# Armor Plate and Self Sealing Tanks



## syscom3 (May 11, 2009)

Many people (myself included) talk about the following. But you know, maybe we really don't understand it. I know its different from airplane to airplane, but its probably similar to one degree or another.

For armor protection for the cockpit seats, just how much weight does the armor weigh, and what type of ballistic protection does it afford [like how much weight would the Zero gain if they used armor seat protection]? 

What other parts of an aircraft also gets armor protection? Linkages? Fuel line junctions?

For self sealing fuel tanks, just what exactly is the weight and volume penalty?


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## drgondog (May 11, 2009)

syscom3 said:


> Many people (myself included) talk about the following. But you know, maybe we really don't understand it. I know its different from airplane to airplane, but its probably similar to one degree or another.
> 
> For armor protection for the cockpit seats, just how much weight does the armor weigh, and what type of ballistic protection does it afford [like how much weight would the Zero gain if they used armor seat protection]?
> 
> ...




The fighter armor plate doctrines were all over the place and weight penalties ranged from ~ 45 pounds in a P-51 (1/4" to 5/16" hardened steel aft of seat - only) to 260 pounds for the later model P-39D's. The P-63 cut it down to ~120 pounds. The P-47 was around the 60 pound - all aft of seat.

The Spit (most) had 8mm armor and all aft at about 60 pounds. The IL-2 was at top extreme and the FW 190A-8 had back/side/front armor plus 30mm glass on front windshield (and behind head aft of seat?) This ship also had some cowl armor to provide additional protection to the engine from head on 50 cal fire

The LW doctrine IIRC was geared to stopping a 50 caliber round at 200 yards to protect the pilot

Self sealing tanks usually had a single layer (later a double layer) of rubber/neoprene type lining on outside of cell - usually targeted to withstand a 12.7 ball/api hit.

None of the self sealing tanks were very effective against an explosive 20mm in context of rupture.


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## comiso90 (May 11, 2009)

I imagine that when the self sealing tanks took hits, they were drained and properly patched after the mission. The self sealing feature was effective enough to get the pilot home but was not considered an actual seal.. correct?

.


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## syscom3 (May 11, 2009)

How much volume in the fuel tank is devoted to the compounds that made it self sealing?


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## drgondog (May 11, 2009)

syscom3 said:


> How much volume in the fuel tank is devoted to the compounds that made it self sealing?



The only one example I have looked at was about 1/4" thick layer of what seemed to be two laminates (hard to see)


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## renrich (May 13, 2009)

According to Dean, "America's Hundred Thousand" the Wildcat held 160 gallons of internal fuel in unprotected tanks and 147 gallons in protected tanks. In the F4F3 the armor weighed 155 pounds, F4F4, 165 pounds and FM2, 223 pounds.


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## syscom3 (May 13, 2009)

It doesn't seem that armor plate for the cockpit doesn't add to much weight. Ditto with the self sealing tanks.

I wonder why the Japanese came to different conclusions.


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## BombTaxi (May 13, 2009)

I think the Japanese were perhaps hoping to outrun or out-turn anything heavily-armed enough to shoot them down - a bit like the battlecruiser vs battleship debate at sea. This certainly seemed to work for them in the very earliest days in the war, but they obviously didn't think about what would happen when the enemy sussed thier tactics and developed their own responses...

A further thought - at the time the Zero was designed, most a/c were packing 2-8 rifle calibre MGs. 50s and 20mm cannon were rare, so perhaps the Japanese incorrectly anticpated the kind of punishment the Zero et al. would receive?


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## Soren (May 14, 2009)

The Japanese were on to something if they could but have kept the speed climb rate of their a/c to either the same level or higher than that of their enemies. 

The Ki-84 was approaching this, and with better built engines, fuels and better trained pilots it could've proven superior to most Allied fighters.


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## BombTaxi (May 14, 2009)

The lack of trained pilots later in the war really showed up the deficiencies of Japanese aircraft. The Marianas Turkey Shoot was just one example of how easy it was for poorly trained pilots in substandard aircraft to be butchered by better aircraft flown with greater skill...


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## FLYBOYJ (May 14, 2009)

syscom3 said:


> It doesn't seem that armor plate for the cockpit doesn't add to much weight. Ditto with the self sealing tanks.
> 
> I wonder why the Japanese came to different conclusions.



You'd be surprised how much 150 - 300 pounds affects performance.


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## renrich (May 15, 2009)

FB nailed it. In an AC like the early A6Ms, with less than 1000 HP, a few hundred pounds was a big factor on performance. An AC like the Wildcat, with around 1200 Hp, when armor, self sealing tanks, folding wings and extra guns were added had it's performance substantially degraded. Later in the war, the A6M got more HP, which degraded it's range, but bigger MGs, SS tanks and armor kept the airplane from achieving better performance.


