lengthening bow design

[fujimo]

i have a few glass bow designs, that i would like to lengthen, to suit my 31.5" draw
i see two ways of doing this:
1.whilst keeping the tips and the handle in the same relation to each other- does one simply "stretch" the design?
which would create a limb with less deflex and/or less reflex, but the relationship between hand position and the reflex and deflex exactly the same.
or 2. does one simply add to the limb length( proportionately of course), keeping the reflex
and/or deflex angles the same- but landing up with the reflex in a different position relative to the riser.

looking at how Roy builds bows of different length, on his adjustable form, it seems like the first method is more desirable, but with deflex and reflex angles changed- how does that effect final performance?

thanks all.

[monterey]

I got no answers for you Fuj, but I have the same questions!

[Bvas]

This is my limited education guess.

I would think that proportionally increasing everything would give you the closest performance on a longer bow. By this I mean if you were to take your template and throw it in the copier and enlarge by 110%.

That being said, some measurements would not increase by the 110% such as width and limb thickness. Thus the performance would still differ slightly.

I’ve often wondered how bowyers can offer a design in several different lengths. To me, they may be similar designs, but will be two completely different bows.

[Mad Max]

Recurve
If it was a take down you would make the riser longer and keep everything the same.

A one piece, I would make a power lam longer and same fade taper as the riser fade taper.

And keep the riser length and fades the same.
If it's only 2" longer I would not worry about more reflex.

My 2 cent

[Crooked Stic]

I would think a longer draw would want a longer working limb. Does your now design show a lot of stack at the 31.5 draw length?

[fujimo]

yup a few of my designs shoe a bit of stack at my longer draw.
thats the way i am thinking, Crook!
i need to lengthen the limb sections- just trying to figure out the right way to do it.
to my way of thinking, My first thought would be better:
"1.whilst keeping the tips and the handle in the same relation to each other- does one simply "stretch" the design?
which would create a limb with less deflex and/or less reflex, but the relationship between hand position and the reflex and deflex would stay exactly the same."

 but really dont want to screw things up with some of my recurves, i just worry about the loss of performance.

[Crittergetter]

I try to go with option 1.  However I have just added length to the limbs on one design with "ok" results but you gotta be careful and not get the tips to far ahead. Everything is a trade off. I personally feel if the design is good then just enlarge it to meet your desired requirements. IMO

[Crooked Stic]

I assume you are talking longbows? Adding an inch to each end is probably not gonna change performance a lot either way. But may get you better for draw length. More than that you may want to stretch out what you have now. adding an inch may call for a tip wedge to get string angle. Ok now I see recurves mentioned. I would strech them out on a one piece. On a TD lengthen the limb on the butt end for the first two inches
. After that strecth out the design.

[fujimo]

thanks all!
only way for sure i guess- is to start doing, and stop talking    :D

[monterey]

Take some pitchers too.

[fujimo]

roger that mate!

[LittleBen]

I would go option 1 if it's a highly reflexes design like the short bow you sent me, otherwise with option 2 you might end up with so much reflex that you get limb instability.

With a very mild longbow you could probably do either and get away with it, but option 1 seems like the safer bet in all cases.

Let's have a serious talk here Wayne. With a 31.5" draw, you should be smoking arrows no matter the bow! Don't sweat a couple FPS.

Haha good luck and get some pictures up when you make a decision.

[T Folts]

I don't think you will notice any difference in just moving your string notch 1 inch on each limb.
The difference would be hard to notice unless you shot it through a chrono with a shooting machine.
You could also just simply add a tip wedge to help with the string angle. Its going to cost money either way to make a new form or try to work with what you have. See if it gives you what you need before building a new form.

[fujimo]

one of the designs i want to lengthen a wee bit, is the super short static tip recurve, like i sent Little Ben..
yup T Folts- youre correct.
nothing for nothing i guess   :D   sadly!.
i think i will just have to build a new form and work from there.


thanks all!!

[fujimo]

Yup Ben, just splitting hairs i guess. just want to get the science right!!

the long draw has its pros and cons, calluses on my knuckles is a definite con!!.
short bows are an issue, short arrows are an issue, but arrow speed is a pro i guess!!

thanks!