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Author Topic: SO Wright Stuff 2020  (Read 3137 times)
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cxflyer
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« Reply #100 on: November 24, 2019, 03:48:01 PM »

Has anybody's team broken 1 min 30 sec on a Wright Stuff 2020-conforming flight? Just one flight, either circling left or right, not two flights together.

Inquiring minds want to know!    Smiley


There was a flyer on scioly.org that broke 1:50 to both the left and above 1:45 to the right.
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bjt4888
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« Reply #101 on: November 24, 2019, 04:56:14 PM »

What was the ceiling height?
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Maxout
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« Reply #102 on: January 10, 2020, 06:57:19 PM »

Here's the first installment in my 2020 Wright Stuff Review series, and the first thing I review is the rules set and what happened after it was released! Spoiler: it's not pretty.
https://youtu.be/cVXurA8nDrA
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flydean1
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« Reply #103 on: January 10, 2020, 08:47:09 PM »

I was thinking about getting involved with SO along with my EAA chapter.  Not interested.  Makes dealing with the FAA a simple process.
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Crtomir
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« Reply #104 on: January 12, 2020, 09:38:50 AM »

Here's the first installment in my 2020 Wright Stuff Review series, and the first thing I review is the rules set and what happened after it was released! Spoiler: it's not pretty.
https://youtu.be/cVXurA8nDrA

Wow!  That's intense.  This year's rules are making for a truly miserable experience.  Although, if our students do eventually get their planes to fly, they will feel a big sense of accomplishment.

Your explanation of the very narrow airstream from the small propeller interacting with the very small stabilizer seems to jive with exactly what our students have been seeing with their planes.   They can't get their planes to fly at all. They either climb up fast, stall, and then fall backwards to hit the ground, dive into the ground from the start, or start to climb but then start diving over into the ground.  No matter what they do, they cannot get their planes to fly very well.  The have tried moving the wing up or back on the motorstick, adjusting the wing incidence, adjusting the stab incidence, changing rubber thickness, changing propeller designs, and adding ballast to the nose.  There seems to be only a tiny margin where they can barely get their planes to fly.  And these are students that have been doing Wright Stuff for 3 years previously and so have a lot of experience.  They are getting so frustrated. 

So my question is, could it be that that highly nonlinear and sensitive effect of the propeller downwash airstream interacting with the small stabilizer is the cause of all this?  I noticed that our students are mostly using stabilizers with some camber, but a lot of the kits (from what I can see online) have flat stabilizers.  Also, the few planes I have seen in our group that have flown with any level of decency have used flat stabilizers.  Does having a flat stabilizer minimize the prop downwash-stab interaction effect you mention in your video?

And if that is the case, why not place your stab and rudder high up above the prop downwash?  Maybe we will try this. 
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Indoorflyer
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« Reply #105 on: January 12, 2020, 10:30:07 AM »

Something I've wondered about, but never personally tested, is a performance comparison of bottom-covered stabs (flat) vs conventional top side covered ones.   Dick Baxter's 'Pussycat' design has a stab with covering on the bottom (only).  It also has twin fins...
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bjt4888
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« Reply #106 on: January 12, 2020, 10:48:40 PM »

Ctr,

Our airplanes are flying well, but this year’s rules definitely make trimming sensitive. We are flying about 35% static stability margin with about 4.5 degrees of decalage angle. So, quite safe in pitch stability. A shift rearward of even 1/8” in the CG, along with less decalage resulted in poor recovery from ceiling hits or bad air. A small shift forward in CG of 1/8” resulted in continuous slight nose-down flying during let down. This trim is a bit “draggy” but we are getting repeatable good flights.

I have posted (and Coach Chuck has pasted) a number of specific suggestions on the Scioly.org forum, based upon my team’s experiences this year, that some on the forum have found helpful.

We have tried several propeller styles (symmetrical, semisymetrical, flaring, etc.) and a number of pitch angles on each style) and are starting to get things sorted out. Managing climb rate with the small propeller is one of the key issues this year.

Brian T
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bjt4888
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« Reply #107 on: January 12, 2020, 10:50:05 PM »

...Coach Chuck “posted”, not “pasted”... typing too fast.
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Maxout
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« Reply #108 on: January 13, 2020, 02:18:47 PM »

I was thinking about getting involved with SO along with my EAA chapter.  Not interested.  Makes dealing with the FAA a simple process.

