Build Along ( building by mass)

[DanaM]

I think I have it bending into fades fairly well, I'm going for a more elliptical tiller
with quite stiff outer limbs. I put it on the form today I only ended up with 1" of reflex
my form isn't very agressive. I will give it a few days to rehydrate then finish er up.

[Woodbear]

Steve,

       Thanks for having a look at the bow.

   You are right about having the bow calculated for strain. The bow was calculated for 0.7% strain in the working arms, and slightly less strain in the handle. The center 6 inch of the bow is at 0.6% strain, adjusting to full strain (0.7%) outside of the center 12inches.

The bow mass is 18 Oz. …….I consider the handle as somewhere between full, and semi-working, as the strain is only 15% less than the arms. So, I was thinking that the value to put in to the formula for handle length would be something less than ½ of the 12 inch reduced strain length.  However it takes 8 inch (which is more than ½ of 12) to get the actual bow mass. I designed for 28 inch draw to have a bit of safety margin. The bow has 1.5 inch of just unbraced set after use at up to about 26 inch draw. (About 1 inch set rested) It has a crowned belly and is oak so I thought the set to be about right.

Do you think that for a narrowed handle bow, intended to have a working handle, there still needs to be some handle length value put in to the formula, as opposed to, say, a full working ELB style?

Dave

[Badger]

Dave, I would bet if you had a little more bending in the inner limb it would not have taken that set, I based the projected mass on the tiller you used, it did take a bit of set there so could have used a bit more width in the high bending area ( little more mass) I really like the way you gradualy taper your limbs out of the fades into their high bending areas being the widest, that is a good example of mass logic as it applies to bows. I have one right now I am tillering with the utmost care, so far out to 26" and no sign of set yet, I hope I can make it out to 28" with no set but seldom do with this particular design.
     

[Badger]

Trying another experiment just to see how close it comes. Took a 1 1/2X3/4" red oak board 72" long.
I left the center 16" of the bow paralell and tapered the remaining limb to 3/8 tips. After rounding off the corners the stave weighs 21 oz. The center is bending but not as much as the rest of the bow so I am going to give the center a value of 4" for stiff handle and fades. According to this the bow should come out around 65# with no tillering. I am curious how close it will come, if it doesnt break. Going to go cut some nocks and check the draw weight, wish me luck LOL.  Steve

[Badger]

Came out pretty close, bow is drawing 65# @25" and need a little tillering in the outer limbs where it is a bit too stiff. Aftet tillering those out even the bow will be down to about 18.5 oz where the formula says it should draw about 52#. Going to proceed there. Steve

[Badger]

      Well, didn't have to take off as much wood as I thought, bow is at 19 1/4 oz, should be good for about 57#, right now pulling 60# at 26". Taking about 3/4' set, mostly from when I was drawing it to 65#. Not really a great piece of wood and I don't have much time in it so I think I will go ahead and just draw it out to 28" to see if it breaks or takes excessive set. BRB.......
       Survived about 1/2 dozen draws to 28" then let go. Was pulling 67# at 28" a bit too heavy for that wood, at 57# it would have been reliable. This was about letting the formula drive the draw weight, seemed to do that pretty well. Steve
       

[DanaM]

Steve do add a little extra mass for a character stave???

[Badger]

Dana, on character stves I just play them by ear like anyone would do. If the character is confined to small pin knots I try to keep the mass pretty close, or if the character is a series uf humps and bump without knots I will try to stay close, but yes I do add allow extra but no figures for that I just wing it. Steve

[mullet]

  Steve, Did I miss the finished bow? what happened to the Mulberry one you were going to do at the same time? Looking forward to seeing it.

[jamie]

i think my head just exploded

[mullet]

  I got lost in all the mass jamie. Well , what happened to the Mulberry bow?

[Badger]

 Eddie, I have been running growth rings on it for the last 2 weeks lol. Took a while longer than I thought to get the ring I wanted my shop is outside so the rain slows things down. I should be back on it this week. The wood looks real good , I have two other mulberry staves here that are not nearly as dense. Steve

[mullet]

 Cool Steve, I was looking forward to seeing what you get out of it.