Main Discussion Area > Flight Bows

drying conifer woods for arrow shafts

<< < (3/6) > >>

joachimM:
baking wood, or toasting, changes the hygroscopicity of the wood itself by the early combustion process of hemicellulose molecules, which have a high affinity for water molecules.

toasting beech for example, reduces its equilibrium MC from 10% to 5% at an ambient MC of 66%.
Since drier wood is stiffer too (in compression), toasting arrows increases spine.
That's exactly the reason bamboo for splitcane fly-rods is baked during the manufacturing process.
For the technical info, see http://www.primitivearcher.com/smf/index.php/topic,51962.0.html (and second page).

Since all woods contain hemicellulose, this affects all wood species. But there are strong differences in types of hemicellulose among wood species.
I noticed that some woods require a deeper / longer baking than others, for the same result. I long thought that my fir boards didn't respond well to heat treatment, until I forgot a slat in my pizza-oven at 300°C (but cooling down), and only recovered it after half an hour when I also removed the burnt focaccia I had tried to make. The slat had changed (on the belly side, which was lying on the oven stones) from cream to dark brown, had become concave at the toasted side. The change was dramatic and didn't disappear after some time.

So maybe if someone's toasting results only seem temporary, I guess this is due to a mere change in MC (and a rebound afterwards), and the toasting wasn't done long enough or hot enough to markedly affect the hemicellulose content and structure.

willie:
Joachim-
thanks for posting that link to the earlier discussion and an explanation of your discoveries. The extreme temps do seem to offer hygroscopic reduction benefits, but not so much for stiffness, at least not with the conifers I have been looking at.  I do wonder if the improvements with bamboo are more than just drying ? 

I have been drying in a hot box that is nothing more than a Styrofoam lined cardboard box with a old florescent lamp inside. Seems to maintain about 40 F. above ambient temps, it's enough to lower relative humidities considerably. The larch has stiffened up nicely. Still looking for some better spruce, and some  doug fir is still drying.

Steve, is optimizing spine requirements mostly about a smooth release?

Badger:
   Willie, stiffer spines allow me smaller diameter arrows, I prefer dense woods with stiff spines when I can find them. I have had pretty good luck with purple heart when I can find straight grain. I had some 11/32 larch with 100# spine. That was also good stuff to work with.

avcase:

--- Quote from: willie on November 08, 2017, 11:07:57 pm ---Alan, Did you see significant reductions in MOR when you heated your sitka spruce?
I guess I think of stiffness (bending strength) as governing design, but I best not ignore ultimate strength if my bow hand is going to be in the line of fire.

Btw, In the flight community, is there a commonly used spine test standard for short arrows? Otherwise I can make my spreadsheet  accept any length/thickness etc.. And calculate MOE to predict spine.

--- End quote ---

I didn’t test the strength of my heat treated arrows, I only tested the stiffness.
   The info I have seen on the effect of heat on strength is from research by the forest product industry or supporting government agencies, or from those who make fly rods.

willie:
Larch that tests 100# (.26" deflection with 2# weight at 26") is quite the find in 11/32 dia.
75#  seems like the best I will be able to get out of this batch. My preliminary sampling shows a 25% difference in the relative stiffness of spruce, pine, doug fir and larch. The doug fir and larch is heavier on an absolute and relative (stiffness per density) basis, and in spite of the adage that spruce is supposed to be the "strongest for it weight" , the lodge pole pine stiffness seems to be coming out on top of the spruce sample currently have in the drier. I guess I misunderstood what was meant by "optimization" if one is simply seeking to find best spine per diameter. Aero dynamically, spine per diameter seems to be desirable, but at the expense of how much extra mass seems to be the $64 question.

Perhaps I should  ask if "normal" wood arrows are still competitive in classes that allow carbon, or for that matter, how about the composite bamboo arrows that you make, Alan?
 
Btw, I have recently located a commercial supply of sitka/lutz spruce that might have some potential. It seems like the slower growing variety is in demand for its strength. Available up 50 rings per inch and "dehumidification kiln" dried. The drying process limits ambient temps to 120 F. max for quality purposes.
 

Navigation

[0] Message Index

[#] Next page

[*] Previous page