Use of fabric in rudder & elevators ( DC-3 DC-4 etc)
 

I can understand that for weight reasons small GA a/c used fabric covered contol surfaces but not sure at all why fabric was still used on much bigger planes from the DC-3 thru DC-7 and even the Super Connie.

Any suggestions?

flutter
 

I think it was mainly because of flutter concerns caused by oil-canning in metal structures.

b377

Saw a Stinson owner wind up and slug his Rudder. He asked if he could clobber my Skylane the same way. I said, "No".

Balance determines flutter. Not the covering.

Fabric saves weight. It also enables fairly straightforward removal to inspect the underlying structure.

Although Guppy often supplies rather long-winded answers, this time...he is absolutely correct.
How do I (personally) know?
My Dad was engineering project manager at Douglas...(deputy manager, on the DC4), manager engineering on the DC6 and DC7.
In addition, fabric covering often allowed for a more robust assembly.
Even the Stratocruiser (a quite fast airplanre, for its time) employed fabic, in several locations.

411 by chance is your old man still around? I have questions
on the Deisel 9 - 30's tailplane and why it was designed so
(elev/elev tabs/stab). In my time no one could effectivley
answer why.

The 727 had a diferent arrangement that was quite strateforward.

As it happens, I've covered and maintained those structures.

Covering is the easy part. Cleaning off the old fabric and dope...there's a job for someone with no reason left to live...

Sadly, no.:sad:

The B-29 also had fabric control surfaces. Any chance they are less prone to icing? I had a Bellanca Cruisair with fabric fuselage and tail for 20 years, and never had an icing event, thankfully.

Fabric coverings were from the era of expensive materials and cheap labor. The way it's going now, however...

Amazing that kite material continued to be used on advanced piston planes like the b377 when they could have borrowed some ideas from de Havilland and used "kitchen foil" thick Al like they did on the Comet 1. :o

In one of the last chapters of Gann's "Fate is the Hunter" he tells of his lucky escape from a potential DC-4 disaster (due to fate taking a hand rather than airmanship) when on ground inspection they discovered a hinge problem on the elevator of his plane while another DC-4 had recently come to grief due to the same problem (1950s). Gann called it 'elevator porting' which is when an elevator breaks or loosens from a hinge causing it to put the airplane firmly in a nose down attitude without a chance for recovery. (The nasty incident was witnessed from another plane behind the unlucky DC4)

Are you guys familiar with this problem?

I digress though, so back to topic on control surface fabric use.

I think that it was primarily to save weight and reduce drag.

You see corrugated aluminum controls on Ford Trimotors, Junkers, Cessnas from the 1940s on, and even the WACO UPF-7 (an example of the reverse: fabric covered wings, metal ailerons), but these are all relatively slow aircraft.

Smooth fabric is more aerodynamic than corrugated aluminum with universal head rivets sticking out and the steel frame has better strength to weight. I think better construction techniques and more power finally allowed the designers to switch to metal control surfaces.

Weight saving, smoothness, ease of inspection, strength ... these are all plausible reasons - but which one is the winner?

One thought that comes to mind is the control effort required from the pilot via the 'mandrolic' pulley system ? But dynamic balancing would have remedied this so perhaps not the reason.

So why continue to use use fabric when the rest of the skin became metal... hmm.

Also Dornier Do 27, 28, 128, and 228, but not 328, 528, and 728.

DC-3 and DC-4 Fabric Elevators etc...
 

I'm a former DC-3 and DC-4 captain for Millardair in Toronto and I saw this question about fabric control services and thought I'd help you out.

The elevators were heavy and lacked hydraulic assist thereby making control inputs heavy. In the DC-4 as an example, the fabric elevator combined
with a counter weight spring aided the pilot in pulling back on the yoke.

The DC-4/6/7 and Constellations all had fabric covered rudders. During heavy maintenance checks a fabric tester was used to determine if it had deteriorated. The dope that had been applied would dry and crack but a "rejuvenator" could be applied that softened it and extended its life. Aside from that we had very little trouble with fabric covering, at least in my experience.
Still, it did happen. On a very windy night on the ramp one of our mechanics had to re-lamp a DC-6B red anti-collision light which, Douglas in its wisdom, had placed atop the vertical fin. We had a very tall "fly ladder" mounted on a four-wheeled base. A fixed ladder went up at an angle to the midpoint and a second fly ladder was extended above it being pulled up by a rope. When extended to the height of a '6B fin (or even worst a '7C) it was very flexible. The aircraft was moving a lot too being buffeted by frigid gusts. The inevitable happened, I think the end of the ladder contacted the rudder and a hole was torn in the fabric.
It was going to require a "high-speed" patch which meant sewing and doping. It then transpired that none of us, all A&P licensed mechanics, had touched a needle since school and getting licensed. Anyway it was too cold for doping and it went off to the base hangar and attention by a fabric shop mechanic.
Some of the radar Constellations had their center rudder which lived aft of the radome on top, fixed (deactivated) in place in place and metal covered. Apparently the two outboard fins and rudders were sufficient.
Fabric covered controls were definitely lighter than metal covered ones. The higher speed of turbine aircraft ended their use on transports.

Having recovered a few DC3 flying control surfaces as an apprentice I can tell you recovering a fabric controls was a low skill level than metalwork !

Along with construction techniques, aluminum alloys and heat treating techniques have improved over time. No doubt that was a factor in changing the fabric vs. aluminum calculus.