Setting height of spring blade rest on compound

chuffalump

Well-known member
Question. I understand that the start point is to have your arrow running level with the rest mounting holes (button holes on a recurve) and your nocking point level or 1/8 higher.

BUT the arrow compresses the spring blade. It strikes me that an arrow on the string at brace height has a lot of weight overhanging in front of the rest. It this acts like a lever then the rest will have more down force on it at brace height than at full draw. So, if I set my nocking points and then jack the arrow up level with the holes and then draw the bow, the tip of the arrow is lifted as the bow is drawn and force comes off the rest.

Am I correct? I'm not in a place where I can test this till this afternoon.

If I'm correct then should the rest height be determined at full draw instead? Get someone to look at the arrow hole alignment while aiming and adjust as per their observations? Or alternately, take the flex out of the rest when setting by supporting the arrows weight?
 


geoffretired

Supporter
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If you had a very soft blade, the difference between the two levels would be quite large. As it is, I expect the drop at BH is about 1mm. You could remove the pile to get a closer match between the two. I just hold the shaft at the nock end between finger and thumb and place the front end of the shaft into the blade V; so the arrow is at a very similar position to the full draw one. That lets me see whether the shaft is level with the mounting hole, when at full draw.
I put my bracing gauge onto the string and slide it slowly down until the straight edge of the gauge just rests into the bottom of the v in the blade, with no depressing. I put marks for the d loop at square for the lower and 6mm above that for the upper. Once the d-loop is fitted to those marks there is a 6mm gap inside. I serve round the inside of the lower loop knot to leave the correct size gap for my nocks. That's about 3mm. That leaves the arrow nock about 3mm above square. To the naked eye it is just visibly not square. The bow will shoot well enough like that for starters.
 


chuffalump

Well-known member
I used a bowsquare aligned to the bottom of the button hole, put a nock on the string and moved it 1/8 up. Tied a lower nocking point. Then I tied a top nocking point sized to my nocks (plus a little slack). D-loop around the outside of both. Looking at my procedure again, I realise that the running height of my arrow should be slightly lower than level with the holes due to the nock being narrower than the arrow shaft (to keep the 1/8 up relationship intact). Also, I can see that I've assumed my arrow shaft diameter is the same as the mounting hole. It's not far off but it is still a dangerous assumption.

Since it seems I'm essentially correct, I'll rest the arrow tip on the blade and then set running height a little lower than hole centre for today. Looks like I'll have to move the nocking points and loop up by a mm or two when I get a chance. By accident I've probably set the arrow dead square.

Thanks Geoff. That's my morning sorted. I wonder if this is contributing to my lower sight marks.
 


KidCurry

Well-known member
It's all a bit accademic if the arrow is absolutely level with the hole or a smidge out as you will no doubt be paper tuning to sort out any nock high/low issues anyway. If I have a 1/4" or 1/3" nock high or low through paper I will use the blade rest adjustment to correct it rather than the courser d loop adjustment.
 


geoffretired

Supporter
Supporter
I have no evidence to say that having the arrow rest 1mm lower than level with the button hole ( and nocking points to match) has any serious implications for accuracy. I'm not sure that all bows have the same distances between grip throat and button holes; perhaps that's a sign that there is some flexibility in the setting up. Hoyt had a vertically adjustable button hole at one time!
My thinking is that they are good starting points and if we want to take matters further we can do bareshaft tests to see if we can get better results.
I'm not sure what caused your lower sight marks. I wasn't too clear on one part of your post regarding that. One thing I may have got wrong is what you said about the connection between peep and sight movements.
A move of the peep of 1/2inch would only raise or lower your draw hand by about half of that, due to the string being on a slope at full draw. A movement of the sight of about 1/4 inch should bring the arrow back to the same elevation, relative to horizontal.
 


chuffalump

Well-known member
@KidCurry, yes. I usually (in my short time with a compound) adjust the rest as opposed to the nocking height. Much easier. I have a home made paper tuning frame but it's hard to paper tune at the club because it interferes with everyone else. I'm thinking of using the garage and a bag target. For now I was just going to lower the running height and shoot lower than the button holes by a fraction.

