Wedge

[DC]

Has anyone glued a wedge in the end of a billet instead of using a riser block? I'm mostly concerned about a weak spot at the end of the wedge. I glued this experiment up. It's an OS billet with a chunk of fir for a wedge. I just used wood glue. I grabbed it in the vise and gave a good reef on it. I gave a bit of a crackle on the first pull but was fine after that. Hopefully it was just a bit of bark or something. It won't be used for a bow anyway. With contrasting wood it could look OK. I might cut the kerf a little closer to the back or maybe start close to the back and slope it toward the belly so that the end of the wedge is close to the neutral zone. Ideas? Comments?

[sleek]

I love the idea, but I'm concerned about splitting on osage, maybe if you got it hot first?

[Sagebrush]

I love the idea, you would just have to feather it in really thin?  I think you should try it with a hard wood.  Fir vs OS outside of the neutral plane might not be a fair fight.  Keep up the good work sir!!!

[simk]

DC, I can remember a bow built like that and posted here. should be possible... cheers

[DC]

I love the idea, but I'm concerned about splitting on osage, maybe if you got it hot first?

I put a C clamp on the limb right at the end of the kerf to stop it from splitting there. That works well. I tried kerfing and then steaming a piece of OS but the back part cupped quite dramatically and then I couldn't clamp it together without it splitting lengthwise.

I love the idea, you would just have to feather it in really thin?  I think you should try it with a hard wood.  Fir vs OS outside of the neutral plane might not be a fair fight.  Keep up the good work sir!!!

You only have to feather it out to the thickness of the kerf. In my case about 1/32"(1mm) thick. It may be better if you could feather it like a power lam but I haven't figured out how to get the kerf tapered to nothing. The fir insert was just a test on the end of a long OS billet. it will be firewood.

DC, I can remember a bow built like that and posted here. should be possible... cheers

I don't doubt that. I don't think anything is new in archery



I epoxied one last night. I used a Black Walnut insert in an OS billet. After I finish my coffee I'll unclamp it, clean it up and post it. The other thing that is bothering me(beside breaking at the end of the kerf) is where to position the end of the kerf between the belly and the back so that after tillering there is still enough belly wood left. On this one I put it about 3/8" from the back.

[Pat B]

If that is in a working area of a limb I'd be concerned it wouldn't be able to handle the stress of bending.

[DC]

Yeah, that. I made mine 8" long which puts it about 2-2 1/2" outside the fade. Right in the highest stress area. If I made it any shorter I couldn't get any appreciable thickness gain in the fades where I want it. Because the joint is so long and the stress will just be on the last couple of inches I'm hoping it will hold together. Just for speculation what do you think would happen if the glue let go on the last inch or so. Everything would still be held in place. I guess it would be like a grain delamination. We'll see. This is a fairly long term project so don't hold your breath

[Jim Davis]

If the kerf is in the middle it won't break there. If the back and belly are proper material, the core could be a line of blocks glued end to end and it would work. All force on the neutral plane is shear.

[DC]

I put the kerf closer to the back so I have enough belly wood for tillering. Kind of an educated(primary school) guess. It would be similar to putting a power lam under a bamboo back sorta. I'll show you in a bit.

[mmattockx]

If the kerf is in the middle it won't break there. If the back and belly are proper material, the core could be a line of blocks glued end to end and it would work. All force on the neutral plane is shear.

+1. The vast majority of the bending moment is dealt with in the outer skin of the belly and back. The core is simply holding the outer surfaces in shape while they carry the loads. The only thing I can see that may be a problem is cracking along the grain that starts at the end of the wedge.


Mark

[DC]

Here it is cleaned up a bit. It would look better if the insert followed the flow of the limb but this will tell me if it will live . I put the other bow in there just so you can see where things will be. It's handle is quite deep. I'll might have to glue a bit of riser on there but it will be out of danger of popping off.

[bownarra]

Have a look at a few glass bows
That is basically how I make all my glass designs. It definitely won't fail. Ideally you want the 'riser' in the middle of the limbs thickness.
Are you planning on having the handle made entirely out of the center piece or are you going to use something to join the two backs? Two self limbs spliced on? If you went with a boo back and a couple of cores with a belly (for the limbs) you could 'work out' your design more easily.

[DC]

I'll cut the splice into the fat end you see in the picture. Natural back and belly. So a self bow with an insert and a leather handle to cover all the crap I just glued up the other limb. Maybe splice it tomorrow then Tuesday we'll see how it looks.

[sleek]

This has given me an idea for tips too...

[Rākau]

I think this is a really neat idea, hope it works out.