by Tommy H. Thomason

Wednesday, July 25, 2012

Douglas Low-Drag External Fuel Tanks Redux

I provided dimensioned drawings of the 150, 300, and 400-gallon Douglas low-drag external tanks here: http://tailspintopics.blogspot.com/2011/07/douglas-low-drag-external-fuel-tanks.html

The tanks and fins were standardized but the number and location of the fins varied with the specific location on a particular type.

The 150-gallon tank was common on the A4D-1 and early A4D-2s.

Because the tanks were very similar in shape, you have to look carefully to see which one is installed. In the case of the A4D, the clues are a somewhat smaller diameter relative to the airframe and more obviously, how far the tank extends behind the wing trailing edge and to a lesser degree, ahead of the wing leading edge.


Here is an example of a single 400-gallon tank on an A-4 and one with two 300-gallon tanks. Note that the 300-gallon tanks do not have fins, which is not unusual, but the forward location of the national insignia on an A-4E is.

I've seen questions about which kits have accurate external tanks so I did a quick survey of some of the 1/72 kits in my stash, comparing their 300-gallon tanks to the drawing. In rough order of acceptability:

Esci A-4 (A4D): Excellent

Hasegawa A-1 (AD): Almost perfect. Rounding the nose a bit provides almost exact length; the fins are a bit small but not objectionably so.

Tamiya F4D: Very slightly oversized, rounding the nose would be appropriate.

Airfix F4D: Very slightly oversized.

Airfix S-3: Basic size and shape okay; the fins need to be cut down. (The basic shape of the airframe is also better than the Hasegawa kit, e.g. the engine nacelles aren't circular.)

Hasegawa EA-6B: Basic tank okay but fins slightly undersized.

Fujimi A-6: Length okay but diameter a bit undersized and too tapered; fins good.

Hasegawa S-3: Too short by about 13" and forward edge of fin angled downward too sharply.

Fujimi A-7: Too short by about 31" and terrible fins

Airfix AD: Somewhat undersized (too tapered/conical) and fins too small.

Hasegawa A-4: Definitely undersized; could be sectioned to create the 150-gallon tank.

Matchbox F3D: 150-gallon size but forward part of tank is too tapered, conical.

Hasegawa F9F-8: 150-gallon size but too small in maximum diameter; taper down in diameter from mid section both forward and aft is too conical; and the fins are not correct

For some aftermarket options, see http://tailspintopics.blogspot.com/2013/08/things-under-wings-douglas-low-drag.html

Comments, additions, and corrections welcome.




3 comments:

  1. Tommy, I noticed another correction that needs to be done to the Airfix AD4-2 early versions, and if backdating to an AD4-1.
    Underneath each wheel sponson just aft of each door are a collision light, and a large blade like antenna sticking off of the sponson. These need to be removed.
    "But" leave the little fuel dump vent on the one sponson in place as that was there.
    Hopefully this makes since and maybe you can provide photo data to what I am talking about.

    Sincerely
    Scotty Battistoni

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  2. Scotty - Thanks for bringing that to my attention. I wrote it up here: http://tailspintopics.blogspot.com/2012/11/the-dirty-underside-of-a4d.html

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  3. Dear Mr.Thomason,

    In regards to the size of the Douglas low-drag external fuel tanks as represented in the 1:72 scale kits, maybe you will consider as useful the measurements I have taken for some of the kits that are not listed in your post.

    Fujimi A-4E/F kit # F24: L = 77.5mm, D = 8.7mm.
    Overall shape appears to be correct.

    Hasegawa AV-8B kit # D19: L = 85mm, D = 10.4mm.
    Definitely oversized.

    Academy OV-10A kit # 1665: L = 54mm, D = 7mm.
    Too small even for a 150-gallon tank.

    Sword F3D-2 kit # 72072, 300-gallon tank: L = 77.5mm, D = 8.5mm.
    Overall shape appears to be correct.

    Sword F3D-2 kit # 72072, 150-gallon tank: L = 61mm, D = 7.3mm.
    Apparently undersized.

    PS: Please let me know if you would like me to send photos of respective kit parts.

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