NoCOPilot wrote:

.
I like the looks of it, but wish it was the same span as the S20 (S21 is one foot shorter per side, and gives up 10 square feet of wing area because of it).

I guess with the S-21 being non-LSA, RANS was going after a little more speed. They quote 75% cruise as 155 mph with the 180 HP Titan 340. Not sure what a projected cruise would be with the new yet to be introduced 135 HP Rotax 915iS that Courierguy mentioned. What's that old adage, there is no such thing as a free lunch ?

Also, figure a Rans S20 at 1320 GW with a 100 HP Rotax 912 vs Rans S21 with 135 HP Rotax 915 say at 1800 GW has similar power loading. The S20 vs S21 power loading is 13.20 vs 13.33. lbs/hp. That's fairly close and that's not taking into account any actual 915 weight savings (vs Titan 340). Wing loading of course is different.

Ultimately, jumping in and taking a flight around the patch is what counts.

.
In theory there is no difference between theory and practice. In practice there is. Yogi Berra

.
https://en.wikipedia.org/wiki/Aspect_ratio_(aeronautics)

In aeronautics, the aspect ratio of a wing is the ratio of its span to its aerodynamic breadth or chord. A long, narrow wing has a high aspect ratio, whereas a short, stubby wing has a low aspect ratio.[1].

For a given wing area, the aspect ratio, which is proportional to the square of the wingspan, is of particular significance in determining the performance. Roughly, an airplane in flight can be imagined to affect a circular cylinder of air with a diameter equal to the wingspan.[2] A large wingspan is working on a large cylinder of air, and a small wingspan is working on a small cylinder of air. For two aircraft of the same weight but different wingspans the small cylinder of air must be pushed downward by a greater amount than the large cylinder in order to produce an equal upward force. The aft-leaning component of this change in velocity is proportional to the induced drag.

Denali wrote:NoCOPilot wrote:

.
I like the looks of it, but wish it was the same span as the S20 (S21 is one foot shorter per side, and gives up 10 square feet of wing area because of it).

I guess with the S-21 being non-LSA, RANS was going after a little more speed. They quote 75% cruise as 155 mph with the 180 HP Titan 340. Not sure what a projected cruise would be with the new yet to be introduced 135 HP Rotax 915iS that Courierguy mentioned. What's that old adage, there is no such thing as a free lunch ?

Also, figure a Rans S20 at 1320 GW with a 100 HP Rotax 912 vs Rans S21 with 135 HP Rotax 915 say at 1800 GW has similar power loading. The S20 vs S21 power loading is 13.20 vs 13.33. lbs/hp. That's fairly close and that's not taking into account any actual 915 weight savings (vs Titan 340). Wing loading of course is different.

Ultimately, jumping in and taking a flight around the patch is what counts.

All good points, and really it's probably a waste of time to worry about projected performance anyway--the proof will be in the pudding, or something. It's interesting to compare specs with the Bearhawk Patrol though. Empty weights seem similar, the Patrol is a couple hundred pounds heavier gross weight (2000 vs. 1800), claims a 180 hp 75% cruise of 150 vs. 155 for S21, and has a much larger wing at 180 sf (33 ft span, 6.05 AR) vs. 141 sf for the S21 (28 ft span, 5.53 AR)

At any rate, the S21 is an exciting new option. It's good to see RANS embracing this type of flying finally (21" tires standard, vs. 6.00x6 standard on S6 and S7 historically) and I'm sure the S21 will be a great performer.

Will be interesting to see if the cruise speed is real at the claimed 75% power setting. If so, it should be a very nice machine.

Greg

FWIW: RANS has a history of stating very conservative performance # 's. Like VANS seems to. I know for quite a while they claimed the S-7 stall in the high 40's, while meanwhile I was landing in low 30's. Taking high AOA piot errors and all that into account, they were still very conservative in their claim.

Mike, what I should have said was, "Is that a first to have an integrated a steel tube frame (crash/roll cage) into a semi-monocoque fuselage?"[/quote

Just because it's metal covered does not imply that it's "semi monocoque".

MTV

Looks impressive from the photos.

