I have been doing some repair work on my trainer, and I have a couple question concerning epoxy. Is there any differrene other than cure time between a 5 minute and 30 minute epoxy? (Ie Does one former a stronger bond than the other.) My second question is to ask if different brands are better than others, and if so, which.

30 minute is a bit thinner and will soak into soft balsa better. I've had 5 or 6 minute setup just about as hard the next day.
I've used Tower brand and Great Planes and Devcon with the same results. It comes down to which hobby shop I'm in or what mail order special may be offered.

Of course 5 min epoxy will not soak into wood as well as 30 min, hence 30 min epoxy will give better bonding strenght. As for brands, I have used mainly hardware shop stuff like Selleys etc (not the super cheap ones ok). The RC plane epoxy is just too expensive here. None of my planes have had any part come apart, wings have held well even in crashes. Why pay so much more for the same performance?

About a year ago, I was given a box of 6-minute epoxy.

About a month ago, I gave it away - unopened

I just don't see the point in 5 minute epoxy. It sets in 5 minutes, but it takes 24 hrs to cure - same as 30 minute epoxy, but you get far less working time, and it doesn't bond as well.

To me it's a no brainer. So what if I have to wait an extra 10 or 15 minutes? It's not like I build the entire plane with it. For the few things I need it for (Usually only joining the wings and adding the tail feathers) I don't mind letting things sit overnight.

You can add some strength to any epoxy by adding a little bit of mill fiber to it.

Hmmmm... Ya know, MinnFlyer, I think I have a couple bottles of 5 min epoxy that I have never used either. I never thought about it until you mentioned it. The way I build the working time is important. It usually takes me several tries and several "Oh *Sh$*'s" to get things positioned right.

Good point Glen, I forgot about the "Oh S#it" factor.

The problem about the longer setting, thinner epoxy is that you have to find a way to contain it until it sets or it will flow out of the joint long before it cures. Another thing is unless the epoxy is fairly warm the setting time is far longer than the bottle says. For 15 minute epoxy to set in my cool basement it neds at least 25 minutes!!

Fast,

you can speed that up by warming the epoxy before (or after) mixing. Keep your bottles near your furnace, water heater, or other warm spot (WARM, not HOT!) Or stick the bottles in the microwave BUT ONLY FOR ABOUT 10 SECONDS AT A TIME (they heat up very quickly). Or, mix them and warm it up with a heat gun (Again, warm, not hot)

Yes, it will thin it out and make it runny, but only for about a minute or two, then it will reach normal consistancy, but it will set faster.

Thanks for all the replies. I will just go out and pick up a decent 30 minute epoxy to give myself more time to work on the placement. Total cure times for both take about 24 hours before being usable?

A foam plane repaired with 5 minute epoxy can be ready to fly again in an hour.

Regards to all.

One way that has worked for me is when applying somewhat larger sections, like repairing the fuselage, etc. is to put 30 min. on most of the surface and to put 5 min. around the outer edge. That way you get the majority of it to soak in to the wood and you only have to hold the edges for a few minutes.