Primitive Archer
Main Discussion Area => Bows => Topic started by: Selfbowman on December 20, 2022, 05:21:29 pm
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New bow design somewhat.67” ntn,9” handle, 1-1/8 at fades, 9/32 at tip, pyramid. Trapped on the back3/8 total. Pretty much the whole limb.3/16” on each side. About ready to start tillering.
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Pic
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Maybe less glare.
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2-1:2” reflex
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24.2 ounces right now. Probably 3ounces coming out in handle section. Going to be interesting for me to see what the end weight in mass and draw weight will be.
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I was curious so I braced it.
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thanks for posting Arvin. I'm looking forward to seeing how it turns out my friend. :OK
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Looking good so far. Will be watching.
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Looks really nice! Should be a smooth draw. Good luck and thanks for sharing the details and photos.
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Looking great Arvin. Seems narrower than you usually build them. Can I ask why? Just curious as I'm always looking to learn.
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Bill and Steve.... Arvin is the wood guru. Now to see how far it will shoot. Elegant Arvin with no frills, and a linen string most likely. :BB (SH)
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Steve just a test. I am going to find out how narrow I can go with little or no set. Taking mass off the back making the tension weaker and the belly stronger in compression. May decrease total mass also. May blow up. We will see.
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so you are building one of your normal bows but trapping the back to remove mass? :OK
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so you are building one of your normal bows but trapping the back to remove mass? :OK
Hopefully
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I’m watching this build. Looks great so far. Keep pics comin!
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Skinny bugger
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Looking good Arvin, looking forward to seeing the outcome , looks like you got your shop up and running that;s great to see. ;)
Pappy
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Thanks for the reply Arvin. I kind of figured you were experimenting for your flight bows. Interested in your findings.
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Guys I’m thinking it takes 8 oz of mass in a limb for a fifty pound bow or there abouts. How you distribute the mass will determine the set. Keeping in mind that wood is 8 times stronger in thickness compared to width. I will cut some pieces as close to the same size as possible. I will do this at fade , mid limb and 2” from tip. I think I will do this on several bows. still need to hang my tillering board but my siding is not in yet. So I may have to hang it temporarily to tiller this bow.
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Here is bow I talked Kenny Cartwright out of its 45# at 24”. The mass is 12 oz. bend in the handle bow. I can’t wait to test this little bow. 52” ntn.
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Well the bow came in at 20.9 oz. 50@27 shot one arrow between 220-230 several times. Shot a 500 gr arrow 200 plus. It lost half of the reflex from fade to mid limb in set. Good bow. May need to do a stretch test on this bow.
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Here is the cross sections of the limbs.
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Interesting experiment, Arvin. What weight are you aiming for? I'm interested to see how it works out.
Mark
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It’s fifty at 27” right now. I’m thinking taking some more off the outer limbs and tiller to about 48@ 28 and try shooting it there. The mass on my simple composite BBO that shoots 260 yds is 18.9 oz. This bow is 20.9 oz. The handles are almost identical. I think it’s the thick bamboo backing that is lighter.both bows come in at 50 @27. I think the one ounce in each limb is the difference. I’m open to other theories.
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It’s fifty at 27” right now. I’m thinking taking some more off the outer limbs and tiller to about 48@ 28 and try shooting it there. The mass on my simple composite BBO that shoots 260 yds is 18.9 oz. This bow is 20.9 oz. The handles are almost identical. I think it’s the thick bamboo backing that is lighter.both bows come in at 50 @27. I think the one ounce in each limb is the difference. I’m open to other theories.
Are the back profiles the same on both bows? Width? Any set yet in tillering?
Mark
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Marc the profiles are very similar. The bbo has a little less trapping. It has more set in the fades and mid sections but has a bit more reflex at the last nine inches or so. The Osage bow has only been shot 8-10 times. I’ll try to get a pic of one laying on top of the other.
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Pic
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Pic
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Mark I think the main difference in the Osage bow shooting 20-30 yds shorter is the bamboo backed has less mass weight. 2 oz is quite a bit.
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Pretty impressive looking osage bow. Looking forward to see it finished up. Can't recall how long ago, but remember a post you made about adding reflex only to the outer limbs. Because of that post I made a new caul and been doing that when practical. I sure do like how bows like that shoot. It;s also easier to gauge set in the inner limb. Thanks and good luck with your goals for this one.
