Paul,

I want to make a simple firewall to attach to the front of Seawind mount
frame. It is a non structural element for the cowl and only needs to be
strong enough to support the water reservoir, oil filter and pass
through connection.  I am thinking a thin sheet of stainless but what
can I use to back it up so it has some strength? 1/4" plywood comes to
mind but I am concerned about how long it will last with a hot flame on
the engine side.  Of course it could be argued that the FRP cowling will
be burning as well.


Doug in Japan

If it has thin stainless on both sides it won't burn. It needs air to
burn. I think it will turn to charcoal if the heat is high enough. The
best bet for a low density fire proof core may be the ceramic foam stuff
they use on the space shuttle. It is probably real expensive.

The XB70 had brazed SS honeycomb panels.

Paul Lamar

--
Doug,
How about forming beads to add support?   You can form with a brake or use
the "caveman" method - make punch out of a piece of 1/4 x 3 flatbar, round
the sides and ends on the punch end. Then cut a groove in a piece of wood
for the punch to go into plus a little clearance. On a sturdy bench, clamp
two pieces of flat bar/wood on each side of where you are going to bead to
reduce distortion and make a straight bead, and start hammerin'. Don't force
it, just use a bigger hammer.  :D  Sheet metal shops do this with CNC
equipment.
Dan F


--
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The Rutan airplanes initially had sheet aluminum over FiberFrax and
then plywood.  Rutan later changed the aluminum to stainless.

FiberFrax is a ceramic fiber matrix.  Aircraft Spruce sells it:

http://www.aircraftspruce.com/catalog/appages/fiberfrax.php

It's not terribly expensive.

For non structural applications I would be tempted to try heavy
titanium (or stainless) foil.  I've found that on ebay.

The FiberFrax needs mechanical support and protection from being fuel
or oil soaked.

It's probably obvious but, Fiberfrax doesn't work as fire protection
if it's incorporated into a composite structure where it's saturated
with epoxy/resin.  Almost all epoxy burns at a very low temperature.

Whatever material (metal) is being used to protect the Fiberfrax needs
to be robustly connected to to the backing material by a mechanical
means.  A fairly sparse matrix of stainless screws or pop rivets would
be fine.  Aluminum rivets can burn/melt at a relatively low
temperature.

A lot of small airplanes are built with galvanized steel or stainless
as the firewall.  Galvanized steel is cheap.  Exposing galvanized
metal to fire can release zinc fumes which can give you flu like
symptoms for a few days.

Finally, there are ablative/intumescent paints available that swell up
to form a protective barrier when exposed to heat/fire.  Ocean 9788 is
one of these.


Regards,

Matt-

Also,

This looks like an interesting product:

http://www.aircraftextras.com/Contego.htm

I'd want to do a bit of independent testing to make myself happy, but
it sounds cool (no pun intended).


Matt-