Sealion Naval Forces Mk II

Ian Hathaway

In the interests of users sanity this thread has been started to get back to the original point of the discussion ...

Ian Hathaway said:
Following on from this, a simplistic analysis of the "Battle of the Channel" would give us an idea of the losses sustained by both sides and of what forces the Germans could land on British soil.

I have looked at the relative strengths of each ship/boat involved based on a very simple formula of firepower alone taking into consideration the weight of shot, range and rate of fire of the weaponry of the vessels of both sides. This gives the following results as a comparison to the British Tribal Class Destroyer:

  • German Destroyers are 13% stronger than the Tribal Class. Their guns (12.7cm as opposed to the 4.7" QF of the Tribal) fire a heavier projectile over a greater distance and at a quicker rate.
  • In comparison a British Light Cruiser is typically 3 times better than a Tribal.
  • The Battleship HMS Revenge has the Equivolent firepower of 15+ Tribals.
  • In contrast the British V & W destroyers (the most numerous) are only rated at 1/3 the strength of the Tribal.
  • On the German side the 1935 Class Torpedo Boat is slightly weaker than the V & W destroyer however the Raubtier Class Torpedo Boats which also carry the 12.7cm gun are twice as good as the V & W.
  • It would take 11 or 12 ASW Trawlers to pack the same punch as a Tribal.
I know that is pretty basic but it will hopefully give a good idea of what might happen.

The following assumptions have been made, but these assumptions can be changed and the analysis run again:

  • The British have received copies of the plans showing landing beaches and convoy routes, but not dates and times. The plans were only confirmed as genuine at the last minute however so the RN was not able to redeploy shipping but does know where to target their attacks. Basically their is no delay due to fog of war or uncertainty of the exact location of the invasion area.
  • The British identify the German buildup and place all units on alert to sail at 30 minutes notice. This again means that there are no delays in interception.
  • Due to the above the British use their network of Dutch, Belgian and French informants to tell them of the exact moment of departure of the invasion convoys and can set sail and intercept as quickly as possible.
  • On receipt of orders all ships and small boats depart from their respective locations from Plymouth, along the South Coast and up the East Coast as far as Rosyth (all other locations are out of range). To avoid overstressing the ships all sail at 75% max speed. No breakdowns or collisions occur.
  • Mines can be ignored as the British know where they are going and they have been constantly keeping cleared lanes.
  • The German convoys begin moving at 22:00 on 23rd September utilising the darkness to best advantage. The convoys finish forming up off the English coast at 08:00 on the 24th and begin their run to the beaches at this time. The first troops land at 09:00 and continue until all are landed or the remaining transports/barges are sunk.
  • Half light is between 06:00 and 7:00 with full light at 07:00 onwards.
  • From first sailing to the German ships returning to port takes 16 hours (the slower barges are abandoned on the beaches to be recovered at a later date.)
  • No air attacks have been taken into account. It is assumed that the Luftwaffe either fails to break through the fighter screen or is occupied elsewhere. The same applies to the RAF.
  • As per Admiralty orders the RN is tasked with targetting the transports and only engaging with war ships if directly threatened. As such 80% of damage has been allocated to the German transports and 20% to German warships.
  • To try to balance the argument that the German sailors were not as good as those of the RN and that their ships were poorly designed the rating of their ships has been reduced by 1/2 in all calculations.
I will post the results shortly ...
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Ian Hathaway

Derek Pullem said:
Also the straight comparison of combat power might be a bit misleading.

Destroyer vs Destroyer probably leads to two wrecked ships with both combat ineffective.

But destroyer vs barge / auxillary leads to multiple casualties on the barge / auxillary side.

You might be better off "pairing off" the naval combatants, destroyer for destroyer, and then estimating barge kills per warship therafter.

The problem is that as many of the barges were towed then one kill may render many barges ineffective

Revenge and Erebus landing 15" shells anywhere near the barges is going to create secondary losses from collisions and such like.
Click to expand...

Okay I think I've addressed this... damage it split 80%-20% between transports and fighting ships. So damage is done in those ratios ... from first glance it results in the loss of some 700 transports. I've lumped all transports together however so that includes barges, tugs, freighters, ferries etc. etc.
 

