Nice new Duck there Mr. Canard Addict. I'm still flying your D squared plane...

Small world , I have a Singer SM1500 .

What a great display of canard material and comments including some youthful reflections of motoring adventures! Memories of cars and motorcycles are dear to my heart. Nick and Dereck, you two have designed and built so many models that you must feel as if it is all over, but in my mind it seems a great time to really get turned on and see what develops.

Steve, I am absolutely thrilled that your D Squared is still flying for you. It took a while for me to realize that on landing, the flat bottom of the main wing needs to be parallel to the ground in it's normal nose high gliding position. It was easy to force the nose down like a trike trainer and hop along rather than to touch down first on the rear wheels.

In order to tighten up the flat spin on the Delta Duck, the rudder is now at 125% from 100% epa. The axis of rotation may not be through the fuselage as Don said and may never be until the rudder assembly is moved forward. A true flat spin may be harder to terminate.

I am delighted that the thread now contains such a large amount of aero information that it seems to be gaining in the daily view count. Each of you contributors deserve many thanks. If you will click on the 6800 replies, you will see every person who has replied since the beginning and the total replies they have made. Please forgive me for being uninformed but I just now learned about this.

Charles

Lake Flyer

Small world , I have a Singer SM1500 .

I bought one of those for spares for my Roadster - exactly the same engine. Column change and a bench front seat, a real passion wagon. You've still got one! They must be rare, specially in Canada.

Charles I think the Twinkle was designed by TheKM, who was contributing to this thread back in Jan 2007, probably other times too. He attributed the original idea to Laddie and the NorthStar, just as Steve, Jetset44 did with his Polaris. Somewhere in his thread about the Twinkle, TheKM referred to that long nose as being a bit like a canard. That was definitely the first time I'd ever heard of a canard.

cheers

Nick

This is a Steven Wong design of the COZY MKIV made of 5mm depron. It is lightweight, but somewhat fragile. I added landing gear and extra weight and bigger motor. It originally had a "Full flying" canard, it was horrible. I chaged it out to a more conventional stab elevator arrangement. Now it flies good enought that I went ahead and painted it. So maybe some inflight photos soon.

Roger

Thanks for showing, Roger. Canard control by moving the entire wing, depending on it's size and speed can be tedious. Using a tiny end point adjustment setting plus exponential may work well. For a new design it could be really helpful to find the perfect angle of incidence for the wing and then lock in in place and add elevators. My initial design was with a fixed angle with canard area ratio to the main wing as recommended by Andy Lennon. Area has been added to my canard wings but never taken away.
I would welcome more views of your work.
Charles

Charles - By the time I joined in with this thread, you guys had more or less settled on a canard of 20% of the wing area with a positive incidence of 2 degrees. I'm not sure of the optimum moment, some of the most successful flyers have had pretty long snouts.

That rule of thumb has worked well for me for a wide range of models. I've never felt the need to try a "live" canard, but I do like control panels that are at least 25% of the total canard area.

Then, suddenly you came along with the Delta Duck, much smaller canard and very little moment so you can't really say you've never taken away from your canard wings. I had to give it a try. There's no doubt that it needs elevons, but it's not just a flying wing with a fancy nose appendage.

My Polar Duck uses the Delta Duck main wing, but a regular canard with a reasonable moment. It's working really well now that I've found an optimum incidence for the tail stabiliser, which is fixed at -2 degrees. The CG is 10mm back from the one recommended in the CG calculator (ignoring the rear stab). No elevons.

I'm managing inside and outside loops, inverted flying, high alpha almost hovering. Just beginning to get confident with it. She glides and lands very well. I can adjust the speed with the elevator without fear of a vicious stall. By addng a little throttle, I can land with a high alpha and quite a steep descent.

Long may it last!

cheers

Nick

Those are rules of thumb, but they are not based on any particularly "sound" science.

There is nothing "special" or "optimum" about that particular area ratio, or that particular incidence, or that particular moment, independent of the context of the other parameters of the design. They do influence each other, but each has other parameters whose influence is at least as important to them. Only by considering all of those parameters, as well as all of the other design parameters, together within the context of that particular aircraft's mission profile, can you make any sense of it all.

The required incidence is more strongly affected by other parameters that you are not including, things like the airfoils of the wing and canard, and their planforms, stall characteristics, the canard moment arm, etc..

