Tension Weak Wood

[Marc St Louis]

I harvested this wood in Ottawa last year and decided to make a bow out of some of it a couple weeks ago.  The wood I cut was Buckthorn and it is an extremely elastic wood in compression.  The stave I selected was a pretty clean piece except for a small scar which I decided to place on the top limb.  I flipped the tips and used dry heat to straighten out some deflexed areas which added a bit of reflex and started tillering, I elected to go with a shallow D section belly  Got it up to 24" where it was pulling 50# and the tillered shape was good.



I kept going but when I pulled it to 26" it went bang.  You can see from the pics that this is a classic tension failure with both limbs breaking at almost the exacts same spot.





I like this wood but I don't think I'll try another selfbow

[upstatenybowyer]

I'm really surprised it blew like that. The bend in that first shot looks really really good. And shallow D section limbs should have taken some stress of the back if I remember correctly.

[gfugal]

That is a crazy break. It says something about your tiller that it broke in the same spot on both limbs. Well balanced.

[bradsmith2010]

well executed explosion,,

[DC]

" it is an extremely elastic wood in compression."
Does this mean it is a good candidate for a backing like bamboo? We have a ton of straight Cascara which is a Buckthorn.

[PatM]

" it is an extremely elastic wood in compression."
Does this mean it is a good candidate for a backing like bamboo? We have a ton of straight Cascara which is a Buckthorn.

 Seems more like a sinew candidate.

[BowEd]

Both limbs about 8 " out from the handle?

[Bryce]

I've made a few buckthorne bows. In fact it's one of my top 5 favorite bow woods Bc it's so elastic. I've never had one break like that. Actually I do t any have broken. I think it just must have been a bad piece. Very odd for that species imo

[George Tsoukalas]

Sorry, Marc. Just out of curiosity what was the length of the stave? Jawge

[Marc St Louis]

With the RH sitting around 70% all Summer it certainly didn't break because it was too dry.

I don't know if it would do well with Bamboo, probably.  I've got  deflex recurve glued up with a Maple backing that I have been waiting to tiller out, decided to do this bow first.  It would probably do well with sinew also.

Both limbs blew around 8~10 inches from the fades.

Actually this is not the first Buckthorn bow that broke on me, usually it's just a splinter lifting.  The MOR for the wood is extremely low compared to tension strong wood

The bow was 65" long with the limbs just under 1 1/2" wide

The wood may do better as a selfbow with a narrower profile and a deeper D section limbs

[George Tsoukalas]

Looks like  plenty of length and width, the stave is bending through the fades and the recurved tips are bending a bit.
Since I tiller with hand tools, most of my bows end up with a slightly rounded, almost imperceptibly so, belly.
Looks like you did everything right.
That's the way it goes.
Thanks for sharing that even great bowyers can have a break.
Jawge

[Badger]

  The tiller looked right on, had the bow taken any set prior to breaking? Do you have any idea what the mass of that bow was? I know bows that are very elastic in compression can usually carry less mass than most other woods.

[George Tsoukalas]

For what it is worth, Marc, I went through a stage where I liked to try a variety of bow woods (elm, hickory, osage,, yew, red and whit oak, hop hornbeam, maple, ash, lemonwood, Australian pine, poplar,  American hornbeam, sassafras and some I can't remember).

No longer but it has been fun.

Now, I use black locust, and the oaks (red and white) for backyard woods.

Hickory and osage are my favorites when I can get them.

I've broken more than my share.

I'm done experimenting. At 69 y/o I stick with my tried and true.

Sorry for the rambling. Must be my age. LOL.

Jawge

[hoosierf]

I built a sinew backed buckthorn from a sapling and it does make a nice bow. But its tension strength is about half of the typical white woods while its compression strength is about typical of white woods. So, I've sort of decided that it needs a backing to be safe over the long haul. I know others have been successful without but I think it's risky.

Respect to the real masters tha post here, Hoosier.

[Marc St Louis]

Buckthorn is a small diameter tree so anything you cut will have a fairly high crown.  This concentrates more tension stress in a small strip down the center.  Some species shine with having a high crown especially Elm.  Many Elm have about the same density as Buckthorn yet almost double the MOR.

I went through the same stage many years ago George but I'm not calling it quits yet.  New species rekindles the flame.

Sorry Steve but I didn't weigh it.  It did seem fairly light in the hand.

I have a number of nice billets left but my source has been bulldozed over  which is curious since the whole area is being claimed by the Algonquins