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Kitfox 3 Bushplane Project.

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Posted

This is definitely one of the few places where the mod is well worth the weight.

What is often done with the wood farings is prior to covering large holes (1"?) are drilled along their length to lighten them.  My friend Jim did this and said he recovered 3 pounds of wood chips after the drilling was completed.

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Posted

Some things are worth repeating!  :-)  JImChuk

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Posted

unless you have upgraded the struts, the wood fairing are structural and are required.  If you are wanting this to be a bush plane, put the fairings back on or make new ones.  When I put them on mine it was a 250 FPM climb increase and a 7-8 mph cruise increase at the same RPM.  Pretty significant in my book.  Take a look at the fairings that TJ made for his Mod I.

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Posted (edited)

unless you have upgraded the struts, the wood fairing are structural and are required.  If you are wanting this to be a bush plane, put the fairings back on or make new ones.  When I put them on mine it was a 250 FPM climb increase and a 7-8 mph cruise increase at the same RPM.  Pretty significant in my book.  Take a look at the fairings that TJ made for his Mod I.

What difference is there in the weight of the Kitfox snap-on plastic fairings with the wood fairings, if any? 

I think you need the 1" x .049" or .058" wall struts to use the plastic ones like Leni did?  EDMO

Edited by EDMO

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Posted

Yes, the Kitfox plastic covers are for 1" diameter tubing.  Honestly, I think wood farings would be lighter, not by much, but lighter.

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Posted

Ok so what are my options here? According to the build manual the lift strut speed fairings were optional, was it the same strut whether or not you ordered the fairing option? I'm assuming it is, but want to be sure. If it's going to hurt my climb I will add it back on, but will have to buy new ones, I don't want to reattach the warped ones that came off and have the same issue when I'm all finished. 

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Spent a bit today cutting out balsa plugs for the ends of the ailerons and hysoled them in, will flatten them out and fill them tomorrow. 

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Posted

Good luck "buying" them somewhere.  Airdale is gone and Kitfox doesn't do wood any more.

Your best bet is to find a local cabinet shop and have them made.  It will be faster and cheaper in the long run.  Most of the guys I know made them out of plane, clean Doug-Fir 2x4s cut down with a table saw.

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Posted

Suggestion:  I would have to go measure my KF3 struts, but think they may be 7/8" - couldn't you glue on some sort of 1/16" thick spacers, or split tubing of some kind to make at least several areas 1" diameter, and then you could use the plastic fairings that Kitfox sells?  EDMO

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Posted

Foam with a thin layer of fiberglass would be plenty strong, and very light.  Cover with fabric, paint and move on.  JImChuk

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Posted

Foam with a thin layer of fiberglass would be plenty strong, and very light.  Cover with fabric, paint and move on.  JImChuk

Why cover with fabric?   If you wrap the fiberglass around the struts I don't think you would need fabric - just paint.   ???  EDMO

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Posted

Easier to match the paint, also the fabric will hold the fairing on that much better.  JImChuk

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Posted (edited)

Easier to match the paint, also the fabric will hold the fairing on that much better.  JImChuk

I would vote for another layer of fiberglass in the layup with fabric over it for a "peel ply" and be ready to paint - Nothing sticks to unwaxed painted metal more than epoxy.  Supposedly there is paint to match, like what you put on your cowl. 

"To each his own".  EDMO

Edited by EDMO

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Posted

1/4" X  11/2" pine lattes glued to the backside of the tube and then covered with fabric is what I used for my "Bush Gear" to fair them. Worked great and it is light. It will not add much to the structure although.

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Posted (edited)

unless you have upgraded the struts, the wood fairing are structural and are required.  If you are wanting this to be a bush plane, put the fairings back on or make new ones.  When I put them on mine it was a 250 FPM climb increase and a 7-8 mph cruise increase at the same RPM.  Pretty significant in my book.  Take a look at the fairings that TJ made for his Mod I.

Are you sure about this (required for structural reasons)?  I have a Kitfox III and the build manual lists the lift strut fairings as optional.

Model III lift Strut Fairings.png

Edited by LSaupe

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Posted (edited)

Required by Avid, not Kitfox. 

As to Doug-Fir, it can be had cheaply, everywhere.  Is there better?  Sure.  And what would the weight difference be?  A pound or two?  You guys are loosing sight of the forest because the trees are in the way. 

Edited by Av8r3400

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Posted

Alright well it seems unanimous, and I have a neighbor who has a wood shop in his basement so I will go confer with him this AM about fabbing up a new set of fairings for the lift struts. The powdercoat on them got damaged a bit so Im going to have them blasted and powdered before I put on the new struts anyhow, but Im sure him and I can make a set. Hopefully going to be getting this all welded up soon and then real progress can begin with covering the fuselage covering and bringing the panel/ landing gear/ lift struts/ wheels to the powdercoater so he can begin that. 

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Posted

Maybe you should try to find the one side Airdale W.I.B. gear leg you need before putting $ into the oem bungee gear. Hey, you never know unless you ask.

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Posted

Maybe you should try to find the one side Airdale W.I.B. gear leg you need before putting $ into the oem bungee gear. Hey, you never know unless you ask.

GOOD IDEA! Does anyone have a right side wide gear for a kitfox/avid? I have a left side sitting here and would love to upgrade to the wide gear on the plane. 

Spent some time with the table saw playing around with the old warped speed fairings, trimmed about 1/4" off of the front and put the blade at a 30 degree angle and cut a new larger pocket to allow the tube to nestle into it. Worked great and actually 3 of the 4 pieces are now pretty much straight. The 4th I wetted down and put it between 2 sawhorses with a 10 pound weight in the middle, hoping it dries straighter. Anyhow happy to have made progress on that front. 

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Posted (edited)

I was tempted to suggest exactly what you did, but didn't know how much warp was in the wood fairings.  Good Show! 

If Balsa hadn't gotten so stupidly high, I think that would have made the lightest and strongest fairings.   

Unless you make some strategic saw cuts at 90 degrees to the length about half way thru, that fairing may warp again.   EDMO

Edited by EDMO

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Posted

that's a good idea, I'll do that . My plan is to attach them and use superfill to really streamline them to the struts, and paint them, no fabric covering. That's how my Mkiv was and looked much cleaner than these did covered in cloth. Will probably have to permanently mount my jury struts as well I suppose

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Posted

while it may be optional on the KF 3 if you intend to use it as a true "bush plane" and beat it up a beat on rough terrain etc. I would do anything I can to keep the wings from folding up and hitting the ground on a hard landing or impact.  The fairings give you a whole lot more compression strength and will help your take off, climb and cruise.  Well worth the effort you are going through to re-install them.  If you are only flying off a manicured grass strip you could play golf on and are not worried about clearing trees on a short strip or cruising any faster then you could leave them off :lol:

 

:BC:

 

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Posted (edited)

Yes, the speed fairings have been fixed and will be going back on the plane after I get the lift struts touched up. Still waiting on welding so spent some time doing odd jobs that I can still work on before its welded up. Spent some time lightening gussets, still a few to do but removed the centers from them and should save a pound or more. Also cut balsa plugs for the ends of the flaperons and hysoled them in, will fill and sand smooth before paint. Bought a couple sheets of .060 makrolon and will be cutting myself a new windshield/ door windows today. steady progress. Also got my new wingtip lights in the mail, they look nice!

 

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Edited by Neloner
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Posted

I would hold off on cutting and riveting the door skins until you bend the frames to fit your wide body kit. Might make enough difference that using the old ones as templates and match drilling to them could cause slight alignment problems.

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Posted

Well I already cut them but wasn't going to drill anything till the doorframes are for to the widebody

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