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Old Jan 01, 2013, 08:52 AM
What could possibly go wrong?
nickchud's Avatar
Market Harborough
Joined Apr 2006
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An unusual and beautiful plane, expertly built!

I'm looking forward to seeing it fly.

Happy New Year!

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Old Jan 02, 2013, 05:39 AM
Student of Ivan
mountainman2442's Avatar
El Paso, Illinois
Joined Apr 2006
725 Posts
Trevor,
Watching quietly from the sidelines I always find your builds outstanding and never fail to learn something while reading them. The Aquabird is a beautiful airplane and Laddie ranks right up there with Ivan in designing so this will undoubtedly be a great flyer.

One thing that has always intrigued me was designs such as this that have anhedral built in the wing. I always expect planes with anhedral to want to flip over the "right way" whenever they fly however I'm sure this will be a stable flyer considering its designer.

Great job! I look forward to seeing the color scheme you choose for this beautiful airplane.

John
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Old Jan 02, 2013, 06:13 AM
Slip the surly bonds...
Sopwith Mike's Avatar
Christchurch,England
Joined Aug 2004
2,532 Posts
Quote:
Originally Posted by mountainman2442 View Post
Great job! I look forward to seeing the color scheme you choose for this beautiful airplane.

John
Me too - the Fleet Air Arm 1965 (alt) scheme should really set off the unusual lines of this model
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Old Jan 02, 2013, 06:43 AM
...design-build-fly-publish...
eye4wings's Avatar
Ware, herts. U.K.
Joined Sep 2008
3,367 Posts
Just picking up on John's comment about the anhedral, I have to admit to the same feeling. Logically in a bank the lower wing will lose some of its lifting area (relative to the vertical) while the higher wing gains as it reaches maximum at the horizontal. This would normally be unstable... BUT beyond the wing tip as we see it at present in Trevor's build, and beyond the float is a sharply dihedralled winglet section which will reduce the effect to a degree.

What will interest me is how different it will feel to the pilot going from models with positive stability to one that is (presumably) neutral.

Interesting that the anhedral of the Hawker Hunter was (I seem to recall) stated to be for improved stability, particularly near the speed of sound. Thankfully the Aquabird won't be travelling that fast!
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Old Jan 02, 2013, 07:38 AM
What could possibly go wrong?
nickchud's Avatar
Market Harborough
Joined Apr 2006
3,629 Posts
There are a couple of videos on Youtube..This one from 1993 looks very stable and a long glide when he cuts the engine.
Aquabird maiden flight (3 min 29 sec)
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Old Jan 02, 2013, 09:05 AM
Slip the surly bonds...
Sopwith Mike's Avatar
Christchurch,England
Joined Aug 2004
2,532 Posts
Orientation would be my concern - sometimes it was very difficult to tell which end was the bow and which the stern!
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Old Jan 02, 2013, 01:42 PM
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Steve Merrill's Avatar
USA, IL, St Charles
Joined Nov 2002
1,808 Posts
Thanks for the video. I have wondered about anhedral as well, but it seems to work very well. Here is a pic of an A-7 Corsair I am building. This was a very popular jet in the 1960's that flew very well with anhedral wings, and dihedral in the horizontal Stab
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Old Jan 02, 2013, 02:55 PM
build like there is no 2moz
wallis_100's Avatar
United Kingdom, England, Bristol
Joined Apr 2009
797 Posts
Quote:
Originally Posted by eye4wings View Post
Interesting that the anhedral of the Hawker Hunter was (I seem to recall) stated to be for improved stability, particularly near the speed of sound. Thankfully the Aquabird won't be travelling that fast!
You do indeed recall correctly.
The reason for this was to improve the control (by reducing the stability) in roll, which still keeping it positve.
The Hunters swept wing generates an 'effective dihedral' (approx 1 degree dihedral for 3 degrees sweep at the 1/4 chord), so the Anhedral was used to counter this.

scott
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Old Jan 02, 2013, 07:11 PM
We shall serve the Lord
kingsflyer's Avatar
United States, TX, Kingsland
Joined Sep 2005
4,979 Posts
Though the Aquabird has anhedral on the inner wing sections, it has a lot of dihedral on the outer panels. This will act to help stabilize the plane in upright flight.

