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J.L. Frusha

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Scaled, tiled and printed the layout. Trimmed and taped it to a sheet of foam-board.

Tomorrow I'll cut it out and try to get the model together and balanced.

May try to cut the LE slots. Going to trim-off the Junkers Flaps/Controls, squeeze and tape the LE &TE, then try to mount them.

Once I get that done, I'm going to see how it glides.

~53 inch wingspan

The rectangular thing at bottom-left is the seat, stretched for the diagonals and notched for both an instrument panel and the control stick.

1643092641829.png
 

J.L. Frusha

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Round off the leading and trailing edges of the foam board. Glue or tape a dowel, or soda straws on the forward and rear edge so they're not square.

We can get to airfoils a little later :)

Don't have dowels, or straws. Going to be using fireplace matchsticks for landing gear, struts and spars/wing joiners.


Trim a bit of the foam out, glue and tape the LE & TE is about as good as I can afford at the moment. It'll be tricky enough to get it balanced, with the CG where it is.
 

J.L. Frusha

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Go to McDonald's and get a handful of straws. If you can't source free straws, I'm afraid I have some bad news for you about building an aircraft.

LOL... Thank the Gods, there isn't one within 30 miles. Greasy, nasty stanky places, McDonald's are.

I'll check the shop. We may have a few small dowels, but don't hold your breath.
 

Martin W

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Dollar store sells a bundle of about 30 wooden skewer sticks for BBQ etc .... about 1/8" dia and 10" long ... I have found many unexpected uses for them ... tried breaking them in two ... fibrous wood ... strong .... and will flex without breaking.
 

Tiger Tim

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Working on a scale model foam-board chuck-glider with 25 1/2 in wingspan.
I should warn you, mine flies suspiciously well.

Once the glue dried I eyeballed the CG and gave it a toss across the room. It sailed along as nice as any other chuck glider would have, but to be honest that sort of got me questioning things. My model showed a good bit of pitch stability without any real aerodynamic reason to do so. The wing on mine is just a flat plate and I hadn’t yet installed elevons, trim tabs, or any sort of wash-in. I at first thought it was maybe just neutral so I gave it a toss inverted and it did a split-S immediately back to stable upright flight. I suspect the heavy plastic wheels I used are acting as a pendulum and holding the whole glider at about the right pitch attitude for flight.

I have some ideas on how I can mess with it further and why I would want to.
 

J.L. Frusha

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I should warn you, mine flies suspiciously well.

Once the glue dried I eyeballed the CG and gave it a toss across the room. It sailed along as nice as any other chuck glider would have, but to be honest that sort of got me questioning things. My model showed a good bit of pitch stability without any real aerodynamic reason to do so. The wing on mine is just a flat plate and I hadn’t yet installed elevons, trim tabs, or any sort of wash-in. I at first thought it was maybe just neutral so I gave it a toss inverted and it did a split-S immediately back to stable upright flight. I suspect the heavy plastic wheels I used are acting as a pendulum and holding the whole glider at about the right pitch attitude for flight.

I have some ideas on how I can mess with it further and why I would want to.
Where's the CG? just about the center of the leading edge? That's where the wing calculator said to put it...
 

Tiger Tim

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About how much dihedral?
I dunno, some arbitrary eyeballed-in amount. I think around 3/8” each tip. CG is just a tad ahead of the wing leading edge at the root though the heavy wheels down low might be the reason it flies the way it does. I think I’m going to take them off and re-balance for a few throws to see if some bad habits surface.
 

J.L. Frusha

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Any updates -- I am really liking the look of this build. cheers
The foamie at 54 inch wingspan was very tail-heavy, which corresponds well to the counterbalance of the pilot being somewhat forward of the CG. Wind and weather have kept me inside ever since.

I have shifted in another direction, but plan to tinker with the design from time to time.

1644412657145.png
 

Aesquire

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Primary gliders, like the model above, can be great soaring machines, if you aren't dedicated to high speed cross country competition.

Sandlin's "airchairs" are the current generation in a parallel design evolution.

And you can indeed fly out of your local area, it just takes more time & maybe skill.

Keeping landing sites in reach has been my biggest limitation on flying cross country, after lack of talent, but there was that day I had to choose a sure safe landing on an athletic field or a few more miles to a tight landing near a monastery.

The monks were very nice and quite excited to see me land on the driveway. But I still wonder if I should have cut the glide short, and gone for the volleyball courts at the nudist colony.
 

Topaz

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Been fiddling with an ultralight design, figured it's time to get a bit more serious...

Wing Calc. puts CG ~3/4 in ahead of the V.
Expect to use the 1/2 VW engine w/~32 in prop.

Wing calculation does not include the Junkers Control Surfaces.

Mechanical mix Flaperons, Leading edge Slats, 2 x 2 Aluminum Fuselage with welded reinforcement,.
Wing construction loosely based on the Chotia Woodhopper and Gypsy design, using Foam-filled Carbon Fiber Spars
and possibly Tensegrity ribs and reinforcement, with struts as necessary, perhaps vacuum-infused CF skins.

Initial design:

View attachment 120853

I'm very late to this thread, but tailless designs fascinate me so I'll throw in my ¢2 for what they're worth.

