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03-22-2006, 02:16 PM
convergance explained with graphics please as i dont really understand how 200m is any different to say 300 or even 500m, surely if you have set to lets say 500 that will hit from farther away and if plane like closer lets say 200m you will still hit it surely, but if you set to 200m only then u cant hit anything that is like 500m away, so is it not just better to set to 500m and hit everything upto 500m away and closer, or am i on the wrong track here ?, thx

Art-J
03-22-2006, 02:55 PM
The convergence describes a distance to a point where bullet streams from each gun intersect with each other. Example drawing, with view from above of two conv. ranges set (250 & 300 yrds), here:
http://www.simhq.com/_air/air_031d.html

Sure, If You set it to 500m, You can still shoot at anything up to 500m, but only at 500m all Your bullets will meet in one point on a target (at least in theory - natural bullet spread makes it a little bit more difficult). If the plane You're shooting at is closer than 500m, than You will be only able to precisely hit it (in the engine for example) only with Your left or right guns, not both.

Cheers - Art

VW-IceFire
03-22-2006, 03:22 PM
convergance explained with graphics please as i dont really understand how 200m is any different to say 300 or even 500m, surely if you have set to lets say 500 that will hit from farther away and if plane like closer lets say 200m you will still hit it surely, but if you set to 200m only then u cant hit anything that is like 500m away, so is it not just better to set to 500m and hit everything upto 500m away and closer, or am i on the wrong track here ?, thx
I don't have a diagram on hand but I'll try and explain it here. If not..on TeamSpeak.

Convergence is terribly important if you're flying a aircraft with wing mounted guns. It is less important, although still relevant, for aircraft mounting guns in the nose or near the centerline.

What happens is that when you set convergence you set a point where all of the guns will pass roughly through the crosshair. If you set convergence at 200m then the guns, at 200m, will pass through the crosshair and then fall away. If you set the guns at 500m then the bullet stream will pass through the crosshair at that range instead of closer in at 200m.

Whats the difference? Setting a convergence at 500m means that you need to be firing at a much more difficult distance to hit your target...it also means that if you shoot at an aircraft closer than your convergence that you are spreading your bullets out. You may infact miss an aircraft depending on the angles and types involved when your convergence is set so far out.

Similarly...if you set a convergence that is too close...then shooting at longer ranges is ineffective as the spread is going to be much higher. To effectively destroy an enemy aircraft...you need to it it with as many of your guns, sometimes repeatedly, in the same spot. Its no good to just hit the aircraft....you must hit it in a single point to do effective damage. So the ideal way to do this is for all of your guns to hit the aircraft, at the same time, in nearly the same point. It does you no good if half of your guns are missing because they are aimed much further ahead. I'll see if I can photoshop something up.

Chuck_Older
03-22-2006, 03:41 PM
http://img.photobucket.com/albums/v441/Chuck_Older/conv.jpg

For nose mounted weapons, no bullet streams cross. However, gravity effects the ammunition when fired, so the gun needs to be sighted to take your 'convergance' (in this case a misnomer) range into account

slipBall
03-22-2006, 03:42 PM
SO then should your convergence distance be set differently, depending on aircraft chosen, and the weapon balistic power of her guns. A more powerfull weapon's having a greater distance set for convergence

Chuck_Older
03-22-2006, 04:16 PM
That shouldn't have anything to do with it. 300m should be 300m, the muzzle velocity of the weapon should not matter- 300m convergance should set the convergance to 300m for that weapon. When you set 300m as convergance, that doesn't mean 300m for .303 rounds, so tweak it to 250 for the same convergance with 20mm cannon if you change aircraft

range is range, don't over-complicate http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

horseback
03-22-2006, 04:27 PM
Different types of guns have different ballistics; that means that your 7.9mm machine gun fires a round with a different trajectory than the round fired from your MG151/20mm cannon. The guns' mountings and the gunsight are adjusted so that the trajectories cross (or at least have their closest point of approach) at the point apparently at the center of your gunsight's crosshairs.

That's for nose-mounted armament, and since the bullets are fired more or less parallel to the aircraft's line of flight, long range shots are simplified if the up/down factor of the trajectory of your main battery can be reliably estimated.

The wing mounted armament presents a slightly different problem. If the guns are aligned in such a way that they fire in parallel with the aircraft's line of flight, you will either hit only your target's wings or fuselage with HALF your firepower at best. Therefore, the guns are 'toed in' at a slight angle to hit a spot (or series of spots) at, or slightly above, the aircraft's line of flight at a specific distance from the aircraft, and the gunsight is also adjusted to center at that point. As a result, wingmounted armament is most effective at or near convergence range, because the rounds' paths cross at convergence and spread apart the farther from convergence they go.

Again, when weapons of differing ballistics are involved, that also has to be taken into consideration.

