Primitive Archer
Main Discussion Area => Bows => Topic started by: Selfbowman on October 10, 2024, 06:28:23 pm
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AVCase computer designed this bow for flight. I am doing the build.
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These are the drops off the stave. Going to send them to AVCase to test for bend brake and such so we can get the close numbers to feed the computer. Hopefully I can do my part on the build. Going to be fun no matter what.
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Going to give this bend a go with steam. First time with a wall paper steamer.
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Will be watching this one closely. What is the length going to be?
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Looks like a neat project. Can’t wait!
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55-56” 50 @25”
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The moisture is 7% . Should I use dry heat? I have a lot of bend to get in it is why I’m considering steam.
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looks like a lot of bend concentrated in the middle of the handle area with the way you have the thickness tapered. might be easier to go slow if you use steam
clamp a steel band on the back, (put the clamps out on out the limb a ways in the recurve area) to keep the handle back from lifting a splinter?
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Great project, nice to see a collaboration like that.
I shall be watching with interest, and a cup of tea... Emily Cat is also watching (albeit lying on radiator with eyes closed ;D )
Del
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Cool project Arvin, I have a form almost like that, it make a sweet RD bow, not sure how fast they are but very smooth shooter. I just take my time and us dry heat, I am sure steam would work but would need to have every thing set up and fast in the pull. :)
Pappy
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Decided to try dry heat. Getting there lots of bend on the outer ends.
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Very cool Arvin. I’ll be watching when I can (-P
That profile reminds me of Marc’s . If I remember correctly his might have the reflex spread throughout the limb a little more.
Bjrogg
PS we have been getting lots of work done lately so hopefully I will have some time to work on my projects in a month or so
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Getting closer.
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AVCase computer designed this bow for flight. I am doing the build.
Very cool. I look forward to seeing what you and Alan come up with. It looks like you thinned the grip area to allow all the deflex to be worked in. In the first picture you have what looks like an extra piece ready to glue back in there to thicken the grip back up, is that correct?
Mark
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Yes Mark it heated up and I ent right in place. Getting the glue joints tight was a pain.
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Looks great so far, Arvin. Good luck! I’ll be watching
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Yes Mark it heated up and I ent right in place. Getting the glue joints tight was a pain.
this one looks like a winner, can't wait to see it finished.
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First heat treat and handle glue up done.
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How long is the bow Arvin?
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56”
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That’s quite a pronounced deflex for a selfbow. Gonna be cool! Are you using a handle glue up section after heat treat?
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Steven Bieber of provision longbows is making some very curvy and deflexed recurves. He did a huge bend on one at the last classic I went to. I was blown away at how much bend he got with dry heat. Looks good Arvin. How do you get Alan to send you a bow design? Sounds like a good deal. (-S
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Ryan we have been flight shooting together for about five years now. Become friends and we love braking records. He’s a smart guy! lots of smart guys. I call them my Big Bang buddy’s. I will thin out the ends and heat them again.
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Just barely cracked the back. That was 3/4” thick.
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I will end up with about 1-3/4” shelf for over draw on a 24” arrow.
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Like I said tweak the ends a bit more.
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Pic
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Second heat session. Tip thinned and a bit more narrow. Now bent to full recurve .
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It’s amazing what a competent bowyer can do with Osage. Looks great, Arvin!
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The Osage wizard! Looks like you got those tips to form. Looking good.!
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Looking good Arvin, should be a smooth shooter. :)
Pappy
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Thin it out one more time and heat it again and we should have profile .
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Hope I remember to watch this all the way to the test results. A computer's output is only as good as its input.
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Jim you know me. I don’t like computers . But I’m not a engineer. The design depends on the wood test to be even close. That’s why we are testing scraps from The stave . This is the only way I know to get close to the design. Then It depends on the builder. I also think that I need to ease into the tiller weight. I’m going wider and thicker than the design slightly and work toward the design. The last one I did it came out 10# light. But the sample from the stave was not tested. So we will see how the engineer and the builder does on this One.
