Cork Grip Glue Lines

By Tom Kirkman

Here's a question from the Volume 2 - Issue #4 issue of RodMaker magazine:

RodMaker Magazine

"I have a question that I was hoping you could help me with. I build all of my own cork grips out of individual rings. Although I have used a "Cork Clamp" like the one Flex Coat sells in the past, my current method involves the use of a threaded rod and wing nuts. I glue up the rings on the rod, then use washers and wing nuts to clamp the rings together. This method seems to work pretty well, except I cannot seem to get rid of the glue lines! They are extremely thin mind you, but they are still there. To be honest, they don't show up until I get into 400, 600 and higher grit sand paper. I am currently using Flex Coat slow cure epoxy, or Devon slow cure expoxy. I apply a VERY thin layer to each cork ring, and them apply a good deal of pressure via the wing nuts. Am I using too much epoxy? Is the fine grit paper polishing the glue lines so they are visible? Am I not using enough pressure?

I have spoken with several other builders, and they don't seem to have a problem. One very well known fly rod designer told me that he uses waterproof glue and the lines disappear. The only problem I see with polyurethane wood glue is that it needs air or moisture to cure. I am not sure about its strength either.

The frustrating thing is when I look at commercially produced rods there aren't any glue lines at all! Are they doing something special to the cork after it is made into a grip? Possibly bleaching it?

I am hoping that you have some suggestions on how I can eliminate this problem!" ~ Andy . . . San Antonio, TX

Your clamping procedure is fine, the adhesives are fine, and I doubt you could actually use too much epoxy since any extra would be squeezed out of the joints when the grip is compressed in the clamp. In fact, I think you answered your own question when discussing your sanding routine. If you're going much higher than 400 grit paper, you may well be polishing that very fine glue line between the rings.

Without seeing one of your grips, it's hard for me to decide how much of a problem you are actually having. I suggest not worrying too much about using too much epoxy, and instead make sure you completely cover the mating surfaces with an adequate amount. The cork is quite porous and will absorb quite a bit of epoxy with any excess squeezed out as you tighten the clamp. I'd tighten the clamp until the grip is about 1/8 inch less than the length of the grip would be if we counted the normal ring lengths. In other words, if you've got fourteen 1/2 cork rings, you'd be looking at a 7 inch grip, so I'd tighten the clamp until the grip is 6 & 7/8 inches (it will spring back to 7 inches after you remove it). Assuming the rings are squarely punched, this amount of tension should be sufficient to contact all mating surfaces and push out any unnecessary adhesive. The resulting thin glue line will be quite strong.

A smooth surface finish requires sanding through many grades of progressively finer paper. I like to use Garnet paper and do my rough shaping with 40 and 80 grits, then finish shaping with 110 and 150 grits. From there I begin finishing the surface with 220 and 320 grits and finish up with a quick going over with 400 grit silicon carbide paper. The resulting grip is super smooth and shows very little in the way of any glue lines.

The Urethane glues are extremely strong and durable, although the brands I have tried were just a tad "rubbery" and did not cut at the same rate as the cork. While the glue lines were minimal, I could easily feel them with my hands and don't think they would be very comfortable to fish with. Perhaps some brands do not exhibit this tendency.

I do want to point out, that since you are not painting or top coating the finished grip with any type of opaque covering, a keen eye and close inspection may well discern the presence of the glued joint. This is normal and should not be viewed as a flaw resulting from improper technique. As far as the commercially made rod grips, I hope you are not referring to catalog photographs, which in some cases, are retouched and depict a fair bit better grip than what is found on the actual rod. ~ Tom Kirkman

Publishers note:

If you have any tips or techniques, send them along! Help out your fellow rodmakers! ~ Publisher, FAOL

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