Seelöwe - realistic transport capacity of barges

Discussions on WW2 in Western Europe & the Atlantic.
Andreas
Member
Posts: 6938
Joined: 10 Nov 2002 14:12
Location: Europe

Seelöwe - realistic transport capacity of barges

Post by Andreas » 19 Apr 2007 09:24

Split from:

http://forum.axishistory.com/viewtopic.php?t=117160
leandros wrote: What matters, in my opinion, is that the Germans found them feasible. Who are we to judge better than those who were to use them..... 8-)
That is an extremely silly argument. The Germans also thought it feasible to destroy the Red Army in a campaign lasting a few weeks, they thought it feasible attack in the Arctic in 1941 towards Murmansk, and they thought it feasible to win the war in the Med without taking Malta, and I could go on and on and on, like the energizer bunny, since there is no shortage of faulty German judgments during the war. I'd say that a lot of these judgments were unbelievably stupid, some with hindsight, and some should have been obvious at the time. OTOH, some of there more audacious judgements were correct, e.g. Weserübung, or Merkur. It is therefore reasonable to debate whether the German judgement on a matter where we have no historical outcome was in fact correct. To try to shut down this debate by saying that the original planners thought it was a good idea is coming close to an acknowledgment that you have no argument left.

As for all this reinforcement of the barges for protection with sand, steel, and whatnot, has a calculation been made of how e.g. infilling of the empty spaces with sand affects buoyancy and thereby load carrying capacity of the barges? It is a straight trade-off. For every kilogram of sand/steel that is used to protect the barge from enemy action, one kilogram of freight has to stay in France. There is no free lunch here.

All the best

Andreas
Last edited by Andreas on 28 Apr 2007 13:31, edited 2 times in total.

John T
Member
Posts: 1183
Joined: 31 Jan 2003 22:38
Location: Stockholm,Sweden

Re: Fighters and Barges

Post by John T » 23 Apr 2007 21:37

Andreas wrote:
As for all this reinforcement of the barges for protection with sand, steel, and whatnot, has a calculation been made of how e.g. infilling of the empty spaces with sand affects buoyancy and thereby load carrying capacity of the barges? It is a straight trade-off. For every kilogram of sand/steel that is used to protect the barge from enemy action, one kilogram of freight has to stay in France. There is no free lunch here.

All the best

Andreas
What where the average capacity of these barges?
bulk loads of 100-400 tons?

What do a infantery company weights?
If you want to use a barge with such a light load you'd like to weight her down with ballast and sand and steel plate is pretty good ballast.

I see two tradeoffs,
Center of gravity to aviod that the barge becomes top heavy,
so you have to load 200 tons on sand low and add 50 tons of steel plate on the top and then fill the space between with your infantery company.

And draught, the lighter the barge the closer to land it comes before getting stuck.



Cheers
/John T.

Andreas
Member
Posts: 6938
Joined: 10 Nov 2002 14:12
Location: Europe

Re: Fighters and Barges

Post by Andreas » 24 Apr 2007 08:55

John T wrote:
Andreas wrote:
As for all this reinforcement of the barges for protection with sand, steel, and whatnot, has a calculation been made of how e.g. infilling of the empty spaces with sand affects buoyancy and thereby load carrying capacity of the barges? It is a straight trade-off. For every kilogram of sand/steel that is used to protect the barge from enemy action, one kilogram of freight has to stay in France. There is no free lunch here.

All the best

Andreas
What where the average capacity of these barges?
bulk loads of 100-400 tons?

What do a infantery company weights?
If you want to use a barge with such a light load you'd like to weight her down with ballast and sand and steel plate is pretty good ballast.

I see two tradeoffs,
Center of gravity to aviod that the barge becomes top heavy,
so you have to load 200 tons on sand low and add 50 tons of steel plate on the top and then fill the space between with your infantery company.

And draught, the lighter the barge the closer to land it comes before getting stuck.



Cheers
/John T.
I was not aware that the invasion force was restricted to infantry companies.

