Skybolt (oz7537)


Skybolt (oz7537) by Claude McCullough 1975 - plan thumbnail

About this Plan

Sig Skybolt. Radio control scale model of the homebuilt Steen Skybolt, for .45 - .60 power. Discontinued kit from SIG.

Quote: "LaMar Steen's homebuilt Skybolt is not only a great looking airplane but a practical design as well. There are no machined parts and a welding torch and ordinary shop tools are sufficient to construct it. The prototype was built by LaMar's students in the Aerospace program at Manual High School in Denver - a fact which will help clarify the lettering on the decal in this kit.

Full symmetrical wing sections are used to aid aerobatic characteristics and the structure is stressed for 9 G's plus and 8 G's negative. The top wing span is 24 feet and the lower span is 23 feet. One quality that has made it so popular is the reasonable size of the cockpits. An information pack on the Steen Skybolt with 3-view can be obtained for $2.00 from Steen Aero Lab, Inc., 15623 DeGaulle Circle, Brighton, Colorado 80601.

ABOUT THE MODEL Our version of the Skybolt was designed with easy building and good model flight characteristics in mind and the exact scale outlines have been modified. It is primarily intended for the NSPA-AMA biplane stunt event and for sport flying. However it can be used for Sport Scale events if desired. In this connection it should be noted that the available 3-view is not quite like the actual airplane in that a different shape and style of cowling is shown so it is recommended that pictures alone be used as a scale presentation for judging. AMA Sport Scale rules do not require a 3-view for competition - photos only may be used if desired.

It's common with homebuilt's for some component shapes to vary from plane to plane depending on how the individual builders happened to bend the tubing. The tail surfaces on Skybolts are an example of this artistic expression. We used the general shape shown on the Steen three-view and if you wish to emphasize the Sportt Scale aspect, be sure and check photos of the particular Skybolt example being copied for exact shape.

The color scheme of the model was taken from the markings of LaMar's airplane as it, was originally painted. He has since redone it in a more complex pattern with air brushed edges between the colors, while his first version needed only masking tape.

Hale Wallace painted his Skybolt pre-production model like his full-size Skybolt. This is a colorful arrangement but requires more masking to reproduce the checkerboarded under-surfaces. An alternate decal is available with stars, license numbers and the Sky-bolt name for the cowl to duplicate his airplane.

Hale used a more elaborately shaped cowling on his Skybolt, as have some other home builders of the design. The fairing behind the spinner and the lower scoop can be made from balsa. Glue balsa to the cowling plastic with Sig-Ment. Paint the balsa parts with Sig Sanding Sealer to fill the wood grain.

Single or Double Ailerons? The original model used single ailerons on the lower wing to keep the linkages to the servo simple. The installation was very effective, gave good response and as rapid a roll rate as desired. The complications of hooking up the double ailerons are not worth the trouble for sport fliers the single ailerons are more than adequate. As a matter of fact, the single aileron set up can give a good account of itself at a contest. For high level competition and expert fliers the double ailerons will probably be desired. They provide max-imum control leverage and a very rapid roll rate for performing complicated free-style maneuvers.

Muffler Installation. Large chamber type mufflers should be located completely outside the cowl on an extension pipe. The Du Bro Muff-L-Aire or similar stack-type mufflers have a neater appearance. These work well if the plates are taken off and varnish and carbon cleaned away occasionally..."

This good scan was posted up on the HPA site by Cavaliere. I took that scan and spent maybe 2 hours cleaning it up, removed all the background noise, removed the paper creases, also darkened the ink lines slightly for better clarity, too.

See RCGroups thread here for more info on the old SIG kit.

Update 18/03/2016: Added extra sheet showing hand-traced parts, thanks to mjb.

Update 23/06/2018: added build manual, thanks to GT.

Supplementary file notes

Sheet showing hand traced parts (tailplane outline and interplane struts).


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Skybolt (oz7537) by Claude McCullough 1975 - model pic


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Skybolt (oz7537) by Claude McCullough 1975 - pic 003.jpg
Skybolt (oz7537) by Claude McCullough 1975 - pic 004.jpg
Skybolt (oz7537) by Claude McCullough 1975 - pic 005.jpg
Skybolt (oz7537) by Claude McCullough 1975 - pic 006.jpg

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User comments

I'm not seeing the horz stab. Could a second page be missing?
anon - 16/03/2016
Good point. Looking at the fuselage side view, the horizontal stab is shown as just constant thickness balsa sheet. I guess since this was a kit plan, maybe that part was completely prefabricated and needed no further drawings (as far as assembly instructions went). But if anyone out there does have an outline of the horiz stab, that would be great.
SteveWMD - 16/03/2016
Hi Steve; I built the kit some years ago. Great flying airplane, but unfortunately was lost due to a radio failure, much too soon in its life! I traced the stab and interplane struts on the back of my plan 'just in case'. They are solid 1/4 inch sheet. Here are scans of them but I have not stitched them together yet. The fuselage top was a plastic moulded piece, so anyone scratchbuilding will have to create a set of formers and strip planking to match the outlines shown on the plans.
mjb - 18/03/2016
Hi Steve; Here are 2 pics of my Sig Skybolt built from the kit and finished in Monokote with the kit design layout [more pics 003, 004]. It was a great looking and flying model. Maybe I should rebuild?
mjb - 05/04/2016
Looks great! Rebuild, definitely.
SteveWMD - 05/04/2016
Vintage photo thanks to Andy Coutts [more pics 005].
Mary - 31/03/2017
Nice plane. It is a comfortable wing span I like to build and fly. Is there any way to purchase a set of plans along with the assembly instructions. Thank you
MF Bush - 31/10/2019
Start by reading the FAQ page at
SteveWMD - 31/10/2019
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Download File(s):
  • Skybolt (oz7537)
  • Plan File Filesize: 1901KB Filename: Skybolt_SIG_51in_oz7537.pdf
  • Supplement Filesize: 7428KB Filename: Skybolt_SIG_51in_oz7537_manual.pdf
  • Supplement Filesize: 45KB Filename: Skybolt_SIG_51in_oz7537_parts.pdf
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