This design is actually a lot more interesting than perhaps has been given credit, IMHO. Are there some possible issues? Of course, but what initial concept design doesn't suffer from a few of those?

  • The concept here is not unlike the Marske Monarch. All the pireps I have for that ultralight glider/motorglider are fairly positive. I don't see any showstoppers here that might make this terribly different.

  • Much has been said about the high thrust line. Well, okay. Even as it sits in this first drawing, simply moving the vertical tail back about 6-8" provides room for bringing that engine down somewhat lower. Given the geometry of this thing, even getting it down to the level of the wing chord is probably "enough." The later drawings with twin engines on a cross-brace would work, too. I really don't see this as a major issue.

  • STOL capability: Well, yes and no. The OP was clever (or lucky, which amounts to the same thing) to choose a swept-forward wing on his tailless design, because nose-up trim requires the elevons (as configured) to go trailing-edge down, increasing lift from the wing. That the lift is applied mostly outboard is unfortunate - stronger/heavier spars needed - but let's hand-wave that away for the moment. There's a myth common about tailless aircraft, that they "can't use flaps." That's not true. A swept-wing (forward or aft) tailless airplane can use flaps, provided that deflecting them does not change the total moments around the CG in pitch. That can be done by carefully designing the span-wise extent of the flaps (or flaperons) such that the same amount of lift is added both fore and aft of the CG, and the change in pitching moment due to flap deflection is cancelled out by a little more lift forward of the CG. This set of calculations is not for the faint of heart, but it's not impossible, either. It's not really something you can "eyeball," so this will be a case of "doing it right," with math or doing without. It might be possible to "cut and fit" a viable solution using a model, but that seems like a risky way to go, to me personally. YMMV. On the topic of slats: I don't see an issue, provided they're full-span and fixed, not movable. The Me-163B had outboard slots, as did the Northrop flying wings. A slat is just a slot that isn't faired into the wing profile. Do I think slats will do a lot of good here, in terms of adding to STOL capability? No, but they're not going to do any harm, either, with the provisions I made earlier. Partial-span slats/slots make high angle-of attack stability and control design work a lot harder unless you fully understand the principles relevant to tailless aircraft. Northrop and Messerschmidt were using outboard slots to ensure good low-speed behavior and aileron control for their swept-back wings. Partial-span slats in this case have the potential for a radical pitch change as they start to take effect at takeoff or landing. I'd either keep them full-span or delete them entirely.

    If you're going to use flaps (or flaperons) though, you're going to need a separate set of pitch-control surfaces (elevators or elevons) near the wing tips. For flaps to work, they need to be pitching-moment-neutral, as described above, but this is exactly what you don't want for pitch control surfaces. So those functions will have to be separated. The flaps will be inboard of the elevators. The latter will be out near the tips and forward of the CG. Either or both can also be given a roll-control function, so "flaperons" inboard and "elevons" outboard. Mixers for such an arrangement could get "interesting."

    At any rate, whether or not this design can actually function as a STOL machine depends on your definition of "STOL," more than anything else. A big-enough wing area and pitch-moment-neutral flaps could bring the stall speed of this design very low, and that means short takeoff and landing runs. Not going to win trophies up in Alaska, but it'll be better than most "conventional" ultralights.

  • Some mention of aeroelastic issues with the forward-swept wing have been raised. Doesn't bother me, personally. This airplane will be so slow that problems shouldn't show up, much like the Monarch. At any rate, just making this a strut-braced wing (which you seem to have already done on your model) would mitigate most of the aeroelasticity issues and help with the "heavier spar" issue I mentioned earlier.

  • One thing that hasn't been addressed is the landing gear. Rotating the nose down, to get the tailwheel off the ground, is going to suddenly rob the wing of a lot of lift, as the elevons go trailing-edge up to do that in your current design. "Reverse flaps," if you will. Then a sudden reversal to nose-up will fairly yank the airplane off the ground. That's going to be a tricky operation for the pilot, so that the airplane lifts off instead of just slamming the tailwheel down. So, IMHO, the options are to either let the airplane "fly off" the ground in the three-point attitude on its own (don't try and lift the tail during the run), or switch to tricycle landing gear, where there's no need. For the shortest takeoff run, the tri-gear is probably the way to go, however contradictory to usual practice that might seem.
Interesting concept. I like your foam model recently shown. Fly the heck out of that. Learn a lot. Even simple models like that can be an incredible learning tool, especially for "unconventional" designs.
 

J.L. Frusha

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Messages
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Primary gliders, like the model above, can be great soaring machines, if you aren't dedicated to high speed cross country competition.

Sandlin's "airchairs" are the current generation in a parallel design evolution.

And you can indeed fly out of your local area, it just takes more time & maybe skill.

Keeping landing sites in reach has been my biggest limitation on flying cross country, after lack of talent, but there was that day I had to choose a sure safe landing on an athletic field or a few more miles to a tight landing near a monastery.

The monks were very nice and quite excited to see me land on the driveway. But I still wonder if I should have cut the glide short, and gone for the volleyball courts at the nudist colony.


I'm also looking for Super Floater plans, fwiw. Haven't asked Mike Sandlin, but had the download on a previous laptop. Lost stuff in the transfer.

Anyone have a PDF they can share?
 
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