Mike
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That is a beautiful strung profile...very elegant. :OK It's a shame to mess with it, but I think you might be right about the extra ounce. Great job Arvin.
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Mark I think the main difference in the Osage bow shooting 20-30 yds shorter is the bamboo backed has less mass weight. 2 oz is quite a bit.
That is a fair bit, especially if it's near the tips. How narrow are the tips? Could you take some weight out there? Can you post a couple back profile pics? If you frame only half the bow in each shot it would show more detail instead of trying to get the whole bow in one shot.
Mark
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Bamboo backed bows average about 10 fps faster than self bows and will usually run about 10% lighter in mass weight.
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Here is some pics of the back. Fade , mid limb, tip.
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Mid limb
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Fade
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Pic
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Pic
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Pic
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No finish yet I’m going to take more off mainly outer limbs. Just rubbed with a shaft tamer.
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Bamboo backed bows average about 10 fps faster than self bows and will usually run about 10% lighter in mass weight.
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Steve I think your right about that. The mass weight is the culprit in my opinion.
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Bamboo backed bows average about 10 fps faster than self bows and will usually run about 10% lighter in mass weight.
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Steve I think your right about that. The mass weight is the culprit in my opinion.
I second this opinion as well based on the experience I’ve had with boo backed bows. Weight is less and speed greater.
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I love the profile Arvin. Question for you. Other than looks, what is the advantage of gluing on tip overlays? How much mass weight does the overlay add to the limb tip? In your search for more cast/distance, would the subtraction of that amount of tip weight gain you anything?
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I love the profile Arvin. Question for you. Other than looks, what is the advantage of gluing on tip overlays? How much mass weight does the overlay add to the limb tip? In your search for more cast/distance, would the subtraction of that amount of tip weight gain you anything?
I was also thinking that there could be some weight reduced at the tips...you don't need much past the string nock. Merry Christmas everyone... :)
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Well dome, Arvin! Jawge
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Thanks guys . The tip overlays are pretty small deficits. I like them and think they add to the appearance. May not win but looks good trying.🤠🤠🤠
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I do agree they look great, just wondered in your search for performance if the fraction of ounce would help contribute to the total ounces you’re looking to save.
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Oh I guess any fraction is to much . But I’m not that good yet. Probably won’t achieve that in my lifetime. Well the glue on was coming off so cut it off. I hate glue joints in a handle. Any suggestions????
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I use a toothing plane for my glue on handles. It does leave a saw tooth pattern to the glue line on each end but, my glued on handles don’t pop off any more. Basically, it’s doubling the glue surfaces.
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Any suggestions????
Glue it better next time? (A) ;D
Sorry about that, couldn't help myself. My only answer would be to re-glue it with a more careful prep the next time, but I doubt you did a bad job of that the first time around. What did you use for glue?
Your fades are pretty steep but most of that is on the glued on portion and the main bow body thickness transitions pretty smoothly from the limb thickness to the glue plane, which is where it really matters. The bow body thickness under the glued on handle also looks to be enough that the glue joint shouldn't be really heavily loaded. Maybe try smoothing the fades on the glued on handle a bit to ease that transition some more?
Just an FYI, for those that like to groove up or coarsely sand their lams and other gluing surfaces, Smooth On recommends prepping surfaces with 120 grit paper for use with EA-40 and there is research saying that a freshly planed surface is significantly better than any sort of abrasive prepped surface for bond strength. Despite what people think, glue bonds at the microscopic, cellular level in woods so what it sees as a rough surface and what we feel with our fingers are two different things. The only thing a rough surface seems to offer is voids in the glue line that might be good for avoiding glue starvation in the joint, similar to how fumed silica works to prevent the joint from closing tight.
Mark
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Will this work?
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I never go over about 64" long with a glue-on handle if the handle section is 3/4 thick. Not sure if the liquid weld is any stronger than tight bond, I know some of the epoxies are stronger.
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Only thing I can tell you is the longer the set time, the stronger the epoxy.
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I never go over about 64" long with a glue-on handle if the handle section is 3/4 thick. Not sure if the liquid weld is any stronger than tight bond, I know some of the epoxies are stronger.
