Better adhesive for estes PSII plastic fins.

Hello all,

I know, I know, yet ANOTHER adhesive thread.. But hear me out! I just purchased an Estes Mammoth kit off of ebay to replace mine which had an issue. That issue being the stupid plastic fins they used on models like the Mammoth, Nike Smoke, and the PSII booster to name a few. The instructions call for CA but I don't feel like its actually the best adhesive that could be used, and as evidence, one of the fins on my old Mammoth split apart during flight. To be fair, I was flying it harder than the recommended BP motors for that kit, but its not like I was trying to hit mach 1 or anything, it was just a smoky composite motor. Anyway, onto the question...

Does anyone have definitive experience with the plastic used in those fins and can tell me which adhesive would be better than CA? I want a weld bond like testors glue forms with styrene parts.

Since this kit is OOP I want to get it right, without any doubt that the fins could split again. Thanks.

Some folks simply put a strip of Scotch tape over the leading edge to prevent splitting.

If you are willing to sand a little, 15-minute epoxy might do a better job. It dries more flexible.

Bat-mite said:

Some folks simply put a strip of Scotch tape over the leading edge to prevent splitting.

If you are willing to sand a little, 15-minute epoxy might do a better job. It dries more flexible.

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I never thought of the scotch tape on the leading edge. Thats a great idea.

I was thinking of trying this product.

https://www.amazon.com/gp/product/B003HNFLMY/?tag=skimlinks_replacement-20

Any thoughts?

What leads you to believe that this would be better than CA?

Bat-mite said:

Some folks simply put a strip of Scotch tape over the leading edge to prevent splitting.

If you are willing to sand a little, 15-minute epoxy might do a better job. It dries more flexible.

Click to expand...

I've got a Nike Smoke floating around here... I think I've got my answer to how I'm going to glue the fins now. I'm liking the idea of combining both methods. Epoxy and tape.

And when I get back to them, the Terrier/Sandhawks are going to get the same treatment.

Bat-mite said:

What leads you to believe that this would be better than CA?

Click to expand...

I do 3D printing and I print with PLA a lot. I've tried CA and I've tried testors glue on the PLA and it really doesnt do well. But supposedly that stuff actually melts the PLA and creates a weld bond. So the fact that it works on plastics that other glues don't, leads me to HOPE that it would work on whatever plastic the estes fins are made out of.

DeepOvertone said:

I do 3D printing and I print with PLA a lot. I've tried CA and I've tried testors glue on the PLA and it really doesnt do well. But supposedly that stuff actually melts the PLA and creates a weld bond. So the fact that it works on plastics that other glues don't, leads me to HOPE that it would work on whatever plastic the estes fins are made out of.

Click to expand...

FWIW, epoxy is terrible with 3D printed PLA parts. BTDT, no love.
Epoxy on Estes/AT fins is also borderline, and chips-off cleanly with a bit of prying.

For plastic Estes/AT fins, I'm yet to find anything that works better than sanding the mating surfaces and applying thick CA. I am not a fan of CA for anything other than temporary tacking parts or gap filling plastic imperfections. Tried multiple plastic/modeling glues - halves come apart with minor motivation.

For gluing together plastic fin halves, I am yet to find anything that works better than CA + taping leading edge with clear scotch tape. If anyone has a better glue lead - please do share.

DeepOvertone said:

But supposedly that stuff actually melts the PLA and creates a weld bond.

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I can see where melting the thin leading edge of a plastic fin would be highly undesirable...

HTH,
a

afadeev said:

I can see where melting the thin leading edge of a plastic fin would be highly undesirable...

HTH,
a

Click to expand...

Only interested in "melting" the thinnest layer of the inside surface of the two halves. Softening is maybe a better word to use. Think of PVC glue how it softens and "melts" the PVC parts which co-mingle and then fuse to become one.

I have built and flown all of the Estes PSII E2X kits (Mammoth, Ascender, Prowler, etc.). I have built and flown the PSII Nike Smoke kit which has plastic fin halves.

On all these models I have assembled the fins using PlastiZap or medium Zap CA+.
None of the fins have come off or separated at the glue joints. I have flown these models on motors up to AeroTech G80s.

One thing I do before gluing the two halves together is sand all the contact areas inside the fins. That removes any mold release compound and produces a rough surface for better glue adhesion.

I used a generous amount of CA on my Trajector fins, then applied Accur8 skins which include cuffs over the leading edge. Those things aren't coming apart any time soon.