The carbon fibre doors will apparently fit the S20 and save about 10 lbs.

I'm looking forward to seeing it in the flesh at OSH. That wing design looks like it has lots of potential.

Crzyivan13 wrote: Looks like a Miniature 180! It has good speed and range too. 155mph @ 75% / 527 mi......

Doesn't look quite like a 180. I don't care for the swept tail. Like the GlasStar, and the post M4 Maules, IMHO it would look better with a square tail, or at least squarish like the S20, or a round one.

155 mph @ 75% power...IMHO they'll need either a c/s prop to achieve that, or else an extremely coarse cruise prop. With a STOL-compatible fixed-pitch prop, I'd guess more like 125 mph. That's down low, BTW, not "trued out" at some nose-bleed altitude like some mfr's like to use for this stat.

The prototype looks to be designed around the Titan 340.....might be that a lot of people will hang a 320 on it. Lots of those available on the used market, at prices that better fit a tight budget. I'd like to see the performance specs on that combination.

As per the display at Osh, it appears that it can make only right turns.

Hotrod180 wrote:

.
155 mph @ 75% power...IMHO they'll need either a c/s prop to achieve that, or else an extremely coarse cruise prop. With a STOL-compatible fixed-pitch prop, I'd guess more like 125 mph. That's down low, BTW, not "trued out" at some nose-bleed altitude like some mfr's like to use for this stat.

Claimed 75% Cruise at 155 mph and Stall at 38 mph give a Vc to Vso ratio or range of over 4 to 1. Plus the S21 claims to glide at 11:1 These figures strike me as very optimistic. I am not saying "not doable" or necessarily impossible, but optimistic. For comparison, Vans RV9 Tail Dragger with 160 HP and fixed pitch prop specs out with a Vc / Vso of 188 mph / 50 mph at Gross Weight giving a 3.76 ratio .

Someone said RANS is conservative in their claims and specs. If so then this plane will represent some very slick engineering.

I do think think the S21 as an all metal plane will be well received for those who hangar outside and hate anything rag. I think it will be a stunning success IF they can get the build time, especially with Quick Build options, way way down. I think there is a big segment of potential buyers who in the past have hesitated about buying a kit they felt they might not be able to finish up. The S21 offers pre-painted metal, fully matched fully sized no-deburring required holes, and blind rivets. Nice.

I also hope that RANS will up their PR game. The videos and website for the CC XCub are just stunning. Watching Randy in some of his older videos do a walk around with a shaky handheld video camera and poor audio now seems out of step with the times The new S21 Outbound and RANS's excellent company reputation deserve first class promotion and media PR..

Magnet wrote:

.
As per the display at Osh, it appears that it can make only right turns.

If anyone goes by area 620 at OSH and can snap a few pics of the S21 and post them here, that would be a real treat for poor souls like me stuck back East here in 100 degree heat working our fannies off.

Couple pics, haven't seen this brochure on the web yet...







Interesting that the prototype is dual struts, but production will be single. Not sure how the single strut structure will work with leading and trailing edge spars, but I'm sure they've got it figured out. Good to see RANS continuing to push forward with new products.

I am definitely interested. Might have to inquire on a factory built one..

I spoke to Randy about the S 21. Interesting airplane. I asked about 51% rule with the kit.....he said it'll probably follow in due course, but it should be easy enough to document. I asked about a "quick build" kit....he said it already is about as "quick build" as he can get it without the FAA having fits.

It looks pretty simple to build. As noted, pre punched and de burred holes. Randy said there are only like four holes in each wing spar that'll need to be matched and drilled. Everything else is matched and punched.

I asked about O-320. He said he's pretty sure that the O-320 is a couple inches wider than the O-340, so it wouldn't fit in the current cowl. I thought the 340 was just a stroked 320 and was dimensionally the same, but.....

The steel cage is virtually identical to the S-20, lots of space inside for two plus baggage.

Very interesting....but not much wing....

MTV

Curious whether the through tail cone was necessary structurally, or an attempt to get some better cruise speed out of it. The change to a swept tail is unfortunate aesthetically.

