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Army mortars v screw galleys

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Re: Army mortars v screw galleys
Post by Jonathan_S   » Thu Dec 03, 2015 12:39 pm

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Darman wrote:
Theemile wrote:Sadly, this has me thinking about a hedgehog launcher - a WWII weapon which was essentially a few dozen mortars mounted together to create a pattern of destruction wherever they are aimed - the shipborne issues would be compounded - except for the accuracy bit, since a hedge hog is an aim-over-there-ish weapon.


This was my thought too. A hedgehog or katyusha-type weapon (although I would not want to be the one firing rockets from aboard any wooden ship) firing shells/warheads with incendiary "shrapnel" might be effective.

Keep in mind that the US Army, when considering coastal defense requirements at the end of the 19th century, considered the smallest number of coastal defense mortars (12" mortars, pre-sighted, fixed fortified positions, fixed aiming points, invulnerable to all incoming fire except mortar fire) to be 4 mortars in a diamond formation. And even that was half a battery. Most coast defense installations built at the time included at a minimum 16 mortars per position to bracket the enemy warship with as many shells as possible. This should give you some idea of the challenges of aiming these mortars from dry land. Add in a ship pitching and yawing every which way? No way. Not with the minimal number of mortars you'd be able to fit on a galleon (i.e. one or two at most). Again, the Army's Coast Defense Artillery expected 16 mortars firing at once from fixed positions at pre-sighted coordinates to be effective at taking out an enemy battleship.

Given the difficulty of a direct hit, and the relative ineffectiveness of blackpowder propelled shrapnel from a mortar shell I wonder if you'd be better off trying for something closer to the original hedgehog; underwater explosions using high-explosive. Of course the fuses would have to be changed since the hedgehog was contact fused; it only detonated if it hit a sub. You'd want something that went off at roughly 7-10 feet underwater. But screw gallies have very lightly build hulls; a series "nearby" high explosive underwater detonation might cause significant leaking.

OTOH that requires more resources and time than simply diverting some existing army mortars and ammo onto ships - you'd have to design and build a new mount and ammo. By that point The Cities or KHs should have already shown up - and they've guns that'll blow right through the bow armor on a screw galley. (Not to mention when working in pairs either design has the steam powered mobility split up so a screw galley can't keep it armor pointed at both simultaneously; giving a free shot at the galley's unarmored flank).
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Re: Army mortars v screw galleys
Post by JeffEngel   » Thu Dec 03, 2015 12:51 pm

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Jonathan_S wrote:Given the difficulty of a direct hit, and the relative ineffectiveness of blackpowder propelled shrapnel from a mortar shell I wonder if you'd be better off trying for something closer to the original hedgehog; underwater explosions using high-explosive. Of course the fuses would have to be changed since the hedgehog was contact fused; it only detonated if it hit a sub. You'd want something that went off at roughly 7-10 feet underwater. But screw gallies have very lightly build hulls; a series "nearby" high explosive underwater detonation might cause significant leaking.

OTOH that requires more resources and time than simply diverting some existing army mortars and ammo onto ships - you'd have to design and build a new mount and ammo. By that point The Cities or KHs should have already shown up - and they've guns that'll blow right through the bow armor on a screw galley. (Not to mention when working in pairs either design has the steam powered mobility split up so a screw galley can't keep it armor pointed at both simultaneously; giving a free shot at the galley's unarmored flank).

Still - submarines are going to be a wicked threat to surface vessels, and any nation seeking an equalizer against a large sea power is going to hanker after them as soon as it can build a remotely effective one. Having an anti-submarine weapon prepared already is a fine idea, and putting it to preliminary use against something else is a fine place to start. With different ammunition types - timed fuse, contact fuse, or in this case depth fuse - you'd have something that could suit a variety of niche applications. If it's not sucking up a whole lot of tonnage, space, or manpower, it'd be a handy extra for a warship. And if they're built small enough and with mounts that can be moved from the ship to a field carriage without gross trouble, they could swing from ship use to marine shore use as need be.
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Re: Army mortars v screw galleys
Post by Silverwall   » Thu Dec 03, 2015 4:14 pm

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JeffEngel wrote:
Jonathan_S wrote:Given the difficulty of a direct hit, and the relative ineffectiveness of blackpowder propelled shrapnel from a mortar shell I wonder if you'd be better off trying for something closer to the original hedgehog; underwater explosions using high-explosive. Of course the fuses would have to be changed since the hedgehog was contact fused; it only detonated if it hit a sub. You'd want something that went off at roughly 7-10 feet underwater. But screw gallies have very lightly build hulls; a series "nearby" high explosive underwater detonation might cause significant leaking.

