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Blue Quill wrote:

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Tight glue lines are a sign of quality and require careful planing and strip finishing. However, the rod will be stronger if you finish the strip with as coarse a surface as possible while still providing a straight/tight/sharp glue line.

The trouble with the scraper is that it leaves the surface so smooth that it glints in the light, which is not an ideal gluing surface. Conversely, the sanded strips have tiny grooves from sanding which provide an excellent gluing surface.

I stopped scraping to final dimension a while back. After planing to dimension I give each strip a few light passes with 400 paper; light enough passes and rough enough paper to cut into the surface of the cane yet leave the dimensions intact.

I still use a 212 scraper for troublesome nodes, and hand-held scraper blades for removing the enamel and flattening the crown, but my gluing surfaces are always sanded.

I realise many makers may not agree with this, but this is how and why I do it and it works for me

Chuck

Chuck,

That all depends on what kind of adhesive you are using to glue the strips together. A roughened surface, with little grooves may work well with a water based glue, like Titebond (or any of it's variants), but will actually weaken the bond on many chemically cured adhesives like epoxies. The epoxies end up having a weaker bond by the excess of the adhesive in joint. Epoxy itself has a terrible lack of strength, both in shear and in tension. It gets is biggest boost of strength in the tightest matrix. The least amount of epoxy to effect the bond is the correct amount of epoxy in the joint. There are many articles out there on preparing a surface to be bonded with epoxies. Here's an article written by Ralph O'Quinn, the fella that supplies the U-40 brand of rod making epoxies: Surface Preparation. Note: this applies mainly to adhesives that use a chemical reaction to cure, not air hardening or air curing adhesives.

Mark

Chuck,

There are "degrees" of smoothness. Matte, which gives the "water break" surface, is much different than something sanded with a sanding medium larger than 600 grit.

It all depends on what you are adhering, and what adhesive you are using to adhere, as to the strength of the matrix. Epoxy is quite different from other adhesives that use air curing or hardening. Epoxy gives a much better bond the thinner the joint is. That's not to say the joint should be starved of epoxy, but any epoxy more than a simply wetted surface weakens the joint. If you don't believe me, please have a read: Bond Line Thickness. Epoxies, and other adhesives that chemically cure, rely on a chemical bond to adhere the objects in the matrix. Air curing or hardening adhesives depend on a mechanical bond to adhere objects in their matrix. The chemical-cure adhesives tend to shrink very little as they cure, while the air-cure adhesives tend to shrink much more in the joint. Since the chemical-cue adhesives shrink very little, any excess adhesive in the joint, whether do to roughing gouges, or joint gap, will do nothing more than weaken the joint.

If epoxy was strong enough by itself, you see Corvettes running around with no fiberglass in them, or composite aircraft with molded flying surfaces having nothing other than the adhesive in them. There really is very little strength in just the adhesive alone. The bond requires the least amount of adhesive to form the matrix between the adhesive and the bonded surfaces. It doesn't matter whether you are talking about adhering one piece of graphite to another, or one piece of cane to another, or one piece of graphite to one piece of cane.

I use Epoxy on all my rods too. But if you are going to base your usage on a certain kind of adhesive, you really should understand the properties of that adhesive. I've been using epoxies (all different kinds - laminating, fill, joint bonding, metal filling, conductive and many others since the early 70's). Each has it's own use, each has it's own properties. But the common thing about epoxies, the thinner the application of the adhesive to the surface (to a point, as shown by the article above), the stronger the joint. The more epoxy left between the two surfaces in the joint, the weaker the joint will be.

I pointed out Ralph's article because he sells a lot of different kind of adhesives, polyurethane and epoxy included. His article talked about the best surfacing for an epoxy bond. The man knows of which he speaks, since he's been in the industry for a long time, and has worked with the kinds of adhesives we use for making fishing poles. A bonding surface is a bonding surface is a bonding surface. How you prepare that bonding surface goes a long way to the strength of the joint that is formed when the adhesive is applied, and the matrix is formed.

Mark

Chuck,

That's not what you said above. Your words, "However, the rod will be stronger if you finish the strip with as coarse a surface as possible while still providing a straight/tight/sharp glue line" do not agree with your latest reply. I was just pointing out that "coarse" and epoxy joints do not go well together.

Just curious. How did you measure the .0003" depth of the striations left by the 400 grit sandpaper? 400 grit particles can range in size from .0018" to .00043". Both of which are larger than what you say your depth of striations are.

Just as you, I've been working with many different types of epoxy for many, many years, from laminating epoxy, to filler epoxy, to coating epoxy, to layup epoxy and many other uses. When somebody puts out information that is incorrect, it needs to be countered with facts. All you've tossed out so far is anecdotal evidence that this is the way it should be. I've offered information from the manufacturers and research. If you choose not to believe what they are saying, that's entirely all right for whatever you want to do, however, for those who want to understand on how to get the most from their choice of adhesive, it just ain't so.

Mark