To get epoxy down into a tight spot (forward centering ring, etc.) without making a mess, you can make a fat straw out of wax paper and pour the epoxy through it. Several wraps around a dowel of the appropriate size held in place with full wraps of masking tape in several places does the trick. Don’t wrap it too tight or the paper will curl up inside when you pull it off the dowel. I use a 1/2” dowel. It gives a wide enough (just barely) opening at the top to pour into, the epoxy runs through it fairly well and it’s small enough to aim the drippy end with some success.
After applying a BT/centering ring fillet, I could often be seen in the back yard tossing the BT into the air with a spin to evenly distribute the epoxy. I did it in the grass because I sometimes missed a catch. :-) No more. Toss a string over one of the exposed 2X4’s overhead in your garage, then tie a knot in each end. Tape the two knotted ends of the string to opposite sides of the end of the BT you just poured the epoxy into. The closer they are to 180 degrees apart, the less wobble you get. Now give it a spin, and another, and another. When you get tired, let it unwind for a while. Less work, no dents.
Submitted by: Mark James
The most important tip I can come up with about working with epoxy is “Think disposable.” I use disposable PLASTIC cups, PLASTIC plates, PLASTIC spoons, brushes, mixers, measures and gloves.
Note the emphasis on “PLASTIC.” Anything that will contain epoxy as it exotherms needs to be able to stand up to some high temperatures. Foam cups or plates are a “No Go,” and will foul up your epoxy. Some plastics won’t make it either, but it depends on the epoxy and the conditions of it’s use.
Plastic spoons and wooden popsicle sticks are good cheap disposable mixers and applicators. Popsicle sticks can be had at most craft/hobby stores for pennies per hundred. Wal-Mart sells some 1/2” plastic handled brushes for about $.50 each. They can be cleaned several times without shedding bristles, but can be tossed when you are done, or get stuck with a hot batch of epoxy on your brush :)
Paper towels are good for quick spills and clean-ups. I try to keep a good cotton rag and acetone close by too, to wipe up spills/drips when it begins to get a little sticky.
As far as heat, you can use heat (from a blow dryer or heat gun, etc) to lower the viscosity of most epoxies, when you first mix it up. Work fast though, because once it gets hot, it’ll gel very quickly.
If you want to achieve the maximum working time advertised by the manufacturer, work with mixed epoxy spread out thin on a plastic plate. It will take much longer to exotherm, as compared to being stacked up in a cup. Stay in a cool/shaded area too. High ambient temperatures will accelerate exotherm.
Most importantly… Safety!! All epoxy is nasty!! Many people have bad reactions immediately, while others suffer from the cumulative effects of exposure. Always wear a respirator that filters vapor AND work in a well ventilated area. Don’t use rubber gloves, use the thicker vinyl/plastic ones that actually keep the epoxy residue off of your hands, and change them as often as needed to keep the epoxy from clumping up on the finger tips. When you do need to clean epoxy off of your skin, use waterless hand cleaner.
Q: Why would you do this? Doesn’t the faster cure defeat the purpose of using epoxy in the first place?
Not necessarily. It all depends on the situation. If you need the epoxy to “wick” in to a joint, it’s got to be thin. When laminating, there are occasions where I need to heat and thin the resin after application of the resin and fabric, and dab off the excess. It all depends on the materials being used, and the characteristics of the chosen epoxy system.
If you are “stuck” in an epoxy emergency at 11:45 Sunday night, live in the boonies (like I do), and only have Wal-Mart Dev-con 30 minute super thick stuff and need to finish a lamination, a little heat goes a Looooong way to providing the consistency you need to finish up :)
Yup. There are trade offs. Heat will definitely speed the exotherm process. It could be speculated, though, that the water-like consistency of warmed epoxy soaks into the materials being bonded faster than it does when it’s thick. After all, that is the point of using slow cure epoxies with cardboard and Phenolic “like” materials. Does heated thin resin need to be viscous as long as it does in it’s cool thick state? Good question, right? Maybe John could include some tests with both room temp cure and accelerated (heated) cure when he gets his epoxy testing apparatus in working order.
Submitted by: Chuck Andrus
West Systems even recommends a little heat to let the epoxy “flow” smoothly. To contrast with Chuck, though, I apply the resin first, then hit it with a little heat from an infrared lamp to make it flow better. That way, when the boosted exotherm kicks in, your epoxy is already happily in place. This heated thinning works well for the finish coats of epoxy: West 206 rolls on with small ripples, but after heating, it flows like paint to a smooth finish.
Surprising to me, a little heat applied after the initial cure is beneficial to the long term strength of the epoxy. Just never bring West Systems past about 140 degrees or so. In a recent email exchange with Eric at Dynacom, he mentioned that he post-cure heat treats some parts at about 70 degrees Centigrade.
Here’s a hint for new West System pump users: I’ve found that the smaller pump used in the hardener cans tends to develop bubbles more than the big pump in the big epoxy cans. So, after you’ve squirted in two squirts from the big pump, then only a squirt and a half from the little pump, the whole mix is ruined, and you have to throw it away. Now I’m much wiser, and squirt from the little pump first. If it spits air rather than squirting hardener, I only throw the hardener away.
I use the full-bodied West 205 hardener when I’m laying up open weave cloths like kevlar and boat cloth, or unidirectional carbon fiber. It fills the open weave better than 206.
When laying up a wrap of glass, I’ll paint the tube first with the 205 mix because it anchors the first wrap better than the 206 mix. After the cloth is down, I’ll roll on some 206 mix because of its increased penetration and superior wet-out.
