What is the best design to stack wings of a triplane? I would like to design an ultralight airplane, which probably the total mass will be around 400kg. The speed should not exceed 200km/h. Forget about what the engine I will use. I intend it can land and take off in a small road and/or in a common road, which the road line not more than 2.5m each direction. If I have to occupy both direction, mean the road width is just around 5m, plus small space beside the road in both side. Beside the road, normally many electrical poles. So, not many space available.

To tackle the situation, I need to change wings design without reduce the wing area (A in m2). Was discussed earlier here some of the triplanes that were used during the WWII. If they were used during the war, that mean that such design was safe enough. But, I have a bit confusion regarding how to place the wings' stack? Here are the three options design.


The wings stack are lean to the tail.
The wings are stacked exactly over another.
The wings are lean to the nose.


Another thing. We know that the closer wing to the ground will produce what is called earth deflection (CMIIW about the terminology) during take off. That will make the plane requires longer time to take off. In my opinion, the same effect will occur if we stack the wings too closed one to another, especially if the wings are stacked lean to the nose, the deflection will hit the lower trailing edge if there is no enough space. So what is the best design in this case? And what is the best space?
Wing stagger was mostly chosen to improve pilot vision: In single-seaters, a positive stagger would allow to place the upper wing ahead of the pilot, improving the field of view.

Large bi- and triplanes had no stagger. Here the pilot sits ahead of the wing and large aircraft fly mostly straight, reducing the need for the pilot to observe the airspace around him.

However, if you look for a proven design of a very compact triplane, I would like to suggest the Italian Pensuti triplane. It had a wingspan of only 4 meters and a total weight of just 230 kg. Emilio Pensuti, a test pilot with Caproni during WW I, designed it as an easy to fly aircraft for the common man. Therefore, it is sometimes also called the Caproni-Pensuti triplane. The first version was powered by a 35 HP Anzani engine while a later development, the Breda-Pensuti 2, used a 80 HP engine.

Of course, its wings had no stagger.



Drawing of the Pensuti triplane (picture source). Yes, it did fly!



Pensuti triplane in flight (picture source)

If you build one, I would strongly suggest to change the wing airfoil to a thicker one with the same amount of camber.