 

Dane Ronnow

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What am I missing?
After reading a number of your comments on this and other threads, I'd say, "Not much."

Referring to the fin template below, my plan is to use a one-piece skin, cut with a .125 inch overhang on leading, tip cord and trailing edges, leaving the fin tab bare, as well as .187 inches of the root cord for the fillet.

I would apply the glue to the paper and squeegee most of it off, then place the leading edge of the fin on the center of the skin and pull both sides of the paper up the sides of the fin, pulling slightly away from the leading edge to keep the skin tight. I would then lay the fin flat and roll the skin from the leading edge to the tab using a 1/2-inch wooden dowel (like rolling biscuit dough) to remove wrinkles/bubbles. Flip the fin and roll the other side. Then press flat on a glass surface with books stacked on top.

Looking at that as steps 1, 2, 3 and 4, it seems like it would go quickly. But with me, it's never quick. Or simple. If I can get an extra 2 or 3 minutes or so, it works to my advantage. That's all.

I should also say that as I work through processes such as this in my mind, I have a tendency to make it much more difficult than it probably will be when I actually do it.

Test Rocket fin template.JPG
 
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