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Nieuport flick rolls at top of loop

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Nieuport flick rolls at top of loop

Old 07-15-2020, 01:55 AM
  #26  
UStik
 
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Originally Posted by cutarug View Post
I have a 1/3 scale pietenpole that is very scale in power and virtually stationary at the top but it does not flick like the Nieuport.
Now I remember you mentioning the biplane's incidence angles. I think the stall initiating the flick could have to do with that, but it would still require that it's an inverted stall (that is the airplane is borne by its wings and not by centrifugal force). Inverted, the upper wing is now lower and the lower wing is upper. The upper wing stalls first and now it is the back wing, meaning the remaining lift is more foreward (in front of the C/G) what makes the stall self-reinforcing so the slightest onset will cause it.

P.S.: Only later I remembered that you mentioned your D7 not stalling like the Nieuport. That's tough because their configuration is very similar. Could just be a different airfoil, but I would rather assume that the Nieuport's elevator power is scarce, the reason why still to find out. It seems to need full up elevator just to keep the loop's upper part round or it would climb up in a straight line until it runs out of speed. (I would try that out.)

Last edited by UStik; 07-15-2020 at 05:28 AM.
Old 07-15-2020, 04:52 AM
  #27  
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Originally Posted by cutarug View Post
Diffidently not overpowered in fact it needs a dive to pick up speed to get it at a speed it will have any chance of doing a loop.
I have a 1/3 scale pietenpole that is very scale in power and virtually stationary at the top but it does not flick like the Nieuport.
An inverted coordinated level stall would break no different than an up right coordinated stall. An airplane can stall at any angle, attitude and speed. Cutarug, inorder to stop the guessing and armchair piloting, please have someone take a video of the plane doing the maneuver several times from different angles.
Old 07-15-2020, 06:30 AM
  #28  
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If the plane can barely pull through the loop due to being underpowered, then we're not dealing with a snap/flick situation. We're dealing with the plane falling out of the loop due to loss of airspeed (inverted stall) and probably being torqued around by the engine after which any self-righting characteristics will take over from knife edge onward. That condition would be aggravated by a design that tends to drop a wingtip; if there's any washout in the wings it will increase the tendency to tip stall when inverted.

I agree, a video of the phenomenon would be helpful.
Old 07-15-2020, 06:44 AM
  #29  
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Cutarug,

Besides adjusting longitudinal balance, please check lateral balance.
Old 07-16-2020, 06:22 AM
  #30  
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First off, that is a good looking N-27. I have a 1/4 scale N-17 myself. Speaking as someone who just pulled a kilogram of lead off of a 1/4 scale Camel, I can say that it is easy to get tunnel vision when chasing that last centimetre on the CG. We all get accustomed to the mantra that WWI airplanes are tail heavy and that is not without its merits but I concur with the thought that the airplane is nose heavy. I hope your nose weight is easily removable. In my case it was chunks of lead bolted to baffles under the cowl. I would say that the plan to incrementally remove small amounts of nose weight is the way to go. As you can see we all have our opinions but I would really like to hear how it turns out.
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Old 07-16-2020, 04:57 PM
  #31  
cutarug
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Thanks for the positive comments my first Covit project, we are now in lock down so no chance of testing it now.
I have had time to make a few changes though, steerable tail skid, bolly prop which gave me an extra 1 kg f thrust and made a jig to balance it properly.
Lots o 3d printed parts on this model, wheels, guns, pilot, cover plates windscreen etc.
I am confident it will be a better flyer now with the extra thrust.
Old 07-17-2020, 07:23 AM
  #32  
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A little off topic, but what is the engine on the Nieuport? I have en engine that would benefit from a similar propeller mounting.
Old 07-17-2020, 03:21 PM
  #33  
cutarug
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36cc 4 stroke Honda clone running straight petrol with wet sump. Plenty of mass so not much nose weight required. Very smooth running suited to this type of aircraft and scale like.
Best sound you can imagine!
Old 07-18-2020, 06:40 AM
  #34  
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Originally Posted by cutarug View Post
36cc 4 stroke Honda clone running straight petrol with wet sump. Plenty of mass so not much nose weight required. Very smooth running suited to this type of aircraft and scale like.
Best sound you can imagine!
Spiffy!, Is the propeller shaft a shop made item or is it a commercial product?
Old 07-18-2020, 09:38 AM
  #35  
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Anyone suggested at 2 or 3 mistakes high to dip the nose a bit to build up speed then roll inverted and see if you can hold it inverted. If you can hold it inverted without it flicking until it stalls I would think the wing geometry must be near correct. I have found too much elevator for a given CofG will cause a snap in just about any plane but usually when pulling out of upward of downward lines, but I have seen them in straight and level flight with too aggressive elevator moments.

Remember WW1 planes did not do round loops usually they were egg shaped at best and sometimes there was a near stall at the top with the airframe falling out of the loop.

Dennis
Old 07-24-2020, 08:56 PM
  #36  
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Cutarug, I'm thinking that jester is right and it's falling out of the loop due to insufficient speed. What's happening is that as you go over the top it stops pulling outward and the G load on the model goes negative. Like inverted flying negative. But not fast enough so it stalls and flicks out of the loop. Try a little more speed/longer dive and use a little extra up as it slows down to see if it makes it around.
Old 07-25-2020, 03:23 PM
  #37  
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Bruce, I would think if that were the case the airplane would not snap out of the loop but just stall. IMO pulling more elevator will only make the issue worse.
Old 07-26-2020, 09:11 AM
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I'm guessing that he may be confusing a "flick" with an inverted stall with wing fall off. Hard to say for sure without a video or being there.

I've never seen a situation where a model stalled due to high positive G and snapped out of a loop as it passes over the top. Oh sure, speed falls off but so does gravity. So I'm inclined to think that it's a lack of sufficient speed to do a nice clean arc over the top and instead it's running out of speed and being loaded inverted and perhaps stalling out before the nose is pointed back downhill.
Old 07-26-2020, 01:27 PM
  #39  
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Bruce, if Im not mistaken what we call a snap roll in in the states many others call a flick roll. That being said I have seen this issue many times in the pattern sportsman class. The sportsman sequence has a two consecutive loop maneuver that tends to bite newbie pattern pilots in the butt. Typically new guys to pattern have their controls set way too hot, add in that most R/C pilots set their CG too far forward. The end result is that some guys during that double loop will come into the first loop with plenty of speed but get off the power too much during the backside and get back into the power too late. Then trying to get through the second loop they pull too much elevator and the airplane snaps out of the loop. It's a combination of the three things, change any of them I.E. move CG rearward a smidge, reduce overall elevator throw or fly faster and the airplane stops snapping out of the loop.
Old 07-26-2020, 04:27 PM
  #40  
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Yeah, you're certainly right that this can be an issue. And it may well be what is happening. The issue we're fighting is that we weren't there to see what happened.

And ya, flick and snap to me mean the same thing.

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