What if: 1935: how to purpose design a raider (HSK)

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kfbr392
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What if: 1935: how to purpose design a raider (HSK)

#1

Post by kfbr392 » 15 Feb 2017, 20:51

in this thread
http://forum.axishistory.com/viewtopic. ... 1&t=226923
we established the following:

the German HSK raiders of 1939-42 where an efficient means of war because of their following characteristics:
- being converted from ex freighters, and their weapons hidden behind fake walls, they appeared to be unarmed Allied or neutral cargo ships. This was their single greatest asset
- they had an endurance and autonomy of over a year
- they had sufficient armament to battle it out with Allied AMCs and more than enough to destroy their targets: Allied cargo ships

On the other hand, they were lacking:
- proper prewar doctrine, preperation and planning
- aircraft/rotorcraft that could be launched from deck and that could land on deck
- radar and top notch radio equipment
- modern flat trajectory artillery, at least some of them heavy flak guns
- even light armor
- speeds of >17 knots
- additional crew ameneties to make these long journeys bearable


So then lets investigate the following scenario.
It is 1935. OKM decides NOT to build the five Admiral Hipper class heavy cruisers.
Instead, some of the money is used to design and produce 10 purpose-built HSKs following (hopefully) all the above parameters.

How would they look like, what would their layout be? Show us your sketches!
(remember, they need to appear to be innocent freighters, at least when viewed from another ship through binoculars at lets say 5000m distance)

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Re: What if: 1935: how to purpose design a raider (HSK)

#2

Post by kfbr392 » 15 Feb 2017, 21:49

ok I go first.

here is a proposal on how a flight deck could be integrated while preserving the freighter look and not having the airflow obstructed by the ships superstructure.
Clearly a flight deck this small can only be suitable for slow double deckers, STOL aircraft and rotorcraft. My preferred scenario would be Fi 167 (from 1939 onwards).
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2017-02-15 20_47_04-1939_HSK-mod.pdf - Adobe Acrobat Professional.png


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Re: What if: 1935: how to purpose design a raider (HSK)

#3

Post by kfbr392 » 20 Feb 2017, 10:02

basically, the objective is to have a 17-20 knot Diesel powered long endurance ca. 7000 register tons "semi-carrier" that can quickly and effectivly be disguised as an Allied or neutral freighter, and that also has a strong artillery element.
Its aircraft/rotorcraft can well be light, slow and of limited performance if the small size of the flight deck does not allow for more competitive types of flying vehicles. The primary purpose of the airborne assets is not combat but instead the spotting of Allied cargo ships which the raider can then intercept and engange with this guns.

A good example of the Kriegsmarine having historically been willing to design a build a novel specalized ship class ist the Dithmarschen class of fast replenishment ships
http://www.globalsecurity.org/military/ ... rschen.htm
The Dithmarschen' were large, unarmored, civillian looking, cannon armed, 21 knot Diesel powered Kriegsmarine special purpose designs.

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Re: What if: 1935: how to purpose design a raider (HSK)

#4

Post by T. A. Gardner » 20 Feb 2017, 21:44

For aircraft, what you could do is something like this...

The ship has an awthartship's catapult (like on Bismarck) capable of firing off anything from a Storch to an Ar 196. You carry one or two of the later with folding wings in a hold along with several Fi 156 Storch. The later are the main scouting plane for the ship.
These are catapulted aloft... It wouldn't take much to get a Storch airborne so that's pretty easy to do. The cargo booms normally stored over the catapult are simply run to full up position out of the way.

For landing, the ship has an installed system similar to this:

Image

Put kingposts forward and aft on the ship for the booms that hold the landing cable, with the boom folding back against the kingposts when not in use. A cargo boom or whip is used to secure the booms in place at each end.

The Storch comes in from astern, with the ship turned into the wind to reduce landing speed. The plane has a hook on top as shown and it hooks the cable strung between the two booms outboard. Stored, the booms look like they are part of a normal cargo ship. The plane is then hooked to a cargo boom and lifted back aboard for storage and reuse.
Landing gear would be optional. You could eliminate it as unnecessary if you wanted to make the plane more compact.
This eliminates the problem of sea state. It could be used in anything from a dead calm to small white caps on waves. You really don't need it in stormy weather. Given the plane is a two seater, that means a navigator can be carried to allow the plane to find its way back to the ship when it flies out of sight of it. Armament isn't really needed, just a good radio.
You could have several planes aloft at a time if you wanted too. With proper camouflage paint on them, their small size and low noise would make them hard to spot. Maybe even add mufflers to the exhaust to make that even harder.
Against mostly merchant shipping these would be excellent spotter planes and probably go unnoticed by their eventual victims most of the time.

