virtualbow

[Miguel Gasso]

Hello,
I reproduce my next bow in Virtual bow but Im not able to understand the meaning of some curves like the stress grafic.
I can send my file to an email, this type of file are imposible to share on this board.
Thanks in advance!

Mig

[Longcruise]

I'm not familiar with Virtual Bow.  Can you give more details?

[Mad Max]

 

[Crooked Stic]

Virtual means online I think

[onetone]

Virtual Bow is a computer program for designing bows.

[Miguel Gasso]

Here is the link to the soft.
https://www.virtualbow.org

This software is written by one guy (Stefan Pfeifer) who is an archer too, I dont know him personally.
Im 3Dmodeler for jewellery and was involved in the develop of software as a beta tester and jewellery "expert".
Saying this, first of all I take my hat off infront of the challenge he take as a single person privat person.
Of course the soft have a few isues, smal bugs, the workflow can be optimized and so on.

Beside this I will focus on the features who are working well.

First of all, we have, a in my opinion, a nice way to combine the different layers as separated materials, considering the bond between each. Once we have done the imput we will get a static and dynamic representation of the draw cycle.
I can confirm the corect behavior of this feature. I rebuild 3 bows I have and the bow shape once stringt to bracehigh and pulling them all down to 30 inches, gives really an accurate grafic and poundage output.
So at least I will use it for a trustable prediction of the bending behavior and pondage objective, for future projects.

What Im strugeling with are the grafic representations of the stress of each layer and there conjunction, it will be very interesting be able to read this grafics.
If some is interested in this soft I will share the little bit I know for now.

[Mad Max]

AVCase did a computer design years ago, he is in to flight archery

[mmattockx]

What Im strugeling with are the grafic representations of the stress of each layer and there conjunction, it will be very interesting be able to read this grafics.

What do you want to know about the stress plot? I've not used virtualbow much at all, but I have used woodbear's flat bow spreadsheet and Alan Case's Supertiller software a reasonable amount.

Do you actually have all those layers in your bow design? The stress plot shows 2 different thicknesses of fibreglass, as well as carbon fibre, 4 maple lams and stabilcore along with an ipe handle, is that correct? I'm not sure why the plot uses arc length on the x-axis, but that looks like it is the distance along the limb from the center of the bow, though it looks like the plot goes farther than the limb length given on the main page image.


Mark

[Miguel Gasso]

What Im strugeling with are the grafic representations of the stress of each layer and there conjunction, it will be very interesting be able to read this grafics.

What do you want to know about the stress plot? I've not used virtualbow much at all, but I have used woodbear's flat bow spreadsheet and Alan Case's Supertiller software a reasonable amount.

Do you actually have all those layers in your bow design? The stress plot shows 2 different thicknesses of fibreglass, as well as carbon fibre, 4 maple lams and stabilcore along with an ipe handle, is that correct? I'm not sure why the plot uses arc length on the x-axis, but that looks like it is the distance along the limb from the center of the bow, though it looks like the plot goes farther than the limb length given on the main page image.


Mark

Hello Mark

I send you the build up I have in mind what I post before was only a an example.
If you agree I can send you the file via email and you can try it by yourself an give me your opinion.
I prefere this way because it will be very complicated to argue it via pictures. The result we get we can share it with all of this forum. Send me a PM if you will do it in this way.
Also Im interested in woodbear's flat bow spreadsheet and Alan Case's Supertiller software.
Im still looking for a soft wich can help me.
Thank in advance!
Mig

64 " Rdbow FROM BACK TO BELLY
GLASS BEARPAW 1.0MM/0.04"/ 24%
VENEER WALNUT 0.6MM/ 0.024"                                                                                                           
MAPLE H. 55#/ taper 0.002/ 2.96mm-1.34mm/0.117"-0.053"               
STABLECORE BEARPAW 45 WOVEN GLASS 0.4MM/0,016"
IPE HANDEL 18"/ 1/32" 1" FROM FADE END/ 1/16" 2" FROM FADE END
MAPLE H. 55#/ taper 0.001/ 2.96mm-2.15mm/0.117"-0.085"
VENEER WALNUT 0.6MM/ 0.024"
GLASS BEARPAW 1.3MM/0.05"/ 24%
-------------------------------------------------------------------------------
GLASS BEARPAW
119.86141 lb/ft³
5946544.9 psi

MAPLE H.
44.011612 lb/ft³
1830375.5 psi

STABLECORE
106.12729 lb/ft³
8702260.8 psi

VENEER WALNUT
38.080969 lb/ft³
1680986.7 psi

IPE
69 lb/ft³
3200981.6 psi

[Mad Max]

The "rule of thumb" on the fades, are 1/16" @ 1" and 1/8" @ 2"
why so thin?? Just asking

[Miguel Gasso]

The "rule of thumb" on the fades, are 1/16" @ 1" and 1/8" @ 2"
why so thin?? Just asking

Ups you are ride it was my mistake written ot down of course 

[Mad Max]

 

[Kirkll]

Oh ya..... I remember all the "air bows" that Allan case did with super tiller. They are definitely cheaper to build than real bows. 

Unfortunately.... The best limb designs for storing energy and performance using super tiller were very unstable vertically in real time practical application, and varied a lot at different draw weights.

