Senior Space Cadet
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A couple days ago, I was trying to join two sections of body tube with a coupler. I spread yellow wood glue around the inside of one section of body tube and tried to insert the coupler. The fit was really tight and I was having trouble getting it started. By the time I did, the glue had already started to set. I got the coupler in about half an inch and the glue grabbed. It absolutely would not go in any farther and would not come back out. I've had a couple engine mount failures that I feel are a direct result of the glue drying too quickly and my fear of glue grab.
This is why I decided to try polyurethane glue. There are pros and cons.
Polyurethane glue needs moisture in the air or components to work. Colorado is semi-arid, but yesterday was more humid than normal and I had no problem with the polyurethane glue curing.
If I had used polyurethane glue to glue in the coupler, I could have inserted it, taken it back out and inserted it again. It is slippery and has a long working time. I used it to make a motor mount last night and it went together easily and is now completely cured. God couldn't get it apart.
Polyurethane glue foams as it cures. Seems like this would make it bad for fillets. It also means you might have to do minor sanding before a motor mount, glued with polyurethane, would slip into a body tube.
It probably works best in humid climates but you probably have less problems with yellow glue in humid climates, so there's that. I wouldn't use it for fins or lugs. I would use it for motor mounts, couplers, and baffles.
It can be messy to work with. Parts can slide around so you need to be aware of how you position things for curing. Interestingly, it has a long work time, but it's total cure time is fairly fast. Once cured, it is more waterproof than wood glue but less so than epoxy. It is stronger than wood glue, but less than epoxy. It will glue things other than paper and wood.
A bottle has a short shelf life. Buy small bottles.
This is why I decided to try polyurethane glue. There are pros and cons.
Polyurethane glue needs moisture in the air or components to work. Colorado is semi-arid, but yesterday was more humid than normal and I had no problem with the polyurethane glue curing.
If I had used polyurethane glue to glue in the coupler, I could have inserted it, taken it back out and inserted it again. It is slippery and has a long working time. I used it to make a motor mount last night and it went together easily and is now completely cured. God couldn't get it apart.
Polyurethane glue foams as it cures. Seems like this would make it bad for fillets. It also means you might have to do minor sanding before a motor mount, glued with polyurethane, would slip into a body tube.
It probably works best in humid climates but you probably have less problems with yellow glue in humid climates, so there's that. I wouldn't use it for fins or lugs. I would use it for motor mounts, couplers, and baffles.
It can be messy to work with. Parts can slide around so you need to be aware of how you position things for curing. Interestingly, it has a long work time, but it's total cure time is fairly fast. Once cured, it is more waterproof than wood glue but less so than epoxy. It is stronger than wood glue, but less than epoxy. It will glue things other than paper and wood.
A bottle has a short shelf life. Buy small bottles.