Tuesday, 31 October 2017

Roughing Out Some Staves

Had a guy come over on Saturday with a log he'd cut about 4 years ago, I'd made him a bow previously (Ridgeback) and he wanted me to make another. From the pics he'd sent the log didn't look too promising, but once I'd trimmed off the end an had a shufti, I could see one clean face with a bow in it. There is still one iffy knot, but most of that will disappear (see pic)

After he'd gone I ran it through bandsaw and there were some troublesome areas where one growth ring had been damaged/rotted, maybe by fire, lightning, rubbing against another branch or just bad weather. Fortunately it was fairly near the centre and by the time I'd got the save roughed down the bad ring had been cut away.

The other two staves are Austrian Yew cut from a rough half log that was bought at a bargain price by one of my friends in expectation of one good stave and maybe a skinny second. Again there are some splits and shakes, but careful laying out has produced two warbow staves, they are a tad on the short side at 73 and 74" (bearing in mind I like to have a couple of inches spare on a stave), but the bloke isn't very tall and has a 30" draw so they should be ok. It's hard to tell which is actually the best stave so I'll probably work 'em down together and see which is 100-110# and which is good for a bit more.

The paler English Yew stave is prob' going to be about 60# but I've got to discus what's required.
It's good to have a few staves ready to work on, and I've actually got a spliced Yew one as well. I tend to think of this time of year as bow making season, as there's now't much going on in the garden. I'll be thinking of cutting a couple of Hazel staves too with my mate JT, who's going to try his hand at bow making early next year.... I'm sure some beer drinking will also be involved.

I went over to Cloth of Gold as a guest of Mick the Blacksmith on Sunday, had a great shoot around in good company, we weren't scoring and did 18 targets each from two different pegs, so I shot a good few arrows. My shooting seemed back to normal and I made a few decent long shots too. Probably my last outing of the year as it's getting colder, although I might manage the ILAA at Windsor if the weather's good.

Friday, 20 October 2017

Oh Bugger!

It's times like this you wish you hadn't left a tap dripping all yesterday morning!
 I had to spend a good deal of time mopping up the garage floor, fortunately most of the boxes on the floor are plastic rather than cardboard these days. A dustpan and brush got up a good deal of the water, and I have plenty of sawdust to help soak it up.

Next irritation was my bandsaw blade breaking, now this was a 1/4" 4tpi blade with extra set which my mate Stuart had bought as a thanks for the bandsaw usage and stuff. It's a blade configuration I hadn't used and it turned out to be very good, cutting nice and straight. I'd imagined that a wide blade would cut straighter but I found the narrower blade better, also good for following curves. (my other blades are 1/2").
The blade is still pretty new and V sharp so I was reluctant to bin it.

There are plenty of Youtube videos on brazing broken blades. This blade had broken on the weld, but I don't think it was a manufacturing defect, more likely due to me cutting odd shape 1/4 logs freehand.
I had an off-cut of Dexion which made a handy guide to clamp the blade to. I just sawed two slots and bent a section out of the way, cleaned up the sharp corners with a file and the jig was ready... only problem was finding the flux and brazing rod. I really must make another draw for welding and brazing supplies.
The ends of the blade were chamfered on the belt sander, coated with flux and carefully clamped up on the jig.
I think the brazing rod I have is quite a high melting point as it didn't want top flow at first, but once the joint was really glowing bright yellow it suddenly flowed. A bit of careful filing and then I tried it on the bandsaw, it clicked a bit as it went through the guides so I put a small grind wheel in my electric drill and lightly ran it over the sides and back of the join. It now runs lovely and smooth, good job all round, taught me a new trick and I have the jig for next time.
Here's a pic of my G-clamp nest, a couple of old shelf brackets screwed to the wall and it keeps 'em all handy and tidy.

Thursday, 19 October 2017

Sawing Some Yew

I've had two 1/4 logs on the garage floor since about January and I trimmed them down a bit the other week. I've taken them down further into 2 big slabs which are wide enough for warbows and some useful off-cuts.
The wood isn't as good as I'd hoped, there is a lot of blueish discolouration in the sapwood and the sap/heart boundary is all over the place even by my standards, I think it's just too undulating, so what I'll probably do is cut it into heartwood staves, billets and slats for use in bamboo backed Yew bows or crossbow prods or experimental work like flight bows.
I won't be too hasty as it requires some thought to make best use of the wood. I dare say plenty of usable yew gets discarded because it's not perfect... and maybe this is what some people mean when they say English Yew is no good, of course the point is I'm sure you could find similar gnarly wood from anywhere, one is simply limited by choice...
What's the best Yew? The bit that you've actually got!

