When is it too hot in temps for sinew backed

[bownarra]

Yes JW that is a fact. Around 40 - 45 celcius was the temperature used. 105 - 115 f.
During construction of a hornbow when gluing the horn to the core the horn is heated to around 50 celcius. The horn at this point has many sizings coats of thin glue. The heat is to soften the horn so it follows the cores shape perfectly and with less ressitance. Also during tillering the bow can be heated to 50 degrees for correction of twists. Relatively high heat is the primary tool for correcting twists etc on hornbows.....funny how they don't all fall apart

[Tom Dulaney]

https://www.atarn.org/chinese/Yanghai/Scythian_bow_ATARN.pdf

The core's back was made round as the original's, scraped smooth, lightly
grooved, well sized with glue and the limbs backed with sinew (soaked in 25%
glue) over the (future) deflexed sections. This backing was done before bending
the mid-limbs for the added security. The sinew did not need to be applied in the
final thickness at this time. Since the heat required for bending could cause
delamination of the limbs, the entire mid-limb section was then bound with
sinew.

The ambient humidity should be no less than about 60%RH for the materials to
have sufficient moisture content for bending. The 60%RH represents moderately
humid conditions, which would likely be encountered in a human-occupied tent
even in a dry climate of Central Asia, perhaps augmented by a pot with boiling water.

 The sections were exposed to slow heat, making sure the surface  temperature did not exceed 60⁰c, for about 1 hour. Then the limbs were bent  over pre-made formers (similar to the Turkish tepeliks for the replica). The forces  needed to flex the core were not excessive at all. The pressure was maintained  until the curvature exceeded the desired profile to account for spring-back. Since  the bow‟s core, unlike in the finished bow, was wider than thicker at this stage  and the bending was done in the plane perpendicular to the greater dimension of  the laminated limb, no problems with limb twist was encountered and the limbs  remained perfectly aligned.  After the limbs had cooled, the sinew binding was removed, leaving the sinew  backing in place. There was some slippage of the parts at one of the wood splices  within the core, now visible on the belly. It did not, however, weaken the limb in  any way and the splice held well. Interestingly, on the original bow's back, a  small step was found at the location of one of the splices where the parts joined.  If the step was caused by the slippage at the splice, it indicates the original bow  could indeed be heat-bent after the core was laminated together, following the  same methods as in the replica, with the slip under the sinew left unseen by the  bowyer and never corrected. There is no doubt this method was the most logical  and practical for the bowyer to force the limbs into the permanent deflex.

3:50 mark:



https://www.youtube.com/watch?v=N6AUq6f5SD8



This is the part where JW Halverson publicly apologizes to me for his barbaric arrogance and stupidity.

[PatM]

Just stop, Tom. Try to be more productive and less combative in your silly way.

[Tom Dulaney]

Yes JW that is a fact. Around 40 - 45 celcius was the temperature used. 105 - 115 f.
During construction of a hornbow when gluing the horn to the core the horn is heated to around 50 celcius. The horn at this point has many sizings coats of thin glue. The heat is to soften the horn so it follows the cores shape perfectly and with less ressitance. Also during tillering the bow can be heated to 50 degrees for correction of twists. Relatively high heat is the primary tool for correcting twists etc on hornbows.....funny how they don't all fall apart

The original Ottoman hornbowyers never used those stupid lightbulb boxes, for the obvious reason that lightbulbs and accurate thermometers didn't exist in Turkey until the 20th century, when the art was dead. They are a toy of 21st century morons who call whatever is is they do "Turkish archery". Nobody stores a bow at +105 degress farenheit.

[PatM]

 Goodbye Tom.

[Tom Dulaney]

  Cured Hide glue  does not suffer from heat, 

Oh yes it does.

Sure if you throw it in the fire it will burn but that's not what we are talking about here

If the surface of the bow heats up beyond 105 degrees farenheit, glue is going to soften up considerably. That can easily happen in a quiver exposed to direct sunlight south of the 35th parallel, particularly if the quiver is animal skin.

105 F.  Really?  I have done a mild heat-treat on a sinew backed bow with no adverse effects to the hide glue and that was a heck of a lot higher temp than 105 F.  You must be thinking of those people that use TB3 with their sinew to back bows and even then it would take a lot more than 105 degrees, maybe 105 degrees C. 

Spreading false information doesn't help anyone

You're a riot. You have no way of knowing whether your bow was affected or not. For all you know, it would have shot better without the heat treatment. Adam Karpowicz tried to bend a glued up Scythian bow and made sure, using an electric thermometer, that the surface  temperature never exceeded 60⁰F. The glue softened up, and one of the (sinew-backed) joints in the wooden core slipped. What makes you think the sinew isn't slipping and catching air bubbles at those temperatures? It most assuredly is. You just can't see it. You'll never know what that bow's performance could have been without the heat treatment/abuse.

The takeaway here though is that Adam did a more severe bend than probably anyone here has ever done, using less than 60⁰C heat. You will never need a temperature higher than that as a bowyer.

I never, ever let glue get exposed to +105⁰F degree heat. That you would expose it to 105⁰C reveals your ignorance. That kind of temperature will destroy wood, much less glue. These materials aren't heat resistant as some of you seem to bizarrely think they are. Why you think you would need that much temperature is perplexing, when they clearly respond more ideally to warmth (100-105⁰f degress farenheit), rather than heat. A fact that aptly demonstrates their sensitivity to temperature change.

[Tom Dulaney]

Goodbye Tom.

Good morning Pat.

[PatM]

You seem to not know the difference between C and F or the meaning of belies. Or about heat treating wood either.

[Tom Dulaney]

You seem to not know the difference between C and F or the meaning of belies. Or about heat treating wood either.

"Heat treating wood" is an oxymoron and a superstitious ritual developed by primitive bowyers. It's a great way to destroy a bow. I didn't get any specs wrong in that post and picking apart accidental double negatives just shows your catty vindictiveness towards me.

[PatM]

Tom, 60 degrees C is 140 F.

[StickMark]

Well, the consensus seems to be that a sinew bow will not suffer any significant performance loss at temperatures that may reach into the 100-115 range in the noon time.

[Digital Caveman]

Tom, we don't know how experienced you are, and we all know that even the most experienced bowyers can be mistaken on some accounts, but if you want us to believe that your opinions are better than methods developed over decades or centuries you will have to provide a lot more evidence than you have so far.  A little practical experience and humility wouldn't hurt either.

[PatM]

 Why would Marc have no way of knowing how the bow would have shot before heating it?  All he had to do was shoot it before and after.

  I have corrected a sinew backed bow many times with high heat on the belly side.

[Tom Dulaney]

Tom, 60 degrees C is 140 F.

Yeah, and temperatures lower than that were sufficient to cause a slip in a glue joint in Adam Karpowicz's bow. JW Halverson said it was fine to use 145⁰F, even +210⁰f.

[Tom Dulaney]

Well, the consensus seems to be that a sinew bow will not suffer any significant performance loss at temperatures that may reach into the 100-115 range in the noon time.

Yes, 100-115⁰f ambient temperature is fine. That's not the same thing as the temperature on the bow's surface. Heat the surface of a sinew bow to 115⁰f and you may very well slough the sinew off before you get to full draw.