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## tomo pauk (May 15, 2009)

BombTaxi said:


> I think the Japanese were perhaps hoping to outrun or out-turn anything heavily-armed enough to shoot them down - a bit like the battlecruiser vs battleship debate at sea. This certainly seemed to work for them in the very earliest days in the war, but they obviously didn't think about what would happen when the enemy sussed thier tactics and developed their own responses...
> 
> A further thought - at the time the Zero was designed, most a/c were packing 2-8 rifle calibre MGs. 50s and 20mm cannon were rare, so perhaps the Japanese incorrectly anticpated the kind of punishment the Zero et al. would receive?



Hi,
A humble disagreement about the anticipated threats. The P. 24, I-16, Ms-406, P-38, P-39, Whirlwind, Bf-110, Fw-187 and Bf-109E-3 carried canons, and were widely advertised as such.

And the 2 LMGs were destroying bombers, let alone the fighters. At least above Poland.


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## syscom3 (May 15, 2009)

renrich said:


> ...... An AC like the Wildcat, with around 1200 Hp, when armor, self sealing tanks, folding wings and extra guns were added had it's performance substantially degraded. .....



How much additional weight did that take?

For the Zero, I dont think the addition of a 100 pound armor slab behind the seat would make much difference.


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## renrich (May 15, 2009)

The empty weight of the F4F3 was 5426 pounds, the F4F4 was 5778.9 pounds. The armor in the F4F4 was 7.5 pounds more than the F4F3. I would think that the SS tanks would not weigh more than the unprotected when they were full because of the gasoline displaced. The 352 pounds difference must have been mostly the folding wings and the two extra MGs. The early F4F3 lacked armor which weighed 155 pounds, so the startling difference in performance can be chalked up to a difference in weight of around 500 pounds.


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## syscom3 (May 15, 2009)

renrich said:


> The empty weight of the F4F3 was 5426 pounds, the F4F4 was 5778.9 pounds. The armor in the F4F4 was 7.5 pounds more than the F4F3. I would think that the SS tanks would not weigh more than the unprotected when they were full because of the gasoline displaced. The 352 pounds difference must have been mostly the folding wings and the two extra MGs. The early F4F3 lacked armor which weighed 155 pounds, so the startling difference in performance can be chalked up to a difference in weight of around 500 pounds.



Thanks Renrich. 

Did that weight figure include the 2 additional guns AND the additional ammo?


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## renrich (May 16, 2009)

The weight given is empty weight for both which would not include ammo but I believe tha ammo weight would be almost the same for F4F3 and 4 since the F4F3 carried 400 RPG and the F4F4 carried 240 RPG.


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## renrich (May 17, 2009)

Sys, I have been studying these tables in Dean on the F4F and it is a little confusing. I think the bottom line is that the F4F4 loaded for the same mission weighed around 350 pounds more than an F4F3, which would have armor and protected tanks. The FM2 weighed pretty much the same as the F4F3. It went back to the four guns and it's performance was similar to the F4F3's. There was also a F4F3A which served with the F4F3. The F4F3A weighed around 200 pounds less than the F4F3 because it had a different engine supercharger combination and did not have as good a high altitude performance. According to Lundstrom, there were times, early war, that the 3A and 3 served in the same squadrons off of carriers. That probably complicated matters because of the different performance at different altitudes but the Navy was desperately short of fighters in those days.


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## syscom3 (May 17, 2009)

So only 350 pounds of weight changed the performance that much?


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## renrich (May 17, 2009)

I believe that is the bottom line. The gross weight of the F4F3 in fighter configuration was 7150.5, the F4F4 was 7426. In overload fighter it was 7543 and 7972 respectively. You can see that difference in weights vary some according to mission. I suspect that most times in the Pacific battles the Wildcat took off with all the ammo and fuel they could stuff in it. These figures are from Dean but are Navair numbers.


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## syscom3 (May 17, 2009)

Did the addition of the 2 extra MG's add some parasitic drag?


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## renrich (May 17, 2009)

I would think that the two extra guns would definitely add drag but Dean does not address that. Reviewing the overload fighter figures the Wildcats are carrying the max internal fuel and max ammunition which accounts for all the additional useful load weight. That means that the 4 is carrying around 420 pounds more weight than the 3 plus additional drag caused by two guns and wing fold intersection.


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## elbmc1969 (Feb 25, 2019)

syscom3 said:


> So only 350 pounds of weight changed the performance that much?


The pilots were shocked by what a dog the -4 was. They'd been doing just fine with the quad .50s against the unarmored Japanese aircraft with unprotected fuel tanks. (The multi-engine aircraft burned merrily when the Wildcats made their standard deflection shooting passes and targeted the nacelles.

You can read all about it in Lundstroms's "The First Team: Pacific Naval Air Combat from Pearl Harbor to Midway" (Amazon product)


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## elbmc1969 (Feb 25, 2019)

syscom3 said:


> Did the addition of the 2 extra MG's add some parasitic drag?


