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1/24 Scratchbuilt Grumman XP-50 Skyrocket


Jim Barry

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Just thought I'd start blogging this build because it's happening now even though the Bearcat is still #1 in production.  I sent the engines I designed in 3D to Shapeways today and figured that's the beginning kick off moment of commitment.  For those of you that know what the XP-50 was when you read the title, way to go, because I did not until a few weeks ago when I stumbled on it reading about Bob Hall, the Grumman designer and test pilot who almost died in it. I was intrigued. It's clearly the development of the somewhat better known  XF5F Skyrocket that the Navy rejected but with a new contract to build a better fighter prototype  for the Army Air Corps, Grumman took their lost baby to a new party. Unfortunately, as a prototype it always played second string to the XP-49, a better-engined P-38 more or less that was charming the Army until well it wasn't. Grumman was told to keep developing the Skyrocket because it had lots of promise, too. But while most testing went well, there was one day that did not go so well and that was the day a turbosupercharger detonated and wrecked the hydraulics. Unable to effectively land without hydraulics, Bob Hall  bailed and the Skyrocket crashed into a bay on Long Island. That was the end of that. 

 Grumman's Tigercat came along a few years later and actually learned many lessons from this plane, but it was another plane all together really. I felt really sorry for the little thing, something they estimated could go 427mph. 

 

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Here's the work on the engines I sent to print today. I'm experimenting with Black Acrylic as a material as I'm really pushing the detail here quite a bit and they say this is the ultimate for detail. Unlike the Bearcat's engine which has many cooling fins detailing the cylinders, this one has them all! I've learned lots of tricks in the year of 3D modelling now and can produce this in a few hours (instead of weeks). For the record it's a Wright R-1820 Cyclone. It's what powered the B-17 , the Dauntless, the DC-3, the Buffalo and the Duck (and others if you want to wikipedia it). Print cost is $23 each. I think it's just going to look boss with two radials ; something I just felt I had to do once I realized what 3D printing can do. 

 

 

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Welp, that's it.  Stay tuned!  

Edited by Jim Barry
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Getting real tonight. 

 

Here's the spine . It's .08 sheet styrene but I only had 12 inches and will need to tack on a few more inches with some epoxy for the full length. Cut with a Dremel jigsaw but you have to be careful as the styrene will melt and reseal the cut if you cut too long and let the blade heat up. I learned that a while ago and it's nice to still remember the error. 

 

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Jim,

 

I used 80 thou for the spine on the F-90. I just traced the shape, scored it with a knife and snapped it out. Worked for me, but then I don't own a jigsaw. Would have tried it your way if I did have a jigsaw.

 

I guess you make it work with whatever you have.

 

Dan

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Hi Dan, Common ground on our spine choice!  I've cut it with a knife with the Fury but when I thought about doing more scratch I decided a little jigsaw will pay off. Pretty happy with my purchase. I'll be using it a ton for the Skyrocket. 

 

So, in the news, the engines came back from Shapeways and I'm very happy. Turns out Black Acrylic was rejected by the engineers there so i just went back to good old Frosted Ultra Detail and it did just fine for half the cost. Just $24 for both engines. 

 

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Guest Peterpools

Will be following with great interest, as anything Grumman is near and dear, as I'm life long Long Islander and lived maybe 20 minutes from the Bethpage plant.

:popcorn: :popcorn: :popcorn:

Peter

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Well then Peter you can certainly appreciate my weekend. Check out my visit  to the USS Yorktown and the haul of Grumman treasure there.  Have you ever made it there? 

 

Starting with the Wildcat: Fully resplendent and truly a lifetime favorite. Always good to see. 

 

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Then the Hellcat. Such detail in real life. Staggering complexity to it all, really. I do not think I've ever seen one in real life (and have been to Duxford, Smithsonian Air and Space (both Dulles  and Downtown) , the  US Air Force Museum and years of airshows)

 

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The I was stunned by the size of an Avenger. A true brute. Not sure scale models ever do it justice. Great to see! That's a first too. 

 

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Then I got not only see an F9F Cougar,  but actually sit in it. I could not  believe it. I'm such a fan. I could work the buttons on the stick and move it around which was a nice treat in this day and age. This is a great museum! (and the Yorktown itself is mind blowing even without the aircraft)

 

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Then up on the deck for a gorgeous Intruder

 

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and a beautiful Tracker complete with the same Wright R-1820s as the Skyrocket (though a little more modern version). There was also the rare EWACs Grumman Tracer but I did not get pictures (batts died!)

 

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And then the ultimate performance Grumman: 

 

The Tomcat:

 

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And for model enthusiast such as ourselves I was thrilled to see this (perhaps 1/9th scale??) Hellcat. Amazing attention to realism. 

 

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Other cool things but outside my scope of Grumman pics for this thread  was a Skyraider, a Dauntless, a Corsair, a Corsair II, an F8 Crusader, an S3 Viking (thought of you Ben "Starfighter"), an F-18 Hornet,  a very nice F-4J , a Stearman PT-17 and a B-25. 

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Ok, Back to our previously scheduled programming...

 

Tonight was cowl night on the computer. The work doing this with the Bearcat was rather trying as I did not know how to do this in 3D. Much trial and error.  Now I do so, it's actually pretty easy. I like the photo I had to attach within Fusion for a test/validation of the cowling opening size against the real thing.

 

I ordered two tonight.  :)  :) 

 

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Thanks Mark, (and I get your forum name now. I was thinking Dodgem like Dodgem cars (bumper cars) but I get it. Dodge M37...your little treasure.  :)

 

 

 Tonight was a bit of toil throwing 3D work  into the trashcan kind of thing,  but in the end I think I got just what I wanted: Two counter rotating Curtiss Electric props. To feather the prop there's  an electric motor in the small hub at the tip  and large reduction gears in the large hub. Power is supplied by brushs that contact slip rings on other side of the blades. More here with a nice vintage guide   http://www.enginehistory.org/Propellers/Curtiss/curtissprop.shtml . If you are curious and want to know more, well the starboard side has the "handed" propeller. Handed means it turns clockwise (from the pilots perspective). The port side has a "counter-handed" propeller . 

 

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Edited by Jim Barry
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