Do I Back It?

[mmattockx]

The bow is a 65" pyramid design from a hard maple board, 40lb@28". The story is this bow was completed with a backing of fabric/TBIII on it. It was tillered and shot 60-70 times. Shot fine. I then heated some reflex into it as a final step. The wood was not heated enough to do any heat treating, just to hold the reflex. Unfortunately, enough heat got under the limb while on the form to scorch some of the fabric and glue of the backing.

It was too much to leave so I sanded off the backing and am now at the point where I have to decide if I re-back it or just leave it. When I started the bow I was on the fence about backing because the grain was pretty good but there was a pin knot in the upper limb, so I chickened out and backed it. Now that I am basically back at the beginning I am less certain it needs a backing, but that pin knot still concerns me.

So I figured I would post some pics and let the experienced eyes here have a look and throw out an opinion. The light was pretty poor today, but I got the best shots I could of the grain and the knot for your viewing entertainment. The brownish patches on the limbs are where the backing glue is still in the pores of the wood and I have not sanded it all off. If you click on the pictures you will get a much larger version for a better look.

The lower limb:





The upper limb:





The knot:





So, my question to all the experts here is, should I back it again or leave it alone?


Thanks,
Mark

[Selfbowman]

 Never used maple but if it was Osage and looked like that it would not get a back. If it did get a back it would be horn or bamboo. Arvin

[willie]

I am curious about the grain orientation and how close to vertical or horizontal it is.
 

[mmattockx]

I am curious about the grain orientation and how close to vertical or horizontal it is.

It's bias cut, maybe 35-40 degrees off vertical (IIRC). I forgot to mention that the knot does make it through to the belly, but it is just a blemish in the grain on that side with no visible core of any sort. Before I backed it I wicked some CA into the knot if that matters. It is as sealed up as I can make it.


Mark

[mmattockx]

Never used maple but if it was Osage and looked like that it would not get a back. If it did get a back it would be horn or bamboo. Arvin

I managed to miss responding to this earlier. While maple certainly isn't osage in its properties, it is a good tension wood that mostly falls down on the compression side of things. One vote for backing it with air, then.

I suppose there is a third option of just adding a patch over the knot area itself and leaving the rest of it alone. Any takers on that?


Mark

[George Tsoukalas]

Yes, back it because of the pin knot. Jawge

[Pat B]

I go along with George.

[DuBois]

Never used maple but if it was Osage and looked like that it would not get a back. If it did get a back it would be horn or bamboo. Arvin

I don't think horn would work for backing but I hear boo is good. Never done a board but George and Pat vote back-
I would back.

[George Tsoukalas]

I never used horn or bamboo for a backing. Jawge

[scp]

I don't have much experience with pin knots in a Maple board, but the pin knot looks too small to be concerned, especially for a 40 pounder. I would rather drill it out than backing the bow for it. How wide and thick is the limb around it?

[DC]

I think I would rather leave it and hope there were no violated fibres rather than drill it out and know there were violated fibres.

[Pat B]

There are many backing materials from wood and bamboo to silk, linen, rawhide, I think George uses burlap and others, even brown grocery bag paper. Most of these cloth and paper backings will not prevent a problem bow from breaking but it will help hold down splinters and is pretty good insurance.

[willie]

I don't have much experience with pin knots in a Maple board, but the pin knot looks too small to be concerned, especially for a 40 pounder. I would rather drill it out than backing the bow for it.

Hmm, one way to stop a crack from growing longer is to drill a hole in the end. But the concern here is just on the back surface.

On the other hand, dishing out the face of the pin knot and filling the dish with a flush patch of some sort might be worth considering. The patch might need to be stronger than the maple though,... It might take an engineer to decide if that idea has any merit.

[mmattockx]

Yes, back it because of the pin knot. Jawge

OK. Now what about a patch over just the knot area?

How wide and thick is the limb around it?

Width would be a touch under 2" at that point, thickness is 0.385" or so.

On the other hand, dishing out the face of the pin knot and filling the dish with a flush patch of some sort might be worth considering. The patch might need to be stronger than the maple though,... It might take an engineer to decide if that idea has any merit.

You are an evil man. 


Mark

[George Tsoukalas]

Mark, I never tried that. All I know is I had a hickory board break at a  pin knot. It was tiny and I missed it when I bought the board.
Jawge