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Heat treating demystified (Somewhat)
Marc St Louis:
As I said, the weight loss was LESS than 2% and this was right after heat-treating. After letting the wood sit for a few days it regained most of the lost weight. I do agree that the shrinking of the belly would mean that there would be less space for moisture to return but this is one of the benefit of heat-treating. Simply air dried wood will not achieve the same results even if you dried it for 20 years. The heat-treating process plasticizes the belly wood and allows it to be re-shaped, I'm sure that this plasticized wood does not allow moisture back in. One of the things about high density tropical wood species that makes them so heavy and resistant to water is their lack of air space in their cells, space that can be occupied by water. By heat-treating the belly of a white-wood you basically shrink it down and increase its density which increases its compression strength.
I sent a fairly short heat-treated Elm recurve many years ago to a guy in Arkansas. He brought the bow to one of the first Mojams and was showing it to some people down there. He told me that the guys were amazed to see the bow keep it's reflex when unstrung after being held at full draw, the weather was quite humid at the time.
BowEd:
I should leave this thread with the last word said by the innovator of this thread but I'm selfish.Sorry I'll work on it.Everybody's up early today.Guess we are all church goers......LOL.OOOps that's a touchy subject....sorry.Personally I'm just up for no reason other than I can't sleep no more.....LOL.
This bow making to me is having a knowledge of the properties of different types of woods.To back up what hrodes said I always take a future bow inside roughed out from a stave.Weigh it till it quits losing weight at a controlled humidity.That can take weeks sometimes to get that last moisture point.Then finish it out.I don't own a moisture meter.I've been told by different bow makers oh that's a lot of fuss to do.Then their bow after being made follows the string bad or does'nt cast very well and blame the wood.To me it's worth the time.
After heat treating I have weighed bows made too.2% loss mass weight is about right.Most times it does'nt gain very much back.Whitewood gains draw weight.Hedge does'nt so much for me because it is already plenty dense.
Good post lost arrow.
I'll quit now no sense in beating a dead horse to death.
druid:
lostarrow, thank you one more time for these datas. Great to see so much expirienced faces here in this topic.
Jim Davis:
I am constantly mystified by the tendency to promote anecdotal experiences without checking whether scientific studies on a given subject have already been done. The document linked below presents clear evidence about the results of heat treating wood. It is a lengthy document, but very useful as the subject relates to bow making.
http://www.ncsu.edu/bioresnnources/BioRes_03/BioRes_03_2_Kocaefe_PB_ThermalTreat_Aspen.pdf
Jim Davis
lostarrow:
Hi Jim , thanks for the link to the article . It appears to be a paper written in 2008 if I'm correct. Looks like someone was trying to convince a lumber company to try heat as an alternative to chemical treatment for lumber.This is all old info in the industry and is taught in most of the better Cabinetmaking and Furnituremaking schools as the basics. As I mentioned in an earlier reply I am trying to present the info in a way that is easy to understand and practical for our purposes on this site .I'm trying to give the reasons behind the successful anecdotes to help people understand why a "proven method" may have let them down.Basically ,what the document said in dozens of pages, with volumes of information was summed up in a few paragraphs above in laymans terms with a visual experiment to further the understanding. I'm not trying to take the magic out of bowmaking ,just trying to make us all better magicians.If you wanted to do a thorough search you could find a hundred more articles saying the same thing. I too am leery on anecdotal evidence but based on my own education and firsthand knowledge on the subject of wood and how to shape and manipulate it , I found Marc's presentation of his findings to be very well founded.He may not have used the" standards of scientific testing" but he never suggested that he did. He gave his findings based on what he tried and the results he could measure based on the equipment he had to measure them.If not presented in the "real life scenario" that Marc did in TBB , few people if any would be doing it today. Thanks again for the link. (I had to type in a search on the site to get it . "Thermal manipulation Aspen" I believe is what I used )
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