I have been asked by many if the Balsa USA or Sig cub are true scale. The answer is not true scale but close. Both have issues and we will talk about that below.
I have spent several hours taking the full-scale prints and putting them into AutoCAD so I could scale them down. Before you ask, yes, I did sale my plans and I’m currently looking for a new printing source. I will not give them out as PDF or any other file format.
Overall size comparison
| Full Scale | ¼ Scale Cub | SIG Cub | Balsa USA Cub | |
| Wing Span | 35’ 2.5 | 105.625 | 105 | 108 |
| Wing Chord | 5’ 3 | 15.75 | 16 | 16 |
| Length | 22’ 4.5 | 67.125 | 67 | 68 |
As you see above they are not exact but close. Below on all the photos the white lines are from the sig or Balsa USA plans. The purple lines are from my plans. When I say both I’m referring to both Balsa USA and Sig Plans
Let’s start with he wing. Both do not have true scale wing rib locations. This mainly because of easy of building. Both do not have the front short ribs as the full scale has. Both have ailerons that are hinged on the top and not close to scale. The full size has the hinge line on the bottom and back from the leading edge.
For the Balsa USA cub you will see how the wing is longer. Also, the tip bow follows the outline close except for the back end. The Aileron extend farther out into the bow then the full scale. Jury strut attachment point is farther out the wing then true scale.
For the Sig cub you will see the wing is a little longer. Also, the tip bow follows the outline close except for the back end. The Aileron is very close to full scale. For the jury strut and main struts are very close to attachment points of full scale.
Wing ribs. The wing chord is a little longer on both cubs then scale.
For the Balsa USA it has a thicker front section, but after the high point it follows the scale outline
For the Sig its thinner in the front and fatter in the back.
Tail surface.
For the Balsa USA you can see how the plans are larger than the true scale. Its wider from side to side and a little deeper. The front leading edge is a little fatter than true outline.
The SIG is closer to outline but not as wide from side to side.
Fuselage. Again as in the wing the bracing and supports do not match full scale.
Fuselage from the side. I line this one up with the tail post. So, you can see how the overall length is.
On the Balsa USA you can see they have the rudder larger than true scale. You will also see were its longer than scale. The fuselage is also taller than scale. The back deck is close to scale
On the SIG the ruder is very close to true scale. The back deck is much smaller than scale. You will see that the sig cub is a little shorter on the drawing. For the overall height, it is very close.
Fuselage from the top. I line this one up with the tail post. So, you can see how the overall length is.
For the Balsa USA you will see it is wider then scale. As you see more in the front area that it is much wider than scale.
For the sig, the back section is wider than scale. The front area is just a hair smaller than scale.
So with all the above said. I would say the SIG is closer to scale.
The Build
Now let’s look at the build.
At one time many moons back, the SIG had some thicker parts that had to be cut out, but now days all parts are stamped, or laser cut ready to pop out. Both kits also have a lot of sticks to cut and build the fuselage. If you don’t like cutting a lot of angles and fitting sticks, then this kit might not be for you.
The Balsa USA has the option for an opening door and window. This can also be added to the Sig version. I have a page on this site for this mod to the sig cub.
The Balsa USA cub has both wings that plug into the center section by a front and back locating dowls. Then install a few screws. This can be a small challenge as you are holding the wing and installing the screws at the same time.
The Sig cub has the center section made onto one side of the wing, so it attached to the fuselage by a dowls in the front and two bolts in the back. The second half of the wing slides onto a finger from the center section.
I own and fly a Sig cub, I have flown the Balsa USA cub. I will say they both fly great, and I could not tell any difference in them.
I hope you find this page informal on the outline.
Feel free to reach out to me with questions.
