Post by: Kirkll on July 24, 2022, 09:38:16 AM
So I’ve got this 40# bow going here that is only to be drawn 28”, and decided I’d like a bit more horsepower. I started out by using some higher yield core material and put a couple paduke cores in the stack. The outer cores are thinner bamboo lams. This paduke material always adds a bit of snap to your limbs.
The second thing I did was use an inch longer wedge to push that working portion out a bit and shorten it up….. I was a bit hesitant to do this at first, but judging by the way she’s bending, and the string angle, I’m pretty happy with the results. I definitely got a better string angle on this D shaped limb design.
This is a sneak preview of the first time on the tiller tree. She is within an 1/8” of even tiller, and about 8 pounds over weight here. Perfect draw weight for what I have in mind. I’m going to narrow up these limbs to deep core skinny whips to get my draw weight down to 40#. I’m definitely going to get some test results on this one and log my numbers for future reference.
I did manage to get the tip overlays done and some profile reduction yesterday. More to come as she comes together. Kirk
Post by: Roy from Pa on July 24, 2022, 10:41:51 AM
:thumbsup:
Post by: Stagmitis on July 24, 2022, 11:06:26 AM
Post by: Kirkll on July 24, 2022, 12:10:44 PM
I can get higher speeds messing with cores and backing, and running deeper stacks with narrow profiles, but i like the consistency of the maple /bamboo i get and also longevity, and i don't mess with carbon backing any more. So i pretty much stick with the consistent stuff and standard width profile for the most part. Over 60# it doesn't improve, but dropping below 50# it always tapers off.
I think the higher performance at 53-57# and even up to 60# has a lot to do with mass weight of limb to preload ratio. But your mileage will vary a lot depending on your limb design/shape, taper rates, and wedge configuration. Some designs perform much better at longer draw lengths than others too.
Manipulating where the energy is stored in the limb, and the length of the working portion storing that energy makes a huge difference on over all performance. The preload that stops the string dead is what regulates how much of that stored energy gets transferred to the shaft.
My strategy on this bow is to pick up some performance in a lighter draw weight at only 28". This limb design typically puts out better #s at 30" draw length, but slows down a bit with the same GPI arrows at 28"..... So i shortened the working section, used stiffer core lams, with a deeper stack than needed to hit weight so i can cut mass weight off the limbs with a narrow limb profile.
I'll let you knw how this one comes out. I haven't done any testing in awhile. I'll have to blow the dust off my hooter shooter and replace the batteries in my Chrono. LOL Kirk
PS.... If you want to build a hot rod just using glass sometime, build a 53-55# long bow using .030 glass with a deep stack & narrow profile. I wouldn't advise this on a recurve design though unless you incorporate some bias weave carbon into the core... Stability is a huge issue with thin glass backing.... I haven't build hot rods in years, but it was fun blowing stuff up going for the gold. :biglaugh:
Post by: Mad Max on July 24, 2022, 06:52:35 PM
How thick are the Padauk parallels?
I bought some Padauk a few months back, the first overlay I cut at the band saw and bent it with my hands and it broke in the middle. :knothead:
Post by: Kirkll on July 24, 2022, 09:15:23 PM
I’ve cut the working portion down about 1.5” in length and pushed the fade tips out almost 2”. I like the way she.s bending, and she’s lean and mean. This 64” bow is going to stack at 31” and could blow up at 33”. But…. It’s designed for a 28” draw.
I’ve got her balanced out at about 41 @ 28” right now, and have the full overlay portion going on the riser right now. Tomorrow she comes together and gets shaped for shooting. I’ll test this thing prior to finish sanding and spraying clear coat so as not to ding it up. Kirk
Post by: Mad Max on July 24, 2022, 09:25:27 PM
Post by: Kirkll on July 24, 2022, 09:28:01 PM
This gives you a bit of room for brace adjustment from 6 3/4 - 7 1/4” and plenty of arm clearance.
With this full overlay design, I can get a 5/8” lower brace and better preload on the limbs because I’m moving the grip forward the thickness of the overlays that give me the flush limb pockets. This is going to help out boosting performance on this lighter draw weight bow. I’ll brace this at 6 3/4” most likely.
Kirk
Post by: Shredd on July 24, 2022, 11:23:20 PM
Post by: Stagmitis on July 25, 2022, 07:48:36 AM
Post by: Kirkll on July 25, 2022, 11:11:07 AM
When you push one to its limits until she blows, it’s typically a delamination between the glass/carbon on the belly side due to compression failure of the belly lam. That’s why rock hard maple rules for belly lams.
