Grumman Skyrocket (oz8911)
About this Plan
Grumman Skyrocket. Stand-off scale RC model twin.
Quote: "The Grumman XF5F-1 Skyrocket was a radical approach in the development of Navy air power. Orders were issued in June, 1938 for this new twin engined shipboard fighter. This at a time whe: biplanes were the king of the fleet and monoplanes were just coming into use.
It was first flown on April 1, 1940. Performance was good, but cooling and airflow problems led the way to a long series of development modifications. An extended nose, fillets and nacelle improvements were made. Landing gear failures added to development problems. The Skyrocket was written off in December, 1944 after a landing gear failure at Floyd Bennet Field in New York.
Wing span was 42 feet, top speed 383 mph and a rate of climb of 4,000 feet per minute, which probably attributes to the name Skyrocket. While only one XF5F-1 was built, the development work on it paved the way for the very successful F7F Tigercat.
The Skyrocket is the type of plane you either like or you don't. Its unique snub nose, or rather no nose appearance and big radial engines is either appealing or appalling, depending on your taste. I have always been intrigued by this airplane and decided it was time to build one. I sized it to suit a pair of Wankel .30's, however any good reliable pair of .29 to .40 engines would do the job. The span is 58in and wing area totals 585 square inches.
Ready to go my Skyrocket weighs 9 pounds, giving a wing loading of about 35 ounces per square foot. This is kind of heavy loading for a sport flier, but the Skyrocket was not built for everyday pleasure flying. A complex twin engine model just can't be considered a sport plane. Ample power, a well forward center of gravity and a generous amount of wash-out in the wing tips all help to make the Skyrocket perform reliably.
Dependable engines are of the utmost importance! The engines are quite far apart, although the absence of a nose make them look even wider spaced than they are. Add to this the large cowls with their resultant high drag and it isn't hard to imagine the single engine performance. In a word, risky, a trait not unique to the Skyrocket alone. I have not seen a scale twin engine model other than those with tandem, push-pull, engines that was not in trouble to some degree when an engine quit. An exception might be some flying boats such as the Catalina.
Pointing the engines outward, about 3 or 4 degrees, can help. I didn't do this on my model, but if you build it you may want to.
I went all out and included flaps and retractable landing gear. Rhom Retracts were used with excellent results and this system must be one of the most reliable available. The Rhom main gears can be made to retract back by simply rotating the legs 90 degrees and mounting them as you would a nose gear..."
Direct submission to Outerzone.
Article pages, thanks to RFJ.
Supplementary file notes
Article pages, thanks to RFJ.
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(oz8911)
Grumman Skyrocket
by Nick Ziroli
from Flying Models
October 1975
58in span
Scale IC R/C Multi Military
clean :)
all formers complete :)
got article :) -
Submitted: 01/07/2017
Filesize: 1003KB
Format: • PDFbitmap
Credit*: Circlip, RFJ
Downloads: 1946
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User comments
I thought I'd try to make an electric conversion but looking the plan over, and having already made several other electric conversions, I'm concerned about battery placement to get the CG correct. In my other conversions I've found that my electric motor(s) end up making the plane quite a bit lighter forward than with gas engines, making the proper CG possible only by having the battery very far foward, much more forward than in the average Lipo electric model. I can see that with the snub-nose there isn't a forward fuselage at all to place a battery, so it will probably need to be placed aft of CG making the need to add lots of lead weight under the wing forward to get the CG correct. As the author wrote, this plane has a fairly heavy wing load already so I hesitate to add the extra weight. The only other option is to split the battery into two packs and place one each under or just behind the motors, something I had to do with a P38 Lightening electric conversion. It worked, but was very cumbersome to set up to say the least. Any comments, suggestions?Sal - 01/01/2020
I'm guessing you'll really need the weight up front, as far forward as possible - which will indeed mean using two lipos, one in each nacelle. Can't see any other way, to be honest.
SteveWMD - 01/01/2020
Bit of lateral thinking, I would look at making the engine cowls heavy. Build them from heavy wood. Cover them in fiberglass. Cast some fake engines with epoxy mixed with metal powder (or get some hollow 3D printed cylinders and fill them).
If you can't move the heavy bits forward then make the forward parts heavier.
Could the battery fit in the wing LE?
Could you lighten the tail?
M Hodgson - 02/01/2020
Just finished an electric version of Ziroli skyrocket. I used to 25 size electric motors was to 3000 mA 14.8 V batteries mounted partially in the cowl and part in the nacelle. Model balanced real nice with about 8 ounces of lead underneath the motor. Flying weight is a shade under 8 pounds if you're interested I could email you some pictures and also the canopy is available from Nick Ziroli Jr.
Remy Haynes - 01/04/2020
Yes please, we'd love to see some pics.
SteveWMD - 01/04/2020
Greetings, The Skyrocket was modified over time with an extended nose. You would lose the snubbed nose we all love, but it would solve the weight and balance problem. Grumman also built a tricycle gear version for the US Army, the XP-50. OZ has a plan, listed as a P-50, by Paul Plecan. This aircraft gave Grumman experience they used to design the F7F Tigercat. Let’s be careful out there.
James Hickman - 02/04/2020
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- Grumman Skyrocket (oz8911)
- Plan File Filesize: 1003KB Filename: Grumman_Skyrocket_58in_oz8911.pdf
- Supplement Filesize: 2533KB Filename: Grumman_Skyrocket_58in_oz8911_article.pdf
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