There was some hint
- Thread starter Pete Wass
- Start date
Gene Beggs
Active member
Pete, Ralph Stewart had a density altitude instrument that worked well and was in contact with those who make it. Maybe he will chime in here and give us the details. Ralph, you out there buddy?
I have given a lot of thought to it lately and am wondering whether or not we could simply use barometric pressure alone for our tuner adjustment charts.
As someone pointed out, I believe it was Jerry Sharrett,,,we pilots live and die by density altitude, so it's understandable why I would use that value, but I'm wondering if it is necessary to go to that extent. The only thing that matters as far as the bullet and internal ballistics is concerned is the weight of the atmosphere.
It may very well be that if we could accurately determine barametric pressure with a simple barometer and disregard correcting it to sea level as we do in aviation, that it would be unnecessary to figure density altitude.
Arnold Jewel, you out there, Buddy? What do ya' think?
I hope I haven't opened a can of worms here and confused the issue. A lot of people are so hung up on this density altitude thing they have lost sight of the fact that you can use a tuner perfectly well knowing absolutely nothing about barametric pressure, DA, etc., if you will simply fire two or three sighters and adjust the tuner/focus ring to bring the rifle into tune each time you go to the line.
You notice I frequently make use of the word, 'Focus Ring', and that is the best way to think of my type of tuner, it's a focus ring! You don't need to know anything about temperature, density altitude, phase-of-the-moon etc., to focus your scope; do you? Of course not! And the same thing is true of my kind of tuner. The ONLY reason for monitoring density altitude is so we can accurately predict what the new tuner setting will be before going to the line. In other words, stay ahead of the changes in atmospheric conditions rather than reacting to them after the fact.
Later,
Gene Beggs
Joe Duke
Active member
DA Meter
Look in the classifieds under equipment / other. The one listed there is someqhat cheaper than a Kestrel 4000.
The nice thing about a Kestrel 4000 is that it records data at whatever time interval you set up. It also has a wind meter. I think the wind speed recorded is the instantaneous speed at the moment of recording and not average for the period. Someday I might even figure out how to use mine. It still won't aim the rifle.
Joe
Look in the classifieds under equipment / other. The one listed there is someqhat cheaper than a Kestrel 4000.
The nice thing about a Kestrel 4000 is that it records data at whatever time interval you set up. It also has a wind meter. I think the wind speed recorded is the instantaneous speed at the moment of recording and not average for the period. Someday I might even figure out how to use mine. It still won't aim the rifle.
Joe
Pete Wass
Well-known member
Interesting thought Gene
You certainly are in a position to test it out. Question: will one need to know the altitude they are at when the shooting day begins or is that what you meant by correcting for sea level?
Just as an asieide: prior to shooting Benchrest I fished most of the time I wanted to recreate. I bought an Airguide Fishing Barometer and used it . The barometer has Good fishing in the center of the face, Poor fishing to the left and Average fishing to the right.(good fishing is between 29.8 and 30.2) It has to be corrected for altitude, which is what brought fourth the question. I found it to work, by the way. When the pressure is below 29.8, fishing usually sucks.
Pete
Pete, Ralph Stewart had a density altitude instrument that worked well and was in contact with those who make it. Maybe he will chime in here and give us the details. Ralph, you out there buddy?
I have given a lot of thought to it lately and am wondering whether or not we could simply use barometric pressure alone for our tuner adjustment charts.
As someone pointed out, I believe it was Jerry Sharrett,,,we pilots live and die by density altitude, so it's understandable why I would use that value, but I'm wondering if it is necessary to go to that extent. The only thing that matters as far as the bullet and internal ballistics is concerned is the weight of the atmosphere.
It may very well be that if we could accurately determine barametric pressure with a simple barometer and disregard correcting it to sea level as we do in aviation, that it would be unnecessary to figure density altitude.
Arnold Jewel, you out there, Buddy? What do ya' think?
I hope I haven't opened a can of worms here and confused the issue. A lot of people are so hung up on this density altitude thing they have lost sight of the fact that you can use a tuner perfectly well knowing absolutely nothing about barametric pressure, DA, etc., if you will simply fire two or three sighters and adjust the tuner/focus ring to bring the rifle into tune each time you go to the line.
