Do you agree with the method Tim VanMilligan uses in the video above? (Skip to 2:00)
Also...he seals the edges with thin CA. You don't recommend this?
What I do is basically pretty close to what Tim's doing... notice he mentions in the video what will happen if you use too much glue, and mentions "taking 90% of it off by squeegeeing off with his finger" before applying the skins...
There's a few differences, though. First, Tim's using yellow wood glue. Now, I know from experience that YWG will work in this application, and some folks here swear by it, but I *prefer* white glue for this application... why?? Because PVA glue (white glue) is a better adhesive for bonding paper to wood... and especially for paper to paper bonds. The properties of the white glue also help... First, white glue doesn't tack up as quickly when spread into very thin layers, which is EXACTLY what you need for this application... YWG (aliphatic resin) tends to get dry and very tacky or even gummy VERY quickly the thinner the layer is spread... then it'll start rolling up in little balls, what Dr. Zooch calls "funky glue putty" (which he actually uses in some steps in some of his kits, intentionally making the stuff by rubbing YWG between your fingers until it stiffens up and starts balling up...) ANYWAY, the only real solution is to put on a THICKER layer of glue to keep it from gumming up or tacking up too fast, which as previously mentioned, is counterproductive in this instance, because a THIN layer of glue is the real key to making papering the fins work. Too much glue=too much moisture, and the paper wicks it up faster and more of it than the wood... since the paper has a thinner, more open "grain" and more surface area and space between fibers for the moisture to wick into... plus thick layers of glue trapped under the paper on top of the wood will form those "ridges" he talks about in the video, or wrinkles, and that basically ruins the whole purpose of papering the fins in the first place. The more glue you have, the more moisture you have, and hence the more chance of warping you have... using a thinner layer of WHITE glue, which stays a little bit damper a little longer and in a little thinner layer, means less glue, a thinner layer, a bit more working time in applying the thin layer and thinning it out evenly, and then joining to the paper, and less chance of warpage or paper wrinkling...
Another difference is, Tim is pre-cutting the paper into two seperate layers, one for each side of the fin. This is honestly just doubling the work required to paper the fins for no purpose that I can see. Now, I'll admit, using the "taco" method on square-edged fins is a little trickier than doing it on a rounded or wedge shaped fin leading edge... but honestly, unless you're doing a scale or semi-scale missile that is SUPPOSED to have a square leading edge (like the TLP Maverick I built) basically you SHOULD be rounding over AT LEAST the leading edge... it takes all of about 2 minutes per fin to do... I can airfoil a fin into a teardrop shape with a rounded leading edge and tapered trailing edge in about 3-4 minutes, so it's not like it's some HUGE deal to do... and it REALLY improves the performance of the rocket from a drag standpoint! Just rounding the leading edge helps drag probably 50%... and it's VERY easy to do... just wrap 220 grit sandpaper over the leading edge and run it back and forth a few times to take the "corners" off the edge of the wood... easy-peasy... and of course it makes papering the fin super-easy as well, because it allows you to ROLL the fin over once the first side is glued to the paper...
SO, WHY glue the fin down to a sheet (or partial sheet) of printer paper or cardstock and roll it over the leading edge to glue the other side down?? Well, first off, think of your fin on the rocket in flight... it's sticking out into the wind, and at burnout that slipstream of wind may be ripping over that fin at several hundred miles an hour, even with a low power rocket... that's tornado wind speeds PLUS... way past even most hurricane wind speeds! And that's just on the TYPICAL LPR/ MPR rocket! A streamlined minimum diameter bird with a high-thrust or long burn engine might be going TWICE that speed or more, even approaching the speed of sound (740 mph at sea level standard pressure or thereabouts). You've glued paper to the surface of your fin, and the wind is ripping past that fin, trying to catch the edge of that paper, get under it, and RIP IT OFF the fin... BUT, by rolling the paper, as a SINGLE PIECE, over the leading edge, you've done two things: 1) you've eliminated ANY "register" (edge) for the wind to pull and tug at and try to rip loose and start ripping the paper off the fin, and 2) you've eliminated well over 25% of the work of papering the fin...
