airbox chafing

[Build9A]

At my last oil change, I noticed that the airbox on my 0-320 carburated engine had minor chafing at the lower left where it is rubbing against the cowling. It will probably worsen as the engine sags. My plane is painted, so I don't want to modify the cowl. If I slightly modify the airbox, what material is used? I vaguely remember that it's not fibergalss, so I think that a different resin and material is needed if I modify it. Is a slight airbox mod acceptable and what problems, if any could it cause? thanks

[kevinh]

Originally Posted by Build9A

At my last oil change, I noticed that the airbox on my 0-320 carburated engine had minor chafing at the lower left where it is rubbing against the cowling. It will probably worsen as the engine sags. My plane is painted, so I don't want to modify the cowl. If I slightly modify the airbox, what material is used? I vaguely remember that it's not fibergalss, so I think that a different resin and material is needed if I modify it. Is a slight airbox mod acceptable and what problems, if any could it cause? thanks

I too had a (very) small amount of rubbing on my airbox - even though the clearance is pretty good when the plane is not running. I suspect there is a slight shake at start/stop. The airbox is fiberglass, so I just cut an oval out on the side, put some masking tape on the inside to serve as a crude mold, then layed up a few layers of bid fiberglass/epoxy on the outside. The net result was about a 1/4" recess on the lower left side of the airbox.

Since I had the airbox off anyway, I went ahead with Van's latest airbox bypass service notice (the one with the bowden cable rather than the magnet).

[robertahegy]

One thing you might try if the area is not too big. I used my hair dryer to heat up an area on my airbox that was too close to the nosegear leg. I heated it enough to soften the fiberglass, then I applied pressure with a pipe to reshape the affected area. You might be able to reform the edge of your airbox to add enough clearance. This way you could avoid a lot of reglassing.

Roberta