Another Stupid Glue question

[MrGneissGuy]

I've done the search and haven't found a definite answer, so I'll reluctantly post a glue question (I know there are probably 1000 of them in here...sorry). I'm mixing materials for a scratch build my daughter has "designed". The sketch she did had a boat tail, and when I ordered the NC56 for her rocket, it came in a 4 pack, so I did a little cutting to one of the spare nose cones to make the boat tail.

When building other E2X kits with my daughters where plastic fin cans were being attached to the body tubes, we've used the Testors plastic cement (as the instructions said in the first one we built), and it has worked fine. But with this scratch build, we'll be attaching balsa fins to the plastic boat tail (nose cone), and I'm not sure if that will be strong enough for the stresses that the fins might have. Pulling together bits and pieces from other threads and doing some funky new math interpretation, I'm guessing CA or epoxy would be more appropriate choices. Is that actually the case? It's going to be a BT56 LPR, between 1 and 2 feet tall. The actual fin shape is yet to be determined as we'll be playing with that in OpenRocket before cutting them out and gluing them on.

 

[ClayD]

I've done the search and haven't found a definite answer, so I'll reluctantly post a glue question (I know there are probably 1000 of them in here...sorry). I'm mixing materials for a scratch build my daughter has "designed". The sketch she did had a boat tail, and when I ordered the NC56 for her rocket, it came in a 4 pack, so I did a little cutting to one of the spare nose cones to make the boat tail.

When building other E2X kits with my daughters where plastic fin cans were being attached to the body tubes, we've used the Testors plastic cement (as the instructions said in the first one we built), and it has worked fine. But with this scratch build, we'll be attaching balsa fins to the plastic boat tail (nose cone), and I'm not sure if that will be strong enough for the stresses that the fins might have. Pulling together bits and pieces from other threads and doing some funky new math interpretation, I'm guessing CA or epoxy would be more appropriate choices. Is that actually the case? It's going to be a BT56 LPR, between 1 and 2 feet tall. The actual fin shape is yet to be determined as we'll be playing with that in OpenRocket before cutting them out and gluing them on.

wood glue might work if you scored the plastic well enough, but might separate.. (i have used woodglue before... and has been okay with my mileage)
5min epoxy is about all i use for anything, CA.. is toxic so i dont let my kids get exposed... epoxy is very non-toxic (ohh crap here comes the federalis) the hardener (catalyst- is the nasty part) so the non toxic is formed by your own opinion of MSDS sheets, But the hands wont absorb 5min epoxy at the rate it will CA... Plus CA with go through a latex glove much faster than epoxy... Exposure to epoxy depends on the brand, and some will melt your brain and some give you nervous sesnsitivity if you leave it on your skin.. some are very benign .. HOBBY epoxy at the hobby shop is what i suggest, 10.00 and it lasts for a year, and is great at fixing everything around the house. PLUS, makes great low power rockets that dont fall appart after 100 flights.
giving it time to set up is why people dont like epoxy, but I have found it worth the wait.

 

[jadebox]

I think it'll be difficult to find any type of adhesive that will hold balsa fins to a plastic tailcone reliably. An alternative might be to cut the fins from a plastic sheet. Even then, it'll probably take some experimentation to find the right type of glue.

Another alternative would be to cut slits through the tail cone so that the fins are actually glued to the tube inside the cone.

-- Roger

 

[WillMarchant]

I'd probably use epoxy after washing the tailcone with dish detergent and then scuffing it up a bit with some sandpaper.

https://www.thistothat.com/cgi-bin/glue.cgi?lang=en&this=Wood&that=Plastic might be of interest.

 

[Micromeister]

I've done the search and haven't found a definite answer, so I'll reluctantly post a glue question (I know there are probably 1000 of them in here...sorry). I'm mixing materials for a scratch build my daughter has "designed". The sketch she did had a boat tail, and when I ordered the NC56 for her rocket, it came in a 4 pack, so I did a little cutting to one of the spare nose cones to make the boat tail.

When building other E2X kits with my daughters where plastic fin cans were being attached to the body tubes, we've used the Testors plastic cement (as the instructions said in the first one we built), and it has worked fine. But with this scratch build, we'll be attaching balsa fins to the plastic boat tail (nose cone), and I'm not sure if that will be strong enough for the stresses that the fins might have. Pulling together bits and pieces from other threads and doing some funky new math interpretation, I'm guessing CA or epoxy would be more appropriate choices. Is that actually the case? It's going to be a BT56 LPR, between 1 and 2 feet tall. The actual fin shape is yet to be determined as we'll be playing with that in OpenRocket before cutting them out and gluing them on.

