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Oct 14, 2021, 05:43 AM
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Quiz Question--Has P-RIX ever been flown successfully?


P-RIX is short for my scratch-built design Pterosauris RIX, shown in the attached pictures. It has a 9 ft. wingspan, Eflite-10 motor, and no vertical fin. It has elevator, aileron and throttle control.

For the purpose of the quiz question, "flown successfully" means that under radio control by the pilot, it has climbed in the air under its own power, was able to go up/down, turn left/right and has landed "without being wrecked," as the Wright brothers once wrote.

So the Quiz Question is, has Pterosauris RIX ever been flown successfully?
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Oct 17, 2021, 03:02 PM
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Pterosauris RIX


Wait....wait. Wait a sec. WHAT? wait. This is the wildest thing I've seen on RCgroups in a while. It really does look like some kinda flying reptile - has a wing similar to a kind of spooky red vulture...

I'd like to submit an answer to the quiz: YES, it has "successfully flown" per the Wright Bros definition.

Cheers mate! Wonderful, creative, creation.
Oct 17, 2021, 03:48 PM
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Thanks for the comments, and for your answer to the quiz question! Sometime later I will give the answer to the quiz question; I first want to see if anyone else has an answer.
Oct 20, 2021, 04:16 PM
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Betting YES.

I've read a couple articles about a mix of wash-in, wash-out, dihedral, and anihedral making for favorable roll-yaw coupling and lateral stability on a flying wing. Have been poking around with the numbers for a 60" version of this, but it uses more dihedral & anihedral and avoids most of the tail. Goal is to mimic a frigate bird silhouette from all aspects as much as possible. Definitely a fun art & design project.

May crib notes from your picture on structure. It's a pretty bird.
Oct 20, 2021, 05:16 PM
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Answer to the Quiz Question


Quote:
Originally Posted by USKP01261
Wait....wait. Wait a sec. WHAT? wait. This is the wildest thing I've seen on RCgroups in a while. It really does look like some kinda flying reptile - has a wing similar to a kind of spooky red vulture...

I'd like to submit an answer to the quiz: YES, it has "successfully flown" per the Wright Bros definition.

Cheers mate! Wonderful, creative, creation.
USKP01261: Please see my response to shamburg, below
Oct 20, 2021, 05:52 PM
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Answer to the Quiz Question


Quote:
Originally Posted by shamburg
Betting YES.

I've read a couple articles about a mix of wash-in, wash-out, dihedral, and anihedral making for favorable roll-yaw coupling and lateral stability on a flying wing. Have been poking around with the numbers for a 60" version of this, but it uses more dihedral & anihedral and avoids most of the tail. Goal is to mimic a frigate bird silhouette from all aspects as much as possible. Definitely a fun art & design project.

May crib notes from your picture on structure. It's a pretty bird.
I designed and tested P-RIX during the Spring and Summer of 2020. When I posted the Quiz Question, I of course wanted the answer to be YES, and my (faulty) memory thought the answer was YES, but when I reviewed my notes from flight testing, I was reminded that the answer to the quiz question is NO; P-RIX never flew "successfully" as it is shown in the pictures. Those were taken before any flight trials. As shown, my attempt at a Bell-shaped lift distribution, with upwash at the tips, DID manage to keep yaw under control, and the plane would glide out nice and straight, with power-off hand launches. The ailerons as shown kept the wings level, but the plane would not turn at all.

But my faulty memory distinctly remembered that I flew it around successfully for 3 or 4 flights. So what happened? It DID fly successfully after I changed the flat tail to a V-tail AND made the ailerons a little bigger. But it was pretty whacky and needed constant attention. Maybe I would have tried to continue development, but given the fact that I didn't really know what I was doing in the first place, I stopped trying to get it to fly better.

The P-RIX wing does not have much dihedral; I didn't think it would need it. Analysis in XFLR5 said it would be stable, but I don't think that was the final word.

Shamburg, if you ever get that frigate bird flying, I would certainly like to see and hear about it. Birds like that are absolutely amazing, and inspire me, too. Nice to experiment with a smaller model, as you say. If I try any more bird stuff, it will be with much smaller designs. You mentioned the wing on P-RIX. I was happy with its weight and structural integrity--plenty strong and light, no flutter. The spars are capped with about 0.030-inch-thick carbon. Ribs all had breakaway tabs on the underside so that the wing could be built on a flat board and still allow for a varying twist and incidence schedule. Wing was designed in CAD so as to be able to find straight paths for the spars to run out through ribs that varied all over the place in incidence, size and sweep--probably easier for the people making such wings with foam. I still have the wings--pretty to look at, but I don't know how to use them!
Oct 20, 2021, 08:30 PM
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P-rix


Wow. Hearty cheers none the less, mate! 110% u-neek and 110% bold . Those P-RIX wings are a thing of beauty....I would vote to repurpose the wings somehow and try to get 'em back up in the air. I can't give much useful suggestions tho - most of my experience is with a heavily dihedral/polyhedral RES type ships (and mostly kit based). But, it seems that there are quite a few of non-dihedral/minimal dihedral sailplane examples in the slope soaring realm that do quite fine. Sounds like going "v" tail was pretty successful.... The P-RIX could fly again! I hope!

Speaking of Frigate and being inspired by flight of birds, there was a recent thread where another Frigate/bird inspired sailplane design was discussed. Antonio Carlos Martins was also inspired by nature there's a link to an article and whatnot if you're curious: https://www.rcgroups.com/forums/show...ratch-build-3m
Oct 21, 2021, 06:37 AM
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Thanks for comments on P-Rix, and for the link to the Frigate. Frigate is beautiful--just seems like it might tip stall easily with those pointy wingtips. I think my next venture might be some sort of 3M.


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