Papering Balsa Fins?

Hi guys I'm hoping someone can provide some clarity... So I know its a good idea to paper balsa fins to help make sure they don't break under pressure and are more likely to survive an impact with the ground. What I don't get is the best method to do it based on x vs y? From reading around there seems to be a lot of different methods and not many people really go into details about why they do it that way. For instance one method seems to be to just paper the flat surfaces of the fin but not the edges, where others seem to wrap the paper around the whole fin from the front leaving only the trailing edge un-papered? Also I presume its better to paper and then sand your edges into shape rather than sand and then paper? Also should I be putting the paper on the fin and then putting the glue onto the paper so it soaks through into the balsa?

Also on a side note the instructions for the kit (vagabond) don't really seem to say anything about sanding the fin edges to add an airfoil? I was re-reading the model rocket handbook section and again it doesn't really seem to go into much detail about what works best for a given rocket type. For example for this type of rocket should I be trying to sand down into a rounded, streamlined, double-wedge, or bi-convex shape?

I've got a tutorial on the process of papering fins that make them extremely strong (compared to the ones I didn't paper during my first venture into rocketry). I've had papered fins survive impacts (things falling on them, etc.) that would have crushed unpapered ones.

You can airfoil if you want, but there isn't really a need for it. It can improve performance, but the amount on a low power rocket is probably not noticeable and I prefer to keep the leading edge on my lp rockets square for a bit more strength (also helps cut down on the dings/dents).

I use self-adhesive label paper (full sheet) and don't normally paper the edges. I then just run a quick swipe of wood glue on the edges and smooth down with my finger.

Try out different techniques and see what you like!

I'm certainly no see xpert but let's start with the last question first- rounding the leading and trailing edges will do just fine for sport flying. This will improve the performance of the rocket and is simple to do but it will fly just fine if you don't do it. An airfoil is difficult to do properly and good building technique will gain more performance than airfoiling fins will.

As for papering fins, you have seen the variety of techniques out there and you can just pick the one that you like best and give it a try. Personally, I like to wrap the paper around the leading edge. I first trace the fin, flip it on the leading edge and trace again so that I have a double image of sorts. I then cut the pattern slightly oversize, apply a thin coat of glue to one side of the fin and stick on side. I then apply glue to the opposite side and leading edge and fold the paper over the leading edge and bond it to the other side.

I almost forgot, yes, do any sanding on the fins before papering.

I hope this was of some help.

Thanks again for the advise guys Can anyone from the UK recommend a good glue stick to use? We don't seem to get elmer's glue over here and gorrilla dont seem to do a stick?

Whike I'm far from being in the UK, I'll suggest researching Titebond II wood glue. If you dont have any luck finding a source fro this, experiment with different wood glues (the yellow stuff). Some people in the States also use Aileen's craft glue. I have never used a glue stick so I don't have any suggestions there.

I have a friend that I'll check with Monday to see if they have any suggestions.

Screaminhelo said:

Whike I'm far from being in the UK, I'll suggest researching Titebond II wood glue. If you dont have any luck finding a source fro this, experiment with different wood glues (the yellow stuff).

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Hmm, why yellow glue? Seems like white glue would work fine for paper to wood, wouldn't have to worry about shrinkage. Gives you a bit more time before it sets up. Plus it's, well, white or clear, less of an issue with painting.

Is there a technical reason why I shouldn't use super glue / CA to do it? I have tons of it on hand and I'm struggling to find white wood glue in a store near me. They all only seem to sell kids pva or stuff like no more nails which i know is crap (says it will hold things like pictures up but doesn't...).

Since I use it for nearly everything, that is what I use for papering fins. I have so many glues, solvents, paints and and other assorted chemicals in my shop that the EPA would have a cow and I am glad that my workshop is not covered by OSHA. I find that multipurposing things makes life simpler for me.

As for CA, I imagine that it would work but not for me. I have ruined enough fins with it to know that I should steer clear of it for this purpose.

ziminar said:

Is there a technical reason why I shouldn't use super glue / CA to do it? I have tons of it on hand and I'm struggling to find white wood glue in a store near me. They all only seem to sell kids pva or stuff like no more nails which i know is crap (says it will hold things like pictures up but doesn't...).

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Try Aileen's white glues from the craft/scrapbooking stores. High quality and tends to be thicker. Stay away from "School Glue". I've been told that they changed the formula of Elmer's Glue All, but I am still using the old stuff so I don't know how the current stuff works.

nobody has mentioned paper types. Label paper yes, but no other paper types. I've papered with the Avery label paper, but didn't like it (Glue seems to give up after a while / doesn't quite stick to balsa). I've used the standard printer / photocopy paper (80lb bond) but feel it's a little heavy for our needs. And I've papered with tracing paper, light & thin but prone to wrinkles & the really big grains come thru. And finally, I have "Monokoted" a few fins..

