Double Glue Method - extended drying time

Earlier this week, Sunday night, I sat down to glue on the fins to my Fliskits Rose-a-Roc and was using the Double Glue Method. After putting Elmers white glue on the fin root edges, pressing them into the body tube, and then setting them down to mostly dry, I noticed a problem with one of the rotor blades.

Usually when double gluing I give the fins about 5-10 minutes and they still show a little white in the glue, so I know they're not completely dry. Then I add more glue and stick them in place and they pretty much hold tight immediately.

This time, however, the problem with the rotor blade had me stumped (one of the hinge wires broke after I'd glued together the three sections of the hinge assembly and filled all the holes with glue) and I didn't want to put the fins on until I'd figured out what to do.

Last night, three days after starting the double glue, I had time to get back to it and managed to fix the hinge and then resumed with the fin gluing. The glue on the first step had completely dried and I wasn't sure if it would work well or not if I continued. I figured I'd give it a shot and if it didn't work I could always sand off the glue and start over. At the VERY worst I'd have to cut new fins from scrap balsa.

Success! Apparently the glue can completely dry in between steps and it's not a problem. The fins grabbed hold of the body tube immediately and as soon as I wiped off the excess I was able to stand the rocket on the fins and they held the weight. I was very surprised and impressed that this method worked with that long of a delay.

I'm sure I'm late to this knowledge, and most builders on this forum already knew that would happen, but I felt like sharing just in case it helped someone else.

This is news to me, but not in the way you may think! I always double glue my LPR builds, but always waited until the glue was completely dry before doing the second application. It's good to know that this may not be necessary- may not tell my kids because I'm using the double-glue joint not only for durability, but also to teach lessons in patience.

I recently completed a build that was on hold 5 years. First step in double glue was before the hiaitus 27th this kit. Second coat of glue grabbed just fine. I was using Elmers Carpenters wood glue.

Marc_G said:

I recently completed a build that was on hold 5 years. First step in double glue was before the hiaitus 27th this kit. Second coat of glue grabbed just fine. I was using Elmers Carpenters wood glue.

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That's totally awesome! I wouldn't be able to find all the pieces after 5 years to be able to finish it, so it wouldn't matter if the double glue worked or not. Ha.

Mushtang said:

Apparently the glue can completely dry in between steps and it's not a problem. The fins grabbed hold of the body tube immediately and as soon as I wiped off the excess I was able to stand the rocket on the fins and they held the weight. I was very surprised and impressed that this method worked with that long of a delay..

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As a rule, I'll get the 1st step of gluing done and let it sit over night, being one of the last things I do before shutting down the shop. I have tried going all the way letting the first application get close to dry, but met with more failures, as step #2 will soften the first step to a point where the fins aren't sticking so well. It'll still dry and hold like it should, but you risk having the fins tweak while drying as they aren't gripping as expected. Then you have to babysit them until you're confident enough to leave them alone. I was taught to do it this way many years ago and had my doubts at the time. But it's been my trusted application from the start. If you read that thread that resurfaced from 2001, I had explained to Brian about removing the glassine from the tube and showed a pic of it after I had prepped it with glue. That glue had dried for a couple of days already. Just a little dab on the root and PRESTO!

Gary,

I have been meaning to ask you for a little more information about removing the glassine coating from a body tube. Are you running the blade along the body tube (like if you were shaving) to get the glassine coating off or are you scoring the surface? If you score the surface then how does the glassine coating come off or does the glue seep into the cut line and then into the body tube?

I was thinking information on removing the glassine coating where the fins attach to the body should be in the model rocket kit instructions. Think how much better the fin joints will be on the rockets by doing this extra step.

Best regards,
Brian

BRS Hobbies said:

I have been meaning to ask you for a little more information about removing the glassine coating from a body tube. Are you running the blade along the body tube (like if you were shaving) to get the glassine coating off or are you scoring the surface? If you score the surface then how does the glassine coating come off or does the glue seep into the cut line and then into the body tube?

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I've always used sandpaper.

I don't use white glue at all any more. CA is so much faster and then I use 5 minute epoxy for filets. It's just so much faster. I can finish a rocket ready for paint in a mater of hours.

BRS Hobbies said:

Gary,

I have been meaning to ask you for a little more information about removing the glassine coating from a body tube. Are you running the blade along the body tube (like if you were shaving) to get the glassine coating off or are you scoring the surface? If you score the surface then how does the glassine coating come off or does the glue seep into the cut line and then into the body tube?
Best regards,
Brian

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Much like a plotter will cut vinyl down to the release paper, I cut the glassine the same. Sometimes a double pass is necessary if you experience the glassine not coming off very well. After scoring the glassine, (cutting straight down to the tube surface) I'll take the point of my blade and start prying it away from the tube at one end or the other. Occasionally some gets left behind, but you can get that off with a little more prying. The raw tube is much more porous than the glassine, so I like taking it all the way down.

Mushtang said:

I've always used sandpaper.

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Ditto; Roughing up the surface is really the "maximum" that need be done for ensuring premanent Fin/Body bond. In fact is has been proven again and again over the last 30 years that using the double glue joint without doing any extra surface prep has provided outstanding results.
Again! These double white or yellow glue joints have been stronger then the Cardboard and Balsa it is bonding. In several break tests back in the 80's & 90's most of the shear breaks caused delamination of the cardboard tube a minimum of 3 layers down.
I'm not saying you shouldn't sand or cut off glassine layers if you want to. Just passing on that the practice has been proven as unnecessary for several decades. Even us Moldy Oldie builders have for the most part moved on
As for extended time between 1st and 2nd application, I've had parts (fins) laying round for months with only the 1st completely dry application. When getting back to the project just apply the 2nd coat and its done....permanent bond complete.