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Author Topic: Caproni CA60 Transaereo  (Read 453 times)
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sprogs
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« on: February 14, 2022, 12:33:57 PM »

Okey-dokey !
I love this aircraft deeply. I think it is as beautiful as a Galleon, but I'm not sure about it's aerodynamics from a modelling point of view.
I don't know if any of you are familiar with "White Wings " paper aircraft, but they were great fliers and one had, if I remember rightly, five tandem wings. It flew wonderfully.
So, how would this relate to the Ca60 with three sets in tandem ?
The five wing tandem had decreasing incidence front to rear. Would this be correct for the ca60 ?
I would appreciate any help on this one.
Liz.
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msc
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« Reply #1 on: July 18, 2022, 09:09:23 PM »

There are two issues I can think of regarding incidence angles for each wing.

For stable stall recovery the front wing must stall first so should have a higher angle of attack relative to the other wings.

Each wing will create a slight downwash affecting the relative angle of attack for the following wings. Depending on the wing spacing this downwash may bounce back up by the time the next wing comes along so I’m not sure if a following wing at the same incidence angle would see a greater or lessor angle of attack then the front wing.

I suggest building a simple chuck glider with three tandem wings and adjustable incidence for at least two wings then see what it takes to trim it out.

Mike
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sprogs
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« Reply #2 on: July 23, 2022, 01:40:05 PM »

Thanks for the input Mike.
My thinking is that not only is there the downwash to consider, as you say the stall to take into account for stability, but what about CG ?
I'm not even sure where to start !
If I put the Cg under the middle wing, the reduced efficiency of the rear wing due to downwash, will mean that the front wing is more heavily loaded and should stall first.
If I put the CG further forward, where I would normally put it, I'm going to have to take into account the downwash to calculate the position.
What if I ignore the middle wing and treat it as either a canard or a tandem wing ? Would this make it easier to think about ?
Sory if this seems a bit wandery but I am well out of my depth.
Liz.
P.s. Just thought, what if I made a chuckie WITHOUT the middle wing and trimmed it for that ? I think I'm going to start there.
Liz.
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msc
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« Reply #3 on: July 26, 2022, 11:27:19 AM »

The reason for a chuck glider is to experiment without fear so you don’t need to overthink the starting point.

My vision of the chuck glider would be to skip the triplane aspect and give it three simple wings with a top view much like the Ca60. A simple stick for the body. The rear wing mounted flat to the stick. Give it a vertical fin or two either on the rear wing or on the stick in front of or behind the rear wing. The center and forward wings get held on with rubber bands so it’s easy to shim the incidence angle of them. Start with 2 or 3 degrees on the front wing and about half that on the center wing. Give it a movable weight so you can adjust the CG.

Assuming three wings that are the same size and evenly spaced the CG will be somewhere near the center wing.

Because the front wing is at a higher angle of attack it will be carrying slightly more weight so the GC will need to be a bit forward. I’m guessing no further back then 25%  cord of the center wing and no further forward then one cord forward of the leading edge of the center wing. I would start out near the leading edge of the center wing and give it a gentle toss in level flight. If it wallows and falls to the ground move the CG forward. If it dives move the GC back.

Keep moving the CG back until stall is achieved then move the CG a bit forward of there. It helps to pick the speed up a bit but not into a dive. Full size gliders typical achieve their best glide slope at about 1.5 times stall speed and minimum sink rate around 1.3 to 1.4 times stall speed.

I’m optimistic what I described will at least achieve a stable glide when you find the best CG. Things I would try after that would be no shim on the center wing and keep reducing the front wing angle until the stall recover degrades. Could try it with no center wing. Keep trying different shims on the center and front wing to find the limits of stability or points of better performance. Changes of wing angels will likely require re-triming of the CG.

As far as wash angels are concerned I’m sure it varies with wing spacing, cord, and reynolds number. I expect it goes down, then up, and could be at any point on it’s next oscillation before the next wing comes along.

You can save the serious thought about physics for trying to understand the response to trim changes. You don’t need to know all the answers before you can have fun tossing a toy around.

Whats your wildest plan for a model if you sort out the trimming? Taking liberties with the powerplants the connecting booms could house two rubber motors to fly it as a twin or make it 4 motor with 2 pushing and 2 pulling. 8 pager motors would give it the best scale look. Extreme crazy thinking would be to imagine using 8 of the Gasparin V-12 CO2 motors. I always have wanted to build a successful ROW model.

Mike
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sprogs
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« Reply #4 on: August 10, 2022, 12:31:54 PM »

Thanks Mike.
I appreciate your input and I'm going down the tandem monoplane route as you suggested. I'm a very slow worker so don't hold your breath but I'll keep you informed as I go.
Thanks again.
Liz.
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kittyfritters
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« Reply #5 on: August 16, 2022, 05:22:54 PM »

This is an absolutely insane project...I Love It! Grin

KF
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TimWescott
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« Reply #6 on: August 17, 2022, 01:35:01 PM »

I absolutely concur with making a chuck glider: it's what I would have said.  I might even go as far as following up the three-wing chuck glider with a 9-wing one, or a 9-wing thing built up of foam or sheet for further testing. 

Find a happy medium between incidence and CG -- more forward CG demands more incidence, but the combination is more stable.  More backward CG means the plane is less sensitive in pitch to extra power (this is why no-auto-surfaces free flight planes have such seemingly insane rearward CG) -- but it means the plane is less stable, and way more sensitive to changes in incidence, whether you put them in or they were put in by humidity or a hard landing.

At least one of the articles that I read about the CA60 attributed the crash of the prototype to the CG being too far back -- it's hard to say if that was really the problem, or just arm-chair engineers looking at the symptoms.

Apparently multi-wing aircraft like this don't recover from spins very well, so go easy on the aerobatics.
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sprogs
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« Reply #7 on: August 17, 2022, 02:40:23 PM »

As far as IU can understand, the crash was caused by the ballast shifting. It had been loaded to simulate the passengers, but not apparently securely enough.
Caproni had ordered that it was not to be flown without his presence and permission, but was apparently ignored.
I would not have liked to explain the crash to him !
I've been having problems with my hands so haven't been able to work on it, but hopefully I'll be able to get something in the air soon.
Liz.
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