I've used epoxy a good bit, but I can't say I've ever come across that problem. I think I can sort of get a couple ideas out to you that might be of help.
First off, it sounds as if you're possibly applying too much epoxy at one time. Outside of the fact that it will take a bit longer, there is no reason that epoxy can't be applied in several coats to achieve the desired size for the head of your fly. If I'm wrong about that, you may want to try waiting a couple minutes to let the epoxy thicken up just a touch before applying it. You've got to work fast with 5 minute epoxy, but you don't have to work so fast that neatness has to be sacrificed. One thing I do a lot when I use epoxy (and you'll need a rotary vise for this of course) is just to rotate the fly while its still in the vise to give it a minute or two to set up enough that the shape is solid. I've never used a drying motor, but I've never had any problem with using epoxy while spinning the fly in the vise. Actually, that brings one thing to mind too. I'm sure someone on the list knows how to do it, but I can't imagine trying to apply 5 minute epoxy without a rotary vise. It offers advantages when applying the stuff which I can't really imagine doing without. There are also other things you can use to build up a head which will lessen the amount of epoxy that you need to apply. One of my favorite things to do to modify epoxy heads is to wrap the shank of the hook with krystal flash or something else with some sparkle to it and then build up the head a bit with monofilament tying thread. You can easily achieve a head of any size and shape you desire this way, and while its not quite as clear as epoxy on its own, its a LOT faster when trying to build up a larger head. Various things materials can be used under the mono to achieve different effects. One of my favorite epoxy flies to tie is one that also helped me synchronize my expectations of epoxy with its actual working characteristics. Joe Bruce's epoxy spoon fly follows: Mustad 94007 or 94011 hook (whichever is the long shank one) Thread - Clear monofilament Frame - roughly 50# coated wire leader material Body - 5 minute epoxy and glitter Start by bending the hook shank back about 20 degrees approximately 1/3 of the shank length back from the eye (bend to the side opposite the point of the hook) Second, cut off about a 6 inch piece of wire, and lash it to the hook right behind the eye at mid-length on the wire - similar to attaching a set of lead eyes. Next tie in a tail material of your choice - Joe has something he recommends, but I don't have the pattern in front of me. Pretty much anything roughly the length of the shank of the hook will work. Bend the loose ends of the wire back along the sides of the hook shank and bind them to the shank. The coated wire leader material will produce a really nice looking smooth curve. Cut off the wire at the end of where its been bound to the hook. Mix up your epoxy and add a little bit of extremely fine glitter and just a touch of coarse glitter to it. Roll your bodkin in the epoxy/glitter mix and get a nice smooth coat of it on there. Take the bodkin and get the epoxy right where the wire intersects with the shank of the hook. You'll have to do this operation two times - once for each half of the spoon. Take the bodkin and drag it along both the wire and the shank of the hook. Sooner or later, the epoxy will fill the opening created between wire and shank on one side of the hook. Just keep sliding the bodkin along the wire and shank over and over until you end up with a full sheet of epoxy laid in there in one pass. When you get the first side done, the second side should be much easier because the epoxy still on the table has been sitting there just about the same amount of time as what you just put onto the hook. If there are any questions about the fly, please feel free to get in touch with me on or off list, and I'll do my best to help. I know the pattern for that fly might read a little funny, but it really helped me get a clear expectation of what i could expect from epoxy, and its a really good saltwater fly anyway. John
