wrote:

Howdy All,

Thanks for your thoutful replies. They seem to fall into three main ideas:

Thicker panels:
yeah. This will work, but for exterior fuselage panels, it would be
prohibitively heavy. I'll pass.

Building in some kind of "upset":
This will work. Breaks, as I described will make the panels stiffer. Another
poster suggested rolling in ridges that would stiffen the panel. These would
look kind of goofy, and have a small drag effect. I think I'll pass.

Spraying a urethane foam on the inside:
This will stiffen the panel and improve the noise level inside the aircraft.
It would require a fire rated foam such as "gator skin". Other are
available. I'm leaning this way.

Thanks to all,
tom pettit

Lean back the other way some, Tom.
You are about to fall off of something here...

Filling large cavities with foam may be great for boats,
but don't do it to a metal airplane.

The lightest mix you'll get will be at least 3 pounds per cubic foot,
minimum.
And you'll need to pull a light vacuum to get that repeatably.

The foam will also continue to expand long after the skin has bulged way
outta shape.

Better solutions:

Deeply curved panels an not so susceptible to oil canning by nature of
their shape.
But that's a preliminary design issue, not an add on.

Better support inside will help reduce skin wrinkling and noise.
Closer spaced ribs, a cleverly placed stringer here or there?

I think the correct answer is thicker skin.

Increasing skin thickness a few thousandths will make a stiffer panel at
a fraction
of the weight of extra structure - or a fifty emergency flotation.


Now, may I suggest you contact the original designer with this question?

Because something as simple sounding as increasing skin thickness can
have snowball
effects on light structures.

In my book, that's considered a bad thing.

Richard