Actual Stall speeds, gross weights, angle of attack - Solidworks Flow Simulation

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Czr7s1

Member
Joined
Mar 30, 2013
Messages
11
Hi All,

I've been monitoring this group for a few years now but never really had time to contribute or ask questions. Job change and a move since I got my Sonerai forced me to put off. I'm posting on the I and II boards as this may benefit both models.

Not sure if many of you know but the EAA is now offering the newest version of Solidworks CAD software free with the membership. Being that I have hundreds of hours in an older version, I downloaded and am playing with the Sonerai airfoil for possible improvements. If anyone can post actual stall speeds along with your approximate gross weight (and approximate angle of attack whether from indicator or guestimate), it would help to sync the software up with actual numbers so I have a baseline when trying things out. I have VG's modeled on the wing now in SW but also am curious what the software will say when adding flaps (whether simple or slotted) on the trailing edge and going way out there with a drooping leading edge or possible movable slat. Not that any of this is doable due to added weight for these little airplanes but just to gain experience with the Flow Sim part of SW is all I'm after. And I happen to have a I in my trailer with wings that have slight corrosion that can be used to mock up some ideas.

Some of you may know this airplane from the early 90s racing days but back in 2015 I bought it from the original owner David Myers. He sold it to someone on the east coast after racing a few times in the early 90s but turned out it was kept tucked away in storage for many years and he was able to buy back. Since then, I pulled the engine and removed the fabric to inspect everything and started preparing to make mods so I can fit. David was barely 5' tall and I'm pushing 6'. Since there were no inspection holes in the wings, I drilled some of the wings skin rivets to get an idea of condition on the inside and found some corrosion on one of the rear spars. I built a floor to ceiling fixture and drilled one side of the wing all the way out. As mentioned earlier, job change and a move put a stop to the project but its tucked away neatly in my enclosed trailer itchin to be worked on. Supposedly these wings are modded for higher loading but you guys will have to confirm that. I know it has the stainless reinforcements at the rib to spar junctions and the angle on the spar is bolted with aircraft bolts all the way down. I only have II plans so don't know what the I is supposed to have wing wise.

Any info is appreciated and look forward to talking with all!

Sonerai_1.pngSonerai_VGs_SW.png
 

Bil438

Well-Known Member
Joined
Oct 17, 2007
Messages
804
My Sonerai is a SIILS. At 1150 lbs, and the J3300 engine at 400 rpm. it stalls at 63 mph. Don't have an Angle of attack indicator.
Bill E

Hi All,

I've been monitoring this group for a few years now but never really had time to contribute or ask questions. Job change and a move since I got my Sonerai forced me to put off. I'm posting on the I and II boards as this may benefit both models.

Not sure if many of you know but the EAA is now offering the newest version of Solidworks CAD software free with the membership. Being that I have hundreds of hours in an older version, I downloaded and am playing with the Sonerai airfoil for possible improvements. If anyone can post actual stall speeds along with your approximate gross weight (and approximate angle of attack whether from indicator or guestimate), it would help to sync the software up with actual numbers so I have a baseline when trying things out. I have VG's modeled on the wing now in SW but also am curious what the software will say when adding flaps (whether simple or slotted) on the trailing edge and going way out there with a drooping leading edge or possible movable slat. Not that any of this is doable due to added weight for these little airplanes but just to gain experience with the Flow Sim part of SW is all I'm after. And I happen to have a I in my trailer with wings that have slight corrosion that can be used to mock up some ideas.

Some of you may know this airplane from the early 90s racing days but back in 2015 I bought it from the original owner David Myers. He sold it to someone on the east coast after racing a few times in the early 90s but turned out it was kept tucked away in storage for many years and he was able to buy back. Since then, I pulled the engine and removed the fabric to inspect everything and started preparing to make mods so I can fit. David was barely 5' tall and I'm pushing 6'. Since there were no inspection holes in the wings, I drilled some of the wings skin rivets to get an idea of condition on the inside and found some corrosion on one of the rear spars. I built a floor to ceiling fixture and drilled one side of the wing all the way out. As mentioned earlier, job change and a move put a stop to the project but its tucked away neatly in my enclosed trailer itchin to be worked on. Supposedly these wings are modded for higher loading but you guys will have to confirm that. I know it has the stainless reinforcements at the rib to spar junctions and the angle on the spar is bolted with aircraft bolts all the way down. I only have II plans so don't know what the I is supposed to have wing wise.

