Inboard fuel tank rib hole...

[Gregg Brightwell]

The big one..... My flycutter won't quite go big enough. Is there a plan b option that is better than a jig saw? It's a touch over 5".

2nd question... I am not one to deviate from plans, but how important is the 1.5 inch diameter for the usage and fuel transfer holes for the interior ribs? I have a nice 1.125 hole saw that would work great for these, and it seems as if that would be plenty big. I can't imagine that a 1.125 hole would slow down refueling. Any of you have a reason why this is a bad idea? Other than the obvious one.....not per plans.

I should mention that even with a really slow drill press, I am still terrified of the flycutter. It bites.

Gregg

[Mel]

Keep in mind that the area of a circle is mostly around the edges.
A 1.125" dia hole has an area of .994".
A 1.5" dia hole has an area of 1.77". That's quite a difference.
I certainly wouldn't go any smaller than 1.5".

[JimWoo50]

Especially if you drill the large holes in the ribs. I recently had one of my tanks off for repair and added a 5" diameter hole in the outboard most rib to facilitate fueling. Before adding that hole I had to add fuel slowly to allow it to flow into the adjacent bays. I used the forward circle stamped on the rib as a guide. If you don't like the fly cutter drill around the perimeter of that circle with a 30 drill bit (about 70 holes) and pop the middle out. I had to do it like this in my completed tank and it's not as bad as it sounds. Clear the edges up and good to go.

[David Paule]

See http://www.vansairforce.com/communit...ad.php?t=91463

It's a safe alternative and works great. It has a minimum hole diameter of about 2". I run mine from my air drill.

Dave

[YellowJacket RV9]

I made mine with a bunch of unibit holes around the perimeter and then used a dremel to smooth the edges. Still tedious but not bad.