Strengthening Parts

Just curious. I've seen several people mention that you could soak your centering rings in epoxy to make them stronger. How exactly is this done? What consistency is the epoxy? Needless to say, I haven't worked with epoxy before.

Mark

I've never done this and would be skeptical of its value. I've heard of people soaking balsa fins in CA to make them stiffer, but plywood centering rings should be strong enough as is. Of course, composite centering rings don't need (and probably won't soak up) epoxy.

That said, to do this one would need to use a very thin epoxy. "Hobby shop" epoxy generally comes very thick, such as would be used for fillets and general bonding. Most epoxy systems (West System, Aeropoxy, Raka, FibreGlast, etc.) come much thinner and are thickened with various substances for different purposes.

John is right, I have never heard of that either. Finishing resin will soak into wood better than building epoxy, but is not very strong. I have coated the outside of centering rings with epoxy before to add a little strength/protection to the wood and make it waterproof for cleanup, but I never have soaked them. Also, I do add a glaze of epoxy to the bottom centering ring, again for waterproofing and to make a sandable surface without the worries of taking off too much wood. You can shape the tail end better that way.

Thin CyA can strengthen a piece of wood because it DOES soak in, but it also makes it more brittle.

Looks like someone was pulling your chain.

Carl

I have a question along the same lines. Not soaking parts but say for plywood fins, brushing on a very light coat of finishing epoxy before fiber-glassing. Would this help in building strength or defeat the purpose of fiber-glassing?

Originally posted by bikeboy
I have a question along the same lines. Not soaking parts but say for plywood fins, brushing on a very light coat of finishing epoxy before fiber-glassing. Would this help in building strength or defeat the purpose of fiber-glassing?

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If you wait until the epoxy cures before fiberglassing over it, you will have a much weaker bond between the fin and the reinforcement. The nice thing about fiberglassing wood fins is that it creates a hard skin for the wood. However, epoxy doesn't bond well to cured epoxy so it's better to just fiberglass the wood directly. The epoxy will soak into the wood and create a very strong bond between the wood and fiberglass cloth. It's even better if you can vacuum bag or press the fins while the epoxy cures.

Thanks John. Oh hey, by the way, if you get a chance, check out my scratch built level 3 project. https://www.mbrocketry.com/my_level_three_project.htm. let me know what you think.

I have never used epoxy (thinking it would soak in) however I have used CA on balsa, or CA and then a thin tissue-type paper over that.

For centering rings, I've added another layer with card-stock or spread epoxy over it after in place.

I have soaked the upper 1" of body tubes with CA which greatly helps in the edges rolling with putting Nose Cone and couplers in and out. I'm not convinced it would prevent a zipper but maybe.

- Nick

Originally posted by bikeboy
Thanks John. Oh hey, by the way, if you get a chance, check out my scratch built level 3 project. https://www.mbrocketry.com/my_level_three_project.htm let me know what you think.

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It looks like a pretty high-performance rocket. Everything seems well thought out and it should be bullet proof. Good luck!

You did a good job with the fin can. The threaded rod is probably overkill, but it is cool. Nice work getting it through all those tiny centering rings!

Those plastic nose cones are a PITA. Threading into plastic doesn't produce a very strong joint and epoxy doesn't stick well to plastic. However, plastic nose cones are very light so you should be OK.

You've done a good job of documenting your project. One thing about the web site that I can't help but mention is the background color. It's very hard to see the links because they're not sufficiently bright against a black background. If you don't stick with a white or light gray background, you have to be very careful with font colors. (You can change link colors with the BODY tag attributes LINK, VLINK and ALINK.)

I have recently reinforced cardboard CRs (like Estes ones) with two layers of 50 g/m² (1.5 oz/yd²) glass each, since they are supposed to be used in interchangeable mid power motor mounts (4x 18 mm, 1x 29 mm and the like). They are not as stiff as plywood, but probably harder to break. Also much lighter.

Oliver

Originally posted by John Coker


It looks like a pretty high-performance rocket. Everything seems well thought out and it should be bullet proof. Good luck!

You did a good job with the fin can. The threaded rod is probably overkill, but it is cool. Nice work getting it through all those tiny centering rings!

Those plastic nose cones are a PITA. Threading into plastic doesn't produce a very strong joint and epoxy doesn't stick well to plastic. However, plastic nose cones are very light so you should be OK.

You've done a good job of documenting your project. One thing about the web site that I can't help but mention is the background color. It's very hard to see the links because they're not sufficiently bright against a black background. If you don't stick with a white or light gray background, you have to be very careful with font colors. (You can change link colors with the BODY tag attributes LINK, VLINK and ALINK.)

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Thanks John.

I honestly used the threaded rod to add some weight to the back to bring the CG back a little bit, and to see if I could do it. I did it more for the challenge.

Do you have any suggestions on the nose cone eye bolt attachment? I have tried many different things like cutting a small slit in the side and feeding in a washer and nut. Trying to thread the nut is always fun.

Also I changed the link colors on the web page. I have had a few other people say the same thing, I just have not gotten around to changing them.

Originally posted by bikeboy

Do you have any suggestions on the nose cone eye bolt attachment? I have tried many different things like cutting a small slit in the side and feeding in a washer and nut. Trying to thread the nut is always fun.

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I used both techniques on my Magnum. Usually, I use slide switches, but this time I used push on/push off switches. (I like the slide switches better.) I like to cut the bottom off the nose cone and build an internal bulkhead. See my Magnum page.

I've poured a puddle of epoxy to completely cover a centering ring from the body tube to the motor mount after it is in place. This is a heavy building practice and using plywood with suffient strength to start with is prefered. If you are looking to add strength to cardboard CA is a better bet, but keep the drying CA away from your eyes as the fumes can be nasty. Happy flying Mark Bosworth