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Re: What if: 1935: how to purpose design a raider (HSK)

#5

Post by kfbr392 » 20 Feb 2017, 23:22

wow, that concept seems almost ideal for a raider!
where can we find out more about it?

in any case, the Fi 156 appears surprisingly well suited for shipboard use!
from wikipedia:
A design feature rare for land-based aircraft enabled the wings on the Storch to be folded back along the fuselage in a manner similar to the wings of the US Navy's Grumman F4F Wildcat fighter. This allowed the aircraft to be carried on a trailer or even towed slowly behind a vehicle. The primary hinge for the folding wing was located in the wing root, where the rear wing spar met the cabin. The long legs of the main landing gear contained oil-and-spring shock absorbers that had a travel of 40 cm (15-3/4 inches), allowing the aircraft to land on comparatively rough and uneven surfaces - this was combined with a "pre-travel" distance of 20 cm, before the oleos began damping the landing gear shock. In flight, the main landing gear legs hung down, giving the aircraft the appearance of a long-legged, big-winged bird, hence its nickname, Storch. With its very low landing speed the Storch often appeared to land vertically, or even backwards, in strong winds from directly ahead.
so it even got foldable wings in its standard configuration!

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Re: What if: 1935: how to purpose design a raider (HSK)

#6

Post by T. A. Gardner » 21 Feb 2017, 02:39

Here's a few sources on line:

http://wonderduck.mu.nu/various/the_lit ... t_carriers

https://laststandonzombieisland.com/tag/uss-lst-16/

Two LST were fitted with the system I showed. This is called "The Brodie device."

https://www.youtube.com/watch?v=7Wrz20iLAEA

If the Germans had a similar system, it could have easily been installed on a merchant ship such that rigging and storing it would be invisible at a distance. All you'd need are kingposts instead of single masts...

Image

You'd put the arms for the system on the forward and aft kingpost and store it against it when not in use.

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Re: What if: 1935: how to purpose design a raider (HSK)

#7

Post by sitalkes » 21 Feb 2017, 05:48

How to purpose design a Raeder? Would you need someone else in charge?

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Re: What if: 1935: how to purpose design a raider (HSK)

#8

Post by T. A. Gardner » 21 Feb 2017, 07:04

The ideal with a system like this might be...

You catapult launch 2 Storch to scout ahead of the ship. You ready two more for launch. When the two scouting return to land, you launch the next two. The two returned planes get serviced and readied for use. You have two more readied for launch. You carry like 10 total and can have 2 aloft pretty much all the time in daylight hours.

What would curtail flight ops are bad weather, need to camouflage the ship for approach of a target (to appear as a merchant), or you are in an area where there are few or no targets expected.

This might even make having a U-boat nearby to help take on targets that the plane(s) find.

Just a 100 NM search radius around the raider would more than quadruple its search area.

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Re: What if: 1935: how to purpose design a raider (HSK)

#9

Post by kfbr392 » 21 Feb 2017, 15:03

This Brodie device - or something quite similar - really appears to be just what was needed for the HSKs!
There are no technical hurdles and it could have been operational for usage with a slightly modified Fi 156 (Brodie hook, some equipment changes such as inflatable rubber dinghy etc.) in the Kriegsmarine by 1938 ... had this path been envisioned and followed... (which of course it was not in OTL)



Btw, an airplane flying at a height of 2500m will be able to see almost the entirety (nearly everything above the waterline) of a ship at 100Nm.
If the weather permits it, of course.

The range of the Fi 156 with internal fuel (2x 75l wing tanks) is stated as 385km = 208NM.
(I read that a 200l tank could be carried in the cabin instead of passengers but lets stay on main=wing fuel for this calculation.)
This would be sufficient to launch, fly out 20Nm while climbing to 2500m, then fly around the HSK in a full 360° circle with a radius of 20Nm, all the while having visual contact with the raider, then come in and land. Total distance traveled: ca. 170Nm.

The area thus observed would be a circle with the radius of 120-126Nm. That is scores of times more area under observation than only having the 13-19Nm radius observable using lookouts on masttops, as was done in OTL.