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Just gonna drop a throwaway comment here so that this comes up regularly in my new replies listing. I wanna see how this comes along, as well as the finished product.
Crack on, brother.
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Lord willing I will give you the chrono Results in the next three weeks. The crown of in the back is throwing a monkey wrench in the mix.
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I have the profile done and need to put my string nocks in the ends. The engineer has been so kind to give me a force draw curve along with brace profile, 18” draw profile, and full draw profile. So I’m going to try to get close to thickness dimensions then follow the profile and force draw at that draw length. I have found that at 20” on a 28” draw the set comes in. So at 18” on this bow if no set and the force draw matches up . Then it will probably hit close to the 50@25”. If the design is correct to the point that no set should happen then I do my part hopefully we will have success. Has any of the computer design guys approached the tiller in such a manner with success????
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Has any of the computer design guys approached the tiller in such a manner with success????
I haven't. I trusted the design completely and just made the bow(s) to final dimensions as closely as I could, then put them on the tree and worked them out to full draw. IIRC, the maple bow I did this way I did actually do a bit of fine tuning on the tiller in the end, but very little. The red oak lam bow I just exercised out to full draw with no touch ups at all.
The big questions (for me, maybe not you and Alan) are how consistent the wood is in matching the bend test samples over the full length of the bow and how accurately the bow is made to the design dimensions. If these two things are good then you won't need more tillering than very small fine tuning adjustments, if anything at all.
Using laminations helps with the consistency of the material properties, but I don't think you are allowed to do that for your flight bow.
Mark
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Mark did you do a force draw before or after or both. If so how accurate was your force draw computer design to final bow?
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Mark did you do a force draw before or after or both. If so how accurate was your force draw computer design to final bow?
No full F-D chart, but the draw weight was bang on for the maple bow I did. I played around with preloading the lam glue ups in the red oak bow and ended up a fair bit heavier than predicted because I had no way to quantify what the preloading effect was going to be.
Mark
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Mark part of my problem I think is that you glue up reflex and deflex in your bow and I have to heat the limbs to get mine. The heat may change the woods property’s . That being said if the force draw design and the bend design match up in the end . Could we not tiller to draw weight and bend design no matter what the woods properties are???? Also Allen did test on the wood. The density was 85 so my Osage stave is a good grade. The growth rings are even in thickness pretty much through out the length of the stave.
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The red line is my design thickness at this time. I got to narrow the width some . Then it will still be heavy but may be able to brace it. Will bracing to heavy cause set?
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Pic
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Could we not tiller to draw weight and bend design no matter what the woods properties are???? Also Allen did test on the wood.
Yes, the actual wood properties don't matter much as long as they are consistent throughout the stave. Doing bend tests on the drops should get you close enough to be 98% or better of the design results unless the wood is really inconsistent. Heating it to bend may alter your properties, but osage seems to be super tough and resilient to every sort of abuse, so hopefully it doesn't change too much. With the stiff handle design the heat there shouldn't matter, it's more the recurves that may have a noticeable change.
The red line is my design thickness at this time. I got to narrow the width some . Then it will still be heavy but may be able to brace it. Will bracing to heavy cause set?
If the weight comes from excess width it won't cause set, if it comes from excess thickness it could. When I did my maple bow I used a set of vernier calipers to get the thickness as close as possible to the design amount, measuring down to at least 0.005". Width is more forgiving, because it doesn't cause extra strain in the wood.
Since it's Allan's design I would ask him what he thinks of this, but I would say you want to get the thickness as close as possible to the design value and then do any tillering adjustments on the width if you can. Thickness determines how much strain the wood sees for any given amount of bend, width just adds or subtracts weight without changing the actual strain the wood sees.
Mark
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I got the tips all done time to tiller.
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Thickness determines how much strain the wood sees for any given amount of bend, width just adds or subtracts weight without changing the actual strain the wood sees.
