flap return spring - I'm stumped

[gkremers]

Here's a pic of the root rib. I bonded a small piece of aluminum to the rib web just for abrasion protection. Not sure if I really needed it but it's easy and cheap insurance. The threaded rod will be cut off, the end will be secured with lock nuts or jam nuts against each other. You'll also noticed I did open up the hole in the false rib, I think Steve was correct and it was easy to do now.

Gary

[SheepdogRD]

Good job, Gary. That's very clear, and it should be easy to follow.

[stede52]

Nice work Gary, That will give you all the tension you'll ever need

[SheepdogRD]

I'm finally back on this part of the build. In re-reading the thread, I followed xpflyr's pointer to this thread: http://www.wingsforum.com/viewtopic.php?f=218&t=18900. It contains a page from the "old" manual that showed a different attachment of the flap return spring. Mounted at the wing root, the spring runs between a tab on the flap spar and a tab under the head of the rear wing spar attach bolt.

Flap Return System - Just Manual Fig_6_13_2a.jpg (56.07 KiB) Viewed 2585 times

Flap Return System - Just Manual Fig_6_13_2b.jpg (19.15 KiB) Viewed 2585 times

I see some advantages to this system:

Easier to install.

Eliminates holes in the leading edges of the flaps and the trailing edges of the wings.

Easier to service.

I'm wondering why this system was abandoned in favor of the more complex one used today. One guess would be to eliminate asymmetrical forces on the flaps. Anyone know about this?

To mitigate the possibility of spring stretching from gusts catching the flaps, I'm looking at putting a small bumper protruding from the hinge plates at the flap control arm, limiting the arm to 45 or 50 degrees of travel. I think an adjustable end would be wise, perhaps with some resilience. Any suggestions or comments?

[SheepdogRD]

A correction to the post above: It appears that the spring runs between a tab on the flap spar and a tab probably attached somewhere along the rear wing spar, perhaps at one of the rivets along the wing joint doubler.

[EchoWhiskey]

I unearthed this upgrade.

Should the stock list require 4 of the bushings?

[SheepdogRD]

I was hot on that upgrade, and was installing it. But then Dane (danerazz) came up with his flap spring mod (here's a link to one of the threads on it: http://www.wingsforum.com/viewtopic.php?f=218&t=23448.

Dane's design is simpler, lighter, easier to install, easier to inspect, and inexpensive. Hard to beat all that. I installed his kit and skipped all the other much more painful stuff.

[EchoWhiskey]

Thanks Richard,

Another baffling case of:

Why isnt that original equipment? The proposed method and materials are obviously wanting. Add to this the fact that these are easily accessible/ replaceable