OTOH that requires more resources and time than simply diverting some existing army mortars and ammo onto ships - you'd have to design and build a new mount and ammo. By that point The Cities or KHs should have already shown up - and they've guns that'll blow right through the bow armor on a screw galley. (Not to mention when working in pairs either design has the steam powered mobility split up so a screw galley can't keep it armor pointed at both simultaneously; giving a free shot at the galley's unarmored flank).

Still - submarines are going to be a wicked threat to surface vessels, and any nation seeking an equalizer against a large sea power is going to hanker after them as soon as it can build a remotely effective one. Having an anti-submarine weapon prepared already is a fine idea, and putting it to preliminary use against something else is a fine place to start. With different ammunition types - timed fuse, contact fuse, or in this case depth fuse - you'd have something that could suit a variety of niche applications. If it's not sucking up a whole lot of tonnage, space, or manpower, it'd be a handy extra for a warship. And if they're built small enough and with mounts that can be moved from the ship to a field carriage without gross trouble, they could swing from ship use to marine shore use as need be.


Subs are no threat to anyone until the orbital bombardment system is taken out of play. Subs MUST use electricity to be viable so by the time they are doable the proscriptions and the OBS must have been smashed to pieces.
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Re: Army mortars v screw galleys
Post by lyonheart   » Thu Dec 03, 2015 5:26 pm

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Hi TheEmile,

I think you mean Congreve rockets since the Hale wasn't invented until 1844 and used by the US in the Mexican war.

A hedgehog or multi-barrel type weapon makes far more sense than a single mortar, since the odds of hitting for any single shell are probably in the 1-2% range if that.

Impact fuses are the only way to go at present, although a shallow water hydro static fuse for near misses might be tried, and volleys of 9-12 4.5" mortar shells ought to do serious damage to both the screw galley's top and crank decks besides having a very high rate of fire.

Since the explanations of why direct fire guns were used instead of mortars are quite correct, a faster firing gun such as the 3" revolver I suggested might work although even a 3-4" breech loader with a rate of 20-25 rpm would probably work better.

L


Theemile wrote:
JeffEngel wrote:*quote="Theemile"*

Sadly, this has me thinking about a hedgehog launcher - a WWII weapon which was essentially a few dozen mortars mounted together to create a pattern of destruction wherever they are aimed - the shipborne issues would be compounded - except for the accuracy bit, since a hedge hog is an aim-over-there-ish weapon.*/quote*
The hedgehog was used for depth charge distribution against a submarine that wasn't localized beyond over-there-ish - you got "accuracy" under those conditions just by hosing down an area with pain. Surface fighting wouldn't have that kind of need except in case of fighting in the dark or thick fog, but the sub could be put out of action or driven off by underwater detonations that may not do much good against a ship when they go off in air.

If the idea is just to rip up sails and rigging, you're in better shape. That said, I've got no idea how bad sheer concussion is on sails or rigging, or how well these charges are going to spread jagged bits of metal to rip them up.

If you don't mind ripping through ammo and you do want to get things done in a hurry, you could use something hedgehog-like - a cluster of mortars firing shells in a narrow fan. While the army can do very good things with mortar accuracy and well-timed fuses for air burst, a ship has to worry about the sea under it pitching it in ways that the army only needs to fear if it takes to fighting during earthquakes.

But in the spirit of varying the exercise some, rockets with timed fuses for air bursts may be another source of indirect fire. I don't think I'd care to try them on any ships with any sails or rigging though.


