Tillering Help

[caliban]

I've actually fired this on a low brace at close to full draw. It's got plenty of wallop and is quite accurate, however, as you can see, the tiller is way off. Looking at the photograph I can see the left limb is stiff and the right limb is flat close to the tip. I can afford to lose a bit of power but I'm at a loss to know how to proceed. I keep looking at the stave, bending it and marking areas to be thinned, and then flexing it and deciding that it needs to be thinned somewhere else. Help!

 

[C_Claycomb]

One does NOT "fire" a bow:AR15firin



I reckon you know what you need to do. You just gotta grit your teeth and start scraping wood off that stiffer limb. You want to go very slow, take a bit off and then re-stress the limb since the effect of wood removal can take a little time to show up. I probably wouldn't worry too much about the limb tip being a little stiff. Stiffer limb tips will mean the bow stacks a little less. Also, if the tips are thick enough not to bend much you can narrow them down a fair way to reduce mass (better speed and less vibration).

I reckon I have been in the same situation on every bow I ever made and sitting there and staring at it never made anything any better. (didn't stop me trying though!) The wood has to come off, you know how to do that, so you might as well get on with it. If it's all going to go wrong, it'll all go wrong, no point in wasting time as well as wood

 

[stovie]

mid third left limb, scrape slowly and re-brace. I'm going to assume the left limb is the lower limb...don't worry about the tips, stiff is good...last thing you want is a whip tiller...

is it a flat bow?

 

[caliban]

Hi thanks! I think you are right Claycomb, I was just letting my nerves get the better of me. I've reduced the left limb down a bit and have SHOT the bow a good few times, I know I shouldn't be doing this yet. It's quite powerful (my shoulders ache) and seems to be fairly accurate.

The bow is as tall as me and is two inches wide, so I guess it is a flat bow. This is probably how it has survived being drawn on my poor tillering.

Stovie, what difference does it make which limb is the upper limb and which is the lower?

Thanks for your help guys.

 

[C_Claycomb]

It is so easy, I find, to get caught up in tillering, and over shoot the desired weight. I have ended up sawing tips off limbs more than once in an effort to regain lost weight . Sounds like you are doing pretty well.

On English D-section longbows, the lower limb is often a little shorter, and therefore stiffer. On the other hand, on symmetrically tillered flat bows, the lower limb, whichever it is, often takes more set over time than the upper limb (due to bracing techniques, storage and the uneven mechanical effect of nocking the arrow above centre). I have read that the fixes for this include making the lower limb a little longer or a little wider. I am not quite sure what effect you would get, over time, if you left it stiffer. Fractionally stiffer might work, but I can see it would be very easy to get it too stiff and wind up putting the upper limb under more strain, so inducing a set there instead.

I'd be interested to hear what other folk have found about upper/lower limb ballance.

 

[dwardo]

Hi caliban,

In the picture shown what is the brace height ? The string looks like a long string.
When you start tillering you should use a long string only until you can brace the bow at a low brace height, say 4 inches. Then you tiller and increase the brace height to normal brace, say 5-7 inch. The bow when braced to normal brace height will tell you a lot about how the bow is bending before you go further.

If you could post a picture of the bow unstrung, braced, then say drawn to 20" that would give us a little more to go on. So far i cant see any hinges or major problems.

Try to be patient when your at this stage in tillering, if you full draw the bow when you are not sure of the tiller it will only add set to the bow or cause a hinge

I'd be interested to hear what other folk have found about upper/lower limb ballance.

I have recently tried a shorter lower limb with stiff handled bows on a few bows and they all took more set in the lower limb (about 1/2 inc more).

The last elm bow i made and its lighter brother were both symetricaly tillered and took set evenly. In my limited experience it seems you can get away with symetrical tiller on longer bows but on shorter bows it needs to be asym or your stiff handle needs to be too long, meaning less working wood for the load. Atleast this is my thinking recently.

 

[cruben]

Hi
I'm no expert but just an observation , it looks like the tiller is'nt in the middle of the stave , would this have an effect on the uneven bend of the lims making one lim stiffer than the other?

 

[Ogri the trog]

Hi
I'm no expert but just an observation , it looks like the tiller is'nt in the middle of the stave , would this have an effect on the uneven bend of the lims making one lim stiffer than the other?

Yours kind-of right, but,
If the bow bends too much in the handle, it can be uncomfortable to shoot - they used to be known as "Lug" bows and often happened when you tried for a higher draw weight.
Incidentally, the "Fistmele" brace height also coincides with the distance from the tip of one ear to the other - so when you see longbow archers putting their heads in their bows, they are not daydreaming, but checking their brace height.

ATB

Ogri the trog

 

[caliban]

Guys, I've tried to even the tiller and I've twisted a "proper" string (I hope) from 12 strands of heavy weight linen thread which was another first for me. Here's where I'm at. I'm thinking that the job might be a good 'un for a second bow? Thanks for your help so far everyone.

Full draw.

I hope I've gotten away with this, and if I have it's because I lucked out with a nice stave and left it long and wide. Fingers crossed.

 

[dwardo]

Tiller looks good

Might just be me but is the bow upside down ? Tops limb looks shorter than the bottom.

(Edit the bow might be canted slightly lol so probably just me)

What weight did you get?

 

[caliban]

Yeah, it does looks a tad askew, but it is canted a wee bit? Not sure what the weight is, but I've got a 30lb horsebow and it feels a bit stronger than that, I'm hoping it's around 35lb, which is getting close to hunting weight I believe. I've already been eyeing up some likely saplings....did someone say addictive?

 

[C_Claycomb]

I can recommend buying a Bowscale

like this one.
http://www.quicks.com/pdf/pa18 info.pdf

You can do some work using bathroom scales at the bottom of the tillering stick, but that's rather hard to do for full draw. Wouldn't be without mine.