Is BSI 30min epoxy ok enough for laminating fiberglass?

[Seatechnerd83]

A rocket came down a little bit hard the other day, and it made me realize that my rocketpoxy fillets were of subpar quality at best. I'm debating doing 1-2 layers of a fiberglass layup for a little bit extra strength. I don't wanna buy any more epoxy right now so I'm wondering if BSI 30min epoxy is good enough for this application. If not then I'll probably just do the correct surface prep and make better fillets.

 

[Titan II]

For your purpose in this situation, you will be fine. If you need to thin it a little, see this from their website...

The one question that is answered most often by the technical experts at BSI is what can epoxy be thinned with. Isopropyl alcohol that is 90-99% pure is what works best. It is available from most drug stores at a reasonable price. Rubbing alcohol contains only 70% isopropyl with the other 30% being water, which can become trapped in the cured epoxy. Denatured alcohol (which is ethanol with an additive to make it undrinkable) has also been used to thin epoxy. Acetone will thin epoxy but will sometimes change the curing characteristics. Also, epoxy thinned with acetone can have an adverse effect on white foam. Epoxies can be colored with the various tinting compounds designed for acrylic and latex paints, which are available at many hardware stores. Colored FINISH-CURE™, thinned with isopropyl alcohol, has actually been applied with a spray gun to form a beautiful final finish on several models. Of course, the immediate clean up of the spray equipment is extremely important.

 

[waltr]

Yes, I have used BSI 30min a number of times to apply glass to fins and BT's. Works fine.

 

[Tractionengines]

Yes it can be used. BUT NOTE: If using "30 min" epoxy, of any brand/type for lamination purposes know that your "on the clock" as soon as you start mixing. Be VERY observant of your time, and realize the bigger batches "go-off" faster.

Having a smoking cup of epoxy next to you, setting up rapidly on your tools, (and everything else), while your panicing, and trying to put down peelply and vacuum bag quickly; is a mistake you'll only make a few times...

[ Using a 12-24hour cure laminating epoxy, and working from large diameter shallow containers will give LOTS of working time. ]

 

[Seatechnerd83]

My rocket is a MD TTW 38mm design, I'm wondering if laminating the fins with a layer of fiberglass, then letting it cure, and using the excess to bond to the INSIDE of the tube and then laying rocketpoxy fillets on top of that and then another layer of fiberglass would be a good way to do it. I haven't seen anyone use this method so it might be interesting to see how it would turn out since it would be pretty much bonded with the entire tube instead of surface bonded. Thoughts? (I am aware that apparently ttw MD isn't the best, but I haven't been able to find out why, and I learned this months after I built this rocket.)

 

[rharshberger]

BSI 20min Finish Cure is made for laminating among other things, its thinner than the 30 minute and penetrates the FG cloth better.

 

[David_Stack]

My rocket is a MD TTW 38mm design, I'm wondering if laminating the fins with a layer of fiberglass, then letting it cure, and using the excess to bond to the INSIDE of the tube...

Curious, if this is a 38mm minimum diameter airframe, won't your proposed fiberglass on the inside of the body tube interfere with insertion of the 38mm motor?

I know that my LOC 38mm motor mount/body tube accommodates a 38mm Loki casing with not much room to spare...

 

[David Schwantz]

Your applying that many layers of glue and glass will add a lot of weight . You'd be better off grinding out the original fillets and starting over.

 

[Seatechnerd83]

Your applying that many layers of glue and glass will add a lot of weight . You'd be better off grinding out the original fillets and starting over.

Thats what I'm planning on doing, sorry if my setup for the situation wasn't very descriptive, but all 4 fins are now off of the tube, and I'm planning on grinding down the fillets and redoing almost everything. I'm not gonna be putting very much glass on there. (probably like 2 layers of 6oz glass).

Curious, if this is a 38mm minimum diameter airframe, won't your proposed fiberglass on the inside of the body tube interfere with insertion of the 38mm motor?

I know that my LOC 38mm motor mount/body tube accommodates a 38mm Loki casing with not much room to spare...

My Wildman fiberglass tube has quite a bit of room in there do do some action. I did my TTW fins poorly last time so I had at least .5mm or more of fin sticking out through the tube. I'm gonna work on it and try to get less fin inside the tube and maybe this internal fiberglass layup will help idk.

 

[David Schwantz]

Have you ever glassed anything before? 2 layers of 6oz glass is a lot of glass and glue. Not only is this a weight penalty but it will also increase the thickness of the fins by double, guessing as you have not stated the thickness. But remember if you are putting 2 layers on, that is 4 layers on the fins, 2 on each side.

 

[David Schwantz]

I do TTW fins on MD rockets all the time. I like to grease up an old motor case, 38mm, and insert it in the tube while I attach the fins. Glue the fins in the slot and do my fillet all in one setting. That way they are all bonded together.

 

[tsmith1315]

Have you considered doing glass strips just on the surface of the fillets?

 

[David Schwantz]

Also, what is your prep for fiberglass? Did you clean them originally? Do you scuff the surface before glue?

 

[Seatechnerd83]

Also, what is your prep for fiberglass? Did you clean them originally? Do you scuff the surface before glue?

I've always cleaned them before, but if i remember right, i didn't scuff the surface. I might have but it A. doesn't look like it, and B. I dont remember doing that. I think I just plain forgot to.

 

[Seatechnerd83]

Have you ever glassed anything before? 2 layers of 6oz glass is a lot of glass and glue. Not only is this a weight penalty but it will also increase the thickness of the fins by double, guessing as you have not stated the thickness. But remember if you are putting 2 layers on, that is 4 layers on the fins, 2 on each side.

No. This would be my first venture into such a thing. Thickness of my fins isn't all that important to me, but the weight is an issue for me, so I think i'll just go with 1 layer, probably not all the way tip to tip. (my fins a 1/8in G10 and the span is about 41mm, and my rocket doesn't fit motors big enough for fin flutter to be an issue.)