Shulman's Skyrocket
03-21-2007, 11:34 AM
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Shulman's Skyrocket
Although I love to work with balsa I have been envious of the apparent simplicity of building flat
foam models. When I saw Leon Shulman's redesign of his championship 1939 freeflight model,
the Skyrocket, in the May 2005 issue of Flying Models, I decided to give it a try. A friend provided
the blue fanfold foam and I started hacking away. Amazingly, in two weeks I had a plane built
from scratch and set to fly.
The wood parts are ply doublers at the nose and motor mount, the landing gear socket, and
strips on the top and bottom edges of the fuselage. These strips were easily attached using
UHU "Creativ" contact cement from a crafts store. The camber of the wing is made by simply
creasing parallel lines with a clamped straightedge on the underside of the wing.
Power is by an Eflite 370-1200 motor running on two 910mah Lipos. Two HiTec S55 servos and
an FMA M5-V2 receiver with an Azarr antenna are for guidance. Wingspan is 36" and total
weight is 9.7 ounces. Test flights will wait until our field dries out.
Another of Shulman's designs, the Zoomer, is in the November 2006 issue of Model Aviation.
foam models. When I saw Leon Shulman's redesign of his championship 1939 freeflight model,
the Skyrocket, in the May 2005 issue of Flying Models, I decided to give it a try. A friend provided
the blue fanfold foam and I started hacking away. Amazingly, in two weeks I had a plane built
from scratch and set to fly.
The wood parts are ply doublers at the nose and motor mount, the landing gear socket, and
strips on the top and bottom edges of the fuselage. These strips were easily attached using
UHU "Creativ" contact cement from a crafts store. The camber of the wing is made by simply
creasing parallel lines with a clamped straightedge on the underside of the wing.
Power is by an Eflite 370-1200 motor running on two 910mah Lipos. Two HiTec S55 servos and
an FMA M5-V2 receiver with an Azarr antenna are for guidance. Wingspan is 36" and total
weight is 9.7 ounces. Test flights will wait until our field dries out.
Another of Shulman's designs, the Zoomer, is in the November 2006 issue of Model Aviation.
05-04-2007, 09:28 AM
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RE: Shulman's Skyrocket
Time for an after action report.
The Skyrocket lived up to its name going vertical on 2/3 throttle. But the wing was bending alarmingly and on the third flight it broke next to the central dihedral joint. The plan suggested reinforcing tape on the wing only as an option for "strong thermals". It wasn't the thermals that got me but the climb phase. I will make a new wing and use two strips of nylon filament strapping tape on the underside this time.
As a confirmed balsa-butcher I was concerned about the lack of torsional stiffnes at the aft end of the fuselage. I have since been told that tail floppiness is a characteristic of flat foamies. I will probably add some foam pieces to the back of the fuselage to make it into a diamond shape to make it more rigid.
The Skyrocket lived up to its name going vertical on 2/3 throttle. But the wing was bending alarmingly and on the third flight it broke next to the central dihedral joint. The plan suggested reinforcing tape on the wing only as an option for "strong thermals". It wasn't the thermals that got me but the climb phase. I will make a new wing and use two strips of nylon filament strapping tape on the underside this time.
As a confirmed balsa-butcher I was concerned about the lack of torsional stiffnes at the aft end of the fuselage. I have since been told that tail floppiness is a characteristic of flat foamies. I will probably add some foam pieces to the back of the fuselage to make it into a diamond shape to make it more rigid.
05-05-2007, 08:54 AM
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RE: Shulman's Skyrocket
Nice Build!
I too am a old balsa dust maker that has converted over to foam. To help some with the stab floppiness I put a 1/8 square hard balsa spar on the hinge line of the stab, both vertical and horizontal and use packing tape for the hinge. Also if the wing is too floppy I will put one on the leading edge and sand it half round, adds a lot of strength. I also put a couple of strips of strapping tape on the underside of the wing, one strip at the spar position and one at the TE.
I'll bet with that 370 it will go straight up. Before I retired several years ago I stocked up on brushed type motors so have to use them up, but I have a couple of cdrom motors that I also use.
Also found some Locktite "Sumo" glue a couple of weeks ago, great stuff for foam. Dries kind-of milky white to clear and doesnt foam as much as Gorilla type glues and dries faster also. Try it if you can find it in your area!!!
Happy flying
Bob
I too am a old balsa dust maker that has converted over to foam. To help some with the stab floppiness I put a 1/8 square hard balsa spar on the hinge line of the stab, both vertical and horizontal and use packing tape for the hinge. Also if the wing is too floppy I will put one on the leading edge and sand it half round, adds a lot of strength. I also put a couple of strips of strapping tape on the underside of the wing, one strip at the spar position and one at the TE.
I'll bet with that 370 it will go straight up. Before I retired several years ago I stocked up on brushed type motors so have to use them up, but I have a couple of cdrom motors that I also use.
Also found some Locktite "Sumo" glue a couple of weeks ago, great stuff for foam. Dries kind-of milky white to clear and doesnt foam as much as Gorilla type glues and dries faster also. Try it if you can find it in your area!!!
Happy flying
Bob
