Swap fabric with carbon?

[Cc__]

I’ve been quite interested in the bearhawk 5, but I’m really not a fan of fabric on control surfaces, I was wondering if it would be safe to do carbon fiber instead? If so, how many layers?

 

[kyleb]

You'd do well to ask that question on a Bearhawk or Homebuilt specific forum. The general answer is that adding weight to control surfaces is a bad idea due to flutter risks. Also, you don't just cover an aluminum structure with carbon fiber. That's a no-go due to material compatibility issues including corrosion... You'd need to completely redesign the surface.

 

[donjohnston]

If the control surfaces are fabric then going to carbon fiber is probably going to change their weight. This will have an impact on the control surface balance. If it were me, I would check with the factory.

 

[Bell206]

but I’m really not a fan of fabric on control surfaces,

Interesting. Do you have a specific reason why not a fan? Regardless, keep in mind carbon fiber is not necessarily the best product for all applications. Would definitely discuss with the kit OEM as you could open a whole slew of issues by simply swapping it out on your own. From a historical point the last part to be metalized on newer aircraft designs was the control surfaces.

 

[moparrob66]

I think its definitely worth investigating, not just for control surfaces but for any fabric surface. You would want to be sure that you arent adding too much weight or creating more problems than you hope to solve.

 

[nauga]

I think its definitely worth investigating, not just for control surfaces but for any fabric surface.

But why?

It's not going to be lighter, it's not going to be cheaper, and it's not going to be easier to work with. What's the benefit of a retrofit to an airplane that's not designed to take advantage of it?

Nauga,
itchy

 

[moparrob66]

It could be lighter, depending on how thin you can get the fabric. Probably stronger, maybe last longer in the sun. Dont get me wrong, traditional fabric is entirely adequate, but would the flapping and fluttering create drag more than a rigid surface?

 

[nauga]

It could be lighter, depending on how thin you can get the fabric. Probably stronger, maybe last longer in the sun. Dont get me wrong, traditional fabric is entirely adequate, but would the flapping and fluttering create drag more than a rigid surface?

You know the fabric has to be filled, right? Stronger? Probably. Does it need to be? If so then I probably wouldn't be considering that airplane in the first place. Traditional fabric does not "flap and flutter" if applied properly, and the matrix to make the CF rigid is not weightless.

Carbon fiber is an excellent material in applications that are designed to take advantage of it. When it's used like "black aluminum" or in this case "black ceconite" it loses much of its advantage.

Nauga,
and a box full of dull rotary knives

 

[jimhorner]

It could be lighter, depending on how thin you can get the fabric. Probably stronger, maybe last longer in the sun. Dont get me wrong, traditional fabric is entirely adequate, but would the flapping and fluttering create drag more than a rigid surface?

Flapping and fluttering? No, not really. I've got around 1220 + hours in airplanes with fabric covered control surfaces (and only about 230+ in metal planes), and I've never seen my fabric "flapping and fluttering". I was trueing out at about 205 mph in the photo below. No flapping and fluttering here.

BTW, the fabric and paint job are 36 years old on this plane.

 

[moparrob66]

Great shot! I have seen videos of other wings with obvious movement of the fabric surface. I dont thing they were doing 200+ either. Not flapping like a flag, but definitely a distinct, fluttering that I found to be slightly off-putting.

 

[Bell206]

It could be lighter, depending on how thin you can get the fabric. Probably stronger, maybe last longer in the sun. Dont get me wrong, traditional fabric is entirely adequate, but would the flapping and fluttering create drag more than a rigid surface?

Doubtful it would be lighter unless you made the entire control item out of CF. But simply replacing the fabric with CF no. As to the "flapping and fluttering" it depends on a number of things if it is actually an issue. In my experience fabric control surfaces are more than adequate for most applications until you get going faster like 250+ mph. Really don't see any advantage replacing fabric, but in replacing metal skins I could see a possible advantage provided you could attach the CF to the existing structure.

 

[moparrob66]

That would probably require or at least permit you to redesign the inner structure. As for it being a direct replacement for fabric, I agree that it would have little to no benefit.