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RV-10 VS Velocity (flame suit on)

flyingriki said:
@ notes to Daniel's theories:
1. If they are draggier why can they be so much more efficient? Never hear of 50 mpg in other common designs. How many O-235 planes have flown from Phoenix to a couple hundred miles further than Oshkosh, then back to Osh on one tank of 50 gallons? A Varieze does it every year.
......
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He does it by flying high, dialing his timing way back, and catching a good tailwind.

One of these days someone will do the same flight in their RV with dual P-mags & EICommander and dial their timing back and achieve the same, if not better.
 
chrispratt said:
I taxied behind one as I arrive at this year's Pecan Plantation fly-in. I won't make that mistake again. We used the grass for the taxiway. Pilot was using high power settings but moving extremely slowly. I figured he/she was fearful about the nose gear digging in or perhaps the airplane was oscillating too much if it moved faster. Whatever the story, it was the lengthiest taxi time I've had since leaving Oshkosh on a Friday morning. And all the dirt and grass that blew into my plane didn't help my attitude. Velocity looks to be definitely a hard surface kind of airplane. (Hope the pilot never goes to Oshkosh where grass taxiing is the norm.)

Chris
Click to expand...

Well, since an uber-moderator opened the door to complaints I have one for you. Last time at Lincoln Fly-In (KLHM) I was parked among the earlier arrivals, with the canopy open, chair set up, talking to some folks about the plane. An RV-10 taxiied all the way into the crowded area, spun around blowing dirt and small rocks all over my plane, canopy and guests. Blew the chair over and the canopy down on my shoulder. He shut down, got out and walked away. (Hope he doesn't regularly go to fly-ins where consideration of people and planes is the norm.) :rolleyes:
 
BJohnson said:
A couple of points from Chapter 4 of "Aircraft Design: A conceptual Approach" 4th edition, Raymer, Daniel P
> The canard design has higher drag than a similarly sized conventional configuration
> Inability to add flaps for high lift situations like landing causes the wing size to be increased or landing and takeoff speeds increased
> The aft wing flies in the downwash of the canard causing the aft wing to be presented at a higher aoa to achieve the same lift. This tilts the lift vector aft creating a new drag component.
> For the canard to be stable, the CG must be moved forward, causing the canard to have a higher wing loading than the main wing. the smaller canard is less efficient at producing lift than the main wing. The main wing works less and has to increase in size as a result.
> The smaller frontal area and smoother composite construction is how the canard counteracts the other drag effects

Related to pushers:
> Cooling drag is higher in a pusher
> The prop has to operate in the wake of the fuselage, reducing efficiency.
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Sounds like tractor design rationalization--probably after losing either a race or endurance test.
PROPS-pushers DO operate in the wake of the fuselage which is why they streamline the fuselage and cowling. On tractors the prop has to deal with flow back pressure off of the cowling and gear leg/wheel if fixed gear.
Cooling drag is similar with less back pressure issues. (Prop sucks air out of cowling--on tractor design both airflow and prop are pushing it making exit area critical) More streamlined fuselage and cowling on pushers generally equate to more equal inflow vs outflow.
Canard does not dramatically interrupt flow to wings--it's smaller, thinner and mounted off center--watch tuft testing.
Canard and wing both provide positive lift (more efficient)--there is no negative lift like on the average tractor tail.
Forward CG?? engine, prop, etc in rear--all have aft CGs.
Lack of flaps is due to delta wing design and DOES add to takeoff and landing speed increases.
 
Av8torTom said:
I believe it was Kit Planes magazine that recently ran an article on the dangers of canards. As a safety feature, the canard is meant to stall before the main wing. At altitude this is a great feature however, in the landing flare a few feet above the ground a canard stall can cause the nose wheel to hit the ground first and this has been blamed for a number of canard landing accidents.
Click to expand...

I haven't read the article and I can't speak for the velocity and other canard models but I have about 450 hrs in a Vari-eze and have landed slow, short, on grass etc and never had the nose drop in the flare.

One thing I dislike about pusher canard designs is the potential for disaster when taking off from any surface that provides significant drag on the wheels such as longish grass and sandy or soft surfaces. In such a situation the thrust from the engine at the back and the drag on the main wheels conspire to push the nose wheel down into the soft surface increasing drag even more. The situation cannot be relieved until the speed increases to the point where the canard gets enough lift to pull the nose wheel up out of the muck but it is difficult to build speed due to the drag on the nose wheel. This is not such an issue for tractor aircraft on T/O as the thrust vector and prop blast on the elevators are trying to lift the nose wheel out of the surface drag.

My gut feeling is that the Vari-eze was not significantly more fuel efficient than my 9A. From T/O to landing in the 9A I cruise around 150 kts and burn 24 to 25 l/h. In the VE it was around 140 kts burning about 21 to 22 l/h.

Fin
9A
 
If quoting a AIAA published textbook is not enough...

@ notes to Daniel's theories:
1. If they are draggier why can they be so much more efficient? Never hear of 50 mpg in other common designs. How many O-235 planes have flown from Phoenix to a couple hundred miles further than Oshkosh, then back to Osh on one tank of 50 gallons? A Varieze does it every year.
2. If the main wings must be so huge, why does a Varieze have such tiny wings?
3. With all that 'drag' inherant in the design how can just a smaller nose counteract it all?
4. Cooling drag can be equal given the amount of effort put into the design. They also have had good luck with plenums, downdraft, etc. When the main inlet is a NACA and the flow through the cowls is measured, as many have, the drag is as good or better than 'most' traditional designs, which of course, can also be improved.
Just sayin'......
Click to expand...

