Thickening and strengthening epoxy

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Four centering rings are used because it's a split fin model. I like to sandwich my fins between centering rings. Plus, a 4" to 3" G10 centering ring only weighs a few ounces, and weight is not a concern for this model. Also four centering rings were not included with the kit, only three are, I just like having that fourth one.

While I agree Rocketpoxy does stay in place quite nicely, t just wasn't my choice this time around. Pulling the internal fillets by hand is something I've wanted to do for a while, just haven't had enough clearance in between motor mount and body tube to get it done recently (4-3", 3"-54mm, ect.)

I use the same method on my builds, always a CR at each end of the fin, ist just one more area to get a solid bond. In the picture below you can see how I slot the CR's to allow the fins to self jig as well, which has turned out to be well worth the extra effort, here the fins are dry fitted as the CRs are already bonded. The 1/4" dowels server no real purpose other than making sure the rings stay in alignment, and I just left them in as they have minimal weight impact overall. The rings were filleted to the MMT prior to installation and then the CR to airframe and fins were injection filleted. The fins are fiberglass laminated 1/8" ply and have very little flex. This assembly is in my L2 cert rocket a 3" Frenzy XL clone.


L2project8-2.jpg
 
I use the same method on my builds, always a CR at each end of the fin, ist just one more area to get a solid bond. In the picture below you can see how I slot the CR's to allow the fins to self jig as well, which has turned out to be well worth the extra effort, here the fins are dry fitted as the CRs are already bonded. The 1/4" dowels server no real purpose other than making sure the rings stay in alignment, and I just left them in as they have minimal weight impact overall. The rings were filleted to the MMT prior to installation and then the CR to airframe and fins were injection filleted. The fins are fiberglass laminated 1/8" ply and have very little flex. This assembly is in my L2 cert rocket a 3" Frenzy XL clone.


View attachment 276376

I have absolutely no flex in my fins (also a frenzy XL, although 4"), but that can be attributed to the 3/16" G10 laminated with carbon. Fins are secured via "double dip" in proline, then injected with west systems. While it may not be the strongest fin attachment, it is easily the strongest I've ever done, and no fin that I've ever "double dipped" has ever come off. I'm sure my fin can will survive very many flights in the 75mm diameter. Someday after getting my L3 I'll put some crazy M motor in it.
 
I have absolutely no flex in my fins (also a frenzy XL, although 4"), but that can be attributed to the 3/16" G10 laminated with carbon. Fins are secured via "double dip" in proline, then injected with west systems. While it may not be the strongest fin attachment, it is easily the strongest I've ever done, and no fin that I've ever "double dipped" has ever come off. I'm sure my fin can will survive very many flights in the 75mm diameter. Someday after getting my L3 I'll put some crazy M motor in it.

I do the same double dip technique as well, first heard about it from one of CJ's builds, and you definitely should have zero flex with carbon laminated G10 fins. Your fins are TTW and filleted internally and externally, without T2T you can't get much stronger, your Frenzy is also FG iirc, it should easily handle an M.
 
I do the same double dip technique as well, first heard about it from one of CJ's builds, and you definitely should have zero flex with carbon laminated G10 fins. Your fins are TTW and filleted internally and externally, without T2T you can't get much stronger, your Frenzy is also FG iirc, it should easily handle an M.

Yup. That's what I thought. Except no Ms for me for a while, they're expensive and I want to get L3 in style (N motor, lol)
 
