Sight marks low away from home?

Mistake

New member
Ironman
Shooting at Pentref the weekend before last, I noticed that all my sight marks were low when shooting away from my home club. I've noticed this at other shoots but I was shooting so.. questionably.. that it could have been down to a laundry list of other issues.

Our home field does have a slight elevation (something like 6 foot over 90m), but I wrote down the sightmarks that I shot each target from at Pentref to compared when I got home and I found that I was 2-3 meters "high" at home consistently across all distances from 10m to 60m inclusive.

Obviously I can compensate for this but setting my sight to hit high when i'm getting marks for a shoot, but it's a little annoying.

I've been working on my execution as it's been very ropey until the last few weeks but still found I was being a little hesitant at the Pentref shoot. Could that be part of my issue or is it mostly just the field slope?
 

Valkamai

Member
I would have thought the slopes at pentref would have been more than at your club field (even with what was quite a fairly level pentref course layout last week).

Sent from my HTC Desire 626 using Tapatalk
 

Aleatorian

Member
Similar thing, I tend to have the same issue, but in reverse. My home field is fairly flat but one of the fields I guest shoot at has a slight elevation, and my sightmarks are higher there than my field.
5 clicks up at 90m which equates to about 0.5m for me there.

Sightmarks will always vary with Slope, so gaining them on the flat is a good start point, but you do have to account for slope. I've seen various programs that can deliver sight tapes and cut charts, as well as excel spreadsheets that do the calculations
 

KidCurry

Well-known member
Our home field does have a slight elevation (something like 6 foot over 90m), but I wrote down the sightmarks that I shot each target from at Pentref to compared when I got home and I found that I was 2-3 meters "high" at home consistently across all distances from 10m to 60m inclusive.
Slope is a factor, but if it's happening at all outside shoots then I would say you are probably tightening up or trying too hard.
 

geoffretired

Supporter
Supporter
When I was reading a thread on the barebow section there was a post regarding how much to aim "off" for shooting uphill or downhill.
One poster was saying that the allowance is based on the horizontal distance to the target, whether it's above or below the level of the shooting peg.
So if you shot uphill at 60 deg the horizontal distance to the target would be half of the distance you would measure out with a tape.
At 45 deg it would be 7/10 or 70% of the actual distance.
6 feet in 90m is equal to an angle of about 1.1 deg and the horizontal distance would be 99,99% of the actual measured one using a tape or wheel.
The theory behind the explanation was that arrows drop under the effect of gravity. Gravity works vertically downwards and ........ I could not follow the rest of the explanation. BUT the upshot of it was that the horizontal distance would be shorter than the actual one and therefore the arrows would fly higher, unless the aiming point was lowered, compared to level shooting.
I would like to understand why??
 

Timid Toad

Moderator
Staff member
Supporter
Fonz Awardee
Ironman
Just to check: How are your distances measured out at your club? We've just disposed of an old marked rope as it was getting erratic. Worth a quick check to if it won't offend anybody.
But as it was consistently high from 10m by about the same amount my guess is you are altering your grip or head position when out of your comfort zone.
 

Mark31121

Member
Ironman
I agree that checking your field is a good idea.

I found out last week that someone measured out 80 metres instead of yards - I had a lovely group on the grass at a competition...
 

Mistake

New member
Ironman
We have a proper 100m measuring tape and we have to remark every time we shoot as we use the local football clubs field during their off season.

Although, come to think about it, this tape has been in the club about 10 years, so it could have changed, although to be out so consistently along the distances :/

Maybe it's a form thing that I need to look at
 

Timid Toad

Moderator
Staff member
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Ironman
I don't suppose you printed yourself off a sight tape, then stuck it on in the wrong place?
 

Mistake

New member
Ironman
No, these are marks I got the old fashioned/ hard way.

- - - Updated - - -

No, these are marks I got the old fashioned/ hard way.
 

Corax67

Well-known member
Might the wind have been a factor?

Our field has a pretty much permanent left to right wind on it (to varying degrees) and when I shoot away I have to remember to dial out the compensation I have written into my sight marks book. Maybe a head or tail wind was blowing at Pertref and that influenced your sight marks ??




