Composite interior panels

[svyolo]

I was watching one of Mike Patey's recent videos and he used a combination of CF and Kevlar for skins for the tail feathers. I am not advocating that for a BH, but I did use the combination for most of the interior. Most of the panels are a 2 layers, one of CF and one of Kevlar. The Kevlar is facing the interior of the cabin. On the small panels next to the front seats I used 3 layers for stiffness and strength, but they are only a few square feet. The larger panels on the left side I put some small balsa triangles and carbon tape on the hidden side for extra stiffness. I will either use Oratex or CF/Kevlar for the ceiling. Probably Oratex as it is even lighter and probably doesn't need to be removable.

They are about 16 oz/sq yard, and the side on the inside is Kevlar in case of a crash. The Kevlar doesn't add much strength, but it will never completely fail. It might crack the carbon, but the Kevlar will hold it together and you can repair it.

They are removable and I used very light homemade (.032 or .025) straps with a nut plate to mount the Kevlar, and hold it to the fuselage tubing. I will hunt for some pics and try to post them.

[robcaldwell]

Would love to see some picssvyolo . I am making carbon fiber panels for the rear bulkhead, cargo doors, wing roots, etc.

[Linusbear]

I have been using quarter inch last-a-foam with glass each side. Strong, light, cheaper than CF.

Scott Williamson
BH 4-place N924PL
former owner 509

[Nev]

Would also love to see photos. Is there any issue with galvanic corrosion? Mike added a layer of fiber-glass to the steel frame before the carbon.

[zkelley2]

Remember carbon breaks into knives when you crash. You'll never see it in the interior of my airplane.

[Russellmn]

That's why the Kevlar is the inner layer, the Kevlar will contain all the carbon and keep it from turning into flying shards. The carbon won't be able to cut the Kevlar either, so that's not a concern.

[Bcone1381]

Can you share the cost spent per pound saved ratio? Evan an estimate. Both for the CF/Kevlar combination and the Last-a-foam/glass sandwich. Also, would you change anything next time?

[Russellmn]

Carbon is heavier than your average fabric covering, and more expensive.

[svyolo]

I weighed mine at 16 oz/sq yard. Finished Dacron is supposed to be 10-20 oz/sq yard. Oratex is a bit under 6,

[svyolo]

Here are a couple of pics of the smaller panels next to the front seats. These small ones are Kevlar - CF - Kevlar. The bigger ones behind the left seat are 2 layers with the Kevlar on the inside and a few balsa triangle with CF tape as stiffeners. Fiberglass probably would have worked just as well but the Kevlar does make them pretty much indestructible.

[corefile]

What is the white substance between the tabs and tube. Is that to protect the tube from wear and galvanic corrosion,( carbon, aluminum, steel all coming together)

[BradW1062]

It would be interesting to know how much weight the tube clamps and nut-plates and screws add to the 16 oz/yard figure. Are these homemade clamps the same size as a standard AN742 plain clamp? They look a little larger, or longer at least.I had tested a similar arrangement using standard clamps and riv-nuts to hold the clamp together. The aluminum riv-nut is probably not as durable as a nut-plate, and maybe not self-locking, but it's light.

[gregc]

I copied svyolo's clips and I happened to notice a couple of extras in the shop today. Mine weigh 4.8 grams with the nut plate but without a screw. So, very roughly about 1 oz for every five clips.

[Nev]

Certainly looks like the business. Good work.

[tailwind]

Interesting, nice way to attach the nutplates without welding tabs on the tubes.

[svyolo]

A big part of my reason for doing it was my "knowing what I don't know". I wanted removable interior panels in case I screwed something(s) up. Cost? In my distant past, CF was very expensive. In my EAB world, it is far cheaper than Oratex, and closer in line with finished Dacron. So cost was much less of a concern. I never considered glass, but I will copy one or two panels in glass and see how they compare. I have some really nice, tightly woven, glass I use for kayaks/paddleboards. Maybe I will prefer it. Kevlar is almost completely indestructible. But that is probably its only great property. It is less stiff than glass.

The little clips I made to attach them were a bit of a PITA, but hopefully they work well, last long time. 3M 5200 adhesive, and a nut plate hold them in place.