All the best

Andreas

User avatar
LWD
Member
Posts: 8584
Joined: 21 Sep 2005 21:46
Location: Michigan

Re: Fighters and Barges

Post by LWD » 24 Apr 2007 13:16

John T wrote: What where the average capacity of these barges?
bulk loads of 100-400 tons?
From earlier quotes I believe that is substantially correct. According to the post by Paul Lakowski I've quoted before most were apparently around 350 tons with a fair number rated at ~650 tons. However I suspect that this is their capacity on canals or rivers. Given the dimensions listed there for each additional .1m of freeboard desired the smaller ones would loose ~20 tons of capacity and the larger ones ~33 tons. It is sated that 2m of freeboard was required. I'm not sure what the freeboard was when operating in canals or rivers. If it was say 1 meter then 350 ton barges would be reduced to a load of 150 tons and thats before any concrete, steal, engines, etc were added. Similarly the 650 ton barges would be restricted to ~320 tons.

As for how much a company weights. I have an org chart for and a German Air landing rifle company at hand. It list 140 men figure 100-150 kg per man + another 10 tons or so for vehicles and horses. That comes to ~ 24 to 30 tons. So they are not weight limited for an infantry company. Support units are likely a different story.

Andreas
Member
Posts: 6938
Joined: 10 Nov 2002 14:12
Location: Europe

Post by Andreas » 24 Apr 2007 13:34

Freeboard at full load in rivers apears to be very close to or is zero. I have seen barges run down the Rhine with water washing up to the internal freeboard. Running up they seem to have more freeboard it seems. I'll try to take some pictures when I go to visit my parents next.

http://www.fotocommunity.de/pc/pc/cat/2 ... ay/7883965

A bit more freeboard on this one:

http://www.fotocommunity.de/pc/pc/cat/2 ... ay/7566751

All the best

Andreas
Last edited by Andreas on 24 Apr 2007 13:56, edited 2 times in total.

Andreas
Member
Posts: 6938
Joined: 10 Nov 2002 14:12
Location: Europe

Post by Andreas » 24 Apr 2007 13:50

leandros has stated elsewhere that barges were presumed good until sea-state 5-7.
leandros wrote:Schenk is detailing the sea-going capabilites of the barges in general. These are very different from the previous cemented opinions on same - and much better. His information is based on actual tests performed by the German 17. ID and the fact that west-going positioning barge towing convoys always went as planned in spite of variable weather conditions. If I remember correctly wind forces 6-8 and sea states 5-7 were mentioned as acceptable.


Assuming that the same scale was used, that implies that they would have been good for waves of up to 9m (Sea state 7 has waves up to 9m height) and gale conditions (Beaufort 8). I find that hard to believe, and rather think that leandros is (again) confusing things or that Schenk has no idea what he is talking about, since the two sets of numbers are contradictory.

http://en.wikipedia.org/wiki/Sea_state :
- 5 Rough 2.5 to 4 m
- 6 Very rough 4 to 6 m
- 7 High 6 to 9 m
http://en.wikipedia.org/wiki/Beaufort_scale
- 6 windspeed 22-27kt wave height 3m
- 7 windspeed wave 28-33kt wave height 4m
- 8 windspeed 33-40 wave height 5.5m
In either case, I think it is a highly optimistic assessment, and can only apply to a very lightly loaded barge where the load has been professionally secured.

All the best

Andreas

User avatar
LWD
Member
Posts: 8584
Joined: 21 Sep 2005 21:46
Location: Michigan

Post by LWD » 24 Apr 2007 15:40

Here is a bit more extensive quote from Paul's post over on feldgrau. (from page 12 of the German Air Craft carrier thread on the KM board some of the hotlinks previously posted appear to be broken now)
All barges had to meet following naval requirements…

Able to handle open water up to sea state 2 [Significant wave height of 1.4 feet or 0.4 meters], which was the basic English channel sea state.
Able to land on beaches with slope of 1 degree
Able to transport a 25 ton tank
Able to use all Dutch Belgian and French canals.

