Re: Herlaai Tips
Posted: Wed Nov 16, 2011 10:07 am
Hier is so ietsie wat ek op die luggeweer forum geskryf het oor die onderwerp so paar jaar terug.
Die meters wat ek gebruik is die Kestrel 4500 en ek het n Silva Pro ook gehad wat baie goedkoper is en net so oulik werk. Jy moet maar net dophou wat met jou POI gebeur en notas maak daarvan en ook al die ander data afskryf elke keer as jy gaan skiet. Daar sal vinnig n patroon ontwikkel. Ek skryf die datum, tyd,
Temp , Humiditeit, barometriese druk en dan veral die Density Altitude neer.
I finally cracked it!......... POI shift.
--------------------------------------------------------------------------------
After all my data collection over a year and a half, I finally have an answer for all our questions.
I have had a look at all the variables that I encoutered, over this long period, but could not come to a definate conclusion. But looking at what happened over the weekend of the Nationals, and taking notes as we went, I could not help to be even more confused as I was before.
The first day saw the most confusion, with everybody having different problems. Some shot low, others high, and some spot on, on their settings. The chronograph, however had most shooting to high.
It bothered me, because some of the people were recording completely opposite results, as what I expierience up to now. I went back to my previous thread of more than a year ago, "PCP, a strange world", and made a startling discovery. My recent findings, was 100% opposite, to what I found a year ago. This put me in a complete backpeddle mode, and after reading the link that Fox gave me back then, ://www.usatoday.com/weather/wdensity.htm
everything fell in place.
It says: HUMID AIR IS LIGHTER, OR LESS DENCE THAN DRY AIR AT THE SAME TEMP
1. Higher temp causes a decrease in Air Densityhttp2. Barometric press has an opposite effect on AD. Increasing press, increases AD
3. Altitude has a far greater influence on AD, than higher or lower press due to weather systems (it has a 1mb change, for every 8m) This is where the big discrepancys lie.
4. Air Density is lowest at high elevation, on hot day, when atmospheric press is low.
5. Air Density is highest at low elevation when the press is high, and the temp is low
6. Compared to the differences made by temp and barrometric press, humidity has a smaller effect on the AD, but humid air is lighter than dry air at the same temp
It goes further, and say that pilots use "density altitude" to relate air density to aircraft performance.
This is what affects Air Density :
High Air Density is caused by:
cold temp
High Barrometric pressure
Low Altitude
Low Humidity
Low Air Density is caused by:
Hot Temp
Low Barrometric pressure
High Altitude
High Humidity
High Altitude = Low AD, but cold day = high AD (like we had early morning, and late afternoon at Nationals)
High Altitude = Low AD, but hot day = low AD( like we had towards the middle of the day at Nationals).
Low altitude = higher density on cold day, and low AD on hot day
If you study all of this, you will see that there is a lot of variables, that you can bring into the equasion. If every 8m difference in altitude, causes a 1mb change in barometric press, then it explains why we all got different readings. I noticed that the barometric press differed by as much as 6mb from the day before at my house, only 30km away, to the morning of the 1st round.
Take into account that we came from all over GP, Natal, and the Cape,with huge changes in barrometric pressure, with our turrets set to our local conditions. Then imagine the changes that occured in each rifle. Taking into account that your pellets trajectory, will change, with every change in environmental conditions, as described above.
Then we did not even take into account, the environmental changes that took place that day, over a short period of time. Like Temp, that varied from 14 deg celc - 26 deg celc.
Barrometric press that varied by at least 4mb, and humidity that swinged from as high as 89% in the morning, to 34% later during the day. This all caused havoc to the Air Density, the single factor influencing the bullets trajectory.
My meter, a (SILVA Pro) has a function to measure the "density altitude", and I never taken note of that. If it is so important to an aircrafts performance, then surely it must say something to me about the bullets flight path. I will now see if there is a direct corolation between this reading, and the air density reading.
If everybodys turrets were set up, at the same venue, at the same time, then we would have found more simular changes occuring to each rifle. That explain why we did not all expierience the same POI changes.
Proof of that, is that on day 2, we all expierience simular changes. None as big as on day 1.
So my conclusion is. Try to set up your turret at the venue, as close to the time, and conditions that you are going to shoot in. It will change from venue to venue, and from changing environmental conditions. Early mornings(cold and humid), through to midday (hot and less humid) and back to the afternoon, again.(cold and humid)
cold air = High AD + Humid air = low AD , with humidity playing the lesser role
Hot air = low AD + Dry air = high AD, with humidity playing the lesser role
I hope you can also see the light on the other side of the tunnel now, or is it a train comming.
