[English Longbow] Heat treating ash bows

alanesq

New member
At Kviljo's suggestion i have been trying to heat treat the belly on my ash bows to try and stop chrysals forming (as I am trying to make myself a 130lb self ash bow)
my first atempt was a bit of a failure but I am now trying again as it turns out I got the heat treating technique completely wrong

but, before I start I thought I would do an experiment just to see for myself what effect the heat treating as on the wood (and if the way I am now doing it has any effect other than colour the wood)
I have just finished doing this and I think you will agree that the results are pretty conclusive (looks like we are definately on to something here :)


I first set about trying to make myself two identical bits of ash
I did this by cutting a length of the ash I make my bows from, chasing a ring then cutting it into two strips



I then clamped them in my vice and putting a spring balance on the other end started to bend them (one at a time) and I adjusted the thickness of them until they were both deflecting the same amount when 20kg was put on the end (so they are now as close as I can get them identical)

I now heat treated one of them (I did this by putting it under the grill on my cooker for around 10mins, until golden brown ;-)



I then left them alone for 12 hours (I know this should really be a week but I couldnt wait any longer to see what the result is;-) but with them being very small I hoped they would normalize quicker then a bow

I then one at a time put them in the vice to see what change if any had occured:
The heat treated one was now stiffer, deflecting significantly less than the untreated one with 20kg on the end

I now put the un treated one in the vice and pulled it until chrysals started to apear. This turned out to be very easy to do as you can feel the wood suddenly give way a bit when it happens, it happened at 28kg
I then turned clampted the other end in the vice and tried again just to see if it happened at the same weight and sure enough at 29kg I felt it give and chrysals had apeared at the other end




Now was the big moment, to try the heat treated wood !
I put it in the vice and pulled it up to 29kg - no problen at all
so I carried on, and on (constantly releasing, checking for any chrysals and trying a bit higher weight)
eventually at 38kg the wood gave way (in a big way!)



as you can see the wood split almost in half (down a growth ring) but even so the heat treated "belly" still looks in perfect condition with no sign of any chrysal

I guess to be scientific this experiment needs repeating but I am convinced !

----------------------------
Adnl:

It has been suggested it could be the wood being dryer had this effect (from the heat treating)
so I have made some more but I now have to leave them a couple of weeks, to check this idea out
watch this space ;-)

all interesting stuff though
It would be interesting if someone else also tried this to see what results they get (or if they already have?)
 

alanesq

New member
I dont know if anyone here is interested but I thought I would post my latest results in case ;-)


Update - Sat 29th dec

I tried testing them this morning
the results were far from conclusive - both bits of wood failed at the same draw length (both tested twice - once from each end)
they were failing at the back rather than belly so what chrysals did happen were very small but the heat treated one had no sign of any, the normal one some slight ones at both ends

but, I then split both bits of wood down the middle and tested the insides with a moisture meter
the heat treated one is still VERY much drier inside than the un treated one after a week (this surprises me as they are very thin bits of wood)

I guess I need to try again now and this time heat treat an extra one so I can test its moisture before doing the test (to make sure its ready)

but I have to say the results so far look like heat treating is not going to help with stopping chrysals
although it is looking like having the bow VERY dry when tillering it may be worth experimenting with (as I suspect tillering is when most chrysals are caused/happen?)

but, looks like I wont have any more results now for about a month?

btw - I know I had planned to wait 2 weeks but I kept checking it with my moisture meter and I was convinced it was ready a couple of days ago - so it just shows that the meter cant be relied upon
 

HOTHOUSEDOG

New member
Keep up to good work Alan. Testing is the only way to prove/disprove some of the "facts" we accept as amateur Bowyers. Experimentation will only expand your knowledge of the properties of wood. Good luck mate. I await more results.
 
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