Knocked out a quick longbow today.

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yeoman
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Knocked out a quick longbow today.

#1 Post by yeoman » Sat Jan 11, 2014 8:40 pm

I wanted to test a couple of hypotheses in bowyery. To be properly scientific, I should have made two bows. However the variables were sufficiently independent of each other that testing them both on one stave wouldn't actually be a problem.

The bow is spotted gum, backed with bamboo. No reflex, just laid out straight. It's about 70" ntn, 34 mm wide at the centre.

I won't go into the hypotheses for the moment, but I will say one of them related to wood selection, and the other related to a possible efficiency that could be realised in the early tillering stages.

As for the first hypothesis, well it seems I was right as here we have a full-drawn bow. It's a tad stiff in the tips, but other than that it's alright for a hack job. 43.5# @ 28", shown here at 26":

Image

As for the other hypothesis, usually it takes me about 5 hours to go from taking the bow out of the form to full draw. Today I started work on it out of the glue-up just to make a start. About an hour later it was at full draw. So it seems my second hypothesis was proven too.

It just needs a sand with 400 grit, wax, new string, and an arrow pass marked. If I figure all that will take about an hour, then by the end I will have about four hours of work in this bow, maximum.

It doesn't have to take ages.
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Re: Knocked out a quick longbow today.

#2 Post by bigbob » Sun Jan 12, 2014 8:19 am

terrific work Yeoman. Be interesting to see your hypotheses' if you do expand on them.
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Re: Knocked out a quick longbow today.

#3 Post by GrahameA » Sun Jan 12, 2014 8:41 am

Morning Dave.
yeoman wrote:If I figure all that will take about an hour, then by the end I will have about four hours of work in this bow, maximum.

It doesn't have to take ages.
Yes, if you are willing to accept a decrease in efficiency/effectiveness of the bow and it not looking so 'pretty' they can be made quick and I would suggest that is what most people the first time around want.

Well done.
Last edited by GrahameA on Sun Jan 12, 2014 11:17 am, edited 2 times in total.
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Re: Knocked out a quick longbow today.

#4 Post by Stickbow Hunter » Sun Jan 12, 2014 9:18 am

That is quick for making a bow alright. The top limb looks a little stiffer in the outer limb than the bottom one but it appears to be coming back further than the bottom when lining it up with the brick work. Of course that could just be the angle of the camera or my eyes. :mrgreen:

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Re: Knocked out a quick longbow today.

#5 Post by Afro » Sun Jan 12, 2014 11:32 am

Wow :surprised:
Cheers :)

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Re: Knocked out a quick longbow today.

#6 Post by yeoman » Sun Jan 12, 2014 12:10 pm

I think your assessment of the tiller is about right Jeff. I've not yet decided if I'll rectify it or leave it be as an example.

Grahame, this was an interesting one. Once I got the tiller to 22", I swapped the fine side of the Japanese rasp to a fine file, so by the time the tiller was finished, there was precious little the sanding did to improve the look of it. It was more a tactile improvement in finish.

As for efficiency of the actual bow, I think there would be little difference between a bow that took four hours and 12 hours to make if the same attention to detail is paid. But for a beginner, I suppose tillering so quickly maybe would lend itself to errors and reductions in performance.

Okay, so one of my hypotheses was about wood selection. And this may seem to be a no-brainer to many, but it was an epiphany to me recently. The purpose of a bamboo backing is in part to be an unviolated layer of fibres on the back of the bow. Anything below this layer, in terms of grain, matters little if any.

So for this bow I picked a stave with horribly violated grain, that would never make a selfbow. The bamboo did its job (of course) and the bow made it to full draw. I honestly don't know why this didn't occur to me years ago. It means if you find a stack of timber of suitable species, you don't have to be fussy about grain if you're going to bamboo-back it.

I'm keeping the other part of my experiment under my hat for a bit, as too many techniques for decreasing bow making time for beginners may lead to more ruined staves than shooting bows. I'll be sharing the secret with students of my courses though, of course. In that instance I'll actually be there to observe and prevent any heinous mistakes.
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Re: Knocked out a quick longbow today.

