Seelöwe - realistic transport capacity of barges

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LWD
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Post by LWD » 28 Apr 2007 15:30

I think I got the 2 meter free board requirement form a post of Paul's on another board. There are two issues with it.

1) it was stated as a German requirement. They could of course relax it but would they do so before then knew it was safe to do so if it was? That was one reason I wondered when the various test were as the timing looks like it may well have been after the end of September.

2) Is it safe. Here Paul is correct from my rather limited knowledge. Length and breadth as well as their ration to the distance between waves can be more important than free board. I've been on a small fishing boat out in the Pacific where the swells were probably well over 2 meters and we had less than a meter free board but we were small enough that we just rode with them. If you start taking on water or having other problems however the free board becomes critical.

I haven't worked out all the numbers but based on what I did previously 40 tons shouldn't reduce the larger barges to less than 2 meters although the smaller ones might have more of a problem especially if they are carrying an engine, a bunch of concrete, and steel that is not included in the cargo aspect.

One question that I have is there seam to have been quite a few barges rejected for various reasons. Are the barges that people are listing as at the various ports all "acceptable" or are some of the rejects included?

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Post by Paul Lakowski » 28 Apr 2007 19:51

Andreas wrote:
Paul Lakowski wrote:If you down load the Springsharp program and fiddle around with building or comparing ships to performance its clear that ship length and beam as well as draft have as much of a baring on seakeeping as freeboard does. Looking at the scale drawing the barges slope from front to back so their is no one freeboard height.


I am not quite sure where you are going with this. I think that if the 2m freeboard requirement posted by LWD earlier was in fact applied, I would logically assume this requirement to be for minimum freeboard, since that would be consistent with a margin of available freeboard across the length of the ship even in conditions where waves are up to 1.25m high (sea state 3). If the barge then has more freeboard towards the bow and stern, so much the better.

All the best

Andreas


In the sharpspring soft ware the freeboard is averaged out so minimum value is only important in relation to maximum value and a broad average. Also LD of the boat is just as important in determining seakeeping. Look at the freeboard of Schnellboot, if that was the only indicator it should sink in sea state 4 or more and yet we have reports of them riding out 2-3 meter waves in the channel and disappearing between waves [how high is the Schnellboot above the water line. If you do this for just about any boat you'll find that that mark is more of a guideline to expected perfomance not a sink-swim mark.

http://www.dcda.org.uk/1-3coastalform/3detailed.html

Covering coastal erosion it records storm events through out a 4month period . These top out at 2-3m waves.

http://www.channelcoast.org/data_manage ... oy2004.pdf

This paper covers wave records in the channel. Most observations indicate ~ 1m Hs [significan wave height]. Also shows wave periods expected.

http://www.oceanweather.com/data/

Shows current wave height in channel/North sea /Western approaches [when it does works :( ] . As of last night it looked like 1-2 meter significant wave height, currently in the channel.

Heres another site monitoring current wave heights around the UK . Just select the buoy and click to read the particulars.

http://www.bbc.co.uk/weather/coast/buoy ... oy#results

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Post by Andreas » 29 Apr 2007 08:21

Paul

You are comparing short, keeled and heavily powered boats designed for ocean-going work with 50m long non-keeled underpowered or towed barges designed for canal work. I am not sure the comparison is valid.

The question is quite simply where does the 2m requirement come from and how was it implemented?

All the best

Andreas

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Post by Paul Lakowski » 29 Apr 2007 23:06

Andreas wrote:Paul

You are comparing short, keeled and heavily powered boats designed for ocean-going work with 50m long non-keeled underpowered or towed barges designed for canal work. I am not sure the comparison is valid.

The question is quite simply where does the 2m requirement come from and how was it implemented?

All the best

Andreas


The answer is simple too , I'm reporting what Schenk wrote and noting that the freeboard figure is only 'part' of a factor that determines seakeeping capability no matter what the ship/boat design.Its clear there was a hugh range of barges selected from shorter L/D ocean going barges to the much longer L/D river barges. Are people thinking of the longer 30 :1 river barges or the majority of the types utilized which have L/D of 16:1 to 20:1.

