Main Discussion Area > Bows
Heat treating demystified (Somewhat)
Marc St Louis:
Wood is wood no matter if it's heat-treated or not. Tempering wood does not affect its elasticity and that is the determining factor on how long a bow will last. If you heat-treat a bow, properly, and reflex the heck out of it then it will not last as long as the same bow with less introduced reflex. This is because the heat re-shapes the wood cells (plasticizes) so that it can be re-formed into a different shape. The elasticity of the wood is not affected but the new belly shape has to undergo higher compression forces for the same draw length. If the back has enough tension strength/elasticity to survive then at one point the belly will start to fail. If you want a shorter lived, high performance hunting bow that will only be shot in hunting situations then a highly reflexed, heat-treated bow will give you years of use. On the other hand if you are going to use this same bow for steady target practice in addition to hunting with it in the fall then it's life span will be considerably reduced. If it's a target bow you want then simply heat-treating the wood with no additional reflex will give you a slightly better performing bow than one that has not been heat-treated and this bow will last as long as the bow that has not been heat-treated. Once again, the elasticity of the wood being heat-treated does not change, unless you take your heat-treating too far. Remember, Brown is good, Black is bad.
As to bows I have made. I have some out there that were heat-treated 10 years ago. They were highly reflexed bows used extensively for hunting/target and they are starting to show their age. Whether or not these same bows would have survived longer without the heat-treating is unknown as I can't go back in time and take it back :-).
P.S. There was a tech paper available from the USDA Forest Service on using heat and chemicals to re-shape wood. I read the paper many years ago and it was an interesting read. Unfortunately I went to the site and couldn't find it anymore.
Jim Davis:
I think the facts of that article and folks experience with heat treating wood can be summarized by saying that there is a temperature at which wood starts to become stronger in compression. Through a fairly small range of higher temperatures, the strength in compression continues to increase. At a higher temperature, the wood begins to decrease in compression strength, and possibly in tension strength.
The best temperature for strength gain can be gauged by the color change in the surface of the wood. A color similar to lightly toasted white bread indicates a temperature that strengthens the wood. Colors darker than that indicate temperatures that are weakening the wood.
This is in line with what Marc said above and in his chapter on heat treating in the TBB.
Refining these principles requires good measuring equipment or judgement based on experience.
J
lostarrow:
Thanks again for your input Marc. I believe we are stating the same point of view.If you think something doesn't jive with your findings (I agree with everything I have seen)please quote the statement in question so we can further our Knowledge in productive manner without having to repeat ourselves .Once again thank you for the straight forward findings you have presented. I think we may have exhausted this one for now.
PEARL DRUMS:
My simple mind hurts you guys..........
scp:
Mine too! Still I sure would like to know what happens to the wood when we heat treat it. We all seem to agree that some moisture is removed. That might bring on some structural change. But heating treating does not appear to be same as simple drying and there might be even some chemical or molecular level changes. The simplest way to test this is to seal the back and sides of a bow real well and dry its belly as long as it takes to the level of just heat treated belly.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version