If the bow is your usual 69" or even 68"... and it was only 64"... it would have to trim some weight off. So, let me know how much shipping is...send it to me...and make a shorter bow. :OK (lol)
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I’m watching Arvin. I’m interested in your outcome and what you learn from this one.
My suggestion for gluing on handle is to rip som thin laminate strips on your table saw. No more than say 1/4” thick. Then prep everything like normal. Stack the laminate’s together with glue between each piece. Clamp it good and tight. ( I use TB 2 so I clamp tight might not want to clamp as tightly with epoxy) and let dry.
The thin laminate strips will bend slightly if they have to and not pop off. You can use a couple of different wood types to make it more interesting. I’ve had really good results using this method and never had one pop off
Bjrogg
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See if I can find a picture
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The reason I use the thin strips is so the handle doesn’t pop off. You don’t have to use different wood types, but it’s an easy way to get a nice look. At least I like it.
Bjrogg
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I do the same and put a kind of powerlam as the first layer.
I had the same problems in the past when I glueed on a handle, after I switched to the powerlam solution all my handles still hold...
Greetz
Cord
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Will black walnut be strong enough? I have some bow limb laminates about 3/32” thick . And I think I will get some slower setting glue.
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I've used black walnut heartwood but it seems to be brittle to me. I like thin osage lams on an osage bow.
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Ok
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Will black walnut be strong enough? I have some bow limb laminates about 3/32” thick . And I think I will get some slower setting glue.
I have never used B W by itself. Not sure about that.
I think the combination on this one was Osage bow that was about 1/4” thicker in handle than limb. Much like yours looks. If you can have that little bit of thickness it really helps.
Then I think it was black walnut- oak- black walnut and finally a sliver of juniper
I have never had a problem with any of them but it does make filling and sanding a little challenging because of the different wood densities
Bjrogg
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Use EA40 and don't tooth it before glue up. I know you read and hear about toothing all pieces with EA40. But, glass bowyers prefer EA40 over any other epoxy and I'm quite certain no components are toothed on a glass bow :) I never waste time toothing and I have had zero delams of any sort with EA40.
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Thanks pearl I know you do them all the time. Is that like smooth on?
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EA40 is smooth-on
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Ok but I have had pop offs with it too. Maybe I need to go to a glue up class.🤠
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On my cans of smooth on ea40 it says mixing 2 parts a to 1 part B will yield higher strength results and resistance to heat. If you prep and score the surfaces well and wipe clean with acetone it will hold. If you’ve got a heat box at your disposal then even better. Bake it for 6-8 hours at 150 degrees while keeping it clamped. Best of luck.
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I would use the smooth on as recommended. I would also laminate a piece or two in between your handle or build it up with multiple laminations. I've had failures in the past where the glue lines weren't very good and I figured smooth out would make it up. It is good at making stuff up but I always use too much clamp pressure trying to get it to come together and I feel like I squeezed way too much epoxy out of the joint. I think it's easier to make multiple laminations come together without excessive clamp pressure then one block to another unless they are perfectly machined flat. I've done some abrupt transitions like that and always had better luck with multiple laminations. You are putting the stress multiple glue joints instead of just one. I also only weigh out smooth on instead of trying to do a part to part. I only use the one-to-one ratio, got sick of having extra of one part. Just my two cents though
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Thanks guys will do.
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Smooth, rough or toothed? It s always a good idea to read the directions on the glue. :) Jawge
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The thin laminate strips will bend slightly if they have to and not pop off. You can use a couple of different wood types to make it more interesting. I’ve had really good results using this method and never had one pop off
Not picking on you, BJ, as this is a common belief. There is no way that the thin lams can bend once glued into a block. As long as the glue is as stiff and strong as the wood (EA-40 certainly is) that laminated block will behave exactly the same under load as a solid block of wood of the same dimensions.
I think it's easier to make multiple laminations come together without excessive clamp pressure then one block to another unless they are perfectly machined flat.
I suspect this is the reason people have more success with laminated handles. It is definitely easier to get good glue lines with thinner laminations that can conform to the other side of the joint. Laminated handles also look great when contrasting woods are used.