Ian Hathaway

sharlin said:
Not to mention the effect of a 15 inch shells near miss producing splinters when they burst on impact. A near miss would probably still be fatal as the hull would have metal spears go hurtling through the sides...even a 4.7 shell would do this :s

Raw numbers won't tell the real result. One thing I do suggest Ian is that for any auxillery craft, armed barges etc you reduce their combat capabilities by 3/4 simply because they are not built for it, not directed, not trained etc. The German naval ships would still be at a disadvantage, they simply are not as experienced at this as the RN are and they are tied to the Convoy.
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Believe me when I tell you that this has already been done, if I use the comparison to a Tribal Class again it would take over 3000 barges to have the equivolent strength of just a single Tribal.
 

sharlin

Banned
Ahh good :) It still needed to be said and its good to see you're not doing what Glenn does "I deny reality and replace it with my own."
 

Ian Hathaway

sharlin said:
Ahh good :) It still needed to be said and its good to see you're not doing what Glenn does "I deny reality and replace it with my own."
Click to expand...
I'm also willing to change any parameters people think are unrealistic or go the whole hog and go ASB and give the Germans every advantage just to see what would happen if people want it.
 

Some Bloke

Even with these back of the envelope calculations regarding relative strength, it's abundantly clear the invading force takes a pasting even before landing with relatively little loss to the RN.

Britain scores a huge PR coup with the US.

If we assume Paratrooper deployment, losses rule out an assault on Crete at the very least. Large material losses for the Germans, less forces allocated to Greece to begin with? More troops to North Africa with the invasion threat eliminated. More attention to Landing Craft development?

The real question here is, what makes the Germans try to invade in the first place? A failed/diminished evacuation of Dunkirk?
The British do something that pissed Hitler off?
 

cpip

Ian Hathaway said:
I'm also willing to change any parameters people think are unrealistic or go the whole hog and go ASB and give the Germans every advantage just to see what would happen if people want it.
Click to expand...

I'd be interested to see the "most ridiculously best-case" scenario, myself -- for both sides.

While I admit the limits and constraints of a mathematical model, I have found this entire process interesting, since so rarely do we do AH through modeling.
 

sharlin

Banned
1940's UK coastal arty was nothing to really write home about, the coastal defences were mostly old 6 inch guns from WW1 cruisers, some 4.7's from WW1 destroyers and lighter weapons, yes you've got Winnie and Pooh but they are not really that useful at this point in the war due to lack of radar.

The British guns would only be useful against anything on the final 'sprint' towards the beaches, it would not factor into the naval battle.

Then again neither would the German guns, they never hit anything outside of the UK and Dover and again should not be factored into any naval engagement as a vast majority of them are either, not in place yet or simply out of range and without a FC radar and decent spotting from the Luftwaffe they are only capable of barraging an area and hoping for a hit.
 
Derek Pullem

Derek Pullem

Donor
Ian Hathaway said:
Okay I think I've addressed this... damage it split 80%-20% between transports and fighting ships. So damage is done in those ratios ... from first glance it results in the loss of some 700 transports. I've lumped all transports together however so that includes barges, tugs, freighters, ferries etc. etc.
Click to expand...

Thats a horrendously high number from first wave - or is it for all waves?

I know you are doing the sums not me but it might be more useful to treat the larger merchant vessels (ferries etc) separately from barges and tugs. I can well imagine a very high loss rate in the barge convoys but the "fast" freighters may get away with a lower one.
 

sharlin

Banned
Ian Hathaway said:
Okay I think I've addressed this... damage it split 80%-20% between transports and fighting ships. So damage is done in those ratios ... from first glance it results in the loss of some 700 transports. I've lumped all transports together however so that includes barges, tugs, freighters, ferries etc. etc.
Click to expand...


700 transports! jesus thats the Invasion a failure there and then no matter what, you've just sank roughly half of the invasion fleet's ships and god knows the damage to the others along with shattered morale for the poor sods having to man them :s

And yes totally agree with Derek, the Barges would suffer far greater losses as they basically are the priority targets and FAR easier to sink than any large vessels.
 
