My 12 is placarded for no aerobatics and no spins. Obviously this admonition is for pilots who are unable to properly spin the aircraft!
No. It has never been on wheels. I suspect that the rotation speed might be a bit slower on wheels with a normal recovery. You should be cautious about exceeding the rear limit of 20" when on wheels. Floats tend to make the rotation speed higher with the nose pointed more down, because of the mass being further from the vertical CG.
My experience was that (on wheels) without VG's I could only just stall the plane without power. Added VG's to the wing and the stall speed was lowered and found I did not have enough elevator authority to stall the wing.
So added VG's under the stabilizer and the elevator authority improved and I was then again able to execute a stall. This was all with some weight in the back. Added gap seals and could not improve it any more than i already had so i removed them. Not very scientific I know. But I was very impressed with the VG's under the stabilizer.
Interesting, how many MPH did the stall speed get lowered? Did the characteristics of the stall change with the VGs? Was it softer or more abrupt?
This does make a lot of sense since the elevator/stabilizer unit needs to be looked at as an upside down wing. It's lift is in a downward direction. With the elevator in the full up position there is a sharp angular change in direction at the hinge line thus generating turbulent air under the elevator reducing it's "down" lift. It is sort of like a wing with a flat upper surface and a hinge in the middle. Most definitely not very aerodynamically smooth. Filling the hinge line gap only reduces air flow down through the slot, but most of the turbulence and loss of down lift will still be there. I will go as far as speculating that if VGs were installed on the top of the stabilizer also, in the same manner as the lower ones, that it would be easier to raise the tail earlier in the take off run when loaded tail heavy.
Placing VGs on both sides of the fin on some twin engine airplanes is known to improve rudder power thus reducing VMC (minimum single engine control speed). So, it makes sense that the same would be true on the elevator.
I have long thought that the flat tail surfaces were not very aerodynamic and could use some improvement. If the stabilizer had curved upper and lower surfaces the air flow past the hinge line would be smoother. Granted the construction would be more labor intensive and Piper's objective was to keep the cost down. Look at the stabilizer that Doug Keller came up with for his flap STC. There also would be a slight drag reduction.
I have thought that a small slat attached to the leading edge, top and bottom, of the elevator would improve the airflow over the elevator. The VGs would likely be simpler and with less drag. What are the dimensions of the VGs which you placed under the tail?
I know when ACA put the 0-390 in the scouts they made the horizontal stab in a wing shape. The Cessna cardinal has a slot on the stab too.
Your cub looks great, have you been flying floats much this year so far? Ill have to come down on wheels sometime and check it out.
Tom
i did my first flights in my new tcow pa-12 this winter. i also could not get the wings to stall,i have VG's on the wing and tail and was thinking about the gap seals to try and increase my elevator authority.great info here it sounds like i'll keep my 250bucks and try the vg's on top to.
I can't get my brain around how that would work on a tail. would you need slats on the top and bottom?
I have lots of nose down just not enough nose up.full nose up trim stick all the way back all i get is a 38-40mph nose up decent with no stall.
This is Peter Annis's (skywagon 8a) Smith Cub
Hello Pete,
Would you comment on your interconnect system and fill procedure for your brake master cylinders ?
Also, what are you using to connect the rear brakes to the front ?
Thank you.
Jonnyo,
Those are North River master cylinders. Being a closed system, it is sensitive to temperature changes. Many users have complained about the nuisance of having to add or remove fluid. So, the two filler plugs and adapters were removed and replaced with brass needle valves which were connected to a "T" on the bottom of a reservoir.
https://www.amazon.com/Parker-Hanni...=2025&creative=165953&creativeASIN=B01BYLXPQE
The reservoir was made from a 6" long 2" diameter piece of clear plexiglas rod on a lathe.
The proper fluid level is set by opening the needle valve, pumping the brake pedal then closing the valve.
The parking brake valve is a 1/8" pipe ball valve from Ace hardware.
The front to rear connection is just a piece of steel tubing supplied by Back Country in their kit.