But with that being said….. you can, and will get different results building identical bows. That is one I never could comprehend.
This one has an 1 3/8” riser pad width and is about 1.20” at the fades with a straight taper to 1/2” tips. The belly side is trapped by eyeball at about 5 degrees from the riser to the tips and the edges eased over with sand paper.
What I’m hoping for is that between the shorter working limb length, the stiffer light weight cores, and narrow limb profile reducing mass weight….. I’ll get a higher performance at a lighter draw weight.
Kirk
Post by: Shredd on July 25, 2022, 07:51:47 PM
Post by: Kirkll on July 25, 2022, 08:53:08 PM
https://youtu.be/cit1lA3Z_Mo
Post by: Longcruise on July 25, 2022, 10:23:21 PM
My hybrid long bow has done pretty well over the years. This little film clip is 10 years old. This is a 60” Sasquatch hybrid LB
https://youtu.be/cit1lA3Z_Mo
Ok, let me clarify first off, In fact emphatically clarify, that im not in any way pooh poohing your bow. But it would be more meaningful, at least to me, if it were a 10 GPP arrow at 28". OTOH, it appears that the vid was made for a specific customer and shot as they would shoot it so it's completely appropriate.
Post by: Kirkll on July 26, 2022, 01:17:13 AM
When I test a bow these days, it’s typically at the draw length my customer has.
Funny thing is …. In the last year or so I’ve built more bows with a 30-32” draw requirement than 28”.
I’m curious why it would be more meaningful to you at 10 gpp @ 28”?
Kirk
Post by: Mad Max on July 26, 2022, 07:17:11 AM
Post by: Stagmitis on July 26, 2022, 08:18:38 AM
From that event forward it has been meaningful to me to compare each others bows using that standard.
I remember years ago chasing speed in my hills- I built a 56# bow with 3/4 backset that shot 196 fps consistently but i used a VERY light arrow....Today that speed i meaningless to me..
All that being said I don't care much for 10gpp arrows and prefer anywhere from 8.5-9 gpp. Thats just a personal thing.
Post by: Longcruise on July 26, 2022, 08:56:04 AM
Quote
I’m curious why it would be more meaningful to you at 10 gpp @ 28”?
Same reason as Max and stag. But, testing to the customer's specs makes a lot of sense too. Most customers are probably not able to test it themselves.
I test at 28"/10gpp just for consistency in my own record keeping.
Come Sept 2 though I'll be holding 45# and shooting 645 grains.
Post by: Kirkll on July 26, 2022, 10:08:25 AM
The chronograph is a valuable tool for bowyers prototyping limbs and tweaking a design. But the dad burn things can cause problems with customer’s expectations too. The lighting itself can cause different readings outdoors, and measuring exact draw weights and arrow weights can creat misleading results. Using a shooting machine with a light kit and never using fluorescent lights indoors make a big difference too in consistency. The biggest issue I’ve seen over the years is people getting different results shooting by hand. 3 different guys shooting the same exact bow will get 3 different numbers…
After getting my bow designs established years ago, I got away from doing much testing. And I got tired of the thrill of victory and agony of defeat routine building hot rod carbon backed bows after awhile. Ringing the 200 FPS bell is tough to do at 10 gpp 28” draw length, but I’ve had a few bows do it at 30-32” just using glass.
About 10 years ago, Steve Tallant and I played with some excellent grade bias weave carbon with foam cores on recurve designs. That’s when I came up with my SS recurve design btw…. We both came up with some crazy fast bows doing that, but the longevity of those hot rods just were not there, and those foam core bows were loud. I think the glass spheres broke down over time after thousands of shots.
But it’s kind of fun going into mad scientist mode now and then seeing what you can come up with if ya have the time.
We had a 110 weather yesterday here, and the shop was an easy bake oven even with the big fan blasting…needless to say I didn’t get much done. Kirk
Post by: Shredd on July 26, 2022, 11:02:05 AM
What is the average arrow speed of your 50 plus lb. bows @ 10 gpp and at 28" draw and what is the arrow speed of your 40 lb. bows @ 10gpp and at 28" draw with the same exact layup?? What is the goal to reach speed wise for your 40 lb. bows??
Post by: Kirkll on July 26, 2022, 01:11:09 PM
But the lower poundage bows always taper off in performance. I would have to dig deep to give you exact test results i did years ago, and i'm really not interested in getting into any debates over those results or splitting hairs right now.
My goal here was to tweak the wedge configuration and core material in this limb design to see if i can get a bit more horse power at 40 @ 28". That's it.... I'll most likely test it at 9 & 10 gpp at 28" & 30" just for fun too.