@Geoff, I figured that a lower peep height would lift the nock end of the arrow at anchor, the arrow therefore points lower. Meaning lower sight marks to lift the impact point back up. In my case it was a change of 2.x to 4.x though. This is all assuming that the sight mounting holes in the riser are in the same relative positions. Need to get the rest sorted out first, in case it's flicking the back end of the arrow due to being too high.
 


geoffretired

Supporter
Supporter
AHHh I thought you were talking about moving the peep and sight of one bow only.
Yes, I don't like to see the fletchings getting marked by the rest. When the rest is pressed down, it will spring back up and reach a point that is higher than the start position. Some rests have a stiff short blade fitted on top of the v blade;it limits the upwards movement of the v blade so it can't spring higher than the "at rest" position. In some cases all you need is a slight change in rest position.
 


chuffalump

Well-known member
Update - Rested the arrow on the blade in shooting position as opposed to at brace position. There was just over a third of the hole visible so I dropped the rest by two or three mm to compensate. Don't have any spring limiters on my rest and I haven't notice any fetching damage but I haven't really looked yet. All this thread was due to a sudden click in my brain while in bed this morning. A 'hang on a minute' spanner in the gears.

😁 I'm talking about the new bow vs the old. New bow is set maybe 4# higher. Peep position less than 1/2 inch lower. Sight mark for 20yd twice what it was. If the weather holds I'll get firmer data today with my rest adjusted. Also, yesterday's shoot was a bit disorganised due to ground works and tidying activities. Maybe it wasn't an accurate 20yds. Mind you, a couple of yards either way wouldn't make that much difference either.
 


geoffretired

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Supporter
Sight mark for 20yd twice what it was.
Hi Chuffalump. That's the part I can't follow. If it was on 20 its now on 40??
If it was on 5 its now on 10?? I can't visualise how much lower the actual sight aperture is.
 


chuffalump

Well-known member
Ahhh. Actual sight marks, not distances. There's around 10mm difference between 1.x and 2.x etc on the sight tape. My old compound shot at 2.x for 20yd, 3.x for 30rd and so on. Yesterday I was shooting with an old 40yd sight mark (approximately) on a 20yd target. Sight mark about 20mm below what I expected. Especially given that this is a better bow with a slightly higher poundage.
 


geoffretired

Supporter
Supporter
I see what you mean now, cheers for that.
Please, don't think that I am trying to teach granny to suck eggs; this is just for clarification.
Sight marks are really only valid if comparing one bow with another when the distance from the sight aperture, vertically down to arrow shaft are compared.
As you said, the mounting holes may be higher compared to button holes. You can easily compare those measurements, just to see if that's the reason. It would take away some of the "doubts".
 


chuffalump

Well-known member
Yeah. Hard to measure as my tape measure has gone walkabout but a rough check with a bow square says the new bow sight mounting holes might be around 10mm or so higher which would explain half of the difference. If the rest adjustment helps I might be back on track. I think I might run out of sight rail before the long ranges though. It's already been dropped down in relation to the extension bar. I am using an old set of xx75s though. My old ACCs might help.
 


chuffalump

Well-known member
Well, altering the rest didn't make the slightest difference. 30yds at 5mm up from my previous bows 50yd sightmark. Paper tuning and resignation are the next steps. 😂
 


KidCurry

Well-known member
Well, altering the rest didn't make the slightest difference.
To what?

30yds at 5mm up from my previous bows 50yd sightmark.
How are you measuring this? If it is just the sight scale it doesn't mean anything. You must measure the distance from sight pin to arrow. If you run out of sight scale the sight scale probably needs dropping one set of holes, but i think you said you have done this. Just to check, I assume you are not comparing XX75s to your old ACCs as XX75 would be almost 1/3rd heavier.

It's also worth remembering that a nock 1/8" higher will drop the arrow impact at 50m by almost 6 inches. I usually set my nock point horizontal before paper tune.

It is also worth checking the peep to nock distance. If this is slightly less than you had before, because the string angle is different say, this will greatly affect your sight marks.
 


chuffalump

Well-known member
I had a forlorn hope that the rest was interfering enough that the sight marks would improve.

I know that 10mm of the sight mark difference is due to difference in the position of the mounting holes. Still leaves the puzzle of where the rest of the difference comes from.

The sight bar is already as low as it can go.