As far as area ratio, that is meaningless without also considering the moment arm as part of the equation. As far as optimum, you can get better efficiency by making the canard somewhat smaller than 20%.

It's like that old wives' tale about "square" props (i.e.: diameter equals pitch) being more efficient; just because something seems to make sense does not make it actually true. In fact, it could be quite the opposite.

Be very careful of rules of thumb, they are one of the primary habitats and hiding places of the "engineering sacred cow". If you take the time to hunt through those habitats (finding the true optimum, vs. what seems like at first glance ought to be the optimum), there could be some very tasty barbeque on your menu. And yes, I speak from considerable first-hand experience on this.

Don

This is what I posted in Sept 08

My brain hurts.

...................

And I have learnt a great deal from earlier posts on your excellent thread as well as the recent conversation with Don and John.

Fortunately, while there are, undoubtedly, optimium solutions, there seems to be quite a wide tolerance, judging by my planes.

When I've crashed them, it has been mechanical or electrical faults, pilot error, eyesight. Only by flying with the CG too far back, or turning without spare energy have I had an unmanageable plane.

Would you say that I get a wider margin for error by keeping the wing loading as low as possible?


NIck

Nickchud

Then, suddenly you came along with the Delta Duck, much smaller canard and very little moment so you can't really say you've never taken away from your canard wings. I had to give it a try. There's no doubt that it needs elevons, but it's not just a flying wing with a fancy nose appendage.

Nick, I should have said that on a given model the canard area has never required a reduction in area but an increase to perform better.

On models with long moment arms for the canard like the Georgia Goose, I used 3.5 more degrees on the canard than on the main wing to assure that the canard wing would stall first. My intuition calls for a gradual reduction in canard incidence as the moment arm decreases. In the case of the new Duck, does the main wing really care if the canard stalls? It is there to influence the angle of attack of the large wing and to give front end steering.

Don Stackhouse

As far as area ratio, that is meaningless without also considering the moment arm as part of the equation. As far as optimum, you can get better efficiency by making the canard somewhat smaller than 20%.

Thanks Don, for your usual first class observations as in the above.
Your comments have been a great help to me along the way.
Charles

Nickchud

Would you say that I get a wider margin for error by keeping the wing loading as low as possible?

Yes!! Lighter and slower will take my vote for safer performance. The Reynolds number rules.
Charles

Originally Posted by nickchud

Then, suddenly you came along with the Delta Duck, much smaller canard and very little moment so you can't really say you've never taken away from your canard wings. I had to give it a try. There's no doubt that it needs elevons, but it's not just a flying wing with a fancy nose appendage.

I think the reason the delta duck works with the short canard moment-arm and small canard area has a lot to do with the symmetrical airfoil on the main wing. I'd even go so far to say some canard designs using flat bottomed airfoils would need less decalage angle if the main wing airfoil was changed a semi-symmetrical or fully symmetrical one. With a less cambered airfoil on the main wing I believe it is quite reasonable to reduce the canard moment-arm, canard area or decalage angle.

I agree with Don that smaller canard area can potentially achieve greater efficiency but it requires a well optimised design to realise that gain. If the design isn't well optimised there could be limitations on other important parameters such as stall speed and elevator authority. I also read above that we should consider the mission profile in the context of the design. On that basis it sometimes won't be an issue if the efficiency is compromised by adopting a conservative design with oversized canard area.

Originally Posted by nickchud

My Polar Duck uses the Delta Duck main wing, but a regular canard with a reasonable moment. It's working really well now that I've found an optimum incidence for the tail stabiliser, which is fixed at -2 degrees. The CG is 10mm back from the one recommended in the CG calculator (ignoring the rear stab). No elevons.

I'm managing inside and outside loops, inverted flying, high alpha almost hovering. Just beginning to get confident with it. She glides and lands very well. I can adjust the speed with the elevator without fear of a vicious stall. By addng a little throttle, I can land with a high alpha and quite a steep descent.

Congrats on your success! It seems like you have come up with a well sorted 3-surface aircraft. Adding the rear stabiliser allows a more rearward CG location which we might expect to allow more elevator authority from the canard. I think your canard area is only around 18%, so the achievement of good control over a very extended flight envelope seems to be a very good achiement. Its especially interesting that the model is without elevons and using a fixed rear stabiliser. A video would be nice, but in the mean time its good that you are enjoying the model. Well done!

