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Thread: Flap extension

  1. #11

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    Default Re: Flap extension

    Quote Originally Posted by Steve Pierce View Post
    I would not shorten a PA20/22 aileron from my experience. Moving it outboard to the tip of a squared wing does help give it adequate aileron response though.
    That was my thought on shortening moving to the tip will improve enough to make up for it. I also have a Certified pacer with the squared tips and yes it does suffer due to unaileroned wing ends.

  2. #12
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    Default Re: Flap extension

    My experiences regarding increased drag.

    I flew my converted Pacer years on Univair gear covered with fabric. When I removed the fabric the change in cruise speed was not noticable. Recently, I converted my gear to Super Cub gear with the Trimmer STC and I was pleasantly surprised to find out that my cruise speed was not noticably changed. (If you look at the Pacer gear and compare it to the Super Cub gear the cabane vee obviously adds drag but you eliminate a major strut on the Pacer gear. You also clean up the belly significantly. I found the outcome is a wash). I change my tires every summer from my 25 inch Goodyear's to my 29 inch Bushwheels, my cruise speed is not noticabibly effected. Collectively, these changes make some difference. But, not anywhere near 5 mph, for my plane. It all comes down the the inverse square law. Increased drag is not proportional to decrease in speed.
    Last edited by Stephen; 01-25-2023 at 01:59 AM.
    "You can only tie the record for flying low."

  3. #13

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    Default Re: Flap extension

    Quote Originally Posted by PACERGUY View Post
    Cub gear is one of the big things that slow them down. PA 12s and Pacers will slow down quite a bit when you start adding Cub gear to them. If you put spring gear on a Cub you can increase cruse 10-15 mph. The angle of incidence is not that big of a factor, info from PA12 pilots that changed to cub incidence the tail will just fly different But now windscreen angle can effect speed. Covered gear and fairings can get you some speed. Every plane is different and one small change on any part of the plane can have effect on the entire plane. If it is only a few inches just push that last bay out to match the Aileron length. If you want to strengthen the rear spar area look at a full wrap around false spar like Javron does. " Just for clarification what do you mean by additional twist of the rear spar ".
    DENNY
    Well I would think increasing the length from 52 to 81" would produce more up lift at the back of the wing through the hinge supports and false spar causing additional twist between the 2. That is the false spar and rear spar especially in the fuel tank area with no ribs to carry that load to the front spare.

  4. #14

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    Default Re: Flap extension

    Quote Originally Posted by nimdave View Post
    Well I would think increasing the length from 52 to 81" would produce more up lift at the back of the wing through the hinge supports and false spar causing additional twist between the 2. That is the false spar and rear spar especially in the fuel tank area with no ribs to carry that load to the front spare.
    Years ago (like back in the 1960s) a lot of folks would rig the flaps on TriPacers with some reflex to get more speed, kind of like the Maule MX-7, until they started finding rear spars with a twist at the inboard end. That practice has long since been discontinued!

  5. #15
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    Default Re: Flap extension

    Quote Originally Posted by nimdave View Post
    Well I would think increasing the length from 52 to 81" would produce more up lift at the back of the wing through the hinge supports and false spar causing additional twist between the 2. That is the false spar and rear spar especially in the fuel tank area with no ribs to carry that load to the front spare.
    Boxing in the false spar area along the flap area and adding 1 inch angled aluminum to both sides of the aft spa will meet the increased load requirements. Another safety solution is to lower your flap extension speed speed a few mph. Air speed has the biggest effect on loads. That may be why using reflex flaps are problematic. They are used at cruise speeds. Remember the STC allows for 90 inch flaps.And, was engineered and tested.
    "You can only tie the record for flying low."

  6. #16

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    Default Re: Flap extension

    Quote Originally Posted by Stephen View Post
    Boxing in the false spar area along the flap area and adding 1 inch angled aluminum to both sides of the aft spa will meet the increased load requirements. Another safety solution is to lower your flap extension speed speed a few mph. Air speed has the biggest effect on loads. That may be why using reflex flaps are problematic. They are used at cruise speeds. Remember the STC allows for 90 inch flaps.And, was engineered and tested.
    I keep comparing to my son's Maule M5, it has longer flaps and shorter ailerons than mine (and a 1.5" longer cord) will have and uses 1 bell crank. The flaps are however fully skinned. I plan to fully skin mine and use 1 bell crank at the stock location. I do plan to reinforce the rear spar with trimmed angles as well which I believe are there to prevent spar buckling.

  7. #17
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    Default Re: Flap extension

    Quote Originally Posted by nimdave View Post
    I keep comparing to my son's Maule M5, it has longer flaps and shorter ailerons than mine (and a 1.5" longer cord) will have and uses 1 bell crank. The flaps are however fully skinned. I plan to fully skin mine and use 1 bell crank at the stock location. I do plan to reinforce the rear spar with trimmed angles as well which I believe are there to prevent spar buckling.
    I think Maule gets away with a shorter ailerons by increasing it's cord. The stock Pacer actuator is on the inboard hinge. My 90 inch flap has three hinges, I chose to used one actuator on the middle hinge. A long flag with an inboard actuator may place a significant torsional load on the flap.
    Last edited by Stephen; 01-25-2023 at 04:53 PM.
    "You can only tie the record for flying low."

  8. #18

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    Default Re: Flap extension

    Quote Originally Posted by Stephen View Post
    I think Maule gets away with a shorter ailerons by increasing it's cord. The stock Pacer actuator is on the inboard hinge. My 90 inch flap has three hinges, I chose to used one actuator on the middle hinge. A long flag with an inboard actuator may place a significant torsional load on the flap.
    I fully agree with you and was planning to use the actuator at the center hinge point but after realizing the Maule with the longer flap with longer cord was using the actuator at the same location as the pacer. I think fully skinning the flap as the Maule will account for the twisting of the flap.

  9. #19
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    Default Re: Flap extension

    Quote Originally Posted by nimdave View Post
    I fully agree with you and was planning to use the actuator at the center hinge point but after realizing the Maule with the longer flap with longer cord was using the actuator at the same location as the pacer. I think fully skinning the flap as the Maule will account for the twisting of the flap.
    I agree, a metalized flap will better withstand torsion.
    "You can only tie the record for flying low."

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