need help with lam thickness.

[wyatts daddy]

I'm looking to make a 64"55#28" longbow using the longbow blueprints from 3rivers. I'm using my own lams which are parallel cut. My question is this: How thick do I go? I have verying opinions, Crooked stik made my lams for me on my first bow and he hit the poundage I wanted dead on but the problem is that he uses tapered lams. I called Bingham and was told .322 if I was using parallel lams. My riser is 18" fade out to fade out. I'm just a little nervous due to the cost I have in the wood on this one and my first bow was .475 it's specs are 66" 51# 28". I want to use bocote as the outer lams with bamboo as the core lams. The riser is bocote, zebrawood and osage accents. I would be very grateful for any help. Thx.
Bill

[Hornseeker]

I dont think you are going to get many confident answers...I am still hoping to hit weight nowadays...and when I change one little thing, I'm usually off 5-10 pounds...

Binghams is probably your best bet...

Ernie

[ChuckC]

Daddy.  it is hard to call the shots on different bow designs, especially if you change things.  I have some (but not a lot) experience with building bows and I wonder how you got only 51# out of .475.  On the forms I have, I believe I would exceed 100# with that much wood.  

Just curious (want to learn more here) why use only parallels, unless that is just what you have ?  I would think that haveing some amount of taper in there would allow for less tip weight (albeit not a whole lot less) and maybe a bit faster recovery.  

I think you will change your whole limb shape / tiller profile by changing to all parallels.

Can't wait to hear from others on this one.
ChuckC

[shantam]

i need about 0.32" for 50#@28" on a 66" longbow.
the form is a mild D/R form and i am using 0.4 glas on that one.
i suggest a overall taper of 0.3 for this.
if you do it with out taper,you end up with a slow bow with handshock.
thats my experience and might not be what others found out.
grinding a parralel lam is just as difficult as grinding a taperd lam by the way.
shantam

[kennym]

By memory,.360 @ 64" on my D/R form(own design) is 55#,.380 @ 64" is 65#.Thats the only 2 64" bows I've built,so my experience is limited. I think your limbs are gonna bend a LOT just off the fades. Mine bend more than I like using a .002 taper,we're gonna try a power lam(think thats what its called),another taper that runs out bout 5-6" past the fades on the next one. Don't know if it'll work,but heck its only money!! Good luck and keep us posted!

[ChuckC]

Hey Kenny, how about just making the riser a tad longer instead of trying to place and maintain that short taper in the mix..  
ChuckC

[shantam]

btw. im building a 66" longbow over the weekend on a new form.
if the tiller turns out ok,
i can sent the pattern and corethickness to you WA.
shantam

[Crooked Stic]

ChuckC the butt thickness on the lams I sent was .400-2 .100x,002 tapers 2.100x,001 tapers plus whatever glass was used.
I agree that with all paralells the strung profile will probably be different with all paralells. It will work ok. When you do a limb with a reverse taper setup provided you use two tapers with the same butt thickness you end up with a paralell limb thickness. The reversed taper goes on the belly so it bends around the fade curve easier.

[ChuckC]

Crooked...is that first number correct ?  .400 ?  I am not quite following...is that the total thickness of all the lams or just that one ?  That is nearly half an inch thick ! Should it be .040 as a parallel, two of them ?

Actually, it doesn't matter what the butt thickness is of the tapers, if you use a reverse taper of the same taper rate, it equals a parallel.

If you tie in those .100 tapers (as you describe above) using one as a reverse taper, have you calculated which taper is going in as a reverse ?

Please show pix of your bow when you finish it, I really enjoy discussing and learning more about this.
ChuckC

[wyatts daddy]

chuckc, On my first bow crooked stic sent me the lams for it. He sent me two .100 butt thickness with a .002 taper and two .100 butt thickness with a .001 taper. I used .040 glass. So the total thickness was .480 that bow was 66" 51# 28". My problem is that I want to learn how to make my own lams. I found a way to make parallel and I have a way to make the tapered but I need a tapered lam to make the guide for my sled. How I made the parallel lams was by using a square board clamped to my bandsaw I cut the lams just a hair over the size i was looking for due to some wood not cutting straight. I then used a drum sander in my drill press and using the same square board i clamped it to the drill press and ran a scrap pieace of wood between the wood and the drum sander until I got it to sand to the size I need. I'm going to make the tapered lams the same way but i will use a tapered lam a straight board and the lam I want tapered, run them between the board and the drum sander. On this bow I want to make it a little shorter 64" that is why I asked the question about the thickness. My riser is 18" fade out to fade out. Bingham told me .322 for the length using parallel lams. Now you said just using parallel lams will make a bow slower I don't want that should I wait until I learn to make the tapered lams?
Bill

[kennym]

Chuck,we've been kickin that around too.
Thanks,Kenny

Bill,are ya measurin your reverse tapers at the center of the bow or figuring the full .100"?

