N94JE

[Mendlerr 4]

Some Exterior Pics

 

 

Yes I know the turtle deck is not installed properly.  I just set it on there for the pic.

[Mendlerr 4]

Just a few more to close for the night.

 

[akflyer 1427]

interesting considering the published cg is 10.7-16".  I'll have to play around.

 

Where do you live and how do I get there?  Sounds like a party!  Steak, Seagrams and 7up, haha!

 

That is the same published CG range for the avids... it is VERY conservative.  I dont know how many hours you have, or how much TD time you have, but I would start out slowing adding some pounds by strapping divers weights on the tail spring.  When I am on wheels I run 8-12 pounds of weight on my tail spring.  But I am starting off at an empty CG of 12" too.

 

add some weight, go to altitude and play around with slow flight and stalls.. add a few more pounds and repeat.  You can tell when the plane starts to act tail heavy and not "normal" .  do all said slow work at altitude!  and get those flaps to where you can use them, your leaving alot of take off and landing performance on the table by not using them.

 

[Mendlerr 4]

Good to know, I still need to lose weight though. So does my airplane, haha

[wypaul 448]

Just plugging in the weights that you provided in your W/B with the Arms for my Avid I get an empty CG range of 12.89 and it seems strange to me with nothing heavy to the rear that you are having aft CG problems. Will you please provide the arms for your aircraft. Did you measure the Arms yourself? Weights are without fuel I assume.

Edited 24 Sep 2013 by Paul S

[Mendlerr 4]

I did not measure the arms and yes the empty weight includes absolutely everything except for fuel.  I simply used the Arms from the previous W&B.  Also, I was just reading through the Purple SkyStar Kitfox POH that came with my airplane and it specifically says that the small 6 Gallon wing tank is completely compatible with the wing storage area.  Does this mean that the small 6 gallon wing tank will drop into the wing storage area?  It got me a bit confused.  I'm also curious what the Kitfox Alunimum Header Tank fuel capacity is?  It does not have it listed on their website.

Edited 24 Sep 2013 by RMendler

[C5Engineer 1170]

My WB sheet shows my tail 40 lbs at  146 inches. Unless a IV is quite a bit longer 160 seems pretty far. Also curious how come your tail is 13lbs heavier. My empty CG is only 11 inches.

[Mendlerr 4]

On my previous weight and balance the tail only weighed 43.10 lbs.  I have no idea what would have added the extra weight back there.  I have looked and looked and just do not see anything out of the ordinary.

 

the only things behind my seat are the twing header tanks and lines, the elt and the strobe controller box.  That's IT!   I have no idea what added 13lbs to the tail.

 

We confirmed the weights 6 times on 2 different sets of scales and took the averages of all 6 readings.  All were within a pound of each other.

 

The official published w&b information for a standard Kitfox IV - 1200 from Skystart is 157.10" Aft.

 

In 2007 it is logged in my logbook that the tailwheel springs were updated to a newer style from Kitfox Aircraft Company.  This included one extra leaf spring and new cables.  After this date the W&B shows the tailwheel at 160.75 but no new W&B was configured.  Perhaps there is a mistake somewhere in my book because no where does it state that the newer style tailwheel springs are any longer or shorter then the originals.  At least I cannot find it.

 

One major change is the gove gear moved the main gear Arm from 3.20/3.30 Left/Right to .25/.25 Left/Right.  That did change the weight and balance

Edited 24 Sep 2013 by RMendler

[tcj 150]

Did you put a stand on the scale to raise the tail to level?  if so did you subtract tha weight from the tail wheel weight?

 

I would carefully remeasure all 3 wheel arms.  I seem to remember some 4s with grove gear having a negative main wheel arm.  For what its worth, my classic 4 tail wheel arm is 158.5 inches.

 

If you still have an aft cg problem then start removing items unnecessary for flight one by one.  Throw them up in the air and if they come back down, dot not put them back on the plane.  Seriously, there has to be one heavy kitfox. 

[Mendlerr 4]

I propped the tail up to flight level position using a 55 gallon trash can w/ lid, then I placed a piece of 1" thick plywood on top of that.  I set the scale on top of the plywood and then set the tail on top of the scale.  It worked out nicely.  I may rig up a plumb bob and meaure the arms for reassurance.  I believe its measured from the leading edge of the wing root, correct? 

