Rabid Models Grumman Skyrocket XF5-1 Twin Foamie Review

Albert Wahrhaftig explores the exciting new Skyrocket from Foamin at the Mouth Planes, by Rabid Models.

Ready for a mission from a secret schoolyard hidden in the far reaches of the Pacific Ocean.

Introduction

The Grumman Skyrocket on final approach
The Grumman Skyrocket on final approach
Wingspan:35 "
Wing Area:245 sq. in.
Weight:with 3 cell 1320ma. battery = 11.5oz.
Length:24.5"
Wing Loading:7 oz/sq. ft.
Servos:2 9 gm. or less
Battery:2 or 3 lipoly cells (3x1320 used in tests)
Motor:2 x LazerToyz 24 gm. brushless
ESC:2 x Castle Creations Phoenix 10
Manufacturer:Foamin' at the Mouth Models
Available From:Rabid Models

In a very small article in some magazine or another, I read about two guys putting together some interesting foam models under the name of Foamin' At the Mouth Planes by RabidModels.com. Now who is going to resist a name like that? Certainly not me. I googled them up and discovered that among their offering was a Grumman Skyrocket XF5-1. Oh joy!!! You can't imagine how quickly I bashed out an email asking to review that particular plane. And that is how what is apparently the first Skyrocket kit fell into my hands. Since it is the very first, and since I corresponded with the designer, Marc Stermer, about this and that during construction and initial flights, the kit you will receive may have some improvements over the one I will describe here.

History

But why such excitement over a Skyrocket? Well, don't we all have an airplane that has been a favorite since childhood? I do, and you have guessed what it is. I was 7 years old when my father presented me with what became my favorite book, the Air News Yearbook, edited by Phillip Andrews and published in 1942. I turned through its impressive 9" x 12" pages of photos over and over, always stopping to visit the Skykrocket at page 71. Take a look at the photos below and see if you don't get excited too!

The Skyrocket was indeed an extraordinary airplane. LDCR Crommelin, in charge of a 1941 fly-off against the Spitfire, Hurricane, P-40, P-39, XFL-1 Airabonita, F4F and F2A, wrote, "I remember testing the XF5F against the XF4U on a climb to the 10,000 foot level. I pulled away from the Corsair so fast I thought he was having engine trouble. The F5F was a carrier pilot's dream, as opposite rotating propellers eliminated all torque and you had no large engine up front to look around and see the LSO (landing signal officer)."

But there is more to my story than that. A comic book featuring the Blackhawks appeared in 1941 and continued in one iteration or another for fifty years. A squadron of do-gooder aviators consisting of pilots from countries overrun by the Japanese or the Nazis (one Frenchman, one Pole, one Chinese, etc.), the Blackhawks flew from a secret island base in the middle of the ocean to battle (even before Pearl Harbor) against the enemies of democracy, and what they flew with such daring and courage were Skyrockets. Yes, Skyrockets in their own distinctive Blackhawk colors. Take a look at them below.

Obviously, my RabidModels Skyhawk had to be a Blackhawk. You can find all the information you will need about these at http://ourworlds.topcities.com/blackhawk/models/f5fmark.html. Otherwise you can stick with Navy paint as shown on the kit's label.

The Kit

OK. Now what about the model?

Marc describes his Skyrocket, correctly, as a "high performance park flyer, designed with a scale profile and scale-size props. The kit is designed for someone who has at least some model building and flying experience. It is not an "Almost ready to fly" kit. The model is quite easy to fly. It is stable and maneuverable at low power, but it will accelerate and zoom vertical like a skyrocket when you pour on the power." The Skyrocket will fly realistically on 2 LiPo cells (I like it that way) and will make a Corsair look like it is standing still on 3 cells.

Kit Contents

Taking the Skyrocket as an example, I think Foamin' at the Mouth Planes are a great value. They are quite inexpensive and reflect some interesting efforts to keep costs low. Basically, the kit consists of fifteen Dow BlueCor foam parts and a few other bits and pieces. One way money is saved is in the control system. Using SpiderWire cable (supplied) knotted to dowel control horns, there is no hardware for them to supply or for you to buy. Another is that there is no paper instruction manual. Instead you receive a CD with a very extensive electronic, color-photo-illustrated manual and an additional file with USAAC markings and printable patterns for the cockpit.

Additional components needed:

  • A light weight receiver (but it doesn't have to be tiny)
  • Two servos, 9 grams or less
  • 2 10 amp ESCs or 1 20-25 amp ESC
  • 2 9x7 GWS three blade props
  • A 2 or 3 cell LiPo pack (the prototype used Thunder-Power 3x1320ma.)
  • 2 brushless "CD ROM" motors. My review model uses smooth running motors from LazerToyz
  • 2 prop savers to suit

Assembly

The first task is to use a paper towel moistened with acetone to lightly and carefully wipe the black marks off the surface of the foam parts. With a bit of delicacy, they will all come clean.

