Firewall Integrity
 

I'm prompted to write this post after viewing some post on the Matronic's list about cutting holes in the firewall to pass an electrical connector. If you're a newbie and haven't yet carved your firewall into swiss cheese, I'd like to offer you a couple of suggestions.

First, maintaining the integrity of your firewall should be one of your primary safety concerns. I've visited many builder sites and I