Quote from: dbeaver on May 27, 2026, 08:27:33 PMParallel core on a r/d longbow would have a lot of limb bending, possibly way too much at your wedge depends on geometry.  Limb tips would also travel farther with the whole limb bending more and no tip wedge so the limb eats up some of the energy returning to brace.  But try

I know I was was having a stacking around 28.5" with 001 taper and it was suggested that parallels would stop the tips bending as much but I did have tip wedges in those. My goal is to get to at least 29" without stack. I wish I new of a book that explained dynamics of limb taper rates, reflex-deflex, wedges, limb shape, and the effects of changing each. Like a bow simulator. Change a shim length and simulate, change a limb shape then simulate.

If you want semi-guaranteed success then ask a bowyer with known results for a form template.

Youre making your own designs without a good grasp on the design elements wanting high end results and then wishing it were simpler.  Its research and development or pay to play.  You obviously have craftsmanship youre putting good looking bows together.

Quote from: dbeaver on May 27, 2026, 09:08:35 PMIf you want semi-guaranteed success then ask a bowyer with known results for a form template.

Youre making your own designs without a good grasp on the design elements wanting high end results and then wishing it were simpler.  Its research and development or pay to play.  You obviously have craftsmanship youre putting good looking bows together.

Ya there aren't a lot of 52" 3-piece long bow limb designs out there. I have a 52" once piece design from kennym that shoot good but only hits 140 fps @29" 45lb with my hunting arrow so I would like to design one that hits around 170 with my hunting arrows. N kennym's defense he designed it to be a 35lb kids bow.
I understand that's it takes experimenting on a new design I am hoping some of you more experienced builders will help point out possible improvements. I am willing to put in the work but yes I dont fully understand the dynamics. Right now I am paying to learn.

I would love to apprentice for a local builder but there aren't any by me

I would like to see a clear non lens distorted frontal view and side view of both of your limbs so far.  They may not be working for you bilut it's an opportunity to play with them and see if you can do anything to improve your performance from there you can take anything that might be there to be learned that you can build understanding on.

It's a long process prototyping limb designs. One of the most important part is remembering that once you start getting where you want to be, & like the way the bow draws and shoots, you need to start splitting hairs to make improvements and gains. These come in little jumps in performance, and some of the best discoveries come by accident.

I learned about deep core narrow limbs being a key factor to performance gains by missing my poundage on a prototype by about 25# too heavy. Instead of throwing them in the wood stove, I took those things to the edge sander and took a full 1/2" off the width profile, and did an aggressive trap to the belly side. I was amazed with the jump it made. I went from 180 fps to 190 fps, but I found it was a wee bit squirrelly at the tips. So with this in mind, I logged all the details in my log book, then changed the taper rate from .004 to .003 and used a tip wedge. Every bow I built after that one I tested, and changed one thing at a time a wee bit. Just shifting the stop in the form an inch, or lengthening my butt wedges, all make a difference. Type of wedge material used makes a difference too.

I wasn't going to quit tinkering until I hit 200 fps @ 10 gpp arrow weight at 28" draw length. Brother... I'm telling you right now,  that is a pretty high bar. The bowyers I was working with back then referred to that as "ringing the bell" and it's damn tough to pull off without using uni carbon and bias weave pre preg carbon for stability and still get any longevity and consistency. I spent about 10 grand on carbon alone trying to beat the fastest bow in the world's record. And I built some serious hot rods doing it too.... I did reach my goal,and It was a blast!  But eventually they all blew up.


 when you get right down to it, you need stability AND durability to sell custom bows.
And I drifted away from using so much carbon, and started tweaking my designs a bit here an$ there until I got damn near the same exact performance as the carbon bows, only they held up MUCH better, and were much more dependable. I did finally ring the bell with my static tip RC design using black glass, a combination of bamboo and maple cores on a few bows here and there, but the draw weights were 57-60 pounds, and I was drawing 30" to get those numbers.

There are no short cuts. Build em, test em very accurately, tweak them a bit, and log every tiny change you make. Once you get to the point you can get no more out of it, it's time to tweak the geometry of the limb, and start all over again with limb pad angles and preload first. Just One bow form will built a dozen different bows with a dozen different test results just shifting things in the form, experimenting with different limb lengths, changing wedge configurations, and taper rates. And limb pad angles.

