River banks - Post christmas question

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UshCha
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Joined: 21 Sep 2016, 12:41

River banks - Post christmas question

Post by UshCha » 03 Jan 2019, 12:19

River banks are always an issue, both modelling and definition.

Definition first - I want to have a bit of fun with amphibious vehicles on a river. Now taking the River Trent close to where I live. The banks are about 5 ft high and near vertical in dry weather and being a UKthe river its proably only 150 ft wide if that (yes I know that would be a stream in other places in the world but the UK is really small). So I propose that viewed on the level beyoned 20m from any direction the vehicle is turret down.. Viewed from closer than 20mm (on the level) from the edge, on th near bank the vehicle counts as hull down, partially obscured by the bank and fully exposed on the far side.

So the questions are :-

Do these figures make it seem sensible, terrain ouside experience is much harder to deal with quickly in a simulation. I have assumed as the hull is only covered with a foot or two of water that it will have no effect on the armor protection of the vehicle.

Will an RPG penetrate and detonate 2 or 3 ft of water or should the vehicle be hull down to RPG's as the won't work for a second or two under water, or other opinion or data welcome. Obviously AP will not have an issue with this ammount of water.

Depiction - anybody got the perfect answer:- we have tried 3 approaches.

1) currently the least worst, thin blue plastic layed on top of the battlefield. Good bank definition, very flexible in terms of positioning, however visually no depth.
2) Being Hexon II rivers can be sunk into tiles. Better definition of banks. However major drawback is lack of flexibility, High storage space requirement, straights never in the right position and uniform 60 deg bends. Personlly I think it looks dafter than the plasic, hence second option.
3) home made banked river, sits ontop of playing surface. Potrentially more flexible but a lot of different lengths and curev angles required to gain flexibity. Misleading in that the river is above ground level in cases where it is not supposed to be. To keep to a sensible size the banks are usually too steep to not be noticeable. Like above ground trench systems sold by some folk, to me their failures mean thay are no better than not being there


I suspect my ideal would be very thin latex so it could be overlayed a bit like my card road system. I'm not enough of an artist to paint a river on card that would look sensible. current road river systen shown below. Note this is a game record photo not really aimed at optimum presentation.

https://www.flickr.com/photos/56805875@ ... ed-public/

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Seret
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Re: River banks - Post christmas question

Post by Seret » 03 Jan 2019, 14:53

Misleading in that the river is above ground level in cases where it is not supposed to be
I think it's a common enough terrain convention that nobody is going to be "misled". Obviously real rivers aren't above ground, but your only alternative is something like Hexon or Terraformer. But as you say, those have drawbacks too (cost, storage, transport, setup and teardown time). I'm totally ok with a nice aesthetically-pleasing river section sitting on the tabletop.

Re: RPGs vs things in the water. Shaped charges only work as advertised if they detonate at exactly the right standoff distance from the armour. Any RPG round striking the water and detonating will be too far out to do anything, essentially the same principle as slat armour. That's assuming the rocket doesn't just skip off the surface of the water. Actual attenuation of the jet moving through a more viscious medium would be genuine, but IMO as someone who's made a few shaped charges in my time the incorrect standoff would be likely to be far more of an issue. Having said that, I've never fired an RPG at a swimming tank, so who knows?

I'd go for hull down while swimming, and presenting a belly shot when climbing out.

Richard B.
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Re: River banks - Post christmas question

Post by Richard B. » 03 Jan 2019, 16:44

From what I´ve read about RPG rockets, I would guess water would nullify the round depending on the depth of water, a few inches may just allow the rocket to reach its target before the compression effect stops the rocket; then the result would probably be the same as normal........

The compression effect on projectiles in water in quite profound (quite unlike we see in the beach scene in Private Ryan :D ) I saw film of a 357 magnum sniper round loosing all momentum after virtually just foot or so, a 20 gauge deer slug couldn't even pass through a fish tank 18" wide side to side.......

As for the asthetic, I recently tried to place our "surface" river in a dip on the table using terrain tiles on either side to create a river bed, this looked better than our usual river running upon the flat tabletop.

I totally agree with your analysis the vehicle would be fully exposed entering, hull down whilst crossing/near to the far bank, but then belly exposed upon leaving.......
"“Sir with the compliments of my officer, your shooting was excellent – you killed four of our men”!
Un-named Traillieur to an artillery officer at R`Fakah, Morocco, Feb. 29th, 1908

dadlamassu
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Re: River banks - Post christmas question

Post by dadlamassu » 03 Jan 2019, 18:58

River banks are always an issue, both modelling and definition.

Definition first - I want to have a bit of fun with amphibious vehicles on a river. Now taking the River Trent close to where I live. The banks are about 5 ft high and near vertical in dry weather and being a UKthe river its proably only 150 ft wide if that (yes I know that would be a stream in other places in the world but the UK is really small). So I propose that viewed on the level beyoned 20m from any direction the vehicle is turret down.. Viewed from closer than 20mm (on the level) from the edge, on th near bank the vehicle counts as hull down, partially obscured by the bank and fully exposed on the far side.

I am talking about amphibious vehicles here. Those that are actually floating as opposed to the far more common assault by wading vehicles that run along the river bed. While the vehicle may be hull or turret down, the bow wave and wake make it very obvious and so spotting them is very easy. They are also very slow usually about walking pace giving time to adjust fire.

So the questions are :-

Do these figures make it seem sensible, terrain ouside experience is much harder to deal with quickly in a simulation. I have assumed as the hull is only covered with a foot or two of water that it will have no effect on the armor protection of the vehicle.

It will, water is incredibly good at slowing projectiles. However, it does amplify concussion (bursting the waterproof seals and collapsing wading screens) and depending upon the target swamp it with a wave or tipping it over, sink it with a water column.

