Primitive Archer
Main Discussion Area => Bows => Topic started by: soy on October 11, 2012, 08:41:12 pm
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The broken bow club that is... I don't want to go into details on what a thorn in my side this thing Has been >:( this is my first bomb , it probably won't be my last throw little duck tape on her and away we go ;) it was hhb with 2 layers ofsinew ... to dry? ???
(http://i1082.photobucket.com/albums/j380/thadsoy/photobucket-32753-1349995083928.jpg)
(http://i1082.photobucket.com/albums/j380/thadsoy/photobucket-28912-1349995045558.jpg)
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how long was it? weight? limb width?
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It was 68 inches ntn mid 50's at 28 inches, and just shy of 1.75 inches at the fades tapering do 7 sixteenths at the tips
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Welcome to the club...don't know why it happened, but I feel ya. I've had a sinewed hhb blow on me as well, n it was in front of some fellow bowyers :-[
It happens, but ya just learn n figure out why and move on. Sometimes there's nothing you could've done to prevent it, cus some pieces of wood just don't wanna be a bow. Good thing woods a renewable / replaceable material that grows on trees ;)
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Was it completely tillered and shot in or a work in process? Heat treated ? Violated back?...............................Standing deadwood? HHB can take alot of abuse.With a sinew back I would think near bulletproof. I've only backed with linen cloth myself ,but the little one I made for my son nearly turns itself inside out.See if you can figure it out and learn from it. Some of the ones I broke seemed like a mystery until sometimes weeks later when the lightbulb went off.
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Okay I guess I will get to the thorn in my side... this is my last cured piece of Ironwood I had made it a serviceable bow but due to a not by the fade it had a bit of a beauty hump and it made that lamb a little bit to the deflex well the other held reflex... doing the heating in bending I got a little heavy handed and cracked the belly I was able to get under the damage but left the bow a bet light in poundage so on goes the sinew, I only got 1 layer on as I grossly missed judged the amount needed I put 2.5 more layers on, tillerd it and the shot the snot out of it... as I was going to back it with a snake skin I noticed the first layer in the rest of the layers were not bonding well together for whatever reason... so I removed all of the sinew and glue(and turnd it into glue) resized it, re backed it with some reflex added ... had it in the dry box took it out waited 3 days I exercised it, made a few scrapes on a stiff part, shot it about 20 times, was checking the weight and BAM! I was supposed to have this 1 done in April I was a bit overdue :P Now back to the old drawing board
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Okay I guess I will get to the thorn in my side... this is my last cured piece of Ironwood I had made it a serviceable bow but due to a not by the fade it had a bit of a beauty hump and it made that lamb a little bit to the deflex well the other held reflex... doing the heating in bending I got a little heavy handed and cracked the belly I was able to get under the damage but left the bow a bet light in poundage so on goes the sinew, I only got 1 layer on as I grossly missed judged the amount needed I put 2.5 more layers on, tillerd it and the shot the snot out of it... as I was going to back it with a snake skin I noticed the first layer in the rest of the layers were notticking bonding well together for whatever reason... so I removed all of the sinew and glue(and turnd it into glue) resized it, re backed it with some reflex added ... had it in the dry box took it out waited 3 days I exercised it, made a few scrapes on a stiff part, shot it about 20 times, was checking the weight and BAM! I was supposed to have this 1 done in April I was a bit overdue :P Now back to the old Ron bored
Man you go far to save a bow;-).
Its a bummer man....I cant imagine how a sinew backed hhb could end up like that. Wood is wood however, its alive and has temperament....sometimes its cooperative, sometimes it needs to be "broken in" and sometimes its so damn stubborn that it will rather break than cooperate.
Cheers
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To bad but like has been said it happens,had more than I can count over the
years. HHB is usually bullet proof and with sinew just don't know. I would cut a little piece out of one of the limbs and do a bend test.I do that a lot on a questionable piece of wood.I have had HHB and Hickory both do that and the backs were dried out, dry rot I guess, done a bend test on a small piece and it would explode so I cut up what I had left and cooked with it. Sometimes just bad wood that you can't see.I hate them kind of blow ups the worst,bad enough if I know what caused it ,hate it when I don't. :)
Pappy
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You obviously haven't read that bit in the book where it says a sinew backing makes a bow virtually indestructible O:).
I feel your pain, I made a little sinew backed Ash bow ages ago using TBII it went just like yours... I haven't plucked up the enthuisiasm to try agin yet :-[.
But one day...
Del
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It happens. I'm not one to heat and contort a stave to remove every little bit of character but I can understand the need to do that but with that comes consequences. The key is to learn something from every mishap. Like I say, "If you ain't breakin' you ain't makin'!"Jawge
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Bummer!
I, like you , keep building and building and trying to fix until the end!
I'll probably be the only to say, good work, nice fight.
But it's not over yet!
Take the unbroken limb, put it in the corner. Next time a bow pops or otherwise offends, save that good limb too.
Splice em together.
Could be real interesting or another exercise in futility.
