Holy DFC Batman...

[Shredd]

  Sorry Guys...  Your right...  It's a great DFC and you will learn a lot from it...   

  I said the bow was Impressive...  What do you want??   

[Mad Max]

Want you to sweat a little

[Mad Max]

If you take into account that those look like very heavy limbs I think you may be disappointed with the arrow speed of a lighter arrow especially at 28" draw...

I agree. Those limbs do look very heavy so their max dryfire arrow weight is probably surprisingly high. That 32" draw is a huge help in getting better performance, I am sure a 28" draw would really gut the numbers.


Mark

Yep

" It will not shoot a light or medium weight arrow very fast but will not be slowed down much by launching a heavy arrow either. This makes the bow well suited for anything that required the use of heavy arrows: warfare and large game hunting. Heavy arrows offer a high degree of penetration through layers of protection (war), increased damage by heavy broadheads (hunting) and increased immobilizing effect due to the arrow's weight (both). Focusing on high damage with large projectiles, it is unlikely to ever win a flight shooting competition against, say, Ottoman or Korean style bows that are primarily built with speed in mind. But when a Manchu arrow strikes within its effective range, it strikes with greater force."

[williwaw]

People often say that there is more stored energy underneath the belly of that curve...  If this was true a hill style bow with a relatively flat dfc would have no energy at all... I believe there should be a better way of defining it... If you have a hill style and a high performance recurve and they both weigh 50# they have the same potential...  It's how they deliver that potential... 

shredd,    when considering stored energy, my understanding of "area under the curve"  includes the red area in the pic below.  Do you mean something different when you say a hill style "would have no energy at all"?

[avcase]

I took a close look at the Manchu bow force draw curve, arrow mass, and arrow speed, because the performance seemed too good to be true.  There are definitely some major errors in there somewhere. As others have observed, the force values jump around in very odd increments.  When I smoothed this out, I get close to 100% dynamic efficiency.  This breaks the laws of physics.  This means the arrow mass is incorrect, or the arrow speed is incorrect, or both are incorrect.  Or another possibility is that the scale used to weight the bow has some serious issues.  It is probably all of the above.

One more issue.  The string used is a pretty heavy B50 string. The energy lost to propelling the string and energy lost due to the elasticity of the string alone will add up to more than a few percent dynamic efficiency loss.

Alan

[Mad Max]

Alan
It may be that you can't get a accurate DFC on a Horn Bow.
The sinew keeps stretching and horn compressing when drawing to each inch for the DFC and the B50 also.

[avcase]

Natural material bows sure can be a challenge. I have tested and measured draw force curves on quite a number of horn bows and all-wood bows, and it does require some extra care. These bows will start to relax if held close to full draw for any length of time, and this gives a false impression that the weight gain per inch of draw is much less than it would be on a normal draw and release.  I can get pretty repeatable measurements, but it does take some extra care that isn’t as critical with the glass bows.  This is why I was playing around with building one of these automated force-draw measuring devices similar to the one that started off this thread. It would be great to be able to have something like this that can measure the force draw curve in the few seconds that it takes to draw back and let down the bow.

At our flight shoot events, we have to verify the draw weight of each bow just prior to each round of shooting.  I have had a 45# bow gain 5-6# in just 3-4 days at the very dry air at the Bonneville Salt Flats.

Unfortunately, this data on the Manchu bow seems to taking inconsistent measurement to a whole new level.  I’ll reach out to the author.  Maybe I am missing something?

Alan

[Shredd]

Yup...  I was skeptical...  That's a heavy arrow to be pushing that fast...

Willi...  I believe you to be correct...  I thought about that right after I posted my comment...  I am surprised Max or Roy did not catch that...   

[Mad Max]

 

[Roy from Pa]

We caught it, waiting on you to catch up dats all..

[williwaw]

Shredd,
It might seem a small distinction to make, but when you start figuring efficiencies, using the total area would make a huge difference. anyways.... a slightly different question I hope you can shed some light on

So I don't think the limbs are storing more energy... I think it's how the limbs deliver the energy stored...

when considering the delivery of energy into the the arrow, it seems to me you have been suggesting one can "see" the difference between an efficient limb and an average limb by the shape of the curve, or possibly the shape of the area above the line?

[Shredd]

We caught it, waiting on you to catch up dats all..

   Suuuuure..........   

Willi....  Curves are nice and fun to look at...  But I like looking at the numbers...  If you have 10% of your draw weight at 28" or higher in the beginning of your DFC that's good...  11% or higher that bow is smoking...  And you want under 5% at the 28" mark... I don't concern myself with Dynamic efficiency, stored energy and kinetic energy...  I look at the curve, read the numbers and run it through the chrony...  I never made time to learn about the other stuff and I am not sure if it can help me build a bow faster... Those things seem after the fact...
   I am undecided about the middle of the curve...  I am not sure what numbers are best yet and how the limb can effect those numbers...  So much more to learn....

[williwaw]

11% or higher that bow is smoking...

Ok,  lets use that as an example.    my bow pulls 50# at 28", and 11% of that is 5.5#, so if the bow is a smoker, I should see it pulling 5.5# in the first inch?    the "in the beginning" part is unclear to me.

and the gain from 27" to 28" should be,   5% of 50, or 2.5# or under?

[Shredd]

  Yes Sir...   You hit them numbers and your limbs are not too heavy and are bending right you will be ripping that arrow...

Excuse me for my lack of ability to communicate my thoughts so they could be understood correctly...

[williwaw]

thanks shredd,

is your investigation of stacking in the interests of performance or smoothness or accuracy? I notice the target guys seem to go for longer bows than you typically find here.

[Shredd]

If you are talking about my new thread, I wanted to simply find a guideline or rule of thumb...  I want to know where the red line is and put some kind of number to it...

[mmattockx]

If you have 10% of your draw weight at 28" or higher in the beginning of your DFC that's good...  11% or higher that bow is smoking... 

Ok,  lets use that as an example.    my bow pulls 50# at 28", and 11% of that is 5.5#, so if the bow is a smoker, I should see it pulling 5.5# in the first inch?   

This is an interesting idea to have as a guide for early draw weight, thanks for sharing that one Shredd and thanks to williwaw for the clarification.


Mark

[williwaw]

If you are talking about my new thread, I wanted to simply find a guideline or rule of thumb...  I want to know where the red line is and put some kind of number to it...

not sure if it's a red line, but a smoothness thing to some.  and consider that stacking is raising daw weight without putting the extra energy into the limb or arrow, so if you were considering efficiency, it would be a concern.
 One way to look at it is if stacking is not beginning to happen at the drawlength you are pulling, then maybe your limbs could have been shorter or bending different

[Shredd]

  Yah kinda lost me Willi...  Maybe you can give me an example in numbers how bow efficiency is measured and how I can use that to make a faster bow...  If it makes sense to me I could use that as a tool also...

[Buemaker]

Interesting stuff.