Balsa technique question

[pepe]

Is this the right way to treat balsa parts? Two coats of wood filler,two coats of sanding sealer, two coats of primer, two coats paint and two coats of clear gloss . I sand between all coats and let each coat cure for 24 hrs. So as you see it takes me over a week to do even a level 1 rocket Is my method overkill and do all steps need a 24 cure time? thanks

 

[emckee]

I'd say whatever works for you. If you're going for the best possible finish on your rocket, you're probably heading in the right direction.

Personally, I'm usually OK with a 20/20 rocket, so I'll sand, glue, then paint. I usually do two coats of paint (sanding after each) and one or two of clear-coat, but no filler, sanding sealer or primer. Yeah, you can see the wood grain through the paint when you're holding the rocket, but mine usually aren't display pieces anyway.

I have found that papering the fins does (what I reckon to be) about the same job improving the finish as filler and possibly sealer, while improving the strength of the fin, so that might be a better way to go.

Other schools of thought?

 

[Micromeister]

Is this the right way to treat balsa parts? Two coats of wood filler,two coats of sanding sealer, two coats of primer, two coats paint and two coats of clear gloss . I sand between all coats and let each coat cure for 24 hrs. So as you see it takes me over a week to do even a level 1 rocket Is my method overkill and do all steps need a 24 cure time? thanks

Generally the Right way is the Way you feel most comfortable with applicating the materials you've found work best for your particular type of model building.

My personal preferrence for most Balsa applications is a coat of Minwax Wood hardner, then 3 wet coats of Cheapy Auto grey primer (the cheaper the better). repeat step 2 with another 3 wet coats after about 30minutes tacking time. Allow model to set overnight to 3 days depending on Humidity. Sand with 240 til all grain & seamlines vanish. if wood or paper are reached before the grain is gone repeat step two and allow to dry overnight Sand with 320 until all grain and seam lines are completely filled. apply matte white base coat. check for blemishes sand with 320 if found if not apply base color coat and finish color coat(s).
Haven't used a rattle can clears on my finished models in more then a decade. Much prefer a coat of Pledge with Future for Highest Gloss, then a coat or two of Nu-finish auto polymer.

But as mentioned earlier whatever floats your boat is whats "Best" for each individual.

 

[Rocketbuilder]

A technique that I've recently found works for me is to laminate the fins in tissue paper and white glue, place them under heavy books to prevent warping, sand with 400 grit, coat with thin CA (the cheap kind from Harbor Freight), and sand again with 400 until smooth. This results in glass smooth fins that are stronger than non-laminated balsa, but still very light.
I know I read about the CA coating technique on here somewhere, I think in one of Luke Strawwalker's novels posts, and combined it with tissue paper lamination for strength-- the tissue paper also helps fill the grain, so you have less sanding to do and it doesn't take as much CA.
This process usually takes a couple of days, just because of the glue's drying time.

 

[luke strawwalker]

Is this the right way to treat balsa parts? Two coats of wood filler,two coats of sanding sealer, two coats of primer, two coats paint and two coats of clear gloss . I sand between all coats and let each coat cure for 24 hrs. So as you see it takes me over a week to do even a level 1 rocket Is my method overkill and do all steps need a 24 cure time? thanks

Yeah, I'd say it's overkill... here's what I do, and it works perfectly for me...

First, you need to fill the grain on the balsa. You can do this in several ways. For nosecones, due to their round, complex shape, usually the thing that I do is apply ultra-thin CA (pink bottle stuff from Hobby Lobby, otherwise "water thin" CA will do) outdoors to the cones from the shoulder to the tip, letting the cone "drink in" as much CA as it wants. This hardens the balsa somewhat and seals off the pores. Don't get it on the shoulder of the cone or transition that goes down into the tube if you can help it, and of course don't glue the cone to your fingers, or anything else. Set it down on wax paper to dry. It can get hot from the CA reaction, and the fumes are NASTY, so do this outside. It'll dry in about 30 minutes or so and be ready to sand smooth with 220 grit sandpaper. Don't worry about getting it perfectly smooth, just sand all the "grit" and roughness off it from the CA treatment.

For fins, I prefer PAPERING them. Cut your fins from the balsa sheet, stack sand them to identical size/shape, and then sand in whatever airfoil you desire, usually at a minimum a rounded leading edge (which cuts drag about 50% alone). Take ordinary printer paper and WHITE glue, and apply a VERY VERY THIN layer of white glue to the paper where the fin will go, and press the fin down onto the paper with the leading edge toward the center of the paper. Spread another VERY VERY THIN layer of white glue onto the top surface of the fin and then fold the fin and paper over the leading edge of the fin, keeping everything taut, and press the fin down firmly. Use a round ended round barrelled tool (like a Sharpie marker) to 'burnish" the paper down tight to the fin surface and squeeze ALL the excess glue out from between the paper and balsa underneath. You HAVE to use a VERY thin layer of glue-- use too much glue and the paper will turn to mush and wrinkle or tear. Work from the front leading edge center of the fin toward the back and outside edges of the fin, and "outline" the fin with the end of the Sharpie marker to crease the paper over the fin edges. FLip the fin and repeat. Allow to dry overnight. Cut the fin from the paper with a SHARP (new) hobby knife blade, shaving the paper down to the edge of the balsa on the root, tip, and trailing edge. Draw the fin across a sheet of 220 grit sandpaper a couple times on each of these edges to "shave" any paper 'hairs' off the edge of the paper, and the fins will be ready to glue on the rocket-- no further filling/sealing or sanding required! Plus, you've just about DOUBLED (or more) the strength of the balsa for VERY LITTLE weight gain. Win/win/win in my book!

