Primitive Archer
Main Discussion Area => Bows => Topic started by: Aries on August 11, 2009, 08:37:19 pm
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Can you guys please help me diagnose the cause of this bows explosion? I had just completed floor tillering this bbo stave and had been flexing it up to about ten in... when i attempted to string it with a short string it exploded at one of the nodes of the bamboo outside of the handle. The grain of the osage slates was fairly straight but my bamboo was relatively thin at the area of the explosion.
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Hinge, To me it looks like you got the fade area a little too thin.
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ugh that sucks, i didn't even notice it bending much through that region i was focused more on the outer limbs than the inside. So what do you think should be different next time? Do you think making my handle riser longer would help? this one was 12"
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A 12" handle is a little long if you don't have a power lam between the bamboo and the belly. It depends on the length of the bow of course, but 6 - 8" is fine for the handle and the power lam should extend at least 2" beyond the handle at each fade.
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can you please explain the concept of a power lam to me for future reference. This bow was a RD and i just traced the curve of the bow onto a 12" piece of wood and cut and paste. If i was to do the power lam would i just need to clamp it between the bow and handle when i glued up the handle.
Im really wanting to make one of these bows This is my second failed attempt. but Im learning tremendous amounts about them each time I make one, Im hoping to have my first lam bow soon still.. I've already started cutting up wood for my next attempt ;D
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too bad :( Keep at it though.
the power lam goes between the bamboo and the osage. you dont need one if you have enough belly wood to work with just make it ramp up in the fades before your glued on riser.
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This bow has 2 power lams between the bamboo and the ipe.
(http://i168.photobucket.com/albums/u169/WIbowyer/DSCN0843.jpg)
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I have to agree with Dano. I try to take more wood off the side instead of the belly , tillering boo backed bows.
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Interesting break. Can't say I've ever seen Bamboo break like that. Personally I don't think a hinge would do that. Hard to tell but you may have worked the the node down too much.
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There is a lot of stress in that portion of each limb. Maybe the node should be placed so it doesn't lay right at the limb/fade transition area. Just a guess.
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Pat summed it up to my thoughts exactally.
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Normally a node will create a stiff spot, so it's a good idea to place them evenly. The node doesn't look like it's been worked down too far. Who knows. ???
Maybe if we could see a picture of the handle and the limb that didn't break we could make a better assumption.
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Did the glue line fail or did the boo fail? What glue did you use?
A bit of glue and a wrap will have you shooting again by the weekend! ;D
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take a real close look at the nodes i can see where it s been filed down or sanded or somthing looks like the node was weakend and thats right where i see the clean break where it snapped in the pic my 2 cents brock
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I hadn't worked the nodes down any at the point the boo gave. My glue bond held strong it would seem because torn osage fibers line the inside of the boo. It just looks like the boo snapped clean off at the space on the node. Here are some pics of the other side of the handle. I didnt have my nodes evenly spaced on this attempt, mainly because i was just using what material i had available, and i couldnt space it properly with this piece of boo ::) pat) I used urac 185 to glue this up. And what kind of thickness do you guys think i should start with on my osage boards if i was looking for a bow of same style with a finish weight of around 60-65 lbs on a 64" ntn bow?
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dnt know about your bow,but that looks like a buck folding guthoohook knife with the wood scales
i have the same but wit the rubber grips,easier for me to hold when its bloody >:D
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lol it is my constant compainion, A pretty darn good knife.. and i like it even more because i got it for cost through my work ;D ;D
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Here's my completely novice theory. It looks like there is a knot in the osage just to the handle side of the break. Knots cause a stiff spot. And, this knot is just at the taper of the handle fade where the bow should be bending slightly. So you handle= stiff area, then you have knot = stiff area, followed by a node= weak spot. The node area was absorbing on the preasure in transition from handle to limb. Like I said this is a novice theory. I've never attempted a lam bow.
Dave
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unlucky break ,you have to just get the next one started and put it behind you.the trials of bow making huh?
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ya mox thats what im thinkin, I just try to learn as much as i can from each failure such as this one. And hedgeapple that dark mark that looked luike a knot was actually just a grease smudge ;)
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My opinion, bad bamboo, shouldn't have broken like that. There is some good and some bad bamboo out there, I have had a bunch of the latter.
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i hope its the latter because i thought i had done everythinhg right up to this point. I have several pieces of bamboo that came from the same location in alabama. do you think that it could possibly all be bad? Speaking of.. Ill be looking to trade for some more bamboo lol i have osage and snake skins shoot me a pm ;D :P
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Looks like bad Bamboo to me. Was there any grain run off in that area in the osage ? Dean
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If there was there would be very little, I had the grain running most of the length of the bow.
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Bad bamboo. Looks like a typical case of bad bamboo. Good bamboo will not have so few splinters when (IF) it breaks. This bamboo is just not strong, it lacks powerfibers - so to speak.
A simple test for a bamboo slat: Take a 1" wide slat, about a foot in length. Bend it 180 degrees by hand. It should not break. It may (or may not) desintegrate with many fibers sticking out, but it should not snap.
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thanks dark, i will likely be usin that test quite a bit in the future ;D