However the barges exceeded these figures , here’s a quote from Schenk “Invasion of England 1940” Translated 1990, pp 70
"For the first criteria it was calculated that the barges would need a freeboard of at least 2 m and would have to be in a good state of repair. As it turned out , the barges were more seaworthy than expected, shipping little water during exercise in winds of force 4 to 5 and coping well with waves. Even at wind forces of 6 to 8 only two barges reported damage to external bow doors during one exercise with the 17th Infantry Division."
Note that it doesn't say what the freeboard was when they experianced the force 4 & 5 winds (or 6-8) for that matter. If the fordeck is covered and they are headed into the waves it is not unreasonable for them to not take in much water even if the waves slightly exceed their free board.

I don't have the book a bit more detail on these test would be interesting.

Andreas
Member
Posts: 6938
Joined: 10 Nov 2002 14:12
Location: Europe

Post by Andreas » 24 Apr 2007 16:59

LWD - thanks for reposting this. It is good to see that leandros is the culprit again in getting things wrong, and not Schenk.

Schenk's quote is interesting, but it does not tell us a number of things, and I think it portrays the barge performance in a flattering way. Questions that come to mind are:

- what kind of barges are we talking about here (size, propulsion, etc.)
- how were the barges in question loaded and what was their freeboard?
- what did they actually do to cope with the weather? Continue to steer course in order to stick to the timetable even if it went in parallel or an unfavourable angle to the waves, or heave-to and ride it out taking them over the bow?
- what was the effect of the high seas on the men on the barges?
- "only two" barges reported damage - how many participated in the exercise?
- did all barges make it to the landing site, or did some turn back?

All the best

Andreas

User avatar
LWD
Member
Posts: 8584
Joined: 21 Sep 2005 21:46
Location: Michigan

Post by LWD » 24 Apr 2007 17:35

A couple of other important factors would be:
1) The distnce between waves. The stresses tend to be much higher if the vessel is a less than two wave lengths but longer than say half a wave length.
2) How long were the barges in these conditions. If they were in them for only a few minutes or 10's of minutes the implications of getting caught out in such weather for hours are not good.

RichTO90
Member
Posts: 4238
Joined: 22 Dec 2003 18:03

Re: Fighters and Barges

Post by RichTO90 » 24 Apr 2007 18:13

John T wrote:What where the average capacity of these barges?
bulk loads of 100-400 tons?

What do a infantery company weights?
If you want to use a barge with such a light load you'd like to weight her down with ballast and sand and steel plate is pretty good ballast.

I see two tradeoffs,
Center of gravity to aviod that the barge becomes top heavy,
so you have to load 200 tons on sand low and add 50 tons of steel plate on the top and then fill the space between with your infantery company.

And draught, the lighter the barge the closer to land it comes before getting stuck.
There appears to be some real confusion of terms here, which is typical when talking about seagoing vessels. First you have to understand the parameters.

'Tonnage’ is actually a number of different things in respect to shipping:

Short Ton equals 2,000 pounds, Long Ton equals 2,240 pounds, Metric Ton equals 2,204.6 pounds. All are measures of weight.

Gross Register Tonnage (GRT) is a measure of the entire interior space in a ship as measure by Register Tons (100 cubic feet or 2.83 cubic meters). It is not actually a measure of cargo capacity; it is a measure of volume.

Dead Weight Tonnage (DWT) is a ship's total carrying capacity including the ship's gear, supplies and crew, in long tons, i.e., 2,240 pounds (1.016 metric or 1.12 short tons). It is a measure of weight and not of volume. The Dead Weight Effective Lift of a cargo vessel is expressed in long tons and is typically less than 80 percent of its Dead Weight Tonnage.

A Measurement or Ships Ton is 40 cubic feet of space (1.13 cubic meters), conversion of measurement tons to weight reflects the density of the cargo.

Net Tonnage is the entire useful cargo capacity of a ship expressed as register tons.
1,000 GRT = approximately 1,500 DWT = approximately 1,200 Long Tons of Dead Weight Effective Lift = approximately 1,775 measurement tons.

