Friday, 6 February 2015

Some Results

The bow feels pretty good and shooting off a shelf is easy.
I measured a force draw curve for the bow and it's now 35# at 27".
I find it's easiest to measure it by pulling to a know poundage and measuring the distance rather than pulling a fixed distance and measuring the poundage. It's done one reading at a time, letting the bow down after each reading.
(I went from 10# to 35# in 5# steps.)

I took a couple of my old arrows with missing points, cut them down a whisker and stuck on new ones giving a 27" arrow with a 70gn point.
Now to be fair, I'm not fully 'au fait' with the detailed conventions of flight shooting... where on the shelf and the arrow do you measure the draw to? Anyhow lets just press on... here's the force draw curve, which led me to ponder...
If the bow has zero poundage at zero draw (e.g zero draw at brace), and 35# at 27", assuming a linear force draw curve (and they generally are fairly linear) then surely there is only one possible line that joins those two points? I s'pose the bow with a load of stored energy at brace no longer has a straight line FD curve but has it bulging upwards in the early stages.
Now this bow doesn't actually have much (if any) reflex. That is to say the limbs have some reflex curve but, unstrung, the tips are not reflexed past the grip. In fact it's effectively got 1.5" of set.
So what if I thin the limbs to weaken them and remove some of the stress, I could then presumably get some reflex back into them and end up back at 35# at 27"... but would that be good, bad or what? Whaaa my brain hurts.... maybe I can actually try it once I've had some fun from the bow.

Right... shooting it through the chrono. I tied a nocking point to the string to give a consistent arrow position, but it was a tad tight on the nock. My first two shots were a bit tentative too.
151 fps
152,4 fps   Not bad, but not spectacular
next shot I made sure I used nearly the full length of the arrow shelf with a slash loose. That is pulling the hand back rather than letting the fingers creep forward as they are extended which can easily loose over 1" of draw.
172.2fps WOW!
I noticed the extra thread I'd whipped round the nocking point had come off and the arrow was now sitting loose on the string. Two more shots to check it wasn't a miss read of the chrono.
It was noticeable that the readings were vastly more reproducible with a near centre shot bow rather than a longbow where the arrow is snaking as it leaves the bow.
I'm very pleased with that. Hopefully on Sunday I'll try it for distance, and also try out my laser range finder.

I refurbished a flight arrow with a missing point, it's 252.3gn and I got 196.1 fps out of it.
I should point out the arrow is 28" long, but I don't think I took it to a full 28... mind I'm tempted to just to get past the 200 fps mark.

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