Will this bamboo work

How to make a Bow, a String or a Set of Arrows. Making equipment & tools for use in Traditional Archery and Bowhunting.

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magtrev
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Will this bamboo work

#1 Post by magtrev » Sun Nov 09, 2014 7:34 pm

Hi guys,

I've previously mentioned i planned on making my own bamboo backed bow. i've got started (will post some pics in another post) but just wanted to ask those in the know. Attached is a picture of the bamboo i have to use. it's 1.8m long so very little extra length to play with. you can see the node spacing at one end is a fair bit smaller than the other.
so..... from experience, do you think this is workable as it is or will cause big problems?

I did consider having 2 strip and splicing them in the middle so the node pattern is the same on both sides but i'm not sure that would work with the bamboo pole (the curve etc) so then i thought i could then sand the spliced section flat and add an overlay to hide/strengthen the splice. Again, not sure how this would work with the curve of the bamboo and the overlay. would sanding the splice flat and overlaying weaken the rest of the bamboo by compromising the outer layer?



Thanks everyone.
Attachments
uneven node spacing
uneven node spacing
Bamboo node spacing.jpg (108.29 KiB) Viewed 2046 times
I've never used training wheels and i'm not sure how they work. I love the stick and string, I just wish I was better at it!

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greybeard
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Re: Will this bamboo work

#2 Post by greybeard » Mon Nov 10, 2014 8:41 am

You can do it either way but splicing the bamboo over the handle will give you a more balanced looking bow.

When using a full length strip of bamboo designate the close node spacing end as the bottom limb as the closer the node spacing the stiffer the bamboo.

If you splice, cut your bamboo from the wide node spacing end. Keep the node as far away as possible from the tip. I would recommend a three to four inch ‘Z’ splice but if you find it easier a ‘V’ splice should suffice.
04 Diagram For Z Splice.JPG
04 Diagram For Z Splice.JPG (21.9 KiB) Viewed 2020 times
If you are concerned about the strength of the splice keep the handle a little bit rigid.

As a matter of interest what is the widest spacing of the nodes?

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

magtrev
Posts: 11
Joined: Mon Sep 29, 2014 12:32 pm
Location: Brisbane

Re: Will this bamboo work

#3 Post by magtrev » Mon Nov 10, 2014 9:13 am

Thanks for the info Daryl.

i'll have think about how i proceed. I need to get a new blade for my band saw first as i managed to break it the other day (GRRRRRRRRRRR!)

I'm not sure on the node spacing off the top of my head, i'll measure up tonight and let you know.
I've never used training wheels and i'm not sure how they work. I love the stick and string, I just wish I was better at it!

magtrev
Posts: 11
Joined: Mon Sep 29, 2014 12:32 pm
Location: Brisbane

Re: Will this bamboo work

#4 Post by magtrev » Mon Nov 10, 2014 8:08 pm

If you're still curious Daryl, i've finally had a chance to measure up.

the first complete section on the left measures 150(ish)mm from node to node
The last complete section on the right is 265mm node to node.

I'm thinking that while i would like to do a splice, i'm not sure my skill is currently at a level to do a nice job of it BUT if using the section whole will make tillering a real problem I should at least have a go at it.
If i do, I'm guessing i will have to get 2 strips of bamboo sanded down so the underside is flat before i make the cuts and do the glueing?

Thanks again for any advice
I've never used training wheels and i'm not sure how they work. I love the stick and string, I just wish I was better at it!

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greybeard
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Re: Will this bamboo work

#5 Post by greybeard » Tue Nov 11, 2014 12:39 pm

The pole you have was probably the bottom section of a much longer pole.

From previous experience the 150mm [6inch] spacing is too close and I would suggest using the other end of the pole.

Allow extra length in the half length laminations to make up for what is lost in the splice.

Most epoxy glues have gap filling properties so if your splice is not precise it is of no great consequence, but strive for the best fit you can get. A ‘V” splice four inches long should suffice.

The following is part of a document that I wrote some years back and although it refers to multi core laminated bows the basic principal applies when backing a bow stave with bamboo.

When preparing core laminations for a long bow I have an overall width about 1 ¼” to 1 ½” by the required length. Make a template slightly oversize of the desired limb plan and this will make the marking out of components more accurate and will save you a lot of measuring. Draw the plan of the limb shape on a lamination and include a centre line down the length and one across at the half way mark. This lamination is placed face down on the form when gluing up. Using two core laminations allows you to end for end the laminations to help minimise weak spots although I prefer three laminations.

Split or saw your bamboo pole into suitable widths and start flattening the inner surface with whatever suitable tools you have available i.e. belt sander, electric planer, spoke shave etc. Mark the limb plan [slightly oversize] on the bamboo and cut to shape. Draw marks across the bamboo at six inch intervals and these will be used as checkpoints to control the thickness and taper. Continue flattening the inner surface until the edges of the bamboo is about 1/ 16” thick.

For ease of construction I use a rigid form to glue up the core laminations, riser and belly bamboo as multiple laminations need a platform to keep them in shape when glued and clamped. The rigid form will need about five inches of reflex built into it as most of this reflex will pull out during the tillering and shooting in process. Unlike a glass laminated bow that will hold its tiller from the first arrow the bamboo bow may take a hundred or more arrows before its tiller settles.
With a three lamination core I prefer to run two laminations on the back and one on the belly of the riser.


You will need to work out a limb width to suit the crown of your bamboo. A high crown could result in insufficient timber left in the stave which could be overpowered by the bamboo.

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

magtrev
Posts: 11
Joined: Mon Sep 29, 2014 12:32 pm
Location: Brisbane

Re: Will this bamboo work

#6 Post by magtrev » Tue Nov 11, 2014 12:49 pm

Thanks again Daryl.

looks like i'll be trying my first splice then :biggrin:
I've never used training wheels and i'm not sure how they work. I love the stick and string, I just wish I was better at it!

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