Fabric control surfaces

[Clayton Magnet]

Fabric control surfaces is still a thing with relatively modern aircraft as well. I worked at a company that operated a couple Dornier 228's, and they had fabric covered elevators. Lighter weight, and easier to balance.
A pain to repair though, as we had to order the special fabric from Switzerland.

 

[MIflyer]

I think there were others in the WWI era, but I do not remember which airframes.

The Waco biplanes of the 1920's had it as well, but they were ground adjustable. When you think about it, if you have not yet invented Bowden cables, using trim tabs on the control surfaces is a real challenge.

 

[special ed]

Just a bit of derail, in late 60s or early 70s a friend and fellow model builder was hired by Ozark airlines because he had fabric ability and was an A & E. Ozark's DC-3s, of course, had fabric covered ailerons, elevators and rudders. It appears Ozark's own mechanics didn't do it.

 

[MikeMeech]

The Waco biplanes of the 1920's had it as well, but they were ground adjustable. When you think about it, if you have not yet invented Bowden cables, using trim tabs on the control surfaces is a real challenge.

Hi
"not yet invented Bowden cables" Not sure about the meaning of this statement? They were invented in the late 19th C, and first used on bicycles in the early 1900s. Very visibly in use during WW1 in aeroplanes like the SE.5a, to operate the trigger on the top wing Lewis gun.

Mike

 

[pinehilljoe]

In With Wings Like Eagles, Michael Korda wrote that Sydney Camm chose to cover much of the Hurricane with fabric to allow ground crews familiar with fabric maintenance and repair to transition to the Hurricane for maintenance.

Excerpt from the book:
WITH WINGS LIKE EAGLES. Copyright © 2009 by Success Research Corporation.

 

[MiTasol]

I think it was the combo of lightweight, relatively small surfaces able to be worked upon if need be and also the fact that it was already a well known and proven capability vs all metal skinning.

The F4U fabric covered wing aft of the front spar sort of punches a hole in the relatively small surfaces reason. PBY also but that was a prewar design.

I suspect @ThomasP may be correct as well as being light, using well known processes, easy to repair for skin damage and I suspect that the making of the curved shapes used on most rudders and elevators (and outboard ends of many ailerons) in alloy was a challenge at the time.

 

[MiTasol]

Servo tabs. They were only in their infancy in ww2 but the aerodynamics and mechanics of them were known.

 

[MIflyer]

Camm said that he was in a great hurry to get the Hurricane out the door and so did not spend the time to make the wing thinner. The Typhoon still had a pretty thick wing but with the Tempest he finally made a thin one.

 

[HP52]

I would say the main reason for using fabric on control surfaces has to do with them having to be statically balanced around their hinge axis.

This is usually accomplished by placing lead forward of the hinge line to counteract the weight of the aileron behind it. And since the hinge line is usually so far forward, if you add weight on the aileron surface as such by replacing the fabric with metal skins, then the short moment of arm means you have to add a lot of extra lead.

So it's not the added weight of the metal skinning as such that is the problem, but rather the increased amount of balancing lead required to get it back in balance around the hinge line.

I was told by an ex-RAAF fitter that depleted uranium was used in mass-balance aileron weights - can't verify it

 

[z42]

I was told by an ex-RAAF fitter that depleted uranium was used in mass-balance aileron weights - can't verify it

Maybe today. Certainly not during WWII.

 

[Holtzauge]

I was told by an ex-RAAF fitter that depleted uranium was used in mass-balance aileron weights - can't verify it

That's interesting. Did not know that this may have been the case. But if they did, it makes sense given that uranium is almost twice as dense as lead. I only knew about the use of it as kinetic dart ammunition for tanks. But if you have the stuff laying around anyway, why not make good use of it?

 

[MiTasol]

I was told by an ex-RAAF fitter that depleted uranium was used in mass-balance aileron weights - can't verify it

That is correct and has been the case since at least the mid 50's.

Coatings and handling procedures have changed significantly over the years.

 

[MIflyer]

The USAF's BOMARC SAM was made out of thoriated magnesium and the whole thing was slightly radioactive.

