Sealing the firewall

[mlwynn]

Hi all,

I am ready to rivet the firewall to the side skins and the flanges that hold the camlocs. The instructions say to use proseal. I have been looking at this and am a little unclear about where the proseal goes. I assume the issue is to be sure no gases or liquids get from the engine compartment into the cabin. Where the flanges are cut in the firewall, there are gaps that would certainly allow that. I wonder if there is an issue of moisture getting between the skins and the firewall.

So, my options include:
1, riveting it all together and then running a bead of proseal around the inside to seal up the gaps.
2. pry the skin away from the firewall and try to run a bead in there. I looked at this and it would be pretty challenging.
3. Put proseal between all the layers including the skin, the spacers and the camloc flanges.

I am a little unclear on what would be the best approach without going into overkill mode. The instructions are not very clear. Thoughts?

Michael Wynn
RV 8 FWF
San Ramon, CA

[fast_flyer]

I added the proseal between the skin and the firewall. put the proseal in a suringe it makes it easier and less of a mess.

[larryj]

Vans also sells a high-temp glue/sealer for this application. The purpose is to bond the skin to the firewall with this stuff and run a small bead to effectively seal the engine compartment from the cockpit. I'm sure Proseal works fine but I would imagine this high-temp stuff would add just that little bit of time in the case of a bad day.

[Transporter]

Flamemaster CS-1900 is a MILSPEC (Mil-S-38249 Type I) firewall sealant; Vans isn't mail ordering it anymore due to HAZMAT hassles...but it's available and is the right stuff to use.

Do a Google search and you should find a source close to home/one that will ship to you. It comes packaged in pint can sets (with hardener) and in smaller Semco-compatible cartridges (as shown in Vans catalog).

It's a bit harder to work than regular Proseal; not quite as sticky, very stiff (tends to form a bead that you'll need to mash down), and the texture is a bit grainy. Cures in about the same amount of time.

Mike

[RVbySDI]

Originally Posted by mlwynn

I am a little unclear on what would be the best approach without going into overkill mode. The instructions are not very clear. Thoughts?

I do not wish to hijack this thread but your post has got me thinking about my firewall build.

I am building a 9A where I see you are building an 8 so I am not sure if everything will be the same in the two builds but I do not recall seeing these instructions for using proseal on the firewall/skin mating area. It is completely likely I just overlooked these instructions in my documents. Can anyone tell me where specifically in the instructions for the 9A this is discussed?

I do not have the firewall completely riveted to the fuselage but I do have both side skins partially riveted without any proseal. If this is a necessity I am most likely going to have to drill out several rivets in order to get proseal in the seam. Unless it is determined that if I need the proseal, I could successfully run a bead on the seam "as is".

Any advice would be appreciated.

[mlwynn]

Regarding the directions, I am sorry for being late to reply. I have been off at work for a couple of days. I will try to sort out where in the instructions it says to seal it. If you look at your firewall/side skin junction, you can see some gaps where the firewall is flanged. There would obviously be leaks from the engine compartment to the cabin, so these definitely need to be sealed. I am pretty sure the instructions said proseal, but I can certainly see the advantage of using a high temp firewall sealer.

Michael Wynn
RV 8 FWF

[Transporter]

My plans also called for tank sealant.

I'm not comfortable using Proseal to seal the firewall since it's not designed for high temps.

I called tech support at Van's last year and they recommended the CS1900 firewall sealant (shown in Van's catalog). I bought a tube from them and used it to seal the upper fwd floor to the firewall. Went to buy more in Nov to do my side skins and was informed that Van's was no longer shipping due to HAZMAT restrictions.

The CS1900 does ship as HAZMAT, so expect to pay a HAZMAT fee, but it's available from a number of sources, including:

http://www.specialtyadhesives.com/flamemaster1.htmI

http://www.sealpakcoinc.com/

I ordered mine from Sealpak with good service.

Mike

[rwarre]

Does anyone use the Permatex Ultra high temp for this application?

[Transporter]

Check other threads on this topic, but firewall materials are supposed to withstand 2000 degrees F (for a limited time) under specified conditions.

The Permatex products I've seen are rated to much lower temps...like 700 degrees F or less.

It comes down to what safety margin you want on your firewall.

Mike

[longranger]

If we're talking about sealing the firewall to the side skins (per the first post), is there significant value added to using a sealant material with a significantly higher temp rating than the alumnium skin?