No. The access hatches were trivial and the gunports were taped over.

If you mean induced drag, then yes, there would have been some increase. No idea how much.


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## Shortround6 (Feb 25, 2019)

elbmc1969 said:


> The pilots were shocked by what a dog the -4 was. They'd been doing just fine with the quad .50s against the unarmored Japanese aircraft with unprotected fuel tanks. (The multi-engine aircraft burned merrily when the Wildcats made their standard deflection shooting passes and targeted the nacelles.



The folding wing seems to have been worth about 190lbs and if the pilots were comparing an F4F3 without armor or self sealing tanks you could be looking at another 250lb difference. 

Something snuck in somewhere as an F4F-4 with 140.6 gallons of fuel and six guns with ammo went 7921 lbs while an F4F-3 with four guns, armor/SS tanks and 147 gallons was supposed to go 7432 lbs (useful load which includeds guns and ammo was around 100lbs lighter on the F4F-4) o blaming the loss of performance on the guns seems to be a mistake even if that was the most visible change.


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## elbmc1969 (Feb 25, 2019)

Shortround6 said:


> The folding wing seems to have been worth about 190lbs and if the pilots were comparing an F4F3 without armor or self sealing tanks you could be looking at another 250lb difference.
> 
> Something snuck in somewhere as an F4F-4 with 140.6 gallons of fuel and six guns with ammo went 7921 lbs while an F4F-3 with four guns, armor/SS tanks and 147 gallons was supposed to go 7432 lbs (useful load which includeds guns and ammo was around 100lbs lighter on the F4F-4) o blaming the loss of performance on the guns seems to be a mistake even if that was the most visible change.


Didn't mean that the guns were the sole cause, only that the pilots didn't see a need and preferred the greater firing time with the quad guns. Pilots seemed to think that the additional guns were adding weight, even with fewer rpg.


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## Shortround6 (Feb 25, 2019)

elbmc1969 said:


> Didn't mean that the guns were the sole cause, only that the pilots didn't see a need and preferred the greater firing time with the quad guns. Pilots seemed to think that the additional guns were adding weight, even with fewer rpg.


 And this is a case of pilots recollections/impressions run into listed weights, 4 guns in a F4F-3 are listed at 286lbs, 6 guns are 433lbs, however the 4 guns had up to 516lb worth of ammo while the 6 gun planes held 432lbs. so yes the 6 gun armament was a whopping 63lbs heavier. That is not quite fair because the the 6 gun planes had two extra sets of gun accessories (chargers, gun heaters etc)that aren't counted in the weights but you get the idea. call it 80lbs (?) on a plane that went around 7500lbs if the tanks weren't quite full? 

You think if I took the spare tire and jack out of your car you could tell the difference in the way it drove?


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## elbmc1969 (Feb 26, 2019)

I can only suggest reading the book. I believe it had specifics on weights and you can track down performance information in some detail. Again, the guns weren't the determining factor, there were lots of other things happening. I suspect that adding mass well out on the wings had some effect on roll rate, as well.

Please respond with whatever information you have, but please don't be offended if I don't reply further. I just think that I've spent enough of everyone's time on a marginal issue.


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## Greg Boeser (Feb 26, 2019)

I wonder how much of the unfavorable commentary on the F4F-4 was because it was being compared to the pre-war F4F-3 without armor and self sealing tanks?
The F2A-3 also received criticism for being an overweight dog, though most pilots who flew the unarmored -2 loved it.


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## Shortround6 (Feb 26, 2019)

elbmc1969 said:


> I can only suggest reading the book. I believe it had specifics on weights and you can track down performance information in some detail. Again, the guns weren't the determining factor, there were lots of other things happening. I suspect that adding mass well out on the wings had some effect on roll rate, as well.
> 
> Please respond with whatever information you have, but please don't be offended if I don't reply further. I just think that I've spent enough of everyone's time on a marginal issue.


See : http://www.wwiiaircraftperformance.org/f4f/f4f-4-4058.pdf

for some details of the F4F-4. Of note is item 18 at the bottom of page 5 and top of page six.
Some sort of test was done to measure roll but the test is not described. The same weight is listed for 3 conditions, 6 guns, 4 guns and no guns. 
to complete this rolling maneuver (whatever it was) took 6.0 seconds for the 6 gun set up, it took 5.9 seconds for the 4 gun set-up and no guns gave 5.7 seconds. 
0.1 seconds difference out of 6.0 seconds doesn't seem like a large amount 

Part of the answer _may_ be that the extra ammo for the 4 guns was out where the extra guns and their ammo was any way so there wasn't that much change in weight distribution.? 





Adding 190 rounds per gun is going to put a fair amount of ammo where the 3rd gun in each wing is.


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