beautiful sunny sunday

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Chris B
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Re: beautiful sunny sunday

Post by Chris B » Tue Jan 14, 2020 12:29 pm

Sandro -

Approximate figures again...

Using a 32 pound cannon ball (let's call it 15 kg) with a muzzle velocity of 450 m/s, I get an initial recoil velocity of 2.25 m/s. But on a real gun deck in the real world I'd expect inertia, friction and rolling resistance to reduce that figure, and the velocity would decrease further as the gun tackles braked the movement.

Even with the momentum associated with a 3 tonne gun carriage it initially doesn't sound too bad. 3 tonnes at 2.25 m/s sounds like a manageable situation. But the numbers on paper that make it look comfortable to deal with only apply if the gun deck remains horizontal. If the gun is fired at the peak of an upward roll of the ship - which I understand was common practice - then the carriage will be recoiling down an inclined plane. We're into sines and cosines now, but the calculated net force on the gun carriage on an inclined plane (rolling deck) will be helping the recoiling gun's 3 tonne mass on its way. Which perhaps helps to explain why the restraining breech rope was of considerable diameter!

I wonder if there's an 18th century gunnery expert out there who can help us put some meat on the bones of this hypothesising!

C

Sandro Picchio
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Re: beautiful sunny sunday

Post by Sandro Picchio » Tue Jan 14, 2020 3:25 pm

Chris,

So we have now the missing datum: 450 m/s
I would not know how to reckon the resistance of oak wood to penetration but to my eyeball 1 metre looks a little too thick.

Why worry about the cannon ball diving too near? Just a few degrees of elevation solve the problem!

Yes, 2.5 m/s = 8.1 km/h, manageable.

I looked for and found some old pictures of naval guns and they show both the tackles and the huge diameter breech rope.

I had not thought of the rolling angle adding to the mechanical gun elevation. The gunners must have a very good eye for firing at the correct moment aka real elevation on a rolling ship. Moreover there was a time delay to take in account, between the torch lighting the external powder and the round going off.
I think that the balls missing the target were a fair large percentage, unless at very short range.

I wonder if the gun crew had the time to wait for the rolling deck help them to pull the gun carriage outboard.


Sandro

Chris B
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Re: beautiful sunny sunday

Post by Chris B » Tue Jan 14, 2020 4:01 pm

Sandro -

Re:
I would not know how to reckon the resistance of oak wood to penetration but to my eyeball 1 metre looks a little too thick.
Yes, it's impressive isn't it? I read about the 1 metre penetration through oak in a technical article about the history of naval gunnery. I don't know if the figures were verified with practical experimentation, but the ballistics chap who did the mass / velocity calculation reckoned that at short range, penetration through 1 metre of oak was a distinct possibility. That said, I can see that in the real world there would be a number of variables to consider, some of which would modify energy dissipation on impact - and could therefore be expected to alter a result predicted by mathematics.
Why worry about the cannon ball diving too near? Just a few degrees of elevation solve the problem!
Yes indeed! But for maximum penetration you'd need short range and zero elevation, to ensure the shot would traverse a short line that's as near perpendicular as possible to the plane of the target.

I had not thought of the rolling angle adding to the mechanical gun elevation. The gunners must have a very good eye for firing at the correct moment aka real elevation on a rolling ship. Moreover there was a time delay to take in account, between the torch lighting the external powder and the round going off.


Absolutely. Must have involved lots of training and practice!

I wonder if the gun crew had the time to wait for the rolling deck help them to pull the gun carriage outboard.


Well I don't know. But I'm certain that when the situation allowed, they'll have applied good seamanship and routinely used the motion of the ship to their advantage whenever possible. Same as we do today on our sailing boats.

Chris


Chris B
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Re: beautiful sunny sunday

Post by Chris B » Tue Jan 14, 2020 5:32 pm

Sandro -

Returning briefly to your comment about gun tackle operation, which I apologise for missing earlier...

As you correctly suggest, if the available space had allowed the gun crew to haul in the opposite direction (i.e. with the mechanical effort on the travelling block) then the mechanical advantage would have been 3:1. However, limited space meant that the outhaul (tail) of the gun tackle had to be hauled inboard by the gun crew, giving a mechanical advantage (before losses) of 2:1.

That might be historically why, in my part of the world, a simple 2 sheave tackle is generally still thought of as a 2:1 gun tackle, regardless of whether it's rigged to advantage (3:1) or not (2:1).

C

Chris B
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Location: England

Re: beautiful sunny sunday

Post by Chris B » Wed Jan 15, 2020 12:44 pm

Sandro -

Re: cannon ball penetration...

The following is an extract from a table compiled in the late 18th century by the Royal Navy. The figures are empirical measurements generated by experiments using captured French naval cannons. (At that time, the data was of value to the designers of British warships).

The target material was oak. The cannon ball was cast iron with an assumed SG of 7.1. (The SG was assumed rather than precise, due to the likely presence of invisible casting voids inside the ball). The muzzle velocity is unknown.

The original table uses imperial measurements. I've converted them to metric.

Target material: Dry English oak
Ball weight: 10.88kg (24 pounder)
Propellant charge: 5.44kg black powder
Distance to target: 91.44 metres.
Depth of penetration: 1.498 metres.

Interestingly, the 24 pound ball had far greater penetrating power than a 32 pound ball. However, the 32 pound ball did considerably more damage inside the target vessel, partly due to the heavier ball's energy dissipation ripping huge splinters from the inner surface of the target ship's timber.

C

Sandro Picchio
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Re: beautiful sunny sunday

Post by Sandro Picchio » Wed Jan 15, 2020 7:20 pm

RE cannon ball penetration

Quote Interestingly etc.
One would think the opposite round but experiment is experiment.

