Hubka's Kr-2S Custom Seat

My Kr-2S Custom Aircraft Seat

Problem: I just can't seem to keep it simple... I have back problems so I wanted an extremely comfortable seat.
I want a fast KR-2S so I wanted the seat as low as possible resulting in keeping the Canopy as low as possible.
I wanted my Rudder, Elevator and Flap cables/push rods to be centered and go through the seat area so...
I needed a hollow arm rest area.
*** Here's a tip for those KR builders new to composite work like me. Doing this nonstructurally critical seat project is an excellent opportunity to spend several days having fun learning composite construction and I did. I made mistakes and learned a lot doing my cockpit floor and seat from composites. I now have the confidence to go on to the horizontal stabs in a few weeks.

I love to experiment and love to do things different. I took some flack from a few local builder who said "keep it simple". That's just not me and if I could build this seat over I would change only one thing...... I would use a few ounces less expoxy.resin.

History: I built my fuselage 4" wider at the top and 6" wide at the bottom in the seat area. Thus...adding a hollow 2" wide arm rest resulted in an overall 4" wider seating area.

This seat bottom is 1/4 inch off the fuselage floor and thus requires the seat frame to be strong and ridged. Solution = Carbon Fiber and the seat will be firmly attached to the 2 spars. The added strength of the arm rest will ensure the seat will never bottom out on the fusalage.

I started with 3 pieces of 1" pieces of Celfort 300 Polystyrene Insulation (made by Dow Corning). You can buy Celfort 200 but 300 is denser/stronger and only a few pennies more. This stuff sands beautifully which can be seen by my rounded contours above. These hollows where achieved by gluing 60 grit sand paper to a 5 ft piece of 4" PVC plumbing pipe. The small wood strip on the right was epoxied in to provide screw material for the seat back hinges. I marked the edges of the 3 pieces of foam with black felt marker here. The white strip is thick glass bead micro slurry which replaced the hard glue joint. Hard glue/epoxy in the joint was mistake #2.

What was mistake #1 you ask ????. I used canned expanding foam which never stopped expanding for 8 hours and ruined my first seat attempt. I now recommend 2 part SuperFill foam epoxy foam. Sand nice and is stronger than the foam itself.

Again... I built my fuselage 4" wider at the top and 6" wide at the bottom in the seat area and there is room for this arm rest beam.

Ok...OK... I missed a few photo's. I hot wired the foam down to 1/2" and the arm rest is in place... and I have added a layer of carbon fiber over the initial layer of fiberglass. Then I added strips carbon fiber over fillets of SuperFill to round and strengthen the joining of the arm rest to the seat.

The arm rest is truly a multi functional component of this seat. It rests on both spars and is..
1) An arm rest for the pilot
2) A structural center piece allowing the seat to be strong and 1/4 " off the fuselage floor
3) A channel for rudder, elevator and flap cables/push rods and wires ( see a few pictures below)
4) The flap handle will protrude the forward top of the arm rest.
5) 1/2" foam was added to beneath the top of the arm rest wrapped with 2 layers of carbon fiber and 2 layers of fiberglass. This arm rest will be the stepping, pushing, holding etc. point in the cockpit. I would trust it to hold 500+ lbs

Here the seat sits on the spar wing stubs. It weighs 3.0 lbs

The arm rest was first cut out and carved from foam. Then wrapped in plastic. Then wrapped in a double layer of glass (1 fiberglass and 1 carbon fiber).

It was then capped and epoxy slurried with 1/2 inch of foam added and again wrapped with a double layer of fiberglass and carbon fiber. 4 layers total. I left to set for 2 days and then the foam plug was pulled out.

A 1/2 inch bead of SuperFill was added to the arm rest seat joint and 1" and 1.5" strips of carbon fiber were laid down.

SuperFill is great stuff

This is a rear view and show the arm rest to be totally hollow and the seat will be easily removable to access cables etc. below. You can just make out the 1/2" of foam sandwiched at the top of the arm rest for strengh.

OK. What kind of seat back are these???? They are translucent.
These seat back are built with "Parabeam 3D Glass Fabric"
http://www.parabeam.com/
The seat backs are 1/4" thick and consist of fiberglass, epoxy-resim and are hollow filled with air.
Mark Langford and a few other KR builders talked about this stuff about 2 years ago and I ordered some then. Because the seats backs must be strong but are not critical to the structure of the KR I decided to "experiment" with this stuff. Parabeam is expensive, hard to work with, a little on the heavy side...
But it is extremely cool and amazing space age stuff. Good for impressing the guy the thinks he knows everything.
Do I recommend it? .NO
Try it if you have a thick wallet or you like to try new stuff.

Notice you can see the 5/8" spruce of the lower fuselage to the left and right. This seat is only 1/4" off the bottom of the fuselage.

It is a real Low Rider. "The Hubka Low Rider Seat". I am 6' 1" and my son is 6' 2". It fits us fine.
This will allow my canopy will be up to 4" lower on my KR-2S than most builders. This should afford less drag and hopefully more speed... I will carry cushions behind the seat backs to allow shorter pilots (my daughter and others) to fly my KR. Because my wife 5' 5" can not reach the pedals at all. Is this a good thing ? :)

Here you can make out the 1/2" foam at the top of the arm rest in this pic. You can also see the carbon fiber reinforcement of the arm rest to the spar seat caps. A couple a screws will be needed to secure the seat lips to the spars. Once the plane is complete I will be able to remove the whole seats assembly in about one minute.

There's those translucent seat back again... I will probably go overboard on a lightweight good looking upholstery. Also... I may try TEMPER FOAM SEAT CUSHION a 3 piece 3 density foam because I have a sensitive back and really bad turbulance makes me go SHIT!!! that hurt!!! in a spam can.

Here's a look at the Parabeam used for the seat backs. It is amazing stuff.

Thanks for checking out this seat section. If you are interested in building a seat like this I'd be happy to provide email assistance.