[N45D]

How can I estimate a new CG for a different prop weight?

 

[longranger]

Step 1 Calculate Current Aircraft Empty Moment:
Current Aircraft Empty Weight * Current empty CG

Step 2 Calculate Current prop moment:
Current Prop Weight * Prop Station Measurement

Step 3 Calculate New Prop Moment:
New Prop Weight * Prop Station Measurement

Step 4 Calculate New Aircraft Empty Weight:
Current Aircraft Empty Weight - Current Prop Weight + New Prop Weight

Step 5 Calculate New Aircraft Empty Moment:
Current Aircraft Empty Moment (from step1) - Current Prop Moment (from step 2) + New Prop Moment (from step 3)

Step 6 Calculate New Aircraft Empty CG:
New Aircraft Empty Moment (from step 5) divided by New Aircraft Empty Weight (from step 4)

 

[N45D]

Step 1 Calculate Current Aircraft Empty Moment:
Current Aircraft Empty Weight * Current empty CG

Step 2 Calculate Current prop moment:
Current Prop Weight * Prop Station Measurement

Step 3 Calculate New Prop Moment:
New Prop Weight * Prop Station Measurement

Step 4 Calculate New Aircraft Empty Weight:
Current Aircraft Empty Weight - Current Prop Weight + New Prop Weight

Step 5 Calculate New Aircraft Empty Moment:
Current Aircraft Empty Moment (from step1) - Current Prop Moment (from step 2) + New Prop Moment (from step 3)

Step 6 Calculate New Aircraft Empty CG:
New Aircraft Empty Moment (from step 5) divided by New Aircraft Empty Weight (from step 4)

Longranger, thanks for the formula. Now I need to know the prop station measurement. I Just started my build and I wanted to use W&B data from similar setups so I could estimate changes in others W&B based on different prop solutions.

I want to build my 8 light. I'm 6'5" 220lbs working towards 205. At 6'5" my pilot weight is going to contribute to the useful load in an unuseful manner. At 220lbs i will be limited to a 180lb back seater with full fuel (220+180 + 42 gallons at 6.5lbs ) An empty weight of 1127 plus all that is gross weight. I'm trying to plan my build from others data and hopefully manipulate that into an approximation of where my build will end up. I see a composite prop and grove landing gear in my future.

Thanks
Dave