Thursday, May 29, 2008

Glue Test #2

Posted by David Bolin

It's been several months since the first post on this subject. I glued up the test strips and lost interest. I'm back at it again. The test strips are PMQ style untapered two strip blanks about .130 inches in overall diameter. That should approximate the diameter of a 5wt tip at the midpoint.

I had several tests in mind for these strips, but most of them didn't make much sense after I gave it some more thought. As noted in an earlier post, I'm using Titebond III. PVA glues like TBIII are know for their tendency to creep under a load. They are not recommended for structural construction like a laminated beam. The beam would eventually bow under stress because of the elasticity of the glue. See the Titebond III post for more pros and cons.

I've read what seems like hundreds of comments about the TB products on the rod makers list and Clark's. Some say that the tendency to creep in structural applications makes TB rods more prone to take a set than no creep glues. Others that use the glue on a regular basis disagree. Not that they will not take a set. But that they are no more prone to taking a set than any other glue. The battle of the glues rages on the internet, but I've yet to see a rodmaking test given to support either position.

So, I figured I'd do a simple test. I have two sets of test blanks glued up with URAC, Resourcinol, Epon, Hide Glue, and TBIII. One set was heat treated at 392 degrees for 15 minutes. The other at 266 degrees for 18 minutes. I'm guessing that the heat treating regimen has more to do with set resistance than the glue...but I could be wrong about that. The glued up blanks have been in my drying closet for several months. They should be fully cured.

I set up a form to put about the same bow in all of the strips with the glue line turned vertical (see the photo). I didn't bother to remove the binding string. That shouldn't be necessary for this test. I'm going to leave them bowed for several days at room temperature. It shouldn't get any warmer than 80 degrees in my garage this time of year.

All the test blanks took a set after 24 hours with no noticeable change after 48 hours. So much for set proof glues. That never made any sense anyway. There's no doubt in my mind that creep resistant glues produces a stiffer rod - all things being equal. But none of them are set proof when abused.

However, bending the test blanks for a couple minutes produced significantly different results. Bending a rod for 24 hours is clearly abusive. But just a couple minutes is closer to normal fishing conditions. The URAC blanks did not take a set in the two minute test. All the other glues took a set, although the TBIII blanks took a more dramatic set than the creep resistant glues.

This was not a lab quality glue test, but it should be close enough for making fishing sticks. URAC is the clear winner when it comes to set resistance under normal conditions. All of the glues will take a set when abused. TBIII is more likely to take a set under normal conditions than the creep resistant glues.

I've been fishing TBII and TBIII rods for several years now on the Ozark tailwaters. I haven't had any trouble with sets except in really hot weather. I can't leave my TB rods in the truck on hot days. Other than that, I just go fishing and don't worry about the rods. I'll keep using TBIII until my experience on the water changes significantly or a creep resistant non-toxic glue appears on the market. I would definitely switch to URAC if it was non-toxic.

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