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Jun 04, 2011, 07:29 PM
Registered User
OMG this priceless!

about washout for a long time people thought that washout was a compromise in efficiency but washout may actually increase efficiency because of the upflow in the wingtip area. a straight wing will means the tip is flying at too high of an of attack and therefore creating more drag not to mention stronger wingtip vortices. in reducing angle of attack to equal the loading of the rest of the wing or even reducing it to cause the root to stall first the lift vector is tilted further forward creating thrust which is efficiency! hey aren't the birds better designed than our best designs?

i started a canard wig but never got far with it, i'll go back to it one day.

the charles canard is the canard i like...mine would be a eurofighter style with a prop ahead to create vectored thrust(imagine lifting the nose and turning on a dime before liftoff!) and the canards about 30 degrees dihedral to yaw the nose into the turn when manuevering as canard elevons, (entire canard moving in roll/yaw and pitch) with a verylow aspect ratio or cropped delta mainwing to maintain lift at very high alpha due vortex lift.
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Jun 04, 2011, 08:24 PM
Registered User
another i want to return to someday, except tractor prop head of canards and maybe delta boxwing to give a more aft AC, balanced to have canards lightly loaded so they are 'control' canards.
Jun 05, 2011, 07:36 AM
What could possibly go wrong?
nickchud's Avatar
David
Quote:
the charles canard is the canard i like..
Is this the one you mean?

I agree completely with your approval of the cropped delta. I've built 3 of these, using the same wing each time and they've all been a blast Nor have I finished playing with this idea yet.

a) I haven't tried your idea of dihedral on the canard. I usually avoid dihedral, till now.
b) Can you get Depron where you live?
c) Balsa makes a very satisfying, robust build.

Cheers

Nick
Last edited by nickchud; Jun 05, 2011 at 10:09 AM. Reason: Oops! sorry
Jun 05, 2011, 01:15 PM
Registered User
That's the one!
Cropped delta; the vortices produced by the swept leading edge(+45 degrees sweep) need enough chord so they can re-attach to create a low pressure zone.
Canard; I rather the canard above to create mutual interference. It creates a slot effect and its wake is above the main wing. Also for a manned air vehicle(MAV) less visual obstructions.
Dihedral; increases 'proverse' yaw.
Can't get foam easily, dominica is full of wild balsa trees, I think I need to harvest a few!

The forward sweep of the revers delta does compound the anhedral effect!. Having the wingtip ahead of CG is excellent for using the winglet as ailerons or even canard like elevons to produce proverse yaw like the birds!
Jun 05, 2011, 01:53 PM
What could possibly go wrong?
nickchud's Avatar
If you search on rcgroups for "airboatflyingship" you'll find all sorts of interesting planes. for example
Jun 06, 2011, 04:59 AM
Registered User
Nick the Bateleur is amazingly stable in ground effect, video showed it reacting to the waves as it flew over them! Reminds me when I was doing ground runs on the model with the low set canards, the canards were free floating so that I could determine what its local airflow was so I could figure the incidence to set them at. I was surprised that they would point down about 60 degrees! pivot was set at 20% of its chord so the trailing edge being heavier would be lower when static.

It seems in strong ground effect the upflow just ahead of the wing is almost straight up! Maybe on the VLAR the lift increase by that strong upflow balances the rearward AC shift! Also the lift vector tilts forward making it fly faster.

With a canard as the nose lowers in GE due rearward AC shift the canard in that strong upflow could balance the craft as well as produce thrust!

Marijn what do u think?

Please pardon me for posting here instead of...promise I will next time.

Rgds david
Jun 07, 2011, 03:43 AM
Registered User
hoverman's Avatar
Hey Nick, any progress lately on the FS-8? Hope you enjoyed your trip.

@ Captarmour, I replied to your question in the other topic

Best Regards,

Marijn
Jun 07, 2011, 04:19 AM
What could possibly go wrong?
nickchud's Avatar

Back to business


Here are the control surfaces for the Flightsip. Sound only starts after 1 min, sorry, it's a new camera and I haven't worked it all out yet.
Flightsip control surfaces (1 min 48 sec)


The wing is parked up against the wall so that I could test the differential throttles with the rudders. It all seems to work as planned, surprise!

Some diagonal braces will be needed between those fins. I have been careful not to build too much re-enforcement. With Depron, you're always in danger of adding to the weight and merely moving the weak point to a new place. Shame I didn't think of passing the elevon servo leads down the middle of those cf tubes. If I get a successful maiden that will be one of the little jobs to do.

I don't want to fix the hull to the wing until I've completed the sponsons, so that I can be sure it'll float about right, with most of the weight taken by the hull.

After some more thought about washout, I think I'll set up the winglets with zero incidence and 20 deg dihedral. this will, in fact, give loads of washout since the main wing has an incidence of 9 degrees.

Cheers

Nick

PS I've just been reading back through several pages of the Ekranoplan thread. Sounds as if learning to fly this beast will not be as easy as I thought. First, those elevator throws will be far too much, so I'll reduce them by 50% at first. I don't have a recovery boat so the first tests will be on the playing field!
Last edited by nickchud; Jun 07, 2011 at 08:05 AM. Reason: PS
Jun 07, 2011, 10:48 AM
Registered FFF Addict
larryross's Avatar
Nick
You might try setting the high and low throttle on your ESCs to make sure they match before you mess with the trim.