Smooth, rough or toothed? It s always a good idea to read the directions on the glue. :) Jawge
Smooth On's technical info says to prep lams by planing or sanding with 120 grit sandpaper, which I don't think anyone does. I use 50-60 grit on my thickness sander just because 120 would go far too slowly and would clog and wear out continuously. It might be worth block sanding the lams with 120 grit after the thickness sander but I haven't tried that yet.
Here is a link to the EA-40 Technical bulletin that specifies 120 grit for prep: http://www.smooth-on.com/tb/files/EA40.pdf
On page 2 of the bulletin it has specific bow making instructions. It says to plane or lightly sand the lams with 120 grit paper.
Mark
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Her are some pics of the handle before the glued on piece.
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Close to enough wood for the handle not to bend I think?
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Pic
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Pic
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Hard to believe that handle could bend enough to pop off a glued on piece. But I’ve never glued up a handle before either.
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It did not pop off but half the glue joint was loose so it was going to happen . Just a matter of time. It’s not pretty if they pop and blow.
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Close to enough wood for the handle not to bend I think?
That looks fine to me. On my board bows the limb is typically ~0.400" thick just before the fades and the thickness where the handle is glued on is left at the full 3/4" of the 1x3 board. I have not had a handle pop off and all of them have been glued with generic yellow wood glue or Titebond III.
It did not pop off but half the glue joint was loose so it was going to happen . Just a matter of time.
That sounds like a prep/joint fit problem, not a glue issue.
Mark
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The fit was nice . I sand each side on my 4x36 belt sander. May have clamped it to tight and squeezed the glue out. Can’t remember I built that blank 1-1/2 years ago before I closed my old shop down. May have dried to much causing the glue joint to fail. I’m going to get some smooth on latter today and try it again.
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It really looks like you have enough thickness in the handle area from the original stave to make gluing another handle work on Arvin. I’m thinking this time around will work
Bjrogg
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I’ve found that Black walnut is just about only suitable for arrow nocks...and almost not even those, because my served strings work through them over time. I’m gonna need to burnish all of my walnut nocks.
I’ve had nothing but failures for BW tip overlays...but as handle material BW should work. I would use multiple thin strips of it, as suggested.
Black walnut is gorgeous wood, but it is just so dern brittle.
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Glue up.
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Those bar clamps are just snuged. Pearl wants lots of oozz. 🤠.
The trouble light is at about 125-130 degrees.
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Went to Sarrles Archery and picked up the smooth on and some scrap wood . Can’t remember what the wood is . I think it’s called pretty.🤠 shame it does not show more.
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Went to Sarrles Archery and picked up the smooth on and some scrap wood . Can’t remember what the wood is . I think it’s called pretty.🤠 shame it does not show more.
That's funny... :OK Can't wait to see it...
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Cleaned the handle up this morning. Hopefully we got it this time.
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Pic
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This handle came out about 8” fade to fade. I usually make them 9-10”
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It looks great...and should have trimmed a little weight off too. :OK
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Ok Bob took a bit off the tips just for you. Before and after.
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Pic
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Tip with # 2 pencil
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What does it weigh now? It looks great.
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20.8 oz
Here is a good way to check out your pyramid. I you can lay all four sides of your limbs on a piece of granite with very little light between them well you did good. That’s real even diminishing mass. Going to finish tiller tomorrow. Letting glue dry 24 hrs.
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Pic
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That's a good tip for that style...thanks. I'll bet it has a really nice profile when it's settled in and finished. I hope the first arrow gives you a new record distance. :OK
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Looking very good Arvin, that one should hold and beautiful to boot. :)
Pappy
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Happy New Year to you Arvin and all the rest of the crew... this may be the best bow of the year...
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Well no it’s not the best bow of the year. A good one yes. Now the question probably none of us can answer. The bow is still taking set it will probably end up tips and handle against the wall. By trapping the back almost 30 percent did the bow fail in compression or tension???????
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Happy New Year Bob.
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This will become my target bow till someone has to have it.
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Oh total mass weight 20.8 oz. subtract 7oz for the handle 13.8 oz in the limbs. 67” ntn the force draw is poor in the first3-4” of draw. This is due to the set it took.
