I am not certain if I should ask this question here or on the design forum. Here, I hope, as it is a 4130CrMo structure question.
For this exercise, I am thinking of building a Cub derivative design. To save a little money on the tubing an idea struck me. In the early days Piper used some non 4130 in their airframes, quite a lot if I recall.
So, here is my thinking. Elsewhere on the forum I read that the biggest reason to use 4130 was for behavior in a crash. The difference in weight of a fuselage properly designed with 4130 and properly designed for softer common steels is minimal for bearing the normal loads. The difference is mostly in crash behavior.
Assuming that I want to save a bit of money, where should I use the 4130? I do not want the engine in my lap in a nose over so forward of the door post it should not get the 1010 treatment. I do not want the cabin to collapse on me so a lot of 4130 used there. Aft of the rear seat or aft of the baggage area maybe not to worry, so 1010 or some such for savings there. I can see some ways that it might be better to have the aft section be a bit softer part, buckling and twisting as this absorbs energy might be the ticket in a crash.
The door frame on a Dutch door would seem to be a waste of 4130. Mostly it is fabric and so will not stop a puncture, a tree branch or some such, any more than a 1010 frame or one made out of old bicycle frame tubes. Do you need a stick made from 4130? Rudder peddles? Do you need to make the seat frames from 4130. Maybe something that would bend a bit would be better?
I have saved up a few bicycle frames as I was planning a little scooter project. Maybe there are some nonstructural places to use that tubing? Lots of bicycle frames at the curb on spring cleanup day in this town, and there is always Craig’s list. As I recall some of those racing bicycle frames were light weight and rather strong.
Can a little scrounging along these lines save enough to make it worth the effort and not effect the final product? It's basically all custom anyway so being able to get Cub parts to interchange is not so high on my list.
Comments greedily accepted!
Cabover
For this exercise, I am thinking of building a Cub derivative design. To save a little money on the tubing an idea struck me. In the early days Piper used some non 4130 in their airframes, quite a lot if I recall.
So, here is my thinking. Elsewhere on the forum I read that the biggest reason to use 4130 was for behavior in a crash. The difference in weight of a fuselage properly designed with 4130 and properly designed for softer common steels is minimal for bearing the normal loads. The difference is mostly in crash behavior.
Assuming that I want to save a bit of money, where should I use the 4130? I do not want the engine in my lap in a nose over so forward of the door post it should not get the 1010 treatment. I do not want the cabin to collapse on me so a lot of 4130 used there. Aft of the rear seat or aft of the baggage area maybe not to worry, so 1010 or some such for savings there. I can see some ways that it might be better to have the aft section be a bit softer part, buckling and twisting as this absorbs energy might be the ticket in a crash.
The door frame on a Dutch door would seem to be a waste of 4130. Mostly it is fabric and so will not stop a puncture, a tree branch or some such, any more than a 1010 frame or one made out of old bicycle frame tubes. Do you need a stick made from 4130? Rudder peddles? Do you need to make the seat frames from 4130. Maybe something that would bend a bit would be better?
I have saved up a few bicycle frames as I was planning a little scooter project. Maybe there are some nonstructural places to use that tubing? Lots of bicycle frames at the curb on spring cleanup day in this town, and there is always Craig’s list. As I recall some of those racing bicycle frames were light weight and rather strong.
Can a little scrounging along these lines save enough to make it worth the effort and not effect the final product? It's basically all custom anyway so being able to get Cub parts to interchange is not so high on my list.
Comments greedily accepted!
Cabover
