Thread Tools
Mar 18, 2019, 06:52 PM
Everything's A Composite
Knoll53's Avatar
Thread OP
Discussion

HyperPlank


It just came to me out of thin air.........................and all the other planes just like it.

Central elevator at 10% of wing span should provide fine pitch control with standard servo.
Lots of aileron.
This aspect ratio should be good for 60" span.

Kent
Sign up now
to remove ads between posts
Mar 19, 2019, 02:45 PM
Registered User
EdSoars's Avatar
It will work fine, as one of my Tiger Moth variants used a simpler (cruder?) system and it worked well. The extended chord is a good idea, somewhat like the Marske Pioneer uses with a highly tapered wing with extended elevator surfaces.

The 3-servo Tiger Moth had a 33%-span elevator, and it worked great for speed trim, but using it for up trim wasn't so good, as it effectively washed-in the elevons, which created a tendency to tip stall. Your 10% chord elevator hopefully won't have that problem.
Mar 19, 2019, 03:36 PM
Everything's A Composite
Knoll53's Avatar
Thread OP
Quote:
but using it for up trim wasn't so good, as it effectively washed-in the elevons, which created a tendency to tip stall.
Oooooooooooh no.........tip stalling is not good. I get the washin effect when nose up is pulled. In this scenario the PW51 at the tip will be unaltered with all elevator force coming from the root panel.

A standard 2 servo wing with full span elevons would be deflected up for nose up, thus increasing reflex. I'm guessing that the reflexed profile would have better stall characteristics.

Also high taper ratio, between the giant root panel and the tip will promote tip stall. High G banked turns could be a problem.

Maybe I should rename it HyperStall.

The landings will be have crow programming with the central flap dropped way down the ailerons kicked up with mixing to balance. So landings will at least have increased wash out. Indeed if it turns out to be a tip-stall-devil, I could dial in some washout and fly it like that. This would be a draggy configuration........

So now you've scared me and I'm even more interested in building it. Maybe there are some tip vortec generators in my future.

Considering the issue you bring up, maybe a better configuration to combat tip stall would be a 4 servo wing with outer elevons and inner aileron/flaps, which is the common configuration. Oddly this didn't help me on the Plank 2.5 project, which had a bad tip stall problem.

Thanks for the heads up.

The hope IS that with all of the elevator coming from the root panel, the majority of the wing is left flying with a higher CL, since it does not need added reflex to achieve higher AOA.........................unless I'm missing something.

BTW, the little mock made clear to me that the root panel may be too small, so now I am going with 15% wide root panel. see attached.

I am sure that I'll get a chance to test the high G turns inasmuch as I am putting in a ballast box.
Mar 19, 2019, 08:34 PM
Everything's A Composite
Knoll53's Avatar
Thread OP
15% root panel.
Mar 21, 2019, 10:39 AM
Everything's A Composite
Knoll53's Avatar
Thread OP
OK, this plane is just too ugly.

Same aero concept, new look.
Mar 22, 2019, 02:19 PM
Living on the Dark Side.
guitarcher's Avatar
For what its worth Kent, having flown many PW51 planks I have never experienced tip stall unless trim is nose heavy and too much elevator is used in slow speed high bank turns. Your proposed new design with the centre section aft of the root chord may present some nose weight challenges depending on the weight you are aiming for .
Mar 22, 2019, 02:44 PM
Everything's A Composite
Knoll53's Avatar
Thread OP
Good to hear.

I'm shooting for 11oz./s.f. out of the box with a ballast option of 17 oz./s.f.
I will push the CG as far back as possible. Pitch control should be "enhanced" by the elevator being on such a big chord.
Smooth elevator control is the goal.

If it turns out heavier, that's fine. Just need another 3 mph of wind, which is free.

I am always happy to balance the plane with just the NiMH battery. I don't think that the nose is too long. I see a lot of weight behind the CG with a solid foam wing. It's always a guessing game.
Mar 23, 2019, 04:56 PM
Registered User
EdSoars's Avatar
She just keeps looking better and better! I follow with interest.
The 3-surface Tiger Moth had the best handling when I programmed up elevator onto the ailerons, and down onto the center elevator.

That led to the idea for elevons restricted to the outer half of the half-span, so that full up elevator created lots of washout and left the center with original camber.

That in turn led to the discovery that this layout produced slower stall speeds than reflexing the whole span. With your center surface left at zero offset, the hyper plank should hyper stall very nicely.
Mar 23, 2019, 05:00 PM
You know nothing....
Stuart A's Avatar
Quote:
Originally Posted by Knoll53
OK, this plane is just too ugly.

Same aero concept, new look.
That looks much better.The twin fin design always looks like overkill.
edit..

Looking at your revised design,could you keep the full width straight elevator and notch the fin to allow upward movement?Would that give better control?
Mar 23, 2019, 05:50 PM
Everything's A Composite
Knoll53's Avatar
Thread OP
Quote:
Originally Posted by EdSoars
. With your center surface left at zero offset, the hyper plank should hyper stall very nicely.
I certainly understand your thinking. We shall see. Sometimes I manage to shoot a little video. Initial programing will be as shown below. After flying, if I have any complaints whatsoever, I will try your approach. It's two, two, two planes in one! At least it is with a programmable Tx.

A top mounted wing should prove to be an easier build and a better potential for touch and goes. I'm building a little mock up of this version now to see if I can warm up to the looks.
Mar 24, 2019, 10:53 AM
Everything's A Composite
Knoll53's Avatar
Thread OP
Liking this a little better.

Similar to but different than the Pioneer.
  • less wing taper
  • less aspect ratio
  • different wing tips
Mar 24, 2019, 09:20 PM
Everything's A Composite
Knoll53's Avatar
Thread OP
the model is a version behind
Mar 26, 2019, 10:22 AM
Registered User
EdSoars's Avatar
Better and better!

Now reduce the center elevator chord at the tips to preserve the nice taper, and have a straight hinge line to simplify the linkage.

The hemp spar + hemp cloth Max Plank lingering on my bench uses a Fibonacci taper: 1:0.618. The Golden Ratio never fails to look right.

Or ignore the butt-ins like me and go build and fly the sucker.

ed
Mar 26, 2019, 10:27 AM
Everything's A Composite
Knoll53's Avatar
Thread OP
What? No sketch?
Come on Ed, get with the program!

I'm more likely to make the root panel longer, like a Hyperbipe fuse.

Your approach would certainly look better. Marske really nailed the look with the Pioneer.
Mar 26, 2019, 04:16 PM
Registered User
EdSoars's Avatar
Like this?

The shape of the elevator isn't very important as long as it's PURTY!

Or as in image 2, save yourself cutting 2 extra templates and an extra panel, and straight-hinge the center elevator.


Quick Reply
Message:

Thread Tools