If you don't want to paper the fins for whatever reason, you can either elect to treat them with CA like the nosecone/transitions, or just move on to filler...

The nosecone and transition, even when CA treated, will still have a lot of grain showing... The CA wicks down deep into the fibers of the cone, transition, or fin, and help seal off the wood grain and glue the fibers together to add a little strength, but the grain will still show. Papering cones isn't particularly feasible so filler is still needed. I use regular Elmer's Carpenter's Wood Filler. Take a dollop and put it in an old baby food jar, or other small sealable container. Add a few drops of water, working it in with a paint brush, to mix the filler and water until it's the consistency of regular hot dog mustard... thin, but not TOO thin. Now you can brush it onto the parts with a 1 inch paintbrush. Once you've brushed on a nice, even coat, (don't worry too much if there are brushstrokes showing, so long as everything is covered pretty uniformly) and set it aside to dry, usually overnight, or at least a few hours. Once dry, the stuff sands off quite easily with 220 grit sandpaper... sand the fin/cone/transition until most of it is gone and you can see through the filler to the wood underneath. If necessary, switch to 400 grit sandpaper for a short second sanding to smooth everything out slick as you please. Sand in SMALL CIRCULAR MOTIONS-- DO NOT sand in straight lines, or you'll get sanding scratches. DO NOT push the paper down hard into the surface; this just creates heat and plugs the paper and wastes time and energy and ruins the sandpaper, and puts deep sanding scraches in the surface. Sand lightly and let the paper do the work. Turn the part continuously in your hand as you sand, DO NOT sand in one spot, or you'll get flat spots and an uneven surface. Wipe the part frequently to remove dust, and inspect the surface by holding it up to the light.

Once you've got the parts sanded down smooth from filling, you're ready for primer. I use the double-glue joint method to join fins to the rocket, so I apply a thin layer of yellow wood glue to the root edge and allow it to dry-- this will allow the glue to penetrate the fin and make a stronger joint. If you're going to CA treat the fins rather than paper them, you should do this step first, so the CA doesn't seal off the fin root wood grain before you apply the yellow wood glue... the CA would prevent it from soaking into the wood grain since it'd already be sealed off by CA, making a weaker fin joint. Double glue joints are stronger than either the tube or the fin, and nearly as fast as using CA to attach the fins, but without the brittleness and low shear strength of CA. Depending on the rocket, I usually glue the fins on first, then primer and paint. If the rocket uses extremely complex paint patterns, sometimes it's better to primer and paint the fins first before gluing them on... just depends; you'll have to decide.

Spray a good coat of a high quality sandable primer on the rocket. Put a light coat on first, then a little heavier with each subsequent coat, about 20-30 minutes apart (read and follow the primer directions). I usually put about 2-3 coats of primer on the rocket. Allow to dry overnight. Sand with 220 grit sandpaper, removing MOST of the primer, but DO NOT sand through it, if you can help it. If you do, a light touch-up and gentle resanding of those areas should do. Sand lightly in small circular motions, and keep the rocket moving. Sand the rocket again with 400 grit, to remove any sanding scratches and make the surface silky smooth. Wipe the rocket off, and hold it up to the light, at an angle, so you get a "glint" of light off the rocket parts... inspect this reflected 'glint' of light for any imperfections... scratches, warps, surface irregularities, pits, voids, or other imperfections in the surface will be readily apparent by this method in the reflection of light off the tube. Either sand these spots smooth with more 400 grit sandpaper, or spray a little more primer, allow to dry, and resand with 220 grit and 400 grit again, until it's smooth. I often will "damp sand" the rocket, nosecone, or parts with 400 grit wet/dry paper... cut the paper up into 2x3 inch squares or thereabouts, dip it in a bowl of water, shake off the excess, then gently sand the rocket as previously instructed. The moisture on the paper mixes with the sanding dust to make "sanding mud" which lubes the sandpaper and surface, prevents the paper from clogging, and makes the surface EXTREMELY smooth as you sand. Periodically dip the paper in water every few minutes and rub your thumb across the grit of the paper underwater, this will remove trapped paint particles and make the paper just like new. SAND LIGHTLY. Use a damp paper towel do wipe away the sanding "mud" and then a dry paper towel to wipe it dry. It DOES NOT take a huge amount of water... just the residual dampness on the paper or an occasional DROP of water will suffice for all this. When you're done, the rocket should be as slick as smooth as can be, and if you hold it up to the light, the glint of light will SHINE off the tube... any imperfections are easily visible, but 99.5% of them should be gone. This whole process takes maybe a couple hours at most...

Let the rocket dry overnight just to ensure no water remains in/on the primer... now you're ready to spray your color coats. Apply the lightest colors first, then the darkest. Light colors are usually pretty poor at covering, and it will take many coats to cover over previously applied dark coats, whereas dark coats usually cover light coats very easily. Apply the paint in several THIN coats, about 20-30 minutes apart, starting with a very light coat and getting a little heavier each time... start spraying before the can is pointed at the rocket, and keep spraying after you passed it. Keep the rocket moving and don't paint in the same spot again or you'll get runs, sags, or drips, which will have to be sanded out later. Don't get the can too close to the surface of the rocket, and don't move the can too slowly... better too fast than too slow... too slow and you'll get runs, drips, and sags. Once you've applied 2-3 coats or so and you're satisfied with the appearance, and the paint has flowed out on the surface smoothly and evenly, allow the paint to dry overnight. It should be smooth and slick with NO further sanding required!

