Deflex--Forward Handle--Reflexed Lets talk Risers

[dbeaver]

Ive been reading a bit here and there trying to utilize good information to make informed decisions when thinking about designing a new bow form. 

I am interested in talking risers, Im keen on finding out what your definition of deflexed riser vs forward handle riser.

Id like to know your thoughts on the physics behind the draw and release of the bow, is it just a push pull between the center point of force on the grip and the center of the fingers on the string where the string pulls back to the handle and the handle back towards the string, or are there minor factors i.e. improper release, bow hand grip, poorly tuned arrow, that introduces a side to side torque that transfers to the handle?
Or is the force between the grip and string at fulldraw enough to mitigate this torque if thats the case.

Lastly, deflex, reflex, forward handle, whatever the shape of your riser, Is brace height the only thing that determines the "powerstroke" of the system where the energy transferred to an arrow for the maximum distance on the string while the limbs still have energy to give, which would transfer more energy to the arrow before it comes off the string? Does the handle position matter or is it really where the shelf is in relation to the limbs?

[dbeaver]

Not a single bite for a conversation on bows physics? 

I have my own opinions of what I've asked and was hoping for some nuance between bowyers so minor details that differ can be sorted through and discussed. 

[Kirkll]

Had to read that first paragraph a couple times to see what you were talking about…


 The torque of the bow is totally dependent on riser grip shape and hand placement, and has nothing to do with the push / pull or location of fingers on the string.
Most guys having torque issues are “Gripping the bow” at full draw. This twists the riser upon string release.

Secondly…. Your reference to a “Power stroke” , brace height, forward placed riser, and transferring energy into the arrow all in one sentence doesn’t make sense.

The power stroke is basically how long the arrow stays on the string. So yes… a forward placed riser with a lower brace height will give you a slightly longer power stroke. But a noticeable difference in performance would minimal until you start talking about the difference between a 28” draw vs a 30” draw… you will see a noticeable difference with 2 extra inches of draw length.

But…. And this is a BIG BUTT….. The energy transfer has very little to do with riser placement or shelf location. The energy transfer is dictated by string tension at brace (preload on limbs) and being able to stop the forward limb travel and string dead, and transfers the energy.

The shape of your limbs coming out of the form and length of the working portion of the limb, (The portion that stores the energy), along with the limb pad angle dictates your preload. This can mitigate  the forward limb travel distance. 

Limb travel and limb mass vs preload all determines the energy transfer rate. The only time you will see a wee bit higher performance with a longer limb travel / low preload, low brace height design , is using extremely heavy arrows at longer draw lengths. Physics wise this points at momentum being a factor…. I’m talking about a 50# bow shooting 8-900 grains of arrow at 30-32” draw length.  Your KE at impact will be higher than shooting lighter arrows at even though the arrow speed is faster with the lighter arrows.

Realistically ….. Staying at 9 -12 gpp arrow weight. You are going to find the highest performance is with a limb design that has high preload with a short limb travel with close attention paid to mass weight in the tips….. in those conditions a forward placed riser allows a shorter brace height, and will increase the preload a bit…

There’s about .05 cents worth….   Kirk

[dbeaver]

Thanks Kirk I'm digesting the info and I'm sure to be back with some questions. I for sure can't word what I'm trying to ask perfectly so thanks for sorting out what you could.