compression fracture?

[MikaelMazz]

There is a very small compression fracture(I think) near a knot on the belly of a bow I am making. It runs horizontal when the bow is standing up.
Is it neccecery to repaiar this? And if so how would I do that. I would prefer the use of only natural material like sinew.
Thanks,
    Mikael

[Marc St Louis]

Compression fractures run across a limb

[PatM]

 It can be quite common for that to happen where the grain direction changes around a knot. Those ones tend to not run all the way across. If it is just a tiny 'pinch', I would just keep an eye on it. It won't be taking much wood out of action if it is restricted in size.
 Let us know the cross section shape and limb width and length.
 Sinew or other wrapping will just hide it. You would need to remove the area and replace it with sound wood to really say that it is fixed.There are ways of doing that though.

[DanaM]

Also take a look at Gordons Hazelnut build along, in it he repairs a fret with rawhide.
Best of luck.

[MikaelMazz]

It is an eastern woodland bow of hickory. The bow is 1 inch its hole length and 68 inches over all. It has a rectengular cross-section. The crack is about 4 inches from the tip if that matters. This area shold not bend a lot once I am done tillering it. I am giving it a D style tiller with slittly stif tips.
Thanks alot for tthe replies.
          Mikael

[Brokestick]

I saw an article on this type of repair, but I can't remember what issue.  The author used a sanding drum, and a hole saw with matching outsid and inside diameters, that is, the sanding drum would fit perfectly inside the hole saw.  He used the sanding drum to remove the bad section, and then used the hole saw to cut a matching plug to replace the wood removed from the bow.  The grain direction of the patch was set so it could be neatly chiseled off and sanded smooth, and the patch set with epoxy or urac.  It's been a few years since I read it, so I might not have all the details correct.  Good luck.

Julian

[PatM]

 I am very skeptical that you are doing much for the fracture by gluing rawhide over it. Rawhide isn't  a compression material. i think it's more an 'out of sight out of mind' treatment.  You wouldn't glue a rawhide belly on a bow.
 It would make more sense to glue a sliver of thin horn on the area.

[Gordon]

I am very skeptical that you are doing much for the fracture by gluing rawhide over it. Rawhide isn't  a compression material. i think it's more an 'out of sight out of mind' treatment.  You wouldn't glue a rawhide belly on a bow. It would make more sense to glue a sliver of thin horn on the area.

If John Strunk uses the technique that's good enough for me. I used it on a bamboo backed yew that had a bad fracture that clicked every time the limbs were flexed. I applied the patch and have never had a problem since -  and I shoot the bow a lot. That said, I think horn would be a very good way to fix the problem as it is very resistant to compression.

[Badger]

Gordon, did you just glue rawhide directly over the fret? There may be more to it than what meets the eye but I can't imagine how rawhide could have any affect at all on a fret, maybe the hide glue that is saturating the rawhide is holding some compression? Steve

[Gordon]

John Strunk does wrap the rawhide tightly with thread after it is applied to the fret - I'm not sure if that makes any difference.  I can't imagine that the glue itself has any particular benefit. I have used the technique a couple of times and in the case of the yew bow I'm fairly certain the limb would have failed had something not been done. I am using pretty thick rawhide - not the stuff you back with.

I don't know, it seems to work.  But perhaps an experiment to prove or disprove the effectiveness of the treatment is in order.

[AndrewS]

I think it is importend, that Gordon use superglue / superglue-gel to fix the rawhide.

[DanaM]

Brokestick the article was a few years ago and it was by Dean Torges.

[Marc St Louis]

I also don't think that rawhide would be of much value as a compression material. Scraping the limb down past the fret and gluing a thin strip of matching wood would work

[George Tsoukalas]

There are 2 causes of these infernal happenings. Improper tiller(localized in one area of the limb)  and bad design (pretty much the whole length of the limb). To fix tillers I've had some luck using thick pieces of birch bark. Rawhide would work too. Works when  compression fractures are caused because the limb is bending too much in that area in relation to the rest of the limb. I believe the reason the above fixes work is they keep the limb from bending too much in that area. The other case of a compression fracture is improper design. Not enough wood around a knot that is on the belly of the bow for example-that is not leaving it a little wider. Fractures that occur along most of the limb's length mean the bow is too short or too narrow. I hate compression fractures.  Most of the time I just retiller as Marc stated.  Gotta leave the fractured area alone and retiller the other limb too. Bow goes in the rafters. I won't hunt with or shoot a fractured bow. I just make another. Getting tired. Sorry for the rambling. Good night.  Jawge

[Badger]

Jawge, I am like you once I see a compression fracture I just loose interest in the bow, in rare cases I will rework the bow. This past year I have tried to push the design a bit more than in the past and probably lost 50% of all the bows I made last year to compression fractures. My heart sinks every time I see one. Steve