Mark
Perhaps the most important fact of bow design.
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Not understanding. I’m thinking the wider the load is spread out more. But yes thicker will take more load.
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Thicker wood will bend less before starting to take set. Thin wood enough and you can bend it into a circle--though it will have almost no strength.
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Have it strung. Will start tiller tomorrow.
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Pretty good alignment.
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looking pretty good, Arvin
will we have to wait until september to see how it shoots?
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Lookin sweet
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That's looking really good Arvin, can't wait to see how it turns out. :) As far as bracing heavy, I always do and just go very slow inch by inch from there. :)
Pappy
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Willie I will test a 200 gr arrow through the chrono when I get it tillered.other than that next September.
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It’s getting interesting! I got the print work done. The bow is close but not perfect unstrung. The thickness numbers are not working out. But I think it’s the heat changing the wood . I’m going to try checking all the other numbers. I will see if the tension at brace matches the calculation from the computer at brace and check the force draw at 10-12-14” when I tiller if it’s still good at 18” of draw then it will probably hit close to weight at 25” full draw. I’m GUESSING🤠
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Again has anyone out there tillered a bow by profile and force draw curve before!!!! I think they go hand in hand. That’s going to be my approach on this because the thickness is not working.
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I beg your right about the heat changing things. It may settle in pretty close when you finish up tiller after all said and done in the end but for now I’m betting it’s off because of that. It’s pretty darn close for unstrung profile though! Nicely done.
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Ok pattern for tiller done.
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That’s going to be my approach on this because the thickness is not working.
What is not working on the thickness?
Mark
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Getting close. The numbers are hitting real close. Been to 18” . Profiles are almost dead on. The last seven inches will tell the tail.
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The thickness numbers are not working out. But I think it’s the heat changing the wood . I’m going to try checking all the other numbers.
was the bend sample heatreated the same as the bow limbs?
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That handle build-up is fantastic!
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Got it to 24” and the recurve ends pulled out about a 1/2”. For my first try at tillering force draw weight to bend profile I’m pretty happy. I will try heating the ends but not real hopeful on that. I will say that you can tiller bend profile to force daw though. I will test the bow tomorrow.
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Willie I don’t my know but I think not.
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Willie I don’t my know but I think not.
What does it mean? to tiller to force draw? Does it mean you simply hit a certain weight at different points as you approach full draw? I would think this might be a good way to come in light if something goes just a little wrong, like set for instance.
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Steve it means I did not test the sample Allen did and I don’t know if he heated the sample.
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260 gr. 200 fps 48@25” 3/4” set
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Arvin I think steve is asking about what your are calling force draw.
some folks like to plot what the poundage is at each inch of the draw after the bow is finished
https://cari-bow.com/wp-content/uploads/2014/02/extra-energy-stored-from-recurve-design.jpg
and the chart is typically called a force draw curve.
Did Alan send something like that before hand which is hopefully what you will end up as?
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Yes Willie I tillered the bow to the force draw that he projected while meeting the bend profile at the projected draw weight. It was close till the bow took set.
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It may not have met your expectations Arvin but still a very cool build.
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Took the words right out of my mouth Dave. Really cool looking bow. Got me thinking I’d like to try one sorta kinda like it. Need to make myself a reflex/deflex form.
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Yes Willie I tillered the bow to the force draw that he projected while meeting the bend profile at the projected draw weight. It was close till the bow took set.
thanks for the explanation, Arvin. Now I am curious how he projected the force draw curve. Are you free to post a pic of that curve? It seems like a method I have not tried or heard of before.
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Now I am curious how he projected the force draw curve.
Alan's software will output that curve.
Mark
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Ya mark it’s amazing to me how he dances with that computer. I’ve got Allen doing a design that I want to try. Shorter version of my longbow.
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I’m going to try the bow. If it don’t work out it could maybe make a blind hunting bow for BJ.
