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Starman

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Seems sort of unnecessary. The purpose of the D-section is to provide torsional rigidity. If you make the aft section of the wing flex style like you are saying, there is nothing for the D-section to support... it would be wasted stucture.
I'll make a drawing to save a thousand words :), the D-section is nothing more than a streamlined spar and torsional strength for the wing tip rib. The wire pulling the fabric to the back makes the spar support the fabric.
 

bmcj

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Thanks Bruce, I remember 'keel' now. when they went to the higher aspect ration they added the wing tip 'ribs', were those called ribs?
The battens are often referred to as "ribs". I forgot what they call the small spreader bars at the wingtips (on the newer gliders).
 

Starman

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OK, here's the drawing, fast aint I? I think if the wire trailing edge was generally below the bottom of the spar that the blanketing effect should reduce the drag of the spar by a fair amount.

 

bmcj

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I'll make a drawing to save a thousand words :), the D-section is nothing more than a streamlined spar and torsional strength for the wing tip rib. The wire pulling the fabric to the back makes the spar support the fabric.
I see what you're saying. the D-section holds the end rib in place (without twisting) and the trailing edge wire defines the location of the trailing edge. Are there any ribs in the wing or just battens and the tip rib? Perhaps holes or slots along the span of the D-section would allow you to slip carbon fiber battens in for ribs, then bow them back to the trailing edge wire.
 

Topaz

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Essentially a Princton Sailwing without the bottom-surface fabric. Search for that term here in the forum, and you'll get some additional information.
 

Topaz

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We usually use this ----> :beer:

There are some plusses and minuses to the Princeton Sailwing. Start thinking along the lines of ensuring identical rear-wire tension between both wings, and what might happen if you don't achieve that goal, and maintain it in-flight during various maneuvers.
 

Starman

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I saw the post about the wire tension and it is important. Possibly use one wire from wingtip to wingtip and let it adjust itself in the middle. That might be a problem though during some maneuvers that create unequal forces on the wings.

 

bmcj

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We usually use this ----> :beer:

There are some plusses and minuses to the Princeton Sailwing. Start thinking along the lines of ensuring identical rear-wire tension between both wings, and what might happen if you don't achieve that goal, and maintain it in-flight during various maneuvers.
Why not let the tension vary and hook the control stick to the wire so that it shifts the greater portion of the tension (or, more correctly, slack) from one side to the other?
 

Starman

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What an interesting idea. That could possibly serve as aileron action.

I see what you're saying. the D-section holds the end rib in place (without twisting) and the trailing edge wire defines the location of the trailing edge. Are there any ribs in the wing or just battens and the tip rib? Perhaps holes or slots along the span of the D-section would allow you to slip carbon fiber battens in for ribs, then bow them back to the trailing edge wire.
It looks like the Zipper sailwing gets by without battens, but that would be a good fallback scenario because it could be added in later if needed.
 

Topaz

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Why not let the tension vary and hook the control stick to the wire so that it shifts the greater portion of the tension (or, more correctly, slack) from one side to the other?
Off the top of my head, I can't see any reason why it wouldn't work, but then I've done no research at all on sailwings. Might be work a try. I'd do a lot of model tests first, personally. I wonder if you could get enough differential tension in the wires to provide adequate roll control, without allowing any possibility of too much slack appearing in the 'loose' side. I could see "luffing" being a problem in that scenario.
 

Starman

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Luffing is a sailboat term which describes the sail flapping or rippling due to improper wind direction/sail tension.
______________

Just a reminder as to where this design could be eventually heading, possibly something for my brother who is a retired F16 pilot.

With something like a V10 or four rotor wankel for power.

This is the main reason that the spar sweep needs to be adaptable. In a case like this the horizontal tail attach points act as torsion connections for the wing.
 

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Topaz

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Why not just go there in the first place, perhaps with a little less leading edge sweep and a bit more area? Those wings would be a snap to build in foam and glass. Keep the weight and wing-loading down and this isn't much more than a pusher Dyke Delta. A bigger, more powerful motor and a higher wing loading could be used for your brother. With just a little rework, the engine could be on the CG, making it much easier to accomodate such changes.

All the added complexity of multiple wing sets, tail sets, and varying control systems - and accomodating those in the original fuselage design - seems like a needless complication. By the time you'd build any of those, you could have sufficient pilot training and experience to handle a lightly-loaded delta like this. There really isn't any 'shortcut' to building an airplane. No matter what you eventually do, the design and build process is going to take a couple of years, absolute minimum.

You can do a lot of training and flying in a couple of years.
 

Starman

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Well that's always a possibility. Luckily I don't need to make that choice till I'm well along with the fuselage. In a case like this most of the center spar strength would be wasted, I guess, but I can live with that. At least it would be easy to figure out where to store the landing gear.
 

Topaz

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Well that's always a possibility. Luckily I don't need to make that choice till I'm well along with the fuselage....
Well, you know that I disagree with you on that score, but there's no point in repeating the discussion. We'll simply have to agree to disagree about the philosophy of building before the design is complete.
 

Starman

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That's fine, I can't see much that would need to be changed with the fuselage other than the spar center section being overbuilt for a small delta, it would be better for the bigger delta that you described. Of course when I make the fiberglass rear body panels (if I use fabric first) I will need to add some stringers or attach points for them.

Cooling inlets would need to be varied according to potential speed. What else?

I realize that due to the adaptability that it won't be optimized for most cases, but it should be pretty close.
 

bmcj

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I DO like deltas a lot.
Just for the heck of it, you should look up the Dyke Delta and read a little about it. From the photos I've seen, it looks like the entire airframe structure (fuselage, rudder, wing spars, wing ribs) is made up of welded steel truss work, then covered. The only think I've read that might be considered a shortfall is that approaches should be made flat with power carried.
 
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Starman

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I've studied the Dyke Delta quite a lot, it uses fiberglass panels laid up on a flat smooth surface, I forgot how he attaches them, I want to say pop rivets but fiberglass doesn't like that too much. I've read that technically the Dyke is not a delta but a highly tapered flying wing with slight sweep.

I better get to work now.
 
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