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Topic: What kind of flags? (Read 272 times) previous topic - next topic

Re: What kind of flags?

Reply #15
@MJeff23

Ya but you don’t have your ass and rifle planted on concrete and you don’t have the major advantage of sighters to test the wind conditions before going to record rounds. And you are physically challenged with movement and obstacles! Even though I’m addicted to BR, I still shoot a lot of steel out to 1400. I have mucho respect for you guys in PRS. It’s a tough game.

Re: What kind of flags?

Reply #16
I think Ballistic AE has multiple wind measurements, I will have a look at it, great idea!
Jeff, my second last time out I had wind doing 180's. Where I shoot is in rolling hills in crop land.

Re: What kind of flags?

Reply #17
@MJeff23

Ya but you don’t have your ass and rifle planted on concrete and you don’t have the major advantage of sighters to test the wind conditions before going to record rounds. And you are physically challenged with movement and obstacles! Even though I’m addicted to BR, I still shoot a lot of steel out to 1400. I have mucho respect for you guys in PRS. It’s a tough game.

It's tough packing a 26# rifle and a 20# backpack for a out-of-shape man in his upper 50's playing in a young man's game.  But it is extremely fun.  I really wish the sport would've been around 30 years ago!  I've shot so much off a bipod for the last 3 years that I don't feel comfortable on a benchrest--I'd get embarrassed in a BR match. 
Jeff
First impressions are forever.....you don't get a second chance

Re: What kind of flags?

Reply #18
Significance of bullet drift created by close wind versus far wind is still in debate today. I know which side of the debate I am firmly on, but there is more to  a wind call than just wind speed and direction.

If you conjure up a magical 1000 yd range which has a full value (90° to the bullet path) 10 mph wind blowing only between the 0 -100 yd section, then dead still air between the 100 - 900 yd section, and then a 10 mph full value between the 900-1000 yd section, you can put some numbers into a ballistic calculator to evaluated the affect of a 10 mph wind on the bullet relative to the speed of the bullet at a specific distance from the muzzle and the distance that bullet still has to travel to get to the target.

Using my 6 Dasher chart with 103 gr Bullets (Vapor Trails for BC), MV is 3020 fps. From 0 to 100 yds a 10 mph full value wind will create a 0.4 MOA deviation at the 100 yd mark with a loss of 140 fps by the bullet through that distance. At 900 yds the same bullet would be traveling at 1833 fps and it will decelerate to 1720 fps by 1000 yds for a 113 fps drop between 900 - 1000 yds. Both fps drops are fairly similar. A 10 mph full value wind on this same bullet traveling at 1833 fps at the 900 yd mark will create a 0.9 MOA deviation by the time it hits the 1000 yd target.

So, 0.4 (4 tenths of an inch) deviation between 0 - 100 yds and 0.9 (9 tenths of an inch) between 900 yds and the target. No question: as the bullet slows the 10 mph wind creates a greater amount of deviation. However, the bullet with 0.4 MOA deviation between 0 - 100 yards still has 900 more yds to travel to the target and it’s already 0.4 MOA off course. The actual deviation of this bullet with NO other wind affects on it during the final 900 yds to the target shows as a 3.6 MOA (0.4 x 9) deviation when it arrives to punch a hole in the paper.

On target, the final 100 yards of 10 mph wind moved the bullet 0.9”; on target, the first 100 yds of 10 mph wind moved the bullet 3.6”. 
Bottom line: your close wind is at least as important and likely much more important than the wind way out there at 900 yds.

In real life, with wind active along the entire 1000 yard, bullet wind drift calculation will be much more complicated than this simplified example of looking at wind affect versus distance just in two segments of the total range.

I just threw these calculations together off my ballistic app as I was typing. I invite anyone to do the same scenario with their cartridge data and ballistic calculator. I may have missed something important on the way to generating the numbers. If so, let’s get me corrected. 😊

I’m a far cry from a wind reading expert and the example I just put together doesn’t mean much to me when shooting a record string. It’s almost unheard of to have a steady wind through the 0-1000 yd distance to target. When that occurs every flag on the range is doing exactly the same thing in the wind. I’ve never seen that happen. It’s more likely that the wind is blowing hardest along one section of the range and gentler some where else. It’s not uncommon to see the 900 yd flag standing straight out, the 600 yd flags at half mast and the 300 ones semi quiet. For a wind call I try to pay attention to where the wind is blowing hardest and then factor in the affect of that distance and the wind speed on the bullet. With a heavy wind close I expect more bullet drift than a heavy wind at the end of the range.  I still DQ with some of the vicious wind shifts we see at CRC, but when the wind is playing nice this system works well for me to get that first sighters on target. To get centered up from there, it becomes a combination of what is the bullet on target saying relative to how I’m actually reading the wind. You can learn a lot about specific wind behavior on an unfamiliar range simply by stopping after each sighter and evaluating the correlation between what you thought the wind was doing when you sent your round, versus what it was actually doing based on target POI. Many shooters who don’t take the time to do this will keep firing sighters until they are centered up, but when they get there, they don’t know how or why they got there. 

