weight and balance for a 2200 sonex

[sonexoldman]

I am planning to rebuild my 2200 Jabiru engine mount to push the motor farther out. I have done the c of g calculations and the motor needs to be 7.5 inches farther forward. Presently my c of g is at 67 inches. The limits are 63.8 to 73.2 inches from the spinner or 20 to 32 % MAC. I have been flying it now for 13 yrs like this with the c of g 3.2 inches from the forward line.
I am going to Alaska in August this year and am going to ballast it to get a much better c of g. I will put 25 to 30 pounds of lead on the motor and into the cowl to balance the plane better. I have a spare motor mount for a 2200 Jab and will post pics as I modify the mount

[tonyr]

30 pounds of lead in front or engine 7.5" further forward?, that sounds excessive even for a 2200 Sonex!

You don't mention what condition you have to achieve your current CG at 67"

Looking at my figures, I am at 67.6" with full fuel and 2 passengers, (no baggage allowed in rear bay, just a zip lock bag on passengers lap for smalls)

Solo trips away I load the passenger floor, passenger seat and then maybe minimal stuff in the luggage bay.

During construction I purposely kept as much weight as I could ahead of the main spar, I wasn't economical in the use of adel clamps, fasteners, fittings etc in and around the engine bay, no paint to the rear apart from the tail tips. No fancy baggage compartment or plastic tubs etc. behind the seat.

Is there anything rear of the spar you can relocate forward to redistribute your weight?

As mentioned my aircraft with 2 passengers full fuel CG sits at 67.6"

(Sorry about the spacing - looked fine in edit!)
Max weight recommended 1100 lbs for 85HP

Max Gross Weight (lbs) Condition:
Item: -- Weight: -- Arm: -- Moment:
Empty Aircraft 641 -- 65.75288612 -- 42147.6
Fuel 96 -- 45.75 -- 4392
Baggage 0 -- 102 -- 0
Pilot 185 -- 76.9 -- 14226.5
Passenger 178 -- 76.9 -- 13688.2
1100 -- 67.68572727 -- 74454.3
CG=(Arm-53)/54 CG= 0.271957912 27.20%

With same 2 passengers - empty fuel 69.5"

1013 -- 69.56964462 -- 70474.05
CG=(Arm-53)/54 CG= 0.306845271 30.68%

Still within limits. I have flown with same passenger weights down to 3-4 US gallons of fuel, handling was pretty much same with a bit more forward trim required, stalls were fine. (passenger was a few sandbags and didn't complain)

Cheers
Tony

[tonyr]

Another thing I was curious about, what prop are you using on your 2200 and what rpm are you cruising at?

What is your cruising speed as well?


Cheers
Tony

[DCASonex]

Putting a 3300 out front would also solve that problem and provide enough power to haul whatever you need on that trip. :-)

David A.

[tonyr]

..yeah. I wish lol

[sonex892.]

I'm really surprised this hasn't been done yet. Using Sonexoldmans 7.5" I did 3 profile sketches to see what the sonex might look like with a longer nose.
Having built a Sonerai with a 2200 Jabiru. I moved the engine forward for all the same C of G reasons. I found out moving engines forward can also drastically change the look of an aircraft. The long nose Sonex doesn't appear look that different compared to the original as my Sonerai did.
Top : Standard Sonex
Middle: modify cowl and engine mount only
Bottom: Raise windscreen/canopy bow approx 18mm, raise upper firewall approx 35mm, modify cowl and engine mount.

[Corby202]

The limits are 63.8 to 73.2 inches from the spinner
Not sure that is correct. 63"=20% 70.2"=32%
25-30 lb of ballast at the engine is only bringing the forward weight up to that of a VW so should be fine.
Other then painting all the plane I did everything I could to get the weight forward, extending the cowl 50mm, push the prop & spinner forward 50mm and the battery is about as far forward as I can get it.
C of G on mine is 22% just me and full fuel. 31.8% with me, 80kg passenger, 15kg baggage no fuel.

[tonyr]

The limits are 63.8 to 73.2 inches from the spinner -

EDIT - Phil is correct, I rechecked my spreadsheet and I have 70.3 inches as the rearward limit. Dyslexia :(

So 73.2 is indeed NOT correct - assuming that your datum (spinner point) is 53" ahead of the leading edge as per the flight manual.

My spinner was actually 52.5" ahead of the leading edge so I measured everything from a datum .5" ahead of the spinner
That way I figured I'd keep the numbers consistent with the manual for the moment arms for pilots, fuel, baggage.

PS Why add excess weight just to be like a VW driver??