I am trying to firm up on the best bits and pieces to install in the cabin of the Bearhawk, in terms of "interior design" for utility and durability. I want to figure out the ideal balance between practicality and weight savings. I'm fitting out a bare plane so my starting point is practically nothing.

I am keen to hear what your thoughts are - what accessories wouldn't you be caught without, and what's dead weight?
What would your ideal cabin include or avoid? Is there anything you always wished you had or perhaps didn't have?
I'm thinking utility rather than instruments & minimum flight equipment here.

I will be hauling hiking packs, hunting equipment, diving & fishing stuff, skiing gear in winter, that kind of stuff most every trip.


To help give a train of thought:

Hard wearing flooring vs. traditional carpets?
Carpets are heavier and harder to clean, but catches sand & grit and stops it working its way into cracks and crannies between floor panels where it's even harder to get out and can wear fabric.

Interior liners?
Are the weight savings available from not installing any interior upholstery (fabric walls and headliner) worth the extra risk to the fuselage outer skin? I'm sure someone has some experience with that....

Would you have a dish-type gear tray that drops into the cargo area to contain the dirty packs, wet boots, blood & guts, etc?

I've been shown that protecting the areas where people will load gear/dogs/skis etc is important. Not everyone is as careful with your plane as you'd like. I have kick-panels and scuff strips, would you go further? I'm told a canvas flap would be a good idea.

Do many of you use a cargo net for keeping that gear where it belongs during turbulence? Worthwhile or waste of time?

What else would you suggest??

I use an automotive style rubber floor mat (with raised edges to contain water) under my feet. I did not use the aluminum wear plates that came with my kit. Easy to pull out and shake clean, best i;s the way it traps water when ski flying. I just wish it didn't say FORD on it.

A dish type tray is good for the portable generator. Oil and dirt seems to always stick to the bottom.

I am building a Bearhawk and what I did on the interior is put aluminum on the interior sides up to about halfway. I figured this is what will get banged the most in loading and unloading. The only fabric on the interior is on the seats.

You need at least a minimal interior if you're going to actually carry "stuff". To save weight, some folks are removing all interior materials and painting the inside of the exterior metal. That's well and good if you are REALLY careful with loading and unloading, but I can tell you that even WITH an interior you can dent the outer skin if you're not a little careful with loading. And, as you say, others are going to be a lot rougher on the plane than you might.

Cargo nets are a must for the kinds of stuff you've described. One of the issues with many airplanes is that there's no good convenient attach points to attach cargo nets in most airplanes. Also, if you're looking to have a cargo net made up, do not use the term "airplane" anywhere in the discussion. A lot of folks who make these kinds of things will suddenly find other work that desperately needs to be done, and your cargo net won't get done. Liability is a PITA.

Door sills will get banged up, but frankly, I'm not sure there's any really simple way to protect them. Your comment about a protective mat or something of the sort might work well. THat said, I found that I get pretty lazy when there are lots of loads to haul, and one or two extra steps in the process often get forgotten in haste. Be disciplined with a rubber mat and it might help.

As to floor covering, you definitely need something to protect the floors. Rubber matting seems to be the most durable and protects the metal floors well enough. They also clean up well. I can tell you from experience that animal blood is NOT a friend to aircraft aluminum, so do whatever you have to do to keep blood from getting into the belly of your airplane. If that means a rubber floor cover that reaches up the sides a bit, so be it. Lots of plastic coated tarps were always my answer. Crude, but cheap and effective.

Good luck.

MTV

In the building of my Bearhawk Patrol I have used .032 6061 for the floor in the baggage area with some beads rolled in. I'm going to try .025 in the pax cabin with a few extra tabs and hope its sturdy enough for foot traffic. I just finished to outside stringers so haven't come up with inside wall material but I'm thinking of using kydex for the baggage area up the sidewall and in the pax cabing the standard BH fabric covering that Bob shows in Beartracks newsletters. I have welded in six rings just behind the pax seat for a cargo net, two in the roof, two on the sidewall and two on the floor. I contacted a race car place that builds nascar style window nets and they told me they could do a custom job. As suggested I didn't mention airplane. I told them I had a dune buggy I needed to seal off the back seat. The super cub guys use the kydex so a search on SC dot org will net you plenty to read.

Buy a Kevlar or fiberglass skin & honeycomb or balsa wood core "sandwich panel" and simply cut it to the right shape. The airline and air cargo industry has already gone through the research and trial & error and weight vs. durability... and they use sandwich panels for baggage floors. Not the cheapest, but your airplane is probably not the cheapest either. Having something that performs well is probably worth a little more.

A light airplane will use a much smaller and thinner panel than a transport aircraft, but the principle is the same. My guess is a 1/2 inch thick honeycomb or balsa core panel will be more than strong enough, and will be one of the lightest solutions that has any durability. Maybe even 3/8 inch.