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The final profile is one that makes for a sweet shooting and still fast bow. I've seen some of Badger's flight bows with a very similar profile. It will be a killer target bow. You have an interesting question about the set. It would make sense that it was due to tension, but it always seems to be due to compression in mine. Great job though! :OK Happy New Year!
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The bow is still taking set it will probably end up tips and handle against the wall. By trapping the back almost 30 percent did the bow fail in compression or tension???????
If it's taking set then it is failing in compression.
Mark
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So I’ve always heard that Osage was pretty even in compression and tension. This trapping makes me wonder how true that is. Less mass on the back but it is still failing to compression??? Explain to me in the most simple terms possible please.
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Happy New Year Arvin.
I agree with Bob. Looks like a nice shooter. Nice profile yet and I’m sure it has many years of good shooting ability.
I know your are after more than that though.
I guess I have always assumed the set came from compression and crushing cells.
I suppose it could be tension and stretching cells?
I think it is more than simply tension or compression. There’s so many things that effect set. And in the end we are dealing with a material that although very similar to each other as a species can still be very different individually.
Would be interesting to know though.
If the trapping actually caused more set. I might speculate that the back actually stretched more than the belly compressed?
Got me starting the year out thinking 🤔
Bjrogg
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Well not impressed with the speed 169. 497 gr arrow.
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I might try one more like this with thicker late rings and less early wood. Don’t know?
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With the back trapped I would lean more to tension was little compromised over the compression. Just my way of looking at it. If the back is trapped would that not be putting more strain on the back to beef up your belly a bit if one was worried about compression failing a little this could be a balance that is struck. In this case it would seem to me that unless I could see some evidence of crystallization happening on the belly I would be looking more at the back as the culprit perhaps. Could still be a bit of both tension and compression and bow has just settle in now to where it will be but if no obvious signs of compression happening I would lean to tension being the cause. Just my thoughts on it. Wet nice bow still regardless. Congrats!
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So I’ve always heard that Osage was pretty even in compression and tension. This trapping makes me wonder how true that is. Less mass on the back but it is still failing to compression??? Explain to me in the most simple terms possible please.
Without having precise measurements of your trapping I can only guess, but it is hard to shift the neutral axis much more than 10-12% with trapping unless you really go nuts with it and it doesn't look like you did from the pictures. A 10% neutral axis shift adds 10% to the tension stresses and reduces the compression stresses by 10%. Very few woods are close to even on the tension limit versus the compression limit, so even if your osage compression limit was only 15% less than the tension limit it still would have failed in compression first.
Many (probably most) hardwoods have the compression limit at 50-60% of tension, so your osage would be considered really good at 85% but still not good enough to avoid taking set.
Mark
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So I’ve always heard that Osage was pretty even in compression and tension. This trapping makes me wonder how true that is. Less mass on the back but it is still failing to compression??? Explain to me in the most simple terms possible please.
Without having precise measurements of your trapping I can only guess, but it is hard to shift the neutral axis much more than 10-12% with trapping unless you really go nuts with it and it doesn't look like you did from the pictures. A 10% neutral axis shift adds 10% to the tension stresses and reduces the compression stresses by 10%. Very few woods are close to even on the tension limit versus the compression limit, so even if your osage compression limit was only 15% less than the tension limit it still would have failed in compression first.
Many (probably most) hardwoods have the compression limit at 50-60% of tension, so your osage would be considered really good at 85% but still not good enough to avoid taking set.
Mark
"New bow design somewhat.67” ntn,9” handle, 1-1/8 at fades, 9/32 at tip, pyramid. Trapped on the back3/8 total. Pretty much the whole limb.3/16” on each side."
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Ok Mark I’ll try one trapped to the limits . Give me the the dimensions for a narrow pyramid bow similar to this one. From what I understand what you said the mass may get down to5-6 oz per limb on this bow.
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Mark I feel it’s failing in tension and here is why. I think the neutral Plane has changed with the trapping because of less mass . If we was to bend that limb the opposite way it would fail miserably I think we could all agree. The problem may be by reducing the elastic abilities or properties in the mass it’s stretch did not return to its original state. If I shoot this bow a thousand times it might fail eventually. We just can’t see the damage. I still think that perfect diminishing mass is where we will find the best performance. By adding reflex on the ends we have a need for more mass at inner limbs. It’s been a interesting build though. If thicker is quicker can we ever reduce the mass in the limbs of a 67” bow with a 8-10” handle to closer to 6oz instead of 8 oz??
