Advice on quick & simple construction method for a "low AR" wing?

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leviterande

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Hi all, I know I am not a very active member here. Usually Im very busy designing, experimenting, testing and flying RC models to validate/invalidate full scale designs/ideas. It can honestly be very daunting... as 97% of models/experiments, time, money energy is wasted to find a "working idea".

Done a few more RC model tests of various planforms (circular, delta, bixel, double delta, zimmerman etc) The inverse zimmerman handled pretty well. Now that the pinkfoam 1/3rd scale model is finished. Im closer to the fullscale stage and I would highly appreciate inputs / advice about relatively quick & simple construction methods for "deep chords" of a low AR wing.

Rough dimensions of the fullscale:

-inverse zimmerman shape (AR 1 - 1.5) (similar to but not exactly a Facetmobile planform)
-4m x 4m (13.2ft x 13.2ft)
Airfoil thickness around 10-12%
-High wing configuration
-Fuselage-hull under the wing
-Tractor upfront propeller

Any ideas on simple construction methods, maybe simpler deep chord ribs? Most aircraft kits include machined alu ribs and other parts that I cant do in my garage.
I tried fullscale aluminium tube/gusset riveting of giant 16ft ribs and it was very time consuming(maybe its me who is doing it wrong?). Foam ribs however seems like a quicker simpler method but are they better/suited for this deep chord low AR wing situation?

Alternatives:
1-
Aluminium ribs (square tube + gusset)+ fabric
2-wooden stick ribs + fabric
3-Foamribs + glassed foam spars + fabric
other better ways?(full composite skin? Rutan full core but may be heavy?)

1- Pros: Have experience in that. Strong, not heavy, proven method, easy to incorporating hard points(engine mount, elevons, fuse etc.)
Cons: very time consuming in my experience, specially making/drilling/attaching the gussets but maybe Im doing it wrong? Maybe I can use angled flat plates instead of square tube+gusset. Then just rivet the angled flat plates to form the ribs?

2- Like nr 1 but perhaps quicker build due to lesser work around gussets: just glue the wooden gusset to the wooden sticks? or are there any big disadvantages here. David Rowes' ufo ribs are made out of timber but not a lot of info can be found.

3-Pros: potentially very quick build. No need to construct the actual ribs/spars or gusseting. Just hotwire, glue the foam ribs/spars and glass the top/ bottom. Or and add a thin plywood strip on top/ bottom. (maybe also inbed alu. tubes inside for strength and hardpoints attachments) Is this really easier than 1 and 2?
Cons: not straightforward to attach hardpoints like the engine mount and fuse. Is this the deal breaker of foam building?

I apologize for sounding very confused.
Your input is very appreciated!
 

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Riggerrob

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Great sketches. And glad to hear that you are flying sub-scale RC models. That puts you way ahead of the rest of us who are only doodling high-wing deltas.

Take a close look at Verhees Delta.
It uses deep aluminum ribs. They start with flat sheets of aluminum, the bend over the edges until they match the airfoil. Many people using this method today CNC cut molds from high-density MDF. MDF is basically sand dust bound together with glue, lots of glue, making it dense enough for tooling on one-off airplanes.
Over on the 3D printing thread, there are a couple of posts about 3D printing PLA dies for pressing lightening holes into aluminum ribs.

OTOH rib material choice is often driven by material choices for spars and skins. Using the same material in all wing components reduces thermal stresses as parts expand and contract as the temperature changes.
 

jedi

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"I'm closer to the full scale stage and I would highly appreciate inputs / advice about relatively quick & simple construction methods for "deep chords" of a low AR wing."

You could carve it from foam same as the model but that would get darn heavy wouldn't it?

So you have modeled the shape but not the construction. That is the problem.

Be careful what you ask for. Here is my out of the box answer for a 24 foot span 16 foot cord LAR ultralight.

I would prefer 15% thickness giving a thickness at the wing root of nearly 30 inches. You are right that is some rib. Even at your lower limit of 10% it is about 20 inches deep. A paraglider or PPC like ram air inflatable wing is the answer. The prop blast will even inflate the wing for you.

