Kitfox Series 7 Super Sport - Show Me Fox

[Jason Murphy]

Scarlett decided she was going to come visit while I worked on things. I have a terrible habit of distracting myself from my studies as my CFI Checkride approaches.

Regardless I worked on the false ribs beneath the wing tank, door joggles, and floorboards today.

Fit false ribs beneath wing tank.

Used dremel to trim back material on the false rib until it cleared wing tank.

Using index lines I had placed on the tank previously initially bonded false ribs to tank with Super Glue. Followed behind with a fillet of hysol.

I plan to sand these false ribs to match the contour of the adjacent ribs.

Door Frames Revisited: Used a straight edge to check how fabric will come off of the door frame joggle. The joggles protrude outwards. I gave the material some loving and massaged it in alignment with a straight edge running from the bottom tubes of the fuselage to the door joggle. I will need to revisit this step and make some adjustments to the door joggles. I also plan on splitting a 5/8” tube to provide a transition between the landing gear brackets and make that transition smooth.

Floor Board Tabs:

Earlier in the build I had made the decision to use tinnerman clips and sheet metal screws to attach the floorboards. There seems to be a great debate over the use of Rivnuts within the community. I would much rather use a machine screw over a sheet metal screw. I drilled holes that measure 0.200” A #6 Rivnut calls for a hole that is 0.189” from a #12 bit. I could not imagine 0.011” oversized hole could result in trouble especially if I were to have a secondary method of securing the Rivnut such as Hysol or the green sleeve locking compound used earlier in the build.

It seems that it is common place that the tabs on the floorboards are set below the tubing it is attached to. This results in bowing off the floorboards if they are snug.

I have been troubled by this situation for longer than I would like to admit and I have possibly developed a solution. If I were to use a Rivnut with a long grip and secure a stack of washers on top of the flange if it would be the least invasive way to bring the mounting surface up to flush. I would of course use an adhesive to protect against the dreaded spinning Rivnut.

I would appreciate anyone’s thoughts and feedback on this topic.

[Geek]

I used the rivnuts all over the place. Installed them using the green sleeve locking and have had zero spins. I too saw the difference between the tab and the frame tube and after installing the rivnuts, I shimmed the floorboards using pieces of birch that I ripped on the table saw to the right thickness and used wood glue to attach them prior to varnish. You can see the two shims on the lower corners of the floorboard. In some places, the top of the rivnut took up the space between the tab and the frame. The head of the machine screw was just less than the diameter of the rivnut head so the whole grip on the board to the fuselage was done right there. No bowing of the floorboards and it is so nice to take those machine screws in and out (cause I wound up doing it a bunch). The floorboards don't need a major torque job done on them either so if you were to spin one of the rivnuts after using the green bearing lock and it's 7000 in/lbs shear rating, you're using your gorilla strength. Those screws just hold the floorboards down secure but there is no real load on those fasteners. For that reason, the tinnerman nuts would work just as well but like you, I like the machine screws for where I know I will be accessing those areas.

Just my 2 cents, opinions will vary. Greatly.

Gary

Floors 1.JPGFloor Boards 3.jpgBaggage Rivnut.jpg

[jiott]

FWIW, I used tinnerman nuts with machine screws, not sheet metal screws. Tinnerman nuts are built to work with machine screws. The nice thing also about tinnerman nuts is they have a spring loaded grip so its like a self locking nut, so you don't have to torque them all the way down and bow the floorboards. They also can move around some to compensate for a poor lineup. Cheap and easy to replace if ever needed.

[Pushboy]

Gary— what’s the black material added to your floorboards?
And what do all the zip ties do?

Dave


Sent from my iPhone using Tapatalk

[Jason Murphy]

I am not so sure about the black material on his floorboards. I believe that he is using the zip ties as a secondary measure to secure the velcro which the carpet and seats from the Kitfox Upholstery Kit uses to keep the seats and carpet in place.

[Jason Murphy]

FWIW, I used tinnerman nuts with machine screws, not sheet metal screws. Tinnerman nuts are built to work with machine screws. The nice thing also about tinnerman nuts is they have a spring loaded grip so its like a self locking nut, so you don't have to torque them all the way down and bow the floorboards. They also can move around some to compensate for a poor lineup. Cheap and easy to replace if ever needed.

Thanks Jim, I have not tried using the tinnerman with a machine screw I may have to try that out. I have the tinnerman nuts in place I agree they are economical and easy to replace which is why I had originally went that route.