Once you get a  hundred under your belt you can put that bow on the tiller tree, stand back and look at it, and know exactly what it needs. You only get out, wha5 you put into these babies....   Kirk

Quote from: Kirkll on May 27, 2026, 02:08:30 PM

Quote from: Longcruise on May 27, 2026, 12:12:17 PM

Quote from: Kirkll on May 26, 2026, 08:08:17 PMLets try this again.  You put in your own info in the yellow boxes and the sheet is set up to calculate the data and give you a graph.


Copy of FD tables_blank template_new.xls

Shows up in Libre Office viewer on my phone should download and work on any device that has excel or Libre Office loaded.

i had a tough time pulling it out of my hard drive back up files, and finding the right format to save it in before it would post on the forum.  ".xls" seemed to work ok. I Just wanted to make sure others could open it.  I haven't played with DFC charts in a long time, and don't do a lot of testing anymore.  Thanks for letting me know. This universal DFC blank template should be placed in the sticky files at the top of this sub forum.

Well, sure - but exactly what needs to become a sticky: this entire thread or part of it?  Email me about this so we can do it right.

Quote from: Watsonjay on May 27, 2026, 08:41:04 PMI wish I new of a book that explained dynamics of limb taper rates, reflex-deflex, wedges, limb shape, and the effects of changing each. Like a bow simulator. Change a shim length and simulate, change a limb shape then simulate.

VirtualBow will do that for you. It is free on the interwebz and there seems to be a reasonable number of users around. It's still time consuming to go through the near infinite combinations of variables, but it is way faster and cheaper than building a set of limbs every time to see what happens.


Mark

Quote from: mmattockx on May 28, 2026, 09:51:47 AM

Quote from: Watsonjay on May 27, 2026, 08:41:04 PMI wish I new of a book that explained dynamics of limb taper rates, reflex-deflex, wedges, limb shape, and the effects of changing each. Like a bow simulator. Change a shim length and simulate, change a limb shape then simulate.

VirtualBow will do that for you. It is free on the interwebz and there seems to be a reasonable number of users around. It's still time consuming to go through the near infinite combinations of variables, but it is way faster and cheaper than building a set of limbs every time to see what happens.


Mark

I'm going to have to download that program and play with it some to see how close it is to real life experiences.  Sometimes things look good on paper or in a simulation that don't  come out so good in practical applications.

Quote from: Rob DiStefano on May 28, 2026, 06:36:21 AM

Quote from: Kirkll on May 27, 2026, 02:08:30 PM

Quote from: Longcruise on May 27, 2026, 12:12:17 PM

Quote from: Kirkll on May 26, 2026, 08:08:17 PMLets try this again.  You put in your own info in the yellow boxes and the sheet is set up to calculate the data and give you a graph.


Copy of FD tables_blank template_new.xls

Shows up in Libre Office viewer on my phone should download and work on any device that has excel or Libre Office loaded.

i had a tough time pulling it out of my hard drive back up files, and finding the right format to save it in before it would post on the forum.  ".xls" seemed to work ok. I Just wanted to make sure others could open it.  I haven't played with DFC charts in a long time, and don't do a lot of testing anymore.  Thanks for letting me know. This universal DFC blank template should be placed in the sticky files at the top of this sub forum.

Well, sure - but exactly what needs to become a sticky: this entire thread or part of it?  Email me about this so we can do it right.

We might want to just post the whole thread a rename it "Limb design discussions". There is a lot of good info, and good questions here, and it could be added to.
I can see a lot of things still yet to be discussed here.

I am going to try that program ans see if I can put these two limbs and risers in to see if it comes up with my results. Very curious. I plan on carving the nocks today and testing speed on this new limb. Tomorrow I am going to order a little scale to come up with a string tension rig. I found an old piston saying tension should be about double the draw weight for good performance. Cant wait to check these limbs

Quote from: mmattockx on May 28, 2026, 09:51:47 AM

Quote from: Watsonjay on May 27, 2026, 08:41:04 PMI wish I new of a book that explained dynamics of limb taper rates, reflex-deflex, wedges, limb shape, and the effects of changing each. Like a bow simulator. Change a shim length and simulate, change a limb shape then simulate.

