Can anyone tell me how... Korean Bow?

Bambo is naturally one tough bastard of a material. Even with the outermost portion of the skin scraped off, you still have the very dense mass of fibers immediately underneath the skin to serve as some sort of belly material if you're making something out of plain bamboo. If you're building a composite, though, then the strength of the bamboo itself wouldn't matter all that much because the horn and the sinew should be taking most of the stress--the bamboo just has to be strong enough to hold everything together.

As for belly materials other than horn, bamboo is one possible alternative. It has been discussed in a recent thread:

http://198.170.107.188/phpBB2/viewtopic.php?t=1111

and there's an older (but successful) attempt shown in the main ATARN site:

http://www.atarn.org/FAQ/bamboo_composite.htm

What you are saying about the horn and sinew doing most of the work makes perfect sense.

Now let me tell you about an experience I had. I made a sinew backed bow on ash which came from a furniture supply. I picked through many boards to find one with ideal grain. The bow was perfect, strong and reliable.

Then I made a horn bow with a core from the exact same board. In fact even the design, proportions and length were almost identical. That hornbow broke the core in five places without affecting either the sinew or horn.

I soaked the bow apart. I retrieved the undamaged horn and the core pieces.

Now I have been a wood worker for almost 40 years and the ash core had breaks which I have never seen before on solid wood. The breaks were like cracking mud, there was no splintering. I can only assume that the other two layers supported the wood completely while immense stresses tore or stretched it apart.

This was the second hornbow I have lost on an Ash core. You might imagine that I will never do this again.

Reservedly I mention that others have been successful with Ash cores. But I am of the opinion that every element of a hornbow contributes. There is nothing that does not matter.

What one makes the core out of is critical, traditional techniques will save much effort. Bamboo is a time honored core material. -j-

You used Ash board, we use small dia trees. Bamboo does not grow here so we take what we have. Elm I will not try any more.
Thin Ash strips feel unbreakable.

I should also say that the second failed ash core was made from an air dried bow stave from the same tree which made excellent long bows.

I also don't have bamboo for cores; I have had no problems with maple but also want to try cherry. Plum looks good but I am a bit reserved.

I suspect that bamboo for cores is not a premier choice; more a matter of availability. -j-

Bede Dwyer's (?) recent presentation on Chinese bowyery practices actually placed bamboo at the bottom of the list of materials to be preferred for bow cores, though the fact that it's still included in the list might say something. In any case, bamboo is so widely available at such low prices in East/Southeast Asia that I can't help using it for a lot of things, whether archery-related or not; bowyers back then probably felt much the same about the material.

I am sorry, but I don't remember doing a presentation on Chinese archery practice.

I have always enjoyed dissecting failed bows and draw conclusions - I find it very educational.

Jack, since you used the same wood, amd the degree of bending was similar (as you say both bows were similar in bending characteristics), the wood of the horn bow could not be subjected to much greater strains, especially so when hidden under the sinew and horn. The failure was in tension, which means the wood of the horn bow was more brittle for some reason. Is it possible the horn bow during construction was subjected to heat to dry the components faster? Perhaps a blow gun was used to dry the glue at some stage or the drying was accelerated in a hot box? Was the glue coating the core in preparation for horn or sinew dried at an elevated temperature? Is it possible you made (or finished) the horn bow in the ambient humidity lower than the selfbow (during the heating season)?

All this would make the wood of the horn bow more brittle and could make it fail onder the tensile forces when bent.

In any case, I do not like to use ring-porous woods (ash, elm or oak) for horn bows. It is because the porous spring growth makes the absorbtion of glue uneven, and the cutting of grooves more difficult. For that reason I recommend diffuse-porous woods, such as maple.

Adam

Adam; I am speaking here about Egyptian angular bows of the King Tut type.

The core consists of two layers of wood with the riser, if you will, sandwiched between; all steam bent to a form. The surfaces were well scored with a hack saw blade but no grooving as such.

