TT: Yeah, don't dis me because I didn't engineer my bolt together kit plane. I'm not an engineer, but I can follow instructions. I'm not the best pilot, but I love to fly. Share your progress or don't. I'd be interested in following along if you do.

Hi Trimtab
I am really interested in how you progress. I have a c-175 that I got approved into the amateur system just before they closed the door, so to speak. I am installing a chevy ls3 in this project. I also have been told of 2 more Seabees and a 182 that have applied for amateur under the new system in Canada. If we can find a way to work in the system we can make real planes out of these old aircraft.
KenW

SV:
I don't want to "dis" anyone. I'll be happy to periodically update people in the details if they are curious.

As it is, I've drilled the top off of one wing and modeled a bit of the structure. One thing is for sure: there is not a lot more to a Cessna wing than most aluminum light plane wings I've seen. But it has become clear that every portion of the structure was designed very carefully and simply.

So far, the ultimate load appears to be around 15,000 lbs (7500 per wing). That means that at roughly 2500 lbs of 182 (2800 minus the weight of the wings), the ultimate load factor at full gross places the structure squarely in the normal category: 2500 lbs * 3.8g's * 1.5x safety factor is about 14250 lbs. The utility category might require 16500 lbs. This was calculated by calculating the section moduli, using known and assumed aluminum properties, and modeling the wing load by area, hinged attach points at the root, and the attach point at the strut with the correct geometry. The wing would appear to be designed to fail outboard of the strut under a positive load, assuming the lower strut fitting did not fail. The areas near the joints are pretty elaborate in a couple of places.

Incidentally, there is a reason the wing strut is placed where it is on the wing: as it moves out, the linear stress goes down and the design load factor goes up as the attach point moves even several inches outwards. However, the compression loads on the inner portion of the spar rise fairly quickly, leading to a buckling instability. The location of the strut appears to be within inches of the optimal location for maximum load bearing capabilities for the angle of the strut and design of the section moduli at the joints. Some folks really did put some thought into that back in the post-WW2 Cessna days.

In any case, I need to go through this carefully since my own design will meet or exceed these numbers. It makes me humble to think that someone used similar principles to design the strut-less Cessnas...

Cool stuff! I so miss doing real stress calculations. I'd love to have a good job doing that kind of engineering.

TT: Good deal. My eyes may glaze over and I may drool a bit if you talk heavy engineering but I am interested in your build. I've built two airplanes and it's always interesting to see what the other guy does.

Trim Tab wrote:SV:


In any case, I need to go through this carefully since my own design will meet or exceed these numbers. It makes me humble to think that someone used similar principles to design the strut-less Cessnas...

And they did it using slide rules, a calculator and real human brain...

Has any progress ever been made on this? Or did it die a slow death?

It seems obvious that installing a set of used 182 wings and/or tail would be far less expensive and difficult. Surely a hell of a lot cheaper than having a DAR take you through the whole EXP certification process.

Why is this (major repair / return to service / used Cessna parts) not one of your choices?

Looks like the poster never went any further than posting a topic and then disappearing 4 years ago.....