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-


Gentleman,

Thank you for the fast and timely response.  Since my fire wall is
basically to hang things on, stainless with some vertical channels
punched in as Dan suggested should work nicely. I'll use the hydraulic
press down the road however:)  Backed up with some insulation it should
work well.  I haven't seen Fiberfax but one product I have used in my
company with good success is a ceramic board made here in Japan.  It is
about 2mm thick, lightweight and can be cut with a box cutter.

Matt, that coating product is similar to the one the racers use.  Latex,
and if I am not mistaken, latex is natural rubber right?

Engine fires in flight are going to be most likely caused by fuel or oil
leaks contacting hot mufflers. Injectors need to boxed and a safe drain
provided for any fuel leaks to be brought away from the hot zone.  See
Mistral's arrangement. For people using turbo chargers oil is brought
right to the source of the heat. Two possible leak area are the inlet
and outlet. Logic would suggest a thin stainless enclosure around this
entire hot zone with a fire sensor and fire suppression nozzle built in.

Unfortunately one design point I don't like about airplanes, and I'm
sure Bill Jepson will agree, is the air duct taking hot air from this
hot zone and blowing it into the cockpit.  Sure it makes a great heater
but in times of fire, even if it can be suppressed within a thirty
seconds, noxious fumes are going right down into the cockpit.

This gives new meaning to using a hot water heat exchanger and blower as
the cockpit heater.
It acts as another cooling source for the engine as well and can be
vented over board if not needed in the cockpit, or the blower simply
turned off.  Heat exchanger can be mounted on the cool side of the
firewall so only a few hoses pass through on the cool side of the engine.

For take-offs on those hot summer days, turn on the heater and roll down
the window:)
Driving across the Nevada desert in the summer of 1970 this was the
technique I used  to keep my car engine from overheating.

Doug in Japan