rocketpoxy for internal fillets

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littlemisterbig

littlemisterbig

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Hey guys,
I just received my madcow arcas hv, cesaroni 2 grain 38mm casing, aeropack 38mm retainer and 8oz pack of rocketpoxy. However, it did not occur to me that rocketpoxy might be difficult to use on internal locations such as where the mmt centering rings attach to the airframe and at the roots of the fins. I was thinking of using 5 minute epoxy in places like those and rocketpoxy everywhere else. What would you guys recommend?

thanks, Littlemisterbig
 
That would be a good option if it is available to you. Rocketpoxy might not flow as well and It would be hard to get in the smallish airframe
 
In my builds, I'm using 30 minute Epoxy from Bob Smith Industries (probably available at your LHS).

Trust me, you'll want the extra time for wiggle room.
 
Rocketpoxy has two stages (John told me three, but I forget). The flowing consistancy and the peanut butter consistancy. What you could do is bond the motor mount, but dont bond the aft centering ring. Then bond your fins with rocketpoxy. Once that cures mix some rocketpoxy and apply a large amount to the area where your going to apply fillets. Turn the rocket upside down and let gravity do its magic.


Alexander Solis

TRA - Level 1
Mariah 54 - CTI RedLightning- I-100 - 6,345 Feet
 
15 or 30 min Bob Smiths stuff. I rarely use 5min. The longer the cure the stronger with Bob Smith stuff. The 30m is "runnier", for example, and will grab what's being bonded better... 5m can start to set too soon if you need to position things like TTW fins or even a MMT, But 30min flows much better for things like internal fillets. 15min is my "go to".
 
Rocketpoxy will flow if you mix and use between 1 to 20 minutes. I do all my internal fillets and centering rings with Rocketpoxy and never have a problem getting to flow when it needs to be. Mix and use between 1 and about 20 minutes, then you can put a blob on the end of the inside air frame tube and tilt the air frame and let gravity flow the Rocketpoxy to where it needs to be. The issue with 5, 10 and even 30 minute unfilled epoxy's such as Bob Smith is that it shatters like glass when it gets hit hard ( put some in a small plastic cup and give it a little whack with a hammer and you will instantly see what I mean). Also eventually all the flexing a rocket does will start cracking the epoxy. Now think about all the flexing fiberglass does in take off, in flight and especially on landing when the fins hit the ground. Rocketpoxy is a highly filled, high strength structural epoxy that will not shatter.
 
jolevich said:
The issue with 5, 10 and even 30 minute unfilled epoxy's such as Bob Smith is that it shatters like glass when it gets hit hard ( put some in a small plastic cup and give it a little whack with a hammer and you will instantly see what I mean). Also eventually all the flexing a rocket does will start cracking the epoxy. Now think about all the flexing fiberglass does in take off, in flight and especially on landing when the fins hit the ground. Rocketpoxy is a highly filled, high strength structural epoxy that will not shatter.
Click to expand...

I've had same issue with BS. RP is awesome. Internal 10 min external 40 min for me
 
Nick@JET said:
I've had same issue with BS. RP is awesome. Internal 10 min external 40 min for me
Click to expand...

I usually wait about 20-25 minutes for the externals. It might sag a little bit, but not much. I tried 30 mins once and it got to a clay consistency that was hard for me to work. Might just be the difference in weather between Indiana and So Cal. Or your better/more patient at working thicker epoxy then I am.

At any rate, I think if you mix consistently you can get the timing down for the thickness you want to work with. Good stuff.
 
I would avoid the 5 minute epoxy. You won't have enough time to get it to flow properly down the joint, and it will be more brittle once it cures. A hard landing may crack the joint, which you won't see since it is internal.

If you want to use rocketpoxy for the internal fillets, I've had good luck with putting the rocket up on its end, smearing the rocketpoxy on, then hitting it with a heat gun to help it flow down. Also, the structural Aeropoxy seems to flow a little better than rocketpoxy for things like this, if you can get a hold of some of it that would also work well. Both of those are almost certainly overkill for an L1 rocket, but would be good experience learning to work with it.
 
I've found BS 30min to be much less prone to cracking than 15min. I've been using it on my builds with success, though I have a couple M-capable projects that I'll probably be stepping up to Proline for.
 
I'll largely copy my post from the other thread, with some small amendments:

If you plan on doing a fair number of high power builds in the future, do yourself a favor and get a better epoxy system. There are cheaper and much better quality systems out there.

  • Many rocketeers use Rocketpoxy and swear by it. It's a epoxy that's premixed with a filler blend. You mix it together and it's the consistency of peanut butter, so it doesn't sag.
  • I use US Composites 635 system with the 4:1 hardener. It's cheaper per oz than the 5/15/30 hardware store epoxies and higher quality too.
    • The Quart kit will last you between 15-25 Level 1 and 2 builds.
    • Being that it's a laminating resin, for structural applications like fillets you will want to add filler.
    • For internal fin fillets, I normally add 25% the epoxy weight in Milled Fiberglass.
    • For external fillets, centering rings, etc, I normally add 25% the epoxy weight in glass microballoons and 5% the epoxy weight in fumed silica, which gives me an epoxy paste that roughly the same in consistency and properties as rocketpoxy. You can get the filler from US composites or Amazon.
    • Get the pumps but weigh your epoxy (see below). The pumps allow you to easily dispense the epoxy but using them as directed (4 pumps resin/1 pump hardener) yields about 200 grams of epoxy. For 3in/4in rockets you will want 15-20g of epoxy max per application.