VirtualBow will do that for you. It is free on the interwebz and there seems to be a reasonable number of users around. It's still time consuming to go through the near infinite combinations of variables, but it is way faster and cheaper than building a set of limbs every time to see what happens.


Mark

I down loaded that program and tinkered with it a bit this am, and i think i would argue the part about it being way faster than building limbs. yes.... building air bows on a screen will be cheaper than materials used in prototyping, but nothing will replace the tiller tree and actually shooting and testing the bow.....

You are going to end up wasting a lot of screen time only to find out its just another rabbit hole....and you are still going to have to tweak your prototypes.

Reminds me of the photos you see of a big construction project with all the owners, the Architect, and all the engineers standing around the old carpenter in the center with saw dust in his hair & a pencil behind his ear explaining to these guys why these plans are not going to work, and what changes need to be made to make it come together...  I've been in that position many times over the years, and building bows isn't any different. Nothing trumps hands on experience.

I think what would help me the most with it is to put a current limb in there and make a little change like wedge length and see what changes to save me from going down that road if there doesn't look like there will be much improvement and focus on another tactic that looks like it has better odds of improvement

Well the 2nd set of limbs is done enough. I always end up with tip twist that I have to fix and I have to process how to fix it in my head. The new limbs on the 17 degree riser hit 158 but new limbs are currently 55lb on it but old limbs on 14degree riser were 55 and only hit 145 so I think it's an improvement. I'll attach the dfc and pics of old and new limbs. The new limbs on the 17 degree see to pickup some poundage in the middle of the cycle??

I broke up the dfc charts into the 2 different limbs on the same risers 14deg and 17. The second limbs seem to help with stacking from 28"-29". Because I changed 4 features (1" longer butt wedge, additional reflex, parallel cores instead of 001ft, and no tip wedge) I am not sure what helped but am guessing it was the parallels?? The 17 seemed to have more of an issue with stacking than 14deg. Speed with 17deg went from 140 to 158 but poundage is up 4 pounds too. The 14 degree went from 145 to 160 but poundage was higher too

Quote from: Watsonjay on May 27, 2026, 09:34:27 PM

Quote from: dbeaver on May 27, 2026, 09:08:35 PMIf you want semi-guaranteed success then ask a bowyer with known results for a form template.

Youre making your own designs without a good grasp on the design elements wanting high end results and then wishing it were simpler.  Its research and development or pay to play.  You obviously have craftsmanship youre putting good looking bows together.

Ya there aren't a lot of 52" 3-piece long bow limb designs out there. I have a 52" once piece design from kennym that shoot good but only hits 140 fps @29" 45lb with my hunting arrow so I would like to design one that hits around 170 with my hunting arrows. N kennym's defense he designed it to be a 35lb kids bow.
I understand that's it takes experimenting on a new design I am hoping some of you more experienced builders will help point out possible improvements. I am willing to put in the work but yes I dont fully understand the dynamics. Right now I am paying to learn.

I would love to apprentice for a local builder but there aren't any by me

When you are testing your bows and trying to improve performance. You need to use a shooting machine and very precise arrow weight at 10 gpp and 9 gpp. into the equation.  Just saying that you were using your hunting arrows, doesn't tell us anything. You also need Exact draw length comparison that the shooting machine provides. Indoor light kits for the chronograph in a controlled environment without any fluorescent light fixtures is a must too. Those chronographs can be all over the place using them outdoors or in weird lighting. When I was getting serious about it I used two chronographs in tandem because I didn't trust just one.

Can you post some full draw photos of each limb at 28-30" draw? And give a detailed description of your wedge length and taper rate? It's tough to advise without seeing it bending.

I can get one of my kids to take a pic while I pull on my draw board.

I used 8" long wedges tapering from 3.75" down to 0 and the wedges are .35 thick. The the three pics are 7.25" brace, 28", and 30". I never intended it to go to 30" being that short of a bow. These are the 2nd limbs

This is the first set of limbs. With tip wedges, and a 7" butt wedge same thickness. I actually like the way this looks bending more, not at stiff by wedge.

Pics