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Thread: Heavy Elevator, maybe install a spring ????

  1. #11
    Senior Member Dave S's Avatar
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    Default Re: Heavy Elevator, maybe install a spring ????

    Roger,

    John has the issue covered well on the issue of the slipstream taking the pressure off the stick. 100% spot on. Elevators work pretty much like a wind sock.....they droop unless they have wind....

    I would like to add a bit about the Spring assist kit which John Mc Bean provides.

    I also have a series 7 - same deal as War eagle - and I got the spring assist and installed it following phase 1 testing. Works well and is a good enhancement for the plane.

    My theory was fly it as designed - then consider enhancements only after getting acquainted with the handling characteristics to see if it is really needed and if it is even appropriate - and maybe a little of - I want to know how this things works first.

    Kitfox models, while they have a lot in common - do have their individual uniquenesses; however, heavy controls in flight is not one of them - I love the light touch on the controls and freedom from mechanical drag and freedom from control slop so you can feel the air load rather than drag from assorted cables and pulleys.

    The elevator is going to feel heavy when the plane is sitting in the hangar - mostly all airplanes are like that. That is not what the spring assist is for. What the spring deal is all about is providing TRIM ASSIST, not lightening the elevator feel when the plane is in the hangar.

    I wouldn't make any assumptions that if it's good for a series 7 it is good for other models.

    The way my KF 7 flew with flaps out at approach speed and full nose up trim required some backpressure to hold the attitude - in otherwords you could not completely trim out all of the backpressure.

    The Trim Assist that John M sells is specifically designed to help trim out the backpressure (which is not in any way very much pressure in the firstplace) so you can arrive at a neutral stick pressure on approach WITH THIS PARTICULAR MODEL of kitfox.

    It is not for alleviating the static elevator weight - it is for assisting the nose up trim on approach.

    If a person makes design changes in controls before testing - the alteration/modification can mask basic handling characteristics and you can end up with something akin to the goofy obsessions we have in this country with medications - take a pill to fix everything - take a second pill to fix the side effects of the first, then a third to fix the side effects of the second ...till a person has a home pharmacy of 37 pills to fix one basic issue and the constellation of pills are worse than the original problem.

    I haven't flown every kitfox model out there - a IV, a couple 5s and & a couple 7s and they all handle well easily enough as designed. Wouldn't be too concerned about modifications till some flight testing is done. There will likely be some fine tuning of the rigging after the first flight or two anyway.

    Sincerely,
    Dave S
    KF7 Trigear
    912ULS - Warp drive
    W/Trim assist

  2. #12
    Senior Member SkyPirate's Avatar
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    Default Re: Heavy Elevator, maybe install a spring ????

    well put Dave and I agree totally,.build it to spec then after acumilating time in it, do a mod if it needs it ,..or if you want to try one ,..unless there is time on the aircraft or the pilot in type prior to flying the build ,..there is no "zero" ground to start from,..if the pilot has time in type and says OK,.I want my build to fly just like so n so's,..providing everything in his build is the same as the one he flew prior,.( same numbers WB,..same engine,..prop..etc) then I would consider it during the build prior to flying it.
    Even though there is another fox flying a VW conversion from prior posts, and probably more kitfox's flying with VW conversions ,..as noted in prior posts ,there isnt much info on it ,..so that alone is one mod that I would want to work out before I applied another mod to the same plane.
    I think I know what your thinking though Roger ,..the VW being heavier your wanting to apply some back pressure mechanically instead of balancing the plane? I'd opt to balance the plane,..
    Last edited by SkyPirate; 09-18-2011 at 11:46 AM.

  3. #13
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    Default Re: Heavy Elevator, maybe install a spring ????

    Skypirate:
    The plane is being built with serviceability in mind, after having issues with some older planes and finding out parts of the plane can’t be accessed for maintained or even inspections without cutting cloth or drilling out some rivets (my floor boards are now made of metal and segmented to be removable in the future, if needed). Adding a spring to the horizontal elevator later, if needed, should be no problem as I will have good access in the tail cone with extra inspection plates (or behind/ under the seat).