Follow the paint instructions on topcoats. Most paints have DEFINITE 'recoat windows' or "topcoat recommendations" that should be followed to the letter, unless/until you have successful experience otherwise. I don't usually bother with any clearcoats or anything, because 95% of the time they're not necessary. 98% of a great paint job is SURFACE PREP WORK... many people make the mistake of thinking they can rush the prep work and the paint will cover the defects... this is ABSOLUTELY UNTRUE.... paint MAGNIFIES surface defects, it does NOT hide them! Put a good primer coat on the rocket, sand it out beautifully, and then CAREFULLY apply the color coats and the rocket will look terrific with no further work. Botch or rush the primer and sanding work, (or the filling and sanding work for that matter) and NOTHING you do will make the thing look great! The actual painting of the color coats is only about 2% of the work of getting a great paint finish, but it's a CRITICAL step... you cannot get a great finish with botched or rushed prep work, but you can RUIN beautiful prep work with a botched or rushed paint application! They must work together!

IF you REALLY want the paint to look a mile deep, have a deep glossy shine, or feel the need to "protect' the paint with a clearcoat, follow the can instructions to the letter regarding cure times-- DO NOT rush this step, as outgassing of the paint can continue for a considerable amount of time, and rushing now will likely ruin all your work. When the paint is fully cured, you can either wet sand the color coats with extremely fine grit sandpaper, polish the paint with polishing compounds to bring out a deep luster, or apply your clearcoats or topcoats. There is little point to sanding or polishing a paint surface you intend to clearcoat or apply a topcoat finish (like Future or various car polishes) to... in fact, it can be COUNTERPRODUCTIVE, by making the surface too smooth for the clearcoat to stick well to it. If you're going to clearcoat, DO NOT sand the color coats of paint-- apply the clearcoat, allow it to FULLY CURE, then wet sand or polish the clearcoat to a deep luster. If you're just applying Future or car polishes (Nu-Finish, etc) then you can wet-sand the color coats with extremely fine paper, then apply the finish product of your choice per the instructions. Like I said, for 99% of the stuff I've seen and done, it's not even necessary at all... the color coats should turn out SO pretty, IF you've done great prep work and applied the paint well, that no further surface work is required.

Good luck! OL JR

 

[luke strawwalker]

A technique that I've recently found works for me is to laminate the fins in tissue paper and white glue, place them under heavy books to prevent warping, sand with 400 grit, coat with thin CA (the cheap kind from Harbor Freight), and sand again with 400 until smooth. This results in glass smooth fins that are stronger than non-laminated balsa, but still very light.
I know I read about the CA coating technique on here somewhere, I think in one of Luke Strawwalker's novels posts, and combined it with tissue paper lamination for strength-- the tissue paper also helps fill the grain, so you have less sanding to do and it doesn't take as much CA.
This process usually takes a couple of days, just because of the glue's drying time.

Thanks...

Interesting on the use of tissue paper... I tried that WAY back in high school... probably 25 years ago... and it was a DISASTER! I used too much white glue and it shrank as it dried and wrinkled... sanded wrinkles for a week... and white glue does NOT sand worth a darn. What type of tissue are you using?? I used wrapping tissue paper and it didn't work worth a darn-- TOO thin and too easily turned to mush with glue.

That's why I really recommend the regular printer paper... the stuff has worked beautifully... I'll post pics in the next few days of a rocket I'm working on now that I papered the fins with regular printer paper and white glue. No need for glass, stacks of books, or other stuff to prevent warpage... IF you use a VERY THIN layer of glue! I've found that 99% of the papering problems I've had or seen have been due to using TOO MUCH GLUE. I prefer white glue myself, but I've heard people using yellow wood glue with good results.

I'd love to hear more about your tissue papering techniques... maybe *I'll* learn something!

Later and have a good one! OL JR

 

[hornet driver]

Well, your opening up the old box of worms here, but that's a good thing. You'll most likely get a hundred different answers to your question---which ain't a bad thing. I always learn something from these or keep something in the back of my mind for a certain use. My 2 cents--You'll notice if you've seen any of my builds--I tend to kill a forest in my builds. With that said I've streamlined my balsa prep---one way ---just lay on a couple of heavy--wet-- coats of sandable auto primer --let dry between coats and sand between coats with 220 grit--let the final coat set at least 24-48 hrs to shrink and dry---dry sand with 320---apply paint--let dry--sand with 400---respray and your done --add clear if you like---the ticket here is to let the primer cure all the way --it shrinks as it drys and little imperfections will show---the other way--lay a couple of coats of sanding sealer down first then sand with 220 and follow with the previous steps---I use this if I have a piece of wood with really heavy grain---In the end you'll find the style that best suites you !------H

 

[Rocketbuilder]

Thanks...

Interesting on the use of tissue paper... I tried that WAY back in high school... probably 25 years ago... and it was a DISASTER! I used too much white glue and it shrank as it dried and wrinkled... sanded wrinkles for a week... and white glue does NOT sand worth a darn. What type of tissue are you using?? I used wrapping tissue paper and it didn't work worth a darn-- TOO thin and too easily turned to mush with glue.

That's why I really recommend the regular printer paper... the stuff has worked beautifully... I'll post pics in the next few days of a rocket I'm working on now that I papered the fins with regular printer paper and white glue. No need for glass, stacks of books, or other stuff to prevent warpage... IF you use a VERY THIN layer of glue! I've found that 99% of the papering problems I've had or seen have been due to using TOO MUCH GLUE. I prefer white glue myself, but I've heard people using yellow wood glue with good results.

