PL premium still provides the majority of the strength, but the wire is there to ensure the fin does not come off should the glue fail while the rocket stretches during pressurisation. The wire also keeps the fin in place while the glue dries.
Once the initial glue dries the wire is trimmed and the twisted part is folded down and a more glue is used to create a fillet on either side of the fin. We are trying a technique to minimise the amount of bubbling from the PL, as PL is not very nice for smooth fillets. After we form the smooth fillet with the PL we place scotch tape over the fillet to minimise the amount of atmospheric moisture entering the glue. Hopefully this will slow down the cure rate and won't produce the big bubbles we normally get. Will have to check tomorrow to see how it went.
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4 comments:
Cool. 'Pyro' HPR type have used this technique on both minimum diameter birds and to reinforce the the bond between fin tabs and the motor mount. The materials there were Kevlar twine and epoxy. This isn't used much anymore with people opting for composite laminates.
Hi Dick,
Interesting info. I do have some Kevlar line on hand and may give that a go on the next rocket, since it is more in keeping with the water rocket mantra of minimal metal components. The one nice thing with the wire was that it was easy to poke through the tiny holes.
Hi George
What size nozzle are you going to use on the FTC rocket? What pressure are you going to launch it at? It looks good.
TDFwaterrockets
Hi Tom,
I'm just doing an update for our main site with all the rocket details. It should be available in the next few days.
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