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Also I have took the force draw curve pounds of one of my best bows and wrote them every two inches on the tillering tree. This bow went from 21 at 14” of draw in the beginning of the tiller to about 17#s after set came into the picture. Then at 20” of draw the bow starts hitting the targeted numbers of the previous bow. So at 20”where set usually starts is where the numbers start getting back on target for the rest of the draw. Interesting.
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Also I have took the force draw curve pounds of one of my best bows and wrote them every two inches on the tillering tree. This bow went from 21 at 14” of draw in the beginning of the tiller to about 17#s after set came into the picture. Then at 20” of draw the bow starts hitting the targeted numbers of the previous bow. So at 20”where set usually starts is where the numbers start getting back on target for the rest of the draw. Interesting.
Arvin, I think you are on to something there with the 20” draw and starting to see set. I’ve seen this as well with some of my bows. For this very reason is why I stopped tillering much past brace prior to applying sinew to my bows. I found better results with getting to just past brace height then making careful thickness measurements of each limb every 2” to get me close enough after sinew. I found that less crushing of cells on belly as I leave what mass is needed to match the tension of added sinew if that makes sense. On final tillering I remove what is not needed from the belly and round it a bit to match the crowning of back with sinew. I think better performance can be had by not overstraining the fibres prior to sinew. Anyway off topic a bit but find your observations interesting how it relates back to what I’ve found with the use of sinew. Thanks for posting this.
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Dave I noticed that at 20” is where set starts happening. So has Badger. The interesting part is noticing where it affects the force draw. So a whip need bow would show up loosing weight at the end of the force draw??
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"New bow design somewhat.67” ntn,9” handle, 1-1/8 at fades, 9/32 at tip, pyramid. Trapped on the back3/8 total. Pretty much the whole limb.3/16” on each side."
That's not really precise enough to use for calculations. When I shape my bow limbs I measure with vernier calipers to get everything as close as I can.
Back in 2007 Badger did a red oak board bow challenge. David Dewey made the only entry, designed using his spreadsheet. This thread talks about it and post #11 shows details of how he made the bow, with pictures. That's the level of accuracy you need to maintain for this to work well.
https://www.tapatalk.com/groups/paleoplanet69529/woodbear-s-red-oak-entry-t13237.html
Ok Mark I’ll try one trapped to the limits . Give me the the dimensions for a narrow pyramid bow similar to this one. From what I understand what you said the mass may get down to5-6 oz per limb on this bow.
1-1/8" wide again? I don't know how low the mass will get, but I can get you to where the entire limb is sharing the strain as evenly as possible. That minimizes the set by not overstraining any particular area of the limb. I forgot to ask, where did the limbs take set on this current bow?
Mark I feel it’s failing in tension and here is why. I think the neutral Plane has changed with the trapping because of less mass
The thing is, I have seen no evidence that wood can fail progressively in tension. In the various testing research I have seen the tension failures are always blow ups. It is only in compression it will progressively fail by taking set. If someone has data to show progressive failure in tension I would love to see it.
Mark
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Fade to mid limb. First part of the draw is affected after set. Also cast is lost at the end when the bow starts bottoming out.
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Mark my cross section looks like Steve first cross section on the thread. The cross section kept the same ratio in diminishing mass .I trapped the bow before I started the tiller. Some fine adjustment on the traps after.
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Fade to mid limb.
Now that's interesting. The straight width taper pyramid profile will overstress the outer mid part of the limb (~2/3 of the way from fade to tip) if the thickness is kept constant as most people say to do with the pyramid shape. To maintain constant thickness from fade to tip the limb sides need to be curved out a bit from straight to keep the strain the same all along.
Did you want to go with the same 1-1/8" width out of the fades or try a bit wider this time?
Mark
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Well the bow came in at 20.9 oz. 50@27 shot one arrow between 220-230 several times. Shot a 500 gr arrow 200 plus. It lost half of the reflex from fade to mid limb in set. Good bow. May need to do a stretch test on this bow.