I'm not going to say it's "better", because I really don't know, but for my Trajector and my PSII Booster I scuffed mine up with sandpaper and used JB Weld to glue them. I clamped them tight with a bunch of binder clips and let them cure overnight. They seem pretty solid to me.

The best thing for bonding plastic fin halves together is an MEK based glue like Plastruct plastic weld or Same Stuff from Micro Mark. Or a methylene chloride based glue like IPS #3.

+1
This is my first time using this stuff, seems to work great on my Saturn V I'm building now.

I like the plastistuct plastiweld. Used it on my Nike Smoke fun halves and they have taken a few beatings none the worse for wear. Tacked with CA then brushed a bead of Plastiweld In the seams and held with binder clips for a few minutes. IIRC the plastic parts on the Nike Smoke fins are ABS.

Initiator001 said:

One thing I do before gluing the two halves together is sand all the contact areas inside the fins. That removes any mold release compound and produces a rough surface for better glue adhesion.

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While I haven't used the specific glues you're referring to, I did scuff the plastic before I glued them together with water thin CA. I did TRY to make them stick. LOL

Just and FYI, I did purchase the glue I linked above to try it. I'll report back to everyone if it works well.

I use the plaststruct liquid seen in the OP photo, I think it works much better than CA. It slightly melts and welds the pcs together.

I will reassert that CA is just fine if you simply cover the leading edge. Airflow into the leading edge is the reason for the fins to blow apart. Eliminate that and you're golden.

Certainly nothing wrong with Plastic Weld or other glues, of course. But sealing the leading edge is a simple sure-fire solution.

Watching this thread with interest.

On my PSII Nike Smoke (Apache) I filled the interior of the fins with white gorilla glue - slightly expanding. And used clear packing tape over the leading edge.

But my real plastic adhesion problem is my big foamy Estes SpaceShip One. I just can’t keep the two parts of the nosecone together.

Charles_McG said:

But my real plastic adhesion problem is my big foamy Estes SpaceShip One. I just can’t keep the two parts of the nosecone together.

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Have you tried Fabri-Tac?

Why would you use tape to seal the edge when you can permantly seal it with a welding glue? My pro series Nike Smoke fins are permanently sealed on all edges and the fins are solid because of the plastiweld. It’s taken some nice flights on G motors with no fin damage and no signs of splitting.

JJSR said:

+1
This is my first time using this stuff, seems to work great on my Saturn V I'm building now.

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Joe, James,
Thanks for the Plastruct lead - I will add it to my glue inventory.

As I've already finished a few plastic-finned rockets with CA, including the complete (but unpainted) Saturn V.

When ready (mostly talking about the weather), I propose we test which glue holds the fins together the best ... on upto G motors !

a

P.S.: I reserve the right to "cheat" with a G8

diregard. Posted with out reading

I use BSI- Maxi Cure on the plastic fins. Lots of G80 launches on the Mammoth, no issues at all.

Plasti-Zap is my go-to for most things like this. Very good strength, sets quickly and has some gap-filling ability.

neil_w said:

I will reassert that CA is just fine if you simply cover the leading edge. Airflow into the leading edge is the reason for the fins to blow apart. Eliminate that and you're golden.

Certainly nothing wrong with Plastic Weld or other glues, of course. But sealing the leading edge is a simple sure-fire solution.

Click to expand...

I second this. I used CA on all my Estes PSII plastic fins and haven't had a problem. I made sure to get a bead across all of the internal and external structural mating surfaces, but made the bead extra-thick along the leading edge so it would be sure to gush out and fill any gaps. I quickly smoothed it out and made sure it was completely sealed before it dried. I squeezed the halves together for a few minutes as they dried. The leading edges have no gaps for air to enter. I've flown my Smoke on F and small G motors, but have no doubt the fins could stand up to larger G/H motors.

*EDIT* last flight on the Smoke was on an AT G79 (420 ft/s max V, 14 Gs to about 1300 feet).

I wash the factory oil residue off, completely rough up the fins with sandpaper on both sides, JB Weld all contact areas, clamp all ends until dry, drill 1/16 in. holes near all fin edges, widen hole surfaces with phillip head screwdriver, fill rivet holes with BSI 30 min epoxy mixed with micro balloons and sand smooth. Couldn't find the perfect adhesives, so I experimented with trying to improve better methods. Never had a fin split apart yet.

