Trad Gang
Main Boards => The Bowyer's Bench => Topic started by: Forwardhandle on December 30, 2018, 09:43:02 AM
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I got a couple questions on stack design for you guys ,I was up in the we hours contemplating some new designs & one is that I'm going to try a zero taper in Kenny's FH design but wanted to use material on hand and I only have .030 glass so here is question 1 , say my stack is 40 lb with .040 glass and a stack total of say .271 with a total taper of .001 , will the stack be the same weight using the same .271 stack with zero taper & .030 glass ? Question 2, I plan on using plain sawn parallel lams instead of 1/4 sawn so I'm wondering weight wise how that will play ?
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.030" Glass should give you less draw weight... I am guessing close to about 3#.. Lighter glass may also give you a faster bow... I would be a little wary about .030" on the belly... I think at 40# that is getting close to the borderline...
Maybe Kenny will have some input on zero taper in his design...
If you are just gonna throw it out there and see what happens... Go for it... But if you are seriously trying to improve your bows performance I would change only one thing at a time...
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I'm just working the no taper design for the longer 64" I'm basing some of it on Kenny's exspermenting I'm going to see how his FDC works out , figuring it will lower the brace height due to the less reflex with out the supper lam & stiffer limbs with no taper , even though it's the same design this one is a design with in a design if that makes sense ,the shorter carbon ones I'm systematically doing minor changes , so maybe I will stick with the .040 glass on this for a base line !
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Sounds like fun... I love experimenting... Can be frustrating sometimes... Try to document everything... I never take enough notes and I kick myself down the line..
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You will be fine with .030 belly and front. Not .040 front and .030 belly.
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Well my post doesn't really exsplain what Im trying to do with this exsperment & using the .030 glass, what Im trying to do is get a working bow with no taper or maybe .001 so that I can work more on my concave limb design figuring I can take the concave limb right into the tips with out the wedge being there, so figuring the .030 glass will bend easier & I can make one peace lams so Im trying to simplify the procese & glue up a lot of test limbs I got the form 98% figured out , also with the lighter tips and less mass of the .030 glass for a mid 40lb bow Im thinking it would be a efficient design but really only one way to find out :dunno:
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How are you getting the concave part in your form? My guess is it would need to be perfectly centered to work right. The ACS is just in the last few in. of the tip also. A tip stiffener without the weight. I am thinking a built in lever at the tip may do the same thing.
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Mike when I get to it I will post pics, easier to exsplain that way, but the only reason Im running to the tips is the concave tips should be stiffer for a lighter weight it really doesent take much to get the effect it will be a 2 part but simple form if it works out & can be temporarly modified & transitioned back to the regular style all in one form but dont want to jump the gun tell Its tried !
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Sounds good.
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Here is probably the easeist way to try it the first exsperment with out modifiying the form but running a center shim dead center of the back glass & using the topless form with the pressure strip shimed on both outer edges but the trick is finding the right amount with out cracking the glass & lams the topless form mule tape straps will be pulled down as tight as I can , the topless form is a natural for it but every thing needs to be spot on center so will see probably take a few bows to dial in . [ You are not allowed to view attachments ]
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Only one way to know...
I bet you're tired of hearing that!! :)
fun tho aint it!!
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Yep I only know what I dont know...lol but I need to retire next year to get them all done , to many ideas and not enough time :biglaugh:
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So you are cupping the whole limb?
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Yep I was thinking that ,on the other one it cup right out side of the fades and stopped before the tip wedges why you got any Ideas ? I'm open to any thoughts ? I was just thinking it would stiffen the tips up a little more for lighter mass, with the shim method I can make what ever part of the limb cup or not I'm just continuing off what I did before ?
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When looking at a bow from the tip. Is the back convex and the belly concave, is that what the acs looks like?
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Just ran across this pic... I hope it helps in some way... Use glass with scrim... It might help keep it from cracking...
Here is something to think about... On my 64" r/d bows, if you increase the stack about .015" the bow gains about 5lb... So if you cup your limb .015" In theory it should gain about 2 lb. being you are not increasing the whole stack... So I am thinking you need to go at least .035" on your shim so you can get a 45# to have the brace tension of a 50# bow... If you can make a 45# shoot like 50# then I think you got something... And don't forget about spring-back...
The other thing to consider also... Are the ACS bows molded or layed up like a standard bow.. When you go putting that cup in your limb and then you put a bend in your limb, you might not be doing yourself any favors... The internal stresses in the limb may want to flatten out which puts you back to ground zero... If the limb is molded I can see the advantages of this design working better...