McD
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Old Jan 02, 2013, 10:20 PM
What could possibly go wrong?
nickchud's Avatar
Market Harborough
Joined Apr 2006
3,629 Posts
If swept wings produce a dihedral effect, does the reverse delta produce an anhedral effect?

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Old Jan 03, 2013, 03:22 AM
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Trevorh's Avatar
Hampshire, U.K.
Joined Jun 2008
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Quote:
Originally Posted by nickchud View Post
If swept wings produce a dihedral effect, does the reverse delta produce an anhedral effect?

Interesting discussion. Where's Don Stackhouse when you need him!? I have to admit that, when contemplating putting this much effort into such an unusual build, the reputation of the designer was a significant factor. That, and the YouTube videos, of course.
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Old Jan 03, 2013, 06:29 AM
TonyS
United States, AR
Joined May 2010
570 Posts
Quote:
Originally Posted by Sopwith Mike View Post
Orientation would be my concern - sometimes it was very difficult to tell which end was the bow and which the stern!
I posted early in the thread, but will repeat...I have made many flights with buddies Aquabird (sheeted foam wing), in mostly all silver/aluminum color with red sponsons and dihedraled tail sufaces, without any difficulty in determining aircraft orientation.

Ignoring the aerodynamic theory discussion for a moment...with center of gravity near Laddie's designated point and controls throws set as specified on the plans, the Aquabird is a stable platform, capable of loops, rolls and inverted flight. The size of the loops will depend on power availability and, obviously, the pitch and roll rates will be relative to the amount of control surface deflection. Rolls are not axial and do require rudder and elevator input, but nothing excessive and comparable to nearly any scale-type general aviation or warbird model.

Wings level stalls were smooth and the nose dropped straight ahead with no tendency to roll. I did not try stalling in a bank and I have not tried spins with his plane.

I enjoyed flying his Aquabird. Unfortunately receiver battery failure caused it to be "re-kitted" this past August, with the foam wings converted to too many pieces to be rebuilt.

TonyS
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Old Jan 03, 2013, 06:35 AM
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Trevorh's Avatar
Hampshire, U.K.
Joined Jun 2008
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Thanks Tony - very reassuring. As a matter of interest, do you have any idea of the weight of the Aquabird you flew?
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Old Jan 03, 2013, 01:46 PM
build like there is no 2moz
wallis_100's Avatar
United Kingdom, England, Bristol
Joined Apr 2009
797 Posts
Quote:
Originally Posted by Trevorh View Post
Interesting discussion. Where's Don Stackhouse when you need him!?
The Simple answer is YES, it has to do with effective sweep angle, and sideslip component to the wing. This would result in it rolling out of a turn, as opposed to the roll 'in' associated with dihedral.

But thats enough of the science,.. it seems it flies fine so thats all that matters :-)
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Old Jan 04, 2013, 10:33 AM
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Trevorh's Avatar
Hampshire, U.K.
Joined Jun 2008
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Changing tack for a moment, I have just been looking again at the pics of his electric Aquabird that Laddie posted on page one of this thread and was wondering whether there is any provision for cooling airflow over the motor, ESC and battery?

On the i.c. version, the air intake is the black 'teeth' of the colour scheme and the air exits through the cowl side cheeks. However, I shall be dispensing with the cheeked cowl (as Laddie has on the e-version) so it is not obvious where to let the air out - clearly the usual practice of leaving the rearmost section of the fuselage bottom unsheeted is not advisable on this model!

I will be fitting a cockpit canopy of some sort just forward of the base of the fin so there is the option of ducting air out behind the cockpit along the sides of the base of the fin. This would be fairly inconspicuous and shouldn't be too prone to water ingress. However, I'm quite tempted to forget the whole cooling issue entirely. Well, not quite entirely - I would of course make sure that the motor and ESC were somewhat over-specced so they hopefully wouldn't work up too much of a sweat during a 10 minute flight, and I have never found heat build up in LiPos to be an issue.

Any thoughts?
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