I looked at the vertical stab on the Rans S-21. Being all metal, I wonder if it is simply a slight variation of the one on their Rans S-19. Vans does the same on some of their all metal low wing RV planes for example. Keeps costs down I suppose.

Rans S-19


Rans S-19

S-21 metal wing test update.... and more to come shortly.

Randy flew the new metal s-21 wing on an s-20 Raven (hybrid). The new wing will be available on the new s-21 and also the s-20 raven LSA. It should also be available on the s7. (Retrofit on these planes, not just an option for the future, but also an upgrade for current s-20's and some later s7's I believe).

As posted by Randy today:

Raven with Outbound wings: Conducted a brief .4 of an hour flight in 104 degree F temps, DA was 5000, winds light from the south. It was a check flight, to make sure controls were responsive and symmetrical (they were) and make sure all things were go for further testing. The most stressful part of flight testing new designs is getting the plane ready for data acquisition. A few crow hops can tell a lot. Controls were light and even. Being only 20 pounds heavier it reached lift off speed in 5 to 6 seconds. The feel in the flare, excellent, very easy to land.
I was impressed with the effective ailerons. Very light but with an odd feel, more on that. The other concern was the force on the flaps. Flap extension force seemed less than the stock Raven wing flaps. This was the intent of the "bail" type flap, good to know it worked out. Back to the ailerons...I kept the flight short because that little voice said go back and investigate.
Back in the shop we measured the static break out forces up to 3.5 pounds. We then tweaked the hinges and got this to be at 2 pounds or less. An aileron system can have a lot of aerodynamic boost, as do these, but if there is system friction it will mask the feel, even though the break out pressure in flight is very light (2 pounds or less). That system friction masks the feed back and diminishes the self centering. The combination of light forces and little self centering would make most pilots uncomfortable. The stick release test was positive, going back to neutral, just a tad slower than what a RANS should. Tomorrow we test with the reduced system friction and take some readings. Ultimately we will have that nice feel you expect in our planes.
We are predicting at lease 5 knots faster and no less stall speed. At first blush that seems both those goals are well within reach. Rate of climb was familiar and plenty.
I am very excited about further flight testing and will post more when possible.

The news about the speed increase while not losing stall speed is what I was hoping to hear!
Personally I'm interested in an S20/21 hybrid, a turbo injected rotax in the 125-135hp range, VG's to bring stall down even more, and possibly seeing a 100mph envelope (~30-130mph) while maintaining a low fuel burn, super high g rating, high fuel capacity, and a plane that can be operated up to 1500lbs (or 1320 as an LSA). That just sounds badass!

But anyway, it's also a step closer for those interested in the s-21! Figured I'd pass it along!

Slightly off-topic, but...
I saw my first Rans S20 Raven this weekend-
first at the Arlington fly-in, then parked overnight at my own airport.
Didn't get a chance to check it out at AFI, but noticed it & thought it was a Kitfox.
Then later I noticed it had flaps & ailerons instead of flaperons.
Also had a rounded rudder like a Cub, not the squared off rudder which per the Rans website seems to be standard for an S20.
It appeared to have a Rotax or some sort of fluid-cooled engine, and a ground adjustable 3 blade prop.
I'm more of a Continental & Lycoming man myself, but it's hard to argue with the weight & performance of these newer engine designs.
It had a cockpit cover on it so didn't get to check out the interior, but from what I did see it looked like a pretty slick little airplane.

The S-21 flew for the 1st time this week! This one is flying with a rotax, a 2nd prototype will be built with a titan 340.

https://www.facebook.com/ransaircraft/v ... 744956351/

By way of comparison only: A short body Mooney, 180hp constant speed prop, retractable gear, laminar flow wing, original sheet metal (no 201 mods), all the cowling seals cleaned up and working right, with new engine mounts so the thrust line is where it's supposed to be. Two adults in the front seats and a pair of 100lb teenagers in the back.

Full throttle and 2500 RPM at 8000' in still air.

Speed 167mph.

I'd like to provide some clarity on what it would take to accomplish the stall speeds advertised in the Rans S21 Brochure.