[rodsmith]

I'm happy with my fabric interior but I understand the advantage of removable panels, very nice job!

[Archer39J]

Looks good! I was considering cut and folds with my left over sandwich panel to make faceted interior sections. Thought I'd decided on Oratex but this is getting me thinking again...

[Jhankins]

svyolo any photos of panels behind the left seat? I’m working on CF/Kevlar panels for the cargo and rear seat areas on the pilot side and am curious how you tackled it, specifically the rear window on the pilot side.

[svyolo]

I am away for the winter. Send me a message about mid April or I will forget.

Basically the window behind the pilot I just filled in the gaps between the window frame and the door panel with med density foam, an inch or so think. Just a square section or less. lightly glued to the interior panel side, and velcroed to the window frame. Looks decent.

[Daniel]

This is the approach I took. The blue tint is the kevlar component. As far as galvanic corrosion, i have two sets of rules i follow for either a wet space or a dry space. Interior panels are in a dry space so we do not have much to worry about. That being said, the coating on the airframe is sufficient isolation and my hardware is all aluminum acting as the sacraficial anode over the 4130 frame material.
20231028_192517.jpg 20231029_133234.jpg 20231029_133017.jpg

[rodsmith]

That is some beautiful work!

[Nev]

Woah. Nice !

[Battson]

I did use the combination for most of the interior. Most of the panels are a 2 layers, one of CF and one of Kevlar. The Kevlar is facing the interior of the cabin. On the small panels next to the front seats I used 3 layers for stiffness and strength, but they are only a few square feet. The larger panels on the left side I put some small balsa triangles and carbon tape on the hidden side for extra stiffness. I will either use Oratex or CF/Kevlar for the ceiling. Probably Oratex as it is even lighter and probably doesn't need to be removable.

They are about 16 oz/sq yard, and the side on the inside is Kevlar in case of a crash. The Kevlar doesn't add much strength, but it will never completely fail. It might crack the carbon, but the Kevlar will hold it together and you can repair it.

They are removable and I used very light homemade (.032 or .025) straps with a nut plate to mount the Kevlar, and hold it to the fuselage tubing. I will hunt for some pics and try to post them.

I would be interested to know what weights people are ending up with.

I tried a composite panel for the aft bulkhead, and once painted to match the rest of the interior - it weighed about the same as painted aluminium paneling. I was shocked, certainly not an intuitive result, but I weighed it twice and sure enough.

What's worse, is for all that extra work - composite isn't anywhere near as durable as aluminium.

For the floor in a "bush plane" you are going to get so much sand / gravel / debris inside, composite flooring would get all scratched up look a mess in just a few months - you'd end up covering it with carpet or deco-dot rubber mat anyway. Probably not a concern for a sealed airport traveler.

[svyolo]

The two layer interior panels I made should be about 15oz/yard sq. Very lightly sprayed with white paint. Similar weight to painted poly fabric. They don't feel very heavy and are very tough, even if they do "give". Probably as light as plastic aircraft interior panels, but a lot tougher.

My aft bulkhead is a single layer of 5 oz kevlar, so 7-8 oz/sq yard with epoxy and a super light rattle can coat of white paint. Kevlar isn't stiff at all, I would say the bulkhead is slightly stiffer than poster board. Easily rolled up tightly. I would describe it as a "cargo net" that looks like a bulkhead.

It is screwed to the bulkhead station with nutplates (tinnermans would have been easier, maybe even just snaps) on the tabs. To reinforce the screw holes I put 2 layers of scrap kevlar (already laminated with epoxy and cured). Just little 1" square scraps epoxied onto the back of the panel at the screwholes.

The bulkhead weighs 6 oz, painted.

I made one attempt at a cargo floorboard. I don't have a vacuum set up yet. Mine was unacceptable. Maybe some time in the future. I did use 1 layer of kevlar under the front seats as I will never put weight there.

1 or 2 layers of fiberglass would make perfectly acceptable interior panels and be cheaper. I had limited exp with CF, and zero with kevlar, so I did it as an experiment. Kevlar has some interesting properties for some applications, but is worthless for others.