Beep Beep Beep Tiller!!!!!!!

[Bearded bowyer]

Just thought I would pop my 105 lb bamboo/yew laminate warbow back on the tiller to see if it had lost any power.
Wound it upto 32" still 105lbs....great!

AAAAAAAAAAh

bottom hook of my butchers scales got caught on the bottom of my tiller.....

10 seconds......cant get it loose.....15 seconds.......panic......20 seconds.....30 seconds.....a whole lifetime of panic passed before I managed to free it up and......

Tiny quarter chryshal mid shaft!!!!!!!

my beautiful perfect bow is no longer beautiful and perfect

Gutted and very cross with myself for letting it happen in the first place 

Lesson learnt....don't leave a warbow at 32" draw for longer than is absolutely necessary...definatly not more than 30 seconds!!!!!

And I nearly took a finger off at the weeked stripping hazel bark.......car isn't working properly.....

I think I may go back to bed for the rest of the week....with several beers

[WillS]

Here's a tip Matt - don't EVER take a bow to 32" on a tiller.

Even if that's the intended draw length.  Most warbow makers don't do it, unless they're photographing it for a customer or something.  If a bow is meant to be 120# at 32", you take it up to 28", work out the projected draw weight at 32" and leave it at 28" on the tiller.  If it makes it to 28" and the tiller is spot on, it'll make it to 32". 

High performance, heavy warbows should be shot the last few inches as it keeps the performance at a peak and you don't risk what's happened here

Learned that from a certain Mr. Stratton - love him or hate him, the guy can make heavy bows.

[Del the cat]

Commiserations...
I think we've all had those days...
Mrs Cat has got me decorating ... grrrr
Del

[Bearded bowyer]

Ta Del
thanks for the advice.
How do you calculate the 32" draw weight from the 28, I have noticed on my lighter warbows that it is generally about 20lbs more, but is there a more scientific way?

Decorating?!?
Maybe you should get a dog to keep Mrs cat in order 

[WillS]

20lbs sounds about right.  It doesn't have to be exact, because unless you're selling the bow (which is where you would take it up to 32" and snap a piccy!) the exact poundage doesn't matter too much I don't think? 

It's always easy to forget (For me, anyway!) that warbows are riiiiight on the edge of sanity in terms of how much a piece of wood can really take.  32" is asking a heck of a lot for a great hunk of timber to reach, so any length of time at that draw is asking for trouble.  Make life easy for yourself and your bows will thank you by lasting longer!

[adb]

I never pull heavy bows to full draw on the tiller tree either. Generally, most heavy bows move about 3-5# per inch. Most of mine are closer to 5#/in. If I want a full 32" draw, I would only ever pull it t 30" and, as Will mentioned, shoot it in the last few inches. If your tiller is good at 30", it'll be fine at 32". I also learned this the hard way. I pulled a bow full draw (140#@32") on the tiller to take some pics, and it exploded. Tiller was fine. These heavy bows just don't like being left at full draw for more than an instant. I call the tiller tree 'the merciless extractor of truth'... it's harsh... there is no give, no compression of joints, etc.

[toomanyknots]

Even if that's the intended draw length.  Most warbow makers don't do it, unless they're photographing it for a customer or something.  If a bow is meant to be 120# at 32", you take it up to 28", work out the projected draw weight at 32" and leave it at 28" on the tiller.  If it makes it to 28" and the tiller is spot on, it'll make it to 32". 

I pull my 32" draw bows, whether they are 50 lbs or 130 lbs, usually to 33" on the tiller. I guess I am more merciless than others. (Thats about as heavy as I make though, if I was making heavier, I don't know if I would) If they fail than I will make another. I sent someone a bow one time that was suppose to be 100lbs, but I miscalculated how the weight would stack ( I measured at 28", but made the bow like an inch longer than I usually do), and it only measured 93#, which he wasn't happy about at all, as the first thing he did is measure the draw weight.  On top of my lack of faith in myself to calculate draw weight, I think a bow can loose 5 lbs sometimes just from being pulled those extra 4 inches, so I always make sure to pull and measure at 32", after working the bow in significantly. I wouldn't trust myself and my puny draw to shoot in a bow properly at 32" either.

EDIT: And I got a pulley setup with a block and tackle that I pull by hand, so it is not static or locked or anything. I hate those ones that you crank with a winch, where the bow is stuck, they scare me! If I ever make bows that pull 750 lbs at 38 inches, I think I will just triple up or so on my block and tackles,  .