I've used spray glue, white glue, yellow (aliphatic resin) glue, and relied on the glue on the label. White glue was the best result for me..

of course, there is also really thin sheets of ply to paper your fins with. You can get a 3-ply wood at 1/32" or even 1/64"..

In the end i ended up using printer paper and applying super glue to the top to let it soak through (at the time I was struggling to get ahold of decent white wood glue and had tons of super glue). I then added a bit of the super glue with added rubber to the edges to hopefully help with impacts It has come out ok and after a bit of sanding its feels fairly tough and has a nice smooth surface. I'm going to try following this (https://www.apogeerockets.com/education/downloads/Newsletter298.pdf) for painting which should help reinforce it further with the wood filler.

dr wogz said:

nobody has mentioned paper types. Label paper yes, but no other paper types. I've papered with the Avery label paper, but didn't like it (Glue seems to give up after a while / doesn't quite stick to balsa). I've used the standard printer / photocopy paper (80lb bond) but feel it's a little heavy for our needs. And I've papered with tracing paper, light & thin but prone to wrinkles & the really big grains come thru. And finally, I have "Monokoted" a few fins..

I've used spray glue, white glue, yellow (aliphatic resin) glue, and relied on the glue on the label. White glue was the best result for me..

of course, there is also really thin sheets of ply to paper your fins with. You can get a 3-ply wood at 1/32" or even 1/64"..

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I just tried FedEx shipping labels a couple months ago - the adhesive on them is *very* aggressive. No lifting so far on the one rocket I've used them on.

Chris

I use the Scotch white glue for scrap-booking. It's made for gluing paper, and sets very quickly. That, and regular office copier paper.

chrisudy said:

I just tried FedEx shipping labels a couple months ago - the adhesive on them is *very* aggressive. No lifting so far on the one rocket I've used them on.

Chris

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+1 on the Fed Ex labels. I've been using them for a while now and I like the results. The adhesive is quite strong I've actually had it pull up chunks of balsa when trying to remove it. I find if I use something like a plastic spoon to smooth it down it really sticks down good.

ziminar said:

Thanks again for the advise guys Can anyone from the UK recommend a good glue stick to use? We don't seem to get elmer's glue over here and gorrilla dont seem to do a stick?

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Basic aliphatic resin glue from a model shop works fine for me. Exact brand will depend on what your model shop has in stock. That PVA you found would work fine. This has the advantage over superglue that it doesn't dry quite as quickly so you have time to smooth out any wrinkles in the paper. It soaks into the balsa, further helping to make the fin stronger. But it can also warp the fin, so it's best to do both sides at once, then wrap the fin in greaseproof paper and put something flat and heavy on top of it - I usually put a book or table-mat onto the fin to provide the flat surface, and some random heavy object on top of that.

Edges can be a problem. They're the weak point; they're likely to be the areas where you didn't quite spread the glue, so they may not be as well stuck down, so they're where the paper may start peeling off. That's why I do the same as Screaminhelo - trace round the fin, flip it over across its leading edge, trace round it again, then cut out the combined shape and wrap it around the leading edge.

The best use for superglue is, when the PVA or aliphatic resin has dried thoroughly, apply superglue to the edges to seal them. Let it dry, then sand the edges to smooth down the superglue as well as make the edges round.

One other refinement which I've done on some fins is, after doing the tracing, flipping and more tracing, I cut out the shape, fold it, and cut off a portion of the trailing edge so that it won't now cover the fin all the way. Then I trace another pattern around the aft end of the fin, flipping it over the trailing edge to get a pattern which will cover both sides. This piece goes onto the fin first, followed by the main piece which goes over the leading edge. The net effect is that both leading and trailing edges are covered and the fin appears to have a control surface.

Root edge question (or topic of further discussion) when papering fins:

Do you bring your paper down to the root edge of eth fin (where it meet / is glued to the body tube)? Or do you leave the paper shy about a 1/16" or 1/8"? The reason being, is that your fillet is then attach to the wood core, rather than the paper wrap. (It actually grabs both the wood core & the paper edge..)

I've done both, and a 1/16" is more than suffice and allows for a good fillet transition. But then again, we are talking about an LPR rocket, and the butt glue of the fin is usually strong enough..

Referencing these threads:

https://www.rocketryforum.com/showthread.php?42250-Balsa-technique-question

https://www.rocketryforum.com/showthread.php?15260-Freezer-Paper!!

https://www.rocketryforum.com/showthread.php?12267-Question-about-using-Elmer-s-Fill-n-Finish

I sometimes have wrinkles with regular printer paper, due no doubt to a lack of refinement of my technique, but the freezer paper (aka "butcher paper" for us old country folks) mentioned in the referenced threads works great for me. I apply it wrapped around the leading edge, using white glue, with the treated side out. I've also tried it with Gorilla Glue - it worked, but since it expands on curing, it foams out at the edges and must be trimmed. It probably would inhibit subsequent white or wood glue attachment if that happened at the root edge.