Karl
 

tzadmin

Supporter
Supporter
When I was reading a thread on the barebow section there was a post regarding how much to aim "off" for shooting uphill or downhill. One poster was saying that the allowance is based on the horizontal distance to the target, whether it's above or below the level of the shooting peg.
I would like to understand why??
It's a bit more complicated than that.
The hand-waving explanation is that gravity only pulls vertically down. It has the largest effect on deviation from 'straight' when 'straight' is horizontal. When 'straight' is vertical (a bit extreme) gravity doesn't pull the arrow off line at all - just speeds it up or slows it down - so you shoot vertically with sights set for zero distance (and a very hard hat). Everything else is somewhere in between.
Exactly _where_ in between is perhaps best answered with a lot of experimentation and practice for a particular archer, as the physics is not the only thing affecting aiming. There's the fact that the archer's posture and alignment change with shooting angle, and that is quite likely to be a fairly big effect for many of us.
But archer issues aside, it _is_ physics, so you can do the maths. If you do (at least ignoring air resistance), all sorts of interesting things happen. The sight adjustment is not exactly the same for uphill and downhill gradients, for example - partly because at any real distance, you're already pointing a bit uphill to hit the target, and partly because a downhill arrow gets a bit of help from gravity. And there's a small region in which the sight needs to be moved _down_ a tad as the slope changes. However, while all that introduces some finer points, it turns out that the sight adjustment needed is not a million miles off being proportional to the horizontal distance. It's not exact, but it's within half a centimetre even for 70m at fairly extreme slopes (that was calculated for a 200ft/sec arrow speed, with gradients up to +-1:1). So your OP was not far off as a working approximation.
 

geoffretired

Supporter
Supporter
Hi Tzadmin, Thanks for that explanation. The effect of gravity pulling down being greater when shooting horizontally, was the bit I was forgetting. I can believe it is more complicated, but it seemed that shooting uphill would not mean arrows landing so low as the OP experienced.We are abigger source of variation, I feel.
Cheers Geoff
 

geoffretired

Supporter
Supporter
Hi AndyW that was the article I read and didn't understand fully; but thanks for your efforts on that.
I think I get it now, gravity pulls the arrows down with more effect when the arrows are trying to go level.
If the arrows were shot straight up into the air, gravity would still pull it straight back down but would not pull it off line from a target like a popinjay.
 

AndyW

Well-known member
Hi geoffretired, I don't see what you exactly mean by pulls down with more effect when trying to go level. In my mind it's just a function of time and gravity (+ drag). If you hold a bullet in your hand and drop it, it will take x hundredths of a second to hit the floor. Drag aside the same bullet shot at 400 mph will hit the floor in the same time it will have just gone further. If you shoot uphill you are taking a tadge of speed away cf downhill even though both are probably over terminal velocity so it will get there slightly slower and hence drop a little more. What he doesn't say is that the drag will slightly increase the up angle of the uphill shot and down angle the downhill so to an extent will counter the above making the "shoot the horizontal" even more appealing for both. I guess this is why the best flight arrow angle is less than 45 as the drag pushes it from 42 - 43 up to the 45. That's how I think of it anyhow.
 

geoffretired

Supporter
Supporter
Hi AndyW I wondered if I had explained that correctly. Heehee. I will try again.
I think it's to do with pulling the arrow off its intended course. If the arrow is shot vertically down over a cliff, it could be 1000 feet high but gravity would not pull the arrow off course. It would speed up under its influence but not deviate.
Similarly for vertically upwards, gravity again would pull and slow down the arrow, but would not pull it off course so long as it could reach as far as the target. That is an extreme case; close to vertical shots up or down would be affected by gravity but not pulled very much off the initial line of the shot. With near vertical shots, the horizontal distance travelled is short,and gravity in those cases, acts to slow down or speed up mainly and only a small component is pulling the arrow away from the intended course.
If we watched an arrow shot close to vertically upwards( arrow close to vertical at launch) it would go close to the "expected" mark, but follow a curved path, as gravity pulled it slightly off line, and it would miss. The curve would be very small and the miss would be close to a hit.
When we shoot close to horizontal, gravity pulls with a greater effect,( pulling the flight off the straight line more) as seen by the clear curve in the arrow flight when viewed from the side. We have to aim the arrow up and over the line of sight so that curve can bring the arrow down to the gold not down to the ground.
Shooting almost vertically, that curve is not so obvious. BUT we may imagine it is greater because at the top of the flight path, the direction changes sharply as ascent turns to descent. We note the very obvious bend in the flight at that point but miss the almost straight path of the lead up to that.
 
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