Coaching students is much easier than the stuff I'm dealing with. If you can find middle school students to get involved with, do so. The rules for ELG this year are a treat and result in very nice flying planes. Wright Stuff is a pain in the neck this year, but look at last year--the rules were a dream last year with planes that flew super easily. Get with a school that is serious about this and they'll do anything you want in return for your coaching. Not kidding--I get paid for a lot of the coaching work I do.

Wow!  That's intense.  This year's rules are making for a truly miserable experience.  Although, if our students do eventually get their planes to fly, they will feel a big sense of accomplishment. 

Yup. It's messed up. That said, it is possible to get the planes flying, at least so long as the air isn't blowing. If they had allowed bigger stabs and/or props, the rules this year would make for trivial trimming efforts though, and the top flight times would be only a little longer.

Your explanation of the very narrow airstream from the small propeller interacting with the very small stabilizer seems to jive with exactly what our students have been seeing with their planes.   They can't get their planes to fly at all. They either climb up fast, stall, and then fall backwards to hit the ground, dive into the ground from the start, or start to climb but then start diving over into the ground.  No matter what they do, they cannot get their planes to fly very well.  The have tried moving the wing up or back on the motorstick, adjusting the wing incidence, adjusting the stab incidence, changing rubber thickness, changing propeller designs, and adding ballast to the nose.  There seems to be only a tiny margin where they can barely get their planes to fly.  And these are students that have been doing Wright Stuff for 3 years previously and so have a lot of experience.  They are getting so frustrated.  

Sounds like you need to move the CG forward. What I've taken to doing is to put all the ballast on the nose of the plane, and then slide the wing forward until it balances at 45% chord for biplanes, 55% for monoplanes. Add incidence until you get a good nose-high cruise going--don't even try for a climb initially, and start by trimming for left circles. Once the plane is flying in a stable manner, add more turns to look for a climb. Start adding downthrust if you see any stalling at higher power settings. If as you add left rudder to get that left turn going, the model starts to crank in, add a small amount of washin to the left wing and you should see a nice, stable climb. After that, try for a right turn. You'll *usually* need more right rudder than you did left, and the pitch trim may change, requiring additional stab incidence which must be documented so you can get repeatable results.

If all else fails, buy the Lasercutplanes.com kit which literally flies right off the board after you add a little incidence under the wing (I also needed to shim the stab for some extra incidence when flying to the right). It's a weird plane but it flies well.

-Josh
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Crtomir
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« Reply #109 on: January 20, 2020, 09:55:25 AM »


Sounds like you need to move the CG forward. What I've taken to doing is to put all the ballast on the nose of the plane, and then slide the wing forward until it balances at 45% chord for biplanes, 55% for monoplanes. Add incidence until you get a good nose-high cruise going--don't even try for a climb initially, and start by trimming for left circles. Once the plane is flying in a stable manner, add more turns to look for a climb. Start adding downthrust if you see any stalling at higher power settings. If as you add left rudder to get that left turn going, the model starts to crank in, add a small amount of washin to the left wing and you should see a nice, stable climb. After that, try for a right turn. You'll *usually* need more right rudder than you did left, and the pitch trim may change, requiring additional stab incidence which must be documented so you can get repeatable results.

If all else fails, buy the Lasercutplanes.com kit which literally flies right off the board after you add a little incidence under the wing (I also needed to shim the stab for some extra incidence when flying to the right). It's a weird plane but it flies well.

-Josh

Thanks Josh.  I ordered three of the Laser Cut Planes kits and a couple of the students built them in about 1.5 hours.  They really enjoyed the build, especially the unique prop design.  And you were pretty much correct when said it flies right off the board. They didn't have any of the problems that I described with their earlier planes.  They don't have them flying perfectly yet (some climbing issues to work on), but I can tell you that their flying experience was a lot more enjoyable than it has been all year.  Now, thye can concentrate on the "normal" trimming process and rubber band (thickness/length) selection.  Their spirits were high and they were so much more enthusiastic about flying again.  Thanks for suggesting that.

I think what we are finding is that the plane needs to be light enough so that a lot of weight (built-in or added ballast) can be put at the nose to move the CG very far forward.  Otherwise, you run into serious stability issues.  That's my feeling and seems to go along with your advice. 

Last year, we ordered some of your Wright Stuff kits and the students enjoyed the simple, but very effective design.  It's nice to see that there several expert flyers providing good quality kits for Science Olympiad flying events.  The kids often use them as a good starting point and then often start doing modifications throughout the season.
 
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