Inspection Holes

[6319]

My C-120s wings were "metalized" in 1961. There were 4 inspection holes placed aft of the rear spar in each wing. I am contemplating putting more inspection holes in the wings due to mouse intrusion. Cutting 4" inspection holes in the very thin aluminum could be a disaster without the proper equipment. Has anyone had the pleasure ? ps I have done everything to keep the mice out, tailwheel on a bucket, mothballs, dryer sheets, and victor traps. They still seem to love the 120.

[6643]

They crawl up the gear legs and sneak in where the legs enter the gear box. If you can keep them out there and put the tailwheel on a plastic bucket you'll be successful, as long as they can't fly.

Another place they go that is problematic is under the front floor boards.

Once, years ago, I went in the hangar and spied a mouse staring down out of the outboard inspection hole. I figured out where it got in and corrected the problem. A week later there were 4 dead mouse pups on the floor under the inspection hole. There's still the remnants of a nest in the wing tip...

Cutting the holes can be difficult. A hole saw is the easiest thing to control. A two legged fly cutter is a lot more difficult and a single legged fly cutter is downright dangerous.

[8224]

Cutting inspection holes in thin aluminum is very difficult if not done correctly. I use a single blade fly cutter mounted on my battery powered (20 v) drill moter. The secret is reinforcing the “ bearing area” of the drill bit shank in the thin skin. If not reinforced, the skin will “Waller” out before the hole is cut and then bad things start to happen, very quickly. After the 1/4” pilot hole is made I attach a predrilled piece of hardwood, oak,maple, etc to the skin inside the cut line with PK screws. When the hole is cut, the whole assembly falls out .
Steve Hawley

[6319]

Thanks Steve, My problem is that I can't access the inside to place the wooden piece. I do identify with your term "waller" and I can see that alum skin wrinkling. Harbour Freight has a 3" dia hole saw with grit edges instead of teeth, I'm looking at it although it's only 3" dia. I have never used the "nibbler" , a hand tool and not sure of how it would work cutting round holes from underneath the wing. Save your back muscles lifting the tail to put it on a pail, it doesn't work. The old fashioned Moth Balls worked best but you can't buy them anymore.

[6643]

I do identify with your term "waller"

I think he means "wallow".

Save your back muscles lifting the tail to put it on a pail, it doesn't work.

It did work for me, until they chewed through the rubber seals around the gear legs.

I hate meeces to pieces...

[5115]

Having access to the inside, a panel hole cutter would be great for that.
https://www.aircraftspruce.ca/catalog/i ... kkey=34593

[5115]

I thought I had a picture, but cannot find it. will try to explain it. For mice, what I have seen doing. You take a piece of thin galvanize steel sheet from home-air-depot, you cut it, lets say 12in x 48in, put it down on its long edge circling the gear tire and clamp the ends together to close the loop.

That should make a slippery barrier that the mice cannot climb to access the tire and landing gear. Do that for each tire and you should be find.
Very easy to remove and put back before and after each flight

[6319]

Found a 4" diamond coated drill bit hole saw on e-bay. It has no teeth, just grit for a cutting edge.Going to do tons of experimenting before using it for real.

[8224]

The “reinforcing” hardwood should be secured to the outside of the thin skin for convenience using at least three PK screws. The hardwood piece can then be detached and used again. I have found that a drop or two of oil makes the wood last much longer.

[6319]

Thanks Steve, I'm wondering if anyone has actually put more inspection holes in their metalized wings. I'm interested in looking at some fabric wings to see where the inspection holes are. Seen lots of 140s but never studied their wing inspection holes. The Ercoupe has 32.