Alternatives to Rocketpoxy?

[scschulte]

I use JB Weld for any areas that may see higher temperatures - so when attaching fins to a motor mount or areas near the exhaust. I see that JB Weld also makes a Clear Weld product now - will be trying that. I've had good luck with ZAP and DEVCON epoxies.

Two things I really consider:
1. Do I need a 5 minute; 15 minute or 30 minute epoxy
2. Is my surface clean and "roughed-up" to get the best bond

1. For me the 30 minute epoxies give the strongest bonds -- I believe that to be true. 15 minute less strength and 5 minute while still strong, even less strength. (If I am wrong about this I'd like to understand it better - please comment). But in some instances, I need the epoxy to "set" quickly and so then I will use a 5-minute epoxy (especially if not in an area requiring super-high strength - like just putting some epoxy on the wires going into my altimeters on my AvBays to make sure that they stay put!)

2. With all materials and especially fiberglass (which of course is not "glass fiber" to which you are bonding but rather a polyester or maybe phenolic resin which covers the fiberglass fiber or scrim) I first clean the surfaces (water + detergent followed by an isopropyl or denatured ethyl alcohol wash) and then rough them up with a 120 grit sandpaper or similar.

I also measure to the gram: Got 100 small paper espresso "dixie" type cups and set them on my precise balance (to 1/100th of a gram), tare and then x grams of resin followed by x grams hardener -- mix with a wooden stick (glad I like espresso!) -- and apply. A lot of mixing. Generally don't mix more than 10 grams total at a time (or else it gets too hot - especially the 5 minute epoxy!). As we know, epoxy 'glues' work by reacting to cure and therefore don't shrink like glues which cure by giving-off water or a solvent). This system has worked very well for me.

And after 6 weeks of building my Terminator-5, I've gone through about 60 of those dixie cups!!

Thanks for starting this discussion thread.

Steve on Thursday 16 November 2023

 

[Donnager]

For me, the key to rocket poxy is to let it cure for 5-10 minutes before application.

You definitely need to wait if you don't want to come back to stalactites, or runs. Also, it is smoothed pretty easily with a glove and some 70%+ alcohol after it starts to leather up.

Mixing gun type stuff just works easier for me. Easier to put epoxy in a slot, and with the thickened, toughened stuff, it doesn't run when you make fillets (a lot like doing bathtub caulking).

I can install fins in the morning, and do all the fillets after lunch, even on a big rocket. It can be a little upsetting that you can do 90%+ of a 4" rocket assembly in a day, and kind of waste rocket build "enjoyment" time.

I tend to use the hand mixed stuff when I want to drag out a project (and mostly hide in my workshop).

 

[JimByrne]

JB weld & BSI 30 min.

 

[tsmith1315]

On the BSI epoxy, do you guys weigh it or just dump and mix? Anyone know if there is a weight ratio?

Dump and mix. Equal sized puddles, I mix as little as a drop of each, it’s not fussy.

 

[John Kemker]

I've gone with Aeropoxy for everything except high heat areas, such as motor retention, in which case I use JB Weld. That said, the EZI-65 I recently completed was done with all JB Weld.

 

[rdrown]

I recently used Proline 4500 from Wildman. It is higher temp capable, like jb weld, and makes great filets also. Just my $.02 worth.