Clearly the Germans understood the problem and adapted to meet the limitations. They requisitioned ~ 2319 barges of which 1/3 were motorised and 1939 were eventually assembled for direct invasion usage. The rest were selected to warehouse supplies for more rapid loading of supplies as the invasion progressed. Of the 1939 about 300 were set aside as reserves and 1522 assembled by 24th September for planned invasion.Of these barges about 1/2 were to expected to make one trip across the channel and then be employed on either side of the channel to speed up loading and unloading onto open beaches.

Its not clear from the results just how much effect RAF and RN attacks in the weeks of Sept had , they may have delayed some barges from arriving.Schenk confirms 51 barges put out of commision temporarly or perminantly and 163 damaged, but the lasting influence doesn't look like much . The air attacks occured through Sept 15-21st and the barge numbers go from 564 on 14th sept to 885 on the 19th and 1522 on the 24th.

The bulk of all troops supplies and equipment for the invasion were expected to cross the channel in medium sized freighters with barges mostly being employed to load and unload these transports at either end.

Also when people speak of 'sea state' they need to be clear on what that means.

http://www.ecan.govt.nz/Our+Environment ... height.htm

What this shows is that the maximum wave experienced could very well be twice the reported significant wave height, which in turn represents the upper 1/3 of the top recorded waves over a period of time. In other words the average expected wave experienced is going to be a fraction of the maximum height wave recorded and the heavier waves in that range will be few and far between.

But this also means that the barges selected, could be expected to survive waves much much larger than a couple of feet. Its likely that after that first wave most follow on barges employed would be powered barges with better seakeeping qualities.

We should note the performance of Barges during DDay it shows ~ 30% loss of barges over a period of 6 months to all causes.

http://www.naval-history.net/WW2MiscRNLandingBarges.htm

Background Loss and Other Notes:
1. For the passage to Normandy, June 1944, some barges were towed over, most sailed under their own power, some broke down and were towed the rest of way. Barges were seen drifting and in some cases abandoned. The main problem was engine failure due to shipping water, but also loss of rudder (WB).

2. On the passage over, west to north-westerly winds were Force 5 to 4, waves up to 6ft. Barges were wallowing/rolling and shipping water. Some were swamped and sank, including one unidentified LBV south from the Isle of Wight. Only one barge heading for Utah was lost in the rough seas. In summary, what were "London river barges (doing) crossing the English Channel in that weather?" (BS.39/WB)

3. On arrival off Normandy, the LBO’s, LBW’s, LBK’s, LBE’s anchored off the beaches or beached, and were soon in business fuelling, watering, feeding and repairing, often under heavy fire; the LBV’s landed their cargoes and commenced the ship-to-shore ferry duties they normally engaged in as civilian river lighters (WB).

4. The June 1944 gales developed in outline as follows – Friday 16th, weather started to deteriorate; Saturday 17th, northerly winds force 4; Sunday 18th, wind strengthening; Monday 19th by midday, north-easterly force 7 and up to gale force 8 for three days and nights; Thursday 22nd, wind began to moderate. With the winds from the NE, no part of the Normandy beachhead was sheltered, but the US sectors suffered most because the Mulberry Harbour was incomplete. One unidentified LBE sank off Utah beach in the gales and the crew rescued by a US LCA (BS.39/WB).

5. By D+30, landing barge losses (damaged sufficiently to require assistance) were 8 LBV’s (48 damaged), 9 LBO’s (20), no LBW’s (4), 5 LBE’s (16) (BS.39)

6. At the end of August, LBE.5 and an unidentified LBO & LBV or W were in tow by a Dutch tug back to England in a gale. The LBO & LBV or W tows broke, and one sank with the loss off two men (WB)
.
7. In late October 1944, the 37th LB (S&R) Flotilla was in a south of England port, possibly Langstone, preparing to sail for Belgian/Holland. Many of the LBW’s and LBO’s were in a "shocking condition" and some were immediately written off (WB)

8. By the end of 1944, landing barge losses since January totalled approximately 58 from all causes – around 35 LBV’s, 10 LBO’s, 4 LBW’s, 7 LBE, 3 LBR (ramped) (HMSO).



