http://a360.co/1QoKKpV
A sketch of how we’re planning on transferring the wing spar loads to the fuselage frame. What do you think? Can these plates be 3D printed? Maybe we need a composite of some sort (thinking plywood).
Cool! 6mm plywood is what I have now. But I’m up for trying to print them. How do we get those flat pieces in the fuselage?
We have successfully printed a test of the coupling for the fuselage sections- works great. We are now printing full sized sections of the fuselage! I am modifying a custom 24V dual core Ubis 13s with a drilled out tip… I need thicker walls to get close to the thickness of a dual wall 1mm tip print. I’ll try 1.5mm.
We are printing daily now and I have a couple guys always feeding the machine. We should have a few sections to show soon.
I have built a Big-E to the specs needed for this project- no bigger. I am going to add a single rail on top with one additional belt to eliminate wobble on the Z. This should allow faster prints and better finish. I want to minimize the need for sanding and surfacing. I’d like to use a new product coming to market that we discovered in the tv show- magna chrome. It is the same way they used to make mirrors! So it should render a completely chrome finish. It’s not paint, it’s actual silver playing. It would look so cool in true chrome. It will add weight but be mind-blowingly cool!
I’ll provide details on how those will fit together. Likely some kind of slotting. These are just sketches :), I’ll flesh out the details after I get the big stuff resolved.
I understand what you were asking now: " How do we get those flat pieces in the fuselage?"
Because the fuse is sectional, you can add sections to the frame one by one, and assemble the frame on a per section basis. This way previous sections can easily slide past.
How big do the dimensions of 6mm plywood get?
My large laser cutters are 4’x3’ so diagonals can be longer. That’s the footprint though. I can manually feed larger sheets with careful planning. The sheets are 5’ squares. We can bolt or glue multiple pieces together of course
Hey I started working on power requirements for this airplane. This is important for sizing the power plant. Here’s my Excel spreadsheet so far in case anyone want’s to check out my calculations and talk about them: http://a360.co/29oP2CL
I’ll have to refine these as we get more accurate numbers/predictions.
Cool. I’m sure weight will play a big part! I’ll compare one of my printed sections to the predicted weight in 360 to see if we are close. I’ll give you weights as we go too.
Kind of wish I had attracted more engineers to the project to take some of the load off of me. In anycase, I now need to perform a few back of the envelope calculations to figure out how to size the wing spars. With that settled, I’ll move on with completing the frame design. If I had more time, I’d put more effort into documentation and teaching.
OK, I set up a quick calculation of the stresses on the wing spar. I believe it’s conservative, then again, I’m not an aeronautical engineer.
I’m going to use this to help me choose a spar material and size. Check out the spreadsheet and let me know if you find a mistake or wish to discuss or know more about the calculations: http://a360.co/29v9Ubr
Searching for a source of carbon fibre or fibreglass rectangular tubes or rods. Requirements: reasonably priced, ~1.5m long, survived estimated wing loading. Maybe plywood spar?
Need to find American distributor/fabricator.
I’m down to provide the spars 
I’ll look for source too.
K, Let me know if you find something, I will too. The spar material needs to be about 1m long or more, and have a width on the order of 1.5" or more. It should be square or preferably rectangular stock. I think we have to throw around a few ideas to find a reasonably priced solution that will withstand the design wing loads.
Carbon fiber tube designed for bikes seems to fit the bill. Have you explored aluminum tubing? It’s easier to source. I’m ok with available and easy over hard to find and cheap!
I’ll explore the idea of circular tubing. That would certainly expand the possibilities quite a bit. Keep you posted.
Square aluminum tube is very cheap here and widely available too. Just saying.
So I’ve found some aluminum rectangular tubing specs online. 6061 aluminum has a breaking strength of about 40-60MPa.
I’ve found that for a 10kg plane flying and pulling 5Gs, with a safety factor of 1.5, we required 2"x1"x1/8" tubing. That size tubing for two main spars, will add 2kg to the plane.
I don’t know how reasonable it is that this plane will pull 5Gs, if I can back off that 5G assumption, we should be able to reduce the size of the aluminum stock.
For example a full scale decathlon is designed to sustain 6Gs: https://en.wikipedia.org/wiki/American_Champion_Decathlon
Note my calculations are “rough” as I’m working to get ballpark numbers, I may improve my assumptions to get better accuracy.
Sounds like carbon fiber is a better fit. Although I’m interested in your thoughts on plywood. I’m not that cost sensitive, it’s a massive project and tour time investment is priceless so let’s get the right tool for the job. My dime.
I’ll look into the use of plywood.
I found that 6061-T6 (commonly used for bike framing) has a yield strength of 240MPa, which allows us to use smaller stock, but we are still looking at about 2kg for both spars.
My initial thoughts are that aluminum is a viable option, but not necessarily optimal. We should evaluate all our material options and find a happy medium between size, weight and cost.
Spending a bit of time on this will save us some $ and effort down the road. Thanks for helping me figure out a solution here. I might launch a new thread soon and try to solicit other people in thinking about this engineering problem with us.