 

I just ran into another problem.  I drained the tanks, replaced all the filters, refilled the tanks and I cannot get fuel to flow to the 2 header tanks.  It's like its vapor locked or I have a blockage in my wing tank lines.  If I put a little air pressure into the wing tanks they will slowly trickle down but they will not do it on their own..  I was looking at Kitfox Service Bulletins and I know this was a problem on the older header tank systems.  Guess I need to drain the tanks and remove the lines, see if there is a blockage first.  This annual is turning into a pain in the ass, haha

Edited 24 Sep 2013 by RMendler

[Mendlerr 4]

Well I accounted for 3+ lbs of the weight.  The fire extinguisher.  It's above the pilots seat.

 

The RadioShack Speaker behind the pilots seat can go.  It's only good for getting METAR's without headsets.

 

I COULD eliminate the header tanks but I would only have 1.4 Hours usable fuel w/ day VFR reserve.

 

I could remove the fuel flow totalizer, but it's probably only 2 lbs or so total and its nice knowing fuel flow all the time.

 

The cabin heat and air system could go.  I honestly have no idea what they weigh.

 

The battery weighs 14lbs in the box.  I'm sure a much lighter battery could be installed.  If I had a big budget I would go with a Braille.  $$$<2lbs

 

I already removed the Cordura cover from behind the seats and the kick panel carpets.

Edited 24 Sep 2013 by RMendler

[C5Engineer 1170]

Sweet only about 100 more lbs to go

[Mendlerr 4]

Haha I honestly don't think that is possible.  I'm thinking 600lbs will be the bare minumum my plane could weigh with the Grove Gear/Wheel/Brakes.

 

That's still 43 lbs though.  I've accounted for about 20-25lbs now.

 

I need more fuel capacity though.  I'm not going to ditch the header tanks at this point until I come up with a viable solution.   I would have to stop (literally) 4 times to make it to the beach.  That's 8 fuel stops round trip and 100LL ain't cheap, oil is not cheap either and I'm making $8 an hour at the moment.  In my buddies RV he can make the round trip and still have plenty of fuel left.  Wish I had done my homework before buying a 2-stroke!  I never would have imagined they burned 6GPH

 

If I can fit a fuel tank in the left wing storage compartment that holds atleast 4 gallons I will ditch those header tanks in a heartbeat!

Edited 24 Sep 2013 by RMendler

[tcj 150]

Yes, the wing leading edge is the datum.

 

What type are the black rubber fuel lines between the wing tank and header?  If they are Mil spec they will swell shut if they ever had alcohol through them.

 

By the way, a Kitfox must have a header tank.  It keeps the engine running if the wing tank unports during a turn.

[wypaul 448]

The IV fox fuselage must be a foot longer than the Avid MK IV.

Does the Fox call for a vent for the header tanks?

[Mendlerr 4]

There is a fuel line (rubber) that leaves the fuel tank on a 90 degree fitting, it enters the cabin where there is a clear glass filter, it then mates to another short piece of rubber fuel line before going through the fuel flow meter.  From here it mates to an aluminum line w/ blue anodized AN fittings.  Then the line splits into the manifold between the 2 header tanks behind the seat. 

 

From the right side header tank a rubber VENT line runs along the fuel supply line, halfway up it meets a ball valve.  From there is continues in a rubber line back into the upper portion of the wing tank.  (atleast it looks that way)

 

I'm not sure why there is a ball valve installed in the vent line but there is for some reason.

Edited 24 Sep 2013 by RMendler

[tcj 150]

The rubber fuel lines could be the fuel flow problem.  Mill spec was what all kitfox kits came with back then.  Its good for Avgas only.  Car gas eventually causes it to swell inside.

 

Some builders put a valve in the vent line.  Their theory is that it needs to be open only to vent the bubble out of the header tank when first filling it.  When the header is full they shut the vent line valve.

 

The wing tank is vented from the tube top of the tank cap so any gravity or fuel pump suction in the system will draw through the main fuel line from the bottom of the fuel tank.  If the header vent is open the theory is the flow in the main line will be less.  Their procedure if they run a tank dry or the tank un ports and the header runs dry, they shut the header vent line valve so the fuel pump can create suction in the main fuel line from header tank to wing tank and start the fuel flowing again.

 

As you probably have found in the service bulletins, the factory position on fuel systems is no valves or filters in the fuel lines from wing tank to header tank unless its a nose tank you can see the fuel level in.  http://www.kitfoxaircraft.com/support/service_bulletins/sb29.htm

[Mendlerr 4]

I replaced all the fuel line from the wing tank to the header tank.  The original fuel line was in 7 pieces all rigged together.  It is now 1 piece of clear tubing so I can see the fuel.  I removed the fuel flow meter and the filter, the filter was the cause of the restriction.

