core wood

You want to be using the sapwood of acer saccharum. In fact it's hard to even find maple heartwood. Really you want wood from a young tree as it's way more likely to be flexible enough to be bent into a suitable core shape. Older wood loses flexibility and unless you cut it yourself is very likely to be kiln dried - both of these things preclude it's use as a hornbow core. The same applies for birch and soft maple is a little too soft!
Grain matters hugely - you won't even get a core bent to shape if the grain isn't perfect (certainly for a three piece core).
The best adviceis to cut your own green maple, reduce to core lathe dimensions and get it steamed/boiled asap after cutting.
Green, young wood is what you want.
I strongly recommend buying Adam's book on Turkish bows - it has everything you need to know in it. Without that book I wouldn't have stood a chance of making a working hornbow!

reduce to core lathe dimensions and get it steamed/boiled asap after cutting.

Hi, it's interesting. Because i everytime reduce dimension after drying wood for slow drying.
Is there some rules to prevent cracking of wood by fast drying?
Sorry for my english, i hope you understand:)

The pieces are cut oversize and overlength. The moisture content is needed to make the wood flexible enough to be able to be steam bent into shape.

after steam bending, while the wood was still dried to form i smear edges with glue joinery. with this practice I never had cracking.

Sugar Maple isn't the only that can be used.There are many other woods that have been used for composite bows. Birch was used quite regularly too, as was Mulberry. Adam Karpowicz suggests using sugar maple but is by no means adamant about it's use.

You could argue that Sugar Maple was never used as a core since it's a North American species.
I believe Cornel was used as a core as well. Somebody once posted cut cross sections of a bow made at least partly with a Cornel core.

Pat Menzies wrote:

You could argue that Sugar Maple was never used as a core since it's a North American species.
I believe Cornel was used as a core as well. Somebody once posted cut cross sections of a bow made at least partly with a Cornel core.

Cornel for bow wood?
Well I never had a piece with a large enough diametre for bows, but the red cornel is quite fine for arrows - and quite easy to straighten as well (during the drying process most of the shafts can become nearly straight if you are diligent).

Actually, I was just checking the properties of yellow birch and it appears that it might just be better than sugar maple for this type of bow making. Check this data base and compare the two woods for yourself. http://www.wood-database.com

Tapsnap wrote:

Actually, I was just checking the properties of yellow birch and it appears that it might just be better than sugar maple for this type of bow making. Check this data base and compare the two woods for yourself. http://www.wood-database.com

In practice unfortunately Yellow Birch doesn't seem to reliably stack up to its listed numbers.
I have cut several pieces and it is quite similar in general properties but it does not seem as hard or as compression resistant or elastic.
I once lightly floor tillered a Yellow Birch stave and it chrysaled immediately.
While it seems usable as a core material I wouldn't go so far as to call it better.

That's a pity. What do you mean by "chrysaled"?

It's a term to describe a section where compression failure causes a "pinched" area running across the limb.
It looks like a faint scratch and there can be just one or dozens of them.

So this pinching is caused by a failure to withstand compression. Can this be compensated for by using thicker horn to wood ratio and perhaps less sinew?

I was just showing that the wood may not be all it is said to be. Undoubtedly it would work just fine as a core but not better. I would imagine that if you can get your hands on Yellow Birch, you can just as easily get Maple.

I think one of the biggest disadvantages to birch is that it does not respond to heat bending as well as maple. This might be a problem when tuning and correcting the bow with heat during the tillering stage.