Carbon fiber skin

[Phil Dubois]

Hello all,

does someone consider carbon fiber instead of fabric for fuselage skin ?

Phil

 

[M61A!]

I have made my turtledeck using carbon. Not sure how much the original would have weighed ( steel tube, aluminium sheet and fabric), but mine weighs about 3 kg. Considering sheeting the rest of the aft fuselage in carbon also, using Dzus fasteners for maintenance access. 2 pies of 212grams/metre seems quite adequate.

 

[Phil Dubois]

Hi M61A1 confirm you doesn't use any fabric on the fuselage ? How do you stick the carbon fiber on the steel tubes ?

 

[M61A!]

Hi M61A1 confirm you doesn't use any fabric on the fuselage ? How do you stick the carbon fiber on the steel tubes ?

The build is not yet complete, but the intent is to have a removable lightweight carbon skin attached with Dzus fasteners or similar.

 

[Phil Dubois]

do you now someone who already used this method ?
I suppose you will not drill the steel tubes. You will add metal tabs ? welded ? Why did you choose this way to do ? You used Dzus or the turtle deck ? May be some photos...

 

[subnoize1]

I have worked for a long time with carbon fiber and I wouldn't use it as a thin, non-loading bearing skin. To make it light enough you would have a terribly expensive skin that would be easily punctured, scratched and otherwise destroyed with any gravel of fod kicked up from the runway.

Carbon fiber for spars, great! Not so much for non-load bearing skins that will see abuse.

Now, that said, vacuum formed polycarbonate would be ideal. Weld the mount tabs to the PC and paint if from the inside and you would have a nearly scratch proof skin that would be a fraction of the cost and last probably longer than the aircraft its on.

PS. As cheap and quick as Oratex is, I really can't see the extra time doing either to be honest

 

[Drieman]

I have made a CF belly pan for my 2LS, I didn't like the flimsy lower stringer. I used 2plies of 6oz on each side and a polyurethane foam core. Total weight is 5.94lbs (~2.7kg), based on that piece I calculated the rest of the fuselage would weigh 25.5 lbs (11.6kg). I concluded that the additional weight wasn't worth it, and I will use the belly pan and fabric cover the rest.

I have also made a CF/Kevlar seat and pan to fit myself, 6'4" tall, without raising the turtledeck.

 

[Aviacs]

I have also made a CF/Kevlar seat and pan to fit myself, 6'4" tall, without raising the turtledeck.

Did you recline the existing position at all?
My seat pan is a sheet of light aluminum that sags down as close as possible to the control parts under it, with a 1/2" layer of foam on top.
Yet at a mere 6'-1/2" i still need an additional 2"+ of canopy/turtledeck height at a minimum to close the lid, esp with headsets on.

No doubt you have longer legs and me a longer torso, but i looked at reclining the seat position and it seemed too complicated compared to raising the canopy. If by chance you attacked your situation with a less vertical seating position, it could be informative for many of us?

 

[Drieman]

Did you recline the existing position at all?

No doubt you have longer legs and me a longer torso, but i looked at reclining the seat position and it seemed too complicated compared to raising the canopy. If by chance you attacked your situation with a less vertical seating position, it could be informative for many of us?

I did recline the seat back and sunk the seat pan to within 3/8" of the controls. I'll get some dimensions and pictures tomorrow.

 

[Drieman]

I made a curved seat back using a mold I made for a friends Pitts project, then using blocks and cargo straps I found an angle that will work to fit me and a headset under the canopy. My seatback is angled to intersect the seat pan about 3" forward of the standard location.



The seat pan was made to stop me from sliding forward on a flat surface while having enough clearance for the control stick stick to move full aft. I used enough layers of carbon for the needed strength, a layer of Polyurethane foam for stiffness, and one layer of Kevlar under the top layer to hold it together in the worst-case scenario. There is 1/2" clearance between the control stick and the bottom of the pan.



The carbon wraps around the tubes enough to snap into location, after the fuselage is blasted and epoxy primed, I'll bond the seat pan in place. The seat back uses the same carbon wrapping technique to lock to the tubes. When I am totally satisfied with the fit, after I make the canopy fairing which will also be carbon bonded directly to the plexiglass, I will add more layers to the seat back structure to withstand the possible aerobatic loads.