You do this 2-3 times a day with one Fi 156 at a time and have vastly increased your chances at spotting a target.


(3m target height means you can basically observe the whole target ship; 25m means you can observe the tips of its masts.)
Attachments
Unbenannt2.JPG
visibility as a function of height
Unbenannt2.JPG (27.31 KiB) Viewed 1478 times
Unbenannt.JPG
https://en.wikipedia.org/wiki/Horizon

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Re: What if: 1935: how to purpose design a raider (HSK)

#10

Post by kfbr392 » 22 Feb 2017, 14:43

actually, there might be an even simpler way of launching and recovering the Fi 156 from a ship... use the 3.5t crane used on Admiral Hipper class and Scharnhorst class. It has a quite long arm. It could be placed at one side of the HSK, as high up as can still be camouflaged, and swung out perpendicular to the hull. Its hook could be outfitted with a net. The Brodie hook on top of the Storch catches that net during "landing".

The relative speed of the Storch to the net during final approach would almost always be around 1kn since the wind speed (the big variable) and the forward motion of the ship (maximum 20kn) would in most instances add up to the stall speed of the Storch (minimum 27kn). Or be greater than it. In other words: using his throttle the pilot could sneak up on the net, and simply latch onto it.
Only when there is absolutely no wind, this type of "catch" would result in a temporary see-saw motion of the Storch, since the Storch is then ca. 7kn = 3.6m/s faster than the ship. The violence of this motion can be mitigated by increasing the distance between the crane hook and the COG of the Storch, i.e. having a longer net.

Aircraft launch:
if there is sufficient wind speed, i.e. >7kn, then one can simply launch by dropping the Fi 156 from the outswung crane (at wind speeds just above 7kn you would need full engine power for both the aircraft and the ship).
If the wind speed is <7kn, then you don't deploy aircaft on that day.
Or you need an additional device to launch the Storch.


Advantages compared to "full Brodie system":
- no need for double kingposts and extensive rigging
- faster and simpler aircraft recovery and launch
- this high-end crane can also be used:
-- to quickly deploy and recover decent sized motor boats for boarding parties and SAR
-- to rapidly move supplies from a captured ship to the raider
Attachments
3,5 t navy crane from Scharnhorst and Admiral Hipper .jpg
3.5t crane from Scharnhorst and Admiral Hipper
3,5 t navy crane from Scharnhorst and Admiral Hipper .jpg (23.78 KiB) Viewed 1420 times

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Re: What if: 1935: how to purpose design a raider (HSK)

#11

Post by thaddeus_c » 23 Feb 2017, 16:11

would still favor the small Flettner helicopter and/or autogyro. it would confuse issue if spotted as to whether they had been launched from ship or u-boat.

remember these are clandestine ships so they need to maintain their cover (as best defense.)

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Re: What if: 1935: how to purpose design a raider (HSK)

#12

Post by gurn » 23 Feb 2017, 18:26

Didn't some of the submarines have the ability to send a man aloft in a tethered hang glider? How much speed would be required for that? Would it be as simple as turning into the wind and proceeding at 10 knots?

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Re: What if: 1935: how to purpose design a raider (HSK)

#13

Post by kfbr392 » 23 Feb 2017, 23:09

gurn wrote:Didn't some of the submarines have the ability to send a man aloft in a tethered hang glider? How much speed would be required for that? Would it be as simple as turning into the wind and proceeding at 10 knots?
Focke-Achgelis Fa 330 „Bachstelze“ autogyro.
First flight from a ship: June 1942.
Minimum headwind (ship speed plus wind speed): 17kn.

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Re: What if: 1935: how to purpose design a raider (HSK)

#14

Post by kfbr392 » 23 Feb 2017, 23:34

thaddeus_c wrote:would still favor the small Flettner helicopter and/or autogyro.
agree. but both Fl 282 and Fa 330 were historically only mature in 1942. not pre-war.

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Re: What if: 1935: how to purpose design a raider (HSK)

#15

Post by thaddeus_c » 25 Feb 2017, 05:21

kfbr392 wrote:
thaddeus_c wrote:would still favor the small Flettner helicopter and/or autogyro.
agree. but both Fl 282 and Fa 330 were historically only mature in 1942. not pre-war.
of course you are correct but you are discussing an expanded or enhanced HSK program. the FA-330 at least seems quite feasible, even if it required a small motor and became a true autogyro.

the KM could use raiders as testbed for later u-boat use.

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