Wing

The wing is formed from three parts, a center and two tips. These are marked according to measurements given in the instructions, bent against a ruler or other straight edge, and then cut in half, separating fronts from backs. A carbon fiber spar is then epoxied between the front and rear half. The wing builds up into an undercambered airfoil, a feature shared by all the RabidModels designs.

I found epoxying the spar according to the kit instructions difficult and messy, but their system works for them and maybe it will work for you. After you read the kit instructions, consider my alternative and take your choice.

My alternative is to:

  • apply glue to the rear wing section and to one side of the spar
  • attach the spar to the rear of the wing, making sure that it is aligned with the TOP SIDE of the wing
  • pin the spar in place with ordinary straight pins
  • wait for the epoxy to cure.
  • remove the pins
  • put epoxy on the other side of the spar and on the front piece of the wing
  • attach the font part of the wing
  • use straight pins diagonally through the root and the tip plus a few pieces of tape to hold it until the epoxy sets.

I think this process will be much more controlled. I built "Blackhawk" their way, and built "#2" my way. The important point is, either way worked!

Skyrocket #2?????

Yes, my Blackhawk version of the Skyrocket was a victim of my dumb thumbs, so I built #2, a second Skyrocket in the original Navy colors. That's why the wings mysteriously change from yellow to red at the end of the video!

Back to wings

Next, I cut and hinge the ailerons, then epoxied the three wing panels together.

If you are going to paint your wing, this is a good time to do it.

IMPORTANT: Gluing to BlueCor Foam

BlueCor foam is covered with a thin plastic film on each side. Before gluing to any flat surface on this foam, the film must be stripped off. Use a ruler and ball pen to lightly mark the area where glue is to be applied. Use the ruler again and a very sharp hobby knife to gently cut through the film. You can then peel it off.

Fuselage

Profile and two sides - that's all there is to the fuselage. Glue them together and you're done.

Tail

The elevators was hinged to the stabilizer first. Then the stabilizer was scored and dihedral glued into it. (An option and a very good idea is to add a strip of filament tape longitudinally across the bottom of the stabilizer. I not only recommend this option; on #2 I added a strip of filament tape to the bottom of the wing.) Then the stabilizer was glued to the fuselage, jigging things up as necessary to ensure good alignment. When the glue was set, the rudders were added.

With the tail complete, I glued the wing to the fuselage.

Nacelles

Each nacelle consists of a profile and two sides, but before gluing them together, I thought through how to mount the motors. I could have used a stick mount or a radial mount; this was the time to decide which portions of the foam must be cut to fit the motor and mount.

Radio Installation

The Skyrocket carries two 9 gram or less servos in its nose. The ESC(s), receiver, and battery are all carried under the center panel of the wing. The Skyrocket can be flown with two 10 amp ESCs or one 25 amp ESC. I have used one ESC with no problem whatsoever on my Jinx, powered by two brushless motors, but on the Skyrocket I went with two 10 amp Castle Creations ESCs (which were generously supplied for this review and which have been entirely reliable). For a valuable source of advice, especially if you are using Castle Creations ESCs, log on to Castle's website and look for Issue #3 of their newsletter, The Castle Scribe, which contains Joe Ford's article on Brushless Multi-motor Power Systems. This article will tell you exactly how to program your ESCs for this application.

Completion

The last task remaining was installation of the control cables. The Skyrocket uses a system of 10# SpiderWire cable tied to servo arms at one end and to wood dowel control horns at the other. The instruction manual provides very complete step by step instructions for accomplishing this rather tedious task. At 71 years old and with considerable carpal tunnel shakiness, I find tying all these knots to get quite difficult. An alternative was to crimp the cables together using the tiny "crimp beads" that can be found at craft stores.

On Skyrocket #2, I tried a third technique and like it best. Using Dubro mini-connectors I installed all the necessary cables to the servo arms before placing the arms on the servos. Then I ran the cables through the various holes and tubes to the dowel control "horns" and tied them. With all the cables installed, I could then adjust them at the mini-connector. Let the young and nimble do it their way; the old and palsied will be better off with my way.

Once the cables were in place and adjusted, the other control system components were velcroed to the bottom of the wing central panel in locations dictated by adjusting the center of gravity to 1 1/2" behind the wing's leading edge. Don't cheat. The CG needs to be exact. You may have to add a bit of lead if you are using a two cell pack. If you are using a three cell pack, once you are thoroughly familiar with the Skyrocket's flying characteristics, you might cautiously move the CG back to 1 3/4".

"Don't cheat. The CG needs to be exact...1-1/2" behind the wing's leading edge."

By the time your read this, the instructions will specify control throws. If you already have your Skyrocket, set the ailerons at 3/8" up and down and the elevators at 1/2" up and down.. Dual rates will be nice with low rate being 70% of high. When you test the ailerons, don't be surprised if the whole wing twists a bit. Marc assures me that this is normal and will not adversely affect flight.

About propellors

The Skyrocket was designed to use GWS 9x7 three bladed props and brushless CD-Rom motor. With them it looks supercool, and clearly they work just right for him. My Lazertoyz motors are quite as stout as the ones that Marc used. With the 9x7 three bladers on my Blackhawk version as long as I did not got to full throttle everything was fine, but at the high end of the throttle it proved to be very overpropped and the motors got kind of wild.