The vessels in question were the Prähme – un-powered barges, over 2,000 of which were confiscated in Belgium, Holland, France, and Germany for use in the operation. There were generally two types the Spitsen or pinnace (typically 38.5 x 5.05 x 2.3 meters, 360 DWT or about 240 GRT) and the larger Kempenaars (or French Campinois, typically 50.0 x 6.6 x 2.5 meters, 620 DWT or about 413 GRT).

We may roughly calculate the DW effective lift of these vessels as about 288 and 496 long tons respectively. However, that works very well for high-efficiency cargoes like grain, coal and lumber, which the vessels were designed for and less well for military cargoes, which tend to be highly inefficient.

Military cargoes include lots of people, which are extremely low-density. For one thing you can't pack them like sardines in a tin, it makes them cranky. Typically for any trip more than a few hours long at least a measurement ton must be allowed per man, so that 125-kilo man (with his equipment) is roughly equal to one-half a 'ton' (GRT). Or to put it another way, your 125-kilo man is taking up the space that typically could be occupied by 665 kilos of more efficient cargo. BTW, horses are worse and more cantankerous to boot.

Now a tank is more efficient, we could estimate that a 20 metric ton tank probably takes up about 20 cubic meters of space, so 1 metric ton per roughly 0.88 measurement tons. But then we have the opposite problem, the hold deck has to be capable of supporting that weight.

Military cargoes in an assault also need to be highly accessible. They can't be packed in as tightly as possible for efficiencies sake. Typically, the US Army found that in regular shipping from the US to Britain, about 70 to 80 percent of a ships usable capacity (it's 'full and down' capacity where the maximum hold space used equals the maximum allowed weight) was normal and that assault shipping was even less, approaching half the ships normal capacity.

So overall we could expect that the Spitsen could probably accommodate the men and equipment of an infantry company, without the vehicles, horses, and other baggage of the Troß. The Kempenaars would easily accomodate an infantry company, possibly including the Troß. Either could accomodate motor vehicles, probably 5 or so in the Spitsen and 7 or 8 in the Kempenaar. One efficiency would be that they at least could be embarked loaded with cargoes on the order of 2-5 tons per vehicle would be about average. Perhaps 2 or 3 armored vehicles could be loaded per Spitsen and myeb double that for the Kempenaar. Finally, probably two or more Spitsen would be required for a typical 4-gun artillery battery with its crew, prime movers and other vehicles. It is possible, but unlikely, that an entire battery could fit into a Kempenaar.

Eventually 1,336 Spitsen and 982 Kempenaars were collected, but as of 17 September only 1,277 were at the designated 'invasion' ports (Dunkirk, Ostende, Rotterdam, Calais, Antwerp, Boulogne, and Le Havre) while another 698 were being prepared or were on the way. That indicates that 343 more were collected sometime after 17 September.

Andreas
Member
Posts: 6938
Joined: 10 Nov 2002 14:12
Location: Europe

Post by Andreas » 24 Apr 2007 20:11

Rich

Thanks for that. Are those calculations based on preserving 2m freeboard and do they assume up-armouring of the prähme?

All the best

Andreas

Andreas
Member
Posts: 6938
Joined: 10 Nov 2002 14:12
Location: Europe

Post by Andreas » 24 Apr 2007 20:17

leandros wrote:This one is always "funny". You should read Peter Schenk. He describes the barge conversions in detail. 2300 barges were converted with bow ramps. They worked. It has also come to light that the barges were much more seaworthy than has been generally acknowledged in earlier discussions. What matters, in my opinion, is that the Germans found them feasible. Who are we to judge better than those who were to use them..... 8-)
Considering the error in your reading of Schenk that I have already pointed out, I would like to read the actual quote saying that 2,300 barges were converted. I am guessing we are talking about planned conversions, given the numbers Rich gave us, and not actual ones?