#7 Post by Gringa Bows » Sun Jan 12, 2014 5:37 pm

Good stuff :biggrin:

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Re: Knocked out a quick longbow today.

#8 Post by Sabinus » Sun Jan 12, 2014 5:57 pm

Nice one!

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Re: Knocked out a quick longbow today.

#9 Post by Dennis La Varenne » Sun Jan 12, 2014 7:34 pm

Dave,

I have had some ideas about the old rule about violated growth rings on the backs of bows too and I have been a bit suspicious of it for some time now. Currently, inter alia, I am working on a Yew ELB which has had the sapwood rounded on the back a la the Mary Rose bows (see pic below).
Cross-section of MR bow showing crowned sapwood layer.jpg
Cross-section of MR bow showing crowned sapwood layer.jpg (202.3 KiB) Viewed 3800 times
You cannot have a single growth ring followed on the back of a Yew bow when the back is cambered like that in the pic. So, I have done the same and nothing is happening to the back of my bow thus far.

I do remember in TBB Vol 2 about Paul Comstock making a sapless Yew bow with its back completely violated without issue and this started me thinking that we may be paying too much attention to something which is not so much of an issue as we may have first believed.

As we know, the MR bows were massive. My ELB is not. Also, the mathematics involved suggest that the stresses applied to the back and belly on a heavy bow and a light bow made proportionately to each other are the same. My bow is a fair bit shorter by about 12 inches, narrower and less thick than any MR bow having a handle girth of only 3.5 inches or 9cm as opposed to 5 to 6 inches for a MR bow, but the back camber on mine is much higher than that in the pic above and like it, there is no sidewall. Theoretically, the back should be an issue, but so far, it is not.

My second 'epiphany' like yours was when a mate in Gippsland in Victoria started making flatbows like Comstock's basic bow from Eastern Red Ironbark. He shaped them using an electric plane to make a flat board from the quartered stave. It never occurred to him to follow a growth ring such as they are with this wood. There were absolutely no issues with bows made this way. I have made similar and ELBs from Eastern Red Ironbark with the same result.

Of course, there may be other issues involved of which we are not aware, but the standard teaching re growth-rings was not predictive with these bows.

The other related occurrence of grossly violated growth rings is in the Meare Heath artifact. this can be seen in Dr Stuart Prior's article on his paper on reproducting the original bow (see attached pic.). Dr Prior's replica is on the right of the picture.
Original-Meare-Heath-artifact-on-left.jpg
Original-Meare-Heath-artifact-on-left.jpg (19.09 KiB) Viewed 3800 times
It has no sapwood and had a lattice of lacing of some kind wrapped around it. Nevertheless, it too should have lifted via the chevrons clearly visible on its back. It broke or was broken at the handle, not the back as we know. I do not consider that the latticing would be sufficient to support such a badly violated back if the principle was universally true.

Just the same, I have always told others that if a bow was backed with some kind of tension resistant material, growth ring orientation of the stave is not an issue as you have realised. I am not about to jettison the principle of following growth rings just yet because nothing harmful follows from it as we know. But it makes for a lot of additional work.
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Re: Knocked out a quick longbow today.

#10 Post by yeoman » Sun Jan 12, 2014 8:00 pm

Dennis,

I think there is a difference between following a growth ring and violating grain. Of course when one chases a growth ring the grain is not violated. In your yew stave, while there is not one growth ring being followed, the grain itself is still not violated as at all points on the back I suspect the wood fibers run parallel to the surface of the back of the bow.

I suspect the same is true of your Gippsland mate, or at least he came very close to the horizon of acceptable grain violation.

On the feature bow of this thread, the grain is genuinely violated. Almost swirly (Well, I say that, but after looking for pure, straight grained timber for so many years any deviation from such seems swirly to me....). If I had made an unbacked bow from this stave, it would, I am quite sure, have broken.

I would agree with your comment about backing and grain violation, but with a sliding-scale-disclaimer: The stronger the backing is in tension, the less the underlying grain matters. A board with violated grain, backed with a rubber band, will still break. Backed with a steel band, it will take set until the cows come home, but will not break in tension.

