Oops, I've already discovered my error. Because the wings are supplying the lift, you subtract their weight in the calculations. I missed that when I did my calculations. I used a higher gross weight, therefore I should have a bigger safety factor, or allow me more weight when I add motors and batteries to the glider

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From: Rick Mullins <This email address is being protected from spambots. You need JavaScript enabled to view it.>
To: "This email address is being protected from spambots. You need JavaScript enabled to view it." <This email address is being protected from spambots. You need JavaScript enabled to view it.>
Sent: Friday, September 23, 2011 9:05 PM
Subject: Re: [Carbondragonbuildersandpilots] Re: Wing calculations



When you were calculating your bending moments you used 260.4 lbs as the payload. In the next step you calculated the wing loading and used 145.6 lbs as the glider weight (seems kind of precise for a guess at glider weight ) and max pilot weight at 190 for a total of 335.6 lbs. Isn't that the number you would have used in the bending moment calculation?


I copied the spar Jim Marske built for the Monarch and just have the load transfer rods on one side of the spar for simplicity. The one change I made was I extended the bars several inches so I could taper one end. On the first spar I built (that I later discarded) I used rectangular bars and it seemed like it would be a high stress area where the bar ended and the rods continued out to the tip. A taper would help spread the load at that transition. No calculations to back it up, it just looked like a weak area. I uploaded a picture to my photo section of the new bars.


I wasn't familiar with the 6082T6 alloy. I had considered maybe using titanium as Steve Arndt did, but I'll have to look into this as a possibility. Titanium is probably overkill.


I also got a grin out of the paper you were using for your calculations. When I graduated from college my first job was with Nixdorf computer. I worked there for 24 years doing field service. They never did very well in the US and I was laid off shortly after they were bought by Siemens

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From: Philip Lardner <This email address is being protected from spambots. You need JavaScript enabled to view it.>
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Sent: Friday, September 23, 2011 1:03 PM
Subject: [Carbondragonbuildersandpilots] Re: Wing calculations



Hi Folks,

I've just uploaded another few pages of wing calculations based on Jim Marske's Composite Design Manual. The uploads are in my directory (Phil Lardner) in the files section of this group - filenames 'Page 15' to 'Page 19'.

Page 15 is a 1:1 scale drawing of the main wing root-end metal fittings and form the basis of the calculations on the pages that follow on.

Page 16 - 19 detail the dimensions of the CF bars that transfer the cap loads (at +10.5g) to the root end metal fittings, and the dimensions and layout of the metal fittings themselves.

As ever, I would be most grateful if someone could double check my numbers and method to make sure I haven't skipped a step of misunderstood something... or generally screwed up somewhere!

Comment welcome,

Phil.