Pro 32 pounds: a greater mass/cross section area ratio, that is more power related to resistance.
Pro 24 pounds? perhaps a greater impact speed?

Anyway one metre and a half is very impressive.
I doubt any warship has been built with such a planking thickness. Even hulls designed for staying through out the winter in the ice vise, like the Fram had lesser plankings. How thicks are the double nestled plankings of H.M.S. Victory?

I read somewhere that most wounds were caused by splinters and much care was used in avoiding the possibility of producing splinters.
Could have read that in "Life in Nelson Navy", a very interesting book of which presently I can't tell Author nor Editor because I borrowed it from my son.

Re elevation
The impact angle would be very near 90° , moreover also the enemy ship was rolling and also she probably had a remarcable tumble-in in the sides, but we are drifting in trifles that surely did not bother an 18th century captain or gunner in angry action.

Sandro

Sandro Picchio
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Re: beautiful sunny sunday

Post by Sandro Picchio » Wed Jan 15, 2020 7:26 pm

Sorry, I was not clear, obviously the possibility of producing splinters was from the point of view of the receiving ship.

S

Chris B
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Re: beautiful sunny sunday

Post by Chris B » Wed Jan 15, 2020 9:41 pm

HMS Victory's hull is approximately 70 centimetres thick at the waterline.

I'm not sure why a 24 pounder apparently had more penetrating power than a 32 pounder. I do know, however, that a 24 pound ball tended to punch a relatively clean hole through thick planking, but a 32 pound ball did a less tidy job - and more or less ploughed its way through hardwood, causing immense damage. I wonder if the anomaly might have something to do with the mechanical structure of timber, rather than the physics of ballistics. Alternatively, the number of variables might make direct comparisons difficult and misleading. For example, the propellant charge size varied according to gun construction, barrel length, calibre, target range, and of course the gun captain's preferences in a particular situation. Also, dry black powder burned faster and released its energy far quicker (giving a much bigger propulsive punch) than damp powder etc. etc. So it's possible that an attempt at direct comparisons, unless made under very carefully controlled conditions, might have produced misleading results - especially if the information of interest was reported / recorded some time after the event. In other words, objectivity might sometimes have suffered and skewed the data! I don't know...

For instance, HMS Victory's 32 pounder guns could reportedly (N.B. I can't find any hard data to support this claim) penetrate a 1 metre thickness of oak at a range of 1 nautical mile. Then there are contemporary accounts of cannon balls fired at medium to short range passing in through one side of a targeted ship, and smashing their way out through the other side. Which sounds impressive and plausible, but it's probably not what you want to happen (if you're the attacker), because your cannon ball has only made a pair of holes. It has not been stopped by anything of structural importance inside the targeted ship. The old Royal Navy gunnery table I've seen possibly offers the most objective comparisons between the firepower of different weapons, and might be as close as we're going to get to the truth.

In any event, it seems that far more deaths and serious injuries were caused by massive splinters and flying debris, rather than by direct impact of cannon ball on personnel. Oak was strong but the exit wound (on the inboard side of the hull structure) tore out huge splinters that killed, dismembered, or otherwise injured personnel - whereas softer timbers were more easily penetrated by shot but the splintering was generally viewed as being somewhat less dangerous. "Less dangerous" being a strictly relative term in this context!

Regarding gun elevation etc... In good weather conditions and when aiming at a target's hull (as opposed to going after the target's rig), the Royal Navy's master gunners sometimes didn't set the elevation. To speed up the load / aim / fire cycle they would use zero barrel elevation, fire the gun, and the master gunner would watch the splashes as the fired ball skipped across the surface of the water towards the target. Which I imagine would have been a somewhat disconcerting sight if you happened to be watching the same thing from the targeted vessel. The 32 pounders on HMS Victory's lower gun deck were only a few feet above the waterline, which possibly helped to make this tactic quite effective.

C

Raya
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Location: Hope Island

Re: beautiful sunny sunday

Post by Raya » Wed Jan 22, 2020 5:49 am

"I read somewhere that most wounds were caused by splinters and much care was used in avoiding the possibility of producing splinters.
Could have read that in "Life in Nelson Navy", a very interesting book of which presently I can't tell Author nor Editor because I borrowed it from my son."


MEN-OF-WAR
Life in Nelson's Navy
Patrick O'Brian
ISBN 0-393-32660-8

This is the book that Sandro referred to. There is a PDF copy of it on Libgen for those that way inclined.

Sandro Picchio
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Re: beautiful sunny sunday

Post by Sandro Picchio » Fri Jan 24, 2020 8:54 am

Raya,

the book i referred to is another one with similar title. It is:

Dudley Pope
Life in Nelson's Navy
Naval Institute Press

Patrick O'Brian is a novelist - whose books I like to read. Dudley Pope is a historian.

Sandro

Chris B
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Re: beautiful sunny sunday

Post by Chris B » Fri Jan 24, 2020 12:13 pm

Dudley Pope's writing was a mixture of nautical fiction (I'm thinking of his "Ramage" series of novels), and several volumes of historical non-fiction. Pope was also an experienced sailor: he spent a lot of time on seagoing sailing yachts, and during his time in the Royal Navy his ship (I can't remember which one) was torpedoed and sunk.

In contrast to Pope - and despite occasional claims to the contrary - Patrick O'Brian had very little seafaring experience. In my opinion O'Brian's strengths lay in his meticulous research and almost forensic attention to detail, plus the ability to spin a good yarn, and the skill to convey to the reader the atmosphere and ethos of life on board ships in the Georgian Royal Navy.

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