I have been experimenting with Skyrocket #2. In the video it is flying on GWS 7x3.5 props. With these it is underproped. I intend to give 8x4 a try. Eventually I will find the optimum motor-propellor combination. When I do, I'll add a note to this review. Meanwhile, be prepared to experiment with your own choice of motor-prop combinations.

All done? Good. Let's fly.

Flying

Basics

Well chappies, you have a fighter plane on your hands, not a Piper Cub. The good news is that it IS a Skyrocket. Especially with 3 cells, it will climb vertically as long as you like and it looks great in the air. I enjoy flying it, and "Red" Jensen, my famous test pilot, got a kick out of it and thinks it is pretty sweet. However, it does have its limitations and its special characteristics. It will loop and it will roll, but it doesn't like to be inverted. Designer Marc Stermer attributes this to the under-cambered airfoil. And, because the thrust line is low, when power is increased it will climb. Prepare yourself for that and remember to add down elevator when you increase throttle. All in all, though, this is a fun and responsive airplane.

Taking Off and Landing

Marc Stermer has a Skyrocket with retracts. I have seen it take off on video, so feel free to add landing gear if that will make you happy. Since the kit does not include landing gear, it is normal to hand launch the Skyrocket. Launch at half throttle or perhaps a little less and with a small amount of up trim. All the Skyrocket needs is a gentle toss. Once you are used to the Skyrocket, start with a little more power and let it lift itself from your hand. When you are ready to land, bring the Skyrocket in under low power - it is not a great glider - and cut the power just before it touches down.

Aerobatics/Special Flight Performance

That is pretty much covered above. With three cells you have a very quick model, but one that can be slowed down. Its habit of flight is smooth and realistic. With two cells, the flight is more scale like and the plane scoots around just fine. Skyrockets had lots of firepower, so forget about 3D. Go look for an enemy and tear up the sky.

Is This For a Beginner?

No way, but if you are used to flying low wing planes with ailerons you will have a lot of fun with this one. Actually, although building the Skyrocket is not difficult and the instructions are extraordinarily clear and complete, this airplane is not for a first time builder either.

Flight Video/Photo Gallery

Downloads

Conclusion

The Rabid Models XF5F Grumman Skyrocket is a wonderful just-for-fun kit. Build it "scale" or build it like the Blackhawks flew it in their comic book, or build it like something out of your own imagination. Experiment with motor-prop combinations. You can even equip it with retracts. It isn't going to cost you much money, it will take a few hours to build, and it wants a pilot with low wing-aileron experience. If, when you fly it, at least one person doesn't exclaim "AWESOME!" I'll be much surprised. Get one and enjoy!

Last edited by wahrhaftig; Dec 08, 2006 at 02:58 PM..
Thread Tools
Dec 08, 2006, 07:42 PM
Registered User
makemcool's Avatar
Thanks for the memories! Although those memories are pretty sketchy, I do know as a kid just old enough to read in the early fifties, the Blackhawks were one of my favorite comics. The battle cry...HAWKAAA, is well remembered, even though it never occured to me that they flew Skyrockets. It really is a plane that deserves to be modeled more.
Dec 09, 2006, 10:42 AM
Still AWD, Subaru
such a cool aircraft in reality, and for a profile it looks great as a model!
Thanks for sharing.
Dec 09, 2006, 05:35 PM
Random Flier
Nice review, and kudos to Rabid Models for modeling a rare beast!

One of my favorites is the Westland Whirlwind, a contemporary UK single-seat twin. In-lines rather than radials, and the twin tail converted to a single tail before it flew...
Dec 16, 2006, 01:59 PM
Registered User
themudduck's Avatar

SKyrocket motors


I thought I would add: the LENS motors that I have been using with the GWS 9x7 props are virtually identical to the Westport 25-turn CD-rom motor that's offered by the folks at Model Airplane Engineering (m-a-e.com).
CD-rom motors with fewer turns won't be able to handle this prop. There are probably other brushless motors that would work well, but the key is to find one that's not too heavy (the Westport motor only weighs 18 grams!).
Thanks for the terrific review and I am glad that you like this model! We have more coming. --- Marc at RabidModels.com


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Cool Rabid Models Demo Day at Sagamore 7/1 kdahlhaus North Coast Electric Flyers 12 Jul 02, 2007 11:18 PM
Article Foamy Factory Models' 3DX Mini 3D Foamie Review Navy Diver 3D Foamies 1 Sep 05, 2005 10:54 PM
Grumman Skyrocket Foamie tiggs Scale Kit/Scratch Built 12 Aug 22, 2004 10:03 PM
Viper Twin 2 review MattLarson29 Foamies (Kits) 23 Aug 25, 2002 07:45 PM
Dave's Aircraft Works TG-3 and 1-26 Foamie Gliders for beginner?? Bellavance Electric Sailplanes 12 Oct 17, 2001 09:06 AM