Vane Clearance Problem???

[colockumelk]

I just bought a new bow and I am trying to tune it.  Before I can do this obviously I need to ensure that my fletchings are not contacting my rest.  I have a trophy taker pronghorn drop away and I am having contact issues.  I lowered the rest a bit and the vanes no longer contact the rest but now they are touching the shelf of my bow. 

So my question is what can I do to fix this?  Should I raise my knock point up or what?  I've launched 150 arrows in the last two days and still havn't fixed the problem.     Any help would be much appreciated.   

[Todd_ID]

I'm thinking that you'll need to raise your rest back up and do your fine tuning with the nock height.  Hold your rest up in the cocked position and nock an arrow.  The center of the arrow should be set so that it's at the same height as the center of the hole that goes through the riser that we used to put a cushion plunger in and that your rest may very well be bolted to on the back side.  The bow manufacturers use this height as the basis starting point for designing a bow and try hard to make a level nock travel happen at this height.  Once the rest height is set, then use a bow square or a carpenter's square on the string to find the point on the string that is the same height as the bottom of your arrow now that you have the rest height set (arrow is 90 degrees to the string).  I put the nock point below the arrow because, when you use a D-Loop and a nock point inside that loop, having the nock point below the arrow will cause just enough pressure downward on the arrow as you draw to keep the arrow from coming off the rest due to the extra angle that you get by not having the arrow be exactly centered in the D-Loop.

If you've got a release loop tied on already, then you can simply wind it around the string, and it will raise or lower like a nut on a screw.  If not, then tie the release loop on above and below the arrow position that you found.  This gives you a good starting point for arrow and rest location. 

You'll want to check the rest timing before you shoot it.  Draw the bow slowly, and check to see when the rest reaches its full upright position.  The length of the activating cord on the rest determines when it raises.  Adjust this length as needed to get the rest coming to full height when you are roughly 1-2" from reaching full draw; a shorter cord raises it sooner and a longer one delays it.

[Todd_ID]

glitch in text box, so I'll continue on in separate posts

You're ready to test for vane clearance again.  Either use the spray foot powder and see where it's hitting, or put lipstick on the vane tips to see where it transfers to the rest.  Make sure to look at strings, sight, riser, and rest.  My guess is you should be good now.  If I remember correctly, that rest is prone to bouncing off the riser and contacting the vane on the rebound; a piece of moleskin under where it falls may help that, and it'll make the falling of the rest quieter, too.

You're ready now to paper shoot to rough-in the nock point elevation and rest windage.  Vanes high = nock point down, vanes left = rest left, and vice versa for both.

To fine tune rest windage and get sight windage set I use a modified French Tuning method that seems to work well.  Hang a weighted string in front of the target.  At 3 yards from target, shoot at the string; elevation doesn't matter in the tuning step, only windage.  Move the sight only until you can hit the string.  Step back to 10 yards and shoot again.  Move the rest only until you hit the string.  Step up to 3 yards and shoot again.  Move the sight only until you hit the string.  A couple repetitions of this will get sight and rest windage in the same plane and close to perfect.  Remember, only move the sight at 3 yards and only move the rest at 10 yards.  You're finished with this step once you hit the string at both distances without moving anything.

[Todd_ID]

From this point you can set the individual pin heights at whatever distances you want them to be sighted in for.  Just shoot groups of field points at those distances and move the pins up or down accordingly.

Assuming that hunting is the goal, then you can continue on with broadhead tuning.  The idea is to get your broadheads and field points hitting in the exact same group.  If they do hit in the same place, then the bow is very well tuned; all you can do from there is tiny tuning steps to try and reduce group size.

To broadhead tune a bow, simply shoot 3 broadheads and 3 field points from 30 yards to see where the center of each group is.  Let's say the field points hit 6" to the right and 2" high in relation to the broadheads.  Work out the left and right problem first, and then work on the elevation.  You move the rest a small amount in the direction that you want the broadheads to move; in this case, move the rest 1/32 or 1/16 inch right.  Reshoot both groups.  Both new groups will be right of center, but the broadheads will be closer to the field points than before.  Keep moving the rest in small amounts until the groups both are in the same vertical line, and then move the frame of the sight right to get those groups back into the center of the target.

Now you're ready to work on getting the elevation of the groups to come together.  In our example, the broadheads are hitting 2" below the field points.  You can either move the rest up a tiny bit or move the nock point down.  The best bet is to move the nock point since we set the rest height where the manufacturer designed the bow to shoot best.

