How well do belly knots take compression?

[David Long]

I am in the habit of making sapling bows, and frequently knots on the bellies don't penetrate to the backs- so no problem with tension failures there. But what about the compression strength of a knot, say one the size of a quarter that comes straight out of the midline- you see the round end grain of the branch. Does this in your experience hold up well, create a stiff spot, or what? Those brown one-eyed monsters are not my friends. Dave

[Hillbilly]

Just depends on the knot. Some cause no problems, some will crack, chrysal, or refuse to bend. they seem to be a given in wooden bows, though-I've not seen many staves without a belly knot somewhere in it.

[JackCrafty]

I've never had problems with belly knots......but I haven't made a bow with knots larger than 1/4" diameter.  In any case, large knots are rare in straight wood, especially in saplings.

Knots are harder than the adjacent wood, so a large knot will create a flat spot when tillering the bow.  I guess you could just make that area thinner, but I think it would become a problem down the road because the wood around the knot will be under great stress.

[Keenan]

 Allot depends on the type of wood and where the knot is in relation to the limb.A knot mid limb will take much more stress and be harder to deal with the elswhere. I you have enough length when cutting a stave that is always something to consider.

[YewArcher]

Some pics of your stave would be helpfull.

Another thing to keep in mind when working on staves with allot of knot: If it does not bend through the knot it will not have any effect really on the knot. You will not get a 100% perfect full draw shot or 100% beautiful brace height shot but then again not every stave can produce those results. It is ok if you have some flat spots around large knots or knots that you are leary of. The tiller police may try and bust you but that is ok, they are usually disarmed when the realise the knot placement.

Another option is to wrap them.

Here are a few extreme examples of the knots I think you are talking about:


That bow is a tad stiff through the area but not to bad. It has been shot a ton with no compression cracks. Osage is osage though.

Steve

[YewArcher]

By the way, here is the full draw of that bow. You can see where the bottom limb is a bit stiff right outside of the fade: This is to minimize bend through that knot cluster.

[David Long]

Thanks you guys. OK, here is the stave. It is a piece of reaction wood yew-the bottom half or compression side. It is 49" long, 1 3/4 " wide and has a little less than three inches or reflex as you can see. I am very fond of this piece of wood, and if I can learn how to deal with this reaction wood I can collect some really good stuff locally. My plan is to bend up the very ends a la YewArcher or similar procedure and then sinew a flat back. Any advice on getting this to work out is helpful. You can see the knots-the lunker is a couple inches past the handle in the area of the fades. Generally I am shooting for a Northern California type flatbow thingy of the kind Allely is fond of. But I suppose I have to listen to the wood here first. Dave



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[David Long]

Forgot to mention it is all heartwood (you can see some sapwood I left around the big knot), and I have not bothered to following rings with this. Dave

[JackCrafty]

David, honestly, if it were me I wouldn't spend any more time on this one.  The chances of a failure at the large knot are too great.  Does that knot go all the way through from back to belly?  If it does, then you'll need quite a bit of sinew over that area (about 1/4" thick).

[David Long]

The knot does not appear on the back because that is essentially the center of the sapling. It doesn't look like it will fail in tension, but who knows. It's a big knot, and it's in a bad place for sure. Dave

[YewArcher]

Ohhhh.....Its Yew we are talking about! Great. I think you can do it. have you made many sucsessfull bows yet?

Sinew the back and you will be all set. I love pics as they tell 1000 words. Soooo.......here are some similar to your knots and the bows hold together just fine. That second bow down has a pretty substatial knot. The thing that you have going for you is the widt and shallowness of a bow of this style helps spred the starin around the knot.



Yew has amazing properties of holding together. Couple that with a sinew back at that bow will be fine.


i would not worry to much that it is compression wood. Leave the good stuff for the ELB and War bow guys.....what you are really making is a sinew bow that has a yew base. I will betcha that with carefull tillering and not overdrawing that bow can retain much of its reflex.

Steve

[YewArcher]

Ohhh....forgot to mention that thats just my thoughts. If that stave was here I would make it int a bow without hesitation. I think you will get allot of thoughts on this one.

[Keenan]

David, Yewarchers advice is good and you can probably pull it off if your carefull. Yew is tuff and will take allot of abuse but as I zoomed in on the knot I noticed some fairly serious ring violations. Though it's not necessary to chase a ring on yew it can be deadly to have sharp violations around a knot.  This is because around that knot the grain tends to role up towards the back of the bow and if you just rasp it flat you cut through exposing the ring at a sharp vertical angle. (Deadly)
  If you still have plenty of wood on the belly I would suggest working down the back a few rings to help remove some of the sharp violations on the knot. Then sinew a little extra heavy at that place.
  Also if you are going to flip the tips you will want to do that before sinew, witch you probably already know.

[David Long]

Maybe I should have pointed out that the pic showing the knots is the BELLY side. I have essentially cut down the middle of the sapling and so the bow will be backwards like a Holmegaard. Seen from the back, the knots are not very apparent and you are looking at the rings end on. I cut the curved sapling this way so that the bow would be made from the lower compression side, thinking this would be stronger. Oriented this way I can use the natural reflex. I hope this is clear. Dave

[Hillbilly]

I would soak those knots down with thin superglue, and sinew the back. I'm looking forward to seeing how this one turns out-I think you'll be ok.