Like I said earlier, I am 6'4" tall, with a 39" seated height. O have just over an inch of clearance between my head and the canopy. I was trying to avoid cutting the seat frame out and lowering it, thankfully it worked out. Weight wise I am nearly two pounds lighter than the steel seat webbing and the plywood/foam seat pads.

 

[Aviacs]

My torso seems to be about 37".
Seat pan, is, if anything, closer to the controls.
I sat in AC a couple days ago, and probably can't recline mine much before the stick hits me in the crotch.

I can see a way to reduce everything with small adjustments, if starting over with structure. But probably have to live with what is here, and add a taller canopy. IOW, yours being a stretch probably offers just that slight amount of extra "wiggle" room. Mine is a standard -2

Thank you for the detailed explanation!
smt

 

[TFF]

There use to be a company who sold fiberglass fabric, that was glued on and shrunk with dope. Very popular with crop dusters. Extras have composite shells over the steel tube fuselage.

The issue is how do you want to do it? Like Ceconite? To make it light it would need to be moulded. To make the epoxy viscus enough not to run off with an open application will make it thick and relatively heavy. Wasting carbon doing that. You would also have to figure out how to keep wrinkles out and keep it from sagging while the epoxy cures.

It’s going to have to be your process.

 

[wsimpso1]

Hello all,

does someone consider carbon fiber instead of fabric for fuselage skin ?

Phil

Are you asking if folks are considering glueing on carbon fiber cloth in lieu of polyester fabrics? Usually polyester fabrics are glued on raw and then heat shrunk or stretched to position mechanically, putting the fabric in biaxial tension.

Many of the responses are for carbon fiber-epoxy composites, which is the usual manner for use of carbon fiber cloth. It is then either made stiff enough by laminating enough thickness or by fabricating a sandwich with a foam or honeycomb core and carbon-epoxy face sheets bonded to the core. If you are going to have that much material in the skins, you usually do not require the tube fuselage structure underneath it.

Billski

 

[fifidibosco]

Are you asking if folks are considering glueing on carbon fiber cloth in lieu of polyester fabrics?

yes. I would like to know if it's possible to use carbon fiber instead of fabric on metal and if that have already been made on sonerai.

 

[Tiger Tim]

I think the Razorback covering system uses fiberglass cloth, perhaps reading up on it could give you the basis of a carbon-based similar system.

 

[TFF]

Anything is possible. The question, of should and what you expect, has to be answered. Why carbon? It would be an expensive experiment off the bat. Not being used normally means you invent the process. I don’t know if anyone on any type that has tried this in this way. It goes against the norm when building is already hard.

 

[fifidibosco]

It's just a question of curiosity.
Except cotton/line all the other fabrics are synthetic, based on polyester (Oratex is not) and I tell myself that carbon fiber could be considered as a synthetic fabric as well, with its specific specs

 

[cblink.007]

Hello all,

does someone consider carbon fiber instead of fabric for fuselage skin ?

Phil

First question is "why?"...

I only ask, because CF is a very expensive range of fabrics that are used almost exclusively for load-bearing applications, not for cosmetic. The reason why fabrics are used on select light aircraft is because it does not have to carry a load (due to the tubular construction of the fuselage), and it is super light weight.

If you intend to use CF as a substitute for fabric, it will be both expensive, time-consuming and heavier than what you had at the beginning. So if you were wanting to go all-out with CF, you'd be better served designing a whole new aircraft.

Just my $0.02

 

[TFF]

Synthetic, yes, but totally different use. Fabric on an airplane is literally clothing. Carbon or fiberglass are usually not clothing. I have always wanted to see raw Razorback fiberglass covering unused. I don’t know if it was woven or a fine mat. I’m thinking it was mat.

To cover a traditional airplane, one has to shrink the fabric. At least to make it look right. Cotton and linen is water and shrinking dope. Dacron heat. The Razorback used shrinking dope. Carbon gets longer with heat but in reality it’s just stable. How do you get the wrinkles out around curves if it doesn’t shrink? What would you glue it to the airframe with? You could sew it, but it’s slippery and will want to unravel without a glue. There are lots of issues to overcome. While not impossible, it’s a one on one experiment. You would probably have to do it two or three times to get acceptable results and be very flexible in thinking out the issues.

 

[arj1]

You could sew it, but it’s slippery and will want to unravel without a glue. There are lots of issues to overcome.

I think it will in the lines of what Billski has said - you need to use glue, and when you add enough glue to get the desired result, it would be easier to remove the frame and just add a little bit more glue, so go for monocoque construction.