I had a better camera today to take some happy snaps of the bow in question. I'm happy to say I no longer consider the fiberglass bowyers to be the only ones allowed to get away with using figured grain in the limbs. Woo!

Image

Image

Image

Image

Now while this camera is better than the one on my phone, the colour still doesn't come out quite right. The timber is a delicious smoky caramel colour.
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Re: Knocked out a quick longbow today.

#11 Post by longbow steve » Sun Jan 12, 2014 8:08 pm

Doesn't the growth ring rule mainly apply to ring porous woods and non ring porous will be more tolerant of not following a ring? Steve

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Re: Knocked out a quick longbow today.

#12 Post by Dennis La Varenne » Sun Jan 12, 2014 9:26 pm

About Dave's tillering job, it is actually pretty good in fact. Here is my analysis. The first pic shows chords drawn between the string nocks to the tiller to show the shape of the curve of each limb. The line drawn at right angles to the chord is placed at the point of greatest distance (see pic below).
Dave's bow_a.jpg
Dave's bow_a.jpg (76.32 KiB) Viewed 3785 times
Looking at the placement of these short lines, it can be seen that the left hand limb has its greatest amount of curvature further out along its limb than that in the right hand limb whose line is slightly shorter showing that the right hand limb is a bit stiffer. Both of the short lines are the same position along each chord which shows that the centre of the limb curvature is at the same position.

The second picture shows two shorter chords on each limb firstly from the string nock to where the vertical line from the major chord touches the limb and secondly from that line to where the second short chord touches the bow at the tiller (see pic below).
Dave's bow_b.jpg
Dave's bow_b.jpg (76.49 KiB) Viewed 3785 times
These 4 shorter chords show that each of the arcs described by the limb curvature above them are almost identical within each limb, ie, the inner limb is the same as the outer limb curvature. Those on the right hand limb are also almost identical to each other.

On the left hand outer limb, there is actually NO flat spot or evident stiffness compared to the inner limb. Both arcs are as close to identical as possible.

So, summarising, the arcs described by Dave's limbs are very close to circular in shape with the right hand limb being a circle of slightly greater diameter, and therefore. the limb loading will be very close to equal between limbs.
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Re: Knocked out a quick longbow today.

#13 Post by bigbob » Mon Jan 13, 2014 8:27 am

Great work Dave! Tiller looks brilliant to a glass guy and good to see the grain pattern in the limbs, swirly and all!
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Re: Knocked out a quick longbow today.

#14 Post by greybeard » Mon Jan 13, 2014 8:31 am

yeoman wrote:Okay, so one of my hypotheses was about wood selection. And this may seem to be a no-brainer to many, but it was an epiphany to me recently. The purpose of a bamboo backing is in part to be an unviolated layer of fibres on the back of the bow. Anything below this layer, in terms of grain, matters little if any.
Dave, bowyers in America have been doing this for many years, Dean Torges showed me the technique about ten or so years back. It probably has been done for centuries but nobody has bothered to make comment.

The handle section in this Brigalow board bow most likely would have failed had it not been for the bamboo backing.
Brigalow Belly.JPG
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Re: Knocked out a quick longbow today.

#15 Post by Dennis La Varenne » Mon Jan 13, 2014 2:11 pm

Dave,

The Red Ironbark bows I had from my Gippsland mate are worse than your board. He just planed the underbark wood dead flat straight through the usual lumps and bumps of a tree stave. The surface was what is variously called 'board sawn' or 'back sawn' with chevrons going in both directions on both back and belly.

My Yew ELB mentioned above has sapwood about ¼ of the stave's thickness - a much greater proportion than on the depicted MR section. The growth rings are quite fine, but I can easily make out that I have cut through up to 3 rings and the back has no flat surfaces at all. Another gorgeous little Yew static recurved rectangular sectioned bow I got via eBay from the US has unbacked sapwood back and it is a mass of chevrons in all directions.