If you want to get fancy, laminate a strip of Kevlar or fiberglass to the edges that extends up the cabin side wall a few inches. This will prevent dirt and liquids from falling down into the belly of the aircraft.

Thanks to the Bearhawk guys for the replies, interesting to hear what everyone else is doing who's like-minded in terms of backcountry flying. I am really keen to keep aluminium out of the interior as much as possible, for example Georg H. did a full alloy interior (among other heavy things) and his plane ended up with just 700lbs useful...

MTV - it sounds like you're speaking from experience, and that is always the best teacher! You've raised some good points there and it really affirms a few worries I had about durability. It sounds like some kind of interior walls, cargo net, and cargo pan are a must-have.

Just a quick thought. A guy I know replaced the 1/4" wood floor in his luscombe with some aluminum sheet and dropped almost .5 pound. There isn't much floor in a luscombe so I thought .5 pound was significant. Al of the right spec can be a very good weight saver in some places. Not selected properly or placed in places where it is not necessary and it can be as bad as an anvil.

Yeah sorry I should have been clearer - the Bearhawk comes with an 0.032" alloy floor as default. I certainly agree that's the best solution. I'm not keen on wall / ceiling panels unless someone can say for sure they're necessary.

In the Beartracks magazine, someone did an analysis of interior covering weights using different material. From bubble wrap, to fabric, upholstery panels, or aluminium sheet. There were some big differences to be sure.

I guess that's the crux of my OP, trying to find that sweet-spot. So far I am swinging towards an uncertified light fabric interior liner, with the alloy floor, S/S wear strips on door frames and scuff-strip at the pilots feet, and some kind of plastic / rubber / fibreglass dish for the cargo area. Still not sure on decoDOT flooring vs. carpet around the seats....

I liked what blackrock did for his interior panels but I can't remember what material he used. Hopefully he will chime in. It was some lightweight board stuff that was just strong enough to protect the exterior fabric...I think.

whee wrote:I liked what blackrock did for his interior panels but I can't remember what material he used. Hopefully he will chime in. It was some lightweight board stuff that was just strong enough to protect the exterior fabric...I think.

The Bearhawk interior side panels are corrugated plastic board from a local sign shop, They came in 4x8-foot sheets and are about 1/8 of an inch thick. The head liner is Kydex (0.028). Both the corrugated plastic and Kydex work well. Kydex is heavier and more expensive. If I remember correctly, the headliner weighs about 8lbs so I'm thinking about removing it, but it sure works well and looks nice so it may survive awhile longer.

The best thing about corrugated plastic is how easy it is to work with and it is relatively strong. If I stain or wreck one, it is fast and cheap to make a brand new one. They come in all sorts of colors. The only down side is the stuff will sustain combustion so it wont pass a burn test, but then again in a fabric plane, I doubt there is much difference in the burn characteristics of a polyester, vinyl, urethane covered plane (Polyfiber) so I didn't see much point in worrying about that. They could be covered with a flame resistant fabric and that should take care of it, if there is a concern. I believe they may make a flame resistant product, too.

Below is a table of materials I considered using for the interior. This is the same table that Jon referenced in the Bearhawk manual except updated and in different units.

Material oz's/sqft
Kydex 0.028 3.80
Kydex 0.022 2.99
Auto Upholstery Fabric 0.91
Foil Bubble Wrap 0.95
Airplane Fabric (coated and painted) 1.60
Elmers 3/16" Foam Board 2.04
Sign Board - Corrugated Plastic(1/8") 2.46
0.016 Aluminum 2024T3 3.68
Upholsterer's Cardboard (1/16") 4.36
0.024 Aluminum 2024T3 5.76

These were measurements I had based on materials available. As always, YMMV.

Similar to blackrock I have a sheet of moulded coflute that fits nicely in the entire cargo area when the back seat is out. It protects the floor and a little way up the sides and contains most blood, hair, dirt and water which is easy to clean up afterwards. Simple to remove when carrying passengers, lightweight and cheap form of protection for the carpets or whatever you have on the floor.
My corflute sheet is white and surpises you how much dirt and blood you get in what you think is a 'clean' load

blackrock wrote:

whee wrote:I liked what blackrock did for his interior panels but I can't remember what material he used. Hopefully he will chime in. It was some lightweight board stuff that was just strong enough to protect the exterior fabric...I think.

The Bearhawk interior side panels are corrugated plastic board from a local sign shop, They came in 4x8-foot sheets and are about 1/8 of an inch thick. The head liner is Kydex (0.028). Both the corrugated plastic and Kydex work well. Kydex is heavier and more expensive. If I remember correctly, the headliner weighs about 8lbs so I'm thinking about removing it, but it sure works well and looks nice so it may survive awhile longer.