PS: Looking at the barge scale drawing in Schenk, the barge hull heights were 3.4-2.5-3.5 meters [stern-wheel house- bow] for the Type A1 barges and 3m -2.6- 4.8m [stern-wheelhouse-bow] for the Type A2 barges. They were supposed to ride at 0.8 meter draft in the bow to meet the landing barge requirement, suggesting the bow freeboard was 2.8m and 4m, respectively. This dipped to 1.8-1.9m respectively around the wheel house. The average freeboard @ this draft works out to about ~ 2.3m & 2.5m, which incidently is close to the Schnellboot @ 2.3m average free board for the early Schnellboot and 2.56m for the war years designs.

The prewar Schnellboot design has L/D of ~ 13:1 , while the war designs are ~ 11:1...but its sea worthyness of these boats was poor at high speed. In seas of 3-4 meters the top speed would have to be reduced to about 20-25knts. Their lack of employment in those waters has more to do with being unable to fill doctrine. As I recall the Schnellboot in this period conducted mining operations through out September anyway.

Andreas
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Post by Andreas » 30 Apr 2007 08:45

Paul Lakowski wrote: Also when people speak of 'sea state' they need to be clear on what that means.

http://www.ecan.govt.nz/Our+Environment ... height.htm

What this shows is that the maximum wave experienced could very well be twice the reported significant wave height, which in turn represents the upper 1/3 of the top recorded waves over a period of time. In other words the average expected wave experienced is going to be a fraction of the maximum height wave recorded and the heavier waves in that range will be few and far between.


Err, Paul - Sea State is a fixed expression, and it is very clear what it means, and has meant since 1939 when it was officially recognised by the IMO. It was developed by a German Captain in 1927.

http://de.wikipedia.org/wiki/Seegang

http://en.wikipedia.org/wiki/Sea_state

0 Calm (glassy) 0 m
1 Calm (rippled) 0 - 0.1 m
2 Smooth (wavelets) 0.1 to 0.5 m
3 Slight 0.5 to 1.25 m
4 Moderate 1.25 to 2.5 m
5 Rough 2.5 to 4 m
6 Very rough 4 to 6 m
7 High 6 to 9 m
8 Very high 9 to 14 m
9 Phenomenal Over 14 m


So this is what I speak of when I use the term Sea State/Seegang, and I am reasonably certain that authors/planners are using the same term in the same way, since it has a universal meaning. If you mean something different, then it is up to you to be clear about it, since you are not using the term in the official way.

All the best

Andreas

John T
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Post by John T » 30 Apr 2007 11:08

Andreas wrote:
Paul Lakowski wrote: Also when people speak of 'sea state' they need to be clear on what that means.

http://www.ecan.govt.nz/Our+Environment ... height.htm

What this shows is that the maximum wave experienced could very well be twice the reported significant wave height, which in turn represents the upper 1/3 of the top recorded waves over a period of time. In other words the average expected wave experienced is going to be a fraction of the maximum height wave recorded and the heavier waves in that range will be few and far between.


Err, Paul - Sea State is a fixed expression, and it is very clear what it means, and has meant since 1939 when it was officially recognised by the IMO. It was developed by a German Captain in 1927.


Andreas,
Sea State is a fixed expression of what?
Answer: Significant Wave Height in meters.
- exactly what Paul says.


http://www.dstan.mod.uk/data/00/970/07030200.pdf Page 7:
Notes:
1 The Significant Wave height (SWH) is defined as the average value of the
height (vertical distance between trough and crest) of the largest one third
(1/3) of waves present.

2 The Maximum Wave Height (MWH) is usually taken as 1.6 x Significant
Wave Height e.g., SWH of 6 metres gives MWH of 9.6 metres.


Once again you express yourself in a way that your opponent's wrong,
when the the discussion just reached a level of detail where your sources do not have exact enough definitions.


We all learn
/John T
(Ex. Conscript Meteorological office, Royal Swedish Navy, 1. ASW Sqn.)

So I simply had to check up the definition ;)

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Post by Andreas » 30 Apr 2007 11:18

John

Where do I say that Paul is wrong please? I just don't understand why he asks posters to clarify what they mean by 'sea state' when there is only one thing that can be meant, reasonably. Your link does however show that he maybe wrong in saying that MWH could be 2x SWH, since your link states expected MWH would be 1.6x SWH.

BTW: 1.25 x 1.6 = 2 - probably co-incidence.