The British used the Hale rockets on their bombardment ships in the war of 1812 (and Napoleonic wars), and those ships were rigged. I think one of the previous posters was correct, you'd probably need a ship with the appropriate (Ketch) type sail plan for either ordinance type, but I believe the Hale's were used widely in the British fleet for a number of years on most vessels.
Last edited by lyonheart on Fri Dec 04, 2015 2:30 am, edited 1 time in total.
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Re: Army mortars v screw galleys
Post by n7axw   » Thu Dec 03, 2015 7:50 pm

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Nice post, Silverwall. Like Keith said, it sort of takes the wind out of my sails. But, oh well, I guess I can still blow hot air.. :lol: On a more serious note, let's see if we can flesh out the discussion just a bit more.

Silverwall wrote:
Accuracy of mortars from ships is historically known to be complete shit. Read about the bombardment of the forts protecting New Orleans during the civil war. Firing on a massive immobile target from a moored flat bottomed craft specifically designed as a mortar platform they missed something like 75% of the shots. The complexities of dropping trajectories is massively more complex than you assume, literally a single degree of roll can cause you to miss your target by several hundred feet.


I take your point. However, against the screw galleys, the battle will be mostly in sheltered waters such as inlets and coastal waters, or perhaps, enclosed bays like in HFQ. That would make a bit of a difference for the aiming, I would think. But even so, your point is well taken.

Silverwall wrote:
The other issue is that for accurate mortar fire you need very consistently burning and consistently sized propellant charges, something that is not really doable with black powder.


Brown powder is already available for the ICN and smokeless powder will be available shortly. This is just an extraneous thought, but could mortar shells be designed as effectively as shells for angle guns?

Silverwall wrote:
As for your idea of using shrapnel from above on crew it will work once maybe and then just putting some light 1" or less timbers or plyboard above the heads of the gun crews will negate all effectiveness as shrapnel from a mortar will only be falling at terminal velocity + a small amount from the bursting charge. A lot of what made Napoleonic shrapnel powerful was the horizontal velocity of being fired from a long barreled cannon.


How effective your plywood would be would be dependent upon the powder, I would think, or the size of the shell you were able to use the pound the plywood with. But still, after that is said, virtually everything has a counter so one could also shelter with iron or steel, except in the case of the screw galleys they are probably not going to be able to handle a lot more weight than they already have.

Silverwall wrote:
Finally with all due respect shredding the sails is not actually that important in a sea fight, The real aim is to cut the rigging that controls them and or the masts/spars so the sails loose all power.

cutting one halyard or stay has the same effect as punching hundreds of holes into the body of the sail. Also with the projectiles coming almost straight down there will be very few sail hits as the sails are oriented parallel with the direction of travel. Again you would get better results with shrapnel fired horizontally from a long gun perpendicular to the sail.


OK, I get the point. The bursting charge would have to be either to the front or the rear of the galley to have the horizontal impact you are talking about. There would be some, but not to the extent of a directly driven shell. Again, the kind of powder used in the shell would be important to how effective this could be.

So what this ends up amounting to is that my original idea is impractical as proposed. But perhaps there could be some modification of it that would work.

Don

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Re: Army mortars v screw galleys
Post by Silverwall   » Thu Dec 03, 2015 8:40 pm

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Don

In the New Orleans case they were moored in a river/bayou with no waves to speak of, I guarantee you shooting at a galley in a bay/harbour will have more swell to deal with.

Terminal velocity of the shrapnel even with the explosion would be unlikely to be more than 175 mph max or ~255 feet per second. The bursting charge in a shrapnel round is very small, just enough to shatter the outer casing and disperse the shrapnel balls. Do not confuse it with the powerful explosion of a HE round being fused for proximity detonation.

For comparison the 45 ACP round which is famously slow by bullet standards is ~820 fps which is a huge difference in energy and will almost certainly suffer less drag than shrapnel will. 9mm parabellum has a muzzle velocity of about 1250 fps and rifle rounds only go up from there. I therefore stand by my comment that a thin splinter deck of wood will protect against this kind of splinter damage. The lack of velocity of splinter/shrapnel damage is why a 2-3mm thick steel helmet could protect soldiers in the world wars when direct shots went straight through.