Hello Arvin,
I just read through the 8+ pages of this bow build and have some questions. According to the statement above, you initially shot a 10 ggp arrow over 200 fps with the bow drawn 27”? The 27” draw is measured from the bow back or belly? Next, you narrowed the tips some amount, the bow started taking some set and then the speed dropped to 169 fps with a 497 grain arrow. This is drawn the same 27”? Do I have this right?
Was the draw weight with the 169 fps shot less than with the 50# draw weight measured for the initial 200+ fps shot? Of course, draw weight changes will effectively change the grains per pound for the 169 fps shot compared to the initial shot. Thanks!
Alan
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Alan the bow never shot 200fps! It shot 500 grain over 200 yds. The arrow that shot 220 -230 several time’s weighed 460 gr. When I took more mass off the ends it did not do as good at 28” the set killed the bow. I always measure to the back of the bow.
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Thanks Arvin. I misunderstood that you were talking about yards, not feet per second! Ha!
Alan
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Fade to mid limb.
Now that's interesting. The straight width taper pyramid profile will overstress the outer mid part of the limb (~2/3 of the way from fade to tip) if the thickness is kept constant as most people say to do with the pyramid shape. To maintain constant thickness from fade to tip the limb sides need to be curved out a bit from straight to keep the strain the same all along.
Did you want to go with the same 1-1/8" width out of the fades or try a bit wider this time?
Mark
Two inches from handle 11/16”mid limb 9-1/6. 2” from tip 9-16”
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The new handle glue up worked out fine.
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I peeled a bit more weight off this bow cause I like shooting it. This bow took more set than sneak peek two the wiggle bow. I think it failed in tension due to the trapping. Can’t prove it though. Arvin
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This should be your 3D bow! :OK
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Here they are together
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Arvin,
I haven't forgot about doing a bow layout for you, I've just been too busy to sit down and do it. I'm also still trying to figure out the best way to post the output when it's done.
Mark
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All right, Arvin. Attached are (hopefully) 2 pdf files of your requested bow. One shows a crappy graphic of the back and side profiles with dimensions in millimetres and the other is a spreadsheet giving the actual dimensions in millimetres and inches. This assumes the same modulus of elasticity as the samples you sent to Alan Case for bend testing a while back, so you may need to tweak the thickness a touch to hit draw weight if this piece of wood has a different stiffness than the test pieces.
The design is 67", nock to nock. Draw weight target is 50lb @ 28". It is a touch wider than 1-1/8" at the fades with the grip area 1" wide x 1-1/2" thick. The limbs are assumed to be rectangular in cross section, to the dimensions given. Don't round the corners much or you will screw up the design. I round the corners no more than maybe 0.1" (at most) on my bows and they have been fine with that.
The bow is designed using David Dewey's spreadsheet which I have found to be very close to my real world results so far. I think it gets you as close as you will find to the perfect diminishing mass as you travel along the limb to the tip. The spreadsheet only works for flat bows, so if you recurve the tips much it will throw things off and possibly overstress the outer limbs where they blend into the tips. You will be better off to reflex the whole limb in a smooth curve from fade to nock if you insist on adding any reflex. For it to work you must stay very close to the dimensions given. The last bow I made this way I found I could get within 0.002-0.003" on thickness and +/-0.010" on width and that worked.
One thing to note that is not obvious, the sides of the limbs are not a straight pyramid taper, they are bowed outwards a bit. This is correct and not wrong. A straight pyramid with constant thickness will overstress the outer-mid portion of the limbs. The limb needs this width profile to provide truly equal strains over the full limb length.
Mark
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mmattockx... Thank you. I know that Arvin has worked hard on this and your calculations will help him get closer to his perfect flight bow. You two are amazing. :OK
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Arvin, I think your bow has a great profile and the chrono reading I saw seems right on.
Your bow making skills are incredible.
Thanks for sharing.
Jawge
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Nice bows Arvin.
I always assumed that the set was from compression, but you really got me thinking about it.
I’m starting to think you might be right about stretching in tension and developing set.
My HHB seems to take more set than my Osage.
It never shows any signs of frets on the belly. Still shoots fine but whenever I get set it always annoys me.
Maybe I should try trapping the belly?
Bjrogg