One pic shows how the heart sap boundary doesn't follow the rings. This Yew was fairly large diameter (about 16") rather than the ideal pipe straight 5 or 6" diameter we'd all love to find.

Wednesday, 18 October 2017

Now't Much

I took the tri-lam and re-tillered Twister to the club on Sunday. I shot about a dozen from the tri-lam, not worrying about getting a 28" draw, just shooting as I normally wood (about 27") at the big practice boss from about 25 yards or so at a scrap of paper in the centre. It seemed nice and smooth giving a reasonably consistent group, a tad left of the paper but a nice vertical line of arrows. I was just banging 'em out quick to give the bow an extra few arrows.
I then picked up Twister which had disappointed me a few weeks earlier when it had felt stiff and unyielding. That's what had led me to re-tiller it.
I was a good 25 yards or so from the target. I pushed out my left hand drew, and... thud 1/2" left of the paper... Drew and thud, 1/2" right of the paper... Drew and clatter as arrow number 3 hit arrow number 2 .
Yup, that's how Twister should shoot. My confidence flooded back and I joined the guys to shoot about 7 of the 3D targets with a good degree of success.
I took my leave feeling much happier, I didn't want to over do it as I've been getting a lot of neck stiffness when I shoot, and it's a wise man who knows when to quit.

I've not started another bow yet, just waiting for the urge to hit me, I've been giving the lathe a good clean and adjust and reading some pap sci-fi on my kindle. Those damn Zarlacks keep jumping out of hyperspace into the summer house while I'm in there reading with Emily the cat on my lap. Must transfer power from my old car battery to boost the shielding...

Thursday, 12 October 2017

Re-Tillering "Twister"

Now re-working Twister is at first glance verging on the unthinkable, as it's been my fave' bow for years (made in 2011). On a good day I knew I could punch out my left hand at a target and I'd hit it.
Recently though I'd been toying with taking off a little draw weight, also my draw length has dropped a tad and is nearer 27" than 28".
Having been shooting in the tri-lam longbow at a good 28" draw, I realised that twister by comparison felt "stacky", that's to say I'd get to about 26" draw and it then felt stiff and unyielding instead of lively and supple.
Over the Years Twister has taken a little set mid limb (more on the lower) but is still good by my test of putting it belly down on the floor (unstrung) and seeing how many fingers you can get between grip and floor. One or less is good, which is how Twister is. Two is ok, 3 is poor. It was a superb bow, but maybe the two of us aren't quite what we were, so I thought I'd ease off the outer limbs a tad and maybe that would make it feel smoother, take some stress off the mid limbs and ease off the draw weight.
To get myself in shape too I've rasped a bit off my belly ... just kidding... I've re-instated the dozen push ups night and morning.
Unfortunately I didn't take a pic before doing any work, but this first pic shows the tiller after I'd eased off the tips a tad and lost a few pounds. It's at 40# at 28" where it probably started out and nearer 45#.
You can see the tips are stiff and it's bending quite hard mid limb almost in the style of a Mollegabet bow with stiff levers for the outer third. The two circles (or ellipses as they may not be exact circles) are quite tight radius and I'd like to see the stress spread more along the whole limb. It must have been worse than this before I eased off the outer limbs.

I've heat treated the mid section of each limb with the limbs strapped down and a slip of wood about 4mm thick under the back where the set was. That effectively pulls it into the merest hint of reflex so that when the heat treating is done and the strapping off, the limb is about straight.
It's now about 40# @ about 24" which gives me some room to re-tiller whilst keeping a decent draw weight. I think what I need is about 40# at 27" and I'd like the bow to have it's original speed and feel.
I've done a little more work now and actually shot it. Here's an after heat treating both pulled to just over 27"
The curve is looking much better and I've ended up pretty much where it was when first made about 45# @ nearly 28" , I've shot half a dozen arrows and it feels smoother and faster like it's old self.
The difference in curve is pretty subtle but if you look at the chalk marks on the wall behind the right limb you can see in the "after" picture the limb is nicely on the curved line whereas in the first pic the tip is pulled inside that line with more of the bend in the middle/inner limb.
I'll probably quit while I'm ahead now!
Maybe this last pic shows the difference better, I've done the 2 ellipses and this time you can see they are flatter and the tips conform to the curves better.
Finally another try to fit ellipses as well as I can, this one shows the right limb having a slightly tighter curve, which is fine as generally you want the lower limb a tad stiffer.
Right you can plays spot the difference now!

