I visited a friend tonight to check on his progress on his soon to be flying 2+2. He just got done rigging his flaps and noticed what both of us think is an unusual interaction between the two flaps. Here is a video showing the concern.
http://www.youtube.com/watch?v=kBKxB4msRjc
Does this look correct to everyone?
The other Jeff
springs should be matched and very light,just strong enough to hold them retracted.
Last edited by Fortysix12; 07-10-2012 at 10:27 PM.
I couldn't see any left and right flap pulleys. Are they there?
Nevermind... watched from beginning and could stop the video and see. I agree, maybe spring tension not same.
Another thing I noticed is the Y connection is almost a T connection. Seems the bracket should be closer to the rear pulley.
Last edited by Bugs66; 07-10-2012 at 10:30 PM.
Hi Jeff,
I also have flaps on my 2 +2 project but still a long way from flight. Yours seems to be rigged differently than the model I'm using, the Pa14. On the 14 I believe the flap cable goes down each side of the fuselage just back of the door post. 14 owners chime in if I'm wrong here. Then across the floor and turn 90# to the flap handle. This is at least my plan. The Y connect doesn't seem to have anything to equalize the pull. If the springs are different that might explain the imbalance. What happens when the flap handle is pulled? Do the flaps both go down evenly? The set up you have looks a lot like the STC for flaps on a 12.
Not much help here, kind of talking through my design ideas.
Marty57
N367PS
Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
www.xanga.com/martyfeehan
I rigged my 2 + 2 pulley system like the PA-12...double pulley on the left side...then cross over...with the connection straighter, not a Y like in this example...will take some pictures when I get a chance...
On my 2+2 I ran both flap cables back and down separately . Then under the floor to the flap handle , which is center mounted between the seats. Turnbuckles at both flap bell cranks.
Cost an extra pulley or two, but gave me control over the adjustment and deflection of everything. Guess I'm a control freak?
Laz
when your flaps are up and you first pull the handle both flaps should start down at the same time you have to shorten the (Y) cable on the flap that starts first if there is any tension on the flap cable as you pull the main cable will center making on flap go down (Same as if you look back at water rudders on floats unless everything is set perfect one rudder will start up before the other don't matter on float rudders) hope you figure it out maybe i'm not seeing it all good luckOriginally Posted by jrussl
Steve C
That looks like normal operation to me with this type of system. When you are moving one flap and changing the load on one actuating cable, what do you expect the other cable to do? This cable system design allows the flaps to equalize each other. If this were a hydraulic system with one hydraulic line going to a "T" then a line to each flap actuator, the action would be the same as yours. For example the Republic Seabee has a hydraulic system which works the same as your mechanical system. The air loads in flight, including the prop blast when beginning the take off, will balance the flaps.
Now if you notice a changing wing heavy condition during flight while changing flap settings then you may want to change something. Your best bet is to be sure that the coupling plate which joins the flap cables to the flap pull cable is centered. This will equalize the pulling loads on all the cables and that seems to be the way you have it. Check that both flaps start to move off the up stops together and that they are at the same angle when full down. The rest will balance it self.
Why did you install that nylon fairing in front of the pulley? That is not necessary since operationally that cable will remain centered on the pulley and will not move side to side.
N1PA
I think it's too much of a T connection like bugs mentioned. I'm just guessing here but I would assume both return springs are anchored in the same place and are of the same tension.
Last edited by Cub junkie; 07-11-2012 at 07:15 AM.
I believe that setup will kill you. In addition to the unequal air pressure when slipping/skidding, what would happen if one of the flaps cables comes loose -- one flap will be extended and the other retracted and over you go...
That is just like a PA-18 installation. The angles are just a little different. And if one cable loosens, the other flap will retract by a proportional amount.
N1PA
I am often wrong. If you're interested, next time I go to the airport I can post a photo of what I think is a better way to run the flap cables.
That is how the system is designed! Mine is a version of your system and it works perfect. Fly square the air loads are square so will the flaps. If you slip they will deflect slightly out of square but you will hardly notice, if at all...
Thanks everyone for the great feedback. The "T" vs "Y" config is probably what is causing the exaggerated interaction between the two flaps. It sounds as though some interaction is normal. Changing the pulley config as some of you suggested is not really desirable at this point since the plane is already covered. Not sure about the nylon fairlead and why it is there. I will share all of your great feedback with my friend.
Laz, I too have a 2+2 project that I bought and it has the flap pullies right in the center, similar to the video. Doesn't help my plans for cargo space. Could you post a couple of pics on how your pullies are set up. Thanks, Peter
Posting Permissions
Reply With Quote
Bookmarks