Whats under your Seat ???

[rogerh12]

As a fiberglass seat breakage could land the pilot on top of the control mechanism, I was thinking about putting “something” in between the seat and the lower fuse tubes, you know, to catch the seat before it ends up jamming the controls.

[cap01]

The seat doesn't need to break , just have the forward lip of the seat slip back off the tube and the same thing happens . I have a 2in nylon strap under the left side and the underseat storage box under the right seat

[Dorsal]

Butt Block
http://www.teamkitfox.com/Forums/showthread.php?t=2586&highlight=butt+block

[Dave S]

Hi Roger,

This is worth thinking about since there are some documented cases of the seat coming down on the alieron control rod.

Most of the problem has had to do with unsecured or improperly installed seats.

John Mc Bean sells some aftermarket seat storage buckets which can be bolted or riveted on the bottom of the seat - this installation prevents the seat from coming down on the control rod if the seat cracks/breaks Also provides a great place to store tools and other heavy but small stuff. Easy enough to fabricate a hinged door to cover the seat bucket access hole - I think the hole is about 10" X 10" or thereabouts.

I think the newer seats come with the buckets formed as a one piece fiberglass assembly but the retro-fit seat buckets certainly work well.

Other folks in my neighborhood have done the seat strap as cap01 indicated

Sincerely,

Dave

[catz631]

Here's what is under my seat.

[jtpitkin06]

My kit, a SS7, came with seat storage compartments molded in the pan. For additional support I added the "butt blocks" mentioned in a previous thread.

The blocks formed a tunnel and were sized to just fit between the seat and the fuselage tube. The flaperon control rod is adjusted so it never touches the seat, frame or butt blocks. Like most builders the control rod required a little tweak and minor bend adjustment to be clear of all obstructions.

Because there are some reports of the front lip of the seat pan breaking or cracking I did the installation on both seats. There is no control rod on the right seat, but the additional support may prevent seat pan failures. It made the seat pan feel much more solid with the bottom support.

The notch in one of the blocks visible in the photo is clearance for one of the storage lid hinge bolts.

John Pitkin
Greenville, TX

[HighWing]

Roger,
I have to wonder. I fear you are on the way to creating the world's heaviest Model IV with your thoughtful but weight introducing Mods. With that in mind, consider the evolution of the Kitfox seats. The early Kitfoxes had distinct curls front and back on the seats. Some guys drilled the metal tube and used sheet metal screws. Some drilled the seat pan and used Nylon Zip ties (me). I know of at least one person that used nothing to secure the seat and put many hours of flying with no issues - and his home base was a strip in his back yard and had lots of off airport landings.

Then the "Heavies" came along and the flat part of the floor boards were shortened at the aft end then angled up to the seat edge. I think I understand the thinking that precipitated this change, as I will be putting something to keep junk from sliding under the flaperon torque tube and jamming it. During my build, I am always finding nuts, bolts, wire fragments and terminals there. This has always concerned me as a safety issue. But back to the story. In order to accommodate the angled part of the floorboard the forward lip on the seat pan was shortened to almost nothing. This is when the seat pan slipping issues started and as most of us do in life we all started comparing apples to oranges and worrying about our Model I, II, III, and IV seats forgetting the history.

If you are intent on something, I would suggest that you avoid the dead weight fix and do something utilitarian like the under seat storage. My current project had the seats already cut for bins by the first owner, and I made my bins with aluminum sheet.
Lowell

[rogerh12]

Thanks for all the great advise and pics guys!!!!

Looks like I have some thinking to do.
I am pretty handy with sheet metal, so perhaps I too will just make
some seat storage compartmens/butt-blocks to kill two birds with one stone.

Have a good weekend!!
Roger

[t j]

Make sure it's not centered under your butt crack. It might split you in two in a really hard landing that crushed the understructure.

[CDE2FLY]

I used a strap on both sides of the seat as well consisting of perforated metal pipe support strapping sold at hardware stores (or Lowes/Home Depot/Grainger's). Easy to adjust for the correct length by wrapping the strap over the steel tubing in front of and behind the seat back and securing with a nut and bolt through the perforations. The strapping is sold by the roll and is cheap, easy to install, and secure.

http://www.grainger.com/Grainger/CADDY-Hanging-Strap-1RUR2

[896tr]

I think the pipe strap might be a waste of time as the max.load rating is only 10 pounds. Just my opinion.

[HighWing]

Using metal strapping is a fresh idea, as far as my memory goes. Wood blocks and Nylon straps have been mentioned. I didn't think about the mild steel's yield strength, but did think about the 4130 strips available at ACS - available in numerous widths and thicknesses. Actually hardware store parts have been sort of a don't go there issue in our neighborhood ever since Rev. Bill built his Dean Wilson designed biplane (pictured below) - which he planned on using in his African humanitarian efforts. It was the talk of the town that much of the materials came from Ace Hardware.
Lowell

Notice the multi-layered flaperons for superior STOL performance.

[CDE2FLY]

Not sure why the strapping is only rated at 10 pounds. Assuming it's mild steel (worst case) the tensile strength would be around 60,000 psi. Based on 24 gage (.0239 inches thick) and 1/2 inch width (3/4 inch minus a 1/4 inch hole) the cross sectional area is .01195 square inches so the strap should hold just over 700 pounds until it fails in tension. Two straps would be good for 1400 pounds (almost 3g with 500 pounds worth of pilot and passenger).

A thicker (.038 inches) strapping material is also available which would increase the load to 1140 pounds per strap or around 4.5 g with 2 straps and 500 pounds of weight on the seat. With 4130 steel, the loads could increase by about 1.66 times that of mild steel since the tensile strength of 4130 is around 100,000 psi.

http://www.grainger.com/Grainger/DMC-Hanging-Strap-4NCC6?cm_sp=IO-_-Home-_-VTV70300505&cm_vc=HPPVZ3 (http://www.grainger.com/Grainger/DMC-Hanging-Strap-4NCC6?cm_sp=IO-_-Home-_-VTV70300505&cm_vc=HPPVZ3)

Again, this is just to suppliment the design that only calls for tie wrapping the seat lips to the fuse tubing....so far hundreds of landings and it hasn't let me down yet. Could also double up the strapping on each side to be conservative.

[czkree]

I used the 1 inch yellow tie down strap 15' long from local home builders store. (home depot) 1000 lbs rating, under the pilot seat only. Light weight easy to work with. Also runs under the seat 3 times if you use the 15 foot piece.

[896tr]

I don't know why the rating is only 10 pounds either but in your original reference to Grainger these are the specs. for the strap.

Item Hanging Strap
Type Perforated
Max. Load (Lb.) 10
Material of Construction Electro-Galvanized Steel
Length (In.) 120
Width (In.) 3/4
Description/Special Features Light Duty, Residential Pipe Support; Strap Gauge 24
Package Quantity 1