Friday, 6 October 2017

Spine Measurement

Well we all know about spine measurement... or do we?
I've made a quick and dirty spine tester, having noticed one rogue arrow, and using my digital verniers to measure spine is a right fiddle.

A while back on an archery forum on a post regarding how point weight effects spine I made a comment that infinite point weight would effectively give zero spine! e.g If you take a warbow to full draw, put the arrow point against a brick wall (which approximates to infinite weight) the arrow will just explode when you loose (e.g it will flex infinitely).
This was tongue in cheek, but was to illustrate a point and demonstrate a way of reasoning by extrapolating to extremes.
Well some bloke "corrected" me and said I meant infinite spine.
It became apparent that the target archers way of measuring spine to AMO standard is the opposite to the traditional wooden arrow way of measuring spine!
Now this is what is technically known as bloody stupid, however I'll let you decide the rights and wrongs.
The tradition way is to support the arrow at two points 28" apart. OR any other convenient distance, and this is important for shorter flight arrows. You hang a 2 lb weight on the middle of the arrow and measure the deflection in inches. You divide the distance between the two support points by the deflection in inches. (This automatically compensates for differing support distances... clever eh?)
E.G. If we have the supports 28" apart and we get 0.5" deflection that gives 28/0.5 which is 56
So the spine is 56, this number bears some rough relationship to the bow poundage for an average bow.
Note:- as deflection of the shaft increases the spine reduces, so 1" deflection would give 28/1 = 28 spine.
The spine figures are not linear, this shows on the uneven spacing of the scale. Also note, for convenience I've used 26" between the supports.

As far as I can tell the AMO method simply measures the deflection in thousandths of an inch with an 880gram (1.94 lbs) weight applied using a 29" shaft with supports 28" apart.
Has this annoyed you yet? They are randomly mixing metric and imperial and I have no idea what the 29" shaft length is about!
BUT the most worrying thing is they are just measuring deflection. Why does this matter?

If you plot  distance between supports divided by deflection (x) as a graph y=28/x you get a curve and as x gets bigger y gets smaller.
If you plot simple deflection y=x you get a straight line and as x gets bigger y gets bigger...
So the AMO spine runs the opposite way to the old method, bigger number is weaker rather than stiffer!

Now which is right?
Not for me to judge, but I'll just mention that  bending stiffness of a beam k=p/w Where k= bending stiffness.  p = force.  w = deflection

Oh, btw, my 2 lb weight is just a carefully calibrated bag of pebbles :-)

Wednesday, 4 October 2017

Trilam all Done

I've got it finished and over 60 arrows through it (I'll take that up to 100 before final waxing). I've just had it on the tiller and it's almost 50# which is odd, as it looked more like 46# the other day, this illustrates the difficulty of getting good data. The camera is mounted about level with the bow so is effectively looking down on the string at full draw giving a parallax error. Whereas if I sit down to pull the rope my eye is about level with string at full draw removing that error, so in reality it's a tad over 47# generally it's prob' sensible to give draw weights rounded down to the nearest 5# as a bow is likely to settle a bit rather than gain weight (unless it starts off not fully seasoned).
It's been interesting shooting the bow, the arrows seemed to wag their tails rather, but a little work around the arrow pass and inlaying the Abalone helped. Then I got suspicious that maybe there was one odd arrow, so I marked the one that flew high and right with an inconspicuous dot. Next five arrows, sure enough, one waggled off right, when I looked, yes it was the same arrow. Maybe that accounts for some of my poor shooting at the last field shoot as it was marked as a number 1 arrow.
I shall try the same test with my field bow and see how that throws 'em, I suspect the effect will be
slightly less marked as that bow is prob' a tad slower.
In terms of feel the tri-lam is lovely, it feels like it would draw further just as smoothly and I've been making sure to shoot it from a good full 28" draw which is extending me slightly. It's good to be shooting more as it seems to be helping the tennis elbow and shoulder niggle. I've been doing push ups night and morning, at least 10 and 15 or so if I'm feeling bouncy.
Couldn't resist adding the pic of the grip again as it is so gorgeous :)