elm sapling ?

[Jim Davis]

Jawge and Pearl, you both have valid points: Wood is 3 to 4 times stronger in tension than compression, but there is a point where a the back of a sapling is so highly crowned that less than a  third of it's back is doing the tension work.

However, the few sapling bows I have had fail all failed by chrysalling, meaning the back was stronger than the belly.

Pearl, the narrow crown, or the narrowed back of a trapazoidal cross section turns out to help performance by reducing limb weight--in tension, wood has almost no stretch before breaking. So, it doesn't hold that we are balancing the elasticity of back and belly (as I believed until shown otherwise in testing literature). We just don't need as much wood on the back to be as strong as the belly.

Jim Davis

[George Tsoukalas]

Now, Jim, I never disagreed about the trapezoidal shape  nor did I ever disagree that most woods are stronger in tension. Just want to set the record straight.
Jawgey

[Badger]

  Something I have never been able to figure is how the tension distributes itself to the compression wood. Does it go straight down or does it angle out? My feeling is that it angles on slightly. If thats the case you may have an 80# running down the middle with 10# bows along the edges and it averages out to 50#, the thicker wood is doing more than its share. The tension wood has to have some stretch to it just to be able to bend it, I have no idea how much.

[JoJoDapyro]

To throw in my very small experience, I had about the same sapling, and tried to split it, I was 180 from top to bottom. I roughed out a 48 ntn short bow, and decided to back it with bamboo. After 3 days of drying I put it on the rack, and worked it a bit, when I gave it a bit more the bamboo broke, not the elm. Tough stuff.

[Jim Davis]

To throw in my very small experience, I had about the same sapling, and tried to split it, I was 180 from top to bottom. I roughed out a 48 ntn short bow, and decided to back it with bamboo. After 3 days of drying I put it on the rack, and worked it a bit, when I gave it a bit more the bamboo broke, not the elm. Tough stuff.

If you look carefully at the belly where the bamboo back  broke, I'm sure you will find there was a compression failure. With an unviolated  back, there is never a tension failure UNTIL there  has already been a compression failure. The belly will not necessarily be in  two pieces, but it will be  crushed.

[Jim Davis]

Now, Jim, I never disagreed about the trapezoidal shape  nor did I ever disagree that most woods are stronger in tension. Just want to set the record straight.
Jawgey

Jawge, you speak truth,  as always.  I was pointing out that you were also correct about narrow backs and that there  is a  point at which one has to compensate for a high crowned back--such as you mentioned, by making the bow longer than usual.

Jim

[George Tsoukalas]

Guess we have to let the young'uns find out for themselves all these things we've spent years learning, Jim.  It's almost time for the Pokenhope. Gonna miss ya. :(Jawge

[PEARL DRUMS]

Ill figure it out one day guys. Give me some time!

[Onebowonder]

Ill figure it out one day guys. Give me some time!

I don't know Pearly - I think you're a hopeless case!   

OneBow

[paulsemp]

Guess we have to let the young'uns find out for themselves all these things we've spent years learning, Jim.  It's almost time for the Pokenhope. Gonna miss ya. :(Jawge

Or its time for us young'uns to show the some of the old timers things that have been unnecessary for years  .

[bushboy]

 This one is cut down to 66" ttt ,so maybe it will survive?

[Marc St Louis]

I would make it a slight D section to take some stress off the back.  The one I made a few years ago from a 2" D sapling lifted a splinter on the back with a flat belly.

[George Tsoukalas]

Sure, Paul, that's it for sure.

[Pappy]

 
 Pappy

[JoJoDapyro]

I would take years of experience over "New" things more than not. Not all old things are the best way, but there is probably a reason that it has been done like that for so long. Woodworking in a traditional manner is just that, you really can't improve on how something was done 50 or 100 years ago and still consider it "Traditional". If I were given the opportunity to learn from some of these "Old timers" I would jump at the chance.