CG: Adding Ballast to Tail

[lrobichaux]

Does anyone have experience in adding ballast to the tail of an EX/FX-3 to shift the CG back with as little weight as possible? Majority of my flying is solo and I've been maintaining a favorable CG by adding quite a bit of weight on the rear cargo area. Looking to achieve the same result with less weight. Tailwheel is Acme Stinger + baby bush wheel. Would prefer an option where it's not terribly difficult to remove the tail ballast as needed for the specific mission. TIA! (pic for attention).

 

[Cactus Charlie]

I used to fly a couple of PA-18-180 that were Restricted category glider tugs. Both had lead blocks attached using the tail spring bolts.

The CG of my FX-3 is perfect with just the essential drinking water, tool bag, and tie downs at the aft end of the baggage compartment so I have not explored adding tail ballast.

"Perfect CG" - My trim is zero for cruise and for approach and landing with only very small adjustment required. The only time it is significantly away from the zero trim drag configuration is for takeoff with flaps. For takeoff I set about 1/3 nose down. This makes it easy to raise the tail and I'm in trim for the full power flaps 1 climb out. Trim goes back to zero after flap retract.

My trim scale is custom with a takeoff green band present only on the ground.

 

[Neal]

I have BRS and I also have 15lbs of other stuff in a rear tacnet and I really like the CG this way. When I did my DAR interview at final build Stan suggested adding weight back there, around 30 lbs. I told him I had the BRS and he said good...that will do it.

 

[lrobichaux]

I've been keeping about 35 - 40 lbs. of tools / parts / gear in the rear baggage compartment, which seems to situate the CG very well. My question is whether this rearward shifting of the CG could be accomplished with much less added weight with lead bolted to the tailwheel. But I suppose I wouldn't be saving that much weight and wouldn't impact short-field operations that much at all.

 

[Neal]

You could. Some do that in STOL competitions like Eric Massey in his FX-3.

 

[Cactus Charlie]

But I suppose I wouldn't be saving that much weight and wouldn't impact short-field operations that much at all.

Some numbers for my FX-3. These assume minimum fuel -

Aft baggage 43 lb gives CG 73.8 inch
Aft baggage 0 lb gives CG 72.0 inch
Tail ballast 14.5 lb at 250 inch gives CG 73.8 inch

So, with all other loading the same, removal of 43 lb from aft baggage requires 14.5 lb on the tail spring bolts to restore the CG.

Weight saving is 28.5 lb but I do not know if it is practical to add 14.5 lb to the tail spring anchor.

 

[Neal]

One thing to be aware of with attaching anything external - it can fall off and kill someone. Weigh the benefits, anything you attach externally should be done with care and per my DAR needs to be logged in the airframe logbook as flight tested.