study of the mechanical properties of AYC (updated with my SG and SBT results)

[Sempertiger]

I'm currently drying some Alaska Yellow Cedar in an attempt to make a bow out of it. While searching around for information on it, I discovered this study.

http://www.fpl.fs.fed.us/documnts/fplrp/fplrp565.pdf

It seems that the wood from trees that are standing dead for between 26 and 51 years, have enough better mechanical properties to target them, over live trees, as potential bow wood. the cool part about this is that you don't need a special permit to harvest standing dead trees. Now I just need my wood to dry so that I can start testing.

JS

[artcher1]

I have no idea whether it's bow material or not, but if it doesn't work for that, it makes one heck of an arrow!

[DRon knife]

you aren't interested in trying to make a birch bow?

[Sempertiger]

I don't have any birch near me. it's common up north, but extremely rare in SE AK, the little we have is a hybrid, and I'm not sure if it's any good... I'll harvest some if I find it, but i've never actually seen any.

[randman]

That looks like some good info there SemperTiger. Looks like there is an abundance of the dead stuff there. I'd be interested in knowing what you find out. Good thing about it is if you find some good dead stuff to use, it's already seasoned and ready to work.

[Jude]

I had really poor luck with the birch in Fairbanks.  Two bows in a row died of compression fractures when they hit 24" on the tillering board.  I was building them wide and long, and they still died on me.  Plus, the arcs looked perfect, and the crysals were up and down both limbs entirely.  Upon further research, I found that the Athabaskans made birch bows with string blocks to achieve brace height, so their bows were under no tension at brace.  I also discovered that paper birch has a large number of different sub-species with a wide range of different properties within the species.  New England paper birch are actually derived from a hybrid with yellow birch, and have a longer lifespan and stronger wood because of it.  I think the problem with the extreme northern trees may be tied to the extremely short and intense growing season.  Even though it is a ring diffuse wood, the rapid growth could give the wood a higher degree of early growth characteristics, making it lighter and less strong in compression than it's southern cousins.  That's just my guess, as I have no research to back it up, and all the birch I cut up there ended up in the campfire, so I can't weigh it against the stuff here in New York.  Enjoy Alaska; I'll make it back up there one of these days, if not by way of the Army then by way of retirement

[Sempertiger]

I think the way I'll do it with any  trees I find up here is to cut enough to make test pieces for 2 tests. I'ld do the standard bend test and specific gravity test as described in the TBB books. That would give me two reference points to colaborate against to figure out the dimensions of any designs I might like to try. I'll post what I find, once I find something to work with.

I'm thinking that since the more dense wood from conifers comes from trees with more grow rings per inch, then I'ld probably have my best luck starting at tree line and working my way down, till I find an appropriate size tree. I don't want to take a huge 100ft tall tree down. I'ld be very happy with anything 3-6" accross.

my two test sticks of AYC hit equalibrium yesterday, So I should have some Idea what I'm working with in a few hours.

JS

[Jude]

Found a couple examples of Athabaskan bows.  They made them from birch, willow or black spruce, depending on what they had.  Note the string block to catch the string before it slaps the wrist.

[Sempertiger]

AYC test results. my specific stick of AYC measured in with a specific gravity of .54

For those familiar with the standard bend test in TBBV1, I got the following average results
18.23lbs at 3.25" for 1/4" set
25.29lbs at 7" to break.

They all broke in compression resulting in wedges being ejected out of the belly of the bend.

Based on these results, I should make my limbs 2.43" wide to make a 50lbs 66"ntn bow.
since I want to make a 55lb bow, I'm going to make them 2.675" and 68" ntn.

Time to ruff out and let it set until it reaches equalibriam in my 40% humidity environment.

JS

[Sempertiger]

I've seen some of those in person. they are very short, and I think you are right, they aren't under tension while braced. the Athabaskan people lived north of me. I'm currently trying to find what materials the Tlingit people used for bows in my area. I've not been able to really locate any relyable information on what they used in the Northern reaches of their teritory.

other than wood aquired through trade, I've heard they used AYC and some extremely dense spruce and hemlock, but, again, I haven't found any hard evidence.

JS

[Jude]

I can't find anything on Tligit or Tsimshian bows either.  Apparently the Haida, further south, made short wide bows out of yew.

[Sempertiger]

Yea, the Haida teritory is the norther edge of Pacific Yew's natural Habitat. I don't think the Tligit would have traded with the Haida for it. From what I understand, from talking to an Older Haida and my research, they are mortal enemy's.

JS