stack in selfbows?

[Dan Jones]

A while back I decided to see if I could make a self-bow from board lumber.  I have now successfully made several bows from Home Depot red oak and maple boards.  I'm pleased with them . . . except for when I take them out to the range.  Both bows stack very noticeably in the latter part of the draw.  I  have assumed that not all self-bows stack, so unless stacking is in fact a characteristic of self-bows, it must be something that I'm doing wrong.  The draw weights are both right around 30# @ 28".   I draw 28."   I backed the bows with linen cloth and reinforced the tips.  One bow has limbs that are tapered from the riser to the tips; the other has limbs of the same width down to the last 10", which is tapered.  I'm stumped and I will be pleased with any light that can be shed on this question.  Thank you.

[Terry Green]

No, selfbows don't automatically stack.  Stack has to do with tiller.

I'm not versed enough to say much on Selfbows as I have only built 2.  I heard for years that your 1st selfbow would fail or come in under weight, so I set out to prove that wrong and did. My 2nd on didn't fail either.

Maiden Voyage - 53@28 when finished, probably 57#s now....

Bear Necessities - 48@28 when finished, probably 52#s now...

[Roger Norris]

How long are the limbs?

[Dan Jones]

Red oak bow - overall length- 70"- limbs both 30"   maple bow- overall length 70" - limbs both 29".  I did my best to tiller the bows with Krewson's "Tillering Gizmo."

[Terry Green]

Dan, no worries on your tiller.  You do the best you can do.  You can have the perfect tiller.... but if its tillered to 26"s and you are drawing 28 its gonna stack.  Make sense?

Just make sure you tiller it to your draw or little beyond.  That's the delicate part.

[Burnsie]

At 30# and 70" it should be fairly resistant to stacking- hard to know without seeing it.
But Terry is correct, self bows are not inherently prone to stacking unless they were tillered as such.

[Dan Jones]

As best I could I tillered both bows to 29".  My 79-year-old draw length is 27 1/2".  Since two bows have the same issue, it seems to me stack must have something to do with my workmanship. but I just don't know what.  Probably tiller.  Thanks to all for the responses.

[Terry Green]

Dan, again, your tiller could be PERFECT, but to a measurement less than your draw length.  You can't tiller a bow, any bow, to 28 and then draw it to 30 and not expect is to stack. Stacking is caused by tillering to the incorrect of the shooter.  Most bows being tillered to 28 inches stock caused them to get bad raps from those that draw 30.  If you have a 30 inch or more draw, its best to get a custom bow as  most all stock bows are going to stack at that draw length.

[Roy from Pa]

I've made about 100 bows from wood and bamboo, even trilams with a red elm core lam. I tiller all my bows 1 inch past their intended draw length. It's all about the tillering process and getting the limbs balanced equal.

[Possum Head]

Good info. Nice work Terry!

[Pat B]

Can we see a full draw side view of the bows? Generally stack happens when the string angle at full draw hits 90deg. Seeing the full draw will show that string angle.

[eminart]

Are these straight-limbed bows? Are you accustomed to shooting recurves only?

[charles m]

All designs will stack if drawn passed tillered length. No design is exempt from stacking.  You have your answer, you just need to tiller to your draw or a smidge longer.

Best of luck! 

[Dan Jones]

To Eminart:  Straight limb longbows 70" - but some set has occurred since shooting them. 
'll
To all: I gather that the remedy is to try to re-tiller the bows - and try to do it better than I did the first time. Thank you to all who responded to my inquiry.

[Terry Green]

Dan, if you have them tillered already, just back the tiller up to just past your draw length.... that's all you need to do to rid the stacking.

[Kirkll]

I haven't messed with self bows at all, and have stayed with composite backed bows.... But i've built a lot of different bow designs and pretty much understand limb balancing...

But you guys talking about tillering a bow for a certain draw length got my ears forward... Could someone please explain in detail what the difference between tillering a bow for 28" and a 30" draw would be?   

Im sincerely interested .... Thanks,   Kirk

[Pat B]

Kirk, if the tiller is good at 28" it is probably good at 30" as long as the selfbow is exercised out to 30" and then the selfbow is long enough to handle a 30" draw. A selfbow doesn't necessarily stack at full draw. Most selfbows increase in draw weight 3# to 4# per inch from brace to full draw and beyond as long as the tip angle(angle between the bow tip and string)is less than 90 degrees and the wood can withstand the strain. Tip angle beyond 90 degrees doesn't bend the limb more but pulls against the limb lengthwise causing the stack.

[Roy from Pa]

Kirk, when building bows from all wood it's a different animal than all glass limbs. You can't hurt a glass bow but you can hurt a wooden bow. So when making a bow for someone or myself, I need to know what the shooters draw length is going to be so I can balance the limbs to that draw length. Then I will take it 1 more inch of draw length just to be safe.

[Terry Green]

Here y'all go.....

This is what I went by when I tillered my bows. My 2nd bow was 'facet' tillered per Dean.  I'll post a pic in a bit....

http://www.bowyersedge.com/organic.html

[Pat B]

Dean's "Hunting the Osage Bow"is a great selfbow building guide. Dean had a way of explaining the whole process and then throw in the hunting stories to back it all up.