Purchase a PPC wing cover to slip over your wing spar. You will not even need to paint the thing. When it is time to replace the cover it could be done in minutes or hours, not days.

The next issue is how to build the wing spar. I have out of the box concepts for that also. We can discuss that whenever you like.

Interesting project. :popcorn:
 
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leviterande

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Hi thank you for the replies.
Riggerrob, verhees delta Has these huge sheets as you said. seems simpler than gusset+tube. MDF sounds even simpler. Need to check the weight though!


jedi, I was actually thinking about using cheap alibaba inflated 4m/3m/2m blimps and stack them side by side to create a fast simple test delta wing but didnt do it. (havent even opened the purchased blimp boxes)

BBerson, Dyke Delta in 4130 tube truss sounds very attractive at first glance. Strength to weight ratio is even slighter better than 6061. Seems the best simple quick construction so far. Strong & light, just cut the tubes, weld them and your done. Hard point installations is better than in composites. Only thing is just that Im not a good welder, only welded a little a long time ago. But I could just hire a local welder to do the job. lets see if I can fine one. Im ready to pay as far as that is not way too expensive.

Most my design work was based on tube + gusset alu tube truss frame due to ease of construction and lack of need to special skill/tools. I found out last year though that it was a very time consuming process..

I never tried steel in the stress analysis software ironically. Only aluminium.
I will look into 4130 tubes truss, build a digital model and testrun the frame in my buckling stress software.

Tiger Tim, yeah I would like to find better pics at how the UFO frame looks. You mean timber construction? I am not sure if I got what you meant.
 

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Aesquire

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The MDF isn't part of the airplane. It's used to make the jig/fixture to make the ribs. Many sheet metal ribs in homebuilts are simply cut out of sheet, deburred, then pounded over a form with a rubber or leather hammer. So you get bent over tabs to fasten other parts to, and turn a 2 dimensional weak sheet into a 3 dimensional stiff part. Then you tweak the part to get it all straight so it fits properly. Various tools and techniques.

That's a very simplified version. Also, you take sharp or jagged edges off between most operations. That removes crack starting irregularities, keeps your tools, fixtures, and skin from being torn up, and helps everything fit together.
 

Aesquire

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"Egg crate", construction, strips with slots that interlock to form a grid, construction can be adapted well to sheet metal low AR designs. No big wing spars, just multiple ribs fore and aft and stringers side to side. It even self jigs straight if you design it right. You will need to double up some stringer/spar parts to strengthen where landing gear and engine mounts, but it would assemble easy.
 

delta

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"Egg crate", construction, strips with slots that interlock to form a grid, construction can be adapted well to sheet metal low AR designs. No big wing spars, just multiple ribs fore and aft and stringers side to side. It even self jigs straight if you design it right. You will need to double up some stringer/spar parts to strengthen where landing gear and engine mounts, but it would assemble easy.
I had this basic same idea using glassed foam sheets. 2plwinglets.JPG
 

Tiger Tim

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Most my design work was based on tube + gusset alu tube truss frame... I found out last year though that it was a very time consuming process
That may just be the price you pay. Did you find you got better and faster at it as you went? Could you extrapolate that improvement out to the point where you picture it getting easy and fast?
 

Sockmonkey

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"Egg crate", construction, strips with slots that interlock to form a grid, construction can be adapted well to sheet metal low AR designs. No big wing spars, just multiple ribs fore and aft and stringers side to side. It even self jigs straight if you design it right. You will need to double up some stringer/spar parts to strengthen where landing gear and engine mounts, but it would assemble easy.
You could do that with just about any material. Sheets of ply, fiberglass, or carbon fiber.
Adapt the plans to whatever you have without needing to tweak them much.
 

leviterande

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Hi again. I am aware Im inactive online. I will try to reply to all. I have been busy as always tinkering with software and in the garage...

Aesquire,
Thats a very clean looking idea. Im making sure right now to figure out all the torsion stress/loadings as well.

