Prop Wash

[MikeB]

How does one determine how far the 'prop wash' goes in the wing area? I've kind of searched through the 43.13 "bible" and can't seem to locate any information. I believe Bill Pancake told me four ribs out not including the butt rib. So instead of the fastener spacing being 4 5/8 it would be 2 5/16 in the wash area. I looked at the three Champs on our field this afternoon and noticed that one has the 2 5/16 spacing all the way to the aileron bay. My Champ (which I did not cover the wings on) goes about 6 ribs out. Another Champ is spaced four ribs on one side and three on the other. Because I have all new heavier .032 ribs with a 1/8" hole I'm using pop rivets in accordance with SL 85 and the pop rivets are a bit more pricy than 1/4" pk screws so I'd like to not use any more than necessary. Another thing I noticed is that two of the three Champs on the field have the 2 5/16 spacing on the out board aileron bay rib for whatever reason (???) My new rib is drilled for the 1/8" pop rivet at the 4 4/8" spacing.

Needless to say the Aeronca service manual is pretty blank on the subject but 'inquiring minds want to know'........ .

Thanks,
MikeB

[kyleb]

The factory drawing specifies using the close spacing on the two innermost ribs. As you pointed out, Bill has recommended going out either 3 or 4 ribs. People who extend the narrow spacing further out than that are doing it because of aesthetics.

[MikeB]

As they say............"after further review" I noticed both my Superflite manual and the Poly Fiber one say "three or four past the butt rib" so guess I'll stick with the four as I originally planned. This is my first wing cover job so I'm still in the 'learning and thinking stage'. The problem is complicated a bit as when I rebuilt the wing structure I also installed a set of 5 gallon Wag Aero wing tanks which also takes a bit of thinking.

"Onward and Upward"

Thanks,
Mike

[kyleb]

As they say............"after further review" I noticed both my Superflite manual and the Poly Fiber one say "three or four past the butt rib" so guess I'll stick with the four as I originally planned. This is my first wing cover job so I'm still in the 'learning and thinking stage'. The problem is complicated a bit as when I rebuilt the wing structure I also installed a set of 5 gallon Wag Aero wing tanks which also takes a bit of thinking.

"Onward and Upward"

Thanks,
Mike

You oughta post some pictures of that installation, paying particular attention to any not-so-obvious details. A pair (or at least one) of the WAG tanks are probably in my immediate future, so I'd appreciate the pointers.

[MikeB]

Kyle,
I can do that. There are a couple of pictures under my posts "Progress/moving along". Dennis off this site also gave me some pointers when I was in the process of installing the tanks. One thing you find out quickly is that while the installation process is fairly easy, they don't fit all that well. I wound up having to move the second rib over (after nailing it in place) so that tanks would fit between the ribs. I think Dennis had the same problem. You also have to reverse a couple of bolts in the wing attach plates. I also had a problem with a weld overlap that caused a clearance problem with the butt rib. The instructions that come with the kit leave a lot to your imagination which may or may not be good. Having said that, I don't want to give the indication that they're a poor choice. Just that you need to be thinking ahead which isn't always my strong suit anyway. Probably for the money they're probably as good as it gets unless you can come up with one of the original 5.5 (??) wing tanks. WAG makes one similiar. I think you probably pull the wing and the butt rib to slide the tank in, rather than fit it from the top down in the case of the STC 5 gallon kit.

MikeB