[Todd_ID]

You moved your nock point down, so your groups will be above the point on the target that you're aiming at.  The broadhead groups will move further than the field points with each move you make, and eventually the broadheads will catch up to the field points.  You will eventually get to a point where the center of both groups is at the same elevation and windage.  That's basically the definition of perfectly tuned; you put big wings on the front of an arrow, and it still shoots to the same place as when it doesn't have them.

All that's left is to move your sight frame up to compensate for the tuning moves you made to bring your groups back down to the center and double check that your pins are all set at the right height according to the distances you want.

Lots of practice later, and you'll be ready to hunt!  Print this out and take it out to where you shoot and work on your bow.  Don't expect to be able to do all this in one day, though, because you'll get tired and start shooting poor groups.  Try to space it out over a couple or three days, and the frustration level will go way down.  Get back on here and post up some thoughts on the process and what worked and didn't for you, and post any questions you may have along the way.

[colockumelk]

Thankyou so much for the advice Todd.  I'm afraid I'm going to need more.

Okay so I reset my rest so that it was even with that bolt hole like you said.  Then I moved my nock point so it was a touch low like you said.  But I'm still getting fletching contact with my rest.  So what do you suggest that I do now?  Again thankyou for the help that you've been giving me. 

I look forward to doing the rest of the things that you've listed I just can't seem to get past step 1.   

[Todd_ID]

Generally nock height should be dead level or maybe 1/16 higher than rest height.  I don't think I've seen any that are lower.  The lower part came from the fine tuning example in broadhead tuning, and that would be only because it wasn't perfectly level at the start.

You've got one of 3 problems: rest timing, bounce back, or bad spring.

Timing: You want to double check that the rest is coming to its full up position just before full draw.  The length of the activation cord sets when the rest comes up and, therefore, when it drops away as you release the string.  You may be trying to use the activation cord in conjunction with the cable slide.  This works occasionally, but it moves at unpredictable times and at a slow rate in comparison to the string travel.  You're far better off to use the downward-travelling cable to attach the rest cord to activate the rest.  Make sure the cord is attached at about the level of the bottom of the grip to get the most predictable travel.  Here's how Paul at Starrflight deals with these rests: http://fob-nation.com/SMF/index.php?topic=124.0 .  FOB's and Blazers are about the same for clearance tuning.

Bounce-Back:  Some rests, and I think yours in particular, are prone to bouncing off the shelf of the bow and up into the vanes before the arrow clears the bow.  Try putting a cushion of moleskin under the rest to help this.  Also, see to it that the prongs are laying flat on the moleskin when it's down to prevent the prongs from becoming a spring.

Spring: You can also, possibly, get a lighter spring in the rest from Trophy Taker to help this.

[Todd_ID]

One, possibly simpler, fix is to turn your vanes in a different orientation.  Maybe try putting the cock vane up and try that.

Sometimes it takes an engineer to type 3 pages of instructions to fix it in one sentence.  (Yeah, I'm an engineer.)

[colockumelk]

Thanks Todd for the help.  I must have misunderstood you when you were talking about nock height.  Right now my nock is about 1/16 inch below my rest.  So I'll fix that pronto.  That might just solve the problem right there.  However following your advice so far has worked out great.  I took it to the shop today and had it paper tuned and didn't have to do anything.  It paper tuned perfectly.  So thank you again for that.  I also refletched a couple of my blazers so that they are the normal vanes and those don't seem to contact at all.  So maybe that worked as well.

One question though.  You mentioned trying the cock vane up.  That's how I've been shooting my arrows.  Is the cock vane normally pointing downward?  Basically have I been shooting my arrows incorrectly the entire time.  If so I appologize for the dumb questions. 

[Todd_ID]

No problem... Cock vane can go anywhere you want it with a drop away rest....as long as you're getting clearance on cables, sight, riser, etc., it doesn't matter.  Normal is up for many guys.  I shoot with it out to get clearance on my cables if I'm using the tall Blazers.

Keep plodding along and keep us posted with the progress reports.

[colockumelk]

Hey Todd thanks for the advice.  As per you and Hoytstaff83's suggestions I just adjusted the timing on my rest and it worked.  I am so stoked.  Thank you so much.  Tomorrow I'm going to paper tune it again and then I'm sure if it's not windy (I live in Ellensburg so that's a big if) I'll walk back tune it.  Thankyou so much.  If you ever pass through Ellensburg the drinks are on me.  Thanks again.  I'll let you know how the paper tuning etc goes.