I’ve had the power tools fired up for a few days. This is turning into an annual event between Christmas and New Years. Splitting, sanding and milling a year’s supply of bamboo. That’s not a lot of work in my case. I’ve never made more than 4 rods in one year. Split enough for 6 this year plus a batch of strips for a glue test. The glue thing needs to be done before gluing up any more rods.
I’ve been using Titebond II and III up to this point with good results. But glue is one of those subjects that seems to stoke the campfire when there’s more than one rod maker present. Before making any more rods, I want to test some of those campfire assertions in the shop.
I plan to test several types of glue for relative stiffness, set resistance, and creep. By no means will the tests be lab quality. I’m not looking for 100% accuracy. Just something more reliable than some of the campfire comments I’ve seen on the internet.
The testing will include Resorcinol, URAC, EPON, TBII, TBIII, GG, and TB white glue. The test blanks will be level taper PMQ style with the enamel side turned in and a finished diameter of about .125 inches. There will be two sets of test blanks representing two different heat treating regimens. I did the heat treating today. One set was treated at 392*F until there was a “just-detectable” color change. About 14 to 16 minutes in my oven. Those strips lost about 6% of their weight. The other set was treated at 266*F for 18 minutes and lost about 3%. I’m assuming that heat treatment will have a significant effect on stiffness and set resistance of the test blanks. So I’ll test blanks from the upper and lower limits of heat treating regimens as defined by Wolfram Schott in “Bamboo in the Laboratory”.
The tests will be done with fairly short blank sections with no nodes. Stiffness will be tested by adding weight and measuring the deflection. Not sure about this yet, but I think I’ll measure the deflection of the blank with the glue line vertical then horizontal and compare the two. As noted earlier, these will be PMQ (2 strip quad) blanks. I hope that will make it easier to isolate the effect of the glue. In theory, the glue should have very little effect on deflection with the glue line turned vertical and a significant effect with a horizontal glue line. The difference in the two would represent the relative stiffness of the glue. That would also help mitigate the effect of different MOEs on the deflection of the test blanks. See Wolfram Schott’s work noted above for a discussion of MOE variations around the circumference of a culm.
Testing set resistance should be as simple as bending the test blanks for a while to see if they take a set. Creep should be fairly easy to test with a significant amount of weight in the middle of a section noting misalignment of the strips at the ends after a few hours.
Like I said earlier, this isn't supposed to be a lab quality project. But if any of these glues are unfit for rod making, these tests should confirm that beyond a shadow of a doubt.