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I’m going to try the bow. If it don’t work out it could maybe make a blind hunting bow for BJ.
You should get good distances, I'd think you can break 300 yards. Whats the speed with a 450gr arrow?
I think you were 25% underbuilt. Id like to see this exact bow made 25% wider and compare.
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Pics.
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Total mass 19.9 oz.
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One more pic
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You sure build a sweet bow Arvin.
Mark
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There is no doubt, Arvin can sure carve a pretty stick.
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Very interesting build Arvin. I do like the projected full draw profile. Sure would be a sweet little hunting bow, but I’m hoping it does everything you want it to.
Bjrogg
PS I don’t see any set except at the tips?
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It happened about 14-18 from center of the bow.
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It happened about 14-18 from center of the bow.
Ok I see it now. Interesting nice build Arvin. Nice numbers. I will be watching to see how far she flings a arrow for sure.
Bjrogg
PS start digging sugar beets tomorrow morning 5:00 am. Our last crop left to harvest. Then maybe I can do some tillering on the blanks you sent me
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Congratulations on the fall harvest . Hope you get good prices for you crops!
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That's an amazing looking bow.
I made a deflex like that a few years ago but didn't progress it because I was scared I would pop the crescent out of the riser. Could be an irrational fear though. Did you put dowels in it?
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No dowels. Smooth on epoxy. My fear was a string braking and the glue joint failing in a dry fire. Thinking about reducing this bow to 35# draw and letting a lady try for a flight record with it.
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No dowels. Smooth on epoxy. My fear was a string braking and the glue joint failing in a dry fire. Thinking about reducing this bow to 35# draw and letting a lady try for a flight record with it.
you dont have high hopes for it at #50? why?
if you reduce you will leave width and length as is?
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No dowels. Smooth on epoxy. My fear was a string braking and the glue joint failing in a dry fire. Thinking about reducing this bow to 35# draw and letting a lady try for a flight record with it.
As you drop weight, speed test it in 5 pound increments, also try to start introducing reflex when you hit 35.
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Willie I will test it . If not looking good I will reduce in thickness and narrow the outer limbs but leave the length the same. That’s a coming from me. AVCase May have a different idea. Keep following the bend profile as close as possible. That’s my present thinking.
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Far more certain to succeed if you reduce only the width. 30 percent narrower should put you at about 35#.
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Reducing the width is a great way to reduce draw weighr, but only if the bend radius isnt over stressing the limb. Considering the ser this bow took, its safe to say thickness reduction would decrease bending stresses, allowing the draw weight to match the bow width more. That combination should increase bow speed and efficiency.
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Jim I respect your suggestion and would go with your recommendation if I was making it for a daily shooter. I agree with sleek on this one. I was told by Badger that it was toast for flight. Damage already done. So I’m just thinking on this for awhile.
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We missed you at flight this year Arvin. Can't wait to see you next year breaking a record with this thing. I've also been toying with modified designs from the Greyson Museum collection from the golden age of flight here in the 1940s and 50s. I'm only going for records I don't have yet. This year I was 8 cm short of the 50# simple composite. For that one, I just need to brush up on my form. Want to bring a 80 or so pound bow for the unlimited class.
Take care
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We missed you at flight this year Arvin. Can't wait to see you next year breaking a record with this thing. I've also been toying with modified designs from the Greyson Museum collection from the golden age of flight here in the 1940s and 50s. I'm only going for records I don't have yet. This year I was 8 cm short of the 50# simple composite. For that one, I just need to brush up on my form. Want to bring a 80 or so pound bow for the unlimited class.
Take care
I'm absolutely convinced that you will accomplish your goals. I'm looking forward to seeing what design you come up with and watching the progress. You and Arvin are my heroes. :)
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Chuck I missed being at the shoot also. I heard it was a good one. I just barely broke the 50# complex composite record. It’s not easy shooting farther than a guy from Hungry . Stop trying to push that arrow another 5 feet and you will brake that record?🤠🤠 missed seeing everyone most of all. Great group of people from around the world!
