Arvins 62" osage design

[Selfbowman]

Sq inches in the back of the working limbs for no set. You said you wanted more hands on proof . Just trying to help you out.🤠🤠🤠

[sleek]

Oh yeah, Id like to see that tested and tried to be proven wrong. Got to have honest trial by fire. If Im right it will stand to scrutiny, if nkt, i need to know.

[sleek]

Sq inches in the back of the working limbs for no set. You said you wanted more hands on proof . Just trying to help you out.🤠🤠🤠

Whats the dimensions of the bow he is building. Ill try and calculate how much set i think he will take.

[willie]

Now I wonder what virtual bow says about your hypothetical bow Arvin? Im curios to check my work against that. It would be fun to have a bow build off competition between my formula and the virtual bows design.

Virtualbow doesnt "say" much, it's more of a visualizer for your inputs, but I would be happy to plug in your design if thats what you are asking.  can you supply a thickness description? 

1. assuming a straight taper, I would need the thickness at the point where the handle dip ends and the full bend begins along with the distance of that point from the center of the bow.   And the thickness at the nock.

2. if the taper is not straight, then additional info will help.  Its easy to  change the thicknesses once the end of the dips are located to see different results.

should I assume the same recurve at the tips as in Arvins model above?

[sleek]

I have no thickness description unfortunately. The thickness of the bow is determined by how stiff the wood is, and that I cant calculate. So, i leave it to the bowyer to determine as they tiller it, and as there is no draw length given by Arvin, one could only guess. That said, the draw length and thickness are not important to my equation, because they arent a factor in set and how much surface area a bow requires to be a certain draw weight. You can assume a 28 inch draw if you like to fill the requirements of virtual bow program.

 The design i ran for Arvin is based on working surface area alone. the stiff tips, the recurve etc are not relevant, as that is again, a factor of tye bend radius, determined by the bows thickness.

If there is a way you can plug in generic numbers or just leave them as variables to be determined by the numbers I gave above, it would be nice to see.

[sleek]

Now I wonder what virtual bow says about your hypothetical bow Arvin? Im curios to check my work against that. It would be fun to have a bow build off competition between my formula and the virtual bows design.

Virtualbow doesnt "say" much, it's more of a visualizer for your inputs, but I would be happy to plug in your design if thats what you are asking.  can you supply a thickness description? 

1. assuming a straight taper, I would need the thickness at the point where the handle dip ends and the full bend begins along with the distance of that point from the center of the bow.   And the thickness at the nock.

2. if the taper is not straight, then additional info will help.  Its easy to  change the thicknesses once the end of the dips are located to see different results.

should I assume the same recurve at the tips as in Arvins model above?

Basically ai leave the thickness to be determined by the final bend radius the bow has, as you tiller it toward your draw length, never drawing past your desired draw weight. So, thats a fancy way of saying... idk?

[willie]

So, thats a fancy way of saying... idk?

yeah, Thats the traditional way of tillering.  If you wanted the program to help you could measure a bow you have, or since you eyeball your bend while you tiller, would comparing two bends in a screenshot of the program help?

[sleek]

Its my opinion that if this hypothetical skinny long bow were to be built, it would be tillered so that the strain is even across the whole bow. If the program can tell you what tiller would look like with even stress, choose that tiller, and the draw length, then the thickness should sort itself out?

[Selfbowman]

Ok 🤠🤠🤠it would look like a yummy bow. Never mind.

[sleek]

Im sure it would perform better. And the tiller would not resemble one. Just the length and width would be reminiscent of a yumi.

[willie]

87.3 ntn  1" wide 
I estimated some values for a thickness taper that produces equal stress for as far out along the limb as I could.  you cant take equal stress all the way out to the tip.  The resulting bend profile or shape plot is as expected for equal stress.  Stress and strain go hand in hand.

Virtualbow is just a visualizer.  The program does not calculate any limb dimensions for you.
It does predict stress and bend radiuses for whatever you input as widths and thicknesses, and will calculate the draweight once you supply a MOE for stiffness. and
It is up to the user to watch that the stresses do go too high and cause unwanted set,  and the user will need to make allowances for any limb crossections other than rectangular.

woodbears spreadsheet works differently as you need to plug in estimates of the materiel stiffness and set a factor for limb crossection (round to retangular), a strain factor to hopefully prevent set,  and an elasicity factor if you are working with a highly or lowly elastic wood, and some values for relative stress should you want stiff tips or a stiffer handle rather than a circular bendy handled bow.

Next you try various thickness tapers, and the spreadsheet will calculate the approiate widths to suit your givens. If you plug an impratical design into the spreadsheet it will simply show you that you are asking too much of the wood by outputting 6"wide limbs sections or some such.

[bjrogg]

I have been trying to read all the information and it is very interesting. I haven’t really had enough time to do it justice but wanted you to know I am watching.

Really neat project. I have to admit it’s probably a little over my head, but I understand the basic mechanics.

Like Arvin said the pictures are nice to study too. I like the idea of the project. I will be watching

Bjrogg