[wyatts daddy]

what do you mean by reverse tapers? i used my gauge and measured the thickness just past the fade out. is that correct?
bill

[ChuckC]

Wyatt.   Slower is a descriptor that can mean many things, from Wayyyyy (less fast) to kinda (less fast) to just barely (less fast).  I don't know which it will be, or even if it will work that way.  Some of this stuff is way beyond rocket science and some is just common sense.  

It ...seems.....right that if the ends of one bow are heavier than the ends of another, the lighter bow will recover quicker, or faster.  But, other things might also influence that, maybe more so.  

Example...in design....a Hill style bow with a very short handle  and long limbs might take longer to recover than a very short bow with a longer riser (shorter working limbs).  But...As soon as that is said, someone is gonna yell how their Hill style bow is lighning fast.  There goes that theory...or does it.  

I still am having trouble following your calculations.  maybe that is why I have such questions.  If you used .040 glass and only those tapers (were they 36" pieces ?) I add up to only .280 thickness.  Did you use parallels also ?

If you want, you can PM me a tele number and I can call you and talk some time.
ChuckC

[kennym]

Bill,I think Binghams measure lam thickness at the thickest point,center of bow or thick end of tapers,(don't think they use reverse tapers,taper turned with thin end to center of bow)

I've never used reverse tapers,so when I talk limb thickness,its:  glass + paralells+taper at thick end.

Hope this helps and I'll let Chuck take it from here cause he's doin a way better job of explainin this stuff and I'll prolly just confuse ya!
 

[Crooked Stic]

This bow in the pic has two .100x.001 tapers and two .100x.001 tapers with .040 glass. It weighs in at 50 at 26 in my design.Thats .480 butt thickness.  

[kennym]

Was I wrong!! Helped a fellow glue up a Binghams TD pronounced longbow limb today and guess what, reverse taper!! Didn't have time to mike and see if they used the same amount of taper in both,but I'll check when we glue up the other limb.

[**DONOTDELETE**]

Originally posted by ChuckC:
[QB] Wyatt.   Slower is a descriptor that can mean many things, from Wayyyyy (less fast) to kinda (less fast) to just barely (less fast).  I don't know which it will be, or even if it will work that way.  Some of this stuff is way beyond rocket science and some is just common sense.  

It ...seems.....right that if the ends of one bow are heavier than the ends of another, the lighter bow will recover quicker, or faster.  But, other things might also influence that, maybe more so.  

Example...in design....a Hill style bow with a very short handle  and long limbs might take longer to recover than a very short bow with a longer riser (shorter working limbs).  But...As soon as that is said, someone is gonna yell how their Hill style bow is lighning fast.  There goes that theory...or does it.  

I believe those really fast "Hill Style" bows you were refering to are fast due to more than than the typical amount of laminations with good tappers to the lams too..... i just read something along those lines abow Hills bows.

[**DONOTDELETE**]

Originally posted by kennym:
Was I wrong!! Helped a fellow glue up a Binghams TD pronounced longbow limb today and guess what, reverse taper!! Didn't have time to mike and see if they used the same amount of taper in both,but I'll check when we glue up the other limb.

What would be the atvantage of a reverse taper????

[kennym]

Don't know,maybe when we get this one strung up,it'll shed some light on why? I use tapers in all mine.I noticed on the sheet that came with his bow kit,the less reflexed longbow uses 1 taper and the rest paralells.?

[wyatts daddy]

Well I glued it up tonight. I went with Bocote parallels .060 on the face and the back of the bow. Bamboo core lam with a butt thickness of .100 with a .001 taper. I made the taper myself with the help of some people here on tradgang. .050 glass. Binghams told me to shoot for a thickness of .322 for the specs I want: 64" 55# 28". I'm giving it a shot. Man I hope it works out.
Bill