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CD Variations in the real world. 13 Jul 2020 03:21 #1288

Hi Phil,
I'm very impressed with the economy of your build and now you can kick some Swift butt. I want to apologize for some of my questions and many I hadn't sent. It turns out that my computer was kicking me out of the photo sections early and I was missing hundreds of them. Don't know if others have had that problem, but there is a ton more information available than I realized.
I also recognize the hundreds of little parts you made! I wanted to mention for your Windrose, I bought "Blemished" Oratex and saved a ton. Can't find a blemish anywhere.

1.) I understand about the weight gain with adhesives. I wish there was a way to bag the leading edge to get the resin right and then stuff the ribs in to adhere them without extra glue. Prepreg makes you realize how little resin one needs to bond.
Easy Composites uses an industrial adhesive in a self mixing dispenser. I wonder if that would be lighter?
Did I really see puddles of flox between the flaperon ribs?

2.) How did you get the flaperon noses to have consistent clearance with the gap cover?

3.) In retrospect, do you think the extra layer of glass on the ribs was necessary?

4.) What are your thoughts on the CD airfoil for a low speed, gentle stall, general aviation wing, like the Legal Eagle? It has a 15% sorta 2215 from the Mini Max. I need an 18% root airfoil to make my spar work. The CD airfoil has a lot of camber and a sharp nose. Any thought, especially about stall?

5.) I did some reading on the Windrose and I'm excited about the possibility of full span control surfaces that are operated from inside the fuselage. The wing is never open and has no internal controls. No birds or mice or spiders. With my double taper wing, the largest chord of the flaperon is 40% out. It's possible I get some flap without any extra weight or mechanism. Many years ago at Oskhosh, the "Backyard Flyer" had a simple mixing system where ailerons over-rode flaps automatically, regardless of a high flap setting. I need to dig out my old photos and look for that. I still haven't sorted the CD control system, but I like the side stick.
Apparently inboard ailerons work on the Windrose. I'm planning a large RC model to test.

Going camping for two weeks. Taking spar design stuff with me.


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CD Variations in the real world. 16 Jul 2020 19:07 #1289

Hi Phil,
Things are going well here.
Headed off on vacation with a stack of books.
Bought so tools from easy composites, as they were actually cheaper than stateside.
For example the epoxy catch pot.
I've found some 200gsm carbon for $16 a yard. It's listed as "seconds" which will be fine for my test pieces.
It's "Standard modulus". Is that acceptable?
I've been studying the trailing edge photos. I'm impressed that the foam on top of your fixture stayed straight and smooth.
My question is whether its possible to use a caul strip of glass or mylar on either side of your fixture, just the right height to reach the apex on both sides? Will the bag pull the caul in enough to force resin down the fixture? I'm trying to get a smooth finish.


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CD Variations in the real world. 12 Sep 2020 14:50 #1291

That's pretty funny -- I'm doing the same thing! I'd like to build a Legal Eagle first and then maybe a Carbon Dragon of sorts. I'm too heavy for the stock build as well, but I do structural analysis for a living so I plan on modifying the wing a bit to get more area and then beefing it up for the weight. We'll see if I can actually ever get to it, but I've loved this thing for 30 years!

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Last edit: by Kenny Andersen.

CD Variations in the real world. 12 Sep 2020 18:38 #1292

Hey Kenny,
A Structural Engineer is just what I need!
I have designed a carbon wing for the LE and plan to use the weight savings to add a little wing.
I also follow Rol Klingberg and am experimenting with a thin foam sandwich for the D-tube.
Just ordered a ton of carbon and hope to make some things to break,
I have gone to a single strut and D-tube similar to the Le Pelican, only carbon.
I'd be happy to collaborate.
This email address is being protected from spambots. You need JavaScript enabled to view it.

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CD Variations in the real world. 13 Sep 2020 04:55 #1293

Hey Phil,
What's your background? What I need is a designer! As I was telling Phil L, the packages that I use are PATRAN preprocessor with NASTRAN as the solver. PATRAN will do so rudimentary geometric manipulation, but it's not a design package -- it's an analysis pre and post-processing package. I've mostly worked for large aerospace companies over the years (Boeing, Bell, Douglas back in the day, Lockheed and Triumph (formerly Vought)), and both fortunately and unfortunately there are consequences to that. One being that with a large company you end up being a specialist with a deep, but narrow skill-set. Currently I'm working on an expended assignment in South Korea (KF-X). If I can get the geometric data (electronic) then I can import it into an analysis package. Previously there was someone on the board who had passed that on to me, but I had a hard drive crash and so lost the data. At the time there seemed to be minimal interest in doing a DFEM of the Carbon Dragon, so I didn't pursue it at that time; but, I'd be willing to look into it again if there is interest.

