Author Topic: Advice needed  (Read 3079 times)

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Offline Calamitus

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Advice needed
« on: April 26, 2013, 09:43:44 am »
I am trying to make a bow along the lines of this one: http://www.primitivearcher.com/smf/index.php/topic,19714.0.html
I tried using bamboo flooring instead of maple backing and broke 2 because the nodes are too weak on the bamboo. I am trying again with a single piece of hickory backing on red oak, a bit longer than Ken's, 52" before adding the siyahs. It will be bending through the handle with a goal weight of 45-50 lbs. At the moment it is 1-1/2" wide and uniformly 5/8" thick. I have glued some reflex into it to counter the eventual set from tillering. My question is should I narrow the whole thing, taper the width from 1-1/4" at the handle to 1" at the place the siyahs start, or leave it parallel at 1-1/2" or 1-1/4" the whole length? Should I trap the back any?


blackhawk

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Re: Advice needed
« Reply #1 on: April 26, 2013, 12:25:34 pm »
Narrow a handle section to at least 1 1/4" with smooth transitions and leave the width in the limbs where your at at an 1 1/2" to start with parallel and go from there..and trap the hickory back quite heavily,n ya might wanna thin that hickory down to an 1/8"
« Last Edit: April 26, 2013, 12:29:57 pm by blackhawk »

Offline Joec123able

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Re: Advice needed
« Reply #2 on: April 26, 2013, 01:18:02 pm »
This seems like a high stress design and glueing in the reflex is just going to put even more stress on the limbs you should have slightly deflexed the limbs to reduce the stress on the limbs
I like osage

Offline Calamitus

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Re: Advice needed
« Reply #3 on: April 26, 2013, 04:09:36 pm »
Narrow a handle section to at least 1 1/4" with smooth transitions and leave the width in the limbs where your at at an 1 1/2" to start with parallel and go from there..and trap the hickory back quite heavily,n ya might wanna thin that hickory down to an 1/8"

Any ideas how to thin it evenly without a planer or bench sander? It's hard to get a 1/8" board with a band saw.

This seems like a high stress design and glueing in the reflex is just going to put even more stress on the limbs you should have slightly deflexed the limbs to reduce the stress on the limbs

You are correct, I completely forgot about the increased stress. I was thinking only of the finished shape and target weight. I might have to try this design one more time, I have plenty of hickory left from that wheelbarrow handle.

Offline adb

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Re: Advice needed
« Reply #4 on: April 26, 2013, 04:14:43 pm »
You can get a 1/8" backing strip from a bandsaw... but it'll be rough and unglueable. You're right, it'll be a lot of work without a thickness sander or belt sander.

Offline lostarrow

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Re: Advice needed
« Reply #5 on: April 27, 2013, 02:10:02 am »
Glue your backing on first ,then trim it down on the bandsaw . Clean up your toolmarks and you're set. Planing a thick board is easier than a thin one.Get the face that will be glued ,dressed ,then run it along a fence on your saw. Do you use a fence? If you can't get a good 1/8 strip with your bandsaw, it needs a tune up,blade change,different blade,fence adj. or all of the above. With things working well, you can cut veneers with a standard 14" band saw. 
 

Offline Calamitus

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Re: Advice needed
« Reply #6 on: April 30, 2013, 09:33:50 am »
I'm going to try to thin the backing, it already popped a splinter just bending it over my knee a bit, but it was shallow and can be sanded through. The backing is quartersawn btw. If it blows up no big deal. I will have one of those asian style bows eventually! In the meantime working on a kids red oak bow.

Offline lostarrow

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Re: Advice needed
« Reply #7 on: April 30, 2013, 11:20:24 am »
Probably not a good sign.

Offline adb

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Re: Advice needed
« Reply #8 on: April 30, 2013, 12:59:20 pm »
I'm going to try to thin the backing, it already popped a splinter just bending it over my knee a bit, but it was shallow and can be sanded through. The backing is quartersawn btw. If it blows up no big deal. I will have one of those asian style bows eventually! In the meantime working on a kids red oak bow.

Did you round off the corners first, before you started bending it. Where did it lift a splinter... at a run off?

Offline Calamitus

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Re: Advice needed
« Reply #9 on: April 30, 2013, 07:15:15 pm »
I'm going to try to thin the backing, it already popped a splinter just bending it over my knee a bit, but it was shallow and can be sanded through. The backing is quartersawn btw. If it blows up no big deal. I will have one of those asian style bows eventually! In the meantime working on a kids red oak bow.

Did you round off the corners first, before you started bending it. Where did it lift a splinter... at a run off?

Yes I rounded the corners, it may have been in the area where the grain got a bit wavy but didn't run off.