Main Discussion Area > Flight Bows
Arvins 62" osage design
willie:
sleek, I have added a screenshot and instructions for widths in the first post. The yellow bow design is used to generate the stress curves and bend shape posted in reply 2,
one can have the backshape either more pryamid or parrellel requiring less width, and by changing thicknesses, still be able to control where the limb will bend and consequently, be stressed the most.
--- Quote ---bending limb before it gets stiff
--- End quote ---
the transition from bending to stiff is gradual with most all bows, unless one sets out to deliberatly design a lever bow.
A bigger question is how should the best part of the limb work? should one try to keep most of the bend toward the inners? towards the mids? keep the inners and the mids working as much as possible? etc.
the screenshots shows the stress plot of a limb that works
mostly in the inner
inner and mid equally
mostly mid
sleek:
I ran my formula with the numbers you gave me and the dimensions are exactly what they need to be for the poundage.
I have opinions on the profile of a bow, but being uncertain of their accuracy, ill only say what I firmly believe to be true. The more you stress the inner limb, the more torque you get, the more you bend the outer limb, the more horsepower you get. The limbs profile AND length needs to be built according to those goals. Longer gives more torque shorter more hp. Which, is a large reason my shirt bows have a hard time keeping up with Arvins long bows in shooting broadhead, but also why his long bows struggle against my short in flight.
Selfbowman:
--- Quote from: sleek on December 16, 2024, 10:24:15 am ---I ran my formula with the numbers you gave me and the dimensions are exactly what they need to be for the poundage.
I have opinions on the profile of a bow, but being uncertain of their accuracy, ill only say what I firmly believe to be true. The more you stress the inner limb, the more torque you get, the more you bend the outer limb, the more horsepower you get. The limbs profile AND length needs to be built according to those goals. Longer gives more torque shorter more hp. Which, is a large reason my shirt bows have a hard time keeping up with Arvins long bows in shooting broadhead, but also why his long bows struggle against my short in flight.
--- End quote ---
If agree Kevin.
willie:
--- Quote from: sleek on December 16, 2024, 10:24:15 am ---I ran my formula with the numbers you gave me and the dimensions are exactly what they need to be for the poundage.
I have opinions on the profile of a bow, but being uncertain of their accuracy, ill only say what I firmly believe to be true. The more you stress the inner limb, the more torque you get, the more you bend the outer limb, the more horsepower you get. The limbs profile AND length needs to be built according to those goals. Longer gives more torque shorter more hp. Which, is a large reason my shirt bows have a hard time keeping up with Arvins long bows in shooting broadhead, but also why his long bows struggle against my short in flight.
--- End quote ---
I agree about an agressive side profile stressing the limbs more, especially recurves that are getting the tips out ahead of the handle.
From playing with Virtualbow with various reflex and deflex arrangements, I am seeing more energy being stored in the inner halfs of the limbs and not as much as I had previously thought being added by bending the outers more. That said I have just been playing with 62" bows and havent really spent a lot of time with longers designs - yet.
below are two graphs available in virtualbow that show the amount of curvature in the limb:
the first at brace and the second at full draw. you can move the slider and watch the curvature change as you "draw" the bow.
Looking at the stress graphs sort of tells you the same thing, Maybe the dedicated curvature graphs with its exaggerated scale helps some visualize better. I can see the usefullness for someone who mainly builds glass laminates and tillers by tapering lams before glueup and doesnt often do a lot of sanding and trying to change the bend by eye after the fact
Using the shape view to see the changes in curvature after making a tweak to your model is not that easy, (for me anyways), especially if there is a lot of reflex or deflex
Selfbowman:
🤠🤠🤠just a guess but less mass in thickness he fades from ramps to mid limb. Thin the tapper
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