Mixing 30 Minute Epoxy

[Pauly]

I've got a plane that the tail section has broken off of before. I have in the past used some CA on it and it worked and has held it in place for a long time and did well. Now I have a problem. Saturday I was out at the field and my plane was in my stand and the winds were awful and it flipped it over with the stand and all and of course broke the tail section off again. I was told that I should of used epoxy instead of CA on the it the first time it broke and now here's my chance. My question is I've never used it. How much do I use in mixing the two parts together? Equal or what? I do have some Foam Tac. Sorry I made such a short question into a long story its just I've never used the epoxy and did read on the packaging that the 30 min. is stronger then the 5 min. Thanks in advance.

[xviper]

2 part epoxy is pretty much always 50:50, although some say that you don't quite need that much of the hardener. I just go 50:50 and it's all good.
Personally, I don't have the patience for 30 minute epoxy and use 5 minutes instead. It's plenty strong. Furthermore, for foam repair, I just use FoamTac. It remains somewhat elastic while epoxy cures rock hard. I prefer a little flex. It's so good, if there is a next time, it won't break at the join. It'll break next to it.

[WintrSol]

I've never used Foam Tac, but when using epoxy on a fuselage section, I add something like toothpicks or thin carbon fiber rod as a kind of rebar, just to add a bit more shear strength.

[xviper]

I've never used Foam Tac, but when using epoxy on a fuselage section, I add something like toothpicks or thin carbon fiber rod as a kind of rebar, just to add a bit more shear strength.

Yes, toothpick trick or small CF rods - very common technique. FoamTac is my favorite adhesive. Since I started using it, I rarely use epoxy anymore. I even use FT on foam on plastic, foam on metal, plastic on metal. I'll even use it to hold down stickers and decals that are prone to peeling. When using hinge tape (or blenderm(, I'll spread a thin layer of FT on the foam and put the tape over it. Makes for bulletproof hinges or high stress areas that crack. I still use epoxy for things like motor firewalls and smaller pieces that need solid anchoring.

[fhhuber]

Longer cure time epoxy is GENERALLY stronger because it builds longer molecular chains.
Assorted formulations also affect the strength and flexibility of the epoxy

Mix ratio error can compromise the strength. A really bad error in the ratio can leave the epoxy visibly grainy, indicating it is not going to withstand any significant load.

[StormyDog1962]

Definitely go for the 50:50 Ratio as fhhuber has said otherwise the Epoxy may never harden and rest assured that is one mess you don't want to try and remove.

[WintrSol]

One other trick you can do with some epoxies is, you can thin it to a thick paint with acetone; useful for sealing surfaces and reinforcing things. Of course, anything you put it on has to resist the acetone (most foam will not).

[benjack71]

One other trick you can do with some epoxies is, you can thin it to a thick paint with acetone; useful for sealing surfaces and reinforcing things. Of course, anything you put it on has to resist the acetone (most foam will not).

You use rubbing alcohol. You thin it with rubbing alcohol then you can use it as fuel proofing and you can "paint" your foam plane with it if you want to put a hard clear coat. Just remember most epoxies will yellow after awhile.

[fhhuber]

Caution... mixing random solvents with epoxies can give wildly varying results based on the formulation of the epoxy.

Some epoxies tolerate acetone thinning. Some tolerate alcohol thinning. (be careful here... water % matters) But you reduce the strength. That's usually OK if you are essentially using it for a paint though.

**************

Note: There are 4:1 and other ratio epoxies. You want to use the right ratio... by the label.

[Pauly]

Thank You hero's and fellow pilots for all of your input. I was thinking it was a 50:50 ratio, but wanted to be sure. I do have some Foam Tac and tried it out at the field the other day when it happened, but didn't really have any luck with it. The FT didn't seem to want to stick. Truth be known I was wanting it done then and did try to use an accelerator and was still having issues with it. I will get it up in the stand in the shop and try it and try to clean up some of the old CA in the hole. Thank You friends.

[xviper]

FoamTac isn't an instant fix. It needs at least an hour to set and overnight to cure. FT does not use an "accelerator" like CA. The accelerator does nothing. FoamTac is like contact cement. CA is like Super Glue.

[Pauly]

Thank You Xviper I have found out that FT wouldn't work with the accelerator and it don't dry quick. I do hope that I got my epoxy mixing right or close that is. Its been about a 1 1/2 to 2 hours since I used the epoxy and its a little sticky still but it says that it should take at least 6 to 8 hrs. to completely cure. Is it normal for it to be a little sticky still?

[xviper]

Thank You Xviper I have found out that FT wouldn't work with the accelerator and it don't dry quick. I do hope that I got my epoxy mixing right or close that is. Its been about a 1 1/2 to 2 hours since I used the epoxy and its a little sticky still but it says that it should take at least 6 to 8 hrs. to completely cure. Is it normal for it to be a little sticky still?

Admittedly, I don't measure out each component very accurately, but using 5 minute epoxy, I find that after about 30 minutes, the bond is pretty solid. However, after having said this, I've also noticed that the residual epoxy left in my mixing tray still feels a little "slimy" to the touch, days later. I don't think a little "stickiness" is an indication of a bond that hasn't cured properly.

[Pauly]

Xvip, I did go back later and check it and the stickiness is gone. I did do a coat on the out side of the joint and break and there is some discolor and yellowness as stated earlier, but I'm not to concerned about that as long as the bond is strong. Thank You for all of your help as well as all fellow pilots.

[VOODOO]

I've got a plane that the tail section has broken off of before. I have in the past used some CA on it and it worked and has held it in place for a long time and did well. Now I have a problem. Saturday I was out at the field and my plane was in my stand and the winds were awful and it flipped it over with the stand and all and of course broke the tail section off again. I was told that I should of used epoxy instead of CA on the it the first time it broke and now here's my chance. My question is I've never used it. How much do I use in mixing the two parts together? Equal or what? I do have some Foam Tac. Sorry I made such a short question into a long story its just I've never used the epoxy and did read on the packaging that the 30 min. is stronger then the 5 min. Thanks in advance.

A word of warning about using epoxy resins. The resins have a cumulative effect as to allergic reactions, and over time can cause breathing difficulties. After years of working with epoxies, I developed breathing problems when epoxy fumes were inhaled. I now wear a painters respirator when mixing epoxy. Just something to consider.

[Prowler901]

Thanks for that information, Voodoo. I think we as hobbyists often don't think about the health risks associated with some of the chemicals we use. We don't consider that our limited exposure to these materials can cause issues. But, it is the cumulative affect that can be the real enemy. A mask is a very inexpensive piece of insurance.

Todd

[Pauly]

As an old song would say "Dangerous But Worth The Risk"! But all jokes to the side yes its best to take precautions.