Puzzled ,how does a 50lb bow become a 78lb bow

[SLIMBOB]

Really got me perplexed.  An Osage self bow I made last spring was drawing 52lb at 27 inches then.  I figured it would settle in 50lb.  I noticed the last couple of times I strung it (last fall) that it was a bit difficult to string.  Felt heavy.  I shot it and it was definitely pulling more than 50 but I didn't weigh it.  I strung it during Xmas and knew something was wrong.  Way heavy just to string so I unstrung and let it set.  Today I put it on the scale.  5 1/2 inch brace height.  10lbs at 10 inches, 30lbs at 15 inches.  That's as far as I drew it.  It's gaining 4lbs per inch.  At that rate it will hit 50lbs at 20 inches, 78lbs at 27 inches???  Maybe others have experienced this and I'm just behind, but I've built countless Osage bows in all seasons.  Green wood, dry wood, seasoned wood you name it and I've never seen this before or even heard anybody talk about it.  The stave was given to me bark on last Feb.  Supposed to have been dry and it certainly seemed to be.  It worked like dry wood and I can tell the difference.  Not a single check any where.  It finished out then with a couple of inches of reflex and that is where it sits now.  Pipe straight.  Better than the alternative I guess, but has anyone else ever had this happen???

[PatM]

Dried versus cured.

[SLIMBOB]

Thought about that, but that much weight?  It picked up nearly 40lbs.

[Badger]

I think a couple things might be at play. 1st I would say the moisture was probably higher than you thought. The next thing I have also seen happen when I let a bow get a little out of tiller and repair the tiller before I get to full draw. I think the bow suffers a little compression losses but then heels up as it cures. I am guess the bow will drop down as you draw it further and end up maybe 10# or so heavy when you get to full draw.

   Just for the heck of it I would pull the bow 1" at a time past 15" and go back to 15" every time and recheck the weight. I bet it stats gradually dropping and more rapidly dropping as you apprach full draw.

[JackCrafty]

Yes, this happens when I use osage that is extremely dense and heavy.  Mine gain about 2lb per month for three to six months after they are finished. I don't see this effect with light-weight osage.

[burchett.donald]

  Slim, I've had RH change my white woods but only a couple of pounds but never experienced what you've described...Would be interesting to know what actually went on with yours.

[SLIMBOB]

Badger, I did not pull it past 15 inches, but I worked it up to that just to be safe.  I will do as you suggested and see if it makes a difference.  Tiller looks just as good today as it did then, granted only at 15 inches.  Shot this thing a bunch over the summer and so it's well shot in.  Or it was.
Jackcrafty, I would not have said this was a particularly dense piece of wood.  Might have been.  Smallish diameter stave with a pretty high crown.  Very knotty piece of wood, neon yellow.  Seemed pretty average to me at the time as far as density went.  It took very little set from start to finish, but may be.  40lbs??
Shot a bunch of mine today.  All the others are where they should be so RH not a factor as far as I can tell.  Pretty wet day really.  RH got extremely low last week, but only for a day or 2.

Refigured and its 30lbs.  I've never had one change half that much.
I've had them lose a little weight on hot humid days, and gain a little on bitter cold and dry days, but it's near 80 here today after a rain.

[Josh B]

I've only had it happen once and it was with ironwood.  SOY made me an ironwood takedown that was a pleasant45#@28".  A year later 74#@28".  I figured it was a bit higher in moisture in MN where it was made and it dried out some more here in drier KS.  Josh

[BOWMAN53]

Yup my Osage recurve was originally 50# now it's closer to 70#

[SLIMBOB]

Interesting.  Never had one change much at all.  If anything they lost weight.   This one has become one of my favorites, so I'm gonna try Badgers advice first.  If it will settle around 60lbs I'm ok.  If not, and I will have to retiller it as I cant draw it back as it is.  Scared to!

[toomanyknots]

I've had an osage molly gain weight like that.

[huisme]

And I've had a black locust molly gain weight, just not to the same extent I'd expect Osage could gain weight since BL does a more thorough job of crushing its belly

[lostarrow]

too high MC when it was made tillering allowed the wood to dry thoroughly , and possibly a lower RH now than when tillered.Was your stave fairly thick? Could have been dry on the outside and green on the inside.  When Air drying lumber , the rule is  at least 1 year for every inch  the thicker you go though the less that rule applies. A 6x6 will not likely be  as dry on the inside after 6 years as a 1x6 will be after a year. Through the cycles of drying and rehydrating a piece of wood will regain less and less moisture once lost. This is seasoning.
  Disregard if you already know this of course.

Yes, this happens when I use osage that is extremely dense and heavy.  Mine gain about 2lb per month for three to six months after they are finished. I don't see this effect with light-weight osage.

   

 You live in a very dry climate don't you Patrick? Where do you get your Osage  from?  I think this is a case of the same cause and effect. JMHO

[JackCrafty]

I get my osage from various sources, but mainly from the heartland (Missouri and surrounding states).  I don't use Texas osage any more.

And yes, my climate is VERY dry.  I've gotten rid of all of my staves that can't handle the dryness.  The woods with the highest specific gravity seem to do best.

[H Rhodes]

I had a heat treated winged elm bow go from 50 to 70 once over the course of about 6 months.  It was reflexed about an inch and is still dead flat after shooting a lot at 70 pounds and then retillering it to 45lbs.  I guessed that it had to do with moisture content, but as someone said above, maybe the dried wood as opposed to cured wood is the deal.  It is an odd phenom.  The last thing you expect is a bow to gain a bunch of weight from just sitting around.