Bamboo vs. Glass

K. Mogensen · December 01, 2019, 02:05:08 PM

Sorry if this is a dumb question, but I'm wondering about whether or not bamboo could be used in place of glass using standard 36" lams that one would use in a glass backed bow.

I know that generally you would use bamboo to back Ipe or Osage or more bamboo, but could a person get some ground lams like you would from Bingham's and then use those? I'm envisioning gluing up the lams and riser on a form to keep everything flat (hill style) and then gluing on the bamboo backing afterwards to avoid dealing with the nodes in the form. Same goes for the belly, running the bamboo up the fades of the riser (with heat treated bamboo).

Afterwards the bow would be profiled and tillered as you would with a glass bow, shaving material from the sides of the limbs. My thinking, is that by having lams that are pre-ground to a precise spec, much of the tillering would be avoided.

What would prevent this from working? I'm mostly just curious, I still haven't built anything other than in my head so I really know nothing.

Thanks.

Pat B · December 01, 2019, 02:53:19 PM

The tension strength of bamboo is in the fibers and the closer you get to the rind(outer most)the stronger the fibers are. By cutting the fibers to make a lam you are violating the fibers thus weakening the tension strength.

monterey · December 01, 2019, 03:04:28 PM

I think he's proposing to use a bamboo backing like Roy does on his trilams. Least that's the way I read it.

Mad Max · December 01, 2019, 03:05:22 PM

Quote from: Pat B on December 01, 2019, 02:53:19 PM
The tension strength of bamboo is in the fibers and the closer you get to the rind(outer most)the stronger the fibers are. By cutting the fibers to make a lam you are violating the fibers thus weakening the tension strength.

Read again Pat

K. Mogensen · December 01, 2019, 03:29:44 PM

Yes, like a trilam but using multiple core lams spliced the same way that you would do with a glass bow.

Thanks!

Pat B · December 01, 2019, 06:55:47 PM

Yeah, I guess I missed that part. The answer to your question is yes.

Mad Max · December 01, 2019, 07:14:40 PM

On a Reflex/Deflex tri lam the bamboo is tapered in thickness on the bottom of the bamboo leaving the top (Node part) alone.
It's going to be trial and error to figure out how thick everything is, and your width taper.
You should start with the bamboo on the back only.
My 2 cents

bucknut · December 01, 2019, 08:58:41 PM

Sounds like you are referring to something like a Miller or Shulz Split Bamboo bow. I also agree it will be lots of trial and error on lam stack thickness with the Bamboo back and belly.

K. Mogensen · December 01, 2019, 09:44:50 PM

Whadya know? That's exactly what I'm talking about.

So it looks like it can be done. Thanks guys. Wonder if there's any way to guesstimate a stack thickness that would at least be reasonable (within 20 lbs).

Pat B · December 01, 2019, 10:22:12 PM

James Parker(huntworthyproductions) has made many boo back and belly bows of many different configurations. He could probably get you in the ball park with a stack recipe.

Buemaker · December 02, 2019, 09:00:13 AM

I think Woodcarver made such a bow in the last bowswap.
I think he scorched the belly.

wood carver 2 · December 08, 2019, 12:46:10 PM

Sorry guys, I was away for a few days chasing critters.
Plane your bamboo till it's 1/8" in the middle and 1/16" at the tips. Same for the belly, if you're using bamboo there as well. If you do use bamboo for the belly, then use a torch to blacken it before you get it to the final thickness.
I use one lamination for the core. 1/4" thick in the middle and tapering to 1/8" at the tips. 1/4" is a good starting point. Depending on your choice of wood, it should get you to a decent weight. Because you're using all natural materials, it will usually be a bit of a guessing game, but with practice, you should be able to come close.
If you want a wood belly, Roy would know more than I do about thicknesses. He knows his tri-lams.

Dave.

Mad Max · December 08, 2019, 06:44:37 PM

"wood carver----If you do use bamboo for the belly, then use a torch to blacken it before you get it to the final thickness."

before you glue it on.

wood carver 2 · December 08, 2019, 09:28:05 PM

Definitely burn the belly before glue up!!!
The heat will cause the bamboo to cup backwards. Because of this, you can plane it thinner and with less of a radius. Don't wait too long after burning the bamboo before gluing up your bow or it will start to cup again as it absorbs moisture from the air.
One more thing. There will be some char on the bamboo. I very lightly sand it and wipe it down with a rag so I don't get black fingerprints on everything.
Dave.