Step 7: Tillering

Picture of Tillering
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Here's where it really get's scary, we are gong to start bending the bow to get a smooth curve. We need a tillering stick, i just took a 3 foot piece of 2x4 and cut slots every inch, suboptimal, but workable.

So put the bow on the stick and start pulling it back, you want a smooth even curve, you can see my outer limbs are too stiff, so I'll scrape the belly (string) side to thin them. Keep working until you have a tiller you're happy with.

If at ANYTIME you hear cracking, STOP, get a new piece of wood and go back to step one.
xifirus2 years ago
When putting the bow string on how far back do you pull the bow back when tillering to judge the length of string needed.
yutzwagon5 years ago
How long should the bow be left at each "step?" An hour or two, or a like day? Wait, I think my brain is working now. Do you pull the bow back to each step and check the curvature of the bow, making sure that it's smooth all the way back to your full draw length? Draw length is one's arm span divided by 2.5, right? And isn't there a way to determine a bow length from draw length, or would the old standard of height and a hand be a better choice? I'm sorry for all the questions, I'm clueless and google isn't helping :\
Tool Using Animal (author)  yutzwagon5 years ago
There's links in the very first step to forums containing infinitely more knowledgeable people than me. ;-) In no particular order. A bow like this should never be held back any longer than absolutely necessary, I might have spent 15-20 seconds at each tillering step. Pull is back, stand up, look say "ah there needs work" squat and let down. Draw length ????? Phht, use what's comfortable for you, some people pull to their chin, some their nose, some their ear. I pull 28with this, and 30 with my compound, but they require different muscles.... Length, I have no idea, except from a solid mechanics stand point that the longer the bow relative to draw length, the lower the stresses in the bow.
i have the perfect thing for this prediciment... please excuse my spelling.
arm span-- before making the bow, know your arm span. this is usually your height.
arm span=54-56inches, bow length=4 ft. 6 in., arrow length of 22-23in.
arm span=57-59in, bow length=4ft. 9in. arrow length 23-24in.
arm span=60-62in, bow length=5ft, arrow length 24-25in.
arm span=63-65in, bow length=5ft. 3in, arrow length25-36in.
arm span=66-68 in, bow length=5ft. 6in. arrow length 26-27in.
arm span=69-71in, bow length=5 ft. 10 in. arrow length 28in.
i dont have more specs than that, but those are exact for my tayloring longbows, but your flat bow here can be shorter because the flat shape can take more strain. the arrow should be drawn back to your cheek, and these specs will feel comfortable.
asarris4 years ago
Whenever I bend wood, I use a Iron (yes used for ironing) that has a steam feature and steam the wood, making it very flexible. ( I have used this to make toothpicks into pretzel shape.
seby98 asarris4 years ago
this is an excellent idea. I would watch out for warping when the water evaporates though!!
zerrodach5 years ago
What do you "scrape" with? A knife, plane, etc.
Tool Using Animal (author)  zerrodach5 years ago
A plane will take off too much, you could use a knife, I use a "cabinet scraper".
Should the bow be kept on the tillering block for any amount of time?
clownposer5 years ago
What do you mean by the limbs being stiff, i am new to this and have no idea how to tell if the limbs are too stiff.
Tool Using Animal (author)  clownposer5 years ago
If you look at the left limb, you can see it bends nicely from the handle to about half way, and then from there to the end it's rather straight, ie, it's too stiff. You want a nice continuous curve through the entire limb.
Would there be any benefit to soaking the bow before tillering, or would that result in a bow with a ridiculuos draw length or something?
HenrikOlsen5 years ago
Some important considerations while thinning is go slow and keep the cross section rectangular, especially keep the belly side completely flat,
You want to spread the compression force as equally over the width of the limb as possible, since the bow will be more likely to break if the force is concentrated in one spot.

Another consideration is that while tillering you shouldn't try to pull with a force greater than the end weight you're aiming for and you should't try to force a complete pull while the bow isn't completely tillered, since you're putting extra load on the relatively more bendy parts and the whole point of tillering is to distribute the forces as well as possible over the length and width of the legs. 
kaynegabe5 years ago
What do you scrape it with?