Trad Gang
Main Boards => The Bowyer's Bench => Topic started by: cobbow on March 04, 2010, 01:24:00 PM
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I have been wondering about the orientation of the grain in the riser section of a laminated bow.
I know for strength in a solid riser the grain should run from back to belly.
What about in a footed or laminated riser?
Is it necessary to orient the grain the same way or dose the laminating of the riser add enough strength for this not to matter?
The reason I ask is the availability of large enough stock (with proper grain orientation) to do this with.
Thank You for any help yall can give.
)))Sorry I ment the cross grain of the wood((((
Cobbow
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You want the grain to run from fade to fade and the groth ring orientation to be from back to front as best you can get it for solid risers. I have only seen laminated risers with the glue lines running from back to front and because it is essentially plywood the grain is random. I have seen some I beam risers with the groth rings side to side for cosmetics. It would depend mostly on the poundage of the bow, the handle shape and and the corners of the shelf as to whether turning the groth ring orientation side to side will cause harm. I would err on the side of caution because of the time it takes to build these things.
In short, I would always have the grain run fade to fade and definately laminate the riser with glass or phenolic if the groth rings have to be oriented side to side too much. Quarter sawn lumber would be OK as long as the corner of your shelf where it meets the handle doesn't fall smack dab in the middle of a groth ring. Sand the corners off (inside and outside corners), sharp corners cause concentration of stress in those areas. Type of wood makes a difference too. Walnut risers will crack easier than most for example.
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this is the "back" side of a shedua LB riser, I thought the grain looked good, almost straight..I'm gonna finish ths one by next weekend. the riser came from the block on the left, both have straight grain,I will get 6 risers from the 2" x 6" x 60" board.. (http://i596.photobucket.com/albums/tt46/Robertfishes/2ndlongbowriser4.jpg) (http://i596.photobucket.com/albums/tt46/Robertfishes/2sheduariserblocks2-1.jpg)
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Thanks guys
After rereading my post I worded that wrong. I did mean the groth rings not grain and I dont know where cross grain came from. :confused:
Dont know what I was thinking.
So even on a footed or laminated riser yall have the groth rings running form back to belly as often as possible.
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For the two riser stocks Robertfishes shows above, the one on left is more suitable than the one on the right. But the one on the right (quarter sawn) is fine as long as the layout of the shelf to handle area on the belly, that inside radius corner where the feathers slide through, doesn't segregate whole groth rings to themselves. I don't know how to word that better. Even if it did there may not be a problem especially if there are laminate strips incorperated in the riser. Continuous glass backing helps a lot too. If you were to use the one on the right in a take down bow with a pistol grip you should incorperate many phenolic strips or avoid it totally.
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Jason, I am still learning and I did put glass in the riser block on the left and while I had the saw and jig set up I cut the one on the right too. I would like to have a nice solid dependable riser, all the bows I build will be 45- 50 lbs @ 28 in draw.