Compression Fractures in Osage

[Scallorn]

  I just finished a 62 inch osage longbow loosely based on the powhatan bows in Allely and Hamms encyclopedia. It is a broad thin bow that draws 65# @ 26inches. The bow is very light and very fast. My only concerns are some compression fractures that have formed on the belly. The bow seems very low-stress by design and I dont understand why this happened. Are compression fractures enough to ruin a bow?

[bradsmith2010]

Pics would help,,,unbraced profile,,.full draw

[bownarra]

Yes they will only get worse over time.

[simson]

Can't believe these are compression frets with these stats. Have your bow a hinge?
Make some pics.

[bjrogg]

We need more information and or pictures. Are the compression fractures spread out over the length of the bow? Are they confined to a certain area?
Bjrogg

[Scallorn]

I'll throw some pictures up this afternoon. There are several of them spread out over several inches of one limb. There does not appear to be any hinges. I'll let yall be the judge though, because you might see a flaw that I dont. The width at mid-limb is 1.5 inches and the profile is very thin. I'm not any good at tillering, but I felt like this one was pretty good. The bow took almost no set and it's pretty much flat after relaxing.

[scp]

Did you heat treat the belly? How convex is the belly? How thin at mid-limb?

[Scallorn]

The belly is not significantly convex at all. I havent put a straight edge on it, but I tried to get it as flat as possible. Mid-limb is probably .5 inches or less I think. I'll double check in a minute, but I'm pretty sure it's close to that.

[bradsmith2010]

Ok since I am confined to just guessing
You probably damaged that area when u first braced the bow
Before u evened the tiller
Just guessing,,

[George Tsoukalas]

When they are localized to one spot that's indicative of a tiller problem but when they are spread out like you mentioned, that's indicative of a design problem....too short, too narrow, too heavy for the design etc.

How wide is it?


Tough to say without photos.

Jawge

[scp]

How heavy is the bow? Is the bow dry enough? How long are the compression fractures?

As it was said, it will just get worse. The statistics say it is almost over-built. I would stop pulling on the bow, sand out the chrysals to make the belly really flat unless making a replica, and heat treat the belly rather well. What is the intended draw weight?

[Pat B]

Don't destroy this bow. Later, when you are more experiences you can reduce the belly and add a lam of compression strong wood(like osage or ipe) and retiller the bow.

[Scallorn]

  So, the fractures ended up being very shallow. I used a cabinet scraper and some heavy grit sandpaper to get down past them and flatten the belly out. Re-tillered to 49# @ 26" and called it done. The bow is very thin and very light. It throws arrows with a lot of speed and minimal hand shock. I'll have pic's up soon so everyone can see it. Thank you all for the advice and critiques

[Pat B]

If you scraped the frets without reducing the rest of the limb(s) to be sure both limbs bend evenly and together you have made it worse. The fretted area was getting more stress than the rest of the limb so weakening it by scraping just exacerbates the initial problem. Please post pics so we can see where the frets were occurring in the limb so we can help you. 

[scp]

When people say to scrape off the chrysals, they usually mean to scrape the belly to make it bend more evenly but until all chrysals are gone. Hence the mantra, always use long even strokes as much as possible.