You notice I frequently make use of the word, 'Focus Ring', and that is the best way to think of my type of tuner, it's a focus ring! You don't need to know anything about temperature, density altitude, phase-of-the-moon etc., to focus your scope; do you? Of course not! And the same thing is true of my kind of tuner. The ONLY reason for monitoring density altitude is so we can accurately predict what the new tuner setting will be before going to the line. In other words, stay ahead of the changes in atmospheric conditions rather than reacting to them after the fact.
Later,
Gene Beggs
You certainly are in a position to test it out. Question: will one need to know the altitude they are at when the shooting day begins or is that what you meant by correcting for sea level?
Just as an asieide: prior to shooting Benchrest I fished most of the time I wanted to recreate. I bought an Airguide Fishing Barometer and used it . The barometer has Good fishing in the center of the face, Poor fishing to the left and Average fishing to the right.(good fishing is between 29.8 and 30.2) It has to be corrected for altitude, which is what brought fourth the question. I found it to work, by the way. When the pressure is below 29.8, fishing usually sucks.
Pete
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TomD
e publius unum
One of your preflight items is dialing in current barometric pressure into the altimeter. Altimeters work by measuring change in barometric pressure but assume that all change is a result in altitude change by the plane. If you land at a field with an altitude of 1100 feet above sea level and park overnight, the pressure may change. Say high pressure is coming in and you get back to the plane the next day and the altimeter may be reading 550 feet because the pressure has gone up. Dial the altitude to where it should be and dial in a good local pressure and you're corrected good to go.
Pete Wass
Well-known member
I understand that Tom
being a private pilot myself. I just wondered if one sets up a system at say 200' ASL and has it pegged to that altitude then one goes to Huston, let's say or N'orlens where the altitude may be, say - 30', won't one need to know what the actual barometric pressure is, corrected for that altitude? Does not the difference in altitude change the system? Am I reading too much into this?
being a private pilot myself. I just wondered if one sets up a system at say 200' ASL and has it pegged to that altitude then one goes to Huston, let's say or N'orlens where the altitude may be, say - 30', won't one need to know what the actual barometric pressure is, corrected for that altitude? Does not the difference in altitude change the system? Am I reading too much into this?
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Gene Beggs
Active member
Guys, I'll play around with this a little and see if I can find a way to simplify things. I'm thinking that you could take an altimeter and zero it after you get the rifle in tune. Then, if the altimeter showed an increase in altitude, that means that the weight of the atmosphere has decreased and vice versa. It should not be hard to develope a formula/chart to coincide with this.
In the meantime, I assure you, density altitude works.
Later,
Gene Beggs
In the meantime, I assure you, density altitude works.
Later,
Gene Beggs
Boyd Allen
Active member
Gene,
I believe that there are air density meters (of the sort that race engine tuners might use) for around a hundred dollars. It may be that one would have to pay attention to fractions of a percent, but the information might be just a good for adjusting a tuner.
http://motors.shop.ebay.com/items/air-density_W0QQ_nkwZairQ20density
I believe that there are air density meters (of the sort that race engine tuners might use) for around a hundred dollars. It may be that one would have to pay attention to fractions of a percent, but the information might be just a good for adjusting a tuner.
http://motors.shop.ebay.com/items/air-density_W0QQ_nkwZairQ20density
Pete Wass
Well-known member
A friend sent me
an advert of one on the JEGS site. It said nothing about altitude. I know that people who race vehicles pay attention to altitude or is it air density @ altitude. At the Continental Divide Dragway for instance, they have to pay attention to altitude because the air is less dense as it seemed to be the last time I was on Pikes Peak. Isn't that pretty much a function of altitude? Does that matter in terms of a projectile flying through it?
an advert of one on the JEGS site. It said nothing about altitude. I know that people who race vehicles pay attention to altitude or is it air density @ altitude. At the Continental Divide Dragway for instance, they have to pay attention to altitude because the air is less dense as it seemed to be the last time I was on Pikes Peak. Isn't that pretty much a function of altitude? Does that matter in terms of a projectile flying through it?