The strut should result in a lower wing weight, but at increased drag. The wing section is pretty deep already, so I'm not sure it;s necessary to do a strut unless you MUST keep the weight to 155. Even in that case, what I'm thinking is an electric assist, which would allow you to bump the weight to 254 lb. and still stay in the ultralight category. The Archaeopteryx has a 42 lb (if I remember right) package that they can add to the basic craft that allows it to be self-launched. IMO this would make it particularly useful. With a similar package and a 200-220 lb pilot the gross could still be under 400-425lb, which I think should be manageable. If you keep the g-loading reasonable then it seems workable. Remember, as Phil L has noted you feel every bump with a Carbon Dragon (like fishing with a small graphite pole!) -- IMO it doesn't maybe make too much sense designing for extreme g-factors because those aren't the kind of days that you'd want to be flying a Carbon Dragon (you'd get your arse kicked!).

What I'm thinking is basically using the carbon dragon wing, modified, and a pod similar to the Archaeopteryx where you could put a electric assist or not.

Increasing the wing area: What I'm thinking is to not taper the wing right away, but maybe make the first 1/3 a Hershy bar before starting the taper. I like Phil L's 3- piece wing idea, and that would be a good place to start the taper (and attach a strut if you really were bent on that). I think the area goes from 140 to 150+ if you do that. Also, as long as the wing is stressed for the additional pilot wright and electric assist, then it will still fly well, but the wing loading might be just slightly higher, which in the end would still keep you well within the ability to use micro-lift.

I never did hear a final weight of Phil L's or Steve Arndt's Dragons, which would be helpful to know. I would also note that the more carbon parts you have the longer it will take...

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CD Variations in the real world. 13 Sep 2020 17:25 #1294

Hi Kenny,
My background may disqualify me as a build colleague. I have no formal training, just a lifetime of building and study of design and innovative plans. I took a workshop with Marske on carbon sailplanes, but never took the plunge out of fear of the unknown.
Phil L changed my world view with his videos of him alone in a garden shed building a carbon airplane.
And hen breaking it in his driveway.
For all the fancy composite software, the answer in the end is always build it light and break it, rebuild it and try to break it again.
I can do that.
I'm retired and I have the time and the means, and my shed is bigger than Phil's.

I appreciate you comments on my design.
I think my mission may be a little different than yours.
My father taught me to fly in a Champ when I was ten.
I have definite bias toward the sound, torque, and reliability of four stroke engines.
I have watched as everyone struggled to find the power to safely fly a part 103 airplane with a 250lb pilot.
That part of the puzzle fell into pace for me with Les Homan's LE XL with the three cylinder Verner 3v.
The huge prop disc is perfect for small draggy puddle jumpers with pilots that weigh more than their aircraft.
If you haven't, please google Les Homan on YouTube.

The other designer that influenced me was Gene Smith and his Backyard Flyer.
Check out his interview on Google where he talks about the Backyard Flyer.
Then watch him fly it fifty feet off the ground at 25 mph under perfect control.
From him I have adopted Junkers Flaps for both lift and directional control.
They add to wing area and are controlled from the fuselage. No openings or hardware in the wing.

Lastly, the strut. I believe in 4130 around the pilot for safety.
Plus, it is required for the vibration and weight of the engine and I think the Legal Eagle fuselage is about as light and simple as one can get.
However, the overhead cabane demands struts. But not two.
Another pivotal design was the Le Pelican. Single strut, D-Tube, drag spar.
I like your idea of more area out to the strut and then taper.
With the Junkers Flaps controlled from the fuselage, the trailing edge needs to be straight and close to perpendicular to the fuselage. Thickest part of the spar should be at the strut attach. We don't need struts far out for strength, just stability.
Now the wing starts looking like a Stinson Reliant, or a Westland Lysander.

I'm thankful for Phil L's guidance and when I lose focus, I just re-watch the video of his face above the Alps.
But if this thread is not appropriate for this site, they need to let me know.
My airplane uses Irv Culver's airfoil and Jim Maupin's design concepts, but it's not a sailplane.
Phil D

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