Regards
Larry

Quote:
Originally Posted by nickchud
Here are the control surfaces for the Flightsip. Sound only starts after 1 min, sorry, it's a new camera and I haven't worked it all out yet.
http://www.youtube.com/watch?v=FCkSBAS-wQ0

The wing is parked up against the wall so that I could test the differential throttles with the rudders. It all seems to work as planned, surprise!

Some diagonal braces will be needed between those fins. I have been careful not to build too much re-enforcement. With Depron, you're always in danger of adding to the weight and merely moving the weak point to a new place. Shame I didn't think of passing the elevon servo leads down the middle of those cf tubes. If I get a successful maiden that will be one of the little jobs to do.

I don't want to fix the hull to the wing until I've completed the sponsons, so that I can be sure it'll float about right, with most of the weight taken by the hull.

After some more thought about washout, I think I'll set up the winglets with zero incidence and 20 deg dihedral. this will, in fact, give loads of washout since the main wing has an incidence of 9 degrees.

Cheers

Nick

PS I've just been reading back through several pages of the Ekranoplan thread. Sounds as if learning to fly this beast will not be as easy as I thought. First, those elevator throws will be far too much, so I'll reduce them by 50% at first. I don't have a recovery boat so the first tests will be on the playing field!
Jun 07, 2011, 12:00 PM
What could possibly go wrong?
nickchud's Avatar
Thanks Larry.

I've got the two motors matched as you suggest. It was when I inserted the elevon mixer into the circuit as per the drawing by boredom.is.me on the General Ekranoplan thread that the mismatch between the motors arose.

That was because I used the trimmer on my Tx to adjust the rudders before connecting the Y-lead and the mixer into the circuit. Fortunately, I can put the trimmer back to zero and use the physical adjusters to set up the rudders in the old fashioned way.

Cheers

Nick
Jun 07, 2011, 08:02 PM
Registered User
nick cant wait to c flightship in action!
Jun 08, 2011, 03:26 AM
What could possibly go wrong?
nickchud's Avatar

winglets


A busy evening yesterday!

To get the alignment right I used a spirit level. ie, before attaching the floats, stand the wing upright with the centre line vertical. Then make sure the wingtips are also vertical. I had to cut 10mm off at the leading edge, tapering down to zero at the TE. Promisingly, the same on both sides.

Then lay the wing flat, make sure the long trailing edge of the delta is horizontal. This means the square part of the wingtip is higher at the front by 12mm. So, a corresponding line was needed on the inside of each float in order that the winglet would be level from front to back.

Then I needed to go and have a lie down.

Phew!

Nick
Last edited by nickchud; Jun 08, 2011 at 03:47 AM.
Jun 08, 2011, 05:29 PM
Build straight - Fly twisty
Whiskers's Avatar
Wonderful! Wunderbar! Fantastico! Estupendo!
Or in Australian, Not too bad.
Jun 10, 2011, 06:27 AM
What could possibly go wrong?
nickchud's Avatar

Any advice


I was expecting to cruise gently at about 30cm altitude, but it wasn't to be. Either she stuck to the ground or left ground effect very quickly with disastrous results. Repairable, I have all the bits.

What if I increase the weight in the nose and trim the elevators up a little???

All suggestions gratefully received...
Flightship FS-8 (1 min 17 sec)


Here's what I was hoping to acheive..
New Airfish-8 (WIG craft) (7 min 48 sec)
Last edited by nickchud; Jun 10, 2011 at 06:41 AM.
Jun 10, 2011, 09:08 AM
Registered User
hoverman's Avatar
Haha EXACTLY what my results where in some cases, like a deja vu

It either skips like a stone..or jumps into the sky without return, stalls and crashes. Most of the times, the answer was simple, it's nose heavy! This sounds stupid, because the Out of GE flight at the end proved that it is more tail heavy than nose heavy.. well believe me it's nose heavy.

I'll try to explain. Wig's are longitudinally unstable because their CP moves forward during a in to out of GE transition, requiring a more rearward CG in GE than in out of GE flight. Nothing new

However, the way we stabilise these vehicles in order to be stable during the entire transition is completelly different from airplanes, something which is underestimated by most builders. As you know, the Stabiliser on a WIG is positivly lifting, meaning the CG of the entire vehicle lies somewhere in between the CP of the main wing and the CP of the stabiliser, NOT FORWARD of the CP of the main wing(as on an airplane)

Once the vehicle climbs, the CP of the main wing moves forward..increasing the PITCH UP moment..wanting to make your model flip backwards. However because the CP of this main wing lies in front of the CG, the total Lift reduction due too the disappearance of the GE creates a PITCH DOWN moment, which..yes..effectively is cancelling out the pitch up moment.

In order for this pitch down moment effect to be strong enough to cancell out the pitch up moment, the CG will have to be quite far rearward, and the stabiliser will need to create a lot of lift(hence the stabs are so big on WIG's). What you need to understand is that in order to achieve better longitudinal stability, you are moving the CG REARWARD.

So.. lets say you find that during the in to out of GE transition, it pitches up..you know you're not having enough longitudinal stability. If however you increase the Incidence of the stabiliser by a few degrees, and in order for it to still be balanced neutral you move the CG more rearward, it has now become more stable. The stab creates more lift, the percentage of the crafts weight beeing carried by the stab is now bigger, when the in to out of GE transition occurs the main wing looses lift. the stab is still lifting at it's 100%..voila the nose lowers itself.

You can see nearly every WIG as a sor of Tandem wing, only the front wing pair is effected by the GE.

Long story short, what is the stabiliser angle you're currently using VS the main wing angle ??

Marijn


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