oriol
Well-Known Member
Hi!
While learning about structures, I have sketched a fuselage design. It goes without saying that I love classics. It is only a random design. If possible it would be nice to use a Corsair parafan engine, and stay below the 70 kgs limit, the deregulated class in Europe. Achieving that represents a major engineering challenge by itself.
I would like to cover the tail with dacron. The engine cowl might be made of aluminium or composites, the doors would be aluminium. This is just a sketch without any numbers. Judging by other ultralights perhaps usin one mm thicknes 20 mm tubes would be good enough. Roughly speaking, wingspan would be around 10 m and length half.
Beyond the numbers, what intrigues me are some conceptual considerations.
What is particular of the design, is the idea of slightly bending the upper and lower corners tubes of the tail; something like a 10 or 8 m radius would suffice. The bottom of the fuse would look flat from the side. That is the corners tubes would be like two parentheses ( ). On the other hand the two tubes on the corner above, would be placed at 45 degrees or so; those would look curved from top and side.
That way the airplane, without being a composite aircraft, would look a bit fish like, and not too boxy. OTOH I like that, if possible, the same tube goes from the firewall to the tail. The aircraft silouette reminds a Fairchild 24. However like many similar fuselages, the Fairchild has a curved wood structure on top of the tail, to reduce weight and improve aerodynamics.
Of course the goal is to achieve a sturdy and light fuselage. That is to triangulate everything. The biggest challenge seems to be the cabin, in where there has to be an easy acces for the pilot.
Since this is a single seater, I do not know if to reinforce one side of the cabin; only one door on one side. I personally prefer symmetric structures. It also might be convenient to have two doors, in case of crash?
It is not obvious to tell from the drawing; the stabilator would be strutted. It is always about trade offs, and I prefer everything reinforced as much as possible. The stabilator would be high enough to avoid shadowing the tail rudder. The wing has two struts, there is one reinforcement missing in the drawing, it goes from the strut to the tip of the first triangle at the tail.
I searched the web for inspiration. I found this fuselage below, which looks very nice and light. However, I dislike a bit the stress concentration at the tail; when the two upper tubes become one. One other thing that strikes me, is the lack of reinforcements in the cabin? If the numbers look fine, perhaps this is justified? Even so, I would reinforce the cabin sides with six more tubes, at 45 degrees on each corner of the sides. I do not know if the stab, is connected to the vertical stabilizer with cables or struts?
The lack of reinforcements on the cabin sides, seems to be a trend on many tubular fuselages I see.
Another very nice tubular fuselage is the one below (a Wagabond?). They too, like the Piper Cub, do not connect the upper part of the tail with the cabin with tubes to save weight. The lower part of the cabin is reinforced like above but, the top is not? It seems to be a bit tight to enter, so perhaps this is more justified. But still it looks counterintuitive to me. Even if considering that those aircrafts, are not intended for aerobatics, and the wings are strutted. The wing is still attached to the top of the cabin.
I would appreciatte any comments!
Fly safe,
Oriol
While learning about structures, I have sketched a fuselage design. It goes without saying that I love classics. It is only a random design. If possible it would be nice to use a Corsair parafan engine, and stay below the 70 kgs limit, the deregulated class in Europe. Achieving that represents a major engineering challenge by itself.
I would like to cover the tail with dacron. The engine cowl might be made of aluminium or composites, the doors would be aluminium. This is just a sketch without any numbers. Judging by other ultralights perhaps usin one mm thicknes 20 mm tubes would be good enough. Roughly speaking, wingspan would be around 10 m and length half.
Beyond the numbers, what intrigues me are some conceptual considerations.
What is particular of the design, is the idea of slightly bending the upper and lower corners tubes of the tail; something like a 10 or 8 m radius would suffice. The bottom of the fuse would look flat from the side. That is the corners tubes would be like two parentheses ( ). On the other hand the two tubes on the corner above, would be placed at 45 degrees or so; those would look curved from top and side.
That way the airplane, without being a composite aircraft, would look a bit fish like, and not too boxy. OTOH I like that, if possible, the same tube goes from the firewall to the tail. The aircraft silouette reminds a Fairchild 24. However like many similar fuselages, the Fairchild has a curved wood structure on top of the tail, to reduce weight and improve aerodynamics.
Of course the goal is to achieve a sturdy and light fuselage. That is to triangulate everything. The biggest challenge seems to be the cabin, in where there has to be an easy acces for the pilot.
Since this is a single seater, I do not know if to reinforce one side of the cabin; only one door on one side. I personally prefer symmetric structures. It also might be convenient to have two doors, in case of crash?
It is not obvious to tell from the drawing; the stabilator would be strutted. It is always about trade offs, and I prefer everything reinforced as much as possible. The stabilator would be high enough to avoid shadowing the tail rudder. The wing has two struts, there is one reinforcement missing in the drawing, it goes from the strut to the tip of the first triangle at the tail.
I searched the web for inspiration. I found this fuselage below, which looks very nice and light. However, I dislike a bit the stress concentration at the tail; when the two upper tubes become one. One other thing that strikes me, is the lack of reinforcements in the cabin? If the numbers look fine, perhaps this is justified? Even so, I would reinforce the cabin sides with six more tubes, at 45 degrees on each corner of the sides. I do not know if the stab, is connected to the vertical stabilizer with cables or struts?
The lack of reinforcements on the cabin sides, seems to be a trend on many tubular fuselages I see.
Another very nice tubular fuselage is the one below (a Wagabond?). They too, like the Piper Cub, do not connect the upper part of the tail with the cabin with tubes to save weight. The lower part of the cabin is reinforced like above but, the top is not? It seems to be a bit tight to enter, so perhaps this is more justified. But still it looks counterintuitive to me. Even if considering that those aircrafts, are not intended for aerobatics, and the wings are strutted. The wing is still attached to the top of the cabin.
I would appreciatte any comments!
Fly safe,
Oriol
Last edited:
