Which Tiller?

albatross

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Yesterday I was helping another archer set up their new olympic recurve bow. To establish the limb tiller I set it to '0' with limbs the correct way round. We then reversed the limbs and checked the tiller again. It read 'Positive 6mm'. So does that mean that the top limb is stronger than the bottom limb? Should the tiller difference be set on the top limb not the bottom one? Or should they shoot the bow with the tiller corrected to '+ 3 mm' with the limbs reversed? When I did this test on my bow the was '0' when the limbs were reversed.
 

Timid Toad

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Put the limbs in the right way up. Set tiller to 3mm positive. Do the limbs look balanced? Is the string groove showing roughly equal? Yes? Shoot it. Does the bow have a lot of limb vibration? No - leave it and shoot it. Yes - add 1mm to the top and go again.
This upside down thing is if you have a problem you are having difficulty working out.
Cheap limbs are usually made as equal pairs, so it'll be down to limb bolts and bow geometry. If the limbs are tillered the bolts will be roughly equal. If not the top will be wound in a little more.
 

albatross

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Thanks for the reply Timid Toad. He initially had set it to '0' as he had read by 'well known archers' on the Internet that is what Oly bows are set at! He said that his nocking point was jumping up and down wildly after release - which I thought would be limb imbalance. Hence the tiller check. I will give your advice a go tomorrow.
 

Timid Toad

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If the np is really bouncy, check the brace height too. Over braced can increase instability.
 

Stretch

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Tiller is also drawlength dependent. Archers with long draw typically 0-3mm +ve (Koreans say 2mm) the shorter the draw the larger tiller to get the same result - not usually more than 10mm. (If I recall correctly Koreans say max 7mm)

Having said that I shot some of my best scores at 12mm with 32” draw. Following year same score levels at 0mm. Dramatically different stabiliser setup. So the bow tiller actually made little difference if you change other factors around it.

Tiller that will give you relaxed bow hand, relaxed draw hand and a steady aim is the correct tiller for you. Changing grip or changing stabilisers/weights can have as big an impact as winding on the tiller bolt.

With a traditional type limb shape you are highly unlikely to see limbs out of balance within these ranges. (Not sure if that stays the same with more extreme limb design).

Stretch
 

albatross

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Thanks for all your help fellow archers. I just set his bow up with '0'tiller and noted where the serving entered the string groove and marked it with a sharpie. I then pressed the string down and marked where the serving contacted the end of the groove and market it. I measured the two lengths. The bottom limb = 38mm the top limb = 45mm. Does that mean I have to either undo the lower limb bolt OR tighten the upper limb bolt to get <> readings? Of course this assumes the length of the string groove are the same length!
 

Timid Toad

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This is not how you measure tiller!
Use a BH guage and measure from string to limb where it exits the riser, top and bottom. Assuming it is 0 + greater at the top, and you want to increase the difference, tighten the bottom limb, andvice versa.
 

albatross

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Yes I know how to measure tiller. "Put the limbs in the right way up. Set tiller to 3mm positive. Do the limbs look balanced? Is the string groove showing roughly equal? Yes? Shoot it.". But this bow shows a difference in groove length under the string. I have just measured both string gooves and they are the same. Hence the reason for my question.
 

Timid Toad

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Try moving one bolt (when the bow is unstrung) and seeing what happens. I think you need to tighten the bottom one, but as I've never done any more than eyeball the grooves I have no idea what/if you've had any effect by pressing down the string into the limb! You would need to tighten the bottom bolt to increase tiller from 0mm in any case.
 

Stretch

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Firstly, if the limbs are cheap forget about the limb grooves as they are not always reliably cut. However, if the limbs are good quality it sounds like the brace height is way too high. If you can see 40mm of limb groove while the bow is strung then lower the brace height.

The “judge brace height by where it sits in the groove” has variable success. For starters the bowyer needs to have a clue. But if you drop the brace height so the groove is just visible at each limb it is often a good starting point. More than 10mm is probably too much. To adjust you need to increase the turns on the limb bolt for the limb that is showing more groove - twiddle twiddle until they look even. However, this is only a starting point as it doesn’t take into account any of the archer parameters like grip pressure or hook. It also doesn’t account for stabiliser mass. However, for someone who needs their bow set up for them it will probably be good enough.

Stretch
 

albatross

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Looks like I have and interesting few hours ahead of me before the weekend! Thanks for all the advice.
 

albatross

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I made another string today 10mm longer than stipulated for 70" bow with brace of 9". It gave me <>8 1/4" before it stretches overnight on the bow. I still can see about 20mm of string groove before string contact with '0' tiller. This a really low brace height for this length of bow. Recommended brace range 81/2" - 91/4".
 

albatross

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Thanks for the reply. I was trying to get the string to leave the groove 10mm from the end as was suggested as a strating point.
 

Stretch

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What riser? What limbs? What is the recommended brace height for the limbs?

A 70” Hoyt Xi Velos braced at 9” (mid-ish on recommended range) shows less than 10mm.

A 70” Hoyt Avalon Carbon+ brace just over 9” with pretty much string leaving the limb at the end of the groove.

A 72” Border Tempest CV-W braces at about 8 3/4” where the string just leaves the limb at the end of the groove.

How long are the grooves on these limbs cut - from the shoulder of the limb tip? Seems like it must have a very long groove.

Can we see a picture? Maybe you’re not seeing what we think your seeing. You don’t need to press the string to the limb, you just eyeball how much groove you can see (or use a soft tape or a micrometer if you are so inclined)

Stretch
 

albatross

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Yesterday we did a bit of 'fiddling' (technical adjustments). We concentrated on groups rather than bow behaviour. The final result was +4mm tiller and a brace height of 230mm on a 70" bow. So he is happier now. Thanks or all the advice.
 
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