Dec 01, 2013, 12:34 PM
What could possibly go wrong?
Market Harborough
Joined Apr 2006
3,179 Posts
Quote:
 those tips are "surfing" on the induced flow from the rest of the wing inboard of there
I like that. Does that take us back to geese in formation?

 Dec 01, 2013, 05:28 PM Registered User United States, OH, Bradford Joined Jun 2005 3,672 Posts Very similar effect.
 Dec 02, 2013, 08:49 AM Registered User Joined Mar 2011 706 Posts fantastic! keep it coming Don
Dec 02, 2013, 09:14 AM
Registered User
Joined Mar 2011
706 Posts
Quote:
 Originally Posted by Don Stackhouse Well, technically the Avanti is not a canard, it's a "three-surface aircraft". Te details of that vs more traditional "two-surface aircraft" are subtle, but significant. For that matter, from that point of view there is no such thing as a canard. There are one-surface aircraft (flying wings). There are two-surface aircraft (typical canards, tandem-winged aircraft, and aft-tailed monoplanes). The canard layout is simply one portion of a continuum that includes all three of those. While there are important differences in the way that things like stability and control have to be treated in different portions of that continuum, all three regions follow essentially the same set of equations. There are three-surface aircraft, such as the Avanti, but this category also includes things like aft-tailed biplanes. Then again, a typical flying wing, swept-style or plank-style, can be thought of as a variation of the two-surface arrangement. In a swept flying wing, it's typically the outer 20% or so of the span that acts like a conventional tail, so you can think of them (including for mathematical modeling and stability and control analysis) as an aft tail where the tail is cut in half and stuck on the wing tips. In a plank-style flying wing, the last 20% or so of the chord, the portion that is "reflexed", acts as a horizontal tail, and can be modeled as an aft tail where the tail moment arm is so short that the leading edge of the tail coincides with the trailing edge of the wing. The bottom line is that although, as usual, "the Devil is in the details", all aircraft arrangements follow essentially the same set of rules in the grand scheme of things. Just watch out for those details! And, for the record, I do have the beginnings of a full-scale Rutan VariEze (not LongEze) out in the barn. However, at this point the odds of ever finishing it are fairly low. The project got interrupted by an illness years ago,then by other factors, and by the time I was in a position to work on it again, my needs in a personal aircraft had changed. I have studied and experimented with a wide variety of canard aircraft models over the years, and do in fact have some in the works at present (nope, sorry, not ready for any public disclosure of any details just yet). However, they too are subject to the same limitations I discussed in my previous post, no worse, but no better. Quite honestly, at this point I'm finding flying wings (Prandtl/Horten/Jones style BSLD's in particular), and tailless designs in general, to be a much more promising avenue to explore. Much trickier to design (which is why we have not seen more of them), but they do indeed seem to have significant advantages over two-surface layouts for many applications, IF you do the details just right.
Don,

Have you done much work with close coupled canards? we spoke of this before but i cant remember if you actually designed and built close coupled canards.

For the many inefficiencies you have mentioned regarding canards, the only canards i would consider are the close coupled canards due to their beneficial interference.

a swept flying wing with close coupled 'control' canards, ie, no load except for control inputs, combined with 'short' elevons might be interesting. the problem though for transport aircraft is a tube is much easier to pressurize than any other shape, so for some time we will probably be seeing tube type fuselage aircraft with tails.
maybe we may see close coupled control canards, in addition to tails, to reduce tail down load for landing and takeoffs...

what about a 'wingtip feather' type elevon? that way a simple no twist wing could be built and use the the 'wingtip' to induce twist as well as control. if it is less than the wingtip chord and mounted aft it would be flying in a strong local upwash, making its zero lift incidence somewhat negative...

regards
 Dec 02, 2013, 10:16 AM InvDelta FwdSweep GEV Ireland, Cork, Model Farm Road Joined Mar 2013 2 Posts Hello Don, So, you'd think putting canards on my Wing-In-Ground-Effect (WIG/GEV) plane is not a good idea to prevent it from overbalancing when it leaves the Ground effect? I'm only at the design state, but it seemed pretty logical to me, not only for the fancy look... regards
 Dec 02, 2013, 10:23 PM Registered User Joined Mar 2011 706 Posts I can't say conclusively that canards help, I have had mixed results so far. What you are describing seems to be a too far aft OGE CG, which can be countered with a large tail, a canard may not help in that regard. IMHO a flying machine, GE or not, with a too far aft CG for OGE flight is not a safe vehicle. The ideal would be a vehicle that maintains height IGE but wants to nose down OGE due to a forward CG. A canard may help with such a vehicle.
 Dec 03, 2013, 02:50 AM What could possibly go wrong? Market Harborough Joined Apr 2006 3,179 Posts I still think you can get a good stabilising result by using a gyro on the elevator channel. Pitching up or down for any reason other than input from the Tx is corrected automatically. There's only one correct position for the CG out of GE and it's different from the correct position fo flyingr In GE. To solve this problem, the gyro could be used to move the overall Centre of Lift backwards as the plane leaves Ground Effect. An all-moving canard with a high Incidence IGE would automatically tilt downwards as the plane pitches up. Most of those ground effect vehicles are built with the elevator and horizontal stabiliser well up out of GE. I'm suggesting that the canard could also be in GE and would therefore lose some of its lift as the plane rises. How does that sound?
 Dec 03, 2013, 06:31 AM Registered User Joined Mar 2011 706 Posts lots of info in General Ekranoplan forum see also http://www.rcgroups.com/forums/showt...ral+ekranoplan Last edited by captarmour; Dec 03, 2013 at 06:38 AM.
 Dec 03, 2013, 01:58 PM Registered User Denmark, Capital Region of Denmark, Charlottenlund Joined Jan 2012 969 Posts FPV Canard Hi All, I'm new to this forum, but I have been looking into canard design principles after embarking on a FPV-canard project. I own a Sonic Liner, which I'm very fond of and only fly on clear and calm days: The Sonic Liner only flies LOS, though, and I want to try out the canard design for FPV applications. My idea is to put the cameras and VTx on the canard/front wing and the normal Rx on the rear to obtain a lower noise floor and get the camera away from the motor noise/vibration. I've purchased a set of replacement "warm-liner" wings/stabilisers from HK, and plan on building as sleekly as possible to get some speed into the platform. The main wing is 156 cm span and the canard is 50cm. I haven't decided on the length yet, but I will let the CoG calculations influence that (but it seems there is not much influence, really...?). The plane will be propelled by a 300 watt pusher outrunner and 8-9" high pitch folding prop. I expect an AUW around 900gr. including a Mobius HD cam and FPV gear. After going through some of the posts here, I have com to worry about the detrimental effects of the canard turbulence to the main wing. Will it help mounting the canard slightly higher than the main wing? (Like the Sonic Liner) Also, I was planning a single vertical stabilizer, but that would probably be sitting in the "canard air"? Maybe better to go with two stabilizers instead? Your comments are most welcome!
Dec 03, 2013, 04:28 PM
Registered User
Joined Jun 2005
3,672 Posts
Well, I've posted it here before, but one more time..

See attached picture. The wake behind a lifting surface is more than one span high. Moving the canard up or down a little will NOT get its wake clear of the wing. Just not practical.