With the local wood species being mostly perennials, I have long considered that the violated growth ring principle is perhaps nowhere near as important because of the nature of the 'early' wood not being anywhere nearly as porous nor thick as in the northern hemisphere deciduous trees.

With Daryl's Brigalow bow above may or may not have broken unbacked, but neither he nor any of us can really know unless it does break and we find out why. In the meantime, I am going to make some bows from indigenous wood when I can get it locally and see what happens if left unbacked.
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Have the courage to argue your beliefs with conviction, but the humility to accept that you may be wrong.

QVIS CVSTODIET IPSOS CVSTODES (Who polices the police?) - DECIMVS IVNIVS IVVENALIS (Juvenal) - Satire VI, lines 347–8

What is the difference between free enterprise capitalism and organised crime?

HOMO LVPVS HOMINIS - Man is his own predator.

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Re: Knocked out a quick longbow today.

#16 Post by greybeard » Mon Jan 13, 2014 4:35 pm

Dennis La Varenne wrote: With Daryl's Brigalow bow above may or may not have broken unbacked, but neither he nor any of us can really know unless it does break and we find out why. In the meantime, I am going to make some bows from indigenous wood when I can get it locally and see what happens if left unbacked.
Dennis, I did start on a second bow from the same milled board. This bow was not backed and had a similar grain run off just inboard of mid limb. The bow had the short string on and I was gently exercising the stave during weight reduction.
Without warning the limb exploded and I had three pieces of timber on the ground.

If it had been an air dried billet and not a milled board I believe a bow would have been possible.

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

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I am old enough to make my own decisions....Just not young enough to remember what I decided!....

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Re: Knocked out a quick longbow today.

#17 Post by Nezwin » Wed Jan 15, 2014 8:21 pm

Long time lurker, first time poster. Once I get my current run of bows finished I'll post an introductory thread with a few pictures of how I do things & how it differs from a few other folks. Lots of great info here & a great attitude among members for sharing info.

Weighing in on the growth ring/backing discussion, while living in Vancouver, BC last year, I was lucky enough to undertake a bw building course with Jamie McDonald, bowyer with Ravenbeak Natureworks (http://www.ravenbeak.com/ - well worth checking out some of his work with yew here). Aside from getting a great little yew flatbow from it, I also picked up a lot of new skills, especially working with selfbows & tillering - I'd always worked with lams up to that point, not even a board bow. What surprised me was his attitude toward 'chasing the ring', basically being not to worry too much about it. We cleared the bark off of the back of the yew billets with hatchets which inevitably violated a few layers but it turned out to be now such a big deal. His reasoning was that, due to the tight spacing of the rings in yew, there was a lot of leeway in working with it. My Bowyers Bibles are all enroute from the UK at the moment so I can't verify what they say but I'm pretty sure that goes against the recommendations there. Regardless, my yew flatbow still shoots well, albeit with a lot more set & a little less poundage than previously.

Personally, I've always backed with fibreglass (cloth primarily, but more recently homemade pretensioned e-glass lams) and wouldn't do a build in any other manner (except, maybe, for a little experimentation like yourself, Yeoman). I came to the conclusion long ago, however, that underneath the backing, it's pretty much an open field as to what you do with the grain.

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Re: Knocked out a quick longbow today.

#18 Post by greybeard » Thu Jan 16, 2014 4:08 pm

Welcome to Ozbow Nezwin, looking forward to seeing photos of your work.

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

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Re: Knocked out a quick longbow today.

#19 Post by yeoman » Sat Jan 18, 2014 5:47 am

Nezwin, welcome again, and I too eagerly await seeing your work.

Daryl, like I said: I don't know why this didn't occur to me years ago. I could have saved myself hours looking for particular grain, instead looking for attractive colours and grain instead.

Dennis, the limbs probably are balanced. Problem is, because they taper in width and thickness, in all honesty the tiller should be much more elliptical. I think I will try to remedy this by removing wood from the sides of the outer half of each limb rather than thickness. This will reduce mass more efficiently and hopefully have a more beneficial effect on arrow speed.
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