Angle guns are long barrel compared to mortars so have much more burn time to fully consume the propellant charge and reach a consistent velocity.

As I said the correct way to fire shrapnel into the rigging is to use a conventional long cannon to fire case shot straight at the rigging. Much easier to aim, more effective and doubles for other purposes.
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Re: Army mortars v screw galleys
Post by n7axw   » Thu Dec 03, 2015 10:32 pm

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Silverwall wrote:Don

In the New Orleans case they were moored in a river/bayou with no waves to speak of, I guarantee you shooting at a galley in a bay/harbour will have more swell to deal with.

Terminal velocity of the shrapnel even with the explosion would be unlikely to be more than 175 mph max or ~255 feet per second. The bursting charge in a shrapnel round is very small, just enough to shatter the outer casing and disperse the shrapnel balls. Do not confuse it with the powerful explosion of a HE round being fused for proximity detonation.

For comparison the 45 ACP round which is famously slow by bullet standards is ~820 fps which is a huge difference in energy and will almost certainly suffer less drag than shrapnel will. 9mm parabellum has a muzzle velocity of about 1250 fps and rifle rounds only go up from there. I therefore stand by my comment that a thin splinter deck of wood will protect against this kind of splinter damage. The lack of velocity of splinter/shrapnel damage is why a 2-3mm thick steel helmet could protect soldiers in the world wars when direct shots went straight through.

Angle guns are long barrel compared to mortars so have much more burn time to fully consume the propellant charge and reach a consistent velocity.

As I said the correct way to fire shrapnel into the rigging is to use a conventional long cannon to fire case shot straight at the rigging. Much easier to aim, more effective and doubles for other purposes.


Ok. Just for my edification, comment on the idea that the brown and smokeless powders could make the mortars more effective.

Don
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Re: Army mortars v screw galleys
Post by Silverwall   » Thu Dec 03, 2015 11:00 pm

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Having just googled the properties of brown powder I see it is slower burning. This is good in long guns but actually counter-productive in a mortar which has a very short barrel relative to it's caliber. It would however be much more reliable in terms of burn rate (when not wet, oops ships are very damp) this is much less of an issue in conventional naval artillery which until the dreadnought era was fired in non parabolic direct trajectories. Also by the time it was introduced in the 1870's most naval guns were either breach-loading or were muzzle loaded from special loading depressions where the charge and round were greatly protected from the elements. Obviously mortar rounds being dropped in from the muzzle are very susceptible to the environment.

*Edit* It should also be mentioned that a grain size greater than 1 inch across also leaves quite a bit to be desired in a mortar that is only ~3 inch in callibre

Smokeless is obviously the best but from a EoC point of view getting smokeless into the army's rifles is obviously much more important tactically and strategically than improving an experimental weapons system for the navy
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Re: Army mortars v screw galleys
Post by Hooked   » Fri Dec 04, 2015 4:41 am

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The Go4 has come up with something Russian katyusha rockets from WWII.
Chairis is going to produce a better version using Lewsite(sp?) (like dynamite)
Is it possible to have a multiple rocket launcher on a ship. Enough explosions, even just close to a screw may be enough to damage its hull? It may not be necessary to hit the screw galley. Just like horseshoes, close enough is all you need.
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Re: Army mortars v screw galleys
Post by Silverwall   » Fri Dec 04, 2015 4:49 am

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Hooked wrote:The Go4 has come up with something Russian katyusha rockets from WWII.
Chairis is going to produce a better version using Lewsite(sp?) (like dynamite)
Is it possible to have a multiple rocket launcher on a ship. Enough explosions, even just close to a screw may be enough to damage its hull? It may not be necessary to hit the screw galley. Just like horseshoes, close enough is all you need.


Mount the Katyusha's to fire over the front of a galley and they could be practical harbour defence weapons. Probably won't do much to a true ironclad but the open topped ships and older galleons would be in trouble.
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