[WillS]

Interesting to hear different approaches!  I think if I was working with a laminate, something that I could glue up again to the same dimensions if it broke I'd probably go right out to 32" as well, just for the "well now I KNOW it's safe" factor, but working with rare, pristine yew staves makes you a bit more aware of the pain when they go boom...

[Del the cat]

I calculate as follows.
Say it's 88# @ 28"
28"draw is really 28 minus the brace height. ( A force draw curve pretty much goes to zero at brace).
So if it's a 6" brace the real draw is 22".
Then that gives 88# at 22" which is 4# per inch.
To get from 28 to 32 is an extra 4" and will therefore add 4x4 pounds which is 16# giving 104# @32"
Note:- If you don't subtract the brace hight you'd get 3.14# per inch, giving 100.6# @32"
Del

[toomanyknots]

But what about potential stack towards fulldraw? And what about the opposite with reflexed bows? As well as length seems to make a huge difference.

[Del the cat]

But what about potential stack towards fulldraw? And what about the opposite with reflexed bows? As well as length seems to make a huge difference.

I'm talking about sensibly designed ELBs which are surprisingly linear, from my experience.
Although I have had the misfortune to try to draw a horrid Italian Yew warbow with a belly that had a load of untreated knots so when it got to about 2/3 draw they all pinched up and it stacked solid. Kicked like a mule.
Anyhow it's just a way of estimating, it doesn't matter how much sophisticated maths, computer analysis or 3D modelling you apply... none of it will effect the actual reality!...
Maybe the simple rule of thumb add 20# is close enough for jazz?
Del

[Bearded bowyer]

Lots to think about 

other than this occasion and one other ash, end grain on, tri-laminate bow, I haven't had a problem taking them to 32" for a second just long enough to check the draw weight then winding them back down again. I am mostly a laminate bowyer. Not sure I would do it with a single piece bow, but like toomanyknotts I don't want anyone coming back unhappy.
I think I will make some drastic changes to my tiller so it can't get stuck!
BUT I will be much more careful when my hazel staves are ready next year!

I've got a some target archers wanting light warbows at the moment....can't wait to see them try to use them

[Bearded bowyer]

oh by the way..
I'm going to continue to use the bow as a 28" target bow. I will keep a close eye on the chryshal and let you all know how she gets on.

Thanks everyone
Matt

[toomanyknots]

But what about potential stack towards fulldraw? And what about the opposite with reflexed bows? As well as length seems to make a huge difference.

I'm talking about sensibly designed ELBs which are surprisingly linear, from my experience.
Although I have had the misfortune to try to draw a horrid Italian Yew warbow with a belly that had a load of untreated knots so when it got to about 2/3 draw they all pinched up and it stacked solid. Kicked like a mule.
Anyhow it's just a way of estimating, it doesn't matter how much sophisticated maths, computer analysis or 3D modelling you apply... none of it will effect the actual reality!...
Maybe the simple rule of thumb add 20# is close enough for jazz?
Del

Okee dokey, makes sense.  Thats crazy about knots in a bow causing it to stack!

Lots to think about 

other than this occasion and one other ash, end grain on, tri-laminate bow, I haven't had a problem taking them to 32" for a second just long enough to check the draw weight then winding them back down again.

That's kinda what I do, I just don't use a winch.

oh by the way..
I'm going to continue to use the bow as a 28" target bow. I will keep a close eye on the chryshal and let you all know how she gets on.

Thanks everyone
Matt

In my experience, I've been lucky enough to get two different kinds of chrsyals. (depending on the wood sometimes) I either get lots of faint barely visible chrysals, usually in an area where the tiller is working more than anywhere else. I get these sometimes in mulberry, and have had them in a higher stressed linen backed osage bow. And the other kind will be just one or two, that go very deep. I had one single chrysal in a yellowheart bellied bow, it wasn't even bending (to my eye) anymore in that spot than anywhere else. I tried to do a patch and the chrysal went all the way to the core.

[Del the cat]

@ Toomanyknots
You could see the pinches running out across the belly from each knot.
The knots were sound but the ring of black manky stuff round each knot wasn't solid and hadn't been filled or soaked in superglue.
The effect was like sawing slots across the belly every 12" or so going half way through the bow, so that they closed up at 2/3 draw.
It had tons of set and felt like a 50# bow until it got to about 26" .
It was a bow which had been returned to the bowyer and then sold on as a training bow... it's wasn't sold as perfect. But it's a great illustration of how Italian Yew isn't magic or all knot free perfect staves. Also a good illustration of how important it is to treat the manky stuff around knots.
Where a side branch grows over and forms a knot, the wood of that branch may be sound, but the bark and cambium becomes the black ring of worthless mush.
Del