All the best

Andreas

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Post by John T » 30 Apr 2007 11:38

Andreas wrote:John

Where do I say that Paul is wrong please?
Andreas

Just look at the quote of you in my post. As far as I know Err is a short form of error.
Andreas wrote:Err, Paul - Sea State is a fixed expression, ...


-----------------------------------------

Andreas wrote:
Your link does however show that he maybe wrong in saying that MWH could be 2x SWH, since your link states expected MWH would be 1.6x SWH.



1.6 is rounded to 2 as an aproximate value of another aproximate value.

Are we talking right or wrong in a contest of rethorics
or try to describe a physical reality as mathematical models?

Cheers
/John T.

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Post by Andreas » 30 Apr 2007 11:52

John T wrote:
Andreas wrote:John

Where do I say that Paul is wrong please?
Andreas

Just look at the quote of you in my post. As far as I know Err is a short form of error.
Andreas wrote:Err, Paul - Sea State is a fixed expression, ...


First time I hear that. For me it is a written expression of confusion.

-----------------------------------------

John T wrote:
Andreas wrote:
Your link does however show that he maybe wrong in saying that MWH could be 2x SWH, since your link states expected MWH would be 1.6x SWH.



1.6 is rounded to 2 as an aproximate value of another aproximate value.

Are we talking right or wrong in a contest of rethorics
or try to describe a physical reality as mathematical models?

Cheers
/John T.


Replace 'wrong' by 'imprecise', if you so wish.

All the best

Andreas

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Post by fredleander » 30 Apr 2007 12:08

LWD wrote:I haven't worked out all the numbers but based on what I did previously 40 tons shouldn't reduce the larger barges to less than 2 meters although the smaller ones might have more of a problem especially if they are carrying an engine, a bunch of concrete, and steel that is not included in the cargo aspect.

As I have opinioned before - space, rather than weight, would be the limiting factors in the barges. Just think about it: These vessels were originally built to run with their load compartments full of coal, sand, wheat, whatever. With no air in-between. Any military load, except solid stacks of ammunition boxes, would necessary contain more air than mass. For example, some 300-ton barges were planned to carry 3 25-tonn tanks. A "personell" barge with 150 troops might add up to 20 tonn, personal equipment included. Most of the examples I have seen describes a mixed load - personell and vehicles. Should give plenty weight availability for all the constructional weight additions.

LWD wrote:One question that I have is there seam to have been quite a few barges rejected for various reasons. Are the barges that people are listing as at the various ports all "acceptable" or are some of the rejects included?

Schenk writes a lot about this. There were several control board stations which made final acceptance trials (inspections). As I read him many were rejected but also some of the originally rejected were "taken in" again. It should be understood that the wharfs modifying the barges were able to do it all so I should think a lot of improvements were made. For example, he also mentions that quite a few barges were shortened to improve their strength. So, the variation in type/sizes might have been much larger than simple "A" and "B" categorization..... :)

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Post by fredleander » 30 Apr 2007 12:20

Paul Lakowski wrote:[Clearly the Germans understood the problem and adapted to meet the limitations. They requisitioned ~ 2319 barges of which 1/3 were motorised and 1939 were eventually assembled for direct invasion usage. The rest were selected to warehouse supplies for more rapid loading of supplies as the invasion progressed. Of the 1939 about 300 were set aside as reserves and 1522 assembled by 24th September for planned invasion.Of these barges about 1/2 were to expected to make one trip across the channel and then be employed on either side of the channel to speed up loading and unloading onto open beaches.

I read Schenk a little differently. He states 2319 "modified" barges. Very close to that he states "2400". I believe what was requisitioned (Klee) - or eventually gathered - was approx. 3000. Klee's detail charts of the invasion fleet count the use of approx. 1100 barges on S-day.

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Post by John T » 30 Apr 2007 14:04

Andreas wrote:
First time I hear that. For me it is a written expression of confusion.


Uhu, since you wrote it you know the best, then I learned something again.
Too much computer errors in my mind.

To push this discussion further would undoubtedly be to err. :)

Cheers
/John T.

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Post by Paul Lakowski » 30 Apr 2007 18:56

Andreas wrote:
Paul Lakowski wrote: Also when people speak of 'sea state' they need to be clear on what that means.

http://www.ecan.govt.nz/Our+Environment ... height.htm

What this shows is that the maximum wave experienced could very well be twice the reported significant wave height, which in turn represents the upper 1/3 of the top recorded waves over a period of time. In other words the average expected wave experienced is going to be a fraction of the maximum height wave recorded and the heavier waves in that range will be few and far between.