First let me say that most Estes Plastic fin unit models have a cardboard Centering ring that is actually making the contact between the motor mount and main body tube. So your really using wood to wood gluing process. Those that require Plastic FINS attached to Plastic Fincan suggest Testors tube cement to "solvent weld" the plastics togethers. Wood glues (ALL wood or carpenters glues) will not bond to plastics in any way.
Solvent welding Styrene or other plastics to wood only achive a very weak mechanical bond where the softened plastic is forced into the grain of the wood, but this is simply not a good bond for any model rocket.

CA is a good choice as a tacking agent between dissimalar materials. I'd strongly suggest rough sanding the fin contact areas with really rought sandpaper 80 or even 36grit to give the surface more "tooth". the apply the wood fins and fillet with 5 or 30 minute epoxy.

You might also consider using the epoxy rivet method for attaching these fins running a line of 1/16" holes down the centerline and to both sides of the Fin thickness at each fin attachment area. apply a line of 5 minute epoxy alone this line, attach and tape the fin in postion. Fillet with 30minute epoxy covering all remaining evidence of the rivet holes. This is the method I use most often when attaching LEXAN polycarbonate fins to cardboard or other dissimilar material bodies. I've yet to loose a fin with this method
Hope this helps.
PS: the only stupid question is the one NOT ask

 

[Stymye]

giving it time to set up is why people dont like epoxy, but I have found it worth the wait.

I use epoxy when needed , but it gets heavy quick ,,especially the "hobby shop " epoxy that is full of filler to allow the 1 : 1 ratio.

Plus for wood to wood or paper joints, titebond III outperforms any hobby shop epoxy in the strength category.

for wood to plastic I often use Weldbond.

 

[MrGneissGuy]

First let me say that most Estes Plastic fin unit models have a cardboard Centering ring that is actually making the contact between the motor mount and main body tube. So your really using wood to wood gluing process. Those that require Plastic FINS attached to Plastic Fincan suggest Testors tube cement to "solvent weld" the plastics togethers. Wood glues (ALL wood or carpenters glues) will not bond to plastics in any way.
Solvent welding Styrene or other plastics to wood only achive a very weak mechanical bond where the softened plastic is forced into the grain of the wood, but this is simply not a good bond for any model rocket.

CA is a good choice as a tacking agent between dissimalar materials. I'd strongly suggest rough sanding the fin contact areas with really rought sandpaper 80 or even 36grit to give the surface more "tooth". the apply the wood fins and fillet with 5 or 30 minute epoxy.

You might also consider using the epoxy rivet method for attaching these fins running a line of 1/16" holes down the centerline and to both sides of the Fin thickness at each fin attachment area. apply a line of 5 minute epoxy alone this line, attach and tape the fin in postion. Fillet with 30minute epoxy covering all remaining evidence of the rivet holes. This is the method I use most often when attaching LEXAN polycarbonate fins to cardboard or other dissimilar material bodies. I've yet to loose a fin with this method
Hope this helps.
PS: the only stupid question is the one NOT ask

Actually, the two E2X kits I helped my girls with was plastic fin can/motor mount combo, one with a smaller diameter plastic sleeve/plug (male section, if you will) that the BT slid over, and the other that had plastic sleeve (female section) that went over the BT, so they were both plastic to cardboard. The instructions (for one at least, can't remember for sure, they were the first ones we built) said plastic cement, I picked up the Testors for that. It's worked fine for several flights on both. I'm just not as confident with using it for fin attachment.

Some non-rocket building coworkers all seemed to agree Gorilla would likely work pretty well, but none of them said that with extreme confidence. I think I'm leaning towards the epoxy/rivet idea. Maybe I'll just try to talk her into making long sweeping fins that attach to the BT and extend down level with the bottom of the boat tail. :wink:

 

[MarkII]

I would suggest using regular JB Weld. Wash the plastic tail cone with soap and water beforehand, rinse it well and dry it completely. Then lightly scuff up the surface that the fins will bond to. (Just take off the shine.) Most epoxies have very little odor or fumes when they are used in the small quantities that your project will require, but do wear nitrile (blue) gloves, which offer much better protection than latex. I don't know about any long-term effects of JB Weld on the skin, but I do know that it is a real PITA to scrub off of your fingers, so it is best to avoid getting any onto them in the first place. Whether or not there could be any possible health issues associated with it (again, remember that you are only using small quantities), the black splotches of JBW on your fingertips and hands will certainly be a cosmetic problem, and they can take a week or more to wear off on their own.