Any info is appreciated and look forward to talking with all!

View attachment 14983View attachment 14984
 

eschrom

Well-Known Member
Joined
Jan 18, 2006
Messages
800
Location
Manchester, PA
55 mph at an actual flying weight of 750 lb. No AOA and I couldn't even hazard a guess.

Ed
2LS "bone stock"
 

Czr7s1

Member
Joined
Mar 30, 2013
Messages
11
Thanks for the responses men...at 55mph, the software shows the start of separation at 11 deg AOA - which as we all know does not mean the wing will stall. Just strictly the airfoil in the flow simulation and does not take anything else into account. Will incorporate the lift force and gravity variables for now to see what speeds and AOAs the software says lift will drop below a particular plane’s gross weight. Curious to see if 1150lbs matches up to Bill’s 63mph...
2291DEA5-6A4B-46A3-A03F-9093DC1399D0.jpeg
 

DeadRinger

Active Member
Joined
Feb 2, 2012
Messages
38
Location
KAPV
Solid works nice. That latest YouTube vid from Mike Peaty has that same program for his super crazy cub.
 

Czr7s1

Member
Joined
Mar 30, 2013
Messages
11
Been letting this computer burn up on these simulations...have some results to share but still not all the way finished with what I want to do. All these simulations have 3 constants for the most part - gravity, AOA, and airspeed. Also, its just one wing only in a 2d simulation with no wing tip - the 3d sims would take 300 hrs :oops: (the software analyzes a section of the wing and assumes it will be the same down the wing) I'll get the fuselage in SW to get us a drag number to use but will put that off until last. I'm concentrating on the stall speed to try and get that puppy down so most of my time has been spent at the 55mph(80fps) point. I did some sim's @ 60 and 65 but only to get Bill in the air. In addition to having some real time data from you guys, I used the XFoil program/database to make sure the Solidworks results are REAL and provide a good base line for anything tried to improve the stall speed and handling at the bottom of our envelope. It gives a realistic lift and drag coefficient to use for calculating but not really a REAL lift "force" that solidworks gives.

We'll start off with Ed's airplane @ 750 gross - stated 55mph stall...in short, the green is we flying. So, the numbers say Ed's airplane will fly between 12-15 AOA @ 55mph. Any AOA outside of that (positive or negative) and mother earth is getting closer. Didn't do 16 deg as most unmodified airfoils fall off after 15degs.
ED_spreadsheet.png


Chucker @ 800 gross - stated 55mph stall...numbers say 14 deg AOA at 55mph and that's about it. 60+mph and you seem to be good.
CHUCKER_spreadsheet.png


Bill @ 1150 - stated 63mph stall...obviously not enough lift at 55 or 60 so I went to 65. After 13 AOA, we flying.
BILL_spreadsheet.png


Worked with an easy to build slat yesterday (full radius leading edge - wrap a thin tube with trailing ribs similar to RV and probably some other flaps/ailerons). Amazing on how sensitive the position and chord length is to actual lift numbers. After (8) position and shape tries, here's what I got. 28% increase in lift with manageable drag. As in, if we can produce 225-250lbs of thrust from a direct drive VW, its at about 1/2 power from what I can figure. This is not including drag from the fuselage but still - improvement from the clean wing is what I'm after. I'll reduce speed on this config until it no longer provides enough lift - standby for results. 15 deg AOA screenshot of clean wing results first, then 16deg AOA testing with the slat. You can probably figure out where VG's would be placed in this setup. Need that high velocity air to stay attached for longer.
80fps_15deg.png 80fps_16deg_slat only 4_6in chord.png 80fps_16deg_slat only 4_6in chord_screenshot.png

If anyone was to try this, it would involve modifying the entire leading edge of the wing. These slats would need to be retractable as well as not always needed and come with hefty drag especially at a Sonerai's cruise speed. The back of the slat matches the modified leading edge of the wing for a good retracted fit. Would have to run more sims on if the the two leading edge radii "gap" when retracted at the bottom would affect cruise.

More to come...starting on a flap using the same chord as the aileron. Don't think there is anyway the rear spar can be moved up for more chord being that it is right at the seat backs.