Time to think. 🤔
 


geoffretired

Supporter
Supporter
Chuffalump, can we just go through a summary of the two bows etc, in order to eliminate a possible oversight?
I have looked at the two bows on line and they seem very similar in specs. Mybo is faster.
Are draw weights set equally on both?
Draw lengths? That's length of power stroke in this case. One way to check is to put the arrow on the string and mark where it contacts the rest.( one arrow for each bow) Then mark with lipstick near the pile end of each arrow an inch or so that can be disturbed by the arrow rest when at full draw. That will leave a mark that shows full draw to arrow rest. Distance between two marks is power stoke length.
Check the tiller geometry of each bow. Best done with an arrow or other length of rigid material. Measure from top axle to bottom limb shoe.( choose a place that is easily found on the other shoe,too.) The two readings on the same bow should be equal to each other. The other bow may have different readings from the first bow, but its two readings should equal each other.)
Does each bow draw to a single solid stop at full draw? IF a bow is out of time, there can be two small stop positions at the end of the draw instead on a single one. It could be that one is out of time and you may be drawing it to its first stop, because it feels solid, but there is more to go to reach the next stop.
 


chuffalump

Well-known member
Good thoughts but difficult to do as far as powerstroke in concerned. I've transferred rest and sight from old to new. I imagine long term compounders probably have old rests knocking around etc and could get all their bows operational at once. 😁

The new bow feels good although the valley is a lot more defined, meaning it's easy to bump the arrow off the rest as the weight comes off. I've also being reducing the DL this afternoon as it felt like my arm was almost completely folded up. So maybe some ergonomic differences somewhere? Both bows have a solid back wall, the Static has stops built in to the dl modules while the Origin has separate adjustable blocks.

The old bow was specced at 50# wound fully in. At my dl it should have been about 48# but my luggage scale never went above 46#. The new bow seems to peak at 48# limbs fully wound out. So slightly higher poundage, which is what I expected. Not that it's easy to measure with a standard luggage scale.

I suspect that the issue is going to come down to a combination of dimensional differences, peep position, set up(?) and mystery factor X. The Origin brace height is slightly higher and about 6mm greater from string to button hole. Tillers are even. I think the timing was ok on the Static but the Origin has them fancy schmancy binary(tm) thingys I think. Both cams are linked to the each other, no yokes. Starting position is equal but I'll need an observer for the finishing position.

It's not that's it's a massive problem. Just a brain teasing puzzler. I'll try and paper tune during next week, if something is way off then the arrows might be losing a lot of energy while straightening out.
 


chuffalump

Well-known member
Thanks for all your suggestions and comments so far guys. I hope I can continue to pique your interest. 😎
 


geoffretired

Supporter
Supporter
I know the feeling of teasing puzzlers. I don't spend a lot of time these on setting up my bow, but I remember from a few years ago spending too much time trying to get all the settings to match expectations or " the norm".
It is a little worrying, for example, when the arrow rest has to be set further in or out than would seem to be correct. Or the sight needs to be further in /out compared to the arrows or the string line.
It always seemed to me that things should shoot properly when they are set up according to what I was told. When my set up has to differ from that I have to wonder what is wrong to cause the differences.
These days I accept that there can be small differences between my set up and what is considered to be ideal or correct. The small differences in set up don't spoil my groups- I do that by myself.
The sight mark differences you have seen are a bit of a puzzle. The over long draw length can cause collapsing on the shot and creeping from full draw during the aim. Perhaps that is part of the answer.
 


chuffalump

Well-known member
Question (another one) - how do you know when to move to a stiffer blade on the arrow rest?

Woke up early today, plenty of time before work, so I set up my bag target and home made paper tuning jig in the garage. First two arrows gave different results so picked another two and ended up having to move the rest up a fraction and to the right by quite a long way (tail high and left). Shot a few bullet holes but still getting random tail high results and wondered if the rest was too springy making it too sensitive to slight release differences. Problem might also be due to the tips of the rest catching the vanes. They are wider than the gap between the hen vanes so some contact might be happening, depending on where the arrow is at this point.

The paper tuning jig is a thick cardboard box with the bottom cut out of it. Hang it from the roof and keep it vertical with an old CD stand. Not exactly precise, so any movement would cause small changes in the arrow holes.

Those red resin blades seem to be available in multiple types and sizes but I thought I'd ask the experienced compounders first.
 


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