On the brochure, stall speed is claimed at 42mph (18.7757 m/s), lets assume this is at maximum gross weight 1800lbs.
The brochure also declares a wing area of 141 sq ft. (13.1 m^2)
Lets do our calculation at sea level air density (1.225kg/m^3).

The basic lift equation would dictate the following: L = 1/2*p*S*CL*V^2

8007 newtons (lift required to hold up 1800lbs) = .5 * (1.225) * (18.7757) ^2 * 13.1 * CL

solving for the coefficient of lift, we get a value of 2.831.

This is a very difficult lift coefficient to achieve without sophisticated high lift devices. Aircraft with leading edge and complex trailing edge devices with vortex generators and other equipment to reduce spanwise flow and promote attachment may be required to achieve this type of lift coefficient.

Now, I am not saying that it is impossible, however it is very difficult to achieve, and is increasingly unlikely without the added high lift devices.

EDIT: I would also like to comment that these kinds of numbers plague the industry. The bearhawk patrol site specifications claim a landing speed of 35, lets assume that is also the stall speed... For that specific aircraft, a stall at 35mph would require a lift coefficient of 3.5!!! With nearly the same airfoil as the S21. The data on NACA airfoils (somewhat comparable to Riblett foils) is publicly available and I urge anyone interested to review the max lift coefficients achieved at reynolds numbers that these aircraft operate at. Review the stall speeds and lift coefficients reached by production aircraft (Cessna 170, 140, super cub) All reasonable values, certainly not exceeding 2.5+ CL.

Another bad offender: Cubcrafters - 3.26CL for the carbon cub FX.
Another bad offender: Kitfox - 3.55!!!! for the STi S7 Super Sport

Please note, that the lift generated by an aircraft is a function of velocity squared, knowing this, achieving just a couple extra mph is increasingly more difficult to achieve as you approach these extremely low speeds. Not to mention, measuring these speeds can be a challenge itself.

Pinejuice wrote:I'd like to provide some clarity on what it would take to accomplish the stall speeds advertised in the Rans S21 Brochure.

On the brochure, stall speed is claimed at 42mph (18.7757 m/s), lets assume this is at maximum gross weight 1800lbs.
The brochure also declares a wing area of 141 sq ft. (13.1 m^2)
Lets do our calculation at sea level air density (1.225kg/m^3).

The basic lift equation would dictate the following: L = 1/2*p*S*CL*V^2

8007 newtons (lift required to hold up 1800lbs) = .5 * (1.225) * (18.7757) ^2 * 13.1 * CL

solving for the coefficient of lift, we get a value of 2.831.

This is a very difficult lift coefficient to achieve without sophisticated high lift devices. Aircraft with leading edge and complex trailing edge devices with vortex generators and other equipment to reduce spanwise flow and promote attachment may be required to achieve this type of lift coefficient.

Now, I am not saying that it is impossible, however it is very difficult to achieve, and is increasingly unlikely without the added high lift devices.

EDIT: I would also like to comment that these kinds of numbers plague the industry. The bearhawk patrol site specifications claim a landing speed of 35, lets assume that is also the stall speed... For that specific aircraft, a stall at 35mph would require a lift coefficient of 3.5!!! With nearly the same airfoil as the S21. The data on NACA airfoils (somewhat comparable to Riblett foils) is publicly available and I urge anyone interested to review the max lift coefficients achieved at reynolds numbers that these aircraft operate at. Review the stall speeds and lift coefficients reached by production aircraft (Cessna 170, 140, super cub) All reasonable values, certainly not exceeding 2.5+ CL.

Another bad offender: Cubcrafters - 3.26CL for the carbon cub FX.
Another bad offender: Kitfox - 3.55!!!! for the STi S7 Super Sport

Please note, that the lift generated by an aircraft is a function of velocity squared, knowing this, achieving just a couple extra mph is increasingly more difficult to achieve as you approach these extremely low speeds. Not to mention, measuring these speeds can be a challenge itself.

Way above my pay grade.

I might venture an assumption though that the 42 stall is at the LS gross of 1320 maybe? That’s a little faster than but pretty close to where the S7S gives it up. My airspeed indicator and GPS agree to about 35mph, then the AI zeros out. I’m with you though, 42 at 1800 is a stretch.