Hope this helps.

cheers

horseback

VELCRO_FLY
03-22-2006, 04:33 PM
This may be a dumb question. I understand convergence, but does that mean that if my convergence is set to 300m then I should start firing when a plane is at .30 from me to get the maximum effect?

Chuck_Older
03-22-2006, 04:51 PM
horseback-

100% agreed, for real life applications

However, in the simhttp://forums.ubi.com/groupee_common/emoticons/icon_smile.gif , range should be range. There should be no reason to figure out that your lower velocity round needs more convergance than a 'raw' 300m to actually reach 300m, when you set it to 300m, it should be set to 300m, and that's that

Aviar
03-22-2006, 04:53 PM
Originally posted by VELCRO_FLY:
This may be a dumb question. I understand convergence, but does that mean that if my convergence is set to 300m then I should start firing when a plane is at .30 from me to get the maximum effect?

Bingo. You now understand convergence...http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Aviar

RubberDuckski
03-22-2006, 05:17 PM
Don't worry about convergence at 500 metres. Set your guns and cannon to 150 metres.

Remember, if you think you're close, get closer. The difference in destructive effect is massive.

tigertalon
03-22-2006, 05:43 PM
The issue is important not because of horisontal convergence, but vertical one!

On Fw190s I always set my inner guns to 500 or even to 1000m, as this makes bullets fly much flatter in my sight (I don't give a .... where they will cross over in horisontal, 100 or 500, the same - for inner guns).

In PF convergence affects horisontal and vertical movement of shells.

VW-IceFire
03-22-2006, 06:18 PM
Originally posted by RubberDuckski:
Don't worry about convergence at 500 metres. Set your guns and cannon to 150 metres.

Remember, if you think you're close, get closer. The difference in destructive effect is massive.
150 meters may work for you...but it does not for me. I tried it...its devastating but ultimately not as flexible as I'd like it. Strafing runs with 150m convergence is an excercise in frustation. Works for you...not for me. We have to be careful to confuse our own preferences and skill sets with other people.

For someone new to this...we need to impress upon them that experimentating and finding their own comfort zone with convergence is key.

VW-IceFire
03-22-2006, 06:19 PM
Originally posted by slipBall:
SO then should your convergence distance be set differently, depending on aircraft chosen, and the weapon balistic power of her guns. A more powerfull weapon's having a greater distance set for convergence
Even if the aircraft has completely different guns with differet trajectories...the guns are still going to converge at the given distance. What will be different is the trajectory and speed in which they arrive at that given point.

DaimonSyrius
03-22-2006, 07:05 PM
This is very similar to what Chuck_Older posted, but adds the aspect of harmonisation of several wing-mounted guns. A partial harmonisation adjustment can be done in IL2 for some planes, when there are two different sets of guns that are fired with separate triggers and have separate convergence settings (for instance, the P-47, but not the P-51):

http://www.infonegocio.com/daimon/img/Harmonisation.gif

And this other one shows an often-overlooked aspect of adjusting your convergence, the elevation angle to account for the parabolic trajectory drop (or setting for convergence in the vertical plane). This affects nose guns as much as wing-mounted guns, despite the common comment about "no need to worry about convergence for a nose cannon":

http://www.infonegocio.com/daimon/img/Trajectory-drop.gif

Both come from (and are explained in) this excellent page on Ballistics (http://www.geocities.com/CapeCanaveral/Hangar/8217/fgun/fgun-th.html)
(However, the picture backgrounds look lousy against this forum's http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif)

The whole web site is a very comprehensive source about gunnery. Homepage: The WWII Fighter Gun Debate (http://www.geocities.com/CapeCanaveral/Hangar/8217/fgun/fgun-in.html)

Cheers,
S.

tigertalon
03-23-2006, 01:53 AM
Originally posted by DaimonSyrius:
And this other one shows an often-overlooked aspect of adjusting your convergence, the elevation angle to account for the parabolic trajectory drop (or setting for convergence in the vertical plane). This affects nose guns as much as wing-mounted guns, despite the common comment about "no need to worry about convergence for a nose cannon":

http://www.infonegocio.com/daimon/img/Trajectory-drop.gif

Hm, this picture is a bit questionable, as the "red" bullets have higher muzzle velocity than "blue", something which of course cannot be altered by convergence...

DaimonSyrius
03-23-2006, 02:37 AM
Originally posted by tigertalon:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">http://www.infonegocio.com/daimon/img/Trajectory-drop.gif

Hm, this picture is a bit questionable, as the "red" bullets have higher muzzle velocity than "blue", something which of course cannot be altered by convergence... </div></BLOCKQUOTE>
Hmmh... questionable remark, tigertalon http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif

Have you actually bothered to read the text explaining the figure, which I linked too?

