String alignment on a compound bow

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seanplod

Member
So I have just got my old PSE Supra bow out to set it up. Having just set up my new bow I have brought a new eye to bare on this and to how my old bow was set up. On setting the approximate starting point for my rest I have to question myself.
my usual method was to stand behind the bow line the string up through the centre of the hole’s that run down the back of the riser. Having studied this alignment I believe I have got it wrong. Looking at the top and bottom cams they are actually sitting to left of the centre between the limbs which therefore means that the string actually runs to the left of those holes.
My question is therefore is this actually correct or should I set my rest with the string running through the centre of the holes ?
Thanks
 
KidCurry

KidCurry

Well-known member
AIUK Saviour
I don't recall the string running down the centre of the bow. My old Supra ME had a line machined down the centre of the shelf as I recall. It was a pain. The only reliable way to set centre shot was a modified French Tune.
 
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inthemiddle

Active member
seanplod said:
Yes
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The method that has worked for me is screw on a long rod, adjust said launcher so the arrow runs parallel with the long rod. This is a crude starting point. Then do the above, French tune the bow and or paper tune it till it shoots a bullet hole.
 
jerryRTD

jerryRTD

Well-known member
Fix an arrow to a flat portion of the riser with an elastic band, nock one of your arrows and let it rest on the arrow rest. adjust the arrow rest until the two shafts are parallel Lock the rest down and shoot through paper
 
Sinbad

Sinbad

Member
My supra has a line down the shelf. But I do use a laser alignment tool, once done tune it. I found that the line was a smidge right of the string. String wasn't middle of the holes either.
 
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inthemiddle

Active member
Sinbad said:
My supra has a line down the shelf. But I do use a laser alignment tool, once done tune it. I found that the line was a smidge right of the string. String wasn't middle of the holes either.
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The laser tool does not work on My PSE perform X. The string may line up but the cams don't
 
Shirt

Shirt

Well-known member
inthemiddle said:
The laser tool does not work on My PSE perform X. The string may line up but the cams don't
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That's why they give you those limb adjustment screws so you can really mess around with stuff that you don't necessarily understand :D

More seriously, any centreshot point is only a starting point for tuning. Generally accepted approach is to measure out from the side of the riser 13/16" and set the centre of the launcher there, then go tune.
 
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inthemiddle

Active member
Shirt said:
That's why they give you those limb adjustment screws so you can really mess around with stuff that you don't necessarily understand :D
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Yeah I messed with them and now have perfect bullet holes :) Not shot it at any distance yet though. Roll on summer :)

Is the 13/16" a starting point for any compound bow?
 
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Shirt

Shirt

Well-known member
13/16" is a good start point for Hoyt, PSE, Mathews, Bowtech. I don't know about other brands, some of the smaller / weirder ones like Gearhead probably have a different measure because of the way they're built.
 
B

bownarra

New member
Do not use your rest to adjust centershot from actual center. Set centershot at center then leave it! Your bow is meant to work with the arrow in the exact same plane as your string. If you need to do something else to paper tune then your arrows or cam lean are off.
 
jerryRTD

jerryRTD

Well-known member
bownarra said:
Do not use your rest to adjust centershot from actual center. Set centershot at center then leave it! Your bow is meant to work with the arrow in the exact same plane as your string. If you need to do something else to paper tune then your arrows or cam lean are off.
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The problem with that is the assumption that it is always the bow or the arrows that are at fault. The archer could have set the centre shot wrong or the archer could be torqueing the bow.
 
B

brassgbits

Member
Just some info I found tuning my Mathews TRX when I set it at 13/16 = 20,6mm
my centre shot ended up at 19mm with VAP 350 arrows and 19,6mm for VAP 400 both do bullet holes and French tune out to 50 metres.
then I changed my release from a Carter to a Stan this changed the centre shot to 19,4 and 20mm
0,4 does not sound much but it’s 36mm at 90 yards.
 
jerryRTD

jerryRTD

Well-known member
brassgbits said:
Just some info I found tuning my Mathews TRX when I set it at 13/16 = 20,6mm
my centre shot ended up at 19mm with VAP 350 arrows and 19,6mm for VAP 400 both do bullet holes and French tune out to 50 metres.
then I changed my release from a Carter to a Stan this changed the centre shot to 19,4 and 20mm
0,4 does not sound much but it’s 36mm at 90 yards.
Click to expand...
The same sort of thing happened to when I changed my Carter Lockjaw for a Carter Quickie.
 
pipeski

pipeski

Member
I recently used a technique where I taped a piece of string from one limb bolt to the other, a few inches in front of the rest. Then I used an old cut-off nock end of an arrow that will sit on the rest and just fit between the bow string and the other bit of string. This makes it really easy to eyeball whether a nocked arrow is centred horizontally relative to the limbs. Seems to have worked pretty well.
 
Thorvald

Thorvald

Active member
This is an excellent tool to set up a bow: OMP laser tool til opsætning af compoundbuer As other says you should set the vertical and horizontal centershot as good as possible - and this tool is excellent at that. And then that is a very good place to start. Then one can fine tune with for example paper test, if and when one wants. I don't know what the French tune is.
 
Howi

Howi

Member
Easiest way to set centre shot (align arrow with cam/string) is to clamp a parallel arrow to the top and bottom cam, with the arrows pointing forwards. Put an arrow on the rest and with your bow on a stand(on bottom limb), look down from the top of the bow and use the arrow rest adjustments to get all three in alignment. This should get you pretty close to the correct alignment.
This should set your static alignment, you will need to french tune to get the dynamic alignment. On a day with little or no wind you should not have to adjust windage at 20 yds or 100 yds.
Remember adjust sight at short range, adjust arrow rest at long distance, as you repeat the process, the adjustment will coincide at the point of alignment, i.e you should not need to adjust arrow rest OR windage at long or short distance (in theory!)
ALL the other alignment processes rely on the cams being aligned to the plane you are measuring from, which may or may not be true.
Contrary to what people say, laser tools do NOT work unless you are very lucky and you WILL still need to french tune.
13/16 is JUST a starting point and does NOT work for all bows.
Aligning the string with the centre of the riser does NOT work unless you are very lucky.
Aligning your arrow to your long rod is another no no.
The above procedure is for HORIZONTAL alignment, for VERTICAL alignment you should set your arrow at 90 degrees to your string (or slightly less, never more!) and the centre of the arrow should run through the centre of the BERGER button hole(s).
It is the horizontal alignment that is the important one
 
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