American flat bow efficiency

[Fox]

How efficient is a American flat bow? With no set or reflex? What speeds would be expected from a 26” draw at 50# certainly enough to kill a deer. But how does this bow compare to a recurve or a R/D or a higher stress design?

[bownarra]

Wood can only take a certain amount of strain. The wood doesn't care what design it is in Unless you build a bow too wide/thin then they all see similar strain. Really that is the goal as a bowyer
An American flatbow is a slightly modified pyramid design - it will be plenty efficient if you do a good job of tillering.

[simk]

What is plenty? 
In my bowmaking I found that a more complex design with somehow reflexed ends or pronounced levers will always outshoot a very classic straight bow by around 10fps. straight bows here go up to 175fps, more complex designs up to 185fps at 10gpp - these are my personal benchmarks.

[RyanY]

I can’t answer the original question but I think it’s possible that we haven’t seen the best possible straight limbed bow performance. We’ve probably gotten very close but it’s rare that designs are built and tillered in such a way that a limb has totally even strain along it’s whole length. The typical American longbow taper of parallel limbs results in areas of higher and lower strain. Same with a typical straight line taper pyramid bow with circular tiller. I wonder if it’s possible to squeeze out a few more fps with even, low strain resulting in no set with a perfectly matching width and tiller profile. Probably not 10fps more but who knows.

[Badger]

      I think about 165 fps at 26" draw with a 10 grain per pound arrow would be excellent for a straight limbed flatbow. One thing funny, in my experience I could take a good shooting 28" draw straightbow and test it at 26" and it would have a very big drop compared to a bow that had never been pulled past 26". It doesn't have to be that way but it usually is.