False bottom rib

[jiott]

I believe the SS7 kit option for bottom false ribs comes with 3 ribs per bay. That is what I used, but I see from this thread that some folks are installing 4 per bay. I think that is overkill, especially if you have a good tight 350 degree shrink on the fabric.

[Flyboy66]

I believe the SS7 kit option for bottom false ribs comes with 3 ribs per bay. That is what I used, but I see from this thread that some folks are installing 4 per bay. I think that is overkill, especially if you have a good tight 350 degree shrink on the fabric.

Are they fabricating the extra ribs or ordering them from the factory? I cant see that it would be worth the time trying to fabricate what I presume is a very inexpensive part to buy.

[av8rps]

Based on what I see with my Model 4-1200, I'd put 4 between each bay even if only 3 are recommended. At higher speeds the fabric pushes up causing drag. So closer false rib spacing would alleviate most of that.

Also, make sure to put false ribs on underside of fuel tanks too. Mine doesn't have those and at cruise you can look right out the window and see the fabric pushed up tight against the bottom of tank, not following the airfoil shape of the rest of the wing.

The minimal weight gain would be more than offset by increased cruise, and fuel efficiency in my opinion.