Effect on CG

[Zero4Zulu]

I'm working on rebuilding a RV6A. The engine is a O320 B3B (Conical Mnt.) I have changed the sump to the more forward carb. location from the far aft type sump. The builder had 3/8" spacers behind the engine mounts to make room for the FAB and nose gear interference with the previous sump.

This plane has a Hartzell constant speed prop. I'm also replacing the spinner and bulkheads to fix a poor job there also.

Between these two issues, it means I'll need to move the cowlings aft at least 3/8". I am redoing the cowl attachments anyway so I don't mind that.

Question is..............how much will moving the engine back 3/8" effect the CG and is this a good thing since it is a constant speed prop with more weight up front?

[L.Adamson]

Since you'd be back to original design, I see no problem there. I have a 6A with an 0360 & Hartzell prop. I installed the strob pack & elt towards the tail to help offset the weight, even though they aren't exactly heavy. In the end, just re-weigh & make new calculations---- especially for baggage capacity, which will be the most important. You can download the W/B charts from Van's website.

L.Adamson --- RV6A

[Kevin Horton]

Originally Posted by Zero4Zulu

I'm working on rebuilding a RV6A. The engine is a O320 B3B (Conical Mnt.) I have changed the sump to the more forward carb. location from the far aft type sump. The builder had 3/8" spacers behind the engine mounts to make room for the FAB and nose gear interference with the previous sump.

This plane has a Hartzell constant speed prop. I'm also replacing the spinner and bulkheads to fix a poor job there also.

Between these two issues, it means I'll need to move the cowlings aft at least 3/8". I am redoing the cowl attachments anyway so I don't mind that.

Question is..............how much will moving the engine back 3/8" effect the CG and is this a good thing since it is a constant speed prop with more weight up front?

The change in empty CG location will be:

(distance the weight is moved) x (amount of weight moved) / (empty weight)

E.g., if you figure that engine, prop, etc weigh 400 lb, and your empty weight is 1000 lb, then moving the engine back 3/8" will move the aircraft's CG back 3/8 x 400 / 1000 = 0.15"