HK-1 evolution


ACCESS: Top Secret
Senior Member
14 June 2006
Reaction score
Like every airplane, the Hughes Kaiser Model 1 (AKA Hercules AKA Spruce Goose, Howard forgiving) passed through a series of concepts before his design being frozen. So, behold. The concepts were numbered from 1 to 7 (the "good" one) and you can notice influences from a number of famous seaplane design schools from around the world. Weight and overall dimensions went steadily up during the process. Unfortunately, nothing is (AFAIK) known of the shape of the original concept drawn by Kaiser's engineers and flatly rejected by Hughes. I owe these images to my friend Lark, to whom go my best wishes.


  • HK-1 Concept 1.gif
    HK-1 Concept 1.gif
    347.7 KB · Views: 824
Concepts from 2 to 4


  • HK-1 Concept 2.gif
    HK-1 Concept 2.gif
    166.9 KB · Views: 635
  • HK-1 Concept 3.gif
    HK-1 Concept 3.gif
    78.2 KB · Views: 589
  • HK-1 Concept 4.gif
    HK-1 Concept 4.gif
    127.5 KB · Views: 592
Last 3 concepts. Source is "Howard Hughes and his Hercules", by John J. McDonald.


  • HK-1 Concept 7.gif
    HK-1 Concept 7.gif
    229.8 KB · Views: 201
  • HK-1 Concept 6.gif
    HK-1 Concept 6.gif
    36 KB · Views: 212
  • HK-1 Concept 5.gif
    HK-1 Concept 5.gif
    129.3 KB · Views: 595
first of all thanks a lot for that post.

I've been looking for the book and it is not an expensive one. Do you recommend it? Looking at the pics I get very curious about that effort to produce the Hercules.
Thanks Scott, the unnamed one could well be a variation of Concept 3. As for the Kaiser Cargo, the gross weight would be right (the Kaiser proposal is referred to as 70-ton plane). The configuration of the tailess design doesn't seem adaptable as a seaplane, though. So perhaps there was another proposal yet.
Pome, I recommend but "cum grano salis", the book is at times in the often travelled road of "poor Howard, if the top brass hadn't hated him so much...".
One of the earlier HK-1 designs. Note 3-bladed props and clamshell loading doors, both of which were built and survived in a long term parts storage warehouse for several decades.


  • Hughes HK-1 Early.jpg
    Hughes HK-1 Early.jpg
    248.4 KB · Views: 341
Wonder what the designation would have been... Since this was a Hughes-Kaiser aircraft, I suggest XJRK-1...
well at the end a short flight @ 26 metres (officially) or 10 metres ( for more observers) altitude at 150 km/h for one mile : unique and last flight ! ;D ;D
Where was mistakes on these project ? ??? ???
Unsufficient power or what ? :(
Makes me wish I knew where my souvenir book from the Spruce Goose was. Some of the pics Skybolt posted were in it. My folks won a CA vacation in the 80's and we visited the Long Beach site and I remember the souvenir book they got me. I just wish I could remember where it went to.
To Stargazer - by suggesting that designation you may have planted the seed for much confusion amongst aviation historians of about 50 years from now. ;).
Of course the designation XJRK-1 was already used for a four engined light transport flying boat for 37 passengers to be built by Nash Kelvinator but which was not built. A Nash Kelvinator advertisement from 1942 shows the Sikorsky JR2S (S-44). It is possible that consideration was given to building the JR2S at the Nash Kelvinator plant as XJRK-1, although there is no evidence whatsoever to support this assumption.

Seriously, from what we read about the relationship between the Kaiser concern and the US Government, it seems totally unlikely that the US Navy would have been interested in that aircraft (and if it was, would not have been allowed to be so). So my strong suggestion is that the pic in US Navy markings is just another one of Howard Hughes' dreams.


  • K-JR1K [possible].JPG
    K-JR1K [possible].JPG
    27.1 KB · Views: 225
Stargazer2006 said:
Wonder what the designation would have been... Since this was a Hughes-Kaiser aircraft, I suggest XJRK-1...

I'd have thought that depended on who was going to operate it. US Navy or USAAF?
Neither, maybe. The contract was signed by the Defense Plant Corporation, a subsidary of the Reconstruction Finance Corporation, owned by the Department of Commerce. It could have been operated by the DoComm, like a cargo ship.
A little article on the HK-1
I have a 1945 era production report on the HK-1 by the same people who did the XF-11 report. However, it's low on my list to OCR right now. Give me a few weeks to get around to it.
Found on ebay, Henry Kaiser with a model of an early design in 1942


  • 11857025.jpg
    93.3 KB · Views: 219
  • 11857024.jpg
    95 KB · Views: 222
From the book, Howard Hughes and the Spruce Goose,

and as displayed by my dear Skybolt at first three posts,but in a clearer views.


  • 1.png
    335.3 KB · Views: 61
  • 2.png
    372.9 KB · Views: 51
  • 3.png
    371.6 KB · Views: 51
  • 4.png
    339.5 KB · Views: 49
  • 5.png
    329.8 KB · Views: 50
  • 6.png
    352.5 KB · Views: 46
  • 7.png
    337.5 KB · Views: 45
  • 7-1.png
    71.8 KB · Views: 75

I've just located a NACA report on the resistance testing of the HK-1

Hopefully, this link is more permanent:

It should lead to NACA-WR-L-683 ... I'm not a big fan of that search engine's user interface, to put it very mildly.

Resistance Tests of a 1/16 Size Model of the Hughes-kaiser Flying Boat, NACA Model 183

Tank tests were made of a hull model of the Hughes-Kaiser cargo airplane for estimates of take-off performance and maximum gross load for take-off. At hump speeds, with the model free to trim, the trim and resistance were high, which resulted in a load-resistance ratio of approximately 4.0 for a gross load coefficient of 0.75. With a 4000,000-lb load, the full size craft may take off in 69 sec over a distance of 5600 ft.

Henning (HoHun)
From this book.


  • 18.png
    1.1 MB · Views: 34

Similar threads

Top Bottom