Sight marks

PLEASE HELP TO FUND ARCHERY INTERCHANGE

Big George

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I’ve just changed my arrows and noticed the change to my sight mark was not what I expected.

Old arrows 500 spine, Medallion XR. Limbs are Ukkha SX50. Arrows were tuned at 30m, sight mark was 48 at 60m.

New arrows 400 spine, Easton Advance, same limbs, arrows again tuned at 30m. Sight mark is now 53 at 60m.

Draw length is the same, as is brace height. Draw weigh has gone up to bring the arrows into tune (about 3/4 more turn on the bolts) (Don’t have the new draw weight yet). Tiller differs but the tiller difference remains the same. I’ve used a new string but the same number of strands.

I would have thought with the higher draw weight the arrow trajectory would be flatter so the sight would go up but it’s gone down.
Anyone care to explain the logic in it?
 

Shirt

Well-known member
Draw weight has gone up.
Arrows are stiffer.
Stiffer arrows are heavier.

Say you've increased your draw weight by a pound or so for 3/4 turn. Arrow weight has increased by (7.9gpi/7.6gpi = ) 4%. It's likely to end up being slower.

Also, you've only given one sight mark. The bit you really care about is the gap between your 20m and 60m marks - if this has reduced, the bow has got faster but all your sight marks have dropped slightly which is likely a function of tune.
 

Timid Toad

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Yes, all the above, but also did you change your nocking point?
Arrow mass at the end of the day is a huge issue, which is why field archers are chasing 5gpp (not gpi). This of course over time will have a detrimental affect on your limbs, and failures are common. Don't even start me on Flight archery...
 

Big George

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Thanks for the replies. I weighed the arrows today and the new ones are slightly heavier (I had it in my head, without any evidence, that the new arrows, being thinner would also be lighter, my ahha moment when I put them on the scales).
ok, so heavier arrows will fall faster and need a lower sight mark. Starts to make sense.
Nock point is slightly up, not by much but it will also add to the need to lower the sigh.

I will have shoot some other distances to get the difference between the marks to see the speed increase.

thanks for the replies, it makes sense now.
 

KidCurry

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I’ve used a new string but the same number of strands
Careful, not all strings weigh the same. My 68 inch 8190 string weighs 30grains more than my 652 string. It noticeably affects cast and arrow tune. I now weigh all my strings as well :)
 

iandall

New member
ok, so heavier arrows will fall faster and need a lower sight mark. Starts to make sense.
Actually, heavy arrows fall at the same speed as light arrows. Heavy arrows are slower which means they take longer to travel the same distance so they fall further in the the same distance.
 

Big George

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Actually, heavy arrows fall at the same speed as light arrows. Heavy arrows are slower which means they take longer to travel the same distance so they fall further in the the same distance.
Yes, sorry, “I ‘cannae rewrite the laws of physics captain”.
 

hening

Member
I’ve just changed my arrows and noticed the change to my sight mark was not what I expected.

Old arrows 500 spine, Medallion XR. Limbs are Ukkha SX50. Arrows were tuned at 30m, sight mark was 48 at 60m.

New arrows 400 spine, Easton Advance, same limbs, arrows again tuned at 30m. Sight mark is now 53 at 60m.

Draw length is the same, as is brace height. Draw weigh has gone up to bring the arrows into tune (about 3/4 more turn on the bolts) (Don’t have the new draw weight yet). Tiller differs but the tiller difference remains the same. I’ve used a new string but the same number of strands.

I would have thought with the higher draw weight the arrow trajectory would be flatter so the sight would go up but it’s gone down.
Anyone care to explain the logic in it?
how about the weight of the arrows?
 
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