A tinkerers Toys

[HighWing]

Some kind words from you guys have prompted me to start this thread. I plan on posting some of the Modifications I have done mainly on Model IV number two, but possibly some from No. 1 also.

I welcome comments and the critiques that come to mind as well. Also if any of you have had the "Tinker" addiction prompt you to make mods, feel free to share

Since we all tend to start in the back, That will be where I will start.

Post Number 1 -
This will focus on the fairings and gap seals I put on the empennage.

I did it as well on 96KL, but this time a bit different in design. I wanted an airfoil from leading edge to trailing edge without the hour glass shape at the hinge lines. The vertical stabilizer to rudder was fairly simple as the rod end hinge design gave ample space for a complete arc on the leading edge of the rudder. The hinge at the horizontal stabilizer to elevator was the challenge due to the limited space provided by the welded tube hinge design. This required some real effort. I made up some molds to use to get several shapes I could use. Some fit as molded, some needed trimming and re working while in place to provide an unencumbered range of movemtent - both vertical and horizontal. All ribs were fabricated from 1/4" LAST-A-FOAM from ACS. After cutting, the foam was coated both sides with a medium weight fiberglass cloth and epoxy resin. After final trimming, the edges were coated with "Micro" and sanded smooth.After covering, I did riblace for reasons that will be explained later.

[airlina]

lowell, thanks for sharing your ingenuity with the rest of us. After the first installment, I can' wait to see what else you have come up with. Great job on the empennage gap seals. Bruce N199CL

[av8rps]

Ditto, ditto... !!

Keep em coming. This is some great stuff Lowell!

[Paul Z]

Lowell,

Do you have a picture of the tool to make the fiberglass fairing on the horizontal stabilizer? Very impressive and simple design to build the molds used to fabricate the gap fill parts.

Paul Zimmermann

[HighWing]

Lowell,

Do you have a picture of the tool to make the fiberglass fairing on the horizontal stabilizer? Very impressive and simple design to build the molds used to fabricate the gap fill parts.

Paul Zimmermann

The link is to one of my albums.
http://www.teamkitfox.com/Forums/album.php?albumid=474

[HighWing]

Post Number 2
Elevator trim is a must in my mind.
On my first Model IV, I ordered the Speedster Elevator and it worked well. This time elevator trim became an an add on. The first thing I did was make a trim tab by folding a piece of aluminum to the desired dimensions and shape. I wanted it to fit between the two outer welded in tubular ribs. The chord of the tab then determined the cut out dimension of the middle rib. I found that if the trailing edge is cut out first, the weld stresses would result in the hinge spar bending toward the trailing edge, so the first cut was to remove some of the #2 welded rib to clear the tab and for the welding of the square tubing. After the half inch square tube was welded in, the trailing edge could be cut out without distortion to the spar. Piano hinge was used to connect the trim tab to the square tube. The servo was attached by welding in tabs – one offset to secure the servo. The 4-40 screws were welded to the tabs to avoid the need for a wrench on top of the tab. A servo cover was made to cover the servo at the bottom of the elevator. The attachment arm for the servo at the trim tab was made by hysoling a couple of pieces of aluminum angle together to form a T, then cutting and sanding to the final shape.

With the gap seal and trim tabs, I found elevator authority a nonissue with three point landings.

As a side note, a local pilot – Avid - wanted a different profile on his elevator for additional chord and brought some drawings. I helped him with the assembly and liked the design a lot. I would be tempted to use the design if building again. Two photos are attached to give an idea of that design. The first shows the trailing edge tube and its relationship to the existing profile of the Kitfox elevator giving significant additional surface area. The second shows aweldding jig with parts in place. One thing I really liked about it is the hinge on the top surface rather than between elevator and trim tab - much simpler.

[PNWJARED]

HighWing

Excellent Post. Very Clean! Very Cool! way to up the bar for the rest of us!

I assume the results are evident as well.

[HighWing]

Post Number 5.
When I began this project, there was an article in Kitplanes by the electronics guru, Jim Weir. In it he explained the electrical needs of LED bulbs and explained that for constant light output they needed constant current rather than a set voltage. He then offered a power supply in schematic form. I was hooked. When I finished my first one, I was surprised how large it was. Later experience with DC to DC voltage converters proved the concept. To change from 12 V. to the voltage needed for a typical LED required first conversion to AC to feed a transformer, then back to DC at the new voltage. Without adequate filtering, these can be really noisy. Flying under Sport Pilot, I really didn’t need the lights, but wanted them just in case.
The first pictures will show how I mounted the aft position lights. To avoid complexity, at least so I thought, I decided to position them on both sides of the rudder so there wouldn’t be a possibility of rudder shadowing. For that I needed some custom lenses. The lenses were made using a vacuum forming technique I learned in the dental office – Mouth guards and bleaching trays. No longer having the equipment, but knowing how it worked meant searching for components and building my own.

The lights on the wing tips used the same mounting method that I used on 96KL, but using the LEDs rather than the big bulbs. While working at United Airlines as a fueler, I noticed on the B-727s they had an interesting wing tip design that I adapted to the Kitfox. A “door” was cut out of the fiberglass. Then a lip was added to provide positive positioning with screws into nut plates for attachment. A lens was fabricated using heated Lexan forced over a plug made from the wing tip for shape. This was then glued to the “door”. A note on heat forming Lexan (Polycarbonate). A quirk of the material is that it is extremely hydrophilic – it absorbs significant quantities of water. To heat form it successfully, it needs to be dried in an oven for a time determined by its thickness. Otherwise it will look really interesting after forming - lots of steam bubbles within the plastic - large and small.

[jrevens]

As usual, really excellent, Lowell! You're a man after my own heart, but you are the king of innovation, making your own tooling, etc., etc.!! I love seeing what you have done!

[HighWing]

Post Number 6 Landing Gear

The landing gear came as a suggestion from a friend. He gave me some numbers and that became the goal – two inches taller at the firewall and 70 inches beween the brake mounting pads. To ensure the same fore aft relation with the new gear legs as the original bungee gear, it was important that the axles be exactly under the same point on the airframe so that was the first goal. The fuselage was positioned in three point the tail supported by the tail wheel and a support frame forward that held the bungee gear with the axles where they would be if in the wheels. A rail like structure was made as precisely as possible using inverted angle iron and it was fixed to the floor perpendicular to the long axis of the fuselage with Bondo. “A” frames with inverted Vs as feet to slide on the rails provided the means for adjusting the width of the gear legs with no fore and aft deviation and removable supports that fit into the inverted Vs provided the means to increase the gear leg lengths as desired. The A frame adjustment support dimensions were determined to get the desired 2” additional height at the firewall - increased leg length when removed. Then it was a matter of creating landing gear weldments that closed the gap between the axle mounted on the A frames and the gear leg attachments on the bottom of the fuselage. These weldments became the landing gear legs the spring struts and the cabane. The fairings were of thin aluminum to conserve weight.

A note: with the desire for accuracy, great care was taken to ensure proper tracking if wheels were on the axles. It was found, as many suggest, that the original gear (1992) was significantly toed in and appropriate adjustments were made to correct that.