I'd love to hear more about your tissue papering techniques... maybe *I'll* learn something!

Later and have a good one! OL JR

I honestly have no idea whit kind of tissue paper it is. All I know is that my mom keeps it with the wrapping paper, and it is very thin. It definitely is more delicate than printer paper, but I just stuck it on the fins on each side and sat them under the stack of Atlases. I did use even less glue than I do with printer paper or cardstock. The next day it was dried, and sanded smooth pretty well. I actually liked using it better than printer paper, because (strangely) it didn't wrinkle like printer paper sometimes does. After the CA, they were ridiculously smooth.
EDIT: I also put a (very) little tension on the tissue paper when applying it to the fin.
And Hornet, since when do worms come in boxes? :confused2: :neener:

 

[hornet driver]

Little round boxes of worms for fishin--I'm sure in the future they will be little round tupperware containers---- actually --back in the day you went out and got your own worms and put them in a worm box with some soil in it --it usually clipped on your belt or had a shoulder strap---it's a fishin thing!

 

[luke strawwalker]

I honestly have no idea whit kind of tissue paper it is. All I know is that my mom keeps it with the wrapping paper, and it is very thin. It definitely is more delicate than printer paper, but I just stuck it on the fins on each side and sat them under the stack of Atlases. I did use even less glue than I do with printer paper or cardstock. The next day it was dried, and sanded smooth pretty well. I actually liked using it better than printer paper, because (strangely) it didn't wrinkle like printer paper sometimes does. After the CA, they were ridiculously smooth.
EDIT: I also put a (very) little tension on the tissue paper when applying it to the fin.
And Hornet, since when do worms come in boxes? :confused2: :neener:

Okay... that's cool... probably a different kind of tissue paper than I used years back... the stuff I used was closer to Kleenex than wrapping paper... maybe it's treated or something to make it "pretty" and that resists the glue moisture better.

Usually wrinkling or other problems with the printer paper method is because of using too much glue... the moisture in the glue is the culprit... it soaks rapidly into the paper and softens it, and will allow it to "warp" and soften as the paper fibers expand from soaking up the moisture... this of course can really complicate things. That's why I always harp on the VERY VERY THIN glue layer... it's the key to making the whole thing work. Interestingly enough, actually a THIN layer of glue is MUCH stronger than thick layers of glue slobbered all over everything...

I've never CA'd over papered fins... that could be interesting. The CA soaks into the paper and basically turns it into a "composite" material... (fibers of one material cured inside another material applied to it as a liquid prior to curing). I've done paper transitions and boattails and paper rocket nozzles on the Zooch kits with CA, which turns the paper translucent and makes it VERY tough and strong... but I've never bothered doping papered fins with CA... might have to experiment some and see if it adds any toughness or strength... Very interesting indeed!

Thanks for your tips! OL JR

 

[MarkII]

pepe: the right answer is provided by your result. If it looks good, then it is good.

Yes, the lion's share of the rocket build time is spent putting on a good finish. The basic assembly is often the easiest part. I usually start working on the finish of the balsa parts as soon as I start building the rocket, and sometimes even beforehand.

 

[chadrog]

There's no wrong way to eat a Reese's.

 

[Rex R]

I have used tracing paper to paper fins.
rex

 

[luke strawwalker]

Somebody around here (wish I could remember and give them credit where it's due) was recommending some Reynolds Freezer Paper for papering fins... it's sorta like wax paper on one side and regular "sheet paper" or "butcher paper" or whatever on the other... be sure to glue down the "butcher paper" side to the fin, and leave the "wax paper" side facing out away from the balsa...

My questions were: 1) will the thin plastic layer (it isn't actually wax like wax paper's layer is) on the outside hinder moisture moving out of the glue holding the paper to the fin, thus impeding drying or curing of the glue, keeping that moisture in there agains the wood and forcing it to wick out and evaporate through the wood grain of the fin rather than through the surface of the paper, thus potentially increasing risk of warping the balsa fin core, and 2) how does the thin plastic layer on the surface of the paper react to paint application... does it make a good surface for the paint to adhere strongly too, or is the paint weakly bonded to it and liable to chipping or peeling off... or even "beading up" when being applied to it?? How about long-term adhesion?? How about fillet adhesion??

The originator of this idea spoke very highly of it, and reported no problems... I haven't tried it yet, so I reserve judgement myself... personally the printer paper method works terrific for me, and I see no need to fix what ain't broken...

Later! OL JR

 

[emckee]

Anyone ever try Tyvek? The stuff used in the "rip-proof" mailing envelopes?

I'm giving it a shot on a build at the moment. Not sure if my fins will be bullet-proof or just incredibly strong, but I'm a bit worried about how sanding will turn out.

Thanks
-e

 

[luke strawwalker]

Anyone ever try Tyvek? The stuff used in the "rip-proof" mailing envelopes?

I'm giving it a shot on a build at the moment. Not sure if my fins will be bullet-proof or just incredibly strong, but I'm a bit worried about how sanding will turn out.

Thanks
-e

The Dr. Zooch Space Shuttle kit uses Tyvek for the elevator hinges... works very well, but requires a little more effort to get it glued down...

Papering fins with it?? It'd probably work, but take more effort... sanding?? I wouldn't even try... make sure whatever sanding you need done to the surfaces of the fin (airfoiling, etc) is already done and ready to go... because I doubt it will turn out pretty if you try sanding in airfoils afterwards... dress sanding the edges, would probably work okay... (but no guarantees; I'm not speaking from experience here-- you could end up with raggedy fur hanging off the edges of the fins!)

