- Oct 8, 2009
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I got to thinking and was wondering if Bass wood would be better to use for the fins on a rocket. It definitely is stronger but might be heavier.
Absolutely agree with powderburner's post. But you can significantly increase the strength of balsa fins, and still have them be lighter in weight than equivalent ones made from basswood, by gluing paper onto both sides of them. Some people bond regular printer paper to them using white glue; others swear by using sheets of adhesive-backed address label stock. I just used a technique that worked really well to reinforce the balsa fins for my clone of Estes Industries' The Bat. These fins were long, thin and upswept, so they were prime candidates for reinforcement. I used a sheet from a roll of Reynolds Freezer Paper for the reinforcement. This is heavy kraft paper, similar to butcher paper, but what is really neat about it is that it has a smooth coating of plastic on one side. You glue the uncoated side to the fin, and have the plastic coated side as the new surface for the fin.
Now people who reinforce balsa by gluing paper on with white glue warn about the moisture in the glue causing the fins to warp, but that is because they apply the glue to the fin surface, and then stick the paper onto it. What I did instead was to spread the glue onto the paper, and then stick the fin down onto the paper. Applying the glue in a thin, smooth layer makes it similar to self-adhesive address label stock. I took the sheet of freezer paper and taped it, shiny side down, onto a smooth table. Then I applied a thick bead of white glue to the edge of a craft stick, and used it squeegee-style to spread a thin, even coat of glue onto a section of the paper that was just larger than the fin. Then I pressed one side of the fin down onto the glue-bearing surface. After doing this for all three fins, I did place a light book over all of them, just in case the paper decided to wrinkle (it didn't).
When the glue was set an hour later, I cut around each fin with scissors, leaving a bit of margin around each one. Then I repeated the process to adhere the freezer paper to the other side. I placed a book onto top of them (again, I'm not sure if this was really necessary) and left them overnight. Again I cut around them to free them from the paper.
Finally I fitted my craft knife with a new blade and carefully cut off the fringe of paper from each fin. The result was three strong and warp-free but very lightweight fins with sealed smooth surfaces that were ready for priming and painting, once I had attached them to my rocket. I did apply water-thin CA to all of the edges except the root edge in order to seal the edges of the paper as insurance that they wouldn't subsequently lift up.
So far my Bat has two coats of primer on it - 1 coat of Krylon Gray and 1 coat of Dupli-Color Black Sandable Primer. I sanded the Krylon smooth with regular 320 grit before applying the Dupli-Color. Everything is looking good so far. The Krylon had no problem sticking to the freezer wrap fin covers. The plastic coating on the freezer wrap is very, very smooth, very thin, and very durable and well-bonded to the paper. It has a dry plastic feel to it - no waxiness or oiliness. It seems to accept paint well.Hey, I LIKE that Mark!!
Got a pic of the paper box (and rocket)?? I'd like to get some of this stuff and play around with it...
How'd the paint bond to the coating?? Just wonder because some of those plastic coatings on stuff can be kinda waxy and paint doesn't really like that... (polyethylene??)
Later and kudos on a great idea! OL JR
That DOES look good Mark... congrats. Kewl rocket design to boot...So far my Bat has two coats of primer on it - 1 coat of Krylon Gray and 1 coat of Dupli-Color Black Sandable Primer. I sanded the Krylon smooth with regular 320 grit before applying the Dupli-Color. Everything is looking good so far. The Krylon had no problem sticking to the freezer wrap fin covers. The plastic coating on the freezer wrap is very, very smooth, very thin, and very durable and well-bonded to the paper. It has a dry plastic feel to it - no waxiness or oiliness. It seems to accept paint well.
I was in a hurry to get this rocket completely done (meaning painted, decals applied and everything) by last Saturday so that I could launch it at ASTRE's Spooky Sport Launch on Sunday, because flying The Bat unpainted and without its decals just wouldn't have the desired effect. But the launch was postponed until next Saturday because of high winds. So I didn't take any pictures of the covered but unpainted fins. But actually, except for the shiny finish on the covers, they looked just like any other set of fins that had been papered. I didn't do much rounding of the edges except for taking the square edge off, so I just papered the entire surface of each fin, right up to the edge. (When I paper fins that are to have rounded edges, I cut out the paper covers in the exact shape of the fin, but slightly reduced in order to leave a small margin of bare balsa at the edges that are to be sanded round. I make the bare balsa margin on each side of each edge equal in width to the thickness of the fin. I paper right to the edge of the root edge, though.) I am attaching a photo of the primed rocket (on my very cluttered work bench) and a close-up of the fins.
The postponement of the launch actually helped me out because a warm front is moving into our area, meaning that it will be warm enough and dry enough tomorrow to spray on the topcoat outside. I am using Dupli-Color Gloss Black Acrylic Lacquer for the topcoat.
