Primitive Archer

Main Discussion Area => Bows => Topic started by: Red Dwarf on February 19, 2009, 04:26:14 pm

Title: Thinning bamboo backing from rind side? Full draw added.
Post by: Red Dwarf on February 19, 2009, 04:26:14 pm: I am trying to build a bamboo backed hickory flatbow for my son. Tha bamboo I have comes form a smaller diameter palm and so is thicker than I would have liked for the width required. I am at the tillering stage and am finding that the hickory is getting thinner than I would like in relation to the thickness of the bamboo; can I thin the bamboo by removing material from the back of the bow? (The rind side).

Red Dwarf
Title: Re: Thinning bamboo backing from rind side?
Post by: Hillbilly on February 19, 2009, 04:30:24 pm: Don't think I'd do that. If you trap it pretty heavy it might help.
Title: Re: Thinning bamboo backing from rind side?
Post by: Jesse on February 19, 2009, 04:31:14 pm: not unless you plan to put another backing over that.
Title: Re: Thinning bamboo backing from rind side?
Post by: dragonman on February 19, 2009, 05:55:40 pm: I would'nt do that if I where you, I tried that on my first bamboo backing, and it was a disaster
Title: Re: Thinning bamboo backing from rind side?
Post by: El Destructo on February 19, 2009, 08:10:56 pm: Red Dwarf....is the Boo already glued down?? If not use a Belt Sander and reduce it....if it is glued down....I would heat it off....and reduces it....then re-glue it....taking anything from the Rind Side...will be devastating....JMO
Title: Re: Thinning bamboo backing from rind side?
Post by: Red Dwarf on February 19, 2009, 11:30:28 pm: How about cane fly rods? The bamboo is reduced to straight sections and they seem to hold together just fine.
Just a thought..

Red Dwarf
Title: Re: Thinning bamboo backing from rind side?
Post by: PatM on February 19, 2009, 11:44:54 pm: Yes but rod makers stagger the nodes and iron them flat so the weak spots are very minimal and spaced far apart. There is nowhere near the node violation you would have by completely severing a node across a high stress area.
Title: Re: Thinning bamboo backing from rind side?
Post by: Pat B on February 20, 2009, 12:52:54 am: What glue did you use? If TBIII you can heat it to 150 deg(F) and the glue will release.
Title: Re: Thinning bamboo backing from rind side?
Post by: Red Dwarf on February 20, 2009, 11:05:48 am: I used Urac 185!
Thinning the bamboo further from the "inside" face would have resulted in the bambo being narrower than the belly slat, but, with the benefit of hindsight, that would have been better than what I have now.

Red Dwarf
Title: Re: Thinning bamboo backing from rind side?
Post by: Jesse on February 20, 2009, 11:43:47 am: Do you have any pics? I would just finish the bow and see how it comes out. If its only thinner than the boo out at the tips you can leave those a little stiff. You can trap the boo and thin the limbs a little also.
Title: Re: Thinning bamboo backing from rind side?
Post by: adb on February 20, 2009, 01:07:50 pm: When I'm building a bamboo backed bow, I don't really touch the outside of the bamboo anymore. You have to thin it enough, before you glue it up as a backing. I used to sand down the nodes quite a bit, but I usually don't even touch them anymore. Now, i just lightly scrap or sand off the milky outer rind, so the bamboo will take a stain or finish. If you get to aggressive, you will violate the power fibers of the bamboo, and this usually results in failure.
Title: Re: Thinning bamboo backing from rind side? Tiller picture added.
Post by: Red Dwarf on February 23, 2009, 04:02:46 pm: Well, I figured I had nothing to lose so I went ahead and thinned the bamboo by around 1/16 keeping the same thickness difference at the nodes. Here is a picture pulling 20# at 18 1/2". This one is for my son and I am hoping for 22# @ 22".
To me it looks like I could do with a little more bend at the fades/inner 3rd; what do you guys think?
The profile is 1 1/4" at the fades with a straight taper to 1/2" nocks. 56" ntn.
Red Dwarf

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Title: Re: Thinning bamboo backing from rind side? Tiller picture added.
Post by: Pat B on February 23, 2009, 04:06:09 pm: you could come in on the right limb a bit more near the handle but other than that is looks quite good.
Title: Re: Thinning bamboo backing from rind side? Tiller picture added.
Post by: Red Dwarf on February 27, 2009, 07:38:00 pm: No one is more surprised that I am to see that she made it to full draw.
Here is a picture of my son pulling 22# @ 22". I am very pleased with the way it shoots and am hoping that it stays in one piece.
I think I should have thinned the bamboo a little more on the lower limb (on the left) as it has taken more set than the upper, where the boo was already a little thinner to start with.
If it still looks good after 100 or so shots I will go ahead and try my 1st staining job.

Red Dwarf

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Title: Re: Thinning bamboo backing from rind side? Full draw added.
Post by: Easternarcher on February 28, 2009, 09:00:39 am: I'm pleased to see that it is holding for you as well!
I don't know if the lower limb is taking set, it looks like the tiller is off that's all. The upper limb is stiffer than the lower in those pics.
Nice looking bow tho.....congratz.
Title: Re: Thinning bamboo backing from rind side? Full draw added.
Post by: dragonman on February 28, 2009, 10:41:29 am: I'm pleased your bow worked out, just shows, nothing is certain in the world of bow making!!! best to go with the feelings, its good to get advice but anything is possible,( even though I'm suprised the boo did'nt break)
Title: Re: Thinning bamboo backing from rind side? Full draw added.
Post by: Justin Snyder on February 28, 2009, 11:35:53 am: I'm glad to see that it worked out. I'm not surprised to see that it did. I didn't realize you were shooting for such a low weight. I don't worry about grain much at all on those low weights. If that bow was #40 it might be different all together. Nice looking bow for your son, congratulations. Justin
Title: Re: Thinning bamboo backing from rind side? Full draw added.
Post by: Rich Saffold on February 28, 2009, 12:43:06 pm: Red Dragon, LIke you were thinking, the bamboo doesn't always have to be as wide as the belly piece as long as the crown of the bamboo runs down the center of the bow. If this is a small gap you can smooth this transition between the two pieces and having the belly be wider than the bamboo backing isn't a problem..

Ipe D or Elb style bellies match up well with these small diameter bamboos, and 3/4" to an inch width will easily make bows from 60 to 100#'s.