No thanks
pierre smith said:
Hi Alan,
Neat tuft tests, buuuutt wait! I spoke with an aerodynamic engineer/RV builder about a retrofit tapered wing for the RV series. He said that it was easily workable to make a bolt-in replacement wing. He also went on to say that the landing config stall speed vs. the flaps-up stall speeds are too close and can be further optimized by having less wing area, larger fowler type flaps and smaller ailerons. Yield could be 25 MPH added cruise speed and 10 MPH higher stall.
Huaaaa? "He also went on to say that the landing config stall speed vs. the flaps-up stall speeds are too close"
That is true but its also intentional. Van designed the wing, flaps and ailerons intentionally as they are. There are always better ideas but rarely do you strike such a beautiful balance of compramises that makes the RV such a joy to build, fly and own.
Your friend is right, the RV's stall speed flap down v. up is small, about 3 mph but so what, the stall speed is already low. Fowler flaps are going to be complex, heavier, harder to build and more costly than the light simple hinge flaps we have.
Van's RV cruises and tops well over 200 MPH but has a stall speed in the high 40's or low 50's of MPH, basically C152 stall speed but twice the top speed. That is a ratio of 4 to 1, max to min speed. How slow do you want to go, and VERY FEW planes have this ratio.
The NACA 23013.5 airfoil with constant chorde/thickness is a great airfoil. Have you built a tapered wing? Again more complex, expensive and harder to build.
This IDEA has been done and is being done> Teamrocketaircraft.com sells QB Rocket kits, similar to the Harmon Rocket. They offer a new Evo Wing as your friend describes. The standard Rocket uses a RV-4 wing but is cliped about 14" (104 verses 110 sq-ft area).
The standard "Rocket": top speed: 250 mph, cruise speed (75%@8k): 230 mph, stall: 54 mph, wing area: 104 sq-ft.
The Evo wing: top speed: 265 mph, cruise speed (75%@8k): 240 mph, stall: 50 mph, wing area: 102 sq-ft. The Evo wing is about $5,000 more.
The bottom line is +15 mph top, +10 mph cruise -4 mph stall, which is nice but is it worth it. Takeoff/Landing are listed as the same. Handling? There is some info on their teamrocketaircraft.com web site. The negatives are slower roll rate and smaller CG range, but it sounds like it handles nice overall.
Smaller ailerons? No thanks.
Many planes, Boeing jets have fowler flaps, double and triple slotted fowler plus leading edge "high lift devices". Its all good but it adds weight and complexity.
The overall performance, handling and joy of a RV is a delicate balance of many factors, not the least is kit cost and build difficulty. A constant chord / thickness wing is a joy to build. A new wing will make it a different handling plane, and probably not a "RV" feel. Speed is great but if you have to live with it as a "sport plane" there are other qualities that are as important or more important.