Armor Plate and Self Sealing Tanks

syscom3 · May 17, 2009

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

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.

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 ASIN 159114471X)

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.

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.

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.

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?

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.

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.

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.

Armor Plate and Self Sealing Tanks

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