Wednesday, 22 February 2017

Emily's Return and Musing on Tillering.

Emily the cat came back last night after 3 nights missing, she's moving slow with a bit of a limp but seems ok, and very pleased to be home. We'll take her to the vet for a check up.

In the interests of fairness, putting the alternative view and generally trying to learn, here is some discussion of methods.
A guy (Will) on one of the sites has suggested that you can make Yew bows to virtually final dimensions including horn nocks before getting it on the tiller for final tweaking. I'd agree that this is possible with laminates and may be possible with a clean stave. He suggests that one advantage is that the wood doesn't get overstressed by excessive force when unevenly tillered and it doesn't even need a long string.
The interesting thing is that when you study the detail of what he says it is virtually the same as what I say and do, other than working on the tips and outers which come round later!
Here's his quote:-

"The long string is a bit of a controversial one as well - many bowyers who make superb heavy bows don't use long strings, especially not for a 100lb bow.  Something that light can be floor / vice tillered to begin with, then braced as soon as possible.  

If you watch Ian Sturgess' recent video you can see the process clearly.  It's a case of ensuring perfect tapers and watching the mass, getting the bow virtually finished before it even sees the tillering tree.  This minimises set, and drastically reduces the strain put on a bow early on, while many other bow makers drag it down on a long string to see where the problems are - by which point those problems have already damaged the bow.

However, all of that said, with unknown woods and unfamiliar draw weights a long string does keep things safe, at the risk of having a lower performing bow.  I think for what you're doing (at this stage just trying to make the thing work!) a long string is wise, but perhaps only to brace height.  Provided the bow is fairly even at brace height, you should be able to see almost all the problems with the tiller from the full brace shape."

Anyhow, it's given me thought to question my techniques and my position that "you can't make a bow by numbers" I think the key reasons for my approach are to cope with uneven staves, problems of bows trying to bend sideways and trying to hit an exact draw weight.
I think any technique done well souldn't overstress the wood, but I'd suggest that unless you have perfect timber, caution and proceeding slowly is safest.

He raises some interesting questions about how the medieval bowyers would have worked suggesting they couldn't take too long on the tiller.
This has been raised before and the counterargument is that they also couldn't spend ages measuring dimension and mass.
My thought was maybe they had a set of gauges to judge the key dimensions, but no such tools have been found. More likely we probably just underestimate their skill and they were good enough to get it all very close by eye and maybe flexing it by shoving it between two beams and heaving on it one limb at a time.
We simply don't know.
Anyhow, I could make a bow close to final dimension and go from there if I wanted, inded I have done so before. I think the key point is I try to explain the best way to do it to achieve success (especially for the less experienced) which is generally considered to be a well tillered bow at the target draw weight and length. I don't suppose the medieval bowyer of warbows was aiming at a specific poundage other than bllody heavy or over!

Monday, 20 February 2017

Missing Cat Syndrome

Emily cat has wandered off, it's over 48 hours now... we've even had a little ginger cat who is her friend looking for her in our garden. We've posted on Facebook and put leaflets through the doors in the neighbourhood. The woman next door came round she has cats too and said she'd previously seen Emily in their garden and going over in a dirction which we'd not been aware of. She's an adveterous soul and very much a free spirit. maybe she's got a whiff of spring and feels the need to raom free (even tho' she's been spayed). We wouldn't mind her roaming as long as she's ok... hopefully she'll come back in her own time.

Anyhow, what do I do when I need distracting from cat worries?
Yup, make a bow! I have another pair of glued up rather wonky billets, so I'm trying to make a heavy weight short draw flight longbow for the ILAA rove at the weekend. I'm aiming for about 70# at 24" I hope to maybe give the warbow boys a fright in the flight shhot at the end of the rove!
I've also done a double belly patch on JT's 120# warbow, it had a long but relatively shallow chrysal/pinch across the belly that was in danger of getting worse. Warbows have a short enough life and take a lot of strain, so some preventative maintenance may hopefully prevent a blow up.
The chrysal raises the question of should one leave thickened areas around knots etc... the danger is you simply create a weak point between the thick points and get a chrysal or pinch there. I think the real answer is to be very subtle and sympathetic to the wood, great raised bulges are in my opinion a nonsense, unless done as "character" features. On the 120# bow I could feel a very slight dip where the crysal is, because a tiny bit extra had been left for a knot on one side just beyond the crysal, and the other side of it, a little extra left to accomodate an undulation. As is often the case, hindsight is 20/20 and one could easilly say "Ah, it was bound to chrysal there"... but conversely, if it hadn't chrysalled, it would have been a brave man to call it a "weak point" as it was very subtle.
Been making some brass flight arrow points too.

In case anyone is wondering I did two thinner patches rather than one deep thick one, this is because a thinner patch will flex and conform to the rasped out scoop giving a good fit.

Thursday, 16 February 2017

Buddleia Explodes!

