Core wood?

[JonW]

It seems that Maple is the core wood of choice. I don't really have access to Hard Maple. I would have to procure it from someone else. Probably not a big deal though. My question is what other types of wood would be tried if you were in my position. I have a lot of Sassafras that I was going to practice making cores with.

[Pat B]

I think mulberry was a traditional core wood.

[mikekeswick]

Mulberry was used for the tips not the bending limbs. It is ring porous.
You want a diffuse porous wood with great gluing properties,obviously great steam bending ability and less than 0.70s.g.........which = maple!
Also vitally important is that the grain is flawlessly straight, no pins,no wiggles and definitely no twist.
Other woods that I have used are european hornbeam and cherry prunus avium. the cherry was fine for a while but eventually the core broke. I have also used osage for a couple of 'mini' half scale Turkish bows (ring porous but it's osage!). I wouldn't recommend it for a proper bow though.
I have had such a hard time trying to get suitable core wood that I have started to grow tartarian maple (what the Turk's used) and will be growing them up pipes like forcing rhubarb.

[james parker]

actually, mulberry was used by the Chinese in certain bows for limbs, as was bamboo, Korean bows also use bamboo,
I personally have used those,and hickory also,, the first five Turkish bows I ever built I used hickory as a core and mulberry for the tips.. after inspecting a Chinese bow, the core was mulberry and the tips were of two different larger ring porous woods ,
 so I think (certain) larger ring porous wood can /has been used for larger horn bows . with the stresses spread out more evenly throughout the limb,,= larger bending radius, compared to the shorter bows with a much tighter bending radius=knee
mike is defiantly right about proper grain qualities and choice
note: I have dissected several ancient  broken  horn bows, a crab bow, a Turkish bow,  and a few others and broken bows of my own,, after looking at the most bending sections of the limbs a noticeable amount of wood breakdown was evident, I think the more the stresses and the more the bows were shot the more the amount of wood ( cell) breakdown in that area,all bows showed some breakdown to a degree +/-

[mikekeswick]

James - that's really interesting about the wood showing signs of breaking down in older bows.

[Limbit]

I second that, there are several videos I've seen showing Koreans using mulberry for a preferred core wood. My friend is from India and he said mulberry is the wood they used in horn composites as well, but he isn't an archer, so I am not sure he really knew or not.

[joachimM]

About the breakdown of the wood: is that actually a problem? or stated otherwise: isn't it inevitable?

If I quickly estimate the strain experienced by a Turkish bow core of 6 mm thick at the sal (the most bending portion) on the basis of a bending radius of a circle in the neutral plane of the core and at the outer surface of the core, you get nearly 2% of compression and tension strain.
No way any wood can stand this by itself. If it weren't backed with enough sinew, it would splinter. And if it weren't for the horn belly, it would buckle at the sal.
Even a core of 4 mm thick experiences 1.3% strain. (this site http://www.botondbow.com/ijkeszites actually suggests to use a 4-4.5 mm thick wood core, albeit for hungarian bows)

When a turkish bows breaks, (from what I have gathered) it seems regularly to be caused by a too thin sinew layer, that hence the neutral plane is not located in the middle (or closer to the back) of the core (but rather at the belly of the core), and that strain on the wood is nearly twice as high as expected. Since sinew and horn have nearly the same modulus of elasticity and strain resistance (in compression on the one hand, and tension on the other), so they should be equally thick at the sal.

Here's an example of a bow by Francesco Alessi picture here http://paleoplanet69529.yuku.com/topic/60068/Blue-Turkish-Bow#.VYfyhPm8PRY
Doing the same analysis on the strain at the belly surface and the back surface, you get (as expected) a strain of c. 5%

Joachim

[mikekeswick]

 Francesco Alessi - has made some truly stunning bows.
I have come to the conclusion that my first layer of sinew needs a thicker solution of glue. As you say the strains on the core are impressive and come too close to the edge if you don't get the ratio of back/core/belly correct and your sinewing perfect.
I've got a new round of hornbows in the works and i'm really going to be paying attention to the horn/wood/sinew ratios.

[crooketarrow]

  Back in the 90's I went throught the horn bow thing. Built 8 or 9 bows I used ,osage, pig nut, shag bark,hickory.elm, maple,mallberry. Only because thats what I had seasoning.

  Only advanage I saw was osage was easyer to heat and form.

  I remember showing CROOKETARROW horn bow I'd just finished. He looked it over with a bowyers eye,ran his fingers all along it.  He was a simple man and only made or used what was needed. The way he knew grew up, only haveing or makeing and useing what was practical.

 A horn bow was far out of his reailm as to my you'd need one. He made bows the same as the Iroqouis had for generations.

  It worked he saw do need to change it.

[mikekeswick]

I to a degree understand and agree with the 'if it ain't broke.....don't fix it' thing but if we stuck with that and never experimented with things we wouldn't have bows at all.....we can run down any animal on the planet if we put our minds to it!