Primitive Archer
Main Discussion Area => Bows => Topic started by: FilipT on August 27, 2016, 12:39:03 pm
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I don't have picture of bow in real life, as its clamped and put in shed to dry. I drew in Paint a simple representation of one of the limb ends.
It has big knot also.
My question is how would I tiller that?
Note: bow is supposed to be longbow, its 78,4" from tip to tip, going for full circular bend as they were in medieval times.
(https://s15.postimg.org/h3glcj9ej/qweqe.jpg)
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That area will be left a little stiff. How far from the tip is it? What draw weight are you shooting for? 78.4" seem a a bit long to me.
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It is going to be entry into warbows, around 70, 80#. Tillered to circle like it should be, I think it will be awesome looking character English bow. I think its almost a foot away from tip, not sure, I will measure tomorrow.
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I would heat it up and straighten it out. Then side view tiller will be as per normal.
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I think the obvious answer is as Slimbob just pointed out. Do your best to straighten it out. Otherwise you won't be able to get the circular shape you desire.
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it does not have to be straightened out, will shoot fine as is,, that would just be up the the bow maker,,
circular tiller is probably the most traditional, but not necessary for a good shooting bow,, especially at a shorter draw,,
for a 76 inch bow a 32 inch draw or something close would be needed to get the bow shooting well,,, the bow will have to much mass at a shorter draw and circular tiller to shoot as well as it could,,
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What Brad said is right, it does not have to be straightened. My opinion, it is easier to tiller if it is straightened, and more pleasing to my eye. In the pic, I had a similar issue. The big knot kinked back into deflex by 30 degrees or so. I heated it up with dry heat and straitened it out. 66 inch bendy handle. 65 lbs or so. The tiller profile as a result, is as though there is no knot. I could have left it as it grew and and tillered accordingly. I just think it is more aesthetically pleasing when straight. Personal call on it.
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32" is the plan. Can I really straighten this kink and should I? Wood grew that way and isn't it general agreement to follow the grain and the way wood grows, but make small adjustments if we can.
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It is going to be entry into warbows, around 70, 80#. Tillered to circle like it should be, I think it will be awesome looking character English bow. I think its almost a foot away from tip, not sure, I will measure tomorrow.
I wouldnt worry about it in the least bit and just build the bow. Hard to ignore a thing like that but thats what I would do.
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I really like the shape and wish it would stay like that. I am only worried about possible breaks and such, if that area is overstrained.
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There is no reason it would break there unless you do something wrong!
Elb's shouldn't have a 'circular' tiller - they should be elliptical. An elb has a large thickness taper. The thinner wood gets the further it can bend. Thicker= less bend. If you tiller your bow to an arco fa circle tiller you will get handshock.
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Yes, sorry, I meant elliptical but didn't know they use that word to describe elb tiller.
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Here are pictures of mentioned area. That kink is 50 cm far from the tip.
From the front side (viewed from belly). Notice the block of wood under the clamp.
(https://s14.postimg.org/69ry8hjlt/IMG_20160828_112109.jpg)
Isometric view on the kink
(https://s14.postimg.org/v1rkfq0sh/IMG_20160828_112042.jpg)
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I would do some heat correcting on that stave.
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Looks thin right at the knot.
Upon closer inspection maybe not. Thickness taper looks off but the knot appears up and thick behind it.
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Everything is ok, thickness taper was produced by thinning down limb in each segment to a measure according to rough estimate drawing made in AutoCAD.
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Looks like your ok. As a suggestion, and this is something that lot's of seasoned guys have talked about, thickness taper needs to be smooth from handle to tip. Take your thumb and index finger and run them along the top and bottom edge of the limb,each side. Eyes closed if it helps. You can feel any thin or thick spots and address them early on. Knots will change the equation a bit, but just factor them in. Thin spots can be an ender if they are not dealt with early on, and the above can help you detect them way early on.
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I always do that technique you described. After making rough work to the lines with draw knife, I use sandpapers and planes, sometimes even electrical plane to make really flat surface on the belly of limbs. There is this tool which I don't know how is called in English that has sides perfectly aligned on the 90 degrees from each other. I use that tool to see if everything is flat.
What to do with knot ends on belly? You can see there is a "dot" on belly picture. That is other end of knot that is on back of the bow. I passed over belly side and made that flat. Is that error? I never encountered knot so deep. If I leave that dip stiff, as after all its only 2 inches wide or so, could I avoid problems
if there are problems?
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I totally ignore knots on the belly. Be careful not to rip them apart but aside from that, tiller right thru them.
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I really smoothed whole limbs and of course with it that knot on belly side. So just tiller it as a bow without knots?
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Not that I have much experience, but I ignore knots on the belly. Leaving it stiffer didn't work well for my first bow; it took set between two stiffer areas marked by knots. And that's with yew.
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Maybe a little flat around the area, but that is a judgment call. I prefer not to leave an area flat if I don't need to. If you are concerned, just a bit flat, otherwise tiller right thru it. At that length, you should be fine. Again we are talking about knots on the belly. This one is a knot on the belly, but also a knot on the back which is different. Knots on the belly, ignore them for the most part. Knots on the back have to be taken into account. Wider around the knot, leave flat if you have to. Flawless back around the knot.
Remember also that thicker wood wont bend as far as thinner wood. It will take set or break. Breaking will be what you need be concerned with because of the knot. That is the reason I mentioned thickness taper earlier. My opinion, you don't want a big gob of extra wood tucked up inside that knot. The extra width should ideally be the modifier giving you more wood AROUND it. Having said allllll of that, this looks like a non issue at that length and it being close to the tips. Just trying to give you food for thought.
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Its 50 cm far from tips, not one feet as I said in beginning. I worked back around the knot good and I left enough of bulge around the knot as you can see on belly side photo so I think this will be alright.
Unfortunately I will need to wait maybe a month to start working on it, after all its green wood.