As to strength?? Probably somewhat stronger than regular paper, but again, for what purpose?? Is it worth the time and effort and trouble??

Interesting experiment... be sure to post pics back here showing your techniques and report back on how it goes... I'd love to hear your experiences with it! Good luck!

Later! OL JR

 

[emckee]

Well, the experiment was mostly done already, but here are a couple pics.

I used old race bib numbers for the Tyvek, but mailing envelopes should work just as well.

I didn't find the process of attaching them to the fin material any more difficult than using normal paper. Indeed, the Tyvek won't rip, so it was actually easier to work with in that aspect.

Fins were sanded to shape already, a rough airfoil. I put a thin-ish layer of wood glue down on the tyvek, put the balsa fin down on top of it, then folded the tyvek over (also glued). I burnished the tyvek down to the fin with the round (non-writing) end of a pen. My process then calls for putting the composite sandwich between a pair of phone books, a stiff layer on top, then ~50lbs of weight on it. The weight compresses everything to keep wrinkles out and the phone books have enough give to allow compression of the thinner areas on the fin (e.g. the tapered tail ends) keeping the tyvek pressed close to the wood.

I leave the stack to sit overnight, then trim off excess material (and glue) with a sharp exacto knife the next day.

Everything looked fine up to this point. The fins had the desired shape and were smooth to the touch. I really should have left good enough alone:sad:. However, my skills with the exacto aren't as well-tuned as I might desire, so there were some rough bits along the aft end of the fin. I applied super-thin super-glue in order to make sure everything stayed together. Of course, this roughened up the smooth surface, as it would applying CA to any absorbent surface. I attempted sanding with 400 grit paper, but as expected, this only made things worse. Patches along the aft edge now show the internal fuzziness of the tyvek, not the outer smooth surface. It's not too bad, but not ideal.

I'm hoping that primer will help to seal the surface, whereupon more sanding (did I just say that?) can help smooth things over.

We'll see how the final product turns out. The rocket is something of a workhorse in my fleet and I'm replacing the fins after the old ones were damaged (big, thin, unreinforced balsa fins). It may not be the prettiest thing, but it'll be strong enough to survive just about anything I can put it up on.

 

[MarkII]

Anyone ever try Tyvek? The stuff used in the "rip-proof" mailing envelopes?

Yup - works good. Whenever I need some, I just go down to the post office and grab one or two (don't be wasteful) Priority Mail envelopes -- they're free!

If you do that, don't be a hog -- just grab one or two or however many you will actually use, and not a whole stack. You can always go back and get more if you need them.

 

[Marc_G]

How well does Tyvek take paint? It's spun polyethylene fiber, right?

 

[chadrog]

Yup - works good. Whenever I need some, I just go down to the post office and grab one or two (don't be wasteful) Priority Mail envelopes -- they're free!

If you do that, don't be a hog -- just grab one or two or however many you will actually use, and not a whole stack. You can always go back and get more if you need them.

Are you serious?!? I think they give them out free under the assumption that you'll use them to support the organization, maybe this is why the USPS is in the tank... It can be had rather inexpensively.
https://www.ebay.com/itm/TYVEK-by-t...973?pt=LH_DefaultDomain_0&hash=item4ab94edfd5

 

[luke strawwalker]

Are you serious?!? I think they give them out free under the assumption that you'll use them to support the organization, maybe this is why the USPS is in the tank... It can be had rather inexpensively.
https://www.ebay.com/itm/TYVEK-by-t...973?pt=LH_DefaultDomain_0&hash=item4ab94edfd5

I for one pay enough taxes that I'm not going to apologize for getting a few tyvek envelopes for free... probably the most useful thing the government does with my tax money in all honesty...

Later! OL JR

 

[Alan Roberts]

...
Papering fins with it?? It'd probably work, but take more effort
...
As to strength?? Probably somewhat stronger than regular paper
...

Tyvek covers a lot of ground ... There are "soft" (fabric-like) and "hard" (paper-like) materials, and a variety of thicknesses (think house wrap as well as envelopes). Somewhere in either the USPS FAQs or the Dupont FAQs (more likely), I think I saw 14-lb. and 18-lb. mentioned as the basis weights for normal and heavyweight Tyvek envelopes. Thus it is potentially both stronger and lighter than the typical 20-lb. printer paper.

Yup - works good. Whenever I need some, I just go down to the post office and grab one or two (don't be wasteful) Priority Mail envelopes -- they're free!
...

For whatever its worth, the Priority Mail envelope I am looking at has some fine print along the edge reading:

This packaging is property of the U.S. Postal Service and is provided solely for use in sending Priority Mail shipments. Misuse may be a violation of federal law.​

Are you serious?!? I think they give them out free under the assumption that you'll use them to support the organization, maybe this is why the USPS is in the tank... It can be had rather inexpensively.
...

Or walk into a Staples and buy a Tyvek envelope, which should get you a lighter-weight material than HomeWrap. Somehow I don't think it will break anybody who can also afford to buy a 3-pack of engines.

 

[highsky]

Luke

I've been reading about a lot of different fin finishing techniques, which seems to be about the most difficult part of the construction. I really like your papering technique, and want to start using your method.

If you wouldn't mind clearing a couple of questions, I'd sure appreciate it:

Do I understand that for each fin, you are trying to use just one piece of printer paper, such that for the leading edge only, the paper is "taco-ed" tightly around the leading edge, then pressed down completely over the entire top area of the fin?

