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Hairline cracks when heat/steam bending?

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superdav95:

--- Quote from: Marin on January 24, 2023, 02:06:56 am ---As to the cracks on the back, the small one has reappeared. I had tried to scrap it off before (it was shallow and I am backing this bow) so I know it doesn't go that deep but I don't reallt want to shave the back in one spot. I am however cautious that when I back this the crack will only grow as it would be under similar stresses to what caused the crack in the first place, and with this crack being not in the center, I am a little worried. Would just filling it in with hide glue and putting an extra strip of sinew be enough caution, on top of the 3 or so layers of sinew I'll be covering it with?
PS Don't be too alarmed at the violated grain in the photo. This was very very tight grained juniper to begin with s9 wyat seems like a major divot is actually barely noticeble when feeling the bow back.

--- End quote ---

That’s what I would do.  If it’s a good piece otherwise I’d say go ahead.  In such cases as these minor hairline cracks if filled in with lots of layers of thin hide glue to prep for sinew is a very good preventive measure as the glue wicks down into the pours of the woods and strengthens it along with the added sinew.  If done right it essentially becomes one piece.  Proper sizing of surface would be your friend here for really good adhesion.  Best of luck with it

Pappy:
Is the checks you are talking about the 2 lines i see in between the 2 pencil marks ? if so yes i would be worried about them. Heat or steaming checks usually run with the limb not across it. Maybe I am looking at the wrong checks  :-\
 Pappy

Marin:
Yeah sorry those aren't checks but due to the bad photo they do look like it. Those are tool marks from my scraper, they just look like cracks in this bad line. The tiny hairline crack is the sort of black line that runs through these two scraper marks. That's why the scraper marks are there actually

Pat B:
Checks or drying cracks occur when wood with moisture in it dries a bit too quickly. They generally are only a cosmetic problem. You can fill the checks with thin super glue which will usually seal them and keep them from getting larger.
 Checks run with the grain, cracks run otherwise, across, diagonally, etc. Correct terminology generally helps with the diagnosis and remedy.

Marin:
But that's the thing. These aren't drying checks, at least not in the way I usually see checks. I initially said in the first post of this thread that they only appeared very very recently and specifcally when I was using heat to straigten this area. They have not appearend anywhere else, and this wood was cut back in october and has spent quite a bit of time at this thickness and dimension before these cracks appear. I don't think they have to do with drying, as the wood is completly dry by now.
And I have heard the term "cracks" applied to lengthwise cracks before, like with cracks that form in the belly of sinew backed bows. I don't think people call those "belly checks" because those weren't formed from the drying of the wood but from different types of stresses the wood is undergoing as the sinew dries.
Unless this juniper somehow has been retaining a lot of moisture after over two months of drying close to finished dimensions, I'm not really sure how moisture of the wood caused it. Unless juniper retains moisture really really well, but I haven't heard anything about that.

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