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After hearing the rest of the story , my guess would be that it was doomed before the backing went on. When you heated and cracked the belly (I'm guessing reflexing) ,that crack had already started through the grain towards the back.Backing may save a back but doesn't help a comprimised belly. When you bend a bow . all of the fibres on the back are pulling away from each other ,while the cells on the belly are crowding each other like too many people trying to get on a train. As it compressed , the two pieces on either side of the fault line slid past each other on the belly side and started the whole process not unlike an earthquake. The combination of hardening the belly with the heat,small fissure started on the belly and the extra strain that the sinew placed on the belly sounds like the overall cause of your bow's demise. The belly is as important to the bow as the back and can't be minimalised.A damaged back is easier to deal with IMHO.Sorry about your loss.
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Like the boys are saying, "it happens to the best of them", even with sinew backing there's no garrantee she won't blow apart even if you've done everything right. I once built a little mountain maple bow, sinewed the back and took it with me on my walks through the woods every day shooting stumps as I walked. One day I pulled back to shoot a grouse and it blew apart in a million pieces, I don't know why, it just happened. Just suck it up and keep turning em out. You'll have more success than failures! Dale
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I feel your pain, had a sinew backed osage blow on me for no good reason a few weeks ago. ??? ::)
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Lostarrow... That could very well be the case as the failure was about 3 inches tward the tip from the belly crack , my other thought I would be the same time only had 3 days out of the drybox with low humidity That it may not have Absorbd enough moisture...
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I know some guys will probably jump all over this one but here it goes............ When you "heat treat a piece of wood ,what you are doing is removing the moisture from the cells. The more you do it , the less moisture. Wood is made mostly of water while growing ,and when we cut it ,it starts losing that water immediately. When they talk about a piece of wood reaching equilibrium they are talking about it losing or gaining moisture ,relative to the ambient humidity present in the air.(RH- relative humidity) When a piece of hardwood is brought down to say 10-12% MC(moisture content) the cells have shrunk significantly already. They will never again be able to contain as much water as when fresh cut.Even if submerged in water.If that piece is brought out of the kiln in mid summer when the RH is 80-90% it will absorb some moisture and maybe creep up to 18% or so depending on species.After the winter when the air is drier and the board has come down to 6-8% in some areas ,in the spring and summer of the following year,it will not get back up to the 18% it did the following year.And so it goes through time until the wood has lost more and more ability to hold the moisture that once made it flexible.Old and brittle. Some woods fight this better than others . When we heat treat we are artificially collapsing the cells(shrinking them ) making the wood more compact but in turn ,less able to absorb moisture. The wood turning brown from heat is the sugars in it caramelizing,just like onions in a fryingpan or sugar heated with a torch on Creme Brulé. MMMMMMMMMMM yummy! the more sugar ,the browner it gets. When the wood reaches a point where it no longer contains enoughwater to keep the temperature below the woods flash point, it cumbusts.You don't need a spark or flame to make fire, you just need enough heat. If you leave the heat gun on the same area too long you shrink the cells to the point where they can no longer bind to each other .Too much of a good thing.If you can heat a piece quick enough,you can harden the outside without collapsing the cells all the way through to the back.If its really thin and the wood doesn't contain much sugar, you may wind up drying the whole piece through before you see any toasting happen. the cells on the back have then collapsed and are no longer able to regain enough moisture to become elastic again.You now have a dry brittle piece of wood. Try this for an experiment,it might give you a better idea ,visually of what is going on. Take a piece of wood 3/4"x3/4"x24" long. Straight grain(ish) Square and straight.Heat one side only , in the very center, for about 6" or so .Heat it until it becomes light brown on that side only.Maple would work good for this.The two ends on the side that is heated will draw into reflex because the cells have shrunk.The piece of wood will now be narrower in the middle as well . The side closest to the heat will be narrower than the side farthestThe piece may also twist ,depending on the grain.The cells closest to the outside of the tree will be larger and therefor shrink more. On a larger sample you can shrink one side until it cracks the opposite . This is what happens to your staves when they dry and split. The larger cells shrink more than smaller ones near the center of the tree or around knots.Back to the experiment......... Measure the size at the middle and both ends. Now throw the piece into some water for a few days. Extreme ,I know , but leave it for the amount of time that you would leave a bow after heat treating. Take it out when you are satisfied that it can gain no more moisture . Dry it off with a towel and stand or hang it somewhere to dry so that it dries even all around. When it no longer appears wet on the outside, measure your spots again. The ends should be larger than 3/4" the toasted side is probably the same and the side opposite might be marginally larger but still smaller than the3/4" you started out with. the cells will never be the same even on the side you didn't think you heated.Some guys use oil when they are doing heat correction ,as the oil has a higher evap. temp and keeps the cells from collapsing while bringing the wood to a temp.high enough to bend.Just make sure it's compatible with your finish.Contemporary accounts of native bowyers of the 19th century said they applied grease or oil from animals to the back of the bow to keep it flexible while they were making it and throughout it's working life .Once again ,if you wanted to sinew back it ,this would not be advisable. Hope this helps. Sorry if it was long winded,but there is allot of info for one small aspect of wood.
Cheers, Dave.
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Thank you...makes sence ;)