SONERAI 2, what's your indicated stall speed?

[J-M]

Hello,
Regarding the stall speed of the Sonerai 2,
On the Monnett plans or documentation I found the value of 72 km/h for the stall speed (39 kts, 45 MPH) But according to different sources found on the internet, this value is much higher... up to 100km/h (54kts, 62mph) at 550kg (1200lbs) for one source.
Of course they are indicated speeds, whose value is not very precise because of the pitot tube indidence and anemometer calibration error .

Notice to all SONERAI 2 pilots,
Can you give me your stall speeds read on the anemometer and for what weight?

Why this research?
Well, I plan to register a Sonerai 2 in Ultralight (in France) but I must prove that it is less than 70km/h (38kts, 44mph), which is not the basis of the basis but I would like to see the Feasibility with VG's or a mixing of flaps in flaperons.
if the speed gap was low, knowing that in reasonable way I can limit the maximum weight to 450kg (990 lbs) which can help.
Obviously if the real stall speed was higher than 80km/h (45kts, 50mph) there is very little chance that reaching 70km/h even with flaperons.

Thank you in advance for your help or your advice

Sincerely

J-M from France

 

[soneraifred]

I don’t believe there is a built-to-plans Sonerai II that stalled at any where near 45 mph. Most stall at 55 mph or higher. My Sonerai IIL at 900 lbs gross weight stalled at 58 to 60 mph IAS. The only way to obtain the stall speed that you are shooting for is to increase the wing area, and that will require designing a new wing.

 

[N804RV]

Hello,
Regarding the stall speed of the Sonerai 2,
On the Monnett plans or documentation I found the value of 72 km/h for the stall speed (39 kts, 45 MPH) But according to different sources found on the internet, this value is much higher... up to 100km/h (54kts, 62mph) at 550kg (1200lbs) for one source.
Of course they are indicated speeds, whose value is not very precise because of the pitot tube indidence and anemometer calibration error .

Notice to all SONERAI 2 pilots,
Can you give me your stall speeds read on the anemometer and for what weight?

Why this research?
Well, I plan to register a Sonerai 2 in Ultralight (in France) but I must prove that it is less than 70km/h (38kts, 44mph), which is not the basis of the basis but I would like to see the Feasibility with VG's or a mixing of flaps in flaperons.
if the speed gap was low, knowing that in reasonable way I can limit the maximum weight to 450kg (990 lbs) which can help.
Obviously if the real stall speed was higher than 80km/h (45kts, 50mph) there is very little chance that reaching 70km/h even with flaperons.

Thank you in advance for your help or your advice

Sincerely

J-M from France

That's Interesting. I was just studying Ramer's Simplified Aircraft Design. To stall at 45mph on a sea level standard day at 950lbs, with a typical max coefficient of lift, it would take a wing area of around 100ft^2. The S-IIL has a stated wing area of 84ft^2.

The Raymer Calculations show that the S-IIL should stall at around 53mph. Mine stalls at around 54-55 mph indicated.

The problem is the Sonerai, like many small low-wing aircraft, if you pull the power off and try to land it like a Cessna, you're gonna find yourself close to the ground with a high sink-rate and trouble maintaining that perfect 1.3Vs0. So, some folks try to land it fast or even wheel it on, and often end up bouncing down the runway.

The secret is airspeed control right from abeam the numbers, judicious use of power if you feel yourself getting behind, and not try the big swoopie flare like you did in the Cessna with the instructor on board.

 

[addaon]

Also keep in mind that the Raymer estimates (all aerodynamic calculations) tell you the calibrated stall speed, KCAS. If you're asking pilots what they see at stall, you're asking about KIAS. But (a) around the stall is where the error between KIAS and KCAS is generally largest; (b) very few EAB folks actually properly calibrate their pitot systems through all angle of attacks to even allow correction between KIAS and KCAS, from what I can tell; and (c) installation error will vary from airframe to airframe.

Unless the requirement is actually written in terms of KIAS instead of KCAS, you'll do better to analyze this properly than to ask pilots what they see.

 

[J-M]

Thank you for all these answers in such a short time,
To reply to Soneraifred, it is on the SonexAircraft.com site which sells the Sonerai plan that I read in the Sonerai 2 specs a stall Speed of 45mph (72km/h).
For the moment I dont have sonerai to check, I envisage the purchase if I was sure to hold the stall speed at 45mph whith mods.
For the moment I have a KR2 with a C90 without flaps and it stall at 45 kts.
For the rest, actually I know that the kias is more or less false especially near the stall but it is the only value that the pilots of Sonerai see,
I especially wanted to have aproximate values of speed in order to know if with flaperons The speed of 45mph is realistic or not , And with your answers I start to tell myself thatif the usual value ofstall is around 58mph, I think it is impossible to reach 45mph even with flaperons ... given the surface of the ailerons..
(sorry for my english, google helps me)

 

[TFF]

Most planes built, do not perform on the numbers unless built to show standards perfection. It is getting easier to do that with CNC but most airplane designers build planes and then fix the plans. When the Sonerai was designed there was no category if it could stall slow. Stall at 45 or stall at 100. It had no bearing until people shoehorning them into LSA microlight, which was never a consideration. Extra light and flown solo, it’s on the cusp. Not with two people.

 

[Vigilant1]

Unless the requirement is actually written in terms of KIAS instead of KCAS, you'll do better to analyze this properly than to ask pilots what they see.

Lots of truth there, but I'm sympathetic to the need to ask the question. Doing an analysis to determine stall speed depends so much on an assumed/analytically derived CL. Getting an accurate real world CL is hard.

