Bow Build: Walnut Bamboo Longbow, Glue Up

glue pot
I use Smooth-On EA 40, a two-part epoxy, for bow body laminations. It’s easy to measure, mix and use. Cost: $35.50 (plus shipping) from 3Rivers Archery. Expensive? No. I’ve done at least 10 glue-ups and have enough for at least three or four more.

It’s glue-up time. Part 1 of this walnut-boo bow build is here.

First we look at a not-very-useful or beautiful picture of the bow form.walnut form

The form, in this case, is a 2×4, something shy of 8 feet long. It’s wrapped in plastic so that the bow doesn’t get glued to the form. That black strip is a spongy rubber used to cushion and/or seal garage door bottoms. That helps protect the bamboo from cracking during clamp-down. Although on this build, I went with the bamboo on top because I forgot to mask the bamboo rind before gluing. I decided it was too late to stop the glue and tape up. Figured if I set the boo on top of the walnut, the glue wouldn’t find its way onto the top of the bow, my experience suggesting that glue does not drip up. Right?

Well, guess what, glue apparently feels fine about dripping up and well as down. Smooth On must have some anti-gravity quality it keeps secret. I could find no mention of it on the cans.

walnut gluey
That’s what the glue looks like on walnut as seen through a camera.

bamboo gluey
And that’s bamboo glued. These are very thin films of glue. Figure 68 inches long, 1.5 inches wide. One tablespoon of Part A glue, one tablespoon of Part B hardener. So two tablespoons for 102 square inches, if I did the math right.

wrap full

Once the laminations are joined, the camera’s on its own. I’m in no mood, state, or mindset to snap photos. As usual, the camera failed to take the initiative itself and record the steps that led to this happy scene. So here’s what happened:

  • The glued laminations (walnut and bamboo planks) are wrapped in 2 mil plastic to keep the glue from sticking to non-bow items such as clamps.
  • C-clamps grip the tips.
  • Bicycle inner tubes wrap around the frame and bow wood. I stretch the inner tubes as tightly as I can. It’s like wrestling an anaconda.
  • Additional clamps hold down inner tube ends and contribute to compressing the laminations.

wrap close
Close-up of clamp/wrap rig.

Then the rig goes in the oven.Bow oven
See that little dot center right about an inch and half in (on my screen) in from the right edge of the photo? That’s a cheap meat specialized bow thermometer.

The glue-up stays in that oven for six hours. Three 150-watt incandescent bulbs (Remember those? Well forget them. Erase their gentle wonderfulness from your mind. Or else.) warm the box to 160 degrees. When time’s up, I pull the plug and let the box cool to ambient.

OK, that’s the plan. Here’s the variable reality: I’ve left the oven on for as many as 8 hours. I’ve cooked for 6 hours and pulled the plug though the temp never got much above 150 degrees. All the glue-ups have been successful in at least the sense that the glue cured and held.

The 6 hours and 160 degrees is mentioned by more than one source. So I use it as a rule of thumb. Smooth On EA 40 comes with no more instruction than mixing ratio and cure time (24 hours). That’s apparently cure time outside an oven. Thing is, the rule of thumb is working. It’s not something I want to veer from beyond the demands of necessity. So I shoot for 6 hours and peak temp of 160. I’ve left in longer. I’ve pulled the plug when max temp never crawled above 152 degrees. All the glues have been fine.

OK, now for the other glue-up: the handle. Normally I start from here:
handle uncut

Then glue another piece of wood to the top of the rise. I use Titebond III and when it’s cured, I start carving.

iboo close 2
This is an example of gluing additional wood to the handle. Rosewood on ipe. It’s all right. But I’d like a bit more highlight, especially with all that dark wood on bamboo. Still, not bad. Safe. Oooooooh … safe!

So this time, I did something different.handle cut

I cut down into the handle, thereby jeopardizing the entire bow and all the work I’ve put into it thus far. Crazy … or courageous? Won’t know till the whole thing’s operational or breaks. Suffice it to say this move made me really nervous. I paced a bit. I admit it.

Of course, I’m not going to leave it like that.3 handle piecesI’m going to glue two pieces of hardwood into that slot. The guy on the left is yellowheart. On the right, zebrawood.

handle yellowheartDrop the yellowheart in first.

handle assembly mockupThe zebra goes on top of the yellowheart.

I don’t know how this will end up, aesthetically or functionally. But I had the idea and decided to chase it. What’s one more broke or nasty-looking stick in the scheme of things?

First thing I do is lay down a thin film of Titebond III to all joining surfaces. In this case, bottom of yellowheart, top and sides of cut-out handle, which is walnut. When the glue gets tacky, I slobber on more glue, press the yellowheart in place and clamp it up.

yellowheart glue close

This time, I let the yellowheart glue-up cure overnight. End of shift. I decided not to press on and add the zebra till the next day. I see no reason you can’t glue it all up at once. Might make alignment of the pieces a wee bit trickier. But otherwise, what could go wrong? And no oven time for Titebond. And no wrapping in plastic. Titebond needs air.

zebra gluedLess dramatic glue ooze (glooze?) this time. I tidied it up before shooting (a photo). In case you’re wondering, I have three clamps on this guy. I want the glue lines to be razor thin. I doubt they will be. I sanded and filed and filed and sanded. When the pieces appeared to fit tight I quick started gluing before they changed their minds. Not exactly a master woodworker move.

That’s glue-up. In part three we explore the wonderful world of once again cutting into a perfectly good bow.

OK, a pretty good, apparently working, bow.

3 thoughts on “Bow Build: Walnut Bamboo Longbow, Glue Up

  1. Pingback: how to build a walnut bamboo longbow

    1. jlindner Post author

      I will add a part 3. Thanks for asking. The gist of it will be this: I really like this bow, despite a sort of embarrassing fail with the handle.

      Reply

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