I understand how you keep it tight with the round barrel of Sharpie pen. Does this mean that after it dries, you carefully edge cut all of the paper away, EXCEPT for the leading edge?

Do you need any any more prep on the surface then, or just a coat or two of primer, then the color finish? Must you treat the trailing and side edges of the fin before painting, or do you just put some primer on those edges as well?

Also, about your double gluing technique, that I also want to adopt, do you use "yellow" wood glue, then treat both the BT, and the root edge of fin with thin layer of glue, THEN LET THOSE TWO SURFACES ACTUALLY DRY FOR 30 MINUTES WHILE THEY ARE STILL SEPARATED? Then after this 30 of drying, you put on ANOTHER thin layer on the BT and the root edge, THEN press them together for 20 - 30 seconds?

After the Double-Gluing dries, do you then use Titebond Trim and Moulding Glue to make your fillets?

Thanks Luke, I really appreciate your help man.

Dan

 

[luke strawwalker]

Luke

I've been reading about a lot of different fin finishing techniques, which seems to be about the most difficult part of the construction. I really like your papering technique, and want to start using your method.

If you wouldn't mind clearing a couple of questions, I'd sure appreciate it:

Sure, let's do it...

Do I understand that for each fin, you are trying to use just one piece of printer paper, such that for the leading edge only, the paper is "taco-ed" tightly around the leading edge, then pressed down completely over the entire top area of the fin?

Oh, you can cut the paper down to a "rough size" with about a half-inch to an inch at LEAST all the way round the fin... no need to waste a sheet of paper for EVERY single fin, especially smaller ones. To get an idea of how much paper you need for a particular fin, lay it down on the paper with the LEADING EDGE toward the center of the sheet, trace lightly around it with a pencil (outline it) then CAREFULLY roll it over the leading edge onto the other side of the fin, making sure it doesn't slip around on the paper as you flip it over the leading edge... then trace around it again... now cut the paper with about a half inch to an inch of spare paper all the way around it, or just cut it out in a rough blocky rectangular shape so both outlines have plenty of space around them... I can oftentimes get four fins to a sheet, depending on their size and shape... the more swept the fins are, the more "diamond shaped" the outlines are on the paper... so they take more room (on the paper) than more square fins... Of course if the fin has a rounded leading edge or is a weird shape, especially one with an ANGLE on the leading edge (strakes, etc) then you have to get creative and do whatever works best for you on that particular fin shape...

I understand how you keep it tight with the round barrel of Sharpie pen. Does this mean that after it dries, you carefully edge cut all of the paper away, EXCEPT for the leading edge?

YEP, that's exactly right! I posted pics of the whole process in my "DR. Zooch Vanguard Eagle Beta Build" thread (easily found using the "search" box at the top of the page). You use the Sharpie pen to squeeze out any extra glue from under the paper, then let them dry overnight. You can use scissors if you have a big honkin' piece of paper hanging off the sides of the fin, to get it down to a manageable shape (down to about 1/4 inch from the edge of the balsa encased in the paper. From there, use a SHARP (new blade) hobby knife to simply slice the excess paper away down to the surface of the balsa... you ONLY trim the tip edge, trailing edge, and root edges of the fin... the leading edge is 100% ready to go when you finish burnishing down the paper with the Sharpie marker... no further work on it is needed! Just saved 25% of the work, minimum... (maybe closer to 50% on long, thin fins!)

Do you need any any more prep on the surface then, or just a coat or two of primer, then the color finish? Must you treat the trailing and side edges of the fin before painting, or do you just put some primer on those edges as well?

Nope, once the fins are trimmed, I draw them lightly across a sheet of 220 grit sandpaper tilted at a SLIGHT angle off vertical, to "shave" any spare bits of paper (paper "hairs") off the TIP, TRAILING, and ROOT edges of the fin-- DO NOT sand the leading edge... it's already done when you're finished burnishing with the Sharpie... a couple light, quick sanding strokes will true the edges up nicely and remove any excess glue or paper bits from the edges, making them ready for primer.... I USUALLY go straight to the double-glue method, though I DO deviate from that for special reasons-- like the Jupiter-C Explorer 1 I just did for Dr. Zooch to go to the Cape Canaveral Air Force Station Museum... because the fins are glued to a pre-colored wrap, masking and painting the fins after they were attached to the rocket would be VERY difficult... so I put the first layer of the double-glue joint on the root edges, let it dry overnight, and then masked the fin off and painted it, and stuck the fins down onto tape looped sticky-side out to keep paint off the root edges of the fin... worked beautifully! For MOST builds, though, I prefer to glue the fins onto the rocket and THEN prime everything, and sand it all at once... just seems to work better that way for me, but you can do it however you want to... (but I WOULD try to keep the primer and paint off the ROOT edge of the fin so the glue can get the best penetration! ) Either way, once the fins have been papered and trimmed, and edge-sanded lightly, they're ready to go straight into primer or glued to the rocket, filleted, allowed to dry thoroughly, then straight to primer... either way works-- your preference...

Also, about your double gluing technique, that I also want to adopt, do you use "yellow" wood glue, then treat both the BT, and the root edge of fin with thin layer of glue, THEN LET THOSE TWO SURFACES ACTUALLY DRY FOR 30 MINUTES WHILE THEY ARE STILL SEPARATED? Then after this 30 of drying, you put on ANOTHER thin layer on the BT and the root edge, THEN press them together for 20 - 30 seconds?

