Primitive Archer
Main Discussion Area => Bows => Topic started by: DarkSoul on February 11, 2015, 07:06:46 pm
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Although I don't usually build many bows in winter due to rain and lousy weather in my cold shed, I've just finished two bows last weekend :) Here's my most interesting one.
It's a European ash (Fraxinus excelsior) flatbow, with a trapezoid cross section and heat treated belly. Pretty much an experimental bow, where I tested this woods capacities. I've used a stave from this particular tree before, and was then highly impressed by the quality of the wood. It's really dense, with fat growth rings and an excellent earlywood/latewood ratio. There were hardly any knots in this big tree, which is also evident in this bow. There is not a single knot in it. However, there are two areas in the lower limb with distinct curves, making the bow appear poorly tillered and hinged.
To test this wood, I made a rather narrow bow for her draw weight of 54 pounds (up to 36 millimeters wide - almost 1½"), with a heavily trapped back. The cross section is trapezoid, with the back about 60% the width of the belly. To increase the belly compression resistance, I performed a heat treatment with a heat gun for about 30 minutes per limb. The bow was clamped in roughly 2" of reflex. She now maintains about 3/4" of reflex, becoming pretty much straight after shooting.
I dressed her up with some marbled West African ebony tip overlays, made from wood that I took from Africa myself. Since the bow was to bend through the handle, I could not apply a riser. But the flat belly with square edges was not comfortable to hold in the handle. So I opted for a cork handle. This allows bend through the handle, while maintaining its shape. I'm not completely happy with the handle, though. It's a bit too wide. I should have left it slightly thicker, so I could have narrowed it a wee bit. A small piece of cow horn acts as an arrow strike plate.
Statistics:
70" nock to nock
54 pounds at 28"
Width 36 mm tapering to 11 mm nocks in a straight line
Thickness 19 mm tapering to 15 mm
(http://i60.tinypic.com/10d5oh0.jpg)
(http://i61.tinypic.com/2qx4abb.jpg)
(http://i58.tinypic.com/2jd19wl.jpg)
(http://i61.tinypic.com/t5m3jc.jpg)
(http://i62.tinypic.com/vo09oz.jpg)
(http://i59.tinypic.com/10y06iu.jpg)
(http://i57.tinypic.com/17s7k5.jpg)
(http://i59.tinypic.com/2vbty8n.jpg)
Unbraced side view to show the profile.
(http://i58.tinypic.com/2i28ok8.jpg)
It's hard to capture the trapped back on camera. But I think it is best visible in this picture. The back is facing upwards.
(http://i57.tinypic.com/2uzowmh.jpg)
And of course the money shot! :D
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Very unique looking bow. Was it hard getting a good tiller out of it? The cowhorn inlay is nice.
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The solid cork handle is kinda neat. :)
DBar
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Cool bow your Darkness. That grip is nice.
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And the money shot is of course...money. Nice bow. It looks like that bottom limb would have been a bugger to get figured out but you did. I like the cork idea too. I been thinking about doing a shorty bend thru the handle but don't like the flat feel, so I think the cork is the answer.
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Nice bow :)
Ash is pretty darn good when treated right eh?!
8)
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Nice work! What was your reason for trapping the back?
I think the general stats are pretty impressive for European ash. At 19 mm max thickness the maximum elongation of the back of your bow is about 1%, which is remarkable given that you have very little set in the bow. Both the trapping and the toasting do help to reduce set, but it's not easy to balance.
Tiller is also very good in spite of the hinges (though the tip of your upper limb is a tad stiffer).
Joachim
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Mmmmm catkins :laugh:
Cool bow, like the cork grip/arrow plate... cool.
Del
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Cool bow, I like the overlays and the horn strike plate.
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Lets see the other bow you finished!
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The cork and inlay are really well done. Plus the bow looks great also.
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Thanks for the comments, guys :)
@Shaneisneato: it was not easy to get this one tillered. The whoop-de-doo in the lower limb gave my fits. I still think the upper limb is a bit too stiff, but I'm not sure.
@Mikekeswick: yes, this ash is wonderful stuff :) Different from American white ash we can get at the lumberyard. This wood seems almost unbreakable. It picked up about 10% draw weight in heat treating.
@joachimM: ash is very good in tension, but not great in compression. Narrow-ish ash bows tend to suffer from a lot of set, while they don't often chrysal. To me, this indicates a clearly tension strong wood. To lower the pressure on the belly, I left the belly wide, while narrowing the back to increase the tension there. To further help to prevent set, I heat treated the belly, which has often been proved to reduce set in whitewoods. The combination of heat treatment and trapping seems to work really well with ash, given the low set and snappy feel.
@Del: yes, cat-kins :p The only bit of spring so far is the hazel that is starting to flower.
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Fine job tillering that bottom limb. Those kinky roller coaster type bends can be a real challenge. You nailed it.
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Very nice.