"How's that??" you say?? Well, look at Tim's video... see he's having to do extra work that I don't... he's having to cut his "skins" out of the paper to the shape of the fin ahead of time, slightly oversize, and then he's having to pretty carefully align them with the balsa core of the fin and then apply them. Doing the "taco" method of gluing the balsa fin down to the paper, applying more glue to the paper where the other side of the fin will fold over onto it (or onto the exposed upper surface of the balsa fin core, either way works just about as well, though I find that I can get a much thinner and more even layer of glue applying it to the paper the fin will fold over onto, myself, BUT BOTH METHODS WORK!) There's NO pre-cutting the paper "skins" as Tim has to do, (unless it's just to cut the sheet of paper roughly into halves or quarters depending on the size of your fins to minimize the number of sheets of paper you use to do the fins and reduce waste), and IMHO it's much easier to apply the glue evenly and thinly to the paper and then press the fin down onto the glue-covered paper-- which again, reduces the amount of glue moisture soaking into the fin, thus reducing the risk of warpage (which isn't usually a problem unless you're doing VERY thin finds, like 1/16 balsa or below, which is VERY prone to warpage, even from moisture in the air at times! For balsa that thin, you'd probably want to switch to a non-water based adhesive for this purpose, probably Super-77 spray adhesive or rubber cement or something like that, to eliminate the risk of warpage from the water in the white or wood glue... OR, one COULD apply the super-thin layer of white glue to the paper, allow it dry, then HEAT SET the paper onto the fin by ironing it on like you would with Monokote airplane covering film... PVA (white) glue can be thermoset once dry-- meaning the glue can dry, but if you heat it up again it will "melt" and then re-set, bonding the two parts together, just like Monokote and other thermoset model airplane covering films do...
Also, look what Tim does later on in the video... he's having to trim ALL FOUR side of the fin... leading edge, trailing edge, tip edge, and root edge. Papering over the leading edge TOTALLY ELIMINATES having to do ANYTHING as far as trimming or sanding this leading edge is concerned... you've killed two birds with one stone by using the "taco" method-- eliminated the edges for the air to catch and work on tearing the paper off, and eliminated the need to trim those edges down, sand them, etc... Also eliminated the need to go back and "seal" the edges with ultra-thin CA... so you've not only saved yourself a minimum of 25% of the work of trimming the fin, shaving the paper down, and sanding the edges to dress them and remove stray "paper hairs" and such, you've got a superior and stronger surface with no edge for the air to catch, and no need for the CA glue to help "shore up" the bond between the paper edges and the balsa to make sure the wind doesn't start pulling them loose... Less materials, less time, better results... I like that!
Now, I noticed in the video Tim just "presses down" the skins onto the fin... which works okay, BUT, you'll get MUCH better results if you carefully BURNISH the paper down gently but firmly to the surface of the fin,and squeeze ANY EXCESS glue out of the space between the paper and the wood... what is "excess glue"?? Simple... ANYTHING that is liquid enough to flow out from under the paper when you apply smooth even pressure to the paper and press it down to the wood. Don't worry, you WILL NOT squeeze out *ALL* the glue no matter how hard you press... when you apply the glue to the surfaces, it INSTANTLY starts soaking into the grain of the wood and grain of the paper... (and yes, paper DEFINITELY has grain! Read the paper modeling forums if you don't believe me!) The glue's moisture soaks into the spaces in the paper and wood fibers and takes the glue adhesive with it deep into the surface... this glue WILL NOT come off the permeable surface no matter what... (impermeable surfaces like glass or plastic is something else, which is why PVA and YWG don't work on these surfaces!) This "embedded" glue then starts forming little polymer chains reaching up from the surface the glue is applied to. When you press another surface down onto the glue (permeable surface like wood or paper) the glue's moisture wicks into the tiny pores and spaces in the grain and takes the adhesive in that surface as well... forming little "chains" reaching up from that surface. As the glue cures, the solvent (water) evaporates, bringing the remaining adhesive into closer proximity, forming little chains that bond to the two surfaces, locking them together... the thicker the glue layer, the longer these 'chains" are, and also the more likely they are to flex or break under a load... that's why thinner glue layers are stronger than thicker glue layers... and "slobbering the glue on thick" does NOT make a stronger joint-- usually quite the opposite, indeed it makes it WEAKER! (Speaking of the physical bond here, not of fillets which add MECHANICAL or STRUCTURAL strength from using the glue as a "bonding filler" as it were, increasing the surface area of the bond and the physical strength of it by adding material).