Gorilla polyurethane glue (the original brown version or the newer white version) is amazing stuff that will form astonishingly tenacious and shock-resistant bonds on just about anything (in this case, you really don't want to get any on your fingers!) but it can be a little tricky to use in model building. The adhesive is activated by water; you have to lightly dampen or moisten the bonding surfaces before you apply the glue. (Never apply water directly to the glue itself!) The problem is that water makes the glue expand and in extreme cases of exposure, to foam up. So to minimize this, you need to apply the water sparingly only to the area that the glue will contact, and also to apply sparing amounts of the glue itself as precisely as you can to just the point of the bond. Using water is mandatory, though, because the glue will not develop enough tack without it and it also will not cure. But if you apply it precisely, Gorilla polyurethane adhesive is simply incredible. (If you need to wipe off any uncured excess, use a DRY cloth or paper towel.)

 

[Micromeister]

The reason there are so many different adhesives and glues is they are DESIGNED for specific bond types.
Gorilla and other brand Polyurethane Adhesives are a Wonderful Woodworking addition. while it is true they can be used on a number of different substrate combinations its expanding nature in most cases does not lend itself to use in Model rocketry. By limiting the moisture to the adhesive it also inpeeds the curing process making the bond much more fragile.
I would Never suggest Gorilla glue for any fin attachment application with the possible exception of a TTW installation. As with many other urethane applications it will become brittle oven time which is NOT a good thing on vibrating parts of our model rockets.

 

[boomtube]

Stupid glue question?

Nonsense; there are no stupid questions just stupid people aski. . .No, that’s not right!

In other news. I’ve had good success gluing balsa to plastic using 5 min epoxy with epoxy also used for the fillets. Sand the region where the fins will be attached with some 220 grit sandpaper.

Be leery when using Testor’s model cement on plastic rocket parts. Testor’s is formulated for styrene plastic and a lot of what’s coming out of China these days isn’t styrene and Testor’s won’t hold.

Or worse it will appear to hold just long enough for you to ignite the motor.

 

[Bone Daddy]

Indeed, there are no stupid questions, only stupid answers.

I'd try sealing the root edge with CA then using CA to glue the fin to the plastic. Scuff up the plastic a bit before gluing. A nice CA fillet seems to help.

Why not do a small test piece using the part of the nosecone you cut off and a small piece of balsa? I do this all the time. Can save some serious heartbreak further on down the road.

But then, this may be one of those answers........................

Bones

 

[MarkII]

Indeed, there are no stupid questions, only stupid answers.

Yeah, you're probably right... I don't always make contact with the ball.

The suggestion to try using Gorilla polyurethane glue was based upon my observation of the incredible tack that this stuff generates as it becomes activated. I have used it on a few occasions in rocket building, but admittedly not for attaching fins. I used it to attach motor mounts in a couple of rockets that I built 6 years ago. It is not showing any signs of becoming brittle in either of them.

I still think that my first suggestion, JB Weld, might be just the ticket for those fin attachments, though.

 

[MrGneissGuy]

After reading all this, I got concerned about the boat tail/BT connection and the mm install into the boat tail I already did and thought maybe I should separate them and add some epoxy or CA or JB Weld. Well, wouldn't you know, I couldn't separate the BT from the boat tail other than by tearing the BT. (when I heard the tearing, I stopped trying). And the mm wasn't budging either.

But those are paper to plastic not balsa to plastic and the cement did soak into the paper some when applying, so I'm sure that helped. I still think I'm going to use the epoxy/rivet method for the fins, though. It just sounds like the best bet. I'll let you all know how it works as far as the build goes. It'll likely be a while before we actually get to test it in flight.

 

[Zack Lau]

Instead of trying to glue balsa to plastic, I'd take a different approach.

I'd attach wood dowels to the fins, and then attach the dowels firmly to the body tube, perhaps through holes in the boat tail. I'd use two dowels for each fin--one along the leading edge, and perhaps another along the high point if the fin were airfoiled.

Zack