Long draw Longbow stack

[Jeff Freeman]

Ok I've got a question about 30" draw Longbow and " stack "

[Jeff Freeman]

I want to build a 68"  straight longbow for a 30" draw. But I run into a lot of poundage increase in the last inch. From 29-30"
 I have been running a total of .004 tapers, .040 back .050 on the belly with a 17" riser. Fadeout width of 1.20 max.
Do I need more tapers,less tapers or a longer working limb and go with a 15-16 riser????

[Jeff Freeman]

Id like to make it smoother draw in the last  1 -1/2
28-29 is fine but that last inch or more. It's really adding on the poundage.
Any thoughts or suggestions 😀👍🏼

[Longcruise]

Add a P Lam that extends about 5" beyond the fades and a tip wedge that runs down the limb about 5" below the nocks.  You could also go with a total taper of .003 with The P lam and the tip wedge but that might not be needed.

I do a 68" 1.125 at the fades, a 15" riser with .003 total taper and the same glass front and back that you use and a full length arc of reflex of about 1.25" with no wedges.  It easily draws 30" without stack but next time around I'm adding a P lam.  I'll be doing one of those up in a few weeks and I'll let you know how it works out.

[bwatters]

The last bow I made like that was for my brother and he draws about 31".
I used 2 thou taper overall and it worked quite well, however it was around 35# so take from that what you will.
Specs were:
0.040" glass back and belly
2 x 0.100" maple tapers (1 thou)
1 x 0.080" maple parallel
(for a total of 0.360" stack and 0.002"/" of taper)
68" long with an 18" riser, somewhere around 1.25" at the fades tapering down to just under 0.5"

Theoretically dropping the taper rate from 4 thou down to 2 or so should help keep the outer third of each limb from bending too much and hence should give you a bit more draw before the string angle hits that magic 90 degrees.

[Stagmitis]

Hey Jeff I think you need a longer working limb. If you dont want to go the route of a 69-70" bow I would shorten the riser quite a bit and increase the rate of taper.

[Jeff Freeman]

Stagmitis, that's what I'm thinking about. Shorting the riser, down to 15" ? That would give me more working limb. JF

[Stagmitis]

That would work or 14". My risers are typically shorter than that but you could always begin the tapers further out mimicking a longer riser.

[Kirkll]

It would be helpful to see the shape of your bow coming out of the form first of all, then some braced and full draw pics on your tiller tree.  Without seeing how the limbs are bending, its tough to make suggestions. your limb geometry often makes a big difference.....

I use a 20" riser and a 30" double ended power lam that extends those fades our 5" , and i use a tip wedge too. With an .004 forward taper i can get a 32" draw from a 66" bow without stacking. a 68" length isn't needed.....Only time i will shorten that riser is if i'm dropping below a 62" length.

Kirk

[Jeff Freeman]

Guess I'll have to build a tiller tree and find a space for it.

[Kirkll]

I can’t imagine building bows without a tiller tree…. But a lot of guys do it, or have done it in the past. I think I built my tiller tree right after the first couple  bows I built.

 But it can be done without it…. If you use an 18” tiller stick to hold the bow in a partially drawn position you can study the bend, make tiller adjustments and map the limbs easily.

I had a ball playing with different limb pad angles and different limb shapes and learning how all of these little things combined with taper rates, material types, and width profile all effect the draw cycle…. It’s a pretty large learning curve, but can be very satisfying, as well as challenging.

For prototyping limb design you can’t beat a take down design , and use an adjustable riser. Just changing the limb pad angle alone and increasing or decreasing the pre load using different string lengths can determine the potential characteristics for your limb shape…..

With TD limbs, once you have a form built, just shifting the stops where your wedge is located can change the whole limb’s dynamics. As well as your tip notch location and limb lengths…… it’s endless… 

Once you find what you are looking for in terms of draw cycle and performance, then reverse engineer the TD bow into a one piece, and save a whole bunch of form building.     Food for though….    Kirk

[Stagmitis]

Jeff I reread your initial post and noticed that your bows are wider at the fadeout than what I build so im not sure how usefull my post is. 
 
Kirk how wide are you at the fade for the reccomendation above?

[Jeff Freeman]

Mine are just barely over one Inch.  Plus a max of .100

[Kirkll]

msg3028149]

Jeff I reread your initial post and noticed that your bows are wider at the fadeout than what I build so im not sure how usefull my post is. 
 
Kirk how wide are you at the fade for the reccomendation above?

My rough riser thickness is 1.5” that typically comes down to 1.25” then I run a straight width profile from riser to tip width of 1/2” . Limb fades are about 6” to 7” past the riser on my TD version (long lean wedges) So at that point, I’m probably about an inch at the fades.

My one piece with the 20” riser fade to fade has a 5” power lam extension and simulates the same characteristics as the TD model. Here is a look at my riser. fades. Both the TD and the one piece I use an .004 FT and tip wedge.

Btw…. I always trap these limbs to the belly about 5 degrees through the working portion, and a bit more at the tip transition.

[Stagmitis]

Gotcha! I found that moving past the 1" 125 Thou starts to get out of deep core territory

[Stagmitis]

Kirk i was responding to Jeff and you posted before I hit the enter button Lol

[Kirkll]

Gotcha! I found that moving past the 1" 125 Thou starts to get out of deep core territory

I’m kind of curious what you meant with this statement about “moving past the 1” 125 thou” and getting out of deep core territory…    What exactly do you mean by this?

[Stagmitis]

Deep core narrow limb as in a Hill style bow compared to a wider limb with a greater glass to core ratio.

[Kirkll]

Thanks.... i understand where you are coming from now.... But.... Glass to core ratio alone is a deceptive thing... Different long bow characteristics are much more dependent on limb shape prior to stringing, riser and fade lengths, a taper rates used, and shifting wedges  to manipulate the length of the working limb, and the location where the limb stores the energy. 

I can build an exact Howard Hill replica you could not tell the difference in when strung that provides a HUGE gain in performance and no hand shock.... Funny thing is.... I did this 10 years ago and the HH cult wouldn't touch them.... I never took a single order for them... This was because of the unstrung profile wasn't straight.... I guess they use those things as spears on occasion....    The second reason was they shot the arrows too fast, and didn't have that "Thump" after the shot..... You know... that hand shock that requires holding the bow just right so you don't loose your dentures after the shot.... "You gotta learn how to shoot these bows." was the common response to hand shock issues.... Well.... i gave up trying to cater to that crowd, and took the offering off my website. I haven't built one in many years...

Getting back to core to glass ratio..... This is a key factor in a bows performance from one bow to the next.... a 60# bow vs a 30# bow has a large difference in core to glass ratio using the same thickness glass on each one. The 50-60# bow will always out perform the 30# at the same GPP arrow weight.

Trying to get two identical bows to perform the same at the same GPP arrow weight at different draw weights and draw lengths is very tough to do without matching core to glass ratio.     Kirk

[onetone]

Got a kick outta your HH cult story Kirk!