Ok everyone, thanks for all of the replies and ideas. I just wanted to put in my .02 because there were things brought up that I didn't bring up myself.

People commented that they sand their surfaces before applying the glue. Thats something I definitely did on the problem fin. Someone said make sure to use glue on every internal contact surface. Yup, did that. So now I'm left wondering what the non-common denominator is.. To me it is most likely the glue. I'm wondering if some CAs are better for this type of plastic vs others. Perhaps the one I used is just not a good formulation for that plastic. OBVS, there are CAs especially formulated for plastic(which I didn't use). Perhaps that would have been the ticket. Anyway, I did end up ordering the glue I linked in above and I'll report on how well it works. If it doesnt work, at least I know it works on my 3D printed materials.

Ok, boys and girls, final report. I received my order of THIS glue yesterday and I am pleased to report that it does indeed melt and weld the plastic fins used on the PSII kits. That being said, I'm pretty sure that there are others available that do the same, such as THIS(not tested by me). I went back and looked at the fins on my old mammoth and noticed that all three of them were able to be split open easily. This tells me that CA, as per Estes instructions is not always the best glue to use. I wish I had had the acrylic glue the first time.

So, concerning the glue I linked above, I can say that its rather messy to use because the nozzle of the tube is very large so its very difficult to be precise. The good thing is that any squeeze out is quite easy to clean up. Lastly, don't get any on your cutting mat, it'll melt the top layer(ask me how I know,LOL).

I hope this thread will help others in the future to know that Estes may sometimes recommend what's easiest to get instead of whats actually best for the job.

I'm starting an L1 build that will basically be a shortened Ascender, but using the PSII Booster assembly for the fin can. I had bought two of the boosters. When I started looking at the parts closely, I realized that some of the fin halves had kinks on the LE or TE, and they didn't easily mate smoothly to form a straight edge. I sorted parts from both booster kits, and ended up with three fins that were straight and three that were kinda jacked one way or another. So I decided to sacrifice the NG fins to science.

My plan is to use Plastruct Plastic Weld for the perimeters where I can actually get the solvent into the joint. I tried three glues for just the internal mating surfaces of the fin to see which would yield the best result independent of the perimeter. I started by scrubbing all the parts in warm soapy water and Dawn to remove any mold release. I did not sand them. All three fins were clamped around the perimeter while the glue cured. I glued the test parts last weekend and let them cure for a week before destructively separating the halves this weekend.

Testor's red tube. I thought this might have better gap filling than a solvent weld, and indeed it did. But it still sucks. When I pried the halves apart, the glue peeled off the plastic. No more using this junk for anything structural.

Plastruct Plastic Weld. I think this had the strongest joint in terms of PSI adhesion, at least where there was actually a joint, but my concern about being able to get the solvent where it needed to be and have it stay solventy long enough to get the pieces together proved wise. It was much better than the Testor's but a distant second place.

JB Weld Plastic Bonder. https://www.amazon.com/J-B-Weld-50133-Tan-1-Pack/dp/B009EU5ZNO/ I have been using this to glue things to other Estes plastic parts and had good results. It seems to have a solvent component that melts it into the surface of the plastic a bit for a good chemical bond, and it also foams slightly as it cures, giving excellent gap filling. That latter characteristic does make the final result slightly flexible, at least where it squeezes out of a joint and is unrestrained, but it is very tough. This was by far the best result. I had to seriously pry the fins apart, to the point where they were significantly deformed before separating. The glued fin just feels the most solid by far before pulling it apart, as if it is properly one piece.

I weighed all three test parts and the epoxy added only one gram to the fin. The Testors was a few tenths, the Plastic Weld was the same weight as the unglued fin halves.

I have now glued the internal bracing and fin tab portions of the flight parts with the JB Weld Plastic Bonder. Will go back around the perimeters with the Plastruct Plastic Weld some time this week.

I plan to use the JB Weld Plastic Bonder for any other joints in the rocket where I glue anything to the Estes plastic. The one exception is fillets. Its foaming action makes it unsuitable for fillets, or really anything where more than a glue line of a joint will be exposed.

Serendipity: I had almost used up the first syringe of JB Weld Plastic Bonder I bought nearly a year ago. I happened to stop by Hobby Lobby on the way home from work Friday, and they had it on clearance for 75% off. So I cleaned them out and am all stocked up for awhile. I finished the first syringe while dispensing glue for the second flight fin this afternoon and was glad to have more on the rocket shelf.