The 230XX airfoil is faster than a LS airfoil?
But - it was the airfoil on the S**** Playboy that Van reverse-engineered in metal. So we've inherited it here. My old RV4, for one, had just about zero prestall buffet.
Never the less, the old Five-Digit airfoils abound and their sharp stall is engineered out on certified aircraft with planform bandaids, leading edge devices, twist, etc. It has served us well over the decades but I for one wouldn't revive it in the face of 60 year improved technology.
You all will have to wait a bit longer to see what I have in store for the RV world...
Well you sound like a real Aero guy, I have only stayed in a Holiday-Inn and sat next to a real Areo guy.
Stalls - I think personally the stalls on RV's are very mild; in fact they don't want to stall. I agree the buffet is nominal or minimally. Fair to say sharp but not dangerous. RV's need stall strips (to get them to stall) to do good snap rolls. If you want to get into MODERN than get an AOA device to warn you of impending 'danger'. For a plane that stalls in the low / mid 50 mph range, slower than a C-152, the danger is small.
The laminar airfoils are not known for mild stall properties. They may warn you but they break like a sob. The Piper Tomahawk uses a GA (laminar) airfoil. I flew one for 500 hours and taught in them. They had weird and unpredictable stall characteristics, like a snake bite, breaking right or left abruptly. I like the T-hawk a lot overall, had good times, but stalls are not a stong point. It flew fine but the T-tail added some more weird control issues both in flight and landing you had to adjust for.
MODERN - I don't totally buy the "modern" argument when presented with it. Auto engine guys say MODERN, yea but its heavier and slower. Again you know more about Aero than I, but in my experience with LF wings, they promise a lot but never really deliver. Two-dimensional data rarely is accurate for an actual wing, and other factors come into play, which I'll mention below.
LIFT? (l/d)
The Glasair III ( LS(1)-0413 airfoil) lost lots of sales when other planes out performed it, the Lancair and QuestAir to name two. The QuestAir beat a Glasair III silly with less HP. The QuestAir used the 230XX airfoil, 23015 root/23010 tip. Stoddard was confused. It's laminar airfoil was MODERN, it should have less drag, RIGHT? The reason was
the LS airfoil had less drag but also made less lift. So the LIFT/DRAG for the QuestAir (230XX) was over twice the LS airfoil of the Glasair III in cruise condition, OVER TWICE! Stoddard made it worse by filling in the lower trailing edge cusp to get the stick forces down, decreasing lift performance further. It was a bad choice of an airfoil. No doubt there are better laminar airfoil choices Glasair could have made; still, modern is not everything. Ever fly a Glasair? They are fast but don't handle as lovely as a RV, especially in roll with the RV's 'frise' ailerons.
BOTTOM LINE
LF airfoils do have a narrow operating range, and they do have more pitching moment and less lift in many cases, apples for apples. Real airframe and real world performance will be different than the 2-D specs.
The QuestAir with a 230XX airfoil is a faster plane than the Glasair III with a laminar airfoil? That is not a debate. The Lancair IV uses some custom and non laminar flow airfoil and is also faster I beleive. Yes the 230XX goes back to the 1930's or 40's but things have not changed much. It gets the job done. Bad stall characteristics are over blown in my opinion. Does any one fear their RV's stall? There is more than just low drag numbers to an airfoil, like lift and pitching moment.
Hey Fellas:
As for the Questair Venture wing, it did start with a 230XX foil, but it was changed from that rather quickly (stall characteristics again!). Do your investigating before you report!
Mark two or three refs show the QuestAir uses a 230XX? What did it change to? "The designer Jim Griswold... who also headed the team the QuestAir Venture, also designed the Malibu for Piper... both use the NACA 230XX." Ref
http://nuventureaircraft.com/
Laminar flow airfoils are not new. The P-51 in the early 1940's had the laminar flow NAA/NACA 45-100. I reject the off hand comment that they used what ever NACA threw out. They had the Clark Y before. I have read some of the old dead "sea scrolls" of Aerodynamic days gone by. Those guys where smart. They may have not had computers but they knew how to use them slide rules. I really don't think it was a willy-nilly reason the 230XX was and is popular. Even the late model Cessna Citations still used the 230XX today. Is it the perfect airfoil handed to us from upon high? No but it seems to work well in the RV and many famous planes. One KEY to the 230XX working well is keeping weight down. Drag does go up quickly at higher lift coefficients. Less weight the better.
Evo airfoil:
The CZ engineer started with the MS(1)-313, but we ran into the same thing everyone else using the new foils did: high pitching moment. We flattened out the aft camber to the limits of the aileron and flap design, and this gave us a foil with an approx 60KT wide trim band......
BTW: Glasair uses the LS(1) or GAW foil; Lancair/Columbia and Cirrus use the NLF foils, again all are modified in the TE area to reduce pitching, and also at the LE (Lancair and Cirrus) to tame the stall to certified limits.
The MS(1)-313 is supposedly about 40% laminar, where the 230XX is about 20%; more attached flow is probably better in just about any case. We haven't seen degradation effects that compromises performance to a large degree -- NASA says it (and other later-designed foils) perform more like the 230XX, or other non-laminar foils, with bugs on the LE.
Carry on!
Mark
Mark in no way am I putting down the Pert-tee (Texas for pretty) Evo wing or its numbers, they speak for them self, its faster. However your comment about filling in the cusp to reduce pitching moment caught my attention, since that lowers life and lowers l/d. Do you fly at a higher angle of attack in cruise than the "sport wing". The Glasair was slower than the QuestAir in part due to lower lift, filling in the cusp lowered lift further. Of course Glasair used a different airfoil than you did. I don't know enough to compare the difference. This goes back to the "NO FREE LUNCH" theory. Yes laminar flow wings have less drag but come with other issues. It's how you handle those issues & mitigate them which determines overall gain/loss.
Here's some experimentals (mostly) w/ laminar & odd ball airfoils:
Swearingen SX-300, NASA NLF(1)-0416
Stoddard-Hamilton Glasair III, NASA GA(W)-2 mod
Evo Wing Rocket, NASA MS(1)-313
Jones White Lightning, NASA 66-215
LINK
Aviat Millenium Swift, NASA NLF(1)-0414F/M1
Mooney 301, NASA NLF(1)-0315
LINK
Neico Lancair 320/360, NASA NLF(1)-0215F
Neico Lancair Columbia 300/400, (root) NASA NLF(2)-0215(H)/(tip) NASA NLF(2)-0215(D)
Wheeler Express, NASA NLF(1)-0215F
Neico Lancair IV, (root) McWilliams RXM5-217/(tip)NACA 64-212 **
Prescott Pusher, NASA NLF(1)-0215F
Sharp/Ericson Nemesis, NASA NLF(1)-0414 mod
Aero Designs Pulsar, NASA MS(1)-0313 mod
** The Lancair IV I think is faster than the Glasair III. Not sure what a McWilliams RXM5-217 is. The NACA 64-212 airfoil is a little infamous (used on BD-5). This airfoil is low-cambered and accounts for low maximum lift coefficient and sharp loss of lift at the stall. It's thickness is 12%. The max thickness is moved aft compared to the 230XX. Why they used it at the wing tip, I'm not sure. The Lancair IV reputation is being a HOT airplane. The SX-300 is a personal favorite of mine, but its approach speed of 105 kts!