Anyway, point is, when you start "burnishing" the paper down tightly to the balsa of the fin, the excess "moist, liquid" glue squeezes out ahead of the burnishing tool... it "flows" across the surface between the two layers (paper above and wood below) until it's either 1) wicked into the wood or paper or 2) squeezed out around the edges... This brings the paper glue "chains" and the wood's glue "chains" into closer proximity, and they "link up" very quickly, forming shorter, tighter, stronger "chains", meaning the paper is bonded down EVEN STRONGER than it would be otherwise...
SO, in flight, with the leading edge completely covered with paper that then is "draped" over the surface of the fin toward the trailing edge over either side of the fin, tightly bonded to the wood, and burnished tightly TO ITSELF AT THE TRAILING EDGE of the fin, (if you "teardrop" shaped the fin, you can cut the paper JUST PAST the edge of the wood and the paper will remain glued TO ITSELF with NO exposed edge of the wood along the trailing edge...) There is basically NO WAY the paper can turn loose from the fin... less edges exposed for ground handling, wind, landing impacts, or whatever to start working the paper loose from the fin... You CAN CA the tip and traiing edges of the fin if you WANT to, but I've not seen ANY need for it whatsoever...
Now, shifting gears a bit... I know some guys RAVE over using label paper for fins... and if that works for you, great... go for it... no right or wrong here... BUT, *I* have a few issues with the label paper thing for myself, and I think the points are logical and bear examination-- then decide for yourself... First, label paper is something you have to specifically go out and buy at an office supply store... not "commonly available" (that I've seen) at the local mega-mart... Second, the adhesive-- it's not a particularly strong or PERMANENT adhesive... lets face it... work with anything "labeled" that's been around for a while, and you'll see corners coming up, edges dogeared or peeling, or the thing dries out and the label simply gets to the point it is falling off... NOT what I want to happen to my rocket. Third, while it's POSSIBLE to do the "taco method" with label paper, it's not as AMENABLE to that application method as other forms of paper... and the weaker adhesive means you're basically running even more risk of the paper turning loose from the fin... if from nothing else the paper wanting to "unfold" from the tight roll over the leading edge, and since label adhesive usually remains *somewhat* gummy or soft (and usually when it DOES dry out *completely* it turns to dust and turns loose of what ever its adhering) this risk in increased. There's also the issue of paint solvents or whatnot affecting the adhesive of the label paper... maybe a non-issue, maybe not... but with white glue we KNOW it isn't... Fourth, using label paper pretty much GUARANTEES you'll have to run all the edges with CA just to "lock down" the label paper to the fin-- basically we KNOW that the label paper adhesive itself is NOT a trustworthy bond long-term, especially with the wind trying to rip the label off, so we "head it off at the pass" by gluing the label paper down with CA around the edges trying to forestall the possibility of the paper turning loose and ruining the looks of the rocket or the finish after a couple flights or with a few month's or year's age... So it begs the question, WHY use something with such a crummy adhesive in the first place?? Why not just save the trouble and use an adhesive we KNOW will make a good bond, because that's what it's made for... IE PVA...
Okay, SOMEBODY's gonna slam me for writing a "book"... but there's a lot to consider... Tim's method and what I do are very close, but the differences I hope I've spelled out for you will make sense and heck, if you give them a try, you just might like it... IF you want to do it a different way, well, that's entirely YOUR decision, and there's no right or wrong about it... different things work better for different people, or for different jobs... for instance, the label paper thing is PROBABLY the better method for papering VERY THIN fins that are 1/16 inch thick or less... 1/8 and 3/32 fins, I've had NO problems with white-glue laminating, BUT, the thinner the balsa, the more prone to warpage, and the more the water in the glue will affect it. SO, switching to a pre-applied, non-water base glue (or at least "very gummy" non-"wet" glue like label backing adhesive) would help solve that problem... of course it adds a few, like having to CA all the edges down to "lock" the paper onto the fin...
Here's the original thread where I describe papering fins after having a lot of folks ask about it and repeatedly describing everything... so I did it as part of a build and documented it with text and pics for a reference material... not as neat as Tim's videos, but hey... I don't run a rocket company... LOL
https://www.rocketryforum.com/showt...a-Build-Thread&highlight=Zooch+Vanguard+Eagle
Anyway, hope this helps clear things up and maybe gives you something to think about...
Later and good luck! OL JR