Yep, that's exactly right... when you're ready to glue the fins on the model, you apply a fairly thin layer of glue to the root edges of the fins and another thin layer to the "fin lines" on the rocket body tube... then set all this stuff aside to dry from about 20-30 minutes to overnight... you basically want them to be anywhere from ALMOST dry to COMPLETELY dry (either works well) before attaching the fins to the rocket tube. Basically it's gonna take about 20 minutes minimum for the glue to get very very tacky (not QUITE dry, sorta "leathery" to the touch-- this is why you use THIN coats... actually the thinner the better, as long as you can see there is actually glue remaining on the surface (especially on the fin, which will draw some of the glue down into the end grain of the wood as it soaks in/dries). I make a handy holder for the fins out of an old egg carton from the refrigerator... invert it, slit the cups with the hobby knife, and presto-- instant fin clamp stand to hold the fin root edges level and upright while they tack up/dry for double-glue joints. There's pics of all this in my "Dr. Zooch SLS Beta Build Thread" for the double-glue method, IIRC... Anyway, once you're ready to attach the fins, put ANOTHER fairly thin layer of glue on the root edge, hold the tube in one hand and the fin in the other, place the 'heel' of the fin root edge (back end of the root edge near the trailing edge of the fin) against the tube on the fin line, line it up carefully, and then "rock" the fin forward until the front tip of the root edge of the fin is tight against the tube. Ensure that the fin is both perfectly aligned with the fin line down the long axis of the tube (the fin is straight) and that the fin is sticking up at exactly 90 degrees from the surface of the tube (that the fin is square to the tube). Hold it steady with slight pressure for about 20-30 seconds, and PRESTO the fin will be "locked" to the tube... the double glue joint works by the fact that the yellow wood glue or white glue (either one works with this method) will soften layers of the same glue previously applied to a surface and allowed to dry, in essence, 'welding' the to surfaces together nearly instantly when a thin layer is applied to dry underlayers and then pressing the parts together... works like a champ. The thinner the layer of glue, the faster the "lockup" time... using VERY thin layers of glue it CAN be nearly instantaneous... but I prefer a LITTLE more glue and working time, so I don't go for EXTREMELY thin layers on the double-glue joints... this type of joint is INCREDIBLY strong, as well... the paper tube will rip the outer layer off or the balsa will shatter and break before the glue itself snaps off between the two parts... you just can't get any stronger than that! (why would you need to?? Remember that thing about the "weakest link"?? )

After the Double-Gluing dries, do you then use Titebond Trim and Moulding Glue to make your fillets?

Usually, yes. SOMETIMES if I want the MOST strength I can POSSIBLY get from the joint, I will fillet with a THIN layer of wood glue on either side of the fin root/tube joint RIGHT AFTER the fin "locks up" to the tube... usually there will be a FEW droplets of glue that is squeezed out from under the root edge of the fin, and now is an EXCELLENT time to spread them out, and a VERY THIN bead of yellow wood glue, applied to either side of the joint, can then be spread with a fingertip down the length of the fin joint, spreading any squeezed out droplets of glue at the same time, and ensuring there are no "air gaps" between the fin root and tube... the key here is THIN, because wood glue is quite runny and shrinks a lot when drying, so if you use a LOT of wood glue slobbered everywhere, you're going to have runs, drips, sags, and huge air holes/voids/bubbles in the fin fillet when you're done. Basically, you should be able to swipe the entire length of the fin joint on one side with your fingertip, and leave a perfectly even, smooth, THIN fillet along the entire length, without having more than a drop of glue spread on your fingertip... so we're not talking about a large amount of glue here... such thin yellow wood glue/white glue fillets should not develop pits or voids or sags or runs or drips... that's the purpose of keeping it THIN!

Let that dry about an hour or two, then follow up with "cosmetic" fillets if desired... the Titebond Moulding and Trim Glue works great for this, best stuff I've found, and it DOES contribute considerable strength to the joint... it's basically a thickened white glue or wood glue, so that it doesn't run or sag or drip when applied in thicker layers, like well-rounded fillets. Be warned though, if you go TOO thick and rounded in a single step, it WILL form pits/voids/bubbles in the fillet-- I found this out the hard way on a build when I pushed the envelope just a little too far! If you want LARGE round fillets, do them in 2-3 steps... it doesn't take any longer, in fact it saves time in not having to apply 3-4 "fixes" to pits/voids/bubbles and having them STILL reappear a few times as the glue dries before you finally get the craters filled in! The great thing about TMTG is that you apply it to all the fin fillets at once, and set the thing aside to dry-- no keeping it perfectly level for hours on end like with wood glue to prevent sags and runs, or for 20-30 minutes like required with epoxy until it sets up firm... it's SO thick that *I* haven't been able to make it run... (not that I've deliberately TRIED to... ) Do all the fins at once, set it aside for an hour, and the fillets should be DONE. If you want them rounder, apply a second coat to all of the fillets, and give them another hour to dry... no muss, no fuss, no sanding... just perfect fillets ready for primer...

Thanks Luke, I really appreciate your help man.

Dan

No prob... just sharing the knowledge... pass it on where you can and help someone else when you have the chance...

If the women don't find you handsome, they should at least find you handy... (Red Green) hehehe..

Later! OL JR

 

[highsky]

OL JR

Thanks a lot man! I'm much obliged to you for sharing your secrets.

You really cleared things up for me. Thanks for taking the time.

Your technique sure saves a lot of time. I don't know why anyone would fill and sand fins again, when they can just paper them.