The best thing about corrugated plastic is how easy it is to work with and it is relatively strong. If I stain or wreck one, it is fast and cheap to make a brand new one. They come in all sorts of colors. The only down side is the stuff will sustain combustion so it wont pass a burn test, but then again in a fabric plane, I doubt there is much difference in the burn characteristics of a polyester, vinyl, urethane covered plane (Polyfiber) so I didn't see much point in worrying about that. They could be covered with a flame resistant fabric and that should take care of it, if there is a concern. I believe they may make a flame resistant product, too.

Below is a table of materials I considered using for the interior. This is the same table that Jon referenced in the Bearhawk manual except updated and in different units.

Material oz's/sqft
Kydex 0.028 3.80
Kydex 0.022 2.99
Auto Upholstery Fabric 0.91
Foil Bubble Wrap 0.95
Airplane Fabric (coated and painted) 1.60
Elmers 3/16" Foam Board 2.04
Sign Board - Corrugated Plastic(1/8") 2.46
0.016 Aluminum 2024T3 3.68
Upholsterer's Cardboard (1/16") 4.36
0.024 Aluminum 2024T3 5.76

These were measurements I had based on materials available. As always, YMMV.

Cheers for that Mike,

I'd be interested to know how you attached the panels to the interior? Do you have any handy photos?
I can see a case for having hard panels around the baggage area and lighter materials elsewhere.
What did you use to heat-form the panels?

Aside from the topic, you'll be pleased to know the Polyfibre on your plane actually does alright in terms of burn testing. It's in the manual somewhere I think. Well, once it's dried and set anyway..... if its wet with MEK or thinners burns pretty well.....

NZMaule wrote:Similar to blackrock I have a sheet of moulded coflute that fits nicely in the entire cargo area when the back seat is out. It protects the floor and a little way up the sides and contains most blood, hair, dirt and water which is easy to clean up afterwards. Simple to remove when carrying passengers, lightweight and cheap form of protection for the carpets or whatever you have on the floor.
My corflute sheet is white and surpises you how much dirt and blood you get in what you think is a 'clean' load

That's interesting - where did you get the corflute to make the tray from?? That sounds like exactly what I need.

Try these guys http://www.psp.co.nz/plastic-sheets/digital/corflute

You can get quite a good job if you gut and glue to shape/form. I didn't bother with that I just use it as a protective sheet mat with sides that slides in and out of the aircraft as required.

EZ where do you get the stuff you are referring to?

Battson wrote:
Cheers for that Mike,

I'd be interested to know how you attached the panels to the interior? Do you have any handy photos?
I can see a case for having hard panels around the baggage area and lighter materials elsewhere.
What did you use to heat-form the panels?

Some panels, like the rear bulkhead are held on by 4 screws and Mondonock clips attached to the tabs in the corners only. Others like the side panels are mostly held in place with industrial strength velcro and just one or two strategic screws. Adel clamps around tubes and riveted closed work well where there are no tabs. For the most part, the Kydex didn't require much heat forming in my case. In the few places where I needed to bend an edge, I just worked it with a heat gun and forming pliers just like you'd work aluminum.

I just looked and don't have any pictures of what I finally wound up with, I do have some from earlier unsuccessful attempts using plastic clamps made for securing electrical conduit. Be sure to place the Coroplast or Kydex as close to the outside tubes as possible or you loose space. This is especially true for the head liner. Mine is glued and velcroed to the stringers above the tubes and gives the cabin a much more open feel. Here is a photo from an early failed attempt using plastic clamps, id gives an idea of what can be done with Adel clamps, but be sure to go up to the stringers for the head liner!



The Coroplast can be cut half-way through and then taped with a colored vinyl tape to make sides, etc. It is really easy to make.

ccurrie wrote:EZ where do you get the stuff you are referring to?

ACP, "Aerospace Composite Products" is one of the "retail" level suppliers or mfg's. Tehachapi, CA. located at my beloved beautiful Mountain Valley gliderport. They are big in the model airplane world, so you will be able to get a thinner sandwich panel from them than almost anyone else. But they are definitely not the cheapest.

However, a Google search for balsa core sandwich panel, or honeycomb panel, will turn up hundreds of sellers, mfg's, etc.

Not that hard to substitute your DIY time for some of the cost either:
1) Cut vertical grain balsa or honeycomb core to size.
2) In-lay and glue in little plywood blocks at fastener locations.
3) Lay up one layer of bidirectional glass cloth and epoxy resin on a piece of waxed formica or plate glass. Squeegee excess messy pools of epoxy but leave a thin layer of gloss (meaning do not squeeze out every drop like you would if you were making a solid composite part)
4) Place core material onto wet wpoxy, apply plastic sheeting, then cover with cardboard and weights to clamp the glue joint. Let cure 6 hours.
5) Remove laminate from table, re-wax, put down another layer of glass cloth, impregnate with epoxy same as first side.
6) Turn the laminate upside down and put the exposed core down onto the wet glass cloth, put plastic sheet and weights on. Let cure 6 hours.
7) Remove laminate, trim and sand edges smooth. Drill holes thru plywood blocks for fasteners. Apply Zolatone or other paint as desired.