Having started with the left limb stiff, I over compensated and it was then a tad weak, but I was easing off the right limb and teasing it back.
I'd got it to about 40# at 23" when it went bang, failing a big knobbly knot, hardly surprising. Just a bit of fun trying out a new wood.
The wood is OK, it's the regular big knobbly knots that are problematic as they are rather pithy and weak on the belly and are a weak point on the back.
Pics sow the break, note the filled knot on the belly, it was a large porous area of bark like material.
The tiller wasn't too bad, the grip could have flexed more and the right limb was still a tad stiff.
Here's the video of it going bang :)
https://www.youtube.com/watch?v=dfrpNkQME04




Wednesday, 15 February 2017

Buddleia

Otherwise known as the Butterfly Bush, We pruned one of these back in the autumn of 2014 and there was a nice straight section which I saved to try as a bow wood.
I couldn't get any opinion on it other than "try it and see" so here goes. I suspect it may be a bit brittle as the dead wood on the shrub is V brittle, but so far it seems fairly stiff and quite hard, with some attractive colour.
I'll show the first try on the tiller as it is V bad and shows the left limb very stiff, the second shot is after I've done a good bit of work on that left limb and faded it back into the grip more (it will flex in the grip when finished). The stave is only 51" long, with a nice waggle in one end,
The bark, which is similar to that of Elder has been left on and is making ominous cracking sounds.
Looks reasonable now, gotta get the grip moving moreand the right outer limb.
I make edit together a video showing how the tiller progresses... we'll see.
I'll probably aim for 40# at 24-25" if it doesn't explode first.

Monday, 13 February 2017

Tarting up Mr Wonky

I thought I'd finish up the Wonky Warbow with an arrow plate, one reason being to cover a slightly narrow bit at the end of the splice. The billets weren't necessarilly going to end up as a warbow, but once I'd made the decision to go for 100# I left the stave a wide as possible, you'll see the narrowing at the end of the splice on one of the other pics (the one with the funny little face!).
Had been hoping it would get shot yesterday, but was overtaken by events, hopefully it will get an outing at the weekend if the flood plain is still dry enough. On a plus note I just heard from JT who shot one of my other bows at the shoot and got 301 yards for the flight shot, winning that part of the shoot. I think we're still learning about flight arrows, it will be interesting to see what Mr Wonky can do with a flight arrow, we know it's not all about poundage.

 Out of interest, the glue area of the Z splice is about  3 x 4.5" times 1.5 inches deep. That comes out at 20.25 square inches of glue area!

Wednesday, 8 February 2017

Reflexed Tips and the Magic Brick

I had someone ask why I used a hot air gun and oil to reflex the tips of the Wonky Warbow rather than steam.
Here are some pics showing how I did it and a list of pros and cons.
Pros:-
1. Dry heat is quicker.
2. You can see what is happening while you are applying the heat.
3. The heat can be taken up to about 200C giving some tempering as well as plasticising the wood. Being hotter it penetrates quicker.
4. You don't have to worry about getting from the steam onto a jig quickly.
5. Gentle even pressure can be applied and the wood allowed to relax into the bend at it's own pace by using the "magic brick".
6. Getting the wood hotter seems to set in the bend and have less bounce back than with steam.
Cons:-
1, The wood can get over heated and scorched.
2, Heat can leak round to the back and effect the delicate sapwood.
3. You can't leave it and have to hold the hot air gun. Whereas you can leave it steaming for half an hour or longer with no problem.

I've used both, I just went for the hot air gun this time (with sunflower oil brushed onto it) so I could get both ends done in the evening and then leave it overnight.

Note the side cheeks used to keep the heat on the belly, the back and sides were also protected with a few layers of masking tape.
With the brick pulling down on the bow, I could see it starting to pull slowly down after less than about 5 minutes of heat!

Reasons for reflexing! (A response to the explain more and the comment)
In this case it is to compensate for the deflex in the bow and to bring the tips back in line with the grip. The more technical aspects of the deflex/reflex design found in modern bows is basically down to improving the force/draw curve of the bow and making maximum use of the materials.
The maths and physics is beyond me, but I have good ways to visualize it and can maybe explain it.
There are several factors coming into play.
Let's consider a simple longbow, if we reflex the tips 2" this will make it require more force to pull the tips back to brace it, this will add early draw weight and give a faster bow... but we may overstrain the wood if we try and pull it back as far as we did before. So what if we deflex the middle of the bow by 2" we are back to where we started but has it made any difference? Well it turns out it has! The angle that the string pulls back on the tips has changed throughout the draw and this makes a difference.... why?
Well imagine a beam sticking out of a wall with a length of string dangling from it. If you want to bend the beam you'd pull straight down at right angles, if instead you angle the string back towards the wall (or away from it) you can't exert the same bending force even though you are pulling just as hard. Take it to the limit and pull the string inline with the beam, you are now exerting no bending force at all! You can pull as hard as you like but you are effectively just trying to stretch the beam not bend it.
That's what happens with a short bow at a long draw, the tips are starting to pull back parallel to the arrow and it becomes harder to pull than would be expected, this is often called "stacking".
Taken to extremes, reflex or recurve can uncoil as the bow is draw effectively lengthening the limbs as the bow is drawn and giving more leverage. This effect is utilized by the cams in a compound and by the levers Asiatic style composite bows which tend to be short, the characteristics of horn and sinew also accounts for their extreme shape.


Tuesday, 7 February 2017

Wonky Warbow Video


I've had it back to 32" draw at 100#.
The tips have been lightly reflexed using a hot air gun.
Here's the youtube video:-
the bow has a fiar bit of lateral waggle too, you'll see I've done the horn nocks, just got to make a decent string now.