All the best

Andreas

RichTO90
Member
Posts: 4238
Joined: 22 Dec 2003 18:03

Post by RichTO90 » 24 Apr 2007 21:37

Andreas wrote:Rich

Thanks for that. Are those calculations based on preserving 2m freeboard and do they assume up-armouring of the prähme?

All the best

Andreas
The general dimensions of the Spitzen and Kempenaars are their typical exterior dimensions and are thus based upon them being a box, which they were not. Nor were they AFAICT actually 'barges', which are flat bottomed and which do have a very boxy cross-section. In fact, they were what are often termed 'keel boats' similar to those used on the Mississippi and Ohio rivers and on many US canals in the 19th century. That is they have an actual keel and a distinct bow and stern beak. Overall, I was generous in estimating them as two-thirds of their DWt. By using their dimensions and converting it to GRT (1 GRT - 2.83 cubic meters) you get 158 GRT for the Spitzen and 292 GRT for the Kempenaar, which given their hull form is probably high, probably about 85-90 percent of that may be close to the actual value.

And none of it has anything to do with 'freeboard', which is actually yet another problem. These vessels were designed for towing on canals and along coastal waters, so their depth in water is minimal and their freeboard is actually not a problem unless they are loaded 'full and down", which would be next to impossible in these circumstances. But, because they had so little depth in the water they were very poor at seakeeping, that is they were very vulnerable to having their course affected by wind, tides, and currents and would have been very difficult to direct, especially in the typical 'Troika' tows the Germans were contemplating (one towing vessel to three unpowered barges). Worse, the lack of seakeeping ability directly affects the tug as well, they would spend as much of their time trying to maintain direction as they would making forward progress, in any kind of seaway.

But of course if the only criteria is 'survivability' then they were very good indeed, that type of vessel has been little changed since first developed in the Low Countries about 500 years ago and they are very strong when maintained well.

RichTO90
Member
Posts: 4238
Joined: 22 Dec 2003 18:03

Post by RichTO90 » 24 Apr 2007 21:47

Andreas wrote:Considering the error in your reading of Schenk that I have already pointed out, I would like to read the actual quote saying that 2,300 barges were converted. I am guessing we are talking about planned conversions, given the numbers Rich gave us, and not actual ones?

All the best

Andreas
Actually they may be one and the same. The total 'aquired' was reported as 2,318, which all presumably were eventually converted. OTOH, it remains that as of 17 September only 1,277 were actually 'ready' on 17 September, with another 698 'being prepared or on the way'. And given that it required only about 700-odd RAF sorties over six missions to destroy 51 and damage 163, it remains questionable whether or not the Kriegsmarine would ever have been able to catch up, especially since the 'plan' appeared to call for a minimum of 1,653 for the initial Schlepp.

Andreas
Member
Posts: 6938
Joined: 10 Nov 2002 14:12
Location: Europe

Post by Andreas » 25 Apr 2007 09:29

RichTO90 wrote:
Andreas wrote:Considering the error in your reading of Schenk that I have already pointed out, I would like to read the actual quote saying that 2,300 barges were converted. I am guessing we are talking about planned conversions, given the numbers Rich gave us, and not actual ones?

All the best

Andreas
Actually they may be one and the same. The total 'aquired' was reported as 2,318, which all presumably were eventually converted. OTOH, it remains that as of 17 September only 1,277 were actually 'ready' on 17 September, with another 698 'being prepared or on the way'. And given that it required only about 700-odd RAF sorties over six missions to destroy 51 and damage 163, it remains questionable whether or not the Kriegsmarine would ever have been able to catch up, especially since the 'plan' appeared to call for a minimum of 1,653 for the initial Schlepp.
Kieser states that by 19 September the conversions had been completed, with over 1,800 barges prepared. This does not however mean that they all had bow doors (which is where I take issue with leandros' claim). Only some of them got these doors (no number specified), and conversion refers to all the work done on them, e.g. uparmouring where possible, reinforcing hold floors to take heavy loads, preparing them with boarding bridges to allow embarkation/disembarkation of horses, etc. pp.

All the best

Andreas

Return to “WW2 in Western Europe & the Atlantic”