Pearl glue with a small addition of fish glue was air dried with only a small warming before applying the Ibex horn. Elk leg sinew with pearl glue was allowed to dry for months in the horn version; weeks in the backed version.

The owner of the backed bow draws his bow significantly further than I drew the horn version.

The horn bow only broke on the back core layer, the belly core layer untouched.

I still prefer ash for backed bows, even and especially for short horse bows of the Plains Indian type.

Bede wrote:

I am sorry, but I don't remember doing a presentation on Chinese archery practice.

So I was right in doubting the accuracy of my own memory with that question mark . :(

It's one of the presentations linked to in a recent post on the ATARN forums. I haven't been able to find the post and the link, though.

Hyarmendacil, there is a link for the presentations;

http://www.turkisharchery.info/?p=!wtafpresentations

all the best

An interesting case. The cracks look like the usual brittle fracture on the tension side, normally found in over-stressed softwood. Hardwood can be made so brittle only with excessive heat or very low ambient humidity. I think you wrote before about drying the core of this bow with a heat gun after each applicationr of glue for the horn-core joinery to hasten drying. Such drying could potentially cause overdrying the wood. If this treatment was done on the sinew side as well, then the wood could be become really dry or "case hardened" on the surface. Perhaps the humidity in your shop was low when the horn bows was made too.

This type of heating also degrades the glue, but in this case it is wood at fault, since as you said the bond with the sinew layer was sufficient. I notice file marks on the wood as if "roughened". The safer way is to scrape parallel grooves under sinew, just as the grooving under the horn.

Adam

Adam; I use a regular fan to speed drying of horn application. Humidity is always relatively high here.

I know that in every wood type there is a large variance in wood density. One can feel this in the weight. Also this board was kiln dried. This usually means to about 10% or so. The moisture then rises again in the air to 20%. I do not think that the boards are heated excessively.

My theory is that in the backed version the plane of neutral resistance is buried in the middle somewhere, such that any good bow wood improves. When horn is applied, it is so dominating in compression that it throws the plane nearer to the back causing great tension to the core under the sinew.

In effect the horn makes the core also act under tension like the back.

I suppose this would not occur if one piled the sinew high, which I do not do because of the excessive work.

The maple or bamboo is dense enough to take this tension, possibly holding the plane of neutral resistance. But the Ash is light and does not act this way.

I hate to pick things apart on this level but these are my thoughts. -j-

Sinew balances horn in the composite construction very well. Bows in excess of 100lb, and very short (bent over a small radius) can have only 2mm of sinew with no trouble. The breaking strains in hardwood are similar for most wood species. I assume your bow was not nearly as stressed.

Maybe you underestimate the degree of bend in your (drawn) horn bow. But I would tend to believe something happened to your core wood between the first and the second bow.

A broken bow is an invitation to make the next...

Adam

Adam; Well what I am saying is that I made another identical bow with a maple core using the exact technique and the bow is quite reliable; I have been shooting it for 2 years now. Another with an improved curve awaits my attention.

A simplified explanation is that the maple can take it where the ash didn't.

Mc Leod wrote about these bows and quoted Carter's sources that two independent tests named ash as a core wood from samples from Tut's bow (s) (?). He also states that he cannot be sure that any of the bows is a hornbow but expects that some or most or all are.

My problem leads me to conclude that at least one of the bows, one from which a sample(s) was taken, may have been a backed bow. This theory cannot be corroborated from other damaged examples outside the Tut collection.

This theory also throws question onto the Aqhat saga translation where bow wood is discussed in ancient Canaan.

One challenge is to use only authentic materials and techniques; always a temptation to allow later, superior techniques to creep in. I am not resolved about the appropriateness of grooving over diagonal roughening for these bows.

One day my mentor will turn his attention from bronze age ships back to Biblical warfare.

Thanks for the advice, -j-