  • West Systems is a suitable substitute for the US Composites system but it will cost you more.



Whether you use the hardware store systems or one of the better epoxies, there are some prep and processing things you need to follow:

  1. Get yourself a scale. You can get a decent gram scale on amazon that goes to .1g for $15. Weigh your epoxy components every time and make sure you are adhering to the ratios. If you don't measure right, you will have either uncured resin (which severely weakens the joint) or leftover hardener (which can make the joint brittle). If you do this one thing, your results with the BSI epoxies will come out much better.
  2. Surfaces need to be wiped clean of oils, then scuffed with sandpaper. The thread Properly bonding composites and what your government doesn't want you to know. contains all you need to know.
  3. Gloves as a must. Epoxy on the skin is not going to kill you, but over time you will develop severe allergic reactions to it if you keep on touching it. Disposable nitrile gloves work best.
  4. The fillers mentioned above work well with the BSI epoxies mentioned here have and you can get them on Amazon pretty cheap though US composites is cheaper. I would recommend you pick up both the fumed silica and the glass microballoons (unless you go with Rocketpoxy).
  5. Get yourself some 8oz plastic/paper cups and some wooden popsicle sticks for mixing. Amazon had the best prices for me.
 
I use US Composites 150 with 3:1 hardener on nearly everything. I now have three different types of fillers (fumed silica, faring compound, and Q-Cells) to use for different purposes plus chopped fiberglass just in case. I do have their 635 stuff as Nate mentioned above but have yet to get the hang of that one. I've used it twice and it took forever to cure.

I've also used RocketPoxy. And right now I have nothing positive to say about it. You have to dig it out of the cup with an E-Tool. It mixes easy enough but if left on your mixer stick, or dipping stick if you have one that will scrape it out of the cup, it will run and get everywhere. Everywhere I tell ya. I had it on my elbows! I may exaggerate a little but it is the messiest stuff I have every used. I used some to embed a nut to a ring in my nose cone and when I tightened the threaded rod down, the nut simply came loose. The RP didn't hold at all. I'm not giving up on it yet though, I know most things have a learning curve.

You can always extend you fin slots out the aft end of your rocket and assemble your fin can outside the rocket so you can get all the fillets you need. Then slide it back in as one assembly. I have been doing this for quite a while now. And you can get great fillets, even with chopped fiber.
 
MikeyDSlagle said:
I use US Composites 150 with 3:1 hardener on nearly everything. I now have three different types of fillers (fumed silica, faring compound, and Q-Cells) to use for different purposes plus chopped fiberglass just in case. I do have their 635 stuff as Nate mentioned above but have yet to get the hang of that one. I've used it twice and it took forever to cure.

I've also used RocketPoxy. And right now I have nothing positive to say about it. You have to dig it out of the cup with an E-Tool. It mixes easy enough but if left on your mixer stick, or dipping stick if you have one that will scrape it out of the cup, it will run and get everywhere. Everywhere I tell ya. I had it on my elbows! I may exaggerate a little but it is the messiest stuff I have every used. I used some to embed a nut to a ring in my nose cone and when I tightened the threaded rod down, the nut simply came loose. The RP didn't hold at all. I'm not giving up on it yet though, I know most things have a learning curve.

You can always extend you fin slots out the aft end of your rocket and assemble your fin can outside the rocket so you can get all the fillets you need. Then slide it back in as one assembly. I have been doing this for quite a while now. And you can get great fillets, even with chopped fiber.
Click to expand...

Mike, I normally give the 635 about 12 hours before I work on it. Is that different from your experience? Also, do you weigh out the resin and the hardener? You may want to try adding both the Q-Cells and the fumed silica. The silica is a Thixotropic agent which means it will help the epoxy from sagging when it's still but still loosen up when your moving it around. The QCells are a good filler, little lighter than microballoons but same concept. Together, it's a perfect combination for external fillets.

My biggest problem with RocketPoxy was weighing it too. The pumps make the US composites systems so easy to dispense. With the RocketPoxy I had to use 2 sticks, taring for each stick, and gooping it out was far less controllable. Considering the expense of the product compared to the 635 and the extra hassle it just wasn't worth it...
 
NateLowrie said:
Mike, I normally give the 635 about 12 hours before I work on it. Is that different from your experience? Also, do you weigh out the resin and the hardener? You may want to try adding both the Q-Cells and the fumed silica. The silica is a Thixotropic agent which means it will help the epoxy from sagging when it's still but still loosen up when your moving it around. The QCells are a good filler, little lighter than microballoons but same concept. Together, it's a perfect combination for external fillets.