I use peel ply to smooth out overlaps and to absorb excess resin. Peel ply is a fine weave nylon cloth that applies like 2 oz glass, but magically peels off after the resin has cured.
And I still use Bob Smith epoxy for many construction details, like payload bays.
Submitted by: Jim Jannuzzo
Here’s how to avoid losing epoxy when the hardener spits air:
Buy those 6 packs of Jello-brand ready-to-eat pudding. Clean the cups when finished, use them to mix epoxy. If you start with a clean cup and get air in your hardener, pour it back into the can rather than through it away. ;-)
Submitted by: Darrell Mobley
- When using thickened epoxy (any brand, any thickener) first mix the resin and hardener together. When thoroughly mixed, then add the thickener to achieve the desired consistency. This will insure that filler doesn’t interfere with completely mixing the resin and hardener.
- When using thickened epoxy , “wet out” the surfaces to be bonded with unthickened epoxy first. Then apply thickened epoxy and fit the parts together. Epoxy resin will wick into the parts to be joined (which you want to maximize the substrate-epoxy joint), but if thickened epoxy is applied directly you’ll wind up pulling the epoxy out of the epoxy/filler mix yielding a resin-starved joint. Since you’ll be mixing the raw epoxy first (see #1), just brush some on the parts before mixing in the filler.
- When multiple applications of epoxy are required (such as multiple layers of glass, or filling the weave of a glass layup), try to complete each application before the previous application achieves final cure. This will cause the second application to bond chemically, rather than mechanically to the first application, producing a stronger bond.
- To elaborate a bit on (2 & 3): Epoxy bonds to surfaces by a mechanical joint–it penetrates porous materials and “locks in” to the nooks and crannies. Non-porous parts must be roughed up in order for the epoxy to have something to “grab on to”. However epoxy will bond chemically to itself, even a prior application, provided the prior application has not achieved full cure. This means that if you’re bonding with fillers, you don’t have to immediately follow the “wet out” step with the “bonding” step. Hours can go by, providing the first application doesn’t fully cure.
- Always mix epoxy exactly as per the manufacturer’s recommendation. Epoxy cure is not a catalyzed reaction such as Polyester where more catalyst will accelerate the reaction. Additional hardener (or resin) will not have anything to react with, and so you’ll be left with a sticky mess.
- Never thin epoxy unless the manufacturer recommends it. If the epoxy you’re using is too thick for the job, switch to different stuff. West System says that thinners will reduce the strength of the cured epoxy in direct proportion to the amount of thinner added.
Submitted by: Doug Steinfeld
Measuring: I picked up some syringes at Woodworkers Warehouse. They come with a long, almost needle-like, end and have snap on caps. The opening is just large enough to shoot West Systems through. They have larger ones, but these have been the most useful to me. They will hold a full pumps worth so you can get inside your rocket and put it where you need it. I’ve even used them to “inject” epoxy through small holes in the BT to fillet inner bulkheads. As for measuring, I took a couple of the syringes and filled one with a pump from the epoxy and the other with a pump from the hardener. I then measured how much was in each with a ruler and divided by 5. Now I can mix 1/5 of a pump for those smaller assemblies.
Clean Fillets: I’m still not up to the quality I’ve seen on some rockets but I have a pretty quick and reliable way worked out to apply fillets. I decide on the radius I’m looking for and measure off on the BT and the fin. I then apply a piece of masking tape along both those lines. With tape in place I can lay down the fillets and smooth them out without smearing all over the fin or body. I let the fillet set up just a bit before removing the tape. Once I’m sure it won’t run all over, I pull the tape up and smooth the ridge out with an alcohol soaked, gloved, finger.
Submitted by: Ted Apke
I think that the best way to apply epoxy in tight areas is to use a dowel rod and make a point on it with a disk sander or pencil sharpener. then mix the epoxy with it and use the point to put epoxy in tight places or anywhere
Submitted by: Seth Habberfield
For more precision, use a syringe. No needle, but you can get plastic tips that work very well. Pharmacy carry syringes for giving medication to infants that work well.
Submitted by: Greg Deputy
30 min epoxy fin fillets:
When applying fillets of 30 minute epoxy it is very easy to accidentally get some of the on the fins and body tube. An easy solution is to put down two strips of masking tape, one of the fin and the other on the body tube. There should be a gap between the two bits of tape large enough for the fillet that you want. Wait for the epoxy to go slight tacky, but still a bit runny and remove the masking tape. The epoxy will then still have time to “spread” out and you wont have any epoxy on the fins or body tube.
West System Epoxy thickened with filler fillets:
When making fin fillets out of West System Epoxy, thickend with an appropriate filler, make it easier by using a syringe and lolly poop stick. Firstly mix up the epoxy and thicken it as per the instructions then, while wearing disposable gloves as it can be a bit messy, fill a syringe with the epoxy mixture. Have the rocket ready and run the syringe down the fin roots and leave a bead of epoxy on the join. You could alternatively just slop a load of the epoxy in by hand but this way is much neater and stops you getting excess epoxy everywhere. Then take the lolly pop stick and run it down the bead of epoxy to make a perfect fillet. You will fin the some of the epoxy mixture will escape out the side, so either use less mixture or use the masking tape trick.
Another quick tip is when you are putting a recessed aft centring ring on after putting the fins in place is to put a wrap of masking tape round the end of the body and motor mount tubes. This means you can remove any epoxy you accidentally smeared on with ease.
Submitted by: Bob Arnott