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.
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Mixing 30 Minute Epoxy
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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.
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Originally posted by WintrSol View PostI'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.
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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.FF gliders and rubber power since 1966, CL 1970-1990, RC since 1975.
current planes from 1/2 oz to 22 lbs
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Originally posted by WintrSol View PostOne 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.
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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.
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Note: There are 4:1 and other ratio epoxies. You want to use the right ratio... by the label.FF gliders and rubber power since 1966, CL 1970-1990, RC since 1975.
current planes from 1/2 oz to 22 lbs
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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.Still Learning:D
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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?
Still Learning:D
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Originally posted by Pauly View PostThank 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?
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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.Still Learning:D
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Originally posted by Pauly View PostI'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.
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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
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