I also bought the Guillotine Fin Jig from Apogee. This will certainly prevent a lot of headaches and disappointments, and will go great with your Double-glue technique.

https://www.apogeerockets.com/Building_Supplies/Tools/Guillotine_Fin_Jig

The guy from the Apogee site, who makes all the construction videos, really likes using FIXIT Epoxy Clay for filling spirals and making fillets. Have you ever tried that? Looks pretty useful.

Dan

 

[luke strawwalker]

OL JR

Thanks a lot man! I'm much obliged to you for sharing your secrets.

You really cleared things up for me. Thanks for taking the time.

Your technique sure saves a lot of time. I don't know why anyone would fill and sand fins again, when they can just paper them.

I also bought the Guillotine Fin Jig from Apogee. This will certainly prevent a lot of headaches and disappointments, and will go great with your Double-glue technique.

https://www.apogeerockets.com/Building_Supplies/Tools/Guillotine_Fin_Jig

The guy from the Apogee site, who makes all the construction videos, really likes using FIXIT Epoxy Clay for filling spirals and making fillets. Have you ever tried that? Looks pretty useful.

Dan

Sure he likes it...he's selling it! Tim is a salesman's salesman, that's for sure...

Actually, I don't see the need for the epoxy clay for these sorts of applications... it's overkill... it's heavy, and I'm NOT convinced it will "stay put" with much flexing or vibration of the fin in flight... There are other materials (such as the Titebond Moulding and Trim Glue) that work MUCH better for the application and are lighter to boot (maybe not a TON, but DEFINITELY cheaper and easier to work with). For tube spirals, the best stuff I've found is the "Bondo Glazing and Spot Putty" available from your local auto parts store... comes in tubes inside a box... I got a "gigantic toothpaste tube" of the stuff for like $4, that should last til mid-century... the stuff is basically a red putty, in all honesty it's just red oxide primer solids with JUST ENOUGH lacquer thinner to make it a paste instead of dust... You just daub a little on your finger, and rub it into the tube spirals... you CAN use an old credit card or gas card to "squeegee" the excess off if you want, but I usually apply a little narrow "hump" of the stuff over the spiral to ensure that I COMPLETELY fill the thing, and sand off the excess after it dries. The stuff dries quickly (so much so that you better keep a paper towel handy to wipe the excess off your finger from time to time as it spreads out on your skin and dries-- keep it away from your clothes-- it will ruin them!) Give the stuff 30 minutes to an hour under most conditions and sand it down smooth to the tube surface with 220 grit sandpaper and presto-- no more tube spirals! Works like a champ and sands easily...

Good luck! OL JR

PS... that's the reason I like double glue joints as well... no need for expensive fin jigs! I mean, don't get me wrong; there's nothing WRONG with them, and they can occassionally help... And Ted Macklin, the guy who invented the guillotine jig, has a neat design that's probably well worth it for epoxy-glued HPR rockets... BUT, double glue joints basically eliminate the need for them... especially in LPR and MPR...

I usually just use clothespins to attach small "L" shaped pieces of scrap balsa over the end of the rocket and hold the fins on opposite sides of the rocket completely flat and in line with each other for an hour or two until the fins are "dry"... on four finned models, anyway... for three fin models, I can usually "eyeball" them to within "near perfect" accuracy...

 

[highsky]

There are other materials (such as the Titebond Moulding and Trim Glue) that work MUCH better for the application and are lighter to boot (maybe not a TON, but DEFINITELY cheaper and easier to work with). For tube spirals, the best stuff I've found is the "Bondo Glazing and Spot Putty" available from your local auto parts store...

Thanks again OL JR! I'll look for the TMTG and Bondo Glazing and Spot Putty.

Much obliged.

Dan

 

[Creeps]

The guy from the Apogee site, who makes all the construction videos, really likes using FIXIT Epoxy Clay for filling spirals and making fillets. Have you ever tried that? Looks pretty useful.

If you do, don't skip running some filler, such as thinned wood filler, over any dried and shaped fillets before painting. The 'FIXIT Epoxy Clay' seemed to me to absorb a small bit of the paint, causing some dimpling. But after I started using the thinned wood filler that hasn't happened again.

I purchased a three pound batch of the 'FIXIT Epoxy Clay' directly from https://www.avesstudio.com/ because I also wanted some 'Apoxie Sculpt' for the kids craft closet. With shipping it was cheaper through them then any other source for the two. I have used it on all my paper\wood builds since. It goes on smooth. I use a disposable chopstick or short piece of dowel (dipped in water, then tapped on a paper towel to remove excess water) to smooth and shape the fillet. Let it dry over night. File with a round file, sanding dowel works as well. Run a coat of thinned wood filler (about one part water to say ten to twelve parts wood filler for Elmer's) along the fillets. Dry overnight. Sand to smooth to remove excess wood filler. Brush off any loose particulate. Then hit it with the first coat of primer.

And I must say, I love the stuff. I'm sure others probable would just go with thickened liquid epoxy. But for me the epoxy putty gives me time to sculpt as needed. It also sands down and finishes nicely. Though, I didn't like it much for filling tube spirals. I'll have to look into luke strawwalker's idea on that one.

Oh, and please note. I use it for other applications around the house as well. It doesn't take much to fillet a rocket. Around the size of a marble or gumball after mixed for most builds. If you're just going to buy it for fillets, a one pound batch will last you a long, long time.

 

[Professor Fate]

For filling the grain in balsa fins with almost no weight impact, I've have great success with DAP lightweight filler. This stuff is so light, you think the container is empty when you pick it up! Sands ultrasmooth, too...

 

[Rockhiitt]

Does anyone know if balsa fillercoat or sanding sealer will have any adverse effect on the wood glue at the fillet joint?