Think I may have found a glitch in my calculations! Stay tuned- doing more research.

Re: What kind of flags?

Reply #19
Prototype flag version 2 is 90% done, got a new idea though, gonna start version 2.5 tomorrow. It rotates very very easily however. I hate how by the time you get it almost done, a new idea pops up lol.

Re: What kind of flags?

Reply #20
Ok time for some corrections in my prior logic on bullet flight after the first 100 yds exposure to a full value 10 mph wind. Pull up the linked article written by Brian Litz. It’s one f the best I’ve read to clarify the nature of bullet deflection created by the wind.

https://www.ssusa.org/articles/2016/12/7/expert-forum-wind-shooting

The bullet diagram on page two shows the angular deviation of the bullet caused by the combined affects of oncoming airflow and the lateral push of a full value wind (lateral aerodynamic drag). The bullet is actually “crab walking” through the air because of two different wind forces affecting its flight path. In my prior description of a mythical range with no wind affect (dead air) between 100 and 900 yards, I said the 0.4MOA deviation seen at the end of the first 100 yards would be a constant for each additional 100 yards traveled resulting in at least a 3.6 MOA displacement when the bullet punched the target at 1000 yards. That is not correct in my opinion. The bullet in the diagram is at an angle as it is moving forward. It is not on a direct flight path of the angle shown. Consequently, when that crabbing flight passes into dead air the only aerodynamic affect on the bullet will be the line of sight air flow and it will stop crabbing and fly straight again.
I’m guessing though,  this bullet will still have more than 0.4 MOA  of deviation  by the time it travels 900 more yards to the target.  This “guess” is based on the fact that the bullet has to retain some of the lateral inertia generated through the first 100 yds of a 10 mph full value wind. It seems rational that the bullet will eventually regain line of sight travel to the target but lateral drift will continue to occur until the energy of that lateral inertia is expended.
No wonder this subject of near/far wind continues to be debated. Considering the new insight from the Litz article, I will temper my original conclusion to say, near wind is at least as important as far wind, but not necessary more so.

Go to the middle paragraph of page 4 in the Litz article. In a much more eloquent way, he has discussed what I was trying to say earlier. It almost doesn’t matter ballistically what wind (near or far) has the most computed affect on bullet flight. In competition, the experienced shooter is going to be flexible enough to analyze the sum of the different wind affects through the whole flight path of the bullet and pay most attention to the ones showing the most affect regardless of where they are located down range.

Re: What kind of flags?

Reply #21
Wow great info, look like I have a good bedtime reading for my wife, should put her right to sleep and I will lie awake thinking about wind till 2:00 am lol.
ow that you mentioned "crab walking", back in my archery days we shot 100 meters. Sometimes we would hide behind a target backstop at mid field, you really could see the arrow fighting ( crab walking ) against the wind. We use to tune our arrow to have a 12-13% front of center balance point, it would drag the back half of the arrow, that was crab waking, over and over on the way to the target. Fun to watch. You could also see the arrow overspin sometimes if the shooter fletched with too mush helical angle, or if the vanes were not at equal angle from each other. Accuracy would suffer drastically.

Re: What kind of flags?

Reply #22
I gave up on changing the design for now, it spins nice, but I want to change a few things on the next one. It should work good to test at the very least. I have the two white UHMW pieces screwed together, but the next one I need to have them drilled at the joint with a smaller than arrow diameter to be able use it as a clamp.  As it sits the arrow is free to spin in the UHMW and I just have 3m vulcanizing tape around it to stop it from horizontal movement.  When I am able to clamp the next prototype, the the flag can be up instead of down.

Re: What kind of flags?

Reply #23
That looks like a fun project. Is the flag one color one one side and a different color on the other side?

Re: What kind of flags?

Reply #24
No this one is not, would that be better for head/tailwinds?

Re: What kind of flags?

Reply #25
No this one is not, would that be better for head/tailwinds?

Easier to judge at a glance which way the wind is coming from. I like your flags let me know if you take orders LOL
Dave

Re: What kind of flags?

Reply #26
Easier to judge at a glance which way the wind is coming from. I like your flags let me know if you take orders LOL
Lol they have a ways to go yet. Thanks for the compliment though.