Derek Pullem

Derek Pullem

Donor
Ian Hathaway said:
Just realised also ... I haven't included anything for British coastal artillery yet ... so that needs including.
Click to expand...

sharlin said:
1940's UK coastal arty was nothing to really write home about, the coastal defences were mostly old 6 inch guns from WW1 cruisers, some 4.7's from WW1 destroyers and lighter weapons, yes you've got Winnie and Pooh but they are not really that useful at this point in the war due to lack of radar.

The British guns would only be useful against anything on the final 'sprint' towards the beaches, it would not factor into the naval battle.

Then again neither would the German guns, they never hit anything outside of the UK and Dover and again should not be factored into any naval engagement as a vast majority of them are either, not in place yet or simply out of range and without a FC radar and decent spotting from the Luftwaffe they are only capable of barraging an area and hoping for a hit.
Click to expand...

What Sharlin said - the coastal guns might be useful if the Germans were trying to do a stand off bombardment to support the beaches but their main use would be disrupting (not necessarily sinking) the landing force.
 
Derek Pullem

Derek Pullem

Donor
The Hipper and the Scheer sunk (at least) 7 of 19 and 5 of 37 respectively when they encountered virtually unescorted convoys. These were in open sea and in Sealion terms would be the equivalent of the best transports the Germans had but I think it would not be unreasonable to allow the "excess" warships (say Tribals and larger) to sink or disable as many as 6 larger merchant vessels per sortie providing there were enough smaller warships to keep the escorts busy

The barge casualties will be worse but very difficult to estimate. Some experiences of the German in the Crete operation would suggest that up to 100% casualties are possible. It would depend alot on weather and more important visibility
 

Ian Hathaway

Derek Pullem said:
Thats a horrendously high number from first wave - or is it for all waves?

I know you are doing the sums not me but it might be more useful to treat the larger merchant vessels (ferries etc) separately from barges and tugs. I can well imagine a very high loss rate in the barge convoys but the "fast" freighters may get away with a lower one.
Click to expand...

The number of transports was in excess of 1800 so yes 700 seems high but accounts for just over 1/3 of all transports. The transports included the motor boats, barges, tugs and the larger ships. The problem is that I suspect that due to the large numbers of vessels at sea even the larger, supposedly faster freighters would be pretty restricted in their speed.
 

sharlin

Banned
Well going off the Axis's experiences off Crete when the Italian convoys were intercepted by naval vessels then yeah...thats probably a close analogue of what the Sealion force would be, slow moving and largely defenceless ships with inadequate numbers of escorts simply being swarmed at close range. The Seelowe convoys are simply too large to utterly annihilate and ramming a barge is a bad idea..but you're going to be looking at staggeringly huge losses amongst the barges and tugs.
 

sharlin

Banned
Ian Hathaway said:
The number of transports was in excess of 1800 so yes 700 seems high but accounts for just over 1/3 of all transports. The transports included the motor boats, barges, tugs and the larger ships. The problem is that I suspect that due to the large numbers of vessels at sea even the larger, supposedly faster freighters would be pretty restricted in their speed.
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Aye you'd have to keep them in a convoy, really the best use for the fast 12kt ships would be rushing supplies over after the initial wave gets ashore. Their speed at least cuts down the time but you'd NEED a port to unload them whilst a barge you can just run ashore.
 
Derek Pullem

Derek Pullem

Donor
sharlin said:
Probably putting Pocket Battleships, Twins, the Pre-dreadnoughts, Hipper and cruisers in there, and maybe the Bis?
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Going to be a horrible tactical position for major warships to be tied to a slow convoy faced by dozens of light torpedo armed warships within sight of their resupply bases.

I think the Germans had it right when they looked at these heavy vessels as decoys to draw alot of the Home fleet away from the invasion.
 

sharlin

Banned
But even then the decoy idea is assuming that the RN would send damn near everything it had chasing after them and most of the German ships simply were not ready or undergoing repairs at the time. The forces enough were not enough to draw off the RN in its entirity, unless the Germans assumed the Brits were all at the 'ol classic, the lead paint snorting.
 
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