Sinew reflex creep

[sleek]

I asked this in horn bows but I want to know here too. On your sinew backed bows, after unstringing it, how much reflex do you loose, and how much comes back over what period of time?

[bassman211]

Some spring right back to original shape as soon as I un string the bow. Those are my best built bows, but I have more that will take from 5 to 15 minutes to return to battery.

[sleek]

Some spring right back to original shape as soon as I un string the bow. Those are my best built bows, but I have more that will take from 5 to 15 minutes to return to battery.

About how much reflex is lost and comes back inside those 15 minutes?

[bassman211]

On mine maybe an inch, or more. You having trouble with one? Humid when you shoot? Hickory, Osage,elm? What wood?

[sleek]

On mine maybe an inch, or more. You having trouble with one? Humid when you shoot? Hickory, Osage,elm? What wood?

I got an osage sinew short recurve that had some reflex pull out. trying to find out what's normal for these bows. Yes it is humid, I am in Norfolk Virginia with it past 2 months. It's in the car windows up hit boxing right now trying to get it dried out.

It actually lost 5 pounds of draw weight and the energy storage on the FD curve went to crap.

[StickMark]

Yes, I see "coming back" of the bow, and can see a 5# drop.

My small data set to share:
Specimen: 55ttt sinew backed hickory. 3 course, and one more down middle.
I can see almost an inch come back. Natural deflex in the bow, and I flipped one tip to match the other more recurved. Normally 0.5 inch gap between handle area and wall that I set bow against. After shooting in Tucson high monsoon humidity of about 45%, the gap is 1.4" or so, then later, back to 0.5"

Regarding humidity and heat, I took this bow on a desert trip and brought a bow scale. Temps ranged from 80 at night to 108. 20% to 55% RH.


Being strung for three hours, bow is 46.5, pounds. 82 to 95 degrees, 51 to 33% RH.
Letting the bow sit in heat an sun, above the desert floor in some branches, for a few hours, weight dropped to 43.8 pounds. I bet that desert floor gets to 125, 130 degrees.
After sitting unstrung all night, 49 pounds, with 80 degrees, 55% RH, then down
to 45.5# after hunting, shooting stumpers, in 100 plus heat.

So, I saw the a five pounds difference.

[bownarra]

What is important is how you applied the sinew and prepared the stave    
How thick is the sinew?
How thick were the layers you applied?
How long did you leave it to dry both inbetween layers and overall before bending it?
How was the stave prepared? Straight, reflexed? Natural/heat induced?
Did you bend the bow before sinewing?
What glue did you use? Collagen based? Which glue exactly did you use? How was it made? What %'age glue did you use on each layer?
Did you reflex the bow after adding sinew? How? When?

The old hornbowyers from across the Earth pretty much all agreed that hardest part of making hornbows is......sinewing. It's one of those things that is simple in essense but the 'magic' is in the detail....
There has to be a pretty good reason to make a bow then leave it for a year or more (upto 3 years....) before tillering!

[burchett.donald]

  I have this happen with a new bow that is well cured, seems you always give up a little during break in...After settling it gains and loses depending on moisture...No radical change though...Mine are kept in an Air Conditioned climate when resting here in subtropical South Carolina...

[ssrhythm]

I'm dealing with the same issues now with my new bow.  This is my first sinew job and first time dealing with this.  I used right at 3 oz of sinew evenly applied on a 62.5 ttt osage recurve with the center back crowned a bit with an extra layer down the center of the limbs.  I only let it dry for 10 days, but the moisture meters were both showing less than 10% MC burried to the back at the thickest part of the sinew where it was built up on the back of the handle.

I have not measured, but I'm estimating I'm losing two inches of reflex after shooting it a good bit.  It returns to near what it was to start with within 15 to 20 minutes, and it is fully returned by the time I pick it up the next day...how long its taking to fully return to pre-shooting reflex I'll start measuring to figure all this out in exact numbers.

I'm shooting this thing in temps between 85 and 100 degrees with RH values running between 13 and 25 %. 

All that said, when I put it on the rack and check the weight, it is consistently 62.5# at 28" and ~60# ar 27" after shooting it.  The tiller is flipping from ~ 1/4" pos at first brace after stringing to slightly negative after shooting it.

I'm sure all the changes and dynamics are due to imperfections in my tillering job combined with areas of natural deflex that I took out with dry heat wanting to return to their natural state during shooting...but the sinew is minimizing all that and bringing it back around after I unstring it. 

I'm a little worried about what is going to happen once I get up on the mountain chasing elk and have a serious cold front bust through.  The small RH fluctuations aren't seeming to affect this bow much if any, but I'm hoping that I'll be able to pull this joker to full draw when its 30-40 degrees. 

[ssrhythm]

What is important is how you applied the sinew and prepared the stave    
How thick is the sinew?
How thick were the layers you applied?
How long did you leave it to dry both inbetween layers and overall before bending it?
How was the stave prepared? Straight, reflexed? Natural/heat induced?
Did you bend the bow before sinewing?
What glue did you use? Collagen based? Which glue exactly did you use? How was it made? What %'age glue did you use on each layer?
Did you reflex the bow after adding sinew? How? When?

The old hornbowyers from across the Earth pretty much all agreed that hardest part of making hornbows is......sinewing. It's one of those things that is simple in essense but the 'magic' is in the detail....
There has to be a pretty good reason to make a bow then leave it for a year or more (upto 3 years....) before tillering!

You offer a ton of good advice on sinew jobs.  I agree with you on the sinew drying times, and that may be a greater factor than tillering imperfections when it comes to this "sinew creep" issue.  You told me that it would take up to 6 weeks or more for my sinew to cure to where I could start bending it and re-finishing the tiller.  Unfortunately, this bow needed to be done way before then, and in this ultra-dry climate, the moisture meters were showing a sufficiently dry backing...so I proceeded.  Now that I've thought about it, the moisutre meter prongs were burying between individual bundles of many individual fibres and reading the MC of the area surrounding the sinew.  Ie, I think the glue had dried sufficiently to start bending, but I'm pretty sure that the MC in each individual fibre that comprise the strands that make the bundles...I'll bet they had a good bit more drying and shrinking to do.  I think if you left the job to cure in a low RH environment for 6 months or more, this "sinew-creep" issue would be minimized maybe to the point that it wouldn't be noticible if tillering wasn't horrible.  If I ever do another one, I'll stick it in a dry hot-box and leave it for 6 months or more.  Until then, I'm going to try like heck to get my tillering improved enough to not have to be applying any sinew.

[sleek]

This sinew job is made of salvaged sinew from a bow that was broken then given to me. I soaked it, peeled it, replied it on my bow. This was back in February. Left it in my car every day to dry. I pulled on it about 2 months, maybe 3 ago, and plotted an fd curve. It looked great. A few spots had lifted since then so I did a sinew wrap around them, waited 3 days and pulled on it. That's when I saw the reduced performance. The bow had gone from Lake Charles Louisiana when made to Norfolk Virginia, and has stayed in a hot car every day.