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Subject: Fin stabilized rounds and wind deflection
Jeff_F_F    9/8/2008 2:30:11 PM
I've heard that fin stabilized rounds tend to fly upwind as wind pushed the finned tail further downwind than the head of the projectile causing it to turn into the wind. If this is the case, could a round be designed that had small fins on the head of the projectile as well which would not entirely stop this effect but control it so that the round turned just far enough into the wind to minimize defelection errors due to windage? Perhaps not a perfect solution but enough to reduce the number of variables that a low tech weapon system and/or less highly trained gunners would have to deal with to get reasonable accuracy?
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Softwar       9/8/2008 2:56:02 PM
I'm sure there are others with better aerodynamic experience than I but I suspect this is not a solution for an unguided projectile.  The drag on the forward (canard) would have to be equal to the rear set of fins.  This is an unstable configuration that could cause the shell to tumble in flight.  In addition, the extra drag will cause a significant reduction in the speed of the projectile. 
Canard fins are traditionaly used with guided missiles.  Missiles such as Sidewinder have two pairs of forward canard fins linked to the I/R guidance system.  The rear fins are balanced but uncontrolled using a windgenerator - gyro - which stabilizes the rear of the missile in flight - to follow where the seeker head is pointing.
The RAM - or rolling airframe missile uses a single pair of canard fins in a spin stabilized mode - so the fins move according to the guidance seeker as the missile revolves in a 360 rotation patttern.  This system is also used by the Russian Kornet if I am not incorrect - with a passive laser guidance in the rear to activate the pair of canard fins as it rotates in flight around the laser beam.
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neutralizer       9/9/2008 4:54:39 AM
I realise tanks may do things differently, but this is an artillery page and the only finned proj are rkts/missiles.  Unguided rkts are susceptable to low level wind at launch, at least some systems have used devices to measure low level wind speed and direction in th launch area and update the firng data to allow for it.  Of course gunners sldom see their target and aim by using computed firing data, this included allowance for wind, etc, accordong to the conditions of the moment and the proj's ballisitc characteristics.
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Jeff_F_F       9/10/2008 5:40:48 PM
Also mortars, recoilless rifles and such. Not so much in terms of modern technology but general ballistic principles with an intrest in alternative historical technologies.
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