From Nick

PS Dereck:
I drove to Stranrar in 1970 in a 1955 Singer Roadster 4AD with a bunch of student friends to tour N. Ireland. We could have been on the same trip! We spent the night before sailing camped by Loch Lomond. Someone lent us a frame tent, we'd never seen it before and we didn't try and erect it till after midnight. You will guess, correctly, that we slept in the open air.[/QUOTE]

We went just before Easter, made the drive in one day. Somehow, we got four of us, one rider's father, four bikes, several pairs of spare wheels and our clothing into my four door Moggy and a Moggy Minor van, ex Post Office.

'We' were the four man Hull Brewery / Hull Coureurs Cycle Racing Team, one of the first sponsored amateur cycling teams in England. The aim was the four day long 'Tour of Northern Ireland' AKA the McArdles Beer Race. Four stages, around 60 - 70 miles each, around Northern Ireland, and a short lap 'criterium' around the seaside town we stayed in one night.

Seeing as the competition included the likes of a four man squad from York who went on to represent England in the Olympics, we got wasted! My dubious claim to fame was some lap prizes in the 'crit' and a high finish in it - climbing Irish mountains wasn't my style, but racing around a half dozen corners in a half mile lap for 20-odd laps was more like it.

Due to my inevitable lack of car skills at the time, we spent the drive there and back replacing engine oil that probably hadn't been changed for a long while...

Halfway back, I figured out how to turn the heater on too.

End of non-canard rambling, honest.

D

Non-canard ramblings..... all part of the community.

Mission profile - I accept that gliders are a whole different ball-game. But anyone thinking of an own-design canard, or a build from 3-views should not be put off by too much sophistication.

My point is that, with low wing loadings and high power-to-weight ratios, almost anything will fly as long as it balances. (ed: also as long as there's more vertical and horizontal surface behind the CG than in front). Just look back over the pages of this thread. Plenty of planes, like The Dark Angel, have a 6mm flat board airfoil and the Slow Stik is seriously under-cambered. There is any number of possibilities and inventive contributors.

Airfoils - My own personal favorite is the symetrical one used by the Delta Duck : 10% thickness, or the S3021, which John recomended for the Starship: 10.5% thickness and very nearly symetrical. For the canard, something classic like the Clark Y but thinner: 8% seems to get good, predictable results.

Here I go - getting more complicated, sorry.

cheers

Nick

Dereck, A great story which I thoroughly enjoyed partly because it painted pictures in my mind of a place never visited. I envy the bikers around here for their powerful legs.

John 235

I think the reason the delta duck works with the short canard moment-arm and small canard area has a lot to do with the symmetrical airfoil on the main wing. I'd even go so far to say some canard designs using flat bottomed airfoils would need less decalage angle if the main wing airfoil was changed a semi-symmetrical or fully symmetrical one. With a less cambered airfoil on the main wing I believe it is quite reasonable to reduce the canard moment-arm, canard area or decalage angle.

John, This quote and your comment on the no bounce Duck landing limited my sleep to 3.5 hours with another 1.5 hours spent tossing and trying to analyze the models flight characteristics. Both airfoils are symmetrical and have zero lift without positive angle of attack. the main wing is at zero incidence, the canard is at 2 degrees and the motor's thrust line is at 2 degrees negative. At top speed of about 55 mph, the canard lift is strong enough to overcome the down thrust and to control the rear wing well. At 25 to 30 mph landing speed the Duck's fuselage holds parallel to the ground and follows a trajectory of a straight line which I would estimate at around 20 degrees to the ground. This would make the angle of attack around 20 degrees.The descent rate may be more than one foot per second and requires rotation to avoid damage to the landing gear. I reviewed the video on page 318 and repeated the landing many times by clicking the mouse arrow on the moving time bar at the bottom of the picture. The study is meaningful because the air was dead calm with temperature in the low 60s and great camera work. The model was balanced level and since the attitude of it was level on approach, the center of lift must have been at the CG. My head is spinning wondering if performance could be improved with a higher lifting canard airfoil with smaller area? Nick, didn't you change the front airfoil on your latest?
Charles