Saturday, 11 July 2015

Distance Results for the last two bows.

Last night I marked all my flight arrows with their weight in grains and approx draw length. First thing this morning I made up "Del's Gravitational Trajectory Indicator" from some old perspex sheet, to allow the launch angle (45 degrees) of arrows to be checked (by the spectator not the archer himself).
It's just a rough guide, as I'd been put off in the past by people suggesting I was shooting too high.
I believe the optimum angle is a degree or two less than 45, but that's hardly accurately achievable without a shooting machine.

Me and my mate JT spent an hour or so testing out some bows.
I was testing out the 52@29" spliced Yew billet bow and the 80# @30" Yew.
JT warmed up on a few big bows and then tried the 130# Yew bow I made him some time back.
He's now completely mastered it and was shooting it with aplomb.

The launch angle indicator soon showed we were both pretty much at the right angle, although JT didn't use my exquisitely manufactured pendulum facility, he just lined it up with the hedge row... spoil sport!

We tried a variety of arrows with the bows.

First up the 52# @ 29" Billet Bow.
My standard field arrow  390gn                               177 yards
29" Flight arrow              307gn (my nicest arrow) 208 yards

Then the 80# @30" Yew
My standard field arrow 390gn                                 196yards
30" Flight arrow             475gn                                220yards
30" Flight arrow             404gn                                232yards
EWBS* standard arrow                                             160yards

(*English War Bow Society)
Out of interest I just looked up the latest EWBS flight records to try and find something comparable.
The closest I could find was this:-
Standard Arrow. Mary Rose Bow (which is pretty much what the 80# Yew bow is)
Christine Carnie 86#@32" 155yds (bowyer Pim)
The nearest thing I could find for a flight arrow was:-
Christine Carnie  80# @32" 184 yards with an Italian Yew bow by Pim

Now comparing flight records is fraught with problems... We had a following breeze and it was a fine day. Maybe Chrissie Carnie hasn't got a full 32" draw... I don't know.
Ah, I've found the Junior records (2013)  which are with an 85# bow and are a bit longer 85# giving 170 yards with a standard arrow and 84# giving 234 for flight.

I'm not claiming anything other than the bow performs decently.

Now the interesting thing with the above results is that the flight arrows are both heavier than my standard field arrow! Some of this is due to them being an inch or so longer and also I used plastic nocks. The implication is that if I barrelled the shaft and used a nice faired in nock and a lighter small diameter point I'd have got substantially further.
Dropping from 475 to 404 grains gained 12 yards, although it may have just been a better loose. We could drop down to maybe 300grains minimum.
Inspecting the Yew bow showed the arrow plate was doing its job as all the scuff marks were dead centre on it.

JT tried the 130# Yew and got 260 yards with a 623 gn flight arrow of mine.
He could doubtless go a bit lighter (and smaller diameter with smaller fletchings) but we were being cautious.
There is some discussion about the optimum grains per pound (gpp) of draw weight for an arrow. It's down to trial and error and it depends on the characteristics of the bow.
5gpp is probably a reasonable start point. 3gpp is probably getting rather light. That would give a range of 650-390 grains, so the 623 is pretty reasonable. The diameter, spine an fletchings are V important.
This post shows some test results I got for velocity and energy using a crossbow pistol.

Ah, yes, I inspected the belly of the 130# Yew bow and there were a couple of small pinches (compression fractures) emanating from small knots, nothing to worry about, but something to keep ones eye on. The back of the bow is the vulnerable area, and any cracks or splinters there need immediate attention.

Bottom pic shows some more shooting in... I'm going to have to spread 'em about a bit more for fear of smashing the nocks off 'em! I'm probably not getting a full 30" draw and I probably won't get the usual full 100 arrows through it. 30 or 40 will have to suffice.

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