OK, say you don't buy into all the ideas of Dr. Raymer and published as a well regarded textbook by the American Institute of Aeronautics and Astronautics. Experts are often wrong. Lets look at trends in Burt Rutan's designs. Have you ever noticed that as Rutan's designs evolved, the canard got bigger, and then eventually disappeared? After Voyager and Proteus, the canard disappeared. White Knight, Global Flyer, and White Knight II do not have canards. It appears that Rutan now agrees with what Dr. Raymer presents.

Back to the original post, lets look at the numbers. Compare the Velocity XL-FG with a Lyc IO 540 260HP engine and fixed gear to a RV-10 with the same engine. From their websites (converted to common units):

Category ---------------------Velocity XL-FG ----RV-10
Empty Weight ---------------1700 lb------------1630
Gross Weight-----------------2800 lb------------2700 lb
Useful Load-------------------1100 lb------------1070 lb
Wing Area--------------145 ft^2 combined------148 ft^2
75% Cruise Speed------------201 mph----------197 mph
Takeoff Distance--------------1400---------------500
Landing Distance-------------1500---------------650
Stall (min) speed-------------75 mph------------63 mph

So an RV-10 is :
>lighter by 70 lbs despite having more wing area and mostly metal.
>It carries only 30 lbs less.
>Flies 4 mph slower at cruise despite having a high drag hershey bar wing optimized for metal kit building.
>12 mph slower stall (minimum) speed
>Takes off in 1/3 the distance and lands in less than 1/2 the distance.

The Velocity does have a +9g/-7g airframe, tested to +6 only. But for normal operations that just means the airframe is overweight.

Anecdotally, if canards were the marvel of efficiency, why are not all competitive sailplanes configured as canards?

There is an understated genius behind Van's "Total Performance" concept.
 
BJohnson said:
A couple of points from Chapter 4 of "Aircraft Design: A conceptual Approach" 4th edition, Raymer, Daniel P

> The aft wing flies in the downwash of the canard causing the aft wing to be presented at a higher aoa to achieve the same lift. This tilts the lift vector aft creating a new drag component.
Click to expand...

Seems like the aft lift vector tilt would only occur within the canard span. Outboard it would be the opposite,, tilting forward, and to some extent would counter the effect inboard.

Also, the canard flies in the upwash of the aft wing, tilting its lift vector forward over its whole span.

Dave
 
Velocity may not be an efficient canard design

BJohnson said:
Back to the original post, lets look at the numbers. Compare the Velocity XL-FG with a Lyc IO 540 260HP engine and fixed gear to a RV-10 with the same engine. From their websites (converted to common units):

Category ---------------------Velocity XL-FG ----RV-10
Empty Weight ---------------1700 lb------------1630
Gross Weight-----------------2800 lb------------2700 lb
Useful Load-------------------1100 lb------------1070 lb
Wing Area--------------145 ft^2 combined------148 ft^2
75% Cruise Speed------------201 mph----------197 mph
Takeoff Distance--------------1400---------------500
Landing Distance-------------1500---------------650
Stall (min) speed-------------75 mph------------63 mph

So an RV-10 is :
>lighter by 70 lbs despite having more wing area and mostly metal.
>It carries only 30 lbs less.
>Flies 4 mph slower at cruise despite having a high drag hershey bar wing optimized for metal kit building.
>12 mph slower stall (minimum) speed
>Takes off in 1/3 the distance and lands in less than 1/2 the distance.
Click to expand...

In looking at other canards they do stack up much more favorably. The Cozy MKIV vs. an RV-7 or Long EZ vs an RV-8 stack up much better.

Category ---------------------Cozy---------------RV-7 180HP each.
Empty Weight ---------------1050 lb------------1061
Gross Weight-----------------2050 lb------------1800 lb
Useful Load-------------------1000 lb------------739 lb
Wing Area--------------103 ft^2 combined------121 ft^2
75% Cruise Speed------------220 mph----------200 mph
Takeoff Distance--------------1200---------------575
Landing Distance-------------1300---------------500
Stall (min) speed-------------70 mph------------58 mph
Range @ 75% power---------1,000sm-----------775sm

The Cozy is 20 mph fasters, seats 4 (or 2 plus a lot more baggage). 261 lbs more useful load. 225 more miles in range. All the canard short comings in take off and landing still apply.

Just another comparison.

Jon Dembs
 
You will die only if you don't finish the RV7. I was considering the Velocity and flew down to Sebastian to fly it. It's different. It;s stable, so is the 10. There were only 2 areas that I didn't like, the long T/O run and fiberglass.
The RV10 was only a deam at the time. I'm glad I waited.
 
Gliders and canards

About canards and gliders. I had a talk with Paul MacCready about canards when Burt came out with the canard glider. Paul pointed out that the canard suffers as a glider because the coefficient of lift of the main wing is limited by having to keep the canard flying. In other words, on a canard, the slow speed performance must be restricted to insure the main wing doesn't stall first. So the RV10 can fly an approach, or a non canard glider can circle, at a much slower airspeed. This appears to be the reason for the long landing distance of the Velocity vs the RV10.
 
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