[Jason Murphy]

I used the rivnuts all over the place. Installed them using the green sleeve locking and have had zero spins. I too saw the difference between the tab and the frame tube and after installing the rivnuts, I shimmed the floorboards using pieces of birch that I ripped on the table saw to the right thickness and used wood glue to attach them prior to varnish. You can see the two shims on the lower corners of the floorboard. In some places, the top of the rivnut took up the space between the tab and the frame. The head of the machine screw was just less than the diameter of the rivnut head so the whole grip on the board to the fuselage was done right there. No bowing of the floorboards and it is so nice to take those machine screws in and out (cause I wound up doing it a bunch). The floorboards don't need a major torque job done on them either so if you were to spin one of the rivnuts after using the green bearing lock and it's 7000 in/lbs shear rating, you're using your gorilla strength. Those screws just hold the floorboards down secure but there is no real load on those fasteners. For that reason, the tinnerman nuts would work just as well but like you, I like the machine screws for where I know I will be accessing those areas.

Just my 2 cents, opinions will vary. Greatly.

Gary

Floors 1.JPGFloor Boards 3.jpgBaggage Rivnut.jpg

Thanks Gary, I will probably order some rivnuts from spruce and do some testing. Rivnuts defiantly have a clean appearance when they are installed. I purchased the Marson Riv Nut tool at the recommendation of a friend and I have lots of the Green Locktite used to install the bearings. What is the material you are using for a skid plate for your heels? I will be doing most of my own interior and I was probably going to skip carpets in lieu of the mahogony floorboards I cut.

[Geek]

I am not so sure about the black material on his floorboards. I believe that he is using the zip ties as a secondary measure to secure the velcro which the carpet and seats from the Kitfox Upholstery Kit uses to keep the seats and carpet in place.

Thanks Gary, I will probably order some rivnuts from spruce and do some testing. Rivnuts defiantly have a clean appearance when they are installed. I purchased the Marson Riv Nut tool at the recommendation of a friend and I have lots of the Green Locktite used to install the bearings. What is the material you are using for a skid plate for your heels? I will be doing most of my own interior and I was probably going to skip carpets in lieu of the mahogony floorboards I cut.

I use the same Marson tool for my rivet installs. It works well BUT like all rivnuts, if you get a bit over-aggressive on trying to pull them real tight, they can/will strip. You get a feel for it after you have done a few and the Green Loctite is your friend.

The heel plates are .06 aluminum. Probably an overkill in thickness and weight but that's what I had. Your floorboards look really nice and with the heel plates, will visually turn out really nice I think. If I were doing it again and didn't have carpet, I might think of using .06 ABS sheeting instead of AL. Heels wouldn't wear through the color and take on an ugly look. But hey - that's just me.

You are correct about the zip ties. They are a secondary means to hold the Velcro. It's one of those Brandon suggestions in the interior install instructions.

Keep at it.

Gary

[jrevens]

Hi Jason,

I made some scuff plates for my floorboards out of 0.015" stainless steel shim stock. I think the material was "half-hard", so it is very durable & scratch-resistant, has a nice springy temper and cuts really cleanly & easily with smooth jaw hand shears. I put a "scuffed" finish on them with a scotch bright pad. After doing that I decided I really liked the look of the carpet from Kitfox, and ended up installing that.

[Jason Murphy]

I use the same Marson tool for my rivet installs. It works well BUT like all rivnuts, if you get a bit over-aggressive on trying to pull them real tight, they can/will strip. You get a feel for it after you have done a few and the Green Loctite is your friend.

The heel plates are .06 aluminum. Probably an overkill in thickness and weight but that's what I had. Your floorboards look really nice and with the heel plates, will visually turn out really nice I think. If I were doing it again and didn't have carpet, I might think of using .06 ABS sheeting instead of AL. Heels wouldn't wear through the color and take on an ugly look. But hey - that's just me.

You are correct about the zip ties. They are a secondary means to hold the Velcro. It's one of those Brandon suggestions in the interior install instructions.

Keep at it.

Gary

Thanks Gary, maybe the best route for me to take is to order a few extra and try them out and see how much I can abuse them before I try and put some in my fuselage. After I get the tool setup on the sideline put it to work doing the real work.

I have 0.020 I may be able to use. It may be a touch on the thin side but would be easy to work and I have an edge rolling tool that would put a very slight taper on them to keep the edges tacked down.