Air Conditioning - Installing a window a/c unit

I bought a small 5,000 BTU window a/c and want to install it. I assume a plywood board nailed to the window sill is the way to do it. This window sill is only about 2-1/2 inches wide. I think more support would be good to have under the plywood on the portion of the 'sill' that slopes downward toward the outside of the house for rain to drain off. In other words, putting the entire weight of the a/c on the narrow sill even if it has huge long nails in it doesn't seem right. This a/c is light, only about 45 pounds or so but I still think a secure platform is needed.

My questions are basic in the extreme, so bear with me. What thickness plywood, what size nails would be recommended. 3/4" plywood or 1/2", for example. And what would these giant nails be called? Framing nails or what, for example. I will appreciate your input. Thanks.

Bette
Depending on how the weight is distributed in the A/C, adding that plywood could actually make it worse, due to the lever action of the added length of plywood. You'd be much better off using a support leg kit, or building something that angles down to the ground. Even maybe a chain and eyebolt type thing up to the soffit of the house.

The plywood idea seems to make sense at first, but imagine attaching it, then pushing down on the outer edge, it would apply much more force than just pushing on the edge of the sill.

If its a new A/C, check the install instructions. If its used, see if you can find them online. The smaller ones probably don't need additional support.

Thank you Vic. I see what you mean about the plywood needing support. bette