Why aren't cannon balls patched?

[bluez]

I remember years ago me and and a firend was shooting with a .495 cal rifle, all we did was to put a little paper on top of the powder, and the place the little underbore round ball on top.

The rifle made a puf and the bullet came out and hardly made a dent on the piece of wood i was aming on. Later we placed the ball in a pice of cloth with lube, great result. So why aren't cannon balls patched in the same way?

[Double D]

Do you remember when you added that patch how much harder it was to get the ball down the bore.

 The circumference of your .495 inch  ball is 1.55 inches.  That size ball was probably going into .50 caliber rifle which was about .510 inch diameter or circumference of 1.60.  The patch you added was probably .010. which made a combination of ball and patch diameter of .515 inches and circumferences of  about 1.61 inches of surface area of the ball in contact with the bore.  A difference of .010.

In a 1 inch cannon the circumference is 3.14 inches.  If you add a .010 patch  the diameter is now 1.020 and circumference is  3.2 inches in surface contact.  A difference of .060.  That increase in area in contact with bore increases friction used to seat the ball.  Add to the friction the increased mass and it take a great deal more force to seat the ball. 

Another factor is material used for the projectile. The soft lead of your 50 call deform and swages down to fit the bore. The iron use in cannons balls does not deform.  If you try to put a 1 inch iron cannon ball  in a 1 inch cannon bore it won't fit, the ball needs to be smaller.

[Cat Whisperer]

From another perspective, look at the area inside the bore.  As the ID goes from fractional to many inches the AREA subjected to the peak pressures grows quite a bit.  THe material is the same strength but the total forces add up to MUCH more.

Keeping an amount of windage keeps the sustained pressures much lower.

[flintlock]

I would expect the patch to burn through as well, heavy rifle charges burn patches, imagine what a pound of powder would do...

[Double D]

Here is a website that discussed the concept of windage and why.

http://www.arc.id.au/Cannonballs.html