There are pictures of the freezer wrap box at the Reynolds link that I posted before. One thing about this paper is that the plastic coating on it makes it just a bit harder to cut with a hobby knife. Not real hard, just harder than it would be to cut uncoated kraft paper. The next time that I use it, I will trim off all of the excess from the first side before bonding the paper to the other side. Trimming the excess from the edges of both sides at the same time after both sides had been covered turned out not to be really feasible, even with a brand new sharp blade in my X-Acto knife. The thickness of the balsa (3/32") may have contributed to this, though, because the excess margins on both sides were that far apart. I ended up having to trim each side individually. This would have been much easier if I had trimmed the edge of the first side before I glued on the other side. As I mentioned in my previous post, I put a couple of drops of water-thin CA on the edge and then let it roll down the edge and around to the next edge, rotating the fin to keep the CA on the edge and keeping it off the papered sides. I did this in order to seal the edges (except the root edge) and help to prevent the paper from eventually coming loose and lifting right at the edges.
(Start of off topic comments): BTW, Jeff, I used Bondo Spot Putty (which you had recommended awhile back) to fill the spirals on this rocket. Oh, man, does that stuff STINK! Not in how it works but in how it smells! :eyepop: I would almost trade CA fumes for the smell of this putty. Almost. Have lots of ventilation when you apply it, or else do it outside. And it cures extremely fast - I had to mix up two batches to get the small spirals filled on the 12.7" long BT-50 because the first batch hardened on the plate before I could get all of it onto the tube. But you know what? The stuff worked really well! Sanding it down took me just about as long as it usually takes me to sand off Fill 'N Finish, maybe slightly less. It cures and is ready to sand much sooner than FNF. One thing that I have been wondering about lately is whether the water in the diluted FNF weakens the spiral-wound body tube by seeping in and causing tiny delaminations of the layers in the areas where it has been applied. I don't know right now whether this is a real problem or not, but another good thing about the Bondo Spot Putty is that it is waterless. (End of off topic comments)
Thanks for your kind comments about my new papering technique. Another thing about the plastic coating is that it makes the paper harder to tear, a feature which will probably add just that much more strength to the fin when you cover it with this paper. Give it a try; you can share a roll of the freezer paper with your spouse, or at least use it yourself in the kitchen, because you will never use up the entire roll just on papering rocket fins. Another tip - you can put a sheet of freezer paper down on your table or workbench to give it short-term protection from minor spills. I used some on my dining room table to protect it while I was coating my sheet of decals with Future.
Sorry for hijacking this thread - I really don't intend to turn it into a build thread.
I love the smell of Bondo Spot Putty. I'd use it for cologne if I were ever to run out of Hoppe's #9.(Start of off topic comments): BTW, Jeff, I used Bondo Spot Putty (which you had recommended awhile back) to fill the spirals on this rocket. Oh, man, does that stuff STINK!
Thanks a lotGenerally 3/64" to 3/32" with a shape x-acto knife. Letting the knife do the work, sometimes takes 2 or 3 passes. Anything thicker then 1/8" cut on a Scroll or Band saw.
Really for most LPR and MPR models once you use a piece or two You'll never use Balsa again for fins.
I have used a fair amount of basswood. I still use balsa for LPR fins most of the time, though. Never have a problem with it. Usually aircraft plywood or basswood for MPR, but sometimes balsa even there, too. :dark:Really for most LPR and MPR models once you use a piece or two You'll never use Balsa again for fins.
"That gentleman has a certain air about him..." :y:I love the smell of Bondo Spot Putty. I'd use it for cologne if I were ever to run out of Hoppe's #9.
I agree 100%, plus the tight grain makes finishing a snap. It's heavy than balsa, but requires a lot less filling to hide the grain. So, by the time you seal, fill, prime balsa fins the weight difference between balsa, and bass might not be all that significant.Basswood is short for "bad-a** wood" I think it's great, especially it's toughness when used as a fin or wing.
I'm partial to using my small hobby bandsaw with 1/16 to 1/8" blade to cut out basswood fins a bit oversized, then sanding them down to the pattern lines with a small disc sander. Obviously this works best for fins with straight edges, but curved edges could be handled with a Dremel tool with sanding drum attachment.A bit off-topic but how do you cut basswood? Use exacto knife? or do i need something more heavier? I'm still a newbie BAR
X-Acto knife up to 1/8" thick, and utility knife for anything thicker. I can't get precise enough cuts with a saw. Basswood cuts pretty easily.A bit off-topic but how do you cut basswood? Use exacto knife? or do i need something more heavier? I'm still a newbie BAR
hehehe... it ain't about what WE GUYS like, it's about what the CHICKS like...I love the smell of Bondo Spot Putty. I'd use it for cologne if I were ever to run out of Hoppe's #9.
A couple of our teachers put it this way, "Sixth grade boys reek of B.O., Seventh grade boys reek of cologne. After that, they start to get things figured out."hehehe... it ain't about what WE GUYS like, it's about what the CHICKS like...
On a related note, I have to laugh at those AXE body sprays commercials... the ones where the hot chicks mob the guys wearing AXE products... my wife turns her nose up and says, "that stuff smells like (edit) ... half the boys in school wear it and it STINKS!!-- they go for the advertising."
LOL Later! OL JR