Oh Crap

[DC]

I was taking a picture for my arrow pass post and noticed that the handle riser glue joint is opening up. I can feel it with my fingernail. I've only shot the bow a half dozen times. The wood has dried for 10-12 months. I used the same epoxy glue up that I normally use. We've had some cold dry weather and I've stood the bow behind the gas stove where it's not too hot, but warm, to dry the Tung oil. Do you think it was just the low RH that did this? Maybe Pacific Nine Bark takes a lot longer to dry?

[DC]

As for fixing it I was going to flood it with thin CA but got to wondering if I should wait for the RH to normalise first. Maybe it will close up a bit?
 It kind of helps my decision as to use a handle wrap or not

[bownarra]

It could well be a moisture content issue. A year isn't really long enough to stabilise. Before gluing up things like this I take an offcut from the middle of the woods thickness and test the m.c., I like 8%. If the m.c. is a little high a microwave is useful for drying.
I suspect another part of the problem is that the riser section extends too far into where the bow is working.

[PEARL DRUMS]

I would rather handle build up blocks have nothing to do with the fades on a self bow, as Mr. Arra mentioned above. I want them to be part of the bow itself and the handle block to be nothing but a way to deepen the grip itself.

[DC]

From what I remember reading on here, the general consensus was that 3/4" was thick enough for the bow. This one is a full 1" so I figured it was thick enough. I have done thinner with no problems but there is always exceptions. I know I've been anxious to make a Nine bark bow so I probably did push the envelope a bit. It did take a bit of set so that's making me think humidity. It's sure nice wood to work.













 

[Eric Krewson]

On any glued on handle it is best to put down a couple of 1/8" shims between the bow and handle piece.

What kind of epoxy do you use?, I had bad luck with the two ton stuff with two syringe type applicators side by side. Every handle I glued on with that type of glue popped off. Of course this was in my early years and my bow making skills were a far cry from what they are today. I use unibond or smooth-on now, I used to use urac. When I started using urac I never had another glue failure.

I have a friend that does nothing but trilams, he swears by TB 3 for all his glue-ups.

Shims;

[willie]

A year isn't really long enough to stabilise.

this and grain orientation. If you read the literature from the major boat building epoxy suppliers, you will find recommendations how to take grain orientation into consideration. no adhesive will withstand excessive shrinkage differences between the two parts being glued.

you can find data where a particular species will shrink at one percentage tangentially and another radially. the T/R ratio varies between species, as some woods have very high tangential shrinkage. you will probably not find pacific nine bark on the list, but you can assume high values if it tends to check easily when drying in the round. you can minimize differences by choosing grain orientation of the pieces you use for the other handle parts.

ht   tp://www.woodbin.com/ref/wood-shrinkage-table/       (link intentionally broken at http)

[DC]

What kind of epoxy do you use?,

West Systems 105/205
This is the first time I have glued the splice and riser together at the same time. They were a very nice fit but I'm wondering now if I may have clamped it too tight. I've read that's it hard to do but who knows.

[Hamish]

DC how hard does your West systems epoxy dry? Is it a little rubbery? The best bow making epoxies dry like Urac(not an epoxy), glass hard. No flex in the glue joint even if the wood bends, you won't get a lift.

[DC]

DC how hard does your West systems epoxy dry? Is it a little rubbery? The best bow making epoxies dry like Urac(not an epoxy), glass hard. No flex in the glue joint even if the wood bends, you won't get a lift.

It dries hard. It's good epoxy.

[PatM]

Undoubtedly a little extra radial shrinkage exceeded the bond strength.

[willie]

I've read that's it hard to do but who knows

one thing that I thinks helps with the system three I use to prevent starved joints, ( I use a thinner product than most with no fillers) is to get the pieces good and warm, almost hot, like 150 F. before mixing up the pot. with the freshly mixed epoxy, I "prime" the hot pieces to get good as good a penetrationas possible and maybe prime again as the pieces cool. I set the pot itself and the remaining glue aside someplace cool. It helps if you pour, (not scrape) the mixing cup contents into a pan of some sort so that it can cool faster in your cooler location. the aversion I have to scraping the mixing cup is that the resin along the sides and bottom may not always be fully mixed at the proper ratios. same for the mixing stick.

when the pieces cool and the prime coat becomes tacky, maybe an hour interval depending, I get the resin in the pan (which hopefully has thickened some), and do the clamp up.

For general information:
the rubbery thing Hamish mentioned is often a mix with improper ratios between part A and the hardener. it's easy to do with small quantities. To Prevent this, it helps to mix by weight with a gram scale. (most products will give a spec for this, as it is not the same as by volume)

[Woodely]

What I have done on some bows is glue a dowel in or countersink a screw,  that's what I did when I noticed the takedown riser starting to separated.  I worked so far.

[DC]

I've thought of using dowels before but it goes against my grain to cut across the grain in any way. Like drilling a hole. I guess as long as you don't drill though the back it should be fine.
Anyway I CA'd it and put it out in the shop where the humidity is better. It seems fine now but I'm watching it. I did find another piece of Nine Bark with the date on it and it says June so I was pushing the envelope a lot harder than I thought. Like most things that go wrong for me eventually they get written off to stupidity on my part.

[vinemaplebows]

On any glued on handle it is best to put down a couple of 1/8" shims between the bow and handle piece.

What kind of epoxy do you use?, I had bad luck with the two ton stuff with two syringe type applicators side by side. Every handle I glued on with that type of glue popped off. Of course this was in my early years and my bow making skills were a far cry from what they are today. I use unibond or smooth-on now, I used to use urac. When I started using urac I never had another glue failure.

I have a friend that does nothing but trilams, he swears by TB 3 for all his glue-ups.

Shims;

I agree with Eric on the 1/8 inch lams, the 2-ton epoxy is only good for rigid applications, I use it on non-bending handle splices, never a problem myself, you MUST use exact amounts, and a 24 hr cure at room temps. This is for devcon epoxy, the only store epoxy I personally trust.