Will an RPG penetrate and detonate 2 or 3 ft of water or should the vehicle be hull down to RPG's as the won't work for a second or two under water, or other opinion or data welcome. Obviously AP will not have an issue with this ammount of water.

Any HEAT round will probably fail to detonate effectively under water. Carl Gustav rounds fired at an Argentine ship that hit the water failed to penetrate its unarmoured hull. Much more effective is HE which sets up a concussive wave which bursts seals and collapses the wading screens. AP Shot will be slowed quite considerably by any amount of water. ATGW control wires are erratic when fired over water.

Depiction - anybody got the perfect answer:- we have tried 3 approaches.

1) currently the least worst, thin blue plastic layed on top of the battlefield. Good bank definition, very flexible in terms of positioning, however visually no depth.
2) Being Hexon II rivers can be sunk into tiles. Better definition of banks. However major drawback is lack of flexibility, High storage space requirement, straights never in the right position and uniform 60 deg bends. Personlly I think it looks dafter than the plasic, hence second option.
3) home made banked river, sits ontop of playing surface. Potrentially more flexible but a lot of different lengths and curev angles required to gain flexibity. Misleading in that the river is above ground level in cases where it is not supposed to be. To keep to a sensible size the banks are usually too steep to not be noticeable. Like above ground trench systems sold by some folk, to me their failures mean thay are no better than not being there

Depends on the geography. In flood plains, frequently river banks and river beds are higher than the surrounding plains. A good example is Iraq where for long stretches the Tiris and Euphrates are both higher than the surrounding land where bunds are needed to contain them. The same applies to significan lengths of the Nile, Mississippi/Misouri (levees), Netherlands (artificial) etc.

Entering the river will expose the top of the vehicle, vehicles in the river are vulnerable to underwater obstacles, boulders, sand banks etc and the most dangerous time the exit. The idea of amphibious vehicles climbing out is more hollywood than realistic. If the tracks/wheels have no firm purchase on the river bed then exit over any sort of river bank is nearly impossible. That is why the areas selected usually have gently sloping beaches. Having carried out river crossing exercises I have seen well prepared amphibians sinking without the stress of enemy gunfire. And then there is the river current that increases the chances of collisions and foundering.


I suspect my ideal would be very thin latex so it could be overlayed a bit like my card road system. I'm not enough of an artist to paint a river on card that would look sensible. current road river systen shown below. Note this is a game record photo not really aimed at optimum presentation.

https://www.flickr.com/photos/56805875@ ... ed-public/

What its your favorite and why?
[/quote]

UshCha
Posts: 165
Joined: 21 Sep 2016, 12:41

Re: River banks - Post christmas question

Post by UshCha » 04 Jan 2019, 00:29

not sure about the bow wave:-

https://www.google.co.uk/search?biw=192 ... 9OAfCMrGgM:
it does not look huge. However it would be easy to spot if looking down the river. Maybe not so easy to spot a distance from the bank. You can't see some narrow boats on the river I was looking at. Clearly the grand canyon river would make spotting very difficult unless at the edge but that was a bit too ambitious for me. Image

I considered that the only ways out would be where the banks were low for some reason. On the strech I was looking at there are a number of Marinas which would be ideal egress places along with a few sections where the bank was sloped not the more typical near vertical sections where egress would not be possible,

Interesting about the HEAT and AP maybe hull down at all times as its certainly KISS and not implausible.

dadlamassu
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Re: River banks - Post christmas question

Post by dadlamassu » 04 Jan 2019, 09:29

Look at a Russian exercise https://www.youtube.com/watch?v=JpRiTRuwLWQ

https://www.youtube.com/watch?v=51EjiT8WYLs

Wading, swimming and current effects https://www.youtube.com/watch?v=nVffY4eC7s8

Shallow entry-exit, bow waves, wake, slow movement, vulnerability and need for extensive support (even wothout an enemy)

There are lots more on youtube

UshCha
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Re: River banks - Post christmas question

Post by UshCha » 04 Jan 2019, 10:27

Great links, thanks.
We obviously have different opinions on what a big bow wave is. These looked small to me. The scenario I was looking at would be for a small recce vehicle(s) to use either a low bank or a marina ramp for entry and egress.

Interesting the tanks just drove agross, more or less. I does mean that I could specify the flow speed so up current would be quite slow. Like I said this would be a "big river" for me, the Trent is much narrower than this. ;-).

Seret
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Re: River banks - Post christmas question

Post by Seret » 04 Jan 2019, 10:46

UshCha wrote:
04 Jan 2019, 00:29
I considered that the only ways out would be where the banks were low for some reason.
Typically the exit point(s) will be identified and planned well in advance. Nobody does a river crossing seat-of-the-pants. Identifying good entry and exit points will have been done in advance by recce and the crossing point chosen carefully.

UshCha
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Re: River banks - Post christmas question

Post by UshCha » 04 Jan 2019, 11:05

That to some extent will be the aim of the scenario, recce.

dadlamassu
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Re: River banks - Post christmas question

Post by dadlamassu » 04 Jan 2019, 12:46

To preserve OPSEC the recce would normally be carried out by night and probably by rubber boat. Vehicles are too noisy. That said the use of a marina or other ramp needs recce for obstacles, mines especially off route mines and enemy forces. The follow up waves will need a bridge so your recce troops probably with engineers will need to hold a bridgehead and identify where the bridge(s) can be built.

An opposed river crossing requires a lot of planning and co-ordination of all arms and services,

A google search "assault river crossing pdf" will provide you with dozens of pamphlets and articles on the subject.

You mentioned "simulation" then this may be useful to you https://www.researchgate.net/publicatio ... ng_Details

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