Loc Aura fin glassing

[Nick Hutton]

I’m building a Loc Aura and need some advice. After much searching of the forum, I rightly or wrongly decided to stick with surface mount fins. I’m building it pretty much stock except for the addition of a PSII retainer





I’ve attempted to make glue rivets by drilling 1/4 in spaced holes in airframe both under the fin root and in the area next to it for the fillets. I also drilled into the fin.



View attachment 391546

I’ve attached the fins with TBIII and also used it for first fillet. I’ve then done a TB thick fillet over the top.



They prob still need a day of curing, but I’m not convinced the are rigid enough. Some more forum searching has led me to contemplate laying some fibreglass cloth along the fillet line (say 1/2 inch on body and 1/2 inch on fin. I have some cloth and some BSI finishing epoxy, but......... I’ve never glassed a rocket - just repaired surfboards.



I’ve trawled the forum and also YouTube, but so far can’t see any tutorials or step by steps on how to do this. Can anyone point me in the right direction?

 

[mbeels]

I'm not an expert either. John Coker has some fiberglassing body tube videos that are well done. What weight fiberglass is that? For a small strip, I'd basically cut a piece to size, lay it on the fillet, and then pour a small amount of that finish cure on. Not too much, it will add weight on the wrong end of the rocket. The finish cure is nice and thin, it should be pretty runny. Try and squeegee or sponge as much excess off as possible. I've used foam brushes for that. Getting the edges to lay flat and look neat may take some trimming / filling / sanding after.

Or do it like a surfboard repair, you may get better results with your experience!

 

[Nick Hutton]

The rocket has a really heavy nose cone and is way over stable so extra weight won’t be an issue particularly as I’ve done all gluing so far with wood glue. Cheers. Hadn’t thought of checking Coker’s site. I’ve followed his tutorials for other things already with success

 

[5x7]

I agree, use a 1 inch strip on the joint, the glass is transparent when wetted out, make sure to eliminate dry spots then do any trimming when it’s green. Use a filler if you want to fill the weave and sand if you care what it looks like. I have an Aura and I used the streamer and it lost a fin, then switched to a chute and it still would lose one once in a while, I think every fin broke off one time or another. Eventually I removed the old fillets and glassed the fins similar to what you are proposing but just did a layer fin tip to tip, then refinished the whole thing, see the pics showing the starting point of the project to the end.

 

[Nick Hutton]

I’ve glassed all three fin joints over the last day.

My first attempt still has a fair bit of air and the glass pattern is quite obvious



My last attempt is quite a bit better



I don’t have any peel ply, so after reading through the forums I used some scraps of ripstop nylon



Question. Can I work some more finishing epoxy into particularly the fillet line to smooth it out, or will that not help. I realise I’m going to be sanding a fair bit to get this looking good.

I’m now investigating sourcing some tighter weave fibreglass cloth and peel ply locally.

 

[mbeels]

That looks like it came out quite well. Did you get the stiffness you were looking for?

 

[heada]

Looking good and even your first one should be plenty strong. I've found that you can't "fix" air bubbles under the cloth. What I've done is to sand it and it sands through the air bubble. I then add a coat of epoxy that is thickened with microspheres to make sanding easier. Paint the thickened epoxy wider than the initial epoxy and then sand it down and feather the edges.

 

[Theory]

Looking good and even your first one should be plenty strong. I've found that you can't "fix" air bubbles under the cloth. What I've done is to sand it and it sands through the air bubble. I then add a coat of epoxy that is thickened with microspheres to make sanding easier. Paint the thickened epoxy wider than the initial epoxy and then sand it down and feather the edges.

^^^ THIS ^^^

 

[Nytrunner]

the glass pattern is quite obvious

Welcome to the wonderful world of Bondo Spot and Glazing putty (the 1-part stuff, not the 2-part)

 

[Wallace]

Welcome to the wonderful world of Bondo Spot and Glazing putty (the 1-part stuff, not the 2-part)

Exactly. Skim coat and sand smooth. Thousandfold easier than additional epoxy coats, sands stupid easy, leaves a nice smooth finish.