Hephaestus
Wainfan is an admirable character in aviation. Cant wait to see the new FMX-5.
I worked the last two years on a facetmobile type configuration due to all known advantages of low weight,NASA report, tests, low complexity and safety. It was in my eyes the perfect machine for the goal I had but in the midst of the aluminium tube frame construction last year I hastily turned 180 degrees and changed my mind due to two reasons:


A--Risk of bad visibility IMO (even with floor GLASS panels)(I suck at taking risks)
B--Far from enough AOA for max CLmax & quick desired takeoff at low speed.

A-I made full scale cockpit front mock up (made mostly from unused plastic spars, foam, aluminium and garbage cans, sliver tape :D) to only test the real life visibility from inside(a thing I can not test or try in CAD or Blender, I need to see it with my eyes instead of a camera). I tweaked a lot but wasnt satisfied. Its sad I didn't find a solution to the visibility problem.

B-For my designed 25-28 deg AOA of a facetmobile type vehicle the landing gear/under-hull is just going to be amazing!. I went thus for the most practical solution that fit my intended need. Admittedly not as clean, pretty, simple or lightweight but fits the bill for a Safe-low-AR with low speed takeoff/landing and great unhindered visibility: a High AoA, High Wing configuration.
(there is far too much of information and sadly too little space & time to share here right now on all kinds of things)
So, back to on topic.

Tiger Tim
Yes in the beginning the construction was slow as I was "learning" more tiny but efficient ways to speed the process up but it was still a longer than I thought. fabricating the 3d gussets that would fit between 5 tubes and getting the angles of all them right+ drilling/riveting them in those tight spaces was a "little" difficulty surprise for me. Thats the price to pay as you said and could be worth it. I think I also could design the ship differently to simplify these 3d angles somehow


billyvray
I wish there were detailed photos of the UFOs

Ideas Sofar:
foam rib-sheets like egg crates / D.R. UFO glassed or plywooded is simplest and fastest as the foam is easiest and fastest to work with/shape. Disadvantages: hardpoint design is harder. Stressloading analysis is also harder.

4130 tube frame ticks all boxes. Strong, light, simple tube cutting, stress analysis is straightforward, hardpoint installation is no issue. I just need to find a good welder to do the TIG welding for me.

Sheet aluminium construction like dyke delta looks good too. maybe a little heavy?

Gussetless idea?
So how about aluminium ribs made from angled /T-bars (See pics). no gusseting and thus its much faster to build. minimal work is needed. since ready off the shelf plates attach to each other without gussets This would perhaps tick all the boxes? see picture to judge if the idea is too stupid? Hidden problems?
---------------

Just threw a picture of : previous delta-facetmobile-type ship with distributed electric propulsion; stress analysis.
Another pic: Early RC Delta lifting body that obviously failed. (Can you guess why?)

One want to almost give up because of the sheer amount of R&D information incorporated.
 

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Tiger Tim

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Gussetless idea?
So how about aluminium ribs made from angled /T-bars (See pics). no gusseting and thus its much faster to build. minimal work is needed. since ready off the shelf plates attach to each other without gussets This would perhaps tick all the boxes? see picture to judge if the idea is too stupid? Hidden problems?
Factory ribs in a J-3 (Piper, not Janowski) are sort of like that. I’ve always been impressed by how light they were able to make them though they don’t seem tolerant of rough handling outside the airplane. Once installed they seem to hold up okay. I think the more serious aerobatic guys with clipped wing Cubs used to double up the ribs so that shows the sort of margins they were built to in order to reach a minimum weight target.

It’s not a great picture but here you can get some idea of what’s going on. Piper used a bunch of different hat sections and whatnot that I imagine were rolled in-house.
 

leviterande

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Thanks! That is neat Tiger! I always get a comfortable feeling some "legitimate" manufacturer doing a similar "fringe" idea I had in my mind. it gives me a good comforting reassuring feeling I am not way out there. Dunno why I am weak and always need confirmation of ideas like this.

Ok so its sheet aluminium with / or Tbars plates that I am considering right now.
I am doing more stress analysis tests with single sheet/Tbar aluminium now.
So far everything looks good, "relatively simple" and lightweight.

Next:
Sharpness of edges(vortex lift)
washout and reflex incorporation.
 
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