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Wildnoob
08-18-2008, 06:22 PM
hi folks!

I are in doubth about self sealing tanks advantages and disadvantages.

already hear that both the imperial japanese army and navy air servies where against it in early war aircraft. but I would like to know why, wat disadvantages self sealing fuel tanks where gonna bring to the aircraft instead of non protected fuel tanks ?

this was already avaliable in the late 1930s, I would like to know if possible some reasons that lead japanese aeronautical industry to not use this improvement in it's pre and early war designs.

DmdSeeker
08-18-2008, 07:03 PM
Because it's heavy.

A standard fuel tank can be as light as a simple aluminium box or even just a rubber bag.

But a self sealing tank is a double layered metal and rubber sandwhich construction, and has considereable mass.

KrashanTopolova
08-18-2008, 09:52 PM
self-sealing fuel tanks minimise the chances of a white hot projectile detonating the fuel.

Pre-war and early War, both the JNAF and JAAF specifications called for an emphasis on manouvreability (the Ki-27 was more manouvreable than the Ki-43, the Ki-43 was more manovreable in turn than the Zero - which is saying something). To accomplish these specifications, light weight and flight surface performance were the top design priorities even at the expense of speed (they could have built a high-performance engine if they wished but the japanese designers had other things in mind).

With the entrance of well-armoured and well-armed US Navy fighters the Japanese changed design improvement strategy seeing that the arena had shifted in terms of fighter tactics and 'ruggedness' needed of a fighter (maximising the ability to take battle damage and survive). So improvements to service designs were made including self-sealing fuel tanks and armour for the pilot later in the war (and much more rarely - a parachute now and then). But these design improvements seem to have been catchup tactics with which to build a new fighter on an older (but not out-dated) design.

Wildnoob
08-19-2008, 08:58 AM
thanks guys! http://forums.ubi.com/images/smilies/25.gif

Taylortony
08-19-2008, 10:07 AM
Actually the primary aim of a self sealing tank is to do just that and prevent leakage, that is where the fire risk is when fuel and air combine... a self sealing tank is actually two layers of rubber, one being vulcanised rubber and one just untreated rubber, that swells when in contact with the fluid and seals the hole, which stops the fuel leaking and atomising, which is the fire risk.

You vary rarely as mentioned use a metal tank in a wing on larger stuff, you just use "wet wing" (unless you install bag tanks) which involves sealing the wing structure to form the tank..smaller stuff would have a metal tank or bag tank or indeed a wet wing dependant on the design..remember it all adds weight.

The (if I remember my time on them correctly) fuel tanks on the Chinook are very clever items, they are self sealing bag tanks capable of absorbing .50 cal hits, additionally the tanks have a fire extinguisher system built in that uses fuel as the extinguishant by filliing the air space in the tank with fuel spray so killing the chance of a fire... addditionally each of the tanks have self sealing couplings and in cases of a crash landing the tank mounting bolts will fail, the couplings will break and seal, the extinguishers will operate and the tanks will come away and roll off the sides of the fuselage increasing crew survivability.

R_Target
08-19-2008, 10:28 AM
Originally posted by KrashanTopolova:
(they could have built a high-performance engine if they wished but the japanese designers had other things in mind).

Actually, they couldn't. Which is why they didn't. Read "Eagles of Mistubishi" by A6M designer Jiro Horikoshi.

luftluuver
08-19-2008, 03:23 PM
Originally posted by R_Target:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by KrashanTopolova:
(they could have built a high-performance engine if they wished but the japanese designers had other things in mind).

Actually, they couldn't. Which is why they didn't. Read "Eagles of Mistubishi" by A6M designer Jiro Horikoshi. </div></BLOCKQUOTE>
Can you explain that statement for the Japanese built more powerful engines.

ie
Nakajima (Ha-45-21) Army Type 4 Model 21, 18-cylinder radial air-cooled engine for take-off, 2000 hp

R_Target
08-19-2008, 05:35 PM
Originally posted by luftluuver:
Can you explain that statement for the Japanese built more powerful engines.

ie
Nakajima (Ha-45-21) Army Type 4 Model 21, 18-cylinder radial air-cooled engine for take-off, 2000 hp

Indeed they did. But neither the Homare nor the other large radials were in production while the A6M was being designed.

luftluuver
08-19-2008, 05:42 PM
Originally posted by R_Target:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by luftluuver:
Can you explain that statement for the Japanese built more powerful engines.

ie
Nakajima (Ha-45-21) Army Type 4 Model 21, 18-cylinder radial air-cooled engine for take-off, 2000 hp

Indeed they did. But neither the Homare nor the other large radials were in production while the A6M was being designed. </div></BLOCKQUOTE>

Ah, OK. Thought that was where you were coming from.

KrashanTopolova
08-19-2008, 06:14 PM
Perhaps war time exigencies took away from Japanese aircraft development in the same way compromises may have affected German and British aircraft design and production during the war. re: the thread on the FW190 and mentions of the B-29 as a rush job in time for reaching the Japanese mainland.

The Japanese never developed efficient self-sealing tanks though they clearly saw the need for adopting them as the war in the Pacific progressed; and they never developed an adequate rough field strip matting. Meanwhile, the inventor of self-sealing tanks gained an international award for his invention for it had enormous military value.
Perhaps these failures (SS tanks and field matting for airstrips) are a case of myopia: It appears the Japanese military didn't really know from their mid-Pacific bases the conditions in the outer rim of the Pacific that they knew they were one day probably going to have to fight in. Their fighters designs pre-war, were good enough to outpace the US while concentrating on manouvreability; and they caused a shock on their debut. The Japanese air force military (a combination of naval and army leadership) did not feel a need for comparable or superior speed in their aerial strategy. Instead they developed group air tactics and wanted fighters that would outmanouvre the enemy fighters. The US meanwhile were smarter; developing ruggedness and firepower and later speed in the F4U; from WW1 the US had led all other nations in developing carriers and a fleet air arm strategy and tactics.

Later in the war the inadequacy of the Japanese fighter design strategy became apparent to themselves.
Nevertheless, the debut of the Ki-43-iii over Thailand in 1944 could well have been similar in performance if not impact as the debut of the FW190 over Europe.

But by then resources for the Japanese were fast dwindling; as they were for the Germans.