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After studying the bow more I realized I had left the last 6”” of the limb was to wide . I left it wider till I got my string groves in. Then the dumb cowboy forgot to narrow them causing the set at 18-19 inches from center of the bow. I narrowed the ends allowing the recurves to work more. The set stayed but the bow shot 199 grains 226 fps. So had I followed the design it would probably been spot on. It may still compete if I get good clean arrow flight.
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After studying the bow more I realized I had left the last 6”” of the limb was to wide . I left it wider till I got my string groves in. Then the dumb cowboy forgot to narrow them causing the set at 18-19 inches from center of the bow. I narrowed the ends allowing the recurves to work more. The set stayed but the bow shot 199 grains 226 fps. So had I followed the design it would probably been spot on. It may still compete if I get good clean arrow flight.
How much extra width was there? It doesn't take much to screw things up if you have everything right to the limit of the material. Great news that you found a reason why things went the way they did. Not knowing what went wrong is far worse.
Mark
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Mark I took off about 1-16 inch off each side from tips to nothing at 5-6” length. It was enough to make a difference for sure. Making working recurves in all wood bows are a challenge to say the least. I learned from the build though. This is my second try at this if I don’t run out of good wood staves that will make good candidates for a build I might get this right yet. The next one I will get the engineer to give me projected bend profile every 4” of draw length. I noticed the force draw and bend profile came real close to the design. Mark do you have both force draw and bend profiles in your design? And if so would you check the profile design vs force draw on one of your bows and see how it came out. I’m curious about this because thickness will be a lot less of an issue when tillering.
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Mark do you have both force draw and bend profiles in your design? And if so would you check the profile design vs force draw on one of your bows and see how it came out. I’m curious about this because thickness will be a lot less of an issue when tillering.
Arvin,
I'm not really equipped to do an F/d chart on my tillering tree and I've never compared the bend profile of a bow to the predicted one. The last lam bow I did I was using Perry reflex to try and improve performance and I have no good way to include that in the analysis, so the bow I made was not really identical to the design version. When I get done building a garage and other infrastructure projects I would like to do some bows without the Perry reflex, just to see how they compare.
The design equations used are well proven to match reality, though, so as long as the bow dimensions are accurate and the wood properties consistent throughout the bow there is no reason for me to think the design and the actual bow won't very closely match each other in the end.
Mark
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Arvin,
if you are going to build another and want computer program input, I would be willing to do a follow along that demonstrates how to use visualbow.
we could collaborate your design finetuned with the program, and post the work as we go, all in the same thread.
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Willie I Am not sure I’m capable of doing what you are talking about because of my lack of computer skills. I’ve built from architectural plans my whole adult live and can follow plans pretty darn close. That being said I’m willing to give it a go. So far I e found building from force draw curve and bend profile was the easiest for me. Getting close to plan dimensions in thickness and going from there. Being a unbacked selfbow it’s near impossible to get your thickness spot on. You have to be close to the plan dimensions in he beginning to achieve the end results in my opinion . So it has to be a collaboration of dimensions and bend profile and force draw .
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Arvin,
there was a thread a while back about using computer programs, and I thought a followup workalong might be nice to demonstrate how to use Virtualbow. My contribution to the project would be......
demonstrate how anyone can test a ripping from the stave on the tiller tree, in order to arrive at more precise numbers to plug into Virtualbow for the actual build.
demonstrate with screenshots how I will plug your design ideas and test results into the program and show how different options or changes will affect the design, say for instance if you want to change limb lengths, widths, recurve, deflex or reflex.
I’ve built from architectural plans my whole adult live and can follow plans pretty darn close.
Before computers were used to draw plans, we used to scale from plans to get dimensions that were not specifically noted, the success of doing this depended on the accuracy of the draftsman. Now a days computer drafting has made some things easier and better, but sometimes the way the plans are printed out means problems can be introduced unexpectedly.