Err, Paul - Sea State is a fixed expression, and it is very clear what it means, and has meant since 1939 when it was officially recognised by the IMO. It was developed by a German Captain in 1927.



Andreas

There are atleast 3 different systems of measureing. I'm given to understand from my american colleges that they use Beaufort scale not sea state. Some people read sea state 2 to mean a ship can't exceed the indicated value of 1.4 feet without sinking. This is clearly not the case.

http://www.oceandata.com/support/Sea%20 ... 0Table.htm

http://en.wikipedia.org/wiki/Beaufort_scale

Apparently UK uses the Beaufort scale for some time. When most people state weather they don't specifiy 'sea state' or 'beaufort scale' or "Pierson - Moskowitz scale". As you can see by comparing scales this can lead to considerable confusion. Schenk specifies the barges shipped little water in force 4-5 winds. Looking at "Pierson - Moskowitz scale" leads us to conclude 11-21knt winds [beaufort scale 4-5] which translates into sea state 2.5 to 5.0 [waves 2.5 ft to 8 ft], a consideable range to choose from don't you think?

If we take sea state 5 as the upper levels then how do they also survive gale force winds of force 6-8 beaufort scale. Thats 22-40knt winds and through "Pierson - Moskowitz scale", sea state 5-7 or significant wave heights of 9-30 feet.

Just because you are clear on what you mean doesn't mean every one is singing from the same sheet of music. If cox states that sea state 3 is the maximum waves that all barges could tollerate , thats 15knt winds and significant wave heights of 4 feet. Going on the calculation that means the maximum wave they could tollerate was ~ 6 feet wave. I included the NZ example to show that sometimes the max wave height can be double [Never forget that calculations are very fallable human attempts to simplify the presentation of data ] . But quite clearly the Barges tolerated alot higher waves than that.I would suggest Cox is wrong or is thinking of a different type of barge.


Since there was a hugh varity of barges , some more suitable than others, it complicates when people speak in universals. Clearly some barges were more ocean going and could make the channel crossing in most weather and some were more river going and were risky any channel weather. I would suggest given the allied use of Barges on DDay that the weather seaworthy ness of the barges is a moot point since they were subjected to such ranges of weather as in Sept 1940 and few were lost to weather over a large period of time. I certainly would not have based my 'national security' on such an assumption.

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Post by Paul Lakowski » 30 Apr 2007 19:02

leandros wrote:
Paul Lakowski wrote:[Clearly the Germans understood the problem and adapted to meet the limitations. They requisitioned ~ 2319 barges of which 1/3 were motorised and 1939 were eventually assembled for direct invasion usage. The rest were selected to warehouse supplies for more rapid loading of supplies as the invasion progressed. Of the 1939 about 300 were set aside as reserves and 1522 assembled by 24th September for planned invasion.Of these barges about 1/2 were to expected to make one trip across the channel and then be employed on either side of the channel to speed up loading and unloading onto open beaches.

I read Schenk a little differently. He states 2319 "modified" barges. Very close to that he states "2400". I believe what was requisitioned (Klee) - or eventually gathered - was approx. 3000. Klee's detail charts of the invasion fleet count the use of approx. 1100 barges on S-day.


Can you tell me of this source 'Klee"? This might explain something else Schenk writes. pp 171 on Logistics of 'Operation Sealion'.

" It was not know until August that there were about 4000 ships to be supplied in addition to the approximately 320 Navy ships."

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Post by Andreas » 30 Apr 2007 20:50

Paul

I think you are getting too focused on survivability. I do not think that a given max. sea state for barge operations equals sinking at higher levels. I think operability is more of an issue. An example based on randomly picked numbers - a barge may well survive sea state 5. But it's crew may not be able to do more in those conditions than weather it, hope for the best, and pray. IOW, what is questioned is the ability to have the barges move across the channel as part of an organised transport attempt working to a strict schedule, once sea state X is exceeded. They may still swim once that happens, but they maybe at significant risk of breaking tow, not able to move in the required direction, etc.pp

All the best

Andreas

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