Kitfox-4 floorboard or firewall options for access

[rogerh12]

Howdy all;

I started to install my floorboards today in my model 4 when I realized it would be held down by the rudder peddle brackets and control column mounts. I think this will be a problem later if I want to remove these components for service as under the floor boards will be fabric (so how do I get to the mounting nuts or inspect the tubs for cracks ???). I was thinking about using metal plates for floorboards instead of the wood as well, maybe make them removable without disturbing the controls, or maybe not run the fabric all the way to the front of the plane, and instead extend the firewall under the plane back to the seat area or something (and make the rear portion of the extended firewall removable with screws.

Any ideas?

Thanks in advance

Roger

[SkyPirate]

I would not replace the wood with steel,..to get the same rigid performance of the wood ,..out of steel would add weight ,.. it would also offset any pre designed heights that were accounted for in the design ,..the wood thickness versus the equivelant for rigidness in steel,..your other suggestion of making a removable plate's makes more sense,..just take into concideration your radiator location if your using the 582 or 912,..and your choice of landing gear as to how you conform the plates,..also the material you choose to make the plates out of and the support system for them

[rogerh12]

The metal in the floorboards would be thinner than the wood, and be made of Aluminum (0.062 aluminum diamond plate is available locally) or perhaps Titanium if I can gets some more cheap. I was thinking the stainless firewall would extend under the fuse, and the removable underbelly portion would be aluminum (a 6061 series or something like that). Oh, this plane is also a Tri-gear, so the nose wheel mounts must be taken in consideration, but the engine will be air-cooled only, so no water radiator will be required.

[HighWing]

I agree with your concern. It was after I built my first model IV that the Service Bulletin came out regarding cracks at the rudder pedal torque tube junctions. I had to remove the rivets securing the bottom firewall extension to get at the nuts for the torque tube pivots. I am building again and will install the aft edge of the firewall part to the floorboard like the radiator is mounted with a two or three through bolts. For the stick torque tube, by far the easiest way to make the nuts accessable would be to add some inspection rings to the fabric and then when necessary cut the fabric and replace with inspection covers. I put an inspection ring on the left side only as the pivot bolt in the right side is accessable.
Lowell

[enyaw]

Could you drill the tab holes larger and install rivnuts? We did this for our bagage compartment.

[Geowitz]

I just put inspection rings and left them uncut so if I do ever need to get to the nuts it will be easy. As Lowell mentioned you really only need access to the left side since you can then remove the tube once that side is removed. Also, as Lowell said you can mount the bottom section of the firewall with through bolts or some type of screw to make it removable to get to the rudder torque tubes.

[FoxDB]

Hello
On my model 1 following fuselage mods for my new landing gear prior to recovering I used these clip nuts http://www.aircraftspruce.com/catalo...es/0402052.php (http://www.aircraftspruce.com/catalog/hapages/0402052.php)
to hold on the stick tube brackets. This allows control and floorboard removal with no fabric problems. They are lock nuts so no concern with loosening.
Dave

[rogerh12]

Some really great ideas here, thanks for the pic of the underbelly, that helps me visualize the setup.
Anyone got a picture of the underbelly with the firewall installed??

The rivet nuts are interesting, but I wonder if they will hold up as well as actual fiber nuts, and I am not sure about the ease of removal later. The clip nuts I have used before, but I have also had the move on me and fall off during bolt insertion. I like the inspection holes perhaps best and the picture gives me something to work toward.

[Esser]

Depending on how you were finishing your plane I dont the checkerboard aluminum would weight more than the wood with carpet on top. Just a thought.

[SkyPirate]

the 1/8" tread plate aluminum / bright ,..which is grade 3003 aluminum is very workable ,.and it's reasonably priced,..the advantages of 3003 ,..it is the same material used for making fuel tanks so it doesnt stain easily,..it is easily welded ,..scratches, if not too deep can be buffed out too.
The only problem with it,..if your going to use the tread tape on areas where your heals go,..you might have to use a heat gun to get it to stick down to the surface due to the "tread" design in the aluminum ,..you could get the spray on rubber for this instead,..and now I believe you can get it in different colors ,..if not ,.the spray on tread that comes in the quart can that has to be reduced (which is a yellowish color )is paintable.
if you use aluminum instead of the wood ,..put something between the aluminum and the airframe where the aluminum would meet the 4130,..tape or split hose on the tubes spaced about 2 inches apart,.. the reason for this ,..vibration will wear the coating off /primer/baked enamel/?/of the 4130,.2 unlike metals rubbing on each other will cause oxidation/corosion,..dont forget to make spacers the same thickness as what ever you use to seperate the 2 metals where there are any thru connect points.

