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Thread: Joe Ruscito's Kitfox S7 Build

  1. #291
    Senior Member JoeRuscito's Avatar
    Join Date
    Jun 2018
    Charleston, SC

    Default Re: Joe Ruscito's Kitfox S7 Build

    Did my weight and balance today. I used heavy duty bathroom scales and it went fairly well, they were all within 1 lbs of each other when I calibrated them. I weighed twice and took the average (they were each off ~+/- 1 lb between tests). My total weight is 836.4 lbs and GC is at 10.4. Once I get up and flying I plan to get it reweighed on some real aviation scales but there are not any I have access to close by. The trickiest part for me was accurately marking the tail wheel position on the floor when it was up on a stand so a plumb bob couldn't be used.

    Right Wheel Left Wheel Tail
    Weight #1 385 386.6 65.6 837.2
    Weight #2 384.4 385 66.2 835.6
    Average 384.7 385.8 65.9 836.4

    ARM -1.6875 -1.96875 154.0625

    I also ran some trail weight and balances for the first time, my take aways were:

    -adding or subtracting fuel has very minimal effect on cg. Min 30 min fuel at 7.26 gallons per hour (Rotax 912is) or max fuel only moves the CG a fraction of an inch.
    -even adding passengers has minimal effect
    -cargo has of course the largest effect
    -with full fuel and two 190 lbs passengers and 150 lbs of baggage I am still 25 lbs under 1550 but my cg is behind 16 (@16.62) which means I will only be able to carry 120 lbs cargo in that configuration. And considering subtracting fuel has little effect that seems to be my max cargo weight. Does this make sense?

    Excuse my novice understanding, but it seems the stol guys are always trying to get the CG farther back. This doesn't seem very difficult so why is it such a topic of concern. What does seem difficult is to get an empty CG forward enough to be able to utilize the full cargo capacity.

    Now that I know I'm likely to always be under 1550 Im considering springing for the Airmaster, which would put a bunch of weight on the nose so that my cg moves forward. Thoughts?

  2. #292
    Senior Member aviator79's Avatar
    Join Date
    Dec 2016
    Los Alamos, NM

    Default Re: Joe Ruscito's Kitfox S7 Build

    Good weight and CG Joe!

    The Airmaster will move your CG forward. I have a 914 and Airmaster. My empty weight is 875, and empty CG is 9.7. I can carry full fuel, two grown men, and 150 lbs in the baggage area without exceeding max gross or the aft limit. The downside is that when I'm light and by myself (CG 11.8), it's nose-heavy. I can't trim it hands-off at approach speed despite adjusting the trim actuator rod end to its aft limit. I compensate by throwing 25 lbs in the baggage area (CG 12.7), which gets it *almost* hands off at approach speed. 50 lbs in the baggage area (CG 13.5) makes it even better, but 25 is a good compromise. You do sacrifice some performance adding baggage ballast to dial in your CG.

    In my opinion, if you can afford the Airmaster, you should do it. It might give you some more utility with your CG, but that's secondary to getting all the performance out of your engine.

    One other thing: On my W&B, I divided the baggage area into three stations (fore, mid, and aft). If you put the heavy stuff in the front of your baggage area, and the lighter stuff in back, it can help you stay forward of the limit.
    Last edited by aviator79; 10-14-2019 at 06:16 AM.
    Flying - S7SS

  3. #293
    Senior Member jiott's Avatar
    Join Date
    Jun 2010
    Portland, OR

    Default Re: Joe Ruscito's Kitfox S7 Build

    Yes, managing the weight distribution in the cargo area helps a lot. I keep my tool kit, tiedowns, etc. crammed right behind the seat and put the lightest stuff in the rear of the cargo area. I like the idea of braking the cargo area into 3 zones to more accurately calculate W&B.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

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