Bow forms...any critiques from the pros?

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1/2 " thick juniper, 5/4 " wide. 28" long in total. The form is a 2x10, so 9.25" wide. The core slipped up about 1/4" while i was cranking the sal flat.

god, i have no idea what i'm doing. I think 1/2" thick is too thin....that it won't hold the horn into conformed shape. But i am experimenting with these forms and so here we go. I boiled the wood for about an hour. It was air dried, from a branch i found a few months ago, which had already been cut down. I don't really intend to use these cores for a hornbow...they are not the best pieces. But i will probably splice a grip in between and sinew back them, just to practice this style of bowmaking.

This is looking good so far. Very similiar to the way I do it. For to avoid any splintering I work the wood down to one growthring on the back and the belly- side of the wood.
I don?t think that it will be worth to splice and to sinew- back the 2 pieces for to make a bow. Juniper hates it to be a short bow, other than you make a backed shortie with wide limbs(westcoast- style).
Michael

You realize you made only one bend in your form? There are two: one for tip (over a small radius), the other for kasan/sal (large radius). The angles for both bends are no more than 45deg, actually less for the tip. Best copy the shape of an old bow from a picture.

Adam

Adam this form is based on the one shown on page 75 in your book. What did i do wrong? Are the angles just too sharp?

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This is the lath 12 hours after clamping. There was a little springback. The other lath broke after boiling for an hour. So...no little practice bow just yet.

I'm looking at the pics of bow forms on p.73 in Karpowicz, and comparing them to the one i thought i was imitating. The ones i made, in the above photographs, add up to about 100 degrees. The sal portion is flat, with 5.5" along a 45 degree angle through the kasan, and then the tip angles back sharply. Too sharply, i see.

I see the curves are much gentler on the forms Adam uses, although until yesterday i thought they seemed extreme. I can see that his total angles are under 90 for 3-piece core forms. I'll have to re-do these, tame them down, make some more laths, and try again.

What do you think is easier for the new guy? 3 piece or 5 piece? Obviously 5 piece adds two splices to the mix, but glue joints are good and strong, that's not an issue. It's easier to coax a gentle reflex in a lath, and splice siyahs into the ends, than it is to force an extreme bend in a short piece of wood.

good times!

hi radius
I think a lot depends on the wood you are working. I broken with maple (old wood) 2 cm thick - kasan / bash angle. but especially with young acer tataricum always had success - even more than 2 cm thick. This is a unique wood for steam bending. problem that is difficult to find so long (not knots ) tree. i accept that three pieces is easier, faster, and cheaper. be very exacting to material for the core :wink:

Your core is bent only in one place, not in two. The forms have two angles to make two bends in the limbs. On the picture (pg.75) you can see the bent wood on the form as well.

Adam

Adam Karpowicz wrote:

Your core is bent only in one place, not in two. The forms have two angles to make two bends in the limbs. On the picture (pg.75) you can see the bent wood on the form as well.

Adam

i know :( fail

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maybe i'd be smart to re-shape the form like this, with extra length leading into the sal, and a manageable recurve which can later receive a siyah.

i reboiled the tip for an hour and a half, and got this bend:

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The rest of it would not bend. I need a bigger steamer. pvc pipe with a t and end caps.

yew lath, about 30" long, .75" thick, 2" wide. I soaked the end 12 or 14" in a bucket of cold water for a couple days, then threw it in the steamer for at least an hour. It bent very well. Just a little steady pressure and bada-bing! it looks just like a pro did it. Well, almost.

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its partner stave:

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In this picture i am trying to show the longitudinal cracks that developed when i bent the lath on the form. Didn't occur right away, but within a few minutes. I don't think they go very deep, maybe 1 mm. no problem.

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Next morning, after maybe 12 hours in the form.

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The back side of the lath: crushed in and outwards.

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So far so good.

I actually sawed up about 5 pairs of laths the other day, all pacific yew. Yesterday i made these cores, but i also used the same technique (and the OTHER side of the forms) to recurve the tips. I made the recurves different, even though the ottoman forms were the same. I'm going to practice grip splicing with these yew recurves, and also practice adding ears to them. I have alot more wood than horn, so i'm happy to use the wood experimentally, so that when i get to these two ottoman-style cores, i hopefully won't waste the materials.

I don't know if this information will be of any use, but people who bend wood professionally for furniture and boats have developed techniques for controlling whether the wood extends on the outside of the curve or compresses on the inside.

This is only a relative difference but it might have some benefits. One technique is to put the outside of the curve under compression with a metal strap with wood blocks at each end. The blocks fit over the ends of the piece being bent and the strap prevents the outside surface of the curve from lifting up. They also differentially heat each surface so one is softer than the other to cause one surface to be affected by the bend.

It might be worthwhile to experiment with these techniques, but I have no direct experience of their effectiveness.

Bede is right. I used this technique for bending of thick trees. instead metal band I work with wood strips- approximately 4-5 mm. thick. bend it together with the core wood and c-clamps brace on it. I like this method.

Is there any reason why you do not round the corners of your forms? The kasan/sal angle is OK, but way too sharp. The angle of bending and the radius (!) of bending are two different things.

Adam

Adam Karpowicz wrote:

Is there any reason why you do not round the corners of your forms? The kasan/sal angle is OK, but way too sharp. The angle of bending and the radius (!) of bending are two different things.

Adam

Yes, sir, there is a reason: the reason is that i'm a dumbass who never does things right the first time! Yes, i am going to tame those corners down.

The sal/kasan angle is 45 degrees. This is too much?

Steve, you are too hard on yourself.. it can get complicated.

The 45deg is OK and the angle can be (and usually is) later reduced after the bow is made to tiller. For a first bow it is safer to go a little less 35-40deg. Look on the pics in the book and bend the core to reproduce the shape of an old bow exactly.

The sharp tip bend is good and it makes it easier to tiller when the kasan below the tip is (near) straight for a little distance.

Adam

haha, i'm not too hard on myself...i just learn from my mistakes, when i can.



These two forms i'm going to adjust by rounding those corners down. I'll make another set of forms which have about a 35* angle, but maintain the sharp tip return, since you say it helps to tiller. I think i see what you mean.