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Thread: Airplane weight loss ideas.

  1. #1
    Senior Member Esser's Avatar
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    Default Airplane weight loss ideas.

    Just curious to hear everyone’s ideas for making a super light Kitfox. I’m thinking some pretty dramatic things like:
    - only one set of controls/rudder pedals
    - carbon fibre sky light and turtle deck
    - Lexan doors

    I’m wondering how much savings carbon floor panels and would be and if I could ditch the center console if I made a flap bracket.
    ------------------
    Josh Esser
    Flying SS7
    Rotax 914iS
    AirMaster Prop

    Edmonton, AB, CWL3

  2. #2
    Super Moderator Av8r3400's Avatar
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    Default Re: Airplane weight loss ideas.

    Build a IV.


    Mic-drop.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
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  3. #3
    Rooster's Avatar
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    Default Re: Airplane weight loss ideas.

    Quote Originally Posted by Esser View Post
    Just curious to hear everyone’s ideas for making a super light Kitfox. I’m thinking some pretty dramatic things like:
    - only one set of controls/rudder pedals
    - carbon fibre sky light and turtle deck
    - Lexan doors

    I’m wondering how much savings carbon floor panels and would be and if I could ditch the center console if I made a flap bracket.
    Ditch the cabin heater! (3kg?)
    (I am from Africa).
    I also got on the bicycle and lost 10kg - Most effective action.

    What about just engine instruments and a Garmin G5?

    Reid
    Last edited by Rooster; 06-13-2019 at 12:18 AM. Reason: To Add

  4. #4
    Senior Member jmodguy's Avatar
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    Default Re: Airplane weight loss ideas.

    Make the cowl from epoxy resin and S2 glass, no gel coat. This is #1. Gel coat and polyester resin layups are heavy.
    Light weight hoses.
    Design wiring based on load not “bigger is better”


    Carbon fiber floorboards won’t be much, if any lighter. Just cost more.
    Jeff
    KF 5
    340KF

  5. #5
    Senior Member HighWing's Avatar
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    Default Re: Airplane weight loss ideas.

    Josh, been thinking about your airplane weight loss question. Sadly, my thinking - not much - given the evolution over the years.


    Example -1 One major difference IV to V. Behind the control stick assembly on the IV, the floorboards terminated just past the bungee bulkhead. Yes, in the three point ground attitude, I have had items slide down and onto the fabric below the seat. Solution, design the angled piece that covers the control stick assembly running from floorboard up to the front edge of the seat. This required a reshaping of the front lip of the seat pan eliminating the almost complete "U" that secured the front of the seat to the bulkhead below. Yes, I know of guys that flew many hours with nothing attaching the seat to the tube structure with no issues. With the fairly common incidents of the forward edge of the seat slipping off the bulkhead, the early fix was the straps running below the pan then the blocks between the pan and the structural tubing below. And yes, it was bothersome at times trying to find the washer that slipped and rolled back under the seat. Add the weight of the angled structure and accessories and the hardware (software) to keep the pan off the controls,


    Example -2 The typical IV came with no elevator trim. The Speedster came with a trim tab, electric servo controlled. Including ribs in both Horizontal and vertical surfaces for aerodynamics. At about an eleven foot arm this weight did have some effect on W/B, but manageable. Then going to the system that trimmed the horizontal stabilizer with the trim actuator plus the aerodynamic mods that closed gaps,added enough extra weight at the same eleven feet, that a new engine mount moving the engine forward an inch or two was developed. The ring mount is significantly heavier than the original mount. Going back to elevator trim would save some weight, but then the airplane would be significantly nose heavy, so sort of locked in W/B wise.


    Example -3 The IV came with tabs welded to the outboard rudder pedal that attached to cables that ran aft just under the outer fabric. At one end or the other - builders choice - parallel strips of steel drilled every half inch or so were placed so that they could be used to adjust the cable length, i.e. the rudder pedals. With the lever actuated adjustable rudder pedal assembly - added weight. Add to that the weight of the center console that mounts and hides all the stuff and it adds up.


    Example -4 Most Model IVs were covered with the 1.87 Oz uncertified fabric. an ounce lighter per yard vs. the 2.79 Oz, fabric standard today and - a guess here - likely about half as much polybrush to saturate the weave. Less weight. I know this would be a debatable choice in the minds of most, but the only thing I ever remember hearing regarding the two weights on a Model IV was from the guy whose ftrst IV weighed 604 lbs. empty. His comment was that he learned to like the mid weight cloth better because it resisted the cat scratch tears he would often find as the family pet liked to climb over his shed housed Kitfox at his farm strip.


    An aside from talking to the 604 lb. Kitfox guy. We often talked about picking up a Series 7 and then during the build eliminating all the things we never missed while each of use were putting the thousand (+) hours on our IVs.
    Lowell Fitt
    Goodyear, AZ


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  6. #6
    Administrator DesertFox4's Avatar
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    Default Re: Airplane weight loss ideas.

    Desertfox1 built his Vixen at 695 lbs. empty weight. So it can be done. She’s a hoot to fly.


    .5808D8B7-033C-4C78-94D9-5AD76BE6E384.jpg


    DesertFox4
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  7. #7

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    Default Re: Airplane weight loss ideas.

    How about replacing the stainless steel firewall with titaniun.
    Mike .

  8. #8
    Senior Member Esser's Avatar
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    Default Re: Airplane weight loss ideas.

    Thanks everyone for the ideas. Steve, I didn't know that Phil had a gear fairing on that plane too. I'm interesting in efficiencies as well including improved cooling with less drag. I see that Phil made the Lo Presti style cowl which should really help stop the air from going turbulent as it enters the cowl. I also have some idea to help it leave the cowl better as well.

    Building a IV is out as I have a 6 ready for cover.

    I was also going to remove all the adjustable rudder pedal options IF I add rudder horn length back to the original rudders which should be fairly easy.

    I do think the cowl will be CF in the end that is vacuum bagged. I will most likely be redesigning the over all cowl because I find the 7 cowl has a bunch of issues I don't like.

    Reid, I use the cabin heater almost every time I fly! at 10,000' on long trips it can get cold up there!
    ------------------
    Josh Esser
    Flying SS7
    Rotax 914iS
    AirMaster Prop

    Edmonton, AB, CWL3

  9. #9
    Administrator DesertFox4's Avatar
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    Default Re: Airplane weight loss ideas.

    Phil did fair the gear. Much carbon and model four controls, carbon seat pan also and turtle deck. No adjustable pedals and no brakes on right side. Much attention to weight savings during every phase of build. 500 rims and tires as it lives predominately on hard surface runways but is perfectly capable of grass or dirt strips. Heater and strobe/nav lights were added which bumped new empty weight to 711 lbs. but the heater is real nice even here in Arizona on a 50 degree winter day.


    DesertFox4
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  10. #10
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    Default Re: Airplane weight loss ideas.

    Yep, added heater lights and a couple comfort things. Worth the 13 pounds.
    Three pc Carbon cowls saved 8.5 pounds, carbon kevlar seat -5, carbon hexcell
    turtle deck and cargo floor -7, etc. looked at every pound as I was building. The
    biggest single weight saving was wheels, axles and tires. 18 pounds. Oh, she
    has Speedster wings, and 1 pound wingtips, Good fun!
    Phil Laker

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