 

[SaparotRob]

Cool!

 

[PAT303]

I was told by an ex-RAAF fitter that depleted uranium was used in mass-balance aileron weights - can't verify it

Doesn't the 747 have DU in the tail for weight balance?

 

[MikeMeech]

Hi
When I was working on Westland Wessex helicopters during 1978-81, DU was used as weight balance in the tips of the main rotor blades. I believe this was quite common in helicopters of the period.

Mike

 

[fannum]

A big concern is the need to static balance to avoid flutter. Early WWII fighters often had to stiffen wings due to torsional flexing, resulting in wing failures in dives. Same issue with empennage, and note that controls were usually statically and aerodynamically balanced, so weight was an issue.
Also, many early helicopters had wooden main rotors with fabric covering behind spruce spars.
Obviously, there are ease of field repair advantages.
A related worst case are these images of B-25 tail feathers singed in the aftermath of a 3/18/44 Mt. Vesuvius eruption. The 340th Bomb Group was located at the Pompeii airfield, and the B-25s lost fabric and plexiglass canopies to the superheated ash. The weight of the heavy ash on aft wing section, fuselage and tail turned the Mitchells into tail draggers until swept clean.
Apparently, after checks and maintenance, all bombers returned to service.

 

[HP52]

In With Wings Like Eagles, Michael Korda wrote that Sydney Camm chose to cover much of the Hurricane with fabric to allow ground crews familiar with fabric maintenance and repair to transition to the Hurricane for maintenance.

Doped patches in the RAF were de rigour at least to the end of WW2 for fast/patched to get aircraft in the air. Used to have a photo in the family album of a 463 Lanc that had ammunition belts hanging out of a hole fwd of the entry door. The old Man said, the airframe guys would have dressed the panel as best they could and then tacked the metal to bits of kerosene packing case before dope-ing over it to be ready for the next day. Bill Purdy who was also on 463 was with us on Anzac Day
Geoff (Horrible-Hamdemon)

 

[fannum]

Doped patches in the RAF were de rigour at least to the end of WW2 for fast/patched to get aircraft in the air.

With the pressure to get as many aircraft "UP" to meet a mission schedule, this was a widespread practice. This was common for all services in ALL combatant countries, especially for flak splinter holes that didn't affect structural members, just punctures in metal skin.
Holes would be drilled or filed round to prevent stress rising cracks, and fabric would be attached with various glues ... often dope, but the aluminum would usually be roughened with harsh grit sandpaper or files, and by Vietnam, we used some more aggressive two component epoxy/resin/RTV type glues.
Also, expedient metal patches were thrown on using blind rivets or Parker Kalon self tapping screws, sometimes with glues and overlaid doped fabric.
I saw a P2V that had the front of the lower radome deteriorate (salt and sand abrasion) at a remote Mediterranean airfield, and get patched with thin tin covered with ubiquitous "200 mph" duct tape. It made it to the repair base, just fine.

 

[pinehilljoe]

With the pressure to get as many aircraft "UP" to meet a mission schedule, this was a widespread practice. This was common for all services in ALL combatant countries, especially for flak splinter holes that didn't affect structural members, just punctures in metal skin.
Holes would be drilled or filed round to prevent stress rising cracks, and fabric would be attached with various glues ... often dope, but the aluminum would usually be roughened with harsh grit sandpaper or files, and by Vietnam, we used some more aggressive two component epoxy/resin/RTV type glues.
Also, expedient metal patches were thrown on using blind rivets or Parker Kalon self tapping screws, sometimes with glues and overlaid doped fabric.
I saw a P2V that had the front of the lower radome deteriorate (salt and sand abrasion) at a remote Mediterranean airfield, and get patched with thin tin covered with ubiquitous "200 mph" duct tape. It made it to the repair base, just fine.

This reminds of me of when I was managing a satellite launch campaign in Xichang, China, 1995 when the US could launch from China. The satellite used an An-124 for the airlift in from the USA. When landing, the plane tore part of a wheel well cover. The load master asked if we hand aluminum tape, we didn't so they used duct tape to secure the tear, and off they went after unloading.