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Thread: Benefits of VG's for stock PA12?

  1. #1

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    Benefits of VG's for stock PA12?

    I know VG benefits have been largely discussed, but I need some opinions on a specific question. I fly a stock PA12 with 115hp engine and TrickAir skis (love em)in Minnesota. The "approved" budget does not allow for any significant mods like big engine, flaps, etc. To be honest I probably couldn't really justify any of those mods for the flat land flying I do here anyway. However, at heavy weights and with bad snow conditions, the takeoff performance can be sketchy. Not a very experienced ski flyer, but it certainly seems to help when I can lift one ski out of the snow during takeoff, then accelerate pretty well. Would adding VG's allow more aileron authority to help lift that ski out of the snow? That's the big question. Would they also get the tailski out of the snow?

  2. #2
    j5mike's Avatar
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    We put VG's on a J5 with a 0290 engine and pressure cowl. Very marginal gain on takeoff if any but really improved the landing phase as to keeping the air attached to the wing at lower speeds. It also improved the aileron and rudder authority in the landing phase at lower speeds and high angle of attack which is what it was designed to do. Before VGs we would run out of aileron and rudder right before touchdown which was problematic in a crosswind or gusty conditions. Not anymore. Worthwhile mod just for that reason.

  3. #3
    windy's Avatar
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    My PA-12 was stock when I bought it. VGs were the first mod of many that were added to my PA-12. They made the most improvement in performance for the least amount of $$. With high density altitudes here in Utah, the ground roll was shortened & could land at slower speed. Might not be such a noticible improvement in the flatlands. VGs didn't help in getting tail off the ground any quicker & didn't help climb performance. Before VGs, the stall used to break & it would hold a spin nicely. After VGs, no stall break, just a lot of sink/mush & no more spins, it only spirals & bobs if cross-control held. Extra margin of safety now with VGs, very worthwhile.
    windy

  4. #4

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    My 12 was mostly stock when I got it except for an 0-320. Before putting the vg's on I went out and did 16 stalls at the main compass points in different power configurations. The next day after the vg's were on I went out and repeated the stalls. Across the board the numbers all lowered about 4mph. The biggest change I noticed was on landing and some on take off, not that I noticed the 4 miles per hour a lot but I really noticed the full feel of the ailerons all the way down to the lowest of speeds. And as wendy said-the best mod for the money I've ever done. You won't regret it, unless you don't do it soon enough.

  5. #5
    Gordon Misch's Avatar
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    I added Micro VG's and the Crosswinds leading edge cuff at the same time, so I don't know how much to attribute to either, but with the combination (and flaps) I almost can't make it stall. The cuff STC says "intentional spins prohibited", so I haven't tried, but what Windy says makes sense. It just bobs along with the stick all the way back - won't break without quite a bit of zoom to aggravate the situtation. I haven't played with ailerons at absolute minimum speed but rudder is very effective for keeping the wings pretty much level. A departure stall with full power is a crazy deck angle with the airspeed indicating closer to zero than 20. And with half flaps it's fairly easy to maintain level flight, including gentle maneuvering, while indicating 20 (indicated, statute).
    Last edited by Gordon Misch; 11-10-2013 at 11:47 PM.
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  6. #6
    aviationinfo's Avatar
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    The biggest change in my plane was that the tail flies quite a bit earlier in the takeoff roll. Mr. Piper gave the airplane a great wing but I don't think the AoA in the three point attitude with stock 12 or 18 gear can make use of all the great properties. The wing will fly nearly as soon as the tail does but it would do a lot better with a higher AoA perhaps with extended gear and larger tires.

    Beyond that, the stall speed definitely decreases and the most noteworthy thing about it is the airplane feels solid almost all the way down to the stall.

  7. #7
    C130jake's Avatar
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    Just put VGs on...tell Patty it is FAA required...and start saving for a bigger motor.

    Jake

  8. #8

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    So far I calculate 5 "yes" votes and no dissent. Still unclear how much they will help on skis, but doesn't sound like there is any downside. I will heed the advice of my elder friend Jake, and start coming up with a plausible story.

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  10. #10

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    I don't think there is a downside to VGs on a PA12. i put them on our PA12 (Micro VGs) and they made a noticeable difference on takeoff,landing and stall.
    On takeoff much more stable.
    Same on landing.
    No stall just a slow rate of descent controlled with power.
    I was very happy with VGs on my 12.

  11. #11
    Chuck Avon's Avatar
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    I know we are talking about a PA12 but I put a set of Micro VGs on my Tcraft and every thing that has been said about them on a 12 also happened on my Tcraft.Cheapest mod biggest change for the buck.

  12. #12
    algonquin's Avatar
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    Lost the engine in a PA22-20 Pacer , still believe it was the VG's that allowed the plane to slow with a deck angle that the tail wheel touched down and dragged thru the muskeg 15-20 yards before the mains came down. The controls remained effective right down to the mains touching .
    I'm building a PA 12 now and will have VG's on it. Just my 2C.

  13. #13

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    Can't say if VG's would help on T/O as they were just one of many mods on my 12....but a benefit that will undoubtedly apply is that you will have aileron/elevator (depending how many/where you put the VG's) as long as or as soon as the aircraft is moving (just a slight exaggeration). I haven't run out of control authority with VG's and (as posted earlier), even with a pig of a -12, it is darn near impossible to stall the -12 without a substantial degree of whip.....suspect the VG's play a large role in that effect.

  14. #14
    Jerry Burr's Avatar
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    63M. I will submit an experienced opinion. I don't think that V.G.'s as the only change on your Trick skis will change much. You will need even a small increase in AOA on takeoff roll for them to work at their best. I was the "trouble shooter" for Micro on the initial Cub V.G. sales. Almost to the person the airplane had a large tail wheel, highly arched tailspring and stock wheels. Usually a larger tire or longer gear worked for them. The big tires won't work for you with the Tricks. Longer gear is great but expensive. My suggestion is to locate a worn out or used tail spring and have it de-arched as much as possible, and only use it with your tail ski. Affordable and would probably work. You didn't mention if you have flaps. In the wet snow we have here, I usually jack the Tricks out of the snow with the flaps. Hold the button down and pump the flaps like a jack. Pull on some flaps, bleed them, pull them and it will usually lift out much faster. Practice somewhere safe. Good Luck. Jerry B.

  15. #15

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    Jerry,
    no flaps on this plane. I do have 8.50 tires which helped increase the AOA for takeoff a little. I also have the small original Maule style tail wheel, which I like because it is light and never needs air. I have a tail ski that works with that tailwheel.
    The responses to my question have convinced me to get the VG's for all the other benefits, even if there utility on takeoff isn't what I hoped for. I'll try to collect some before and after data for the group when I install them. Thanks for the input

  16. #16
    nanook's Avatar
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    I've always used flaps to pop a 12 or 18 off with skiis. I have no idea what conditions you are operating your ski plane in. If it is always a hard surface you may be able to unstick a ski with aileron. If it is a soft snow, I wouldn't recommend trying to aileron pop a ski at a time out. Rolling the weight over on one ski to lift one, just adds drag. Spreading the weight evenly between both skiis will get them going faster and higher up on the snow. Getting the tail up as quick as you can and then dropping the tail when you reach flying speed is going to get you off the snow the quickest. Putting VGs on to do as you describe, is going to be a big disappointment as I see it.

  17. #17

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    I ordered mine yesterday from ABW.

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