 

[soneraifred]

Do not believe the 45 mph stall speed spec. I built my IIL from 1976 thru 1986, and flew it for the first time in 1986. I flew it for 34 years. During that time I edited and published the Sonerai Newsletter for almost 14 years. In all that time, I never heard anyone claim an actual stall speed of 45 mph. The lowest I heard was 51 mph, but I’m not sure I believe it. If you do the math, to get a stall speed of 51 mph (the max US LSA stall speed), it is necessary to add about 2 feet to each wing panel to get enough wing area to lower the speed. That would necessitate redesigning the wing to deal with the increased wing bending moment. I know of a couple people who redesigned the wings incorporating a thicker Riblett airfoil, and increasing the span, and I believe it did lower the stall speed some, but I do not recall the numbers.

 

[BBerson]

To reply to Soneraifred, it is on the SonexAircraft.com site which sells the Sonerai plan that I read in the Sonerai 2 specs a stall Speed of 45mph (72km/h).

It doesn’t say which weight category is 45 mph. There is three weight categories Sonerai Plans-Built Sport Aircraft
Monnett weighed about 100 pounds originally

 

[lr27]

If I'm not mistaken, a 990 lb. Sonerai would have to have a WING Cl of almost 2.4 to stall at 70 kph. Of course, the whole wing is necessarily at a lower lift coefficient than the maximum achieved by an airfoil. You would need some fancy high lift devices and a redesigned wing to carry them. And probably a bigger tail, and maybe a stretched fuselage...... Suggest you find a more suitable design to start with.

I've read, in the Incomplete Guide to Airfoil Usage ( https://m-selig.ae.illinois.edu/ads/aircraft.html ) that the Sonerai II uses the NACA 64-212 airfoil. I doubt you'd get a whole-wing Cl above 1.2 with that, so we'd expect a stall speed just over 100 kph, plus or minus a fair amount.

I'm sure a different airfoil could get you up to 1.5 or so, but that's still 82 kph.

 

[Manudubourg]

J-M,
i did an analysis for this goal (French UL: 70km/h, 450kg. Didn’t care about 500kg). My conclusion was excactly what Fred mentioned: more wingspan and airfoil with more lift (i looked at Ribblet). Of course, existing Sonerai spar do no longer fit the bill for such a modified wing.
as for flaperon, someone did that in Europe. But the existing aileron cord is very small. i doubt flaperon will lower significantly the stall speed.
if you need inspiration to figure out how a French UL wing looks like for a 2 seater, check the UL version of the Gazaile. Numbers are known to be well within the regulation. and compare with the Sonerai wing. that will give you an idea of the extend of the modification needed.
Emmanuel

 

[fifidibosco]

Hi JM

how do you have to prove the Vso? By an in flight evaluation with official flight evaluator (what about the single seaters ?) or based on a calculation document. If it's a calculation I think Sonex is able to provide the Monnett documentation that give 72km/h.
Vso 80km at 500kg makes a Vso approximately 76kmh at 450kg
Fifi

 

[J-M]

Hello
for Manudubour, I have the plans of the gazaile indeed if I had to redo a new wing it will sound to me modification tracks but my goal was precisely not to leave in an almost new construction but just to make minor modifications such as vg’s or flaperons, possibly redo ailerons with 2 inches widh if it can bring a gain but if I had to redo new wings better buy directly a new aircraft.
for fifidibosco ,to prove that the stall speed is less than 70 km/h I have already had to do it on another 1 seater aircraft
the authorities ask to make 3 stalls at a different heading of 120 degrees in order to cancel the effects of the wind on the ground speed and to provide the gps trace Which shows that the average of the 3 ground speeds is less than 70 km/h
On the other hand, it is a good idea to contact Sonex, but thanks to the answers you have all given me I no longer have too many illusions about the feasibility of my project
I dont think that the Sonerai would pick up at such a high Stall speed compared to what was announced but I have the opportunity to acquire a Sonerai and the only way to register it here was to Pass it Ultralight because here an Experimental aircraft built in another country cannot be registered in France
only Ultralight if it respects the limitations thank you for your help

 

[Daleandee]

Can you use the "lifting body" defense?

 

[Manudubourg]

If I recall correctly, someone did register a Sonerai as UL in France. this individual was not smart with his way of flying. the DGAC heard about it and did an inspection. the owner was unable to proof the stall speed was below 65 (before the implementation of 70). Now, the DGAC knows a Sonerai is not a UL. At least, without modification.

 

[Old Koreelah]

Very interesting discussion.

How accurate is your ASI during the landing phase?

One way to reduce errors due to angular airflow is to add an articulated intake to the pitot tube. Forget hi-tech; just add a short length of flexible plastic tube, then plug into it a pitot with its own empenage hanging back behind it. I made a triangular one out of thin bits of spruce, with a pair of tiny “rudders” and tailplane. This helps to keep the intake better aligned with airflow during side slips and high AoA approaches.

 

[Skippydiesel]

I don’t believe there is a built-to-plans Sonerai II that stalled at any where near 45 mph. Most stall at 55 mph or higher. My Sonerai IIL at 900 lbs gross weight stalled at 58 to 60 mph IAS. The only way to obtain the stall speed that you are shooting for is to increase the wing area, and that will require designing a new wing.

OR fit Fowler flaps, giving a pilot controlled temporary increase in wing area, combined with increased curvature, just like the big boys.

 

[AAN]

John Malvestuto, obviously did a lot of experimental work and practically proved his TurboWing concept (basically a pair of paramotors pushing up at about midwing span), which made wonders to a stall speed

 

[TFF]

Powered lift is more about flying slow than stall. What happens if an engine quits when slow with a big hole in the wing?

 

[Vigilant1]

This is the Sonerai subforum. Nobody is going to mount props for powered lift in a Sonerai. The originator of this thread would probably appreciate suggestions and info relevant to his situation.