I was just thinking that you guys might enjoy going along for the ride. I've got nothing to prove. My limb designs are solid. Purely just sharing some tinkering here.... I rarely do much testing any more. Think of it as entertainment. :biglaugh:
Kirk
Post by: Kirkll on July 26, 2022, 01:18:01 PM
https://youtu.be/t8TFk9rxg3w
Post by: Stagmitis on July 26, 2022, 04:55:32 PM
I would love to see the bow you just built run through the chrony at 28" @ 10gpp-
Post by: Shredd on July 26, 2022, 06:37:29 PM
Stag... Good things to take into account... For any new guys out there a shoot machine and fingers are two totally different animals... Like Stag said, fingers can vary alot and should never be used if you want accurate comparisons... A shooting machine is so easy to make... You could put one together in about a half a day or maybe less... I have pics on one of the threads of mine if anyone cares to look it up... If you are building bows and concerned about performance a shoot machine is a must have...
Post by: Kirkll on July 26, 2022, 08:18:08 PM
Another thing that can vary your test results is how long you hold the bow at full draw, type of string used, tied on arrow nock vs brass nock. Shooting bare shafts vs feathers or vanes…. The only way to accurately test one bow from another is using everything the same. String, shafts, and the same shooting machine.
I built a release for my shooting machine shaped like fingers one time with a button that pushed the string off a finger shaped hook. I did the same with my tiller tree hook for my scale trying to get as close to fingers as possible. That is when I realized the difference in draw weight varied slightly from a straight hook to the wider fingers hook. Not much…. But it was there…
You can really get into splitting hairs on this if you are so inclined to do so.
Kirk
Post by: Shredd on July 27, 2022, 09:41:52 AM
Post by: Kirkll on July 27, 2022, 10:32:15 AM
I do have a bit of a problem with answering detailed test result questions, and being told what is appropriate, and what is not regarding my testing procedures. I have nothing to prove to anyone, or is it my intent to do so. If the info I provide is useful and helps someone….. that pleases me a lot. If not, please don’t ruin it for others that do appreciate my efforts to share experience.
We got a serious heat wave going out here in Oregon right now with 100 degree plus days. That is limiting my shop time that turns into an oven rather quickly. So you guys that are champing at the bit will have to be patient. I’ve still got overlays to complete before I test this long bow. Might take a couple more days before I post my results.
Kirk
Post by: Kirkll on July 30, 2022, 01:23:14 PM
40@28 , 10gpp , 184 FPS , 9 gpp 188
42.5 @ 29" 10 gpp = 186 FPS & 9gpp jumped to 194 FPS (customers draw length)
Summary = Extending fades did increased performance at 28" , 29" & 30" of draw. PPI was 2.5#from 28" to 29" draw, but jumped to 2.9 PPI at 30" and was showing signs of stacking an inch shorter than normal wedge length. Test results for 30" draw was similar to 29" only 2 FPS faster.
I'm happy with it. It wasn't a huge gain, but it did bump it up about 5-6 FPS.
Shooting by hand feels smooth to 30" draw. It probably starts stacking at 31" the way the scales were reading. 64" bow length of this design typically doesn't stack until 31- 32". Kirk
Post by: Shredd on July 31, 2022, 10:21:28 AM
Post by: Buemaker on July 31, 2022, 11:04:05 AM
Post by: Shredd on July 31, 2022, 11:52:39 AM
Post by: Kirkll on July 31, 2022, 12:28:15 PM
I’ve done a lot of draw length specific lay ups with my RC and hybrid limb designs to help a customer gain a bit more HP. But…. If and when they sell that bow it may not be ideal for the next archer with a longer draw length. This is the first time I have altered the wedge length on this limb design since It was prototyped. I would do it again for 26-28” draw length request on a low poundage bow.
If I were to to start messing around trying to increase performance further in a 40 pound or less draw weight, I think I would drop the taper rate to .003 FT or even go to .002 FT to help increase the stack thickness in the working portion along with the longer wedge and lighter weight core.
The possibilities are endless…. if you are more interested in tinkering than putting out a consistent high end product, you could spend years spinning your wheels and have a shop full of prototype bows instead of refining your craftsmanship and selling the product…..
Nothing wrong with that either…. If it’s a hobby, have fun with it…. Kirk
Post by: Stagmitis on July 31, 2022, 03:45:21 PM
Post by: Mad Max on July 31, 2022, 06:47:11 PM
Kirk, dont think for a minute that coughing up your knowlege doesnt go unoticed or isnt appreciated- Thanks for posting those numbers :shaka:
Yep