Engine Sag

[wolfrv6]

I am installing my cowling and have heard that the prop will sag after a few hours. I am trying to figure out how much lower I need to set cowling Thanks Rolland RV6

[rv8bldr]

Hi Roland,

I have an IO-360-A3B6D (i.e. heavy) and I set my cowl about 3/16" low, and after about 40 hours it appears to be perfectly aligned (no acro, though). That being said, I didn't even notice that the cowl was set low for the first bunch of hours so how much (or even if) you set it low may be debatable.

Cheers

[dan]

On my RV-7 with an IO-360-A1B6 (angle valve porker) and 2-blade Hartzell, it has sagged about 3/16" in a little under 500 hours. It actually sagged down and slightly to the right, not directly down. And the sag occurred in the first 250 hours or so then stabilized.

I do fly acro, all positive G stuff, and pull 3+G regularly.

Just a data point for the file.

)_( Dan
RV-7 N714D
http://www.rvproject.com

[Bob Axsom]

The Cowl flat disc surface area on my RV-6A is larger Diameter than the spinner so when I installed it I aligned the top of the spinner with the top of the cowl mating disc. It has held alignment well but I did retorq the engine mounting bolts after about 50 hours. I used the aircraft standard 60 Amp alternator with the standard pulley and I have good clearance between it and the cowl. However, I noticed a slight scar in the inner surface of the cowl from a contact with the alternator pulley. I have read of builders using alternators with larger pulleys cutting through the cowl and requiring the addition of a clearance blister. I added a thin strip of stainless steel over the scar with structural adhesive. It has been marked but not penetrated yet. In other words this is another reason to keep the engine at the high end of the alignment tolerance.

Bob Axsom

[N834ST]

I too am about to embark on this part of the project. So far everyone I've spoken too or heard about has done about a 1/4".