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Old 02-20-2011, 09:24 AM   #1
rogerh12
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Default Kitfox-4 elevator trim systems, rans wheel or electric ???

HOWDY ALL;

Well I am confused on installing a trim system for the model 4, and hoped to get some insight from the group. My old model 2, to trim for pitch you just moved the flapperion handle a little (actually, it was not good for much else, didnít really seem to work well as a flap). However, I understand the model 4 flapperions work more like real flaps, and thus adding pitch trip is necessary, correct? (or do I just move the flapperion handle again?).

Kitfox offer an electric trim system, but I see they want you to buy a special elevator that accepts it. But I hear the Rans trim wheel system might also work (sold my aircraft spruce). Has anyone used the Rans? Will it work with the standard kit elevator, or is the trim tab model needed?

Look forward to your responses!!!!!

Roger
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Old 02-20-2011, 12:12 PM   #2
Av8r3400
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Default Re: Kitfox-4 elevator trim systems, rans wheel or electric ???

I have a flying model IV. It does not have a trim system on the elevator. Trimming is (supposedly) done with the infinitely adjustable flapperons.

There are several reasons why I don't like this.

  1. You can not trim the plane to fly hands off while on approach. At low power settings the nose is very heavy. (Not to mention eliminating the use of the "flap" feature - which is effective)
  2. Cruise trim is just barely maintained. I have the fixed horizontal stab set to max nose up position and with full reflex on the flaps, it will just maintain level flight
  3. Safety factor. Without a trim tab, if the linkage ever fails, this means game over. I've tried some approaches using power and flapperon "trim" and found that it can't be done. During my private training we constantly practiced landings with one of the three axis of control failed.
On my 1200 rebuild, I will be modifying the elevator to accept a trim tab. Maybe electric, maybe cable operated. I have seriously contemplated adding the Rans tab you referred to on my 1050 flying plane for the above reasons...
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Old 02-20-2011, 04:40 PM   #3
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Default Re: Kitfox-4 elevator trim systems, rans wheel or electric ???

If I were building I would go with an electric tab. Lowell at Highwing LLC will mod your elevator for you.
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Old 02-20-2011, 05:32 PM   #4
rogerh12
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Default Re: Kitfox-4 elevator trim systems, rans wheel or electric ???

Steve;

Thanks for the info !!!

FYI on the Rans wheel trim. Rans released a scary notice saying that it has led to elevator flutter, due to the usage of a spring in the trim system.
They have recommended going to an electronic servo type trim system, with a ridged pushrod arm, or a mechanical system one with a ridged push rod or tube.

Roger
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Old 02-21-2011, 06:57 AM   #5
catz631
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Default Re: Kitfox-4 elevator trim systems, rans wheel or electric ???

Roger,
I sent my 4 elevator off to Lowell at Highwing LLC and had him install the elevator trim. I installed the trim button in my stick and I now have a terrific system !!! No more "mickey mouse' flap trim. Its really great to trim the pressure off on approach as well as level flight. This is the only way to go !!
Dick
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Old 02-21-2011, 12:17 PM   #6
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Default Re: Kitfox-4 elevator trim systems, rans wheel or electric ???

WRT to Rans Trim Wheel, I'm installing one of those. There is no spring in the system. It uses a solid wire push/pull system. Eric Ashman has one on his IV and it works great.

If you mean this:
http://www.rans.com/_KITS/PDFs/AD127.pdf
It refers to an older trim system.

What *is* a concern on these push/pull systems is to make sure the wire and sheath are secure.
http://www.ntsb.gov/ntsb/GenPDF.asp?...98LA170&rpt=fa

What I've use on these cables is safety wire on the outside as well as Loctite "Black Max" 380 adhesive. This will bond the sheath to the wire as well as to the metal locking ferrule.

Just me, I like the mechanical trim more than an electric servo.

Cheers,

Mark Napier
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Old 02-21-2011, 01:01 PM   #7
Av8r3400
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Default Re: Kitfox-4 elevator trim systems, rans wheel or electric ???

Here's the RANS trim system from Spruce.

What I like about this is the tab can be attached to the rear of the elevator not needing covering repair or cutting / welding. Plus the wheel is a nice infinite adjustment.
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Old 02-21-2011, 02:21 PM   #8
rogerh12
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Default Re: Kitfox-4 elevator trim systems, rans wheel or electric ???

Thanks for the info guys;

Looks like I saw the faulty trim system notice Rans put out on the old trim system, and agree it does not include the current system offered by aircraft spruce.

Regarding the crash after a trim system failed; from a guy that flew a plane and landed safely after his propeller broke off,,, losing power and panicking does not have to equal stall and crash, (neither does a stuck trim tab), if you remember to fly the plane while your panicking. I know you don't want too, because thatís where the ground is, but keep the nose down during all maneuvers, and you won't stall the plane. A controlled crash is 10x better than stall and crash.

Roger
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Old 02-21-2011, 03:07 PM   #9
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Default Re: Kitfox-4 elevator trim systems, rans wheel or electric ???

The trim tab brackets don't require welding, but some hammering over a steel rod and cursing are in order. The radius of the Rans aluminum tubs is much larger than the steel tube trailing edge of the Kitfox. Also, I still need to make an appropriate spacer to put the cable retainer at the right height to lay right on the fabric. I know it is on the bottom but I still want it to look good.

About that NTSB report, there is a local guy who had a departure stall in a Kitfox Lite and dropped in about 50 feet. He broke his shin bone badly. The medication that the paramedics gave him for pain blocks the formation of short term memory. So just like the guy in the NTSB report, he couldn't remember the details of the take off and stall or much else that went on that day. So I can't 2nd guess what happened that caused the stall with the bad trim system but I can make darn sure that my trim system is right. If the force required to keep that stick forward was too great I would also be tempted to slow the plane down to keep from breaking something in the control linkage.

There is another report in the NTSB where the stick in a Kitfox IV wouldn't go to the left of center. The guy got it down with rudder but lost it on roll out. He was unhurt but trashed the plane. They didn't say but I would bet real money that the little bell crank under the seat was catching on the floorboard/carpet. Mine is going to have a hard steel ramp right there on the floorboard and a stout screw (maybe safety wired) holding onto that floorboard/fuselage attachment bracket just under the bell crank.

FWIW,

Mark
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Old 02-23-2011, 03:38 PM   #10
rogerh12
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Default Re: Kitfox-4 elevator trim systems, rans wheel or electric ???

Howdy all;
Does anyone have pictures of the RANs elevator trim tab installed?
If so, would you email them to me at hills@sunflower.com?

Thanks
Roger
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