--------------------------------------------------------------------------------
Last edited by Piet Skiet; 21-05-08 at 17:37.
Die meters wat ek gebruik is die Kestrel 4500 en ek het n Silva Pro ook gehad wat baie goedkoper is en net so oulik werk. Jy moet maar net dophou wat met jou POI gebeur en notas maak daarvan en ook al die ander data afskryf elke keer as jy gaan skiet. Daar sal vinnig n patroon ontwikkel. Ek skryf die datum, tyd,
Temp , Humiditeit, barometriese druk en dan veral die Density Altitude neer.
I finally cracked it!......... POI shift.
--------------------------------------------------------------------------------
After all my data collection over a year and a half, I finally have an answer for all our questions.
I have had a look at all the variables that I encoutered, over this long period, but could not come to a definate conclusion. But looking at what happened over the weekend of the Nationals, and taking notes as we went, I could not help to be even more confused as I was before.
The first day saw the most confusion, with everybody having different problems. Some shot low, others high, and some spot on, on their settings. The chronograph, however had most shooting to high.
It bothered me, because some of the people were recording completely opposite results, as what I expierience up to now. I went back to my previous thread of more than a year ago, "PCP, a strange world", and made a startling discovery. My recent findings, was 100% opposite, to what I found a year ago. This put me in a complete backpeddle mode, and after reading the link that Fox gave me back then, ://www.usatoday.com/weather/wdensity.htm
everything fell in place.
It says: HUMID AIR IS LIGHTER, OR LESS DENCE THAN DRY AIR AT THE SAME TEMP
1. Higher temp causes a decrease in Air Densityhttp2. Barometric press has an opposite effect on AD. Increasing press, increases AD
3. Altitude has a far greater influence on AD, than higher or lower press due to weather systems (it has a 1mb change, for every 8m) This is where the big discrepancys lie.
4. Air Density is lowest at high elevation, on hot day, when atmospheric press is low.
5. Air Density is highest at low elevation when the press is high, and the temp is low
6. Compared to the differences made by temp and barrometric press, humidity has a smaller effect on the AD, but humid air is lighter than dry air at the same temp
It goes further, and say that pilots use "density altitude" to relate air density to aircraft performance.
This is what affects Air Density :
High Air Density is caused by:
cold temp
High Barrometric pressure
Low Altitude
Low Humidity
Low Air Density is caused by:
Hot Temp
Low Barrometric pressure
High Altitude
High Humidity
High Altitude = Low AD, but cold day = high AD (like we had early morning, and late afternoon at Nationals)
High Altitude = Low AD, but hot day = low AD( like we had towards the middle of the day at Nationals).
Low altitude = higher density on cold day, and low AD on hot day
If you study all of this, you will see that there is a lot of variables, that you can bring into the equasion. If every 8m difference in altitude, causes a 1mb change in barometric press, then it explains why we all got different readings. I noticed that the barometric press differed by as much as 6mb from the day before at my house, only 30km away, to the morning of the 1st round.
Take into account that we came from all over GP, Natal, and the Cape,with huge changes in barrometric pressure, with our turrets set to our local conditions. Then imagine the changes that occured in each rifle. Taking into account that your pellets trajectory, will change, with every change in environmental conditions, as described above.
Then we did not even take into account, the environmental changes that took place that day, over a short period of time. Like Temp, that varied from 14 deg celc - 26 deg celc.
Barrometric press that varied by at least 4mb, and humidity that swinged from as high as 89% in the morning, to 34% later during the day. This all caused havoc to the Air Density, the single factor influencing the bullets trajectory.
My meter, a (SILVA Pro) has a function to measure the "density altitude", and I never taken note of that. If it is so important to an aircrafts performance, then surely it must say something to me about the bullets flight path. I will now see if there is a direct corolation between this reading, and the air density reading.
If everybodys turrets were set up, at the same venue, at the same time, then we would have found more simular changes occuring to each rifle. That explain why we did not all expierience the same POI changes.
Proof of that, is that on day 2, we all expierience simular changes. None as big as on day 1.
So my conclusion is. Try to set up your turret at the venue, as close to the time, and conditions that you are going to shoot in. It will change from venue to venue, and from changing environmental conditions. Early mornings(cold and humid), through to midday (hot and less humid) and back to the afternoon, again.(cold and humid)
cold air = High AD + Humid air = low AD , with humidity playing the lesser role
Hot air = low AD + Dry air = high AD, with humidity playing the lesser role
I hope you can also see the light on the other side of the tunnel now, or is it a train comming.
--------------------------------------------------------------------------------
Last edited by Piet Skiet; 21-05-08 at 17:37.