Proseal the firewall to fuse?

szicree · #1 10-29-2007, 05:09 PM

I don't remember if it was in the plans or not, but I know for sure I rivetted the firewall into the plane without proseal. The firewall itself was prosealed together though. Do the plans now indicate the need for sealant around the firewall? Do most planes have it? Do I need to drill this thing apart to glue it back in? Opinions?

N208ET · #2 10-29-2007, 05:24 PM

I just riveted the firewall to the subfloor, and I used high temp RTV, that was all I had around, no proseal. On my 8A, it called for only putting it over the 9 rivets around the cooling air ramp, this is to prevent any oil leaking under in that area from getting into the cockpit area. It seems like a good percaution to me, but I don't think I would go back and do it. You might try and putting a little bead of RTV right at the seam and work it in there with your finger a little bit, kind of like packing a bearing.

Brian Vickers · #3 10-29-2007, 06:16 PM

Steve,
I sealed the firewall unit itself but not the sides or bottom when installing it. I am more concerned about the joint between the forward removable skin and the flimsy stainless firewall (the arched part). There are small gaps here and there between the bent over tabs and the skin. I also have some small valleys between the bent over tabs. Some type of squishy, flame retardant material would be good to have there. It could be adhered to the removable skin. All my other joints are pretty tight; although I'm sure sealing during construction would probably have been the right thing to do. I'm not going to go back and drill out all those rivets. I too would be interested to know if the lack of sealant is a problem with the flying RV4 fleet.

Brian Vickers, RV4 finishing
Washington State

szicree · #4 10-29-2007, 06:39 PM

Brian,

I had the same concerns about that upper skin. I think I might mask off all but the forward most 5/8 inch of the skin, cover the firewall flange with something that won't stick to proseal, slather some proseal on the skin and screw it on to dry.

Captain Avgas · #5 10-29-2007, 07:14 PM

Quote:

Originally Posted by szicree

I don't remember if it was in the plans or not, but I know for sure I rivetted the firewall into the plane without proseal. The firewall itself was prosealed together though. Do the plans now indicate the need for sealant around the firewall? Do most planes have it? Do I need to drill this thing apart to glue it back in? Opinions?

To do the job properly the firewall should be sealed at all possible apertures including at the mating of the firewall to the fuselage skins. This serves 3 purposes. 1. It prevents flames and heat from entering the cabin (for a while at least) in the event of a fwf fire. 2. It prevents smoke from entering the cabin in the event of FWF fire. 3. It prevents carbon monoxide from entering the cabin in the event of an exhaust system leak.

It might be quite difficult to do this if the skins have already been rivetted on.

Incidentally proseal is NOT the sealant to use on the firewall. Despite the fact that it's used on fuel tanks it is quite combustible...and when it burns it gives off copious amounts of black smoke.

The trouble with many RV builders is that they start off using proseal to do their tanks and then proceed to use the stuff for every other possible sealant application.

In fact Vans sells the an appropriate sealant. It's called FlameMaster CS1900 Firewall Sealant. It can cope with a flash temperature of 2000 F. See

http://www.vansaircraft.com/cgi-bin/...product=cs1900

Captain_John · #6 10-29-2007, 08:06 PM

Quote:

Originally Posted by Captain Avgas

To do the job properly the firewall should be sealed at all possible apertures including at the mating of the firewall to the fuselage skins. This serves 3 purposes. 1. It prevents flames and heat from entering the cabin (for a while at least) in the event of a fwf fire. 2. It prevents smoke from entering the cabin in the event of FWF fire. 3. It prevents carbon monoxide from entering the cabin in the event of an exhaust system leak.

It might be quite difficult to do this if the skins have already been rivetted on.

Incidentally proseal is NOT the sealant to use on the firewall. Despite the fact that it's used on fuel tanks it is quite combustible...and when it burns it gives off copious amounts of black smoke.

The trouble with many RV builders is that they start off using proseal to do their tanks and then proceed to use the stuff for every other possible sealant application.

In fact Vans sells the an appropriate sealant. It's called FlameMaster CS1900 Firewall Sealant. It can cope with a flash temperature of 2000 F. See

http://www.vansaircraft.com/cgi-bin/...product=cs1900

Just did it!

The stuff is like TAR!

It came out well. I would do it again. Not bad really. Kinda expensive, but ya know...

Mix it with MEK to thin the consistency. It will aid in the "mix-ability" if you will.

CJ

RScott · #7 10-29-2007, 08:40 PM

Our local hardware store carries furnace sealant (or was it boiler sealant?) that is good to 2,000 deg. Some guys have used that on their airplanes.

Richard Scott
RV-9A Fuselage

szicree · #8 10-29-2007, 08:57 PM

Quote:

Originally Posted by Captain Avgas

Incidentally proseal is NOT the sealant to use on the firewall. Despite the fact that it's used on fuel tanks it is quite combustible...and when it burns it gives off copious amounts of black smoke.

The trouble with many RV builders is that they start off using proseal to do their tanks and then proceed to use the stuff for every other possible sealant application.

I just searched through my old plans and couldn't find where I got the idea that Proseal was for the firewall. I finally found it as the description accompanying one of the photographs in the construction manual. It says that the lap joint in the firewall should be sealed with tank sealant.

As for the side to firewall joint, I'm confident that I can squeeze a nice bead of the correct sealant along the joint from behind.

AntiGravity · #9 10-29-2007, 10:43 PM

Quote:

Originally Posted by Captain Avgas

Incidentally proseal is NOT the sealant to use on the firewall. Despite the fact that it's used on fuel tanks it is quite combustible...and when it burns it gives off copious amounts of black smoke.

The trouble with many RV builders is that they start off using proseal to do their tanks and then proceed to use the stuff for every other possible sealant application.

In fact Vans sells the an appropriate sealant. It's called FlameMaster CS1900 Firewall Sealant. It can cope with a flash temperature of 2000 F.

This could well be down to the fact that the instructions do not specify and many builders, myself included, simply don't know. In fact, the new RV-8 instructions actually state 'fuel tank sealant'. In my case, the bottom edges are prosealed, whereas the side flanges are firewall sealant; except I didn't take into account the 'grooves' in between the tabs so now I have holes! No worries, I'm gonna buy some more and run a bead up the inside corner and smooch it in there...