 I think hands on experience building these things is way more accurate in terms of  accumulating usable data and tweaking the design parameters.

But you guys have fun building your Air Bows....

[Miguel Gasso]

Oh ya..... I remember all the "air bows" that Allan case did with super tiller. They are definitely cheaper to build than real bows. 

Unfortunately.... The best limb designs for storing energy and performance using super tiller were very unstable vertically in real time practical application, and varied a lot at different draw weights.

 I think hands on experience building these things is way more accurate in terms of  accumulating usable data and tweaking the design parameters.

But you guys have fun building your Air Bows....

Hello Kirk,

First of all, Im not interested in Air bows.
I know well what you try to make me understand from my own profession. I have had a few apprentice in my workshop and each of them have had his own way to reach the objectives.
Knowledge and experience are not opposite to each other.
Unfortunally my brain structure need some way around. It was a rock in my shoe since I can remember.
I will be thankfull for every advice I get from you and a few more profesionals with vast experience like Kenny, Big Jim, Clay Hayes . Believe me, Im taking notes about every thing I can get in my notebook and KirkII is often cited, because experience is a level I did not have in this craftsmanship.

[Kirkll]

I spent the majority of my career in construction dealing with a lot of different kinds of engineers. I did a lot of my own design work and drafting, as well as existing plan alterations over the years too.

One of the hardest things to do was to get these engineers out in the field and share the practical experiences that the carpenters have in actually building things. It’s no different building bows either….

 Mathematics has its place, and can be fascinating with all the new software programs creating graphs and simulations. But there will always be inconsistency when dealing with matrix assemblies mixing composite with wood. Learning how to manipulate these inconsistencies with hands on experience and log your findings  for future projects is the key to becoming a successful bowyer.


Then you have your self bowyers that depend totally on hand eye coordination and tricks they have learned over the years on how far they can push it, and  manipulate a piece of wood before it fails. These are the masters that should be recognized more. It’s a dying art form.

I have a question regarding your bow design software. Is the limb travel distance, string length, and tension on the string at brace height factored into your findings?

[Miguel Gasso]

I spent the majority of my career in construction dealing with a lot of different kinds of engineers. I did a lot of my own design work and drafting, as well as existing plan alterations over the years too.

One of the hardest things to do was to get these engineers out in the field and share the practical experiences that the carpenters have in actually building things. It’s no different building bows either….

 Mathematics has its place, and can be fascinating with all the new software programs creating graphs and simulations. But there will always be inconsistency when dealing with matrix assemblies mixing composite with wood. Learning how to manipulate these inconsistencies with hands on experience and log your findings  for future projects is the key to becoming a successful bowyer.


Then you have your self bowyers that depend totally on hand eye coordination and tricks they have learned over the years on how far they can push it, and  manipulate a piece of wood before it fails. These are the masters that should be recognized more. It’s a dying art form.

I have a question regarding your bow design software. Is the limb travel distance, string length, and tension on the string at brace height factored into your findings?

I agree totaly with you when you say:
"One of the hardest things to do was to get these engineers out in the field and share the practical experiences that the carpenters have in actually building things. It’s no different building bows either…."

I will give the soft a try building 3 bows acording to his prediction and we will see if there is a consistent statement in poundage, efficiency, arrow speed, stress factor, etc. we can use to make a prediction. I will accept deviations but they have to be constant.

And now to your crucial question....humm I have to to take a look.

1.limb travel distance
yes, you can see the distance on y axis and deformation of the limbs in realtime,you have a slider to choose the position.

2.string length
the physical string length is one of the basic settings, its that what you mean? Also the physical properties of the string and the number of strands

3. brace height
yes you can choose the brace height for calculating the energy the arrow takes, for the speed calculation and also the final efficiency of the bow

4. tension on string
here im not sure if you mean the force  in lb applied on the string. If yes  the soft do it

[Kirkll]

I certainly wish you luck with consistency and your building experience. I've built hundreds of these things over the years, and still get a few that leave me scratching my head missing draw weight badly doing everything the same on a tried and true limb design....    

But what i found out about trial and error building, is that many times great gains are made with trying to save an ooops! bow .  Those really heavy draw weight bows that i narrowed up the width profile on, and sanded a lot of glass, turned out to be some of the highest performance glass backed bows i ever built.

There is a fine line between limb strength and limb stability and you find certain limb designs do better or worse at different draw weights. It's very difficult to evenly match core to glass ratio, mass weight of limb, and string tension at brace height from a 40# bow to a 60# in the same limb shape.  Some perform better at longer or shorter draw lengths too. But.... all this can be manipulated with experience.

I would highly recommend using vertical grain rock hard maple as a good consistent core material with good longevity, and EA 40 epoxy for your glue. It's been an industry standard for many years...

But most importantly.... Have fun in your pursuits, and good luck to you....   Kirk

[Miguel Gasso]

Hi Kirk,
Is rock hard maple, the same as hard maple( suger maple)?

[Kirkll]

Hi Kirk,
Is rock hard maple, the same as hard maple( suger maple)?

Yes.... here ya go.

https://www.wood-database.com/hard-maple/

[mmattockx]

I have a question regarding your bow design software. Is the limb travel distance, string length, and tension on the string at brace height factored into your findings?

I can't say for virtual bow but Supertiller and woodbear's spreadsheet both give you that info.


Mark