Primitive Archer
Main Discussion Area => Bows => Topic started by: mole on October 12, 2007, 01:13:00 pm
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Howdy folks. This is my first real post here. I met a few of you at Pat's.
This piece of red oak has a lot of history. It was a 1x3 red oak board from Lowe's. It was made into a 74" 70# mere heath bow, but it had too much hand shock. It was cut down to 72" modified version that was 2" wide for most of it's length. It came out to 55# and bent too much on the inner limbs and was a very poor performer. It was then cut down to 68" and tapered from 2" at the fades down to 1/2" at the nocks in a pyramid style.
The bow had a good bit of set at the inner limbs, so in was coated in vegetable shorting pulled into 1 1/2" of reflex and heat treated on 10/03/07. The bow kept about 1/2" of reflex.
Tillering began on 10/11/08 after much humid weather. A long string with about 4 " of play was used to tiller the bow to 55# at 25". A shorter string was then used that gave the bow a brace height of about 1". As I pulled the bow to about 50#, she broke. Tillering was done on a tillering stick and with a knife used as a scraper.
Bow profile
(http://i188.photobucket.com/albums/z239/borwish/DSC02383.jpg?t=1192204127)
Belly
(http://i188.photobucket.com/albums/z239/borwish/DSC02379.jpg?t=1192204207)
Back
(http://i188.photobucket.com/albums/z239/borwish/DSC02380.jpg?t=1192204186)
Side of break
(http://i188.photobucket.com/albums/z239/borwish/DSC02381.jpg?t=1192204150)
Side at break
(http://i188.photobucket.com/albums/z239/borwish/DSC02382.jpg?t=1192203619)
This is the first bow break I have had. I've had good success until now, so I blame the heat treat. Maybe it was too dry. Help restore my confidence please. I've got a beautiful piece of Eastern Red Cedar that is begging to be an English Longbow.
Thanks,
John
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I would say it had been over stressed by the overbendiness in the lower part of the limb and the additional tension requirements of shortening caused a tension fracture. It was a pretty nicely shaped job for an early try. get a new board and start immediately.\
Dave
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Don't overlook backing it with linen, silk or something
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To me there is no doubt it was because of the grain run out into the handle area. The fades should have been a little farther away from the handle so the grain run out was not under so much stress. I made a tiny black line to show the grain direction, and a red arrow to show where it let go. Justin
[attachment deleted by admin]
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I agree with Justin, thing is, you should keep it completely stiff until the limb reaches full width. Especialy with board bows.
Sean
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I agree with Justin. To much bending into the handle fade.
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I agree with Justin ,Ryan.But I don't think it really came into play as a factor till you started shortening it and heating.Then you put the stress closer to the fades as you shortened the limbs.I also think it should have been backed to start with.Some of those boards have really been "cooked" and I think when you heat treated it you really dried it out and took away any flexibility left in the fades.
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Just to put in my two cents worth. I agree that the main problem was the handle/ fades. To throw in an enineering term I learned along the way, putting the fades too close to the handle created a "stress riser". Over drying during the heat treatment may have had an effect, as did shortening the limbs, but the real defect was always there. Ron
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Grain runout like everybody said. Dosent really matter how close fades were, grain runout would have done it (snap) anyway at some point. Build another nows not the time ta stop ! ;D..........bob
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Looks like a compression problem at the handle. I agree with Mullet, re-heating and straightening a kiln dried board is courting diseaster.
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Your Handle is too long so you stressed that area where it broke.
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Mole,
I'm gonna be contrary (at the risk of being banned or beaten) and say the break started at the mid limb area in the corner. I think everyone is right when they say grain, but I think one of the biggest problems is that the edge of your limb is to sharp. So iffy grain coupled with a sharp corner on the limb is why it broke. If you round the edges of your limbs more you tend not to get a break that starts on the edge like I think that one did.
The first photo has an arrow showing where I think the break started. The second photo shows in my opinion the last area that let go.
[attachment deleted by admin]
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I have to agree with hunterism.
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Thanks for the replies and advice. Would using a three inch fade instead of a two inch fade and more rounding of the corners have prevented this from blowing.
Mullet, If you remember Bruce from Pat's, he has now officially renamed you "The Wildman"
Thanks everyone,
John
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Would using a three inch fade instead of a two inch fade and more rounding of the corners have prevented this from blowing.
Now that is the question. We can look for causes and second guess ourselves all day long, but sometimes they would have broken no matter what you did. My best guess is it would have helped. To say it would have prevented is a step I wont make. It is possible that you could have done all that and backed it and it would have broken. But all those things would significantly reduced those chances. Its like the old saying, a bow under stress is already 95% broken. Now I will add, what we do just determines if the remaining portion that isn't broken is 4% or 6%.
It isn't really longer fades you are after. It is making sure you get to a non bending thickness before you start to reduce width to much. You could make the fades longer, or you can make it a steeper angle. You want to keep the bending in the full width limb as much as you can. Justin
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I'm with Huntersim on this one too.( nyah-nyah Justin :P) Seems like theres some splinters left near the fades while its a clean break from the sharp point on back to the splinters. My first inclination was not enough rounding to the edges but hey I've broken more bows than anyone in the history of the world so what do I know? ???
Chris
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I'm with Huntersim on this one too.( nyah-nyah Justin :P) Seems like theres some splinters left near the fades while its a clean break from the sharp point on back to the splinters. My first inclination was not enough rounding to the edges but hey I've broken more bows than anyone in the history of the world so what do I know? ???
Chris
Oh come on Chris dont you have something new to say. ::) I think I have broken more bows than you anyway. Just havent broken more hickory backed cherry. >:D The splintering is on the riser. All the rules go out the window when that happens. I have had them break just like that. Even had on splinter going one way then turn around and splinter the other way. Removed a nice wedge right out of the middle. ;D Justin
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Hi,
I think it broke because: it's oak, it's not an optimal piece for a self bow, and it was not well tillered. These are usually the reasons any bow breaks in the tillering process. You're asking too much of too little. Oak is fine, but for a piece like that, back it. Hickory, linen, silk, rawhide... take your pick. Go get another piece, and start again! If you're not breaking stuff, you're not pushing the envelope! There is only one way to find out how far you can push...
Bye the way, your design looks good.
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I'm with Huntersim on this one too.( nyah-nyah Justin :P) Seems like theres some splinters left near the fades while its a clean break from the sharp point on back to the splinters. My first inclination was not enough rounding to the edges but hey I've broken more bows than anyone in the history of the world so what do I know? ???
Chris
Oh man, I've already risked being band by Justin (who's opinion i highly respect) by being contrary, but Now your gonna rub it in Chris......Oh boy :)
I think everyone has made some good points. Infact Justin said it, we could go on second guessing ourselves but broken wood happens. I have a feeling it was a number of factors so next time stack the odds in your favor. Try not to allow the limbs to bend to much near the fades, round the edge of the limbs more, look at the possibility that low moisture had an effect, etc.
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Actually, I'm going to have to switch loyalties here, it looks to me like the belly part near the fade broke in compression brought on by the other part of the bow breaking.
Here is my theory; the bow broke a little in front of midlimb, then bent too far in the area near the handle, putting too much compression there, causing it to fold under the stress. The wood there, being under a lot of tension, separated along the easiest path, with the grain right through the fade. How's that? I'm a traitor, sorry Justin. :'(
Sean
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Yep,thats a broken bow all right. Looks like an excellent pattern to keep on hand though. Start on a another bow,but check around for cabinet makers in your area,they usually have better oak than the depot or lowes,bow boards are truly hard to find there. Keep trying if you dont break some youre not learning! Auggie.