Engine rubbing lower cowl

[bogopper]

Hi

I have an RV6 with an IO-360 angle valve, Clarck Lyddick wood prop and 850 hours after 12 years. Over winter I've had it stripped and repainted.
Today my inspector came to make sure I had put everything back together correctly. During the inspection he found that the engine/exhaust had been rubbing on the lower cowl. I should have noticed sooner but was more interested in the sodding flap hinges.

I think the engine has sagged because I have found the rubbing getting slightly worse as I have done the serviced. I've used aluminium tape to protect the area but had not got round to that this time before he came.

My inspector now wants me to cut the cowl and fit a bulge. I don't really want to do this because of the fresh paint and the resultant unsightly bulge.

I also don't want to find myself in flames!

Suggestions anyone?

Mark Turner

[scsmith]

If you think it is just from engine sag, no harm in putting some large washers under your engine mounts. A pair of 1/16" washers will raise the prop flange about an 1/8" IIRC.

Depending on where your rub is, this may only get you a 1/16" to 1/8" increase in clearance. So if it is just rubbing a bit on start-up or shut-down, maybe that's enough change to make a difference. If the rub is worse than that, you should probably take more drastic measures. I try to maintain 1/2" of static clearance on everything in there, although the bottom of my ram-air/alt-filtered air housing is probably about 3/8" from the cowl.


What part of the engine is rubbing? What can be modified to improve clearance? If its the air box or snorkle, it can probably be modified to save your cowl paint.

But perhaps a better suggestion: The cowl is a honeycomb sandwich. You could gain about 3/16"-1/4" clearance by carving out the inside glass ply and honeycomb locally around the rubbing area, then glass in a patch of glass on the inside to seal it up. This is easy to do, will save your paint, and gets some needed clearance.