I think Virtualbow can generate a force draw curve, but I do not have the technology at hand to print and mail full size bend profile curves. Visualbow will output these profiles at any draw length and actually let you move a slider a draw the bow to any drawlength on the computer screen. and screenshots can be made and posted to help "eyeball it" for comparision. Maybe someone with printing equipment available can help if full sized bend profiles are desired.
Anyone that wishs to follow along could load the program on their laptop, but it will not be neccesary for you to do so unless you want to.
Being a unbacked selfbow it’s near impossible to get your thickness spot on
yes, with an unbacked selfbow, the back crown or a rounded belly complicates things. Virtualbow was primarily developed for use with FG laminated bows and can easily work without the FG lams so long as the limb crossection remains retangular. when crowned backs and bellies are part of the design, some adjustments will need to be made in the calculations thus starting thick will be prudent. how much extra thick will depend on our success at estimating the "adjustments". perhaps some additional work with the proposed test specimen will get us fairly close.
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I would really like a thread like that, it would help me understand better how to design a bow specifically for any stave
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Willie avcase has the force draw and bend profile in his computer format. He may be willing to share That with you. That needs to be worked out between y’all cause I’m not so smart so to speak.🤠I’ve got a couple of good staves left that I can get the backs almost flat. 2” wide. One almost 3” same wood as my broadhead record bow. Coming in a bit thick at first tiller I can hit the profile and force draw pretty easy. Well real slow and easy.🤠I’ll get with Alan
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Arvin,
I think we have the force draw curve covered. I will double check when I get home this weekend.
The thing about full sized bend curve drawings is the special printer need to make 3 foot prints with accuracy. I am guessing that is something Alan does where he works. And there is also the file type that the bow program generates to feed to the printer....it has to be compatible. I will look at that also when I get Vbow installed on my new laptop.
The wider stave sound like it may make it easy to get the test sample or maybe more, unless...
Were you hoping to get 2 bows out of it?
Do you have access to a nice table saw? A shop type table saw with a decent fence will work with care. The important thing is to be able to rip a slat with a uniform thickness. I will take post some pics of doing it on my saw with a stave I have here and work out some test sample dimensions if you want to move foreward.
The general plan is to rip a thiner slat and make a few test samples, something that can be tapered to a point on each end. A long dimond shaped bend in the handle pyramid mini bow if you will. Then do some bend tests on the tiller tree and use Vbow to reverse design and give us good numbers for the wood. Actually a bit of time spent on the test sample will be worthwhile. Doing some testing on the sample at the working moisture content and testing again after the sample sees some heat treatment and possibly rounding the slat to approximate the crossection of the finished bow and testing a third time.
Do you have a decent scale for the tiller tree that can read weights down to ounces? a digital?
I would really like a thread like that, it would help me understand better how to design a bow specifically for any stave
Take a look at https://www.virtualbow.org/ for its capabilities and for a peek at the visual outputs.
If you have difficulties installing, please post as if I remember correctly, some guys had it working well and some had install issues a few years back when there was a similar discussion.
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I’ve got a architect that can print 32”by long as you want. I just need the design in a folder emailed to me and I have the nice lady move email from my phone to the printer. Just need to do it in 1” scale for me. That’s about as high tech as I get.
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Do you have access to a nice table saw? A shop type table saw with a decent fence will work with care. The important thing is to be able to rip a slat with a uniform thickness.
Depending on the thickness you want, a table saw may not be accurate enough. I use a thickness sander to get consistent thickness on my bend test samples and a decent surface finish to prevent lifting splinters during the test.
Mark
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Do you have access to a nice table saw? A shop type table saw with a decent fence will work with care. The important thing is to be able to rip a slat with a uniform thickness.
Depending on the thickness you want, a table saw may not be accurate enough. I use a thickness sander to get consistent thickness on my bend test samples and a decent surface finish to prevent lifting splinters during the test.
