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A different breed of adhesive
Text, photos and video by Tom Hintz
Posted – 11-16-2015
When I was building my ESM 88” Zero a company named Epo-Grip sent me a few versions of their unique epoxy adhesives. Though I am often optimistic when someone claims to have a better product the Epo-Grip adhesives greatly exceeded my expectations on a couple levels.
Though I frequently look to epoxy for strong joints the strength of the Epo-Grip epoxy joints easily surpassed anything I had used in the past. Even more impressive is the consistency of the Epo-Grip epoxies and how that impacts their use. Epo-Grip makes these epoxies to have a consistency similar to petroleum jelly. Add to that the different versions of this epoxy design and Epo-Grip is blazing their own territory in the world of adhesives. Like any adhesive, you can compromise the strength of the joint with poor preparation so you still need to hold up your end of the deal.
Epo-Grip epoxies have been used in industrial settings for a long time and while some hobbyists have discovered them (like a friend of mine that is responsible for me finding out) I think the model airplane and woodworking communities need to pay attention. To service this wider market Epo-Grip epoxies are available in a wide range of package sizes. 4oz Units- (New Size), 8oz Units, 16oz Units, 1 Quart Units are available through the Epo-Grip web site listed below.
When you need super strength of the joint and a long time to get it assembled the Epo-Grip #30 is the best choice of the Epo-Grip offerings. A leisurely 4-6 hour set up time takes the rush out of the work. A consistency similar to petroleum jelly means that when applied in reasonable quantities this epoxy will not sag or run. I have to admit that it was the consistency of the Epo-Grip epoxies that initially caught my attention but I was surprised by the strength of the bonds these adhesives generate.
Another handy feature of the #30 Paste is 50/50 mix ratio of the A and B parts with a built in fudge factor that means if you miss those exact proportions a little the resulting epoxy will still work just fine. Plus the manufacturer literature claims that the #30 Paste is good for bonding wood, Styrofoam, carbon, composite materials, fiberglass, glass cloth, metal and most ABS materials. Because of its consistency you can add fillets to the joint as you assemble it and often produce a sanding-ready joint. I love the #30 paste for hinges, both flat and Robart pin-style.
The Clear Paste is the most like traditional epoxies in the Epo-Grip line but there are beneficial differences for the hobbyist. This also is a 50/50 mix epoxy but is sets up in 7-10 minutes at normal room temperature 77F. The Epo-Grip Clear Paste is thicker than regular epoxies so it is more controllable. That combined with the relatively quick set up time once again give the modeler more options when building or making repairs. The faster set time makes the Epo-Grip Clear Paste a good product for at the field repairs as well as in-shop work. Prepare the surfaces to be joined properly, as you must with any adhesive and the Clear Paste works very well with wood, Styrofoam, carbon, composite materials, fiberglass, glass cloth, metal and most ABS materials.
Model Matrix is an interesting variation in the Epo-Grip lineup. This epoxy is also a 50/50 mix with a relatively quick set up time of 7-10 minutes. What makes the Epo-Grip Model Matrix epoxy my go-to adhesive for assembly of high-stress joints as well as repairs of this type of joint is the milled fiberglass reinforcement built in the material for extra strength properties. Prepare the pieces to be joined properly and you can expect superior strength with wood, Styrofoam, carbon, composite materials, fiberglass, glass cloth, metal and most ABS materials.
I have found the Epo-Grip Model Matrix makes unexpectedly durable repairs in materials considered fragile like plastic and thin fiberglass often used parts like wheel pants. If I can break it at the field, I trust repairing it with the Epo-Grip Model Matrix epoxy.
In the Shop
There is one way in which the Epo-Grip products are identical to traditional epoxy. It is just as easy to mix too much Epo-Grip adhesives as it was mixing too much of regular epoxy. This is all on us and requires only a bit of self-discipline to correct.
Also, where we are used to swirling regular epoxy in a cup with a stick the Epo-Grip epoxies are best mixed by folding it over itself on a flat piece of cardboard, plastic or wood. Once you get used to doing it this way you get a more complete mix more quickly which leaves more of the open time in which to apply it.
The folks at Epo-Grip sent me an artist pallet knife along with samples of these epoxies. Normally manufacturers include “extra” things as a thinly veiled bribe but Epo-Grip just wanted to show how easy it is to work with their product when using the right tool. To that end, the pallet knife was spot on. Now I can’t imagine using anything else to mix and apply Epo-Grip epoxies.
While evaluating the Epo-Grip epoxies I did the mandatory gluing of pieces of wood and then breaking them to see how tough the joint was. While all of those joints showed exceptional strength of the adhesive I had an all-too-common and much tougher real-world job in the shop that should be more of an extreme test of these epoxies.
I had made an inappropriate landing with my ESM 88” Zero that ripped the retracts out of the wing. Piecing this damage back together demands superior strength of the joints. I also was hopeful that the consistency of the Epo-Grip epoxies would let me create small fillets between the parts surrounding the retracts to add more strength and vibration resistance.
I chose the long setup time Paste Epo-Grip epoxy for installing the main gear block assemblies back into the wing. I had already pieced the balsa pieces back together surrounding the main gear blocks with CA but because of the expected shock and stress the blocks would see along with combinations of balsa, hardwood and plywood the Epo-Grip is the best choice.
Since most of the actual joints to be glued are hidden once the pieces are in place the thick consistency of the Epo-Grip long set epoxy made it much easier to apply the epoxy to all surfaces before assembly. Despite the time needed to get these pieces situated properly I knew the Epo-Grip epoxy would not run and reduce the adhesive grip area nor the strength of the joint. Once the pieces were in their final position I applied light clamping pressure to be sure they did not move before the Epo-Grip epoxy set up. Then probably most important, I quit messing with it and let the epoxy set up!
A few days later I was able to take the ESM 88” Zero to the flying field to see if the Epo-Grip epoxies held up to the real world of bumps other stresses. I made a few flights each with several practice touch-and-go’s. Between all of the taxi time around the field and several landings the Epo-Grip repair held fast. I even had a couple less than perfect landings which presented unplanned shock tests of the repairs but all held just fine.
After we put the camera away I decided to make “one more flight” something RC pilots usually avoid saying out loud because it tempts the high priestess of crashing. I however said it out loud. On what obviously would be the last landing I flat screwed up and dorked the ESM 88” Zero in nose first. The Epo-Grip did its job and clung to the surrounding wood. Unfortunately there was enough force that the wood surrounding the repair gave up. Where before the landing blocks pulled out of the wing, the Epo-Grip forced the whole wing to give way around the original repair.
If you are a woodworker or a RC hobbyist, the Epo-Grip epoxies should be of interest. The joint strength is exceptional and the consistency makes applying the adhesive far easier than anything I have used. I certainly did not want to destroy a giant scale airplane but that crashed shows that the Epo-Grip epoxies are tougher than the material they are bonding.
You can see the pricing for Epo-Grip epoxies at the link below but in my world the cost is not a real consideration. The superior strength and the ingenious consistency takes ease of use to a whole new level while insuring a better bond because the adhesive stays where we need it. You need to get some of the Epo-Grip epoxies and try them for yourself, in hour conditions. I think you will be pleasantly surprised!
Visit the Epo-Grip web site - Click Here
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