Reducing bow poundage

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Feral
Posts: 46
Joined: Mon Sep 30, 2013 12:57 pm

Reducing bow poundage

#1 Post by Feral » Sun Oct 11, 2015 4:23 pm

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This is my 60inch 70lb Osage bow. My original plan was to build a circa 50lb bow. It is 60 inches because that was the straightest bit I got off the tree. But I misread the scale and finished it up.
However it developed a chrysal about half way up the upper limb which I strapped with superglue soaked nylon thread and covered with epoxy. I have been happily shooting it but it is too heavy for my bad arm. I have never been happy with the finish and I wonder if it would too hard to strip all the layers off and tiller it down a bit. As you can see there are a couple of longitudinal cracks near the handle and riser, but I assume that they don't move much, and also a few pins from spikes.
I love this bow, it is rough but my first Osage one and it took a lot to get there. I think I rushed the finish and now that I am calmer I would like to tweek it down and hopefully reduce any disasters later.
Cheers
Osage bow 1.jpg
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This is the epoxy covered repair. It has cracked off but still shoots great
This is the epoxy covered repair. It has cracked off but still shoots great
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yeoman
Posts: 1563
Joined: Mon Mar 08, 2004 1:32 pm
Location: Canberra

Re: Reducing bow poundage

#2 Post by yeoman » Mon Oct 12, 2015 11:02 am

There would be no issue in stripping the finish off the belly and tillering back to 50 lb. This will also have the effect of reducing the bending stress, which may mean the chrysals will not return (though no promises).

Just treat it once again like a bow that's not yet finished: draw to intended draw weight, observe the tiller, remove wood where it needs to come off, and reassess. Rinse and repeat until your desired draw weight is at your desired draw length.

Just as an aside...the nylon wrapping over the chrysal does nothing but hide it. A chrysal is a little bit of wood that's been pinched up because of the compressive forces parallel to the longitudinal axis of the bow. Wrapping cord tightly around the transverse axis does not reduce the compression, and does not support the belly. But out of sight, out of mind, right?
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Hamish
Posts: 309
Joined: Wed Oct 18, 2006 7:42 pm
Location: Sydney

Re: Reducing bow poundage

#3 Post by Hamish » Tue Oct 13, 2015 11:05 am

You are better off getting some new materials and starting a fresh. 60" 70lbs in that design is pretty stressed if its for a 28" draw. Add to that the uncompensated for cluster of knots, in the working area of the limb, its unlikely you will remove the chrysal even if you compensate for the knots an only remove material from every where else, in the reduction to 50lbs.

The bow even if it didn't have a chrysal will still have the string follow of the 70lb bow after the weight reduction.
Sure its possible to do it, but you'll be better served making one 50lbs or so from the start, compensate for any knots, by leaving more wood and or plugging any loose ones.

Feral
Posts: 46
Joined: Mon Sep 30, 2013 12:57 pm

Re: Reducing bow poundage

#4 Post by Feral » Fri Oct 16, 2015 8:17 pm

I've stripped the back off and reduced the bow to about 55 lb. The chrysal isn't a chrysal but a split . So I am still looking at a fix.
Wait and see.

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yeoman
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Location: Canberra

Re: Reducing bow poundage

#5 Post by yeoman » Sat Oct 17, 2015 5:48 am

Share a picture or three? If it is a longitudinal split, the fix might be to swill some glue into the crack(s) and clamp them tightly shut.
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