Ballistics (http://www.geocities.com/CapeCanaveral/Hangar/8217/fgun/fgun-th.html)

In vacuum the projectile would retain its horizontal speed, and follow a parabolic curve (red). In air the projectile encounters drag, a speed-dependent force. The air molecules absorb part of the energy and momentum of the projectile, while the friction converts some of the energy to heat. In general this results in a trajectory that is more curved (blue), although a properly designed round might actually have some body lift, counteracting gravity. The line of sight is made to coincide as close as possible with the curve over the ranges expected in combat (green). Often the guns are given a slight upwards angle, to make the match easier. For guns in the wings this is convenient, because the wings have a positive angle of attack.

Same muzzle velocity, different theoretical conditions.

http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif

Cheers,
S.

slipBall
03-23-2006, 02:56 AM
Originally posted by Chuck_Older:
That shouldn't have anything to do with it. 300m should be 300m, the muzzle velocity of the weapon should not matter- 300m convergance should set the convergance to 300m for that weapon. When you set 300m as convergance, that doesn't mean 300m for .303 rounds, so tweak it to 250 for the same convergance with 20mm cannon if you change aircraft

range is range, don't over-complicate http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

I think the point that I tried to make, and horesback's statement have to be considered in this sim. A weapon with less velosity, and bullet mass, should be set to converge at a shorter distance. And more powerfull weapon's allowing for greater converge distance to be set. I think that weapon velosity, and mass, were modeled into this game. I might have read it in one of the training track's

tigertalon
03-23-2006, 10:30 AM
@ DaimonSyrius:

Initial poster started topic on convergence. You posted this in your initial post in this thread:

Originally posted by DaimonSyrius:
This affects nose guns as much as wing-mounted guns, despite the common comment about "no need to worry about convergence for a nose cannon":

http://www.infonegocio.com/daimon/img/Trajectory-drop.gif

I think it is not unreasonable for one to assume this picture has something to do with "nose cannon convergence". However, it doesn't. It is a matter of drag, or media in which bullet flies if you want (as both, red and blue bullet leave the barrel at same angle but different speeds). However, here we are discussing about bullets that leave the barrel all at same speeds, but different angles.

03-23-2006, 11:03 AM
thx guys i think all these post's have helped me alot and nice piccys to, as a noob i think i will stick with 250 or 300m for both guns at the moment i think that will be safest for now. thx again guys

DaimonSyrius
03-23-2006, 11:14 AM
Originally posted by tigertalon:
Initial poster started topic on convergence. You posted this in your initial post in this thread:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DaimonSyrius:
This affects nose guns as much as wing-mounted guns, despite the common comment about "no need to worry about convergence for a nose cannon":
</div></BLOCKQUOTE>
What you're saying now is true, but it isn't the complete truth about what I posted, as you know well since you edited out a significant bit http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif
The 'elevation' issue (which you have removed in your quote) is what affects guns regarding convergence settings, and that is shown in the picture, and is discussed in the text I linked.

Originally posted by tigertalon:
I think it is not unreasonable for one to assume this picture has something to do with .../...
I never said (nor meant) it was unreasonable. I said that to just put a 'questionable' stamp on the picture without having looked at the text that goes along with it -and was pointed at and linked- is as much a questionable thing to do http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif In other words, I was pointing to the 'questionable' label based on just an assumption when the full text was easily available.

Please have a look at the web site, it's a good one (IMO).

Cheers,
S.

Tully__
03-23-2006, 05:47 PM
Another diagram showing how convergence setting affects shooting in the game:

http://jennirivers.actewagl.net.au/convergence.jpg

The vertical change (range setting) is usually independant of the convergence in real life and with most more advanced sights could be adjusted by the pilot in flight.

antifreeze
03-25-2006, 12:39 PM
Just to add, I found it very helpful to do some scale-drawings in plan (view from above).

Drew some centrelines 50cm long on three sheets of A4 taped together (=500m).
At the bottom, drew my plane's wingspan across the centrelines. 1cm long = 10m wingspan.
Put guns (dots) half way along each wing.
Drew converging lines from the guns going through 150m (15cm), 300 (30cm) and 500m (50cm) on the centrelines.
Drew the 10m wingspans of the enemy at varous distances up the centrelines.

I could much better imagine where my bullets were going to hit the enemy aircraft. For instance, with convergence set to just 50m I could see that the bullets would still hit a fighter halfway up its wings at 100m, after crossing over the convergence point. but it would be useless to fire at a fighter who was more than 120m away.
Another example. With convergence set at 300m, I could see that at 200m, the bullets would hit the wings of a fighter where they meet the fuselage on each side (not a bad place). However, at 50m or nearer the damage would be on the tips of the wings; a case where 'nearer is not necessarily better'.

The difference of course is that wings come off easily when both guns are pointing at the same place, but if the guns are pointing at different parts of an enemy, then the destruction will be more 'widespread' and perhaps less devastating, so it's handy to know where they might be hitting.