Some quick facts: West system epoxy is basically an unfilled epoxy made as a laminating epoxy I am not knocking it but just want you and others that may read this to know some of the differences of the epoxies being talked about on this thread. West system would be good for laminating fiberglass cloth to a plywood fin or fiberglass cloth to a cardboard tube or something similar. That is why West system epoxies have a thin viscosity of less than 1,000 centipoise, so the epoxy can flow around and into the fiberglass cloth, that is why they are called laminating epoxies. If you are purchasing a kit that has a filament would tube with G10 fins this would not be near as good a choice as using a filled high strength epoxy because you are not laminating the fiberglass cloth or fiberglass thread into a tube, the filament wound tube and G10 sheet manufacturer has already done this for you, you are at this point needing a high strength structural filled epoxy to assembly the tube and G10 fin and components for the best results. To use an unfilled epoxy similar to West System you would first need to add lots of fillers and thickening agents to make it anything even close for bonding strength to a filled high strength structural epoxy such as Rocketpoxy G5000. Rocketpoxy G5000 is in an epoxy classification called filled high strength structural epoxies. That is why Rocketpoxy has a viscosity of 350,000+ centipoise (basically a paste). If you love to formulate epoxies and have the time and knowledge to purchase, add, and mix the correct amounts and types of fillers needed to make a superior high strength filled epoxy then the west system unfilled epoxy is for you, if you want a high strength structural filled epoxy to use right out of the jar where an expert chemist with lots of test data has already done all the hard work for you by adding and mixing in the exact formulation of fillers then use something like the Rocketpoxy G5000. That is why filled epoxies do have better physical properties than unfilled epoxies for structural assemblies such as filament and carbon fiber wound tubes, G10 and carbon fiber sheet products, metals, plastics and generally any composites. Most serious composite assemblers that wish to use an epoxy ready to build with will prefer them, also that is why filled epoxies may cost a little more than an unfilled epoxy.

Also when comparing Rocketpoxy to an epoxy such as the Bob Smiths 20 or 30 minute epoxy or Proline 4500 the Bob Smith and Proline would be more brittle and have less bonding strength with some composite materials especially plastics and aluminum. Yes one of the major tradeoffs of a higher temp and faster setting epoxy is that they generally become more brittle. We feel that Rocketpoxy G5000 is the perfect tradeoffs of high strength, not brittle, curing time, and a decent temperature rating that is good for about 98% of all high powered flights. You may have a little more of a learning curve with the Rocketpoxy and may have to be a little patient about the curing times but it will give you a great finished product where lots of fin flexing and even some hard landings will not crack the epoxy. I’ll give you a quick test you can do put about ¼ - 3/8 inch layer of your West system, Proline , and Rocketpoxy G5000 epoxy into a plastic cup and let it harden, then whack all your samples with a hammer, you will notice quickly which epoxy did not shatter like brittle glass ( hint the RP G5000 will not easily shatter) , you will also notice which epoxy bonding strength stuck to the plastic cup and which epoxies ere easily popped off (you will not be able to separate the Rocketpoxy G5000 from the cup). You can have a higher temp and faster setting epoxy but if it is very brittle and less bonding strength this may cause failure well before any temperature comes into play. I’m not trying to get all the West systems, Bob smith and Proline users panty’s in a bunch, all these epoxies have their place and I sure as well know how this forum can get at times and not looking into getting into a big back and forth with this. If it works great for you more power to you, I’m just trying to answer a few questions I have been asked about this. Since my company is the Manufacturer of Rocketpoxy I do feel it is important to get the facts straight from the manufacturer who has actually done a lot of lab work and test data on this.

Excellent information! Thank you! Sold here.
 
The problem is that if I'm ordering something, it's going to be more proline 4500. I just wanted to know if there was anything that I could find kicking around my workshop that would work to strengthen the west systems so I could get started on my fin can.
There are no guarantees going this route, but I can give you one success story. Wood meal. We had some on hand when my friend mixed up some epoxy, thought it looked to thin, tried it, and it worked out fine. I don't know what epoxy he was using. The wood meal we have is like fine sanding dust, pretty much like flour. He used it to assemble his motor mount and attach his fins. The rocket went both supersonic and a mile high. It then crashed after a recovery failure, and I needed a 14 inch steel pipe wrench (because I didn't have a hammer handy) to salvage the parts.

So if you've got a dust collector on your sanding equipment you might try the stuff in the collection bag, but I must repeat there are no guarantees.

If your in an experimental mood, try flour or corn starch. Or saw dust, which is courser than the wood meal and has somewhat lengthy fibers so might act like a weaker but not too weak alternate to chopped glass or carbon fiber. How about dryer lint? But these are all experimental and very risky.

Of course, you could give materials like this a shot on scrap and test the results. Even if you do, it'd be impossible to simulate flight conditions, so it's still quite risky. The wood meal is my only success story and that's only one anecdote; the rest is just brain storming.
 
There are no guarantees going this route, but I can give you one success story. Wood meal. We had some on hand when my friend mixed up some epoxy, thought it looked to thin, tried it, and it worked out fine. I don't know what epoxy he was using. The wood meal we have is like fine sanding dust, pretty much like flour. He used it to assemble his motor mount and attach his fins. The rocket went both supersonic and a mile high. It then crashed after a recovery failure, and I needed a 14 inch steel pipe wrench (because I didn't have a hammer handy) to salvage the parts.

