Empty C of G SS7

[Esser]

Hello everyone. I am starting to contemplate W&B as I try to position things in the airplane. From what I understand with the Kitfox, everything you add to the plane basically puts the C of G aft. It would be very helpful if a few people could post their empty weight, prop and engine combo, tri or tailwheel, and the empty weight C of G.

Has anyone tried to get the C of G as far forward as possible with min fuel and one person on board? Does anyone have their aircraft at the forward limit?

The reason I am asking is Jiott had a thread where he was loaded to 1320# and already at 16". I am planning on using the full 1550# and I want to be limited as little as possible by being too far aft.

Let me know, I would be interested to see what the average ends up being.

[jiott]

My empty wt. (with oil, coolant, and unusable fuel+full header tank) = 834 lbs
912uls engine with Whirlwind 3-blade GA prop
Taildragger with Alaskan Bushwheel tailwheel (those babies are heavy)
Empty CG is at 13.40"
I have the lightweight Aerovoltz battery on the firewall.

All this puts my CG fairly far back. I have never got close to the forward CG limit with any combo of loading. The amount of baggage I can carry with full fuel seems to always be limited by the 1320 lbs with 16.0" CG. A lighter tailwheel and a heavier standard battery would help quite a bit I think. The W&B spreadsheet on the Kitfox website allows you to play around with lots of combinations.

[Dave S]

Esser,

With our trigear (which is heavier than most @884#) the closest I can get to the forward GC is with zero fuel, zero baggage, no passengers no pilot, empty header tank, empty toolboxes etc.....CG ends up at 10.37".....in otherwords it's impossible to load to exceed the most forward limit without hanging lead bars on the prop for our aircraft. Noteworthy that one of my odyssey batteries is behind the pilot's seat.

On the other hand......it is entirely possible to exceed the aft limit with careless loading. I have an extended baggage bay with the baggage area divided into 3 loading zones/stations.....the only thing that goes in the far back is the sleeping bags.

Ditto on the KF spreadsheet...although a person can easily make up their own W/B spreadsheet with excel if you have any W/B stations that vary from stock.

Sincerely,

Dave S

[phintz]

perfect timing of this question, my FAA checkride dude made me figure both empty and max cg of my series 6. Empty weight of 750 lbs with oil and unusable fuel was 11.19 , Max loaded with full fuel , 2- 200 lb people I was 15.16 in. . If you would like I have a printed spread sheet of this also!

Patick -series 6
tri gear , rotax 100 hp

[JohnB]

My SS7 taildragger, Rotax 912ULS, Whirlwind 3 blade, came in at 808 lbs. and an empty CG of 11.2". A little porkier than I has hoping, but I also have the heavier Desser 21x8 tires and installed the extended baggage compartment (at least that's my excuse and I'm sticking to it.) As others have said, I have found it is impossible to get to the forward CG limit but fairly easy to exceed the aft limit when you start loading baggage.

[Esser]

Wow, this is really eye opening. I realize the SS7 was designed for heavy engines but using the Kitfox W&B example in the build manual. An 814# empty SS7 would have to have an empty C of G of 7.48" to get a 9.5" C of G with a 170# pilot and 3 gallons of fuel.

Is this even possible without adding ballast?

I am interest to see John Kuzmic's as he has a 914 and an airmaster prop. All heavier than a ULS and a ground adjustable. Plus he has a nose wheel. Not sure how much of a difference that makes since the tail wheel has such a long arm.

[Esser]

Doing a quick and dirty calculation, is your plane was 801# empty, you would need 45 lbs on your tailwheel and 378 on each main to get an empty C of G of 7.49

[Esser]

Sorry to beat this thread to death but here is a sample W&B I did with my theoretical plane. Now to see if it's doable.

I went a little over on the baggage area to push it.

[Esser]

Bringing this thread back to life as currently my empty weight C of G is 5.49...

Considering everyone said this was impossible and I didn't try to load weight into the front I'm slightly amazed and annoyed lol. As it stands right now, to get me to 9.00 inches with me in the seat I need 40lbs of fuel and 38 lbs in the cargo bay.

I'm thoroughly confused. I know the Airmaster is a heavier prop and the prop extension that came with it is heavy too. But looking what everyone else has said, I'm scratching my head. I will double check my measurements tomorrow but as she sits now, I'm 418 on each main and 42 on the tail....

[jrevens]

If your weights are accurate, it sounds like you are very nose heavy, Josh.


I have the Whirlwind 72" 3 blade GA, 912 ULS, Desser 22' 8.50 tires, T3 tail spring, lightweight Matco dual fork 8" tail wheel, Heavy "standard" battery, a relatively heavy panel with steam gauges, extended baggage with aluminum floor panels, single axis auto pilot, and a few other "extras" (like a ground-handling handle on both sides), etc. And Oratex of course.


Empty weight is 819# with header tank fuel, all engine and brake fluids, & fire extinguisher.


Empty CG is at 9.843". So, like so many others, it's impossible for me to even get close to the forward limit with someone in the airplane. My empty tail weight is 59#.


As an example, with 2 180# people, full fuel, and 130# in the cargo bay my CG would be at 15.9". I haven't flown it loaded to give that CG condition yet, so I don't know how it will handle there, but the probable weight carrying ability is pretty impressive to me. In that regard, for those of you flying, how do these airplanes (SS 7) fly/feel when close to the aft limit?