Flap cables rubbing

[Bcone1381]

Help me understand the difficulty with the flap adjustment. I might be wrong, but you may be over thinking it. From what I am thinking....

1) In the Flaps UP position, the springs force the flap pushrod against the rubber bumper. So, No adjustment is needed. The flap cables might even be a bit slack when the flap lever is in the UP position. I don't see a need for any adjustment.

2) When I pull the flap lever with a small mis-adjustment in the lengths of the cable that attach each flap to the Flap Junction Plate, no big deal. The Flaps are connected to each other via the tri-angle shaped plate. So the load on each flap will be equalized by the plate shifting slightly one to equalize the tension in the two cables and thus equalizing the flap travel. Plans call for a turn buckle on each of those cables. I adjust the turnbuckles so the junction plate remains centered.

One adjustment you might want to look at is how far the flaps travel down when the handle is in the FULL down position. If it travels past the point where Bob designed it to be, it may cause a load in the structure above the design considerations. I set my flap cable tension so distance between the rear spar and the inboard flap lever in the fully deployed position meets what is called out for in the plans.

[svyolo]

The little voice in my head has been whispering "electric flaps" over and over.

[svyolo]

One of the gotchas that might be easy to miss, is the 0 degree flap setting, the pushrod needs to be resting (pulled actually) up against the pad on the tubing. If it isn't, or one side isn't, you can adjust the flap pushrod to zero, but in flight, with air loads, it might go farther up, past zero. Result - heavy wing.

I didn't realize how much force the flap springs would impart to the mechanism. You cannot properly adjust the cables without all 4 springs attached - not 1 or 2, but all of them. Which makes adjusting them (and making them) much harder. There is a lot of torsional flex in the torque tube. I ended up pulling the cable off of the pulleys, and sometimes removing a pulley, rather than remove the springs to adjust something.

The springs are also a bit hard to install and remove. I used pieces of 100# fishing line to pull the spring aft onto the arm, pulling the line straight back through the hole in the aft spar.

I will try tonight to come up with the actual procedure used to do all of this.

[whee]

Good work svyolo. Getting the flap and aileron rigging correct can be a trial of patience. It’s easy to get it “good enough” but that last little bit is tough. And we still won’t know if we got it right till the plane actually flies. Oh the joy of building😁

[svyolo]

I just spent way more time installing and adjusting aileron and flap cables than I thought I would. I decided to hang the wings one more time before I closed them, and wanted to make sure the linkages were "plug and play" when I hang the wings for the last time. Fuel line connections also.

Having the flaps and ailerons not installed (flaps especially), and the fuselage not covered made this a lot easier. Specifically, if the wing roots were covered with fabric, it would be more difficult to accurately measure distances when adjusting the flap linkages. Adjusting the left and right flap cables individually, also affect the opposite one. I now have the two sides moving the exact same amount, retracted and extended. The only thing left to adjust, is the flap pushrod.

Ailerons same thing. The linkage needs to be adjusted so that both sides operate the same. I clamped the aileron bell cranks in the square position, and made up the cables. Unclamp them, and tension the cables. Make sure both bell cranks are square at the same cable position. And make sure the cables aren't rubbing on the ribs (I had a couple that did).

I think if you did all this adjusting off of aileron and flap movement, you would be introducing another variable. You might adjust the aileron (or flap) pushrod to correct a mechanism misalignment. The mechanism needs to be adjusted first.

So far I am very glad I did this before the fuselage is covered. Hopefully I won't be unhappy I did it this way later. :<)

[22LD]

Thank you, Chris. That's pretty much what I came up with. I can't really modify anything. It's the geometry of the pulley in relation to the tube. The rub is very slight but still has to be addressed. I don't really have the option of using an Adel clamp on the tube (no good place to affix it). I have some very tough nylon tubing with an I.D. to accommodate the cable. The O.D. is sized so it fits snugly through the fair leads. I will make it long enough to extend enough past the front and rear fair leads to secure it in place with either a very small clamp or a couple wraps of safety wire.

[Chris In Milwaukee]

Not exactly the same position, but Maule had a similar problem with rudder cables. Any possibility the solution could be used if there are no adjustments you can make?

http://mauleairinc.com/pdf/servicebulletins/service_bulletin_17.pdf

Chris

[22LD]

I've run into a slight different issue with my left flap cable. Where it crosses over from tube from the outside fair lead to the inside fair lead it is rubbing on the top of the tube. Wondering if anyone has encountered this and if so what you might have done to resolve it. Thanks.

[swpilot3]

I had this same scenario. I got the inboard / outboard alignment as central as possible, but the flaps travel a long way.

I found the reality is the flaps never go down far enough in flight to make contact with the spar attach point. The contact isn't a big deal if there's no strain on the cables. I just put some tape into that area to buffer it. After a lot of flying, it hasn't left a mark.

Ah, that's very good to hear. Thanks Battson!

[Battson]

I ran into the same head scratcher. I just hung my wings for the first time and drilled them. The left side seems to be okay, but as you mentioned, the right side has the cable contacting the rear spar attach points in the flaps down position. I positioned the torque tube arm in and out to provide the best clearance in the gap, then I was planning to use a slightly bigger pulley to provide the proper clearance.

I'm very interested to hear what others have to say though.

I had this same scenario. I got the inboard / outboard alignment as central as possible, but the flaps travel a long way.

I found the reality is the flaps never go down far enough in flight to make contact with the spar attach point. The contact isn't a big deal if there's no strain on the cables. I just put some tape into that area to buffer it. After a lot of flying, it hasn't left a mark.

[TrueAirSpeed]

Thanks again! I'll look it up.

[Steve W]

Not sure. Look it up on Spruces website. SA362. The inside distance is much longer than a shackle and is quite slender compared to the shackle/thimble combination.

[TrueAirSpeed]

Good idea. How long are the fork ends?

[Steve W]

I used these fork ends to get the flap arm as close as possible to the root fitting for minimum deflection in the pulley groove. Had the cables made up at Spruce. It also allows more clearance against the arm in the retracted position.

[TrueAirSpeed]

Thanks for the comments.