If anyone has hooked up a thrust gage or has REAL static thrust numbers, please share along with prop diameter so I know if you have a reduction.

Thanks, Chris
 

eschrom

Well-Known Member
Joined
Jan 18, 2006
Messages
800
Location
Manchester, PA
Chris, I'm not an aerodynamicist so bear with me. Chucker is in the green at only one AOA (14 deg). This aligns with my understanding of what happens when an airplane is on the brink of a stall in straight and level flight - pull back any harder on the stick and you stall; relax the stick and you don't stall but you don't make enough lift to hold that altitude. Either way you head south. However, for me the green covers a range of 12-15 degrees. Does this mean that, according to the simulation, I'm not really on the verge of a stall at 55? That would make sense, since I'm 50 pounds lighter than him. Now I'm anxious to get back in the air and measure it again.

One other thing, I was at ~4000 ft AMSL when I stalled it. Not sure if the altitude matters that much.

Ed
 

Czr7s1

Member
Joined
Mar 30, 2013
Messages
11
Ed, Your understanding is right in line with mine. If it was possible to lock in the airspeed at 55mph and AOA @ 14deg, "the numbers say" Chucker's plane will provide just enough lift for level flight. Let's assume the thrust and % power of the engine are linear and run together (they may or may not), to overcome wing drag only we would need about 45% power. The fuselage is mostly streamlined but will add drag - I'll get this modeled ASAP so we have a number. Like you mentioned yesterday, I'm know aerospace engineer either - just interested in design so therefor the variables and formulas start coming out. The technology available these days can rule out most of the trial and error ways of doing things but in the end, who will be the test pilot?!? These airplanes are proven so like you did at 4000, just have some altitude when playing.

On your question about altitude, it does affect the Reynolds number which is used in the lift calcs I have in the Xfoil columns but does not affect what Solidworks says. I trust the Xfoil wind tunnel numbers more than Solidworks as it has so many variables that are user entered. Getting both consistently matching at all speeds and AOA's enables us to change things just in Solidworks and know its close.

Like this - ran several sims yesterday with a full span slat in the same spot as mentioned above but added 30 deg of the current aileron chord with a small slot (would be a full length flaperon where pivot point drops a bit for the slot), and we have enough lift to fly in the low 40's at your gross. Not sure if this is realistic for the Sonerai but would be simple to incorporate a mixer into the current aileron linkage. Interference with bottom flange of rear spar would be an issue but changing the pivot point and other factors is doable. I had full length flaperons on a Minimax years back that worked great at ~30degs but it had a lot more wing to fly with and was ~200lbs lighter gross. With a slight head wind and 50 hp it had, it would fly indefinitely with my 160lb butt at full throttle at an extremely steep AOA.

15-16 degree AOA sims below (I must not have saved screenshots of other combos): 55mph clean wing, 46mph wing with slat only, and 41mph wing with slat and "flaperon" - right on the edge so 42mph is prob a more realistic bragging number. Again, these are just numbers from the software so who knows. I can move the slat further forward and increase AOA till the cows come home but the drag number goes beyond our 250lb(~1100 newtons) of available thrust. Someone running a reduction and larger prop could definitely pull a different setup through the air for even lower numbers but these aren't STOL airplanes. The magic 4x stall cruise number would be great but will take some serious modifying to a stock wing.

80fps_15deg.png 68fps_16deg_slat only 4_6in chord.png 60fps_15deg_slat&flap_30deg.png 60pfs_15deg_slat&flap_30deg.png
 

Voss

Member
Joined
Jul 26, 2017
Messages
20
Location
Italy
Hello Czr7s1,

My Sonerai II MidWing

engine
: jabiru 85hp 2200
Max RPM: 3300
Static RPM: 2950 with propeller sensenich carbon fiber, ground adjust pitch.

runway: 2625 ft

take-off: 60 mph
landing: 65 mph

stall: 50 mph

at 2800 RPM the speed in level flight is 120 mph
at 3200 RPM the speed in level flight is 145 mph

Climb: 1500 ft / m at 3100 RPM and 85 mph

Bye!!

Nik
 

Voss

Member
Joined
Jul 26, 2017
Messages
20
Location
Italy
takeoff weight is 807 lbs
without pilot "that ;-) I weight 186 lbs the Sonerai weight is 618 lbs
 
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