 

If I put say, 5 gallons in the wing tank and open the header tank vent valve, I get no fuel flow.  The only way I can get fuel flow to the header tanks is to open one of the fittings on the header tank and get a little suction going.  Doesn't take much, then the fuel starts a flowin' and it doesn't stop.  Is this normal.  Doesn't seem like it should be.  What happens when you run the wing tank dry so you stop and refuel, shouldn't the fuel flow into the header tanks on its own?  I guess I probably could have put the gas cap on and blown into it a little

 

I spoke with a friend at a local machine shop, he's got his A&P and he was saying he would build me a fuel cell aluminum header tank.  It would probably hold 7-9 gallons and replace the 2 plastic tanks I have.  It would also eliminate all of that plumbing mess.  Sounds like a good option when I get some money in the bank.

 

I also just got to thinking and I suppose with the vent line closed in flight the fuel pump will be able to draw the fuel out of the wing tank to the header tank. 

 

This all seems simple, I don't understand why I'm struggling with it so much, haha.  Sorry for all the questions.  I guess I'm just a little freaked out after almost running my header tanks dry with fuel still in the wing!

Edited 26 Sep 2013 by RMendler

[Mendlerr 4]

I also think I figured out the W&B issue.  It was stupid and a failure to double check, I assumed my angle gauge was calibrated properly..  I was using a dial angle gauge with a magnet attatched to the lower tube of the door frame to determine if the airplane was level.  Well just for giggles I decided to try it again today with a bubble level.  Guess what, the dial gauge was 4 degrees off!  This in turn caused the tail to sit 4 degrees low which is what caused the heavy tail.

 

TO ASSUME : MAKES AN ASS OUT OF YOU AND ME.  I will know to double check my equipment next time.

Edited 26 Sep 2013 by RMendler

[akflyer 1427]

I love it when something is solved so easily!  I learned that lesson when I first used a digital level... I was rigging floats on a plane and I triple checked with the digital level even though my calibrated eye said it was lying.  After I cut all the tubing to length and fitted the plane to the floats I knew it was way out.  Good thing all I had to do was shorten the front leg to get the plane back to 5.5 degrees instead of 8. 

 

Who knew I needed to read the directions and CALIBRATE and ZERO the digital readout against a known level first.

 

Glad you got it sorted out!

 

[Mendlerr 4]

haha I just cant help but beat myself up asking for everyones help when it was a measuring problem, haha.  The tail weight is 49lbs in ACTUAL level flight attitude.

[Mendlerr 4]

So after doing a little math I have determined I can remove my 2 header tanks and replace them with a 10 Gallon aluminum tank and still be within CG limits.  Does anybody disagree with this idea?  It would give me an extra hour of fuel, still be able to carry plenty of baggage and 350+ pounds of plt/pax.  I'm a little uncomfortable flying on the header tank only but it sounds like its a common practice.

[dholly 718]

Also, I was just reading through the Purple SkyStar Kitfox POH that came with my airplane and it specifically says that the small 6 Gallon wing tank is completely compatible with the wing storage area.  Does this mean that the small 6 gallon wing tank will drop into the wing storage area?  It got me a bit confused.

 

The locker fits in a wing bay with normal rib spacing, as do the oem 6 gal. tanks (aluminum or fiberglass). The 'compatible' comment, I suspect, simply refers to the ability to use both a locker and wing tank (in adjacent bays) in a single wing. I do not believe you could fit an oem 6 gal tank into a locker without modification. Remove the locker and install one of the large oem e-resistant wing tanks for the greatest fuel capacity.

[dholly 718]

n 2007 it is logged in my logbook that the tailwheel springs were updated to a newer style from Kitfox Aircraft Company.  This included one extra leaf spring and new cables.  After this date the W&B shows the tailwheel at 160.75 but no new W&B was configured.  Perhaps there is a mistake somewhere in my book because no where does it state that the newer style tailwheel springs are any longer or shorter then the originals.  At least I cannot find it.

 

Look in the KF4 forum here, I did a post about swapping the tail spring on my plane. I didn't measure them but did post pics showing the oem 1, 2, and 3 spring setups that would probably help. If you really need, I can measure them.

[EDMO 1078]

I am still hoping for someone to post a weight for a bare fuselage, so I can compare mine before anything else gets added to it. Any Avid or Kitfox except Magnum.

EDMO