    I also have removable counterweights mounted in the tail. I had special mountings welded in as far back as I could get it in the tail cone for the lead weights (also, if needed), so I should be able to compensate for the heavier VW engine, one way or another (horizontal stabilizer rigging, electric trim tab, counter weights or elevator spring,,, or maybe a little of all 4 !!!!! ). The custom VW engine mount should compensate for the heavier VW engine, however, I just don’t want to build myself into a corner, so to speak. Anyway, the extra time it takes to improve the plane is kinda fun, so why not do it.
    Also, regarding a previous posting about reducing the risk of a stall & spin on my plane, I am installing mountings in the fuse tail cone for a lower shark fin that can be installed and removed as well (located on the far aft fuse) which should increase directional stability and also provide surface area below the horizontal stabilizer to help counter spin rotation. Being removable, I can make several sizes and try them out (start small, and work my way up I guess). This is not done on Kitfox's as they are tail draggers and would quicky bend anything hanging down in that area, but I can do this as my plane is already a nose gear model 4 and I don’t have to worry too much about bending the thing as my tail skid should not touch the ground anyway (I hope) and will help to protect the fin if it does.
    Roger

  4. #14
    Senior Member SkyPirate's Avatar
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    Default Re: Heavy Elevator, maybe install a spring ????

    Roger,..dont "over" build it,
    have you done any preliminary weight calculations to figure out how much your plane will weigh when it's done? all the little add ons add up.
    I'll stick to you aught to do one Mod at a time,. starting with the motor,...if there is a problem ,..and you've done all of these mods ,..prior to it's first flight,..you wont know where to begin to correct any "bad habits" the plane might have.

  5. #15
    Senior Member SkySteve's Avatar
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    Default Re: Heavy Elevator, maybe install a spring ????

    Roger,
    Here may be an option. I have been considering adding it to my plane for cruise trim.
    http://www.aeroconversions.com/products/trim/
    Last edited by SkySteve; 09-23-2011 at 04:18 PM.
    Steve Wilson
    Huntsville, UT
    Kitfox 85DD
    912A / 3 Blade Taper Tip Warp Drive
    Convertible Nosewheel & Tailwheel
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  6. #16
    Senior Member Slyfox's Avatar
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    Default Re: Heavy Elevator, maybe install a spring ????

    when I first bought my airplane it had the standard elevator. Yes more pressure needed for landing. When flaps were on it was harder to pull back for flair to land. I redid my rear elevator and put in the electric trim. Now me be spoiled absolutely love it, like power steering.

  7. #17
    Senior Member Slyfox's Avatar
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    Default Re: Heavy Elevator, maybe install a spring ????

    Now, also I want to point out that having the stick fall down when on the ground means nothing. once the air goes over the elevator it will come up on it's own. If this is what your concerned about, don't. It will act as normall as any other elevator in an airplane. Yup you have different airspeeds that will affect the stick pressure. best to put in electric trim and be happy afterward. I am. In fact if your kit is around mine, mid 90's than the best thing you can do is cut that stupid stop in the back of the tail and put a stop on the floor to copilot stick. What this does is allow the stick to flop full forward. Now you can get in and out with the greatest of ease. After I did this to mine it was like what stick when I got in and out. I'm a small guy and can't emagine a bigger guy trying to get in without this mod. I flown my fox over 1000hrs with it like this.

  8. #18
    Senior Member Slyfox's Avatar
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    Default Re: Heavy Elevator, maybe install a spring ????

    also want to point out that there is or was a kit to install the trim in the elevator, a little cutting and welding, an electric motor and all was done.

  9. #19
    Senior Member dholly's Avatar
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    Default Re: Heavy Elevator, maybe install a spring ????

    Quote Originally Posted by Slyfox View Post
    In fact if your kit is around mine, mid 90's than the best thing you can do is cut that stupid stop in the back of the tail and put a stop on the floor to copilot stick.
    Ok I'll bite, got pics?
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  10. #20

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    Default Re: Heavy Elevator, maybe install a spring ????

    Quote Originally Posted by rogerh12 View Post
    Skypirate:
    Also, regarding a previous posting about reducing the risk of a stall & spin on my plane, I am installing mountings in the fuse tail cone for a lower shark fin that can be installed and removed as well (located on the far aft fuse) which should increase directional stability and also provide surface area below the horizontal stabilizer to help counter spin rotation. Being removable, I can make several sizes and try them out (start small, and work my way up I guess).
    Have you thought about why no major manufacturer installs these fins? Are you assuming that with over a hundred years of development no aircraft designer has thought of it? I would suggest that there are compelling reasons why you don't see these on aircraft. You would do well to investigate this before spending the time, money, and perhaps exposing yourself to physical risk.

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