Evaluating Trumpeter Aero-1D External Fuel Tanks

[allthumbs]

The Douglas designed 300 gallon Aero-1D might be the most widely utilized external fuel tank of all time - at least a half dozen different aircraft types, mostly naval, adopted it. They were practically a fixture on Skyhawks, Intruders and Prowlers over their long service lives.

 

For more information about the Aero Series of fuel tanks, I highly recommend Tommy Thomason's July 2011 blog posting on the subject.

 

1/32 scale depictions are limited to Hasegawa (Skyhawk series), Zoukei-Mura (Skyraider series) and Trumpeter (Skyraider, Skyhawk, Intruder, Corsair ll and Harrier ll series). Fisher Model and Pattern also supplied a resin set in their Skyray kit and, as I recall, the tanks were marketed separately too.

 

The Hasegawa and Z-M offerings are both very good, conforming closely to published dimensions. Just as important, they appear properly proportioned, the ogival nose and tail sections matching up well to scale documentation. The Hasegawa tanks are let down somewhat by their out-of-round cross sections (read about my tank travails here  on the EA-6A  Electric Intruder build).

 

And while I have not viewed the Fisher tanks up-close, judging from photographs they look very good too.

 

Which brings us to Trumpeter, the focus of this thread, and their representations of the Aero 1-D tanks. And yes, curiously, there is more than one - several, in fact! 

 

Here is a look at those contained in their Intruder, Skyhawk and Skyraider kits:

 

 

I do not have in my possession either the Trumpeter Corsair ll or Harrier ll kits. So what follows is an examination of the four tanks included in the Intruder, Skyhawk and Skyraider kits

 

As you can see from the image above, each tank is different - which implies that at least three of them are wrong (yes, there were detail differences on the real tanks over the years, such as tail cone fittings; standard and bobtail, fin configuration and location and orientation of access doors, but the tank’s overall size and shape did not change). If nothing else, it’s an inefficient approach to mold making. Most kit manufactures would produce a single tooling that could be used across a range of kits. Indeed Trumpeter themselves follow such a practice when it comes to other underwing ordnance, such as missiles and bombs.

 

It's worth saying a few words about scale documentation and what constitutes "accuracy" with regard to these kits' fuel tanks. To start with, there's an excellent general arrangement drawing contained in NAVAIR 11-120A-2.1, a US Navy tech manual for shipboard ordnance.

 

Here's an copy of the drawing printed out to 1/32 scale:

 

As you can see, it contains a wealth of useful information for scale modelers including overall length and diameter and a description plus station locations for all of the salient details. 

 

While it's easy to have faith in the dimensions and weights published in these types of manuals, it's wise to be skeptical about the depicted shapes and proportions of the objects themselves. Very often they are inaccurate, sometimes to a large degree.

 

For example, look at this depiction of an A4D-1 Skyhawk from the official Flight Handbook:

 

To name just a couple of inaccuracies, the nose landing gear doors are too narrow and, most glaringly, the wing has too high an aspect ratio. But that's okay, as the drawing's only purpose is to show antenna locations. And it accomplishes this quite satisfactorily.

 

Getting back to our fuel tank drawing, this is a case where the draftsman got it right. The curves, lines and proportions are very accurately depicted in NAVAIR 11-120A-2.1. When compared to other documentation, such as photographs of the tanks taken from the proper distance and angle, such as these on the Cybermodeler website, it scales up nicely:

https://www.cybermodeler.com/aircraft/a-4/pages/aero_a-4_137.shtml

https://www.cybermodeler.com/aircraft/a-4/pages/aero_a-4_289.shtml

https://www.cybermodeler.com/aircraft/a-4/pages/aero_a-4_346.shtml

https://www.cybermodeler.com/aircraft/a-1/pages/aero_ad_009.shtml

 

And just to prove my obsessiveness (or nerdiness), I made detailed measurements of actual Aero 1D's, including tank circumferences at key station locations - direct evidence confirming the drawing's fidelity to scale, at least to an acceptably small margin for error.

 

 

So with this background information out of the way, let's have a look at each tank, starting with the A-6 Intruder offerings.

 

About the only good thing to say about it is that the overall length is correct. Except for the section between the Filler Cap and the Aft 14" Lug, it is simply too skinny.

 

 

Next is the Skyhawk:

 

A little better, perhaps. The nose cone is slightly too narrow, at least through STA 21.20. But like the Intruder tank, the rear half tapers too much. It also reaches its maximum diameter near STA 70.49 and immediately begins a gradual taper down aft of this point. The real tank maintains more or less a constant max diameter between STA's 78.47 and 114.47.

 

 

And finally a look at two different tanks that Trumpeter provide in their Skyraider kits, beginning with the full length version:

 

The proportions are greatly improved. Compared to the two before it, this tank maintains a close outline all the way back to around STA 190, where it begins to taper too sharply. It's a little too bloated in the middle (like me!), reaching a max diameter of 28 scale inches (closer to 1/30 scale).

 

 

Finally, here's the other tank included in the Skyraider boxing; the "bobtail" edition. In reality, this is the standard Aero-1D with its tail section removed (at STA 182.37) and replaced by a short, but streamlined cap. This version was finless.