Have Fun... We'll all be watching...
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Well I have never seen a ACS limb in person , I'm making this one with the back concave pretty much with the theory Rich mentioned increasing poundage with less mass , I discovered what I'm trying to do by accident when using my topless form putting more presure on the limb edges and created a concave limb ,I'm just following up on that but on purpose...lol Makes me wonder how many things get discovered in bow building by accident :laugh:
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Yeah... I discovered fiberglass splinters real easy... :biglaugh:
Hope you don't mind my 2 cents... Just shooting some angles at you to consider and help to increase your odds to success... If you hit it big though, I want a cut... :laugh: :laugh:
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I take every body's input and appreciate it , good to see all views it helps to think things out , I'm thinking with these limbs probably the outer edges of the limbs are doing most of the tension work and the center of the belly most of the compression work, I'm assuming that by the amount of traping I had to do on the last to get any weight change but I think another advantage of this concept is how narrow you can get the limbs if the last bow is any reference I got down to 1 1/4" and thought about going more narrow but lost my nerve :o
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I don't know if you know this but when you narrow your limbs it is like changing the taper rate, it often changes the way they may bend and when they are bending optimally is when you get your best performance...
I have sanded down limbs and got better performance and got less performance... When you take 1/8" off the whole limb the tips begin to flex more because a higher percentage of material is being removed from the tips... I have not experimented to much with leaving the tips and removing more from the base of the limb... With a narrow deeper limb at the base you may have a quicker return rate but I would think with a deeper limb it may want to stack faster... Which can be a trade -off, putting you back to square one...
I just keep messing with it until I find the magic recipe and then stick with it or try making some minor tweaks down the line to see what happens...
I have found that seeking better performance is a War of Thousandth's of an Inch...
I made a bow a couple of weeks ago and it hit 187fps, rough sanded, with big 'ol wide tips... Who Woulda Thunk??? I was like... OMG this thing is gonna really smoke when I narrow it down... When I did it lost performance... What a bummer... The really sucky part is i did not take enough notes and document everything... Good info lost out the window..
I got one I rough sanded today and it is at 185... It looks like it has good potential for increased speed when narrowed up but I am not touching it until I think it all trough and document everything... Then only take it down a lb. or two at a time and check it's speed and take notes on that... It's a pain in the A$$... But it pays off later...
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Well when I narrow a bow its a slow processe for me I usally scribe pencil marks on each limb and re string and test each pass but its been my exsperience that you have to lose a lot of width to change the tiller of a bow if Im at my target weight or near I just narrow tell weight starts to drop & I do the same processe for the tips but watch carefully for string angle changes a lot has been written about light tips but it's a fine line and the gains can be minimal compared to side tillering the bow in my exsperience , Granted a lot of what I learned was from natural material bows but a bow is a bow and the same principals apply , The tips always make me stop and think because you can lose all that you gained on minor changes especially on ridgid tips I could spend a whole thread on the topic its interesting to me !
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I have been looking a bit more on the asc design and the back on their bowlimb is convex. Forwardhandle, I see that you will do it the other way around, with a concave back. I think OL Adcock must have done a lot of testing to come up with this design. I have never made such a bowlimb, but I wonder if the sideways stability will be harder to achieve with a concave back? I just wonder.
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I'm sure ol Adcock did extensive testing I think with the convex back he was trying to componsate for poison efect in the bow to and I read he had problems with limb edges splitting it could have been the material quality of the times , but my thinking with the minor concave that I end with after narrowing ,poison effect is moot with glass or glass/carbon at least that's how it's working out on my current shooter with the limbs at 1 1/4 " I'm basing this design loosely on composite horn bow limbs where they have convex shaped belles & Im putting a double chamfer on both back & belly lightening the outer edges for mass reduction I have found my current bow to be exstreamly stabil , I'm not basing the design ACS or Adocks design just used it for a analogy of a curved limb , I'm guessing the concave back is putting more tension stresses on the the outer back edges and more compression stresses on the center of the belly but so far the design is working out , maybe the bow will blow up after 1000 arrows I don't know just exspermenting ! Sorry for the winded post just trying to explain the difference !
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One of the guys at Dryad is using the ACS in his recurve limbs. He used to work with A&H kind of a spin off of Adcock. I have questioned him about different things and seems to want to help. Pretty sure he could answer any questions on the curved design.