Wednesday, 2 August 2017

Bottle Job

I rasped the Yew belly on the crossbow prod down to about half its original thickness and glued on the fibreglass lamination. Gut feel and experience being used rather than extensive computer simulations and calculations!
The first limb went fine, but the second somehow contrived to be a dodgy glue up, not sure how as I'm pretty meticulous, anyhow the excess fibreglass at the tip got snagged on the bench and popped the glue line at the tip... hmm I was V irritated, but I got it all cleaned up and did it again. It seems ok this time, but is very stiff so I've taken about 4mm off the lower edge of each limb and I'm slowly working it towards full brace and being cocked.
Note I'm using the longest string of the 3 that have been made for the various versions of this prod, which is looped through the string adjuster.
 I'll add the string catchers too as there will be a lot of energy in this bow and I don't want to risk it going over center.
It's hard work to cock it, gotta be about 100# .The actual numbers are a bit irrelevant, but if it settles down to be a reliable prod I'll doubtless measure it on the tiller at some point. The pictures show low brace and cocked, I was hoping to see if the tiller looked even but it's hard to see without carefully lining up the camera, it's also tricky with a crossbow as it's possible to pull the string back off centre forcing it to be on the skew, similarly you can force it back dead straight and it will look true as the string won't slip sideways on the latch.
Dunno if that makes sense... on the tiller rig, the string is being pulled buy a long rope and hook, and the bow is supported so that it can rock, this lets you see how it settles under tension, it's not being forced one way or the other. In comparison, on the crossbow, the prod is tightly clamped and the string catches solidly onto the latch.
Just had it on the tiller, still hard to see how even it is, maybe a hint stiff on the right limb, but that looks contrary to the pic above, I took it to 90# and it wasn't full draw, so I reckon it is pretty much 100#
Anyhow I'm basically rather scared of getting to full brace and cocked without making sure everything is as good as possible. I'm even considering some linen binding at a few strategic points along the limb in case it shatters. What worries me is that now the belly is stronger than the back the failure mode could be an explosion of bamboo splinters which would be at eye level (it will be  a safety glasses job). With the previous configuration the likely failure mode would be a graceful collapse of the Yew belly with chrysals and a deterioration of performance.
I am getting a tad jaded as well as scared but do want to see it through, I'm pining to make a longbow or warbow, and there's decorating to do and we want to put some small windows in the summer house as it's a tad dark in there (good for a crafty cat nap tho' !)
Could also do with a holiday, but that will wait until the school holidays are over.
August already, and we've had blackberry and apple pie, the woman next door is leaving me her windfalls for cider making... the year is rolling by, seems like the Summer months all only have about 15 days.

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