Mark
making the thickness of the sample to a given thickness should not be an issue (within reason), as the sample length can be adjusted to fit. manufacturing the sample to a consistent thickness side to side and end to end will be the most important part, and getting a good measurement of that thickness also.
Hopefully we can make a number of measurements as the build progresses with various conditions of the sample, (at moderate stress levels of course), and if murphy is on vacation when we conduct the final test for set taking, we can get good info to plug into the program.
Having a few test samples on hand will also be nice for various tests.
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Just need to do it in 1” scale for me.
I got the latest version of the VB downloaded and working. the latest version does works in pounds and inches etc. earlier versions only did metric.
It claims to be able to export files in .csv files. I will have to look into that more to see how useful that could be for printing. The latest version of VB also claims to be able to overlay photos on the graphs it makes within the program so one can make comparisions to the results and the predictions sort of like some of the pics guys post here on the forum sometimes.
whether or not full size drawings of bend profiles happens or not is somewhat of a different project.
If we never accomplish generating full size bend profiles, will that be a deal breaker for you?
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Willie I can print 1” full scale drawings at my architects office. Bend profile and force draw. It would be nice to have it all on the same page unstrung , strung, and bend profile every 4” of draw. Every other bend profile starts about ten inches from fade as to not blurry up the first ten inches. coming out or the fades.
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Do you have access to a nice table saw? A shop type table saw with a decent fence will work with care. The important thing is to be able to rip a slat with a uniform thickness.
Depending on the thickness you want, a table saw may not be accurate enough. I use a thickness sander to get consistent thickness on my bend test samples and a decent surface finish to prevent lifting splinters during the test.
Mark
After measuring some rippings, I see some deviations that would warrant a thickness sander, especially if trying to get a good sample from a stave.
I suppose if you had some sizable stock that didnt make a stave from the same tree, and you had enough to work with squaring, resquaring and re-ripping with decent featherboards it might possible.
what bend test do you use and how big a sample?
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what bend test do you use and how big a sample?
I used a simple cantilever bend test where I measured the deflection of the sample slat due to a known weight at a known bending length. The two bows I did this way were made from boards, so I cut one test piece off the board before I did anything else with it. My primary concern was measuring the elastic modulus (Young's modulus) so I could calculate the dimensions to achieve a desired draw weight. I was less concerned with finding the strain where set started, but I did do some of that for the second bow I made from red oak laminations just to get an idea of the strain limit. Because of the imprecise way wood takes set this is pretty approximate and mostly gives you a kind of fuzzy edged range of where set starts to be noticeable.
Mark
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I did do some of that for the second bow I made from red oak laminations just to get an idea of the strain limit. Because of the imprecise way wood takes set this is pretty approximate and mostly gives you a kind of fuzzy edged range of where set sttarts to be noticeable.
Mark
I wonder if the imprecision is "in the wood" or a better test method could help?
Maybe something that bends a sample to a true arc of a circle can be less fuzzy.
I might do some experimenting with test methods here that Arvin could duplicate at his place. I think he would like to design a bow that just begins to take set at full draw if I understand his needs correctly.
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I wonder if the imprecision is "in the wood" or a better test method could help?
I expect it is some of both. The biggest problem I had was determining when set had started. I'd put a load on the sample, measure how far it bent and then take the load off to see if it returned to zero or not. Because wood has some hysteresis there is always a little bit of what could be set, depending on how long you allow for it to return to the unloaded position. I would repeat this with increasing load until I clearly had set, then try to determine where set really started by going back through the test results.
Mark
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Still fine tuning. I don’t even know how many hours of the heat gun!
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Same bow Arvin? How many heat sessions you done on it?
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Same bow. I’ve lost count on the heat sessions. Reduced the width on the last 4” getting it to work more not taking any off where the set was. We will know soon if the bow does not take set again. Took .3 oz off.