 

We have a winner! Well almost. Like its longtail counterpart, the tank is a little too thick in the middle, but less noticeably so (its max diameter is only one scale inch above spec). It also displays the excessive (and by now familiar) "Trumpeter Taper" toward the rear, this time beginning near the aft drain. The bobtail cap is incorrectly shaped as the following photos make clear:

https://www.cybermodeler.com/aircraft/a-4/pages/aero_a-4_631.shtml

https://www.cybermodeler.com/aircraft/a-4/pages/aero_a-4_632.shtml

https://www.cybermodeler.com/aircraft/a-4/pages/aero_a-4_011.shtml

 

 

I wanted a pair of bobtails for a future build. Using the Skyraider tanks "out of the box," especially after reshaping the tail cap, would certainly get me close. But I found that by splicing together two of the tanks reviewed here and adding a new bobtail cap (from the spares box), I could achieve an even better result. 

 

Here's another look at the Skyhawk tank, this time moved back a ways on the plan:

 

Notice how well it matches the drawing from about STA 124.85 all the way to the end.

 

 

And after rummaging through my kit inventory, I came up with this: a pair of Monogram 1/48 F-101B Voodoo external fuel tanks. Their nose sections were a near perfect match for the bobtails in 1/32.

 

 

Here's the resulting hybrid:

 

Careful measuring, cutting and sanding (and some happy coincidences along the way) produced a near perfect fit of parts.

 

Ironically, Trumpeter's scattershot approach to the design and tooling of what should have been one common set of parts, usable across their range of kits, meant that they were bound to get close eventually, if only by accident. It turns out that by combining the best features of different versions, along with some "voodoo magic" from a now defunct Illinois based firm, a very convincing set of bobtail twins can be had.

 

Rich

Edited June 20, 2020 by allthumbs

[allthumbs]

38 minutes ago, Jennings Heilig said:

Don't make the mistake of assuming that the exact shape of the tank on that station diagram is accurate.  That's not what those drawings are intended to show.  It may look good, but there's no guarantee that the shapes are the actual shape of the tank.  The only way to verify that is to photograph a tank and compare the shape you see in the photos with the drawing and dimensions.

 

I agree Jennings. 

 

Here are some excerpts from my original post:

 

"While it's easy to have faith in the dimensions and weights published in these types of manuals, it's wise to be skeptical about the depicted shapes and proportions of the objects themselves. Very often they are inaccurate, sometimes to a large degree." 

 

"...this is a case where the draftsman got it right. The curves, lines and proportions are very accurately depicted in NAVAIR 11-120A-2.1. When compared to other documentation, such as photographs of the tanks taken from the proper distance and angle...it scales up nicely."

 

"And just to prove my obsessiveness (or nerdiness), I made detailed measurements of actual Aero 1D's, including tank circumferences at key station locations - direct evidence confirming the drawing's fidelity to scale, at least to an acceptably small margin for error." 

 

 

 

 

 

 

 

 

[Rick Griewski]

Model building nerds unite!  Useful analysis.

 

Thanks 
Rick

[allthumbs]

Images of images of images...the Frankentank overlaid and beside a good reference photo (from Cybermodeler):

 

 

Edited June 14, 2020 by allthumbs

[mkd1966]

Which 300 gallon version is this one and is it available on any 1/32 scale aircraft out there ? To me it looks like the same style, shape and design as the 150 gallon tanks also seen on this Skyraider and used on Corsairs, Bearcats and Tigercats... Just curious, Mike

 

Edited June 19, 2020 by mkd1966

[mkd1966]

Here are a couple more angles showing it's shape compared to the 150 gallon tanks... I think I like the looks of the big 300 gallon centerline in this style...

[allthumbs]

Hi Mike,

 

You bring up an interesting point, and one that shows how much tank and ordnance configurations varied during the 1950s and 60s, especially on Skyraiders and Skyhawks.

 

This A-1 is sporting “early” 300 gallon (belly) and 150 gallon (wing) tanks. Once again, Tommy Thomason to the rescue. As he mentions in this blog posting, they appear similar, though perhaps not identical to, the tanks used by earlier Grumman and Vought aircraft.

 

Rich

still hammering away at my Aero-1D fankentanks

 

Edit: To answer your question regarding availability of the early style 300 gal tank seen on Skyraiders, even late in their service lives,  I'm not aware of anything offered in 1/32. Both Trumpeter and ZM supply only the later streamline Aero-1D tanks. Perhaps others know more. 

 

 

Edited June 20, 2020 by allthumbs

[Starfighter]

Very interesting thread! I've drawn and printed some Aero 1Ds for my Prowler and Viking using the same drawing as reference a few years ago. It's probably time to finally start my range, maybe they could be helpful for some among us...

 

[allthumbs]

Almost done...

 

 

 

Edited July 10, 2020 by allthumbs

[Michael931080]

2 minutes ago, allthumbs said:

Almost done...

 

 

 

 

Will you be marketing these by chance??

 

[allthumbs]

Hi Michael,

 

No, these tanks (I'm building a pair) are one-offs, destined to hang from an A-4B Skyhawk.
 

However, someday soon, I would like to develop new tanks, with optional tail cones and fin configurations, to be used as patterns for a resin set. Given the problems with the Trumpeter offerings, I think there's room in the marketplace.

 

Rich

Edited July 10, 2020 by allthumbs