I was reading recently of concrete armour being used on Finnish Stug III's in the Continuation War. Was this at all effective ?

I am guessing it was partly to dissuade magnetic mines or captured Panzerfausts (much like the log armour) as I can't imagine it having much utility versus solid shot or AP rounds.

Anyone know more details ?

thanks in advance

It probably had much more to do with crew morale than any real protection. I can't see concrete offering much resistance to AP rounds.

Iv got some exp fighting with virtual Stug, so here is my 2 cents.

Side was reinforced with wooden logs. Extra protection against 14.5mm?
Thin parts of the front was reinforced with concrete. Extra protection against 45mm?

My resources suggest that you're guessing correctly, in two particulars. First, it's more difficult to attach a limpet-mine to a magneto-conductive surface which has been overlayered by one which has not (depending on the thickness of the non-conducting surface). Second, the HEAT warhead has to deal with what is now a laminated-armor cross-section.

How effective? Couldn't say; but if it was more than 'nil' in that regard, then maybe that would have been deemed good enough.

Note the variety of applique armors applied to various Allied tanks, to include bedsprings, sandbags, logs, etc.


Shot

In January 1944 the Inspektor der Artillerie determined through test firing that adding concrete was not beneficial - it added extra weight and was not effective against AP. Apparently manufacturers stopped adding concrete armor after these tests but troops in the field continued to do so. Spielberger is not clear on this but I get the impression that the concrete armor was applied at the factory prior to this determination.

Don't mix up concrete armour and Zimmerit.

Zimmerit was a hardening paste that covered all accessible surfaces of tanks and assault guns for a long period (sometime in 43/44).

I've seen photos and drawings of StuG III who had something very different; actual concrete armour, used to create a sloped armour area at some horizontal/vertical plate frontal armour sections.
That covered only a small part of the frontal silhouette, though.

The StuG III had some troubles with ground pressure and this weight inefficient add-on armour was likely no good idea. But the weight was probably no more than 100 kg anyway.

Yes, the concrete armor on the Stug III was very limited - basically a square block of concrete in front of the driver's compartment. Zimmerit was applied on AFVs starting in 1943 and was discontinued in September 1944 because it was felt that it presented a fire hazard. Zimmerit added about 70kg to a Stug III.

Concrete isn´t that bad as armor protection. After all bunkers, and military construction such as walls, enclosures are often made of concrete.


The table (I, hope it looks like one) is off first google try and gives armor penetration of KwK L24 75mm and KwK L43 75mm on steel and concrete for 0, 1000 and 2000 meters. Not that bad for concrete.

Now you can go along and determine the weights of steel and concrete object of equal protection. I don´t care to right now.




Steel vs Concrete

L 24 / AP : 62 vs 81
L 24 / AP : 49 vs 66
L 24 / AP : 39 vs 49


L 43 / AP : 139 vs 208
L 43 / AP : 113 vs 170
L 43 / AP : 91 vs 137

millimeters, of course. sorry.

My take on the addtional slabs of concrete on the Stugs was that someone - not too high a rank - had a "bright" idea and some construction company had leftover capacity to make concrete things to fit on the tanks.

Didn't Germans have shortage of right about any materials? Oil and metals in particular.

Yes, everything but mustard seed. Sorry, old joke that is.

Steel it seems they had enough. The Stug front plate wasn´t made of concrete INSTEAD of steel.

Regards

Now you can go along and determine the weights of steel and concrete object of equal protection. I don´t care to right now.
Steel vs Concrete

L 24 / AP : 62 vs 81
L 24 / AP : 49 vs 66
L 24 / AP : 39 vs 49


L 43 / AP : 139 vs 208
L 43 / AP : 113 vs 170
L 43 / AP : 91 vs 137

millimeters, of course. sorry.

[/quote]
These concrete numbers seem very low. For the L24 we get about 30% greater thickness penetrated than steel giving us a thickness efficiency of about 0.8 and a mass efficiency of 2.5 due to concrete massing about 1/3 of steel. For the L43 we get TE of about .67 and a ME of 2.2. If these numbers are correct then concrete armour appears rather good vs german AP rounds.

I don't have any data on german AP rounds vs concrete for comparison:
Tests on steel APDS (10:1 L:D) ~0.1 TE 0.3ME
105mm M1 HE 457mm-335mm over similar range with concrete piercing fuse,
90mm M71 HE 1m-0.5m
Tests of 8.8cm L56 HE found it could breach a 2m wall with 8 closely spaced shots

Does anyone have more data on WW2 type AP rounds vs concrete? Do they perform much worse than HE rounds? I would have thought that AP rounds would penetrate a greater thickness of concrete but not reduced as large a volume of the wall to rubble making HE rounds typically a better choice for obstacle reduction.

Regards,

Jay

I recall seeing it applied to the sides as well, and to the upper fraction of the hull.


Shot

You're right - I was looking at a picture of a Stug IV, which has a different hull form, when I wrote that. The Stug III commonly had the concrete applied to the sloping part of the hull to the left and right of the main gun. I looked through Spielberger's book on Stugs but didn't see any photos of concrete applied to the sides of the hull.

Andreaslarka.net has good pictures of Stug III G with add-on concrete armour:

http://www.andreaslarka.net/ps531033/ps531033.html

For exaple:



This Stug is in front of one of the Karelia Brigade barracks in Vekaranjärvi. Andreas has multiple pics of it on his page. Also note the logs as add-on side armour.

Good picture.
Those thin armor plates (sweet spots) are covered with concrete.
That part can be penetrated even lower calibers.

Don't know about the effectiveness of the concrete armor, but Erkki Käkelä's book Laguksen rynnäkkötykit has some info on the add-on armor in the finnish sturmis. The book says that on July the 2nd 1944 1st lt Talvitie suggested to btl cmdr major Åkerman that three logs should be added to both sides of the hull, track links to the lower hull front and reinforced concrete added to the front of the fighting compartment to increase armor protection. The logs, track links and the add-on concrete armor was then added by the divisional armor repair shop at Enso. According to Käkelä's and Lärka's book Suomalaisten rynnäkkötykkien kohtalot, at Enso they also bolted additional steel armor plates to the lower hull sides, welded a protective steel vizor above the drivers vision slit, welded additional steel plates to both sides of the gun mantlet to protect the crew from shell fragments and rifle caliber bullets and welded an additional steel plate to the loaders side of the front of the fighting compartment.