Edge grained Maple backed Yew

[DC]

Mostly this bow has been shot on the machine in my garage. I took it to the range last Monday and I was really pleased. I now know what "sweet shooting" is. I know I'm not pulling it to the 28" mark but the draw is very smooth and even. At 2# per inch I'm probably pulling 37-38# but it feels like a lot less than that. I'm liking this bow.

[dolgima]

thanks DC and thanks Badger  i read your no set tiller interestingly
i add question 7 while you answer  so could you explain about question 7 ?

and is there any f/d curve of this bow? in light of arrow speed i expect rapid increase of   early draw weight.  i want to compare it with other recurve bow f/d curve

[Marc St Louis]

7. http://www.primitivearcher.com/smf/index.php/topic,62668.msg878994.html#msg878994 if I bend recurve like this, it won't tear? why put strip? because wood take less tension thanks to metal strip?  If it is, I must clamp  and vise  tightly so strip can do his role ?


even myself, i can't  understand what i'm talking about...  sorry again and thanks in advance

The vise is lightly clamped down

[ty_in_ND]

That's a sweet bow, DC!  Thanks for sharing it with us.

[dolgima]

[/quote]

The vise is lightly clamped down
[/quote]

if it’s lightly clamped down  it doesn’t slip?
then  what is the role of metal strip?  strip is nothing to do with relieving tention of recurve?

[Marc St Louis]

The vise is lightly clamped down
[/quote]

if it’s lightly clamped down  it doesn’t slip?
then  what is the role of metal strip?  strip is nothing to do with relieving tention of recurve?
[/quote]

Of course it slips a little.  If it didn't slip then I would be trying to stretch the metal, not good

[avcase]

I get a virtual mass estimate closer to 71 grains, which puts it on par with some of the best custom carbon and glass bows. The chrono readings are consistent with this, so I don’t doubt the chrono readings or draw weight readings.  This is an exceptional bow you made!

Alan

[Badger]

  That's almost exactly what I came up with Allen. 71 grains is super low! Almost too low. DC has done everything right checking and rechecking calibration to his scales. I can't help but think there is some small thing we are missing that would throw that off a little. I have  a bow with an almost identical profile that stores more energy. I suspect this bow is storing more energy than we are reading. maybe just a couple of pounds. The two bows build almost identical but mine starts higher. Also his light arrow speeds would suggest a slightly higher virtual mass. Still an exceptional bow either way. So good it draws attention.

[DC]

Do the formulae that you guys use take into account string weight, tip weight, that kind of thing?

[Springbuck]

Lovely bow and excellent performance. 

Most of the time I will reflex the limbs with dry heat before I glue the backing down, if it's a type of wood that reacts well to heat that is, and then add more reflex on glue-up.  The bow keeps much more reflex that way.  If the wood benefits greatly from heat-treating then I do that as well as I am reflexing it.

  That's very interesting, Marc.  I have never considered that.  I did once attempt to heat treat an entire belly lam all the way through before Perry reflexing and backing, in an attempt to improve decent wood to excellent, but it didn't work well.  Even when I put it through my friend's Pizza oven I couldn't get a really even temoper without burning something or leaving patchy spots. 

[Springbuck]

And congratulations on this bow, DC.  She's a beauty.

[avcase]

Do the formulae that you guys use take into account string weight, tip weight, that kind of thing?

Short answer is yes.

I got about 38.4 ft-lb if stored energy when I smoothed out some of the noise in the force-draw readings. Given the 192 fps reading with a 400 grain arrow, the virtual mass number estimates speeds for any arrow weight. These estimated speeds are within a fps or two of the speeds measured for the lighter and heavier arrows shot. This indicates that the measurements made were consistent with each other and pretty accurate. It did look like the speed reading for the lightest arrow shot was a bit low, but the virtual mass model isn’t 100% with large arrow mass changes. 

To put this in perspective, the Modern composite Longbow that holds the current 50# Flight Record has about the same virtual mass as this simple composite wood bow!

Alan

[DC]

I always amazes me what a guy can luck into.

[Badger]

  Allen, your stored energy figure was a little higher than the one I had come up with. helps to make more sense. The consistency of the virtual mass projected speeds and actual speeds indicates very low hysteresis and actually comes out extremely clean in the numbers. I guess I am just having a hard time accepting numbers this good with a relatively conservative profile. If there was a mistake in the calculations it would almost have to be something linear and very small. My first guess would be maybe something like a 1# error in the force draw from start to finish adding about 2# stored energy. I realize it is very possible that the numbers really are as good as they look but when they get this good it is really fun to pick them apart and look for the smallest deviation.

[selfbow joe]

Beautiful bow