David, 'fraid I don't have any answers, but I do have a question, as the Aspire is high on my list of rockets to build next. What do you mean that epoxy "pushed the fin over"?

thanks and welcome to the club!

Greg R.

Oh, the distinction on research days is that they use home grown motors. Custom rockets can be flown on "club" days as heads up launches (at least the first time), meaning, look up in case it comes down fast or in pieces!

Just a reminder, the rocketry calendar is incorrect for this weekend. We're only flying on Saturday this time.

Thats some great use of the english language. I wrote that in the morning before work, sorry. yeah, so i glued two separate fins, "not funs, hehe" onto a scrape piece of wood. one fin i used elmers wood glue with a fillet. The second fin i used some epoxy clay, Loctite was the brand. Then using my hand to push against the fins. Epoxy fin pushed right over, mild force. Elmers wood nerver gave up, fin busted right above the glue.

So my question then would be, has anyone ever coated the whole rocket, or just fins, in elmers glue?

does it add stength?

unnessacary weight? F and G engines

you can sand it, so would make a great painting surface? or just stick with sandable primer?

thanks for the welcome, Im sure i will learn tons from everyone.

David

So my question then would be, has anyone ever coated the whole rocket, or just fins, in elmers glue?

Most of us would use a light fiberglass layer instead of coating it with anything else. Glue or epoxy won't add THAT much strength. Did the epoxy cure properly? I've never had that happen before. It should have snapped either off the airframe or at the glue/epoxy joint.

P.S. I will admit that for a SSS contest flight a few years ago, I tried putting epoxy over plywood fins and gave it a good epoxy fillet (no glass)... I happened to hit the rocket fins into a wall as I was taking it upstairs the night before, everything looked okay... when I got to the launch and prepped the rocket, a fin snapped off... then another. It was really embarassing. That rocket had the best paint job I ever put on a rocket of any size, slick as can be and waxed. Glass it.

interesting, when i first started on low power (ie estes) rockets i had a lot of trouble loosing fins w/white glue. that was completely solved when i switched to jb weld epoxy. the only time i've lost a fin w/epoxy is on ballistic landings - ie, no chute!

that said, more recently i've been trying wood glue with great success. advantages: much cheaper than epoxy; easy clean-up, shrinks when it dries so it's less visible.

epoxy will remain my first choice for absolute strenght, tho.

Glue over an airframe or fins does nothing but add weight and perhaps a small modicum of water resistance. It does NOTHING for strength. To add strength, you need to add something for the glue to bond to that will increase the strength of the item being reinforced. Typically this is fiberglass, Kevlar and Carbon fiber fabrics, however paper even works. I've seen people use old pantyhose even.

There is a whole science to this topic too deep to go into in a brief post. The question needs to be asked what kind of strength are you trying to add? Once that is clear, then the best way to go about getting becomes a lot easier to answer.

While Apogee recommends epoxy clay, I've never used it and suggest the "Bob Smith" epoxy for paper and wood rockets. I do frequently use the Apogee recommended paper laminating of fins, and it is a significant strengthener. The trick is to use a very thin layer of wood glue. You want to squeegee all the wood glue off the fin until you have it as thin as you can before putting the paper on. Standard 20# bond works fin. Do both sides of the fin in quick succession and press between heavy books.

The Aspire is aerodynamically challenged in the fin area, not strength challenged in the tube. Don't worry about tube compression or bend unless you have a lot of nose weight. If you want to add strength in the tube, suggest an extra internal coupler or two ahead of the fins and motor mount.

I'd recommend epoxy fillets. I do mine with the standard hobby store 20 min epoxy and they turn out great. Adding some fiberglass pulp will help, but is probably not essential.

If you are really interested in breaking mach, then you will need to keep the rocket under 120 grams empty weight for a mach flight on a G80 Roadrunner motor. If you want a bit more strength, you could always cut some thin plywood fins and put those on instead of the Apogee balsa ones. There are some more suggestions on the internet related to mach busting.

See you out at the launch, and ask the range control officer to ask for "an extra set of eyes" to track your speed monger. Good luck.

chad, thanks for all the tips. i've been thinking about trying the paper on fin trick, you've convinced me to give it a go - among other things it sounds like it's w/in my skill level!

what's bob smith epoxy?

Here is a link to the Bob Smith epoxies. They are cheap and easy to find, and work very well on paper and wood, but they aren't great for fiberglass and composites.

http://www.bsi-inc.com/Pages/hobby/epoxies.html

The 20 min version is ideal for fillets and is low viscosity. The 5 minute is very fast, and I wouldn't recommend it unless you like to build fast, are impatient, or really need a fast connection. You can get them at your local HobbyTown. You can probably find fiberglass pulp there too.

PS. Practice paper lamination on a piece of junk balsa before you try for real, just so you get a sense of how little wood glue you need. If it wrinkles, you need less glue. You will sand through the paper laminate for the leading and trailing edges, but that will be OK.

Lots of great imput. Thank you all for your knowledge and feedback. Yeah, was hopeing to have her ready for 8/1, but she hasnt even made it to paint yet, next time. I have been using wood glue, figured white was to weak.
would love to see Mach +, wow how cool is that

Thanks again

david