PS . if the aluminum proves to be too reflective ,..if you wash it with an aluminum cleaner it will take the shine off and leave it a light gray in color ,..remove it from the plane first ,..the cleaner is acid based

[SkyPirate]

Rivnuts work great 99% of the time ,..I have used them for many applications ,..but I take a small file and put groves onto the holes first so when the rivnut compresses,..it fills in the area/slot/ that I filed into the hole and helps keep it from spinning in the future, especially if it on an item that gets removed and replaced allot. you can get thru rivnuts or sealed,..I found the better the rivnut installer ,..the better the end result

[rogerh12]

"the 1/8" tread plate aluminum / bright ,..which is grade 3003 aluminum is very workable"

Ya, this is what I used on my Sonerai floor boards, and it worked very well, but I do need to protect the powdered coat on the fuse, so I will figure something out. As for carpet, I my very very strong opinion that carpet has no place in a cockpit where fuel tanks are located !!!! Carpet makes an excellent avgas sponge (don’t ask me how I know !!!) and probably an even better flame wick !!!! If fuel gets into your cockpit, make sure it can get out somewhere FAST (or you might have too instead).

Roger

[HighWing]

I have had frustrating experiences with Rivnuts. I once pulled the threads out while inserting. I like Nutserts. More xpensive, but can be found in quantity online. They require special tooling and take more time to install, but are steel and there are no dissimilar metal issues. Also regarding the diamond plate. With all the creature comforts I put in my first Model IV, it came in at 704 lbs. It is amazing when all the little light weight add ons become pounds. My buddy I flew with regularly weighed exactly 100 lbs less than I did. Just keep in mind that these things are airplanes. Weight adds fuel costs, take off distance, landing distance, climb and payload and can afect W/B. .125 alumimum weighs in at almost two pounds per square foot. For the dimensions of my floorboard something like ten pounds in a model IV, but I know we all know this and make our choices for personal reasons.

[rogerh12]

Looks like I figured out a solution of compromise on the model 4 floor boards that will let me remove the floor boards and controls / peddles later for maintenance or inspection of the tubing, if needed.
I cut the floor boards in half long ways, so they can be installed and removed more easily.
The seam in the metal boards will be filled with a little silicone, if needed.

The controls still hold down the rear of the one ½ floor board, with big old nuts so I can’t yank the stick loose (same with the rudder peddles), but the other half of the floor boards are held in place with simple nut-plates at the rear as nothing will try to yank them up (with the front held down with the rudder peddle brackets). Once I remove ½ the floor board, I can get to the nuts on the back of the other floor board, if needed. However, I do need to add 3 nut-plates to hold one of the right side rudder peddle brackets as that area below gets covered with fabric (the other 3 peddle brackets get covered by the lower firewall, but that portion of the firewall will be nut-plated together with the main vertical firewall for easy removal).

Well that’s my idea anyway. Oh, also the aluminum diamond plate is now available in 0.063, so it’s ½ the weight of 125 and is plenty stiff for my application (maybe I could even use something thinner? ).

Roger

[SkyPirate]

I'll bet if you do a little research at a place that makes extruded channel for screen windows/doors ,..you might be able to find a small "I" beam that you could put between the 2 halfs ,..just a thought,..no need for sylicone then l


actually I've seen it made out of rubber too,..trying to think of the application,..something that had a split window ? hmm

[rogerh12]

Lets see if this worked:

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[rogerh12]

Hey Guys:

Here is a PDF with some pictures of my metalized floor boards on my model-4-1200 They came in at 3 pounds, 13 oz and are very stiff, due to bracing and magnesium shims between the aluminum plates and fuse tubes. The floor boards are split length wise so that they (and the controls) can be removed after installation without making holes in the fabric ( for inspections or maintenance ). The aluminum is just type 5052, about 0.050 in thickness and work very well in this application.

As this is a tri-gear plane, the rudder brackets are now held down via nut plates and so are the aluminum plates as a whole, but the stick control bracket bolts are still held in with nuts (which are now accessible by removing an adjacent floorboard).

I will be installing the seat next, and I already have seat belts and an interior, plus some salvaged but otherwise finished doors, so soon I will be able to sit in the plane, close the doors and pretend to fly !!!!.

Roger


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