So if you've got a dust collector on your sanding equipment you might try the stuff in the collection bag, but I must repeat there are no guarantees.

If your in an experimental mood, try flour or corn starch. Or saw dust, which is courser than the wood meal and has somewhat lengthy fibers so might act like a weaker but not too weak alternate to chopped glass or carbon fiber. How about dryer lint? But these are all experimental and very risky.

Of course, you could give materials like this a shot on scrap and test the results. Even if you do, it'd be impossible to simulate flight conditions, so it's still quite risky. The wood meal is my only success story and that's only one anecdote; the rest is just brain storming.

Yeah I've actually started saving my scrap carbon and fiberglass cloth for that purpose.
 
Some quick facts: West system epoxy is basically an unfilled epoxy made as a laminating epoxy I am not knocking it but just want you and others that may read this to know some of the differences of the epoxies being talked about on this thread. West system would be good for laminating fiberglass cloth to a plywood fin or fiberglass cloth to a cardboard tube or something similar. That is why West system epoxies have a thin viscosity of less than 1,000 centipoise, so the epoxy can flow around and into the fiberglass cloth, that is why they are called laminating epoxies. If you are purchasing a kit that has a filament would tube with G10 fins this would not be near as good a choice as using a filled high strength epoxy because you are not laminating the fiberglass cloth or fiberglass thread into a tube, the filament wound tube and G10 sheet manufacturer has already done this for you, you are at this point needing a high strength structural filled epoxy to assembly the tube and G10 fin and components for the best results. To use an unfilled epoxy similar to West System you would first need to add lots of fillers and thickening agents to make it anything even close for bonding strength to a filled high strength structural epoxy such as Rocketpoxy G5000. Rocketpoxy G5000 is in an epoxy classification called filled high strength structural epoxies. That is why Rocketpoxy has a viscosity of 350,000+ centipoise (basically a paste). If you love to formulate epoxies and have the time and knowledge to purchase, add, and mix the correct amounts and types of fillers needed to make a superior high strength filled epoxy then the west system unfilled epoxy is for you, if you want a high strength structural filled epoxy to use right out of the jar where an expert chemist with lots of test data has already done all the hard work for you by adding and mixing in the exact formulation of fillers then use something like the Rocketpoxy G5000. That is why filled epoxies do have better physical properties than unfilled epoxies for structural assemblies such as filament and carbon fiber wound tubes, G10 and carbon fiber sheet products, metals, plastics and generally any composites. Most serious composite assemblers that wish to use an epoxy ready to build with will prefer them, also that is why filled epoxies may cost a little more than an unfilled epoxy.

Also when comparing Rocketpoxy to an epoxy such as the Bob Smiths 20 or 30 minute epoxy or Proline 4500 the Bob Smith and Proline would be more brittle and have less bonding strength with some composite materials especially plastics and aluminum. Yes one of the major tradeoffs of a higher temp and faster setting epoxy is that they generally become more brittle. We feel that Rocketpoxy G5000 is the perfect tradeoffs of high strength, not brittle, curing time, and a decent temperature rating that is good for about 98% of all high powered flights. You may have a little more of a learning curve with the Rocketpoxy and may have to be a little patient about the curing times but it will give you a great finished product where lots of fin flexing and even some hard landings will not crack the epoxy. I’ll give you a quick test you can do put about ¼ - 3/8 inch layer of your West system, Proline , and Rocketpoxy G5000 epoxy into a plastic cup and let it harden, then whack all your samples with a hammer, you will notice quickly which epoxy did not shatter like brittle glass ( hint the RP G5000 will not easily shatter) , you will also notice which epoxy bonding strength stuck to the plastic cup and which epoxies ere easily popped off (you will not be able to separate the Rocketpoxy G5000 from the cup). You can have a higher temp and faster setting epoxy but if it is very brittle and less bonding strength this may cause failure well before any temperature comes into play. I’m not trying to get all the West systems, Bob smith and Proline users panty’s in a bunch, all these epoxies have their place and I sure as well know how this forum can get at times and not looking into getting into a big back and forth with this. If it works great for you more power to you, I’m just trying to answer a few questions I have been asked about this. Since my company is the Manufacturer of Rocketpoxy I do feel it is important to get the facts straight from the manufacturer who has actually done a lot of lab work and test data on this.