My biggest problem with RocketPoxy was weighing it too. The pumps make the US composites systems so easy to dispense. With the RocketPoxy I had to use 2 sticks, taring for each stick, and gooping it out was far less controllable. Considering the expense of the product compared to the 635 and the extra hassle it just wasn't worth it...
Click to expand...

First time I used 635 was to swab it inside a body tube to stiffen and strengthen the BT. It took a while to cure but not sure how long, I set it aside and worked on other parts; but it was tacky for a couple days. I used it on internet fillets with chopped fiberglass and let cure overnight. Next day it was still gooey but not runny. I used aluminum foil and a shop light for heat to finish it off. I was told that sometimes the stuff will be tacky and needs to be rubbed with alcohol or acetone to remove the tackiness. I've tried it both weighed on a scale and measured in cups. Same result. I used exact methods I used with the 150. I use squeeze bottles. I will try both the Q Cells and silica next time.

As for RP. We seem to be on the same page. The white "part" of the RP was enough to cause an anxiety attack. I need 7 grams and have 5 on the stick. Dip it in and scoop some more out, now I have ...5 grams. Try again and now I have 4 grams. Lol. Set the stick on the cup to weigh it, turn your head and it runs off the stick onto the cup, scale, and table. Grrr So much easier to squeeze stuff out. They should put it in a caulk tube.
 
One thing about 635 and 150 is cure temp, it needs to be over 50°F or it will take forever to cure.
 
RP mixes in a 1 to 1 ratio and is somewhat forgiving. I've found weighing isn't necessary.

If you get yourself a couple of mustard/ketchup squeeze bottles (or something similar) you can just squeeze two equal lines next to each other. That should be a good enough measurement.
1d2ce40d-47a1-47fc-8f63-195e2630ea59_1.b9a0accb35b782f955976c521ce650f8.jpeg
 
Yeah RP instructions did say eyeballing was okay iirc. Have you tried squeezing it out of a bottle? How the heck you get it in there? I'm calling BS on this one...sorry. Lol
 
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MikeyDSlagle said:
Yeah RP instructions did say eyeballing was okay iirc. Have you tried squeezing it out of a bottle? How the heck you get it in there? I'm calling BS on this one...sorry. Lol
Click to expand...

You're killin' me, Smalls.

Rocketpoxy runs when it's fresh. The hardener thickens/stiffens with age. How old is your RP?
 
This was a three-year-old thread that someone resurrected. OP has not posted in three months.
 
Exactimator said:
You're killin' me, Smalls.

Rocketpoxy runs when it's fresh. The hardener thickens/stiffens with age. How old is your RP?
Click to expand...

LOL

Which is the hardener? The brown? Or the white? The white (mine at least) will run slowly and self level, but doesn't exactly flow. I can tip the jar upside and hold it for probably close to a minute before it starts to slide out. But the brown side no way. It is like creamy peanut butter, maybe mixed with toothpaste. I used it within a week of getting it and it was this way then. Got it from Wildman's earlier this year. Maybe it was old stock.


Bat-mite said:
This was a three-year-old thread that someone resurrected. OP has not posted in three months.
Click to expand...

Good, then I wont feel too bad about hijacking it for a RocketPoxy discussion. :)
 
MikeyDSlagle said:
LOL

Which is the hardener? The brown? Or the white? The white (mine at least) will run slowly and self level, but doesn't exactly flow. I can tip the jar upside and hold it for probably close to a minute before it starts to slide out. But the brown side no way. It is like creamy peanut butter, maybe mixed with toothpaste. I used it within a week of getting it and it was this way then. Got it from Wildman's earlier this year. Maybe it was old stock.
Click to expand...

The brown stuff is the hardener. I think. Now I'm second-guessing which component it is. But it's definitely the one that gets stiff. Maybe it was old stock, or maybe it was the temp when you were using it. I don't know. I DO know that it gets stiffer with age, and if I don't use mine up within a year I have a hard enough time working it (or squeezing it out of the bottle) that I throw it out and get fresh. I guess the other alternative would be to keep building rockets so I ran out before it got old, but then I'd run out halfway through the last rocket. So I'd buy more. Then I'd be on a rocket build/epoxy purchase treadmill that would end with me getting a second mortgage.

I get what you're saying though. Neither of the RP components squeeze out of a bottle easily as BS 5 minute epoxy even when it's new.
 
Exactimator said:
I DO know that it gets stiffer with age, and if I don't use mine up within a year I have a hard enough time working it (or squeezing it out of the bottle) that I throw it out and get fresh.
Click to expand...

I've bought two small batches of RP from Apogee, and one from Mad Cow. All three batches were way too thick to use in a squeeze bottle, even when new. Aeropoxy flows really nicely though. I don't think it's due to climate here either, it's always been between 70-90 when using it.
 
Weather isn't the issue here. I was using it last month - July in Louisiana is 90+ degrees so not too cold.

Maybe Mr Rocket Poxy himself will chime in and offer me a free sample of some hot off the press so I can see if sure fire new stuff is better than what I have.
 

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