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Need Help RV-7 Flap adjustment

R

Rockyjs

Well Known Member
Patron
I checked the database, but could not find the info I need. Is there an internal flap actuator adjustment limiting the travel of the screwjack that I've overlooked? I have a total flap travel of 47 degrees from free spinning of the jackscrew. This range of travel remains the same no matter what the length of the links connecting the flaps are set. Adjusting the length of the links merely sets a reference point where the travel is. The only way I see to change the flap range is to alter the geometry (not an option), or set a limit switch to electrically stop the travel at a pre-determined place in one of the directions and use adjustment of the connector links to get the jackscrew to free spin at the opposite end.
Is this correct?

Thanks
Rocky
 
Rocky,

IIRC you probably won't get the full 47* when flying and under pressure. I don't know what the max flex will be, but I would imagine it to be closer to 40* than the 47* when loaded up in flight. I really don't think that it will be a problem as long as you have installed it correctly. Too many of them out there flying.

The only issue might be the travel on the jackscrew. I don't know what mine is but somebody out there has to have measured it.

Just my $.02
 
Use a limit switch

The way I set my flaps was to adjust the pushrod lengths to achieve maximum specified flap deflection with the actuator at full stroke. I then found that it is necessary to limit up travel, which could possibly be done with a hard stop, but which I am going to do with a limit switch.

Actually, I am gong to install two limit switches for redundancy, one on each flap, that will be wired in series.
 
Adjust the linkage for full up flap when the flap motor starts free wheeling. Flaps even with the ailerons when they are neutral and most of the time the flap skin overhang will be flush with the bottom of the fuse if the incidence is close to spot on.

Whatever it ends up full down, leave it alone. No need for switches and hard stops. The motor is intended to decouple from the screw and free wheel at full up and full down.
 
A word of caution.

Brantel said:
Whatever it ends up full down, leave it alone. No need for switches and hard stops. The motor is intended to decouple from the screw and free wheel at full up and full down.
Click to expand...
With the flaps full down, make sure that you still have plenty of overlap at the forward edge of the gap seal. It's very easy for someone on the ground to "bump" the flaps and pull the leading edge out from under the wing skin. You DON'T want this!
I usually limit the down travel to about 38 degrees.
 
No flap adjustment

The flap motor determines the flap travel. What you get, you get. There is no adjustment available or necessary. Full flaps are almost all drag and very little, if any, lift. If you get 47 degrees, just leave it that way. Make sure that they are even with the neutral ailerons when they are up and let the motor take care of the down position.

Bruce Reynolds
RV-6A
 
You can adjust it - sort of

The motor will stop when it reaches a force limit. Set the down travel to ensure you will not have a pop-out event like I did. Mel's right - you DON'T want that to happen. The upward travel will stop when the overlap hits the belly. You can do this with the lock nut on the jack screw then be sure to safe-tie it per plans.
 
Thanks everyone! I'll adjust the flaps to a max of 38 degrees per Mel's advice.
What have people used on the fuselage or flap belly skin for anti-chafing?
 
45 or 47 degrees is too much. If you need more than 40 degrees you are doing something wrong. Mels got the right idea. Just because every one else is doing it is not any justifiction for doing it also. In my RV3 I have 15 and 30 degrees. Full flaps (30) and a go around is a hand full and it loads up the flap mechanisim pretty quick. If you try it in a manual flap a/c you will see what I mean, the pressure on the flap lever increases dramaticly.
YMMV
tm
 
Bruce Reynolds said:
The flap motor determines the flap travel. What you get, you get. There is no adjustment available or necessary. Full flaps are almost all drag and very little, if any, lift. If you get 47 degrees, just leave it that way. Make sure that they are even with the neutral ailerons when they are up and let the motor take care of the down position.

Bruce Reynolds
RV-6A
Click to expand...

I guess you guys did not read Bruce's post. Since he is a Van's employee that works in tech support, I think you should listen to him.

If you want to go thru the complexity of putting in limit switches, go ahead and do it (major overkill) but I would never run this setup in a condition where the motor would be stalled by hitting a hard stop. This is a recipe for a smoked motor or worse!

Adjusting the stop nut does nothing more than adjusting the linkages. Either case, you have the same travel unless you bottom it out against a hard stop. The only thing that would affect total travel is a hard stop or a change in geometry of the system.

If you have your incidence set correctly and the flap overhang just kisses the bottom of the fuse, and the flaps are even with the ailerons when in neutral, and the flap motor is freewheeling up at this point, you should not have a problem with too much down flap at the other end.

I just went thru the rigging of mine a few months ago and I know that there was not excessive down and there was no way the leading edge of the flap could come out and over the trailing edge of the top wing skin. No limit switches and no hard stops. Just several hours of getting everything rigged properly.
 
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Disagree about no adjustment

Brantel said:
I guess you guys did not read Bruce's post. Since he is a Van's employee that works in tech support, I think you should listen to him...
Click to expand...

Bruce is one of my favorite support guys at Van's. That said, he also pointed out to me that some guys have to trim the overlap to get the flaps and ailerons to agree. There must be a lot of variability.

Mine is a QB and I used the prescribed method of setting the ailerons. and the wing incidence was carefully done and then checked with a digital level. Still, the full down position of the flaps was too much and I paid the price at around 150 hours (see my previous post). That it took so long is a good argument for building in some safety. I thought I was OK.

The choices are few. Accept the risk of a popped-out flap, use the hard stop at the top or install fancy electronics to sense and limit position. I'm sticking with the simple version.

I think the only thing that stops the flap motor no matter what you do is the force when it reaches the end of its travel. Any experts out there on what the motor's wiring is doing?
 
hevansrv7a said:
I think the only thing that stops the flap motor no matter what you do is the force when it reaches the end of its travel. Any experts out there on what the motor's wiring is doing?
Click to expand...

The motor does not stop at either end of its travel unless you jam it against something before it reaches the end, it continues to turn at the end of travel, there is a decoupling mechanism inside that disconnects the screw.

The beauty of homebuilding is that you can build your's however you want. That being said, if your stalling your flap motor against a hard stop at the top or bottom, each time you hit that stop with the power on, your placing excessive forces on the system, stressing your motor, and driving higher currents than normal thru the electrical system. Over time this could lead to premature failure of the motor, damage to the mechanics, and or electrical problems. If you happen to get a stuck switch during one of these times while traveling to your hard stop, your almost guaranteed to pop a fuse or breaker (if your lucky) or smoke the motor or worse cause a fire.
 
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Flap adjustment

Would be nice to indicate how to limit the flaps to 37-40 degrees and keep a little more flap skirt under the wing.
TIA, Kirk
 
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