I've never used Rocketpoxy and don't know the difference in strength between that and West. When West 105/206 is mixed with the 405 filleting compound, it's extremely strong. Assuming equal sized batches of West with 405 and Rocketpoxy, both mixed perfectly, with the appropriate level of rocket prep, how much stronger is the Rocketpoxy?
 
Quick comment I have on questions I have been asked on injection internal fillets, I personally don't like drilling injection holes in my FW tubes (making stress concentration holes right next to the slots doesn't do it for me) plus it wastes a lot of time to drill these, also trying to make sure everything inside is "leak proof" you know where every part has to be butted up together so no epoxy leaking though the motor centering rings can occur is difficult, tedious and time consuming and do not find any advantages to using the “injection" method, also I like to be able to see the internal fillets when finished, with injection method using black or colored FW tube this is not possible. I think this was originally developed because it was basically the only way you could do it when using the thin runny epoxies, I find it much easier to simply use a 1/8” to ¼” diameter wooden dowel to build my internal fin fillets laying the rocket horizontal and going in through the bottom and attaching the motor mount rear ring on afterwards, really this is pretty fast once you get the hang of it, you simply just dip the end of the dowel into the mixed Rocketpoxy twirl it a little to build up on the dowel, then go in the aft side of the rocket and twirl the Rocketpoxy into the fillet locations, you can see the internal fillets when finished and make them exactly how thick you want them, no guessing. I have even done minimum diameter rockets this way as well. I do four fillets per 120 degree rotation (for a 3 fin rocket), the two internal fillets on the bottom single fin, and the top two internal fillets on the two top fins per rotation, (or if you really want to speed things up and are quite coordinated you can also do the two external top fin fillets as well at this time). Do this three times and you done with the most unbelievable rocket strength, no injection drill holes needed. If you have an extreme minimum diameter with little to no space where it is near impossible to get a dowel in between the inside of the airframe and outside of the motor tube one technique that is used with great success is again go in from the bottom end and just to pour a little into the area you want to make an internal fillet and tilt the rocket tube to get it to flow where you need it to be, if you use about 15 to 30 minutes after mixing the Rocketpoxy will still flow when the tube is tilted but will still be stiff enough to stay put once tube is level again.

The Rocketpoxy was designed to give you about three viscosities to work within a single epoxy product. From the time you first mix it for about the first 0 to 20 minutes it will flow freely and self level pretty well and can be poured directly from a cup or even put into a syringe with a decent size dispense spout and injected quite well, especially if you have a larger size opening (1/8”diameter or more) or very easy if using a pneumatic dispenser, with this device a piston is forced by air pressure down into the syringe to push out the product, you can easily do very thick materials this way. If you want it to be a little flowable but really with no sags or runs but still trowels well and smooth (such as when doing a fin fillet) use it from about 30 to 45 minutes later after mixing, if you want to use it like a very thick epoxy putty wait after about 45 to 60 minutes and dip you fingers in isopropyl alcohol and you can pinch out an amount and roll into a ball or any shape and press into threads or a hole to repair. You can use up to 1 hour after mixing. Keep in mind the above is approximately and your exact conditions may need to be adjusted slightly, the temperature the epoxy is mixed at and the amount mixed will affect this (will cure faster in a 90 Degree F shop then a 60 degree F shop and will cure faster if mixing a very larger amount).

I wanted to comment on the internal fillet discussion in this thread... I am putting together a Madcow Frenzy mini (from a pre-BF purchase). I decided to build it with Rocketpoxy alone (normally on bigger rockets I use 3 to 4 different epoxies). I double dipped the root edges of the fins for insertion. I am aware that this is normally done primarily for wood glue to increase initial tack so the fins stay in place, but I wanted to get more epoxy into the slot. My plan was then to go in and apply internal fillets as suggested by John above even though it was going to be tight quarters. After cure on the first fin set I removed the rear CR and then began to really see the advantage of using a low viscosity adhesive like RocketPoxy. Take a look at the setup on the internal fillets. I did nothing here except let it settle and cure. Given the shape and fill along the root edge, I don't have to do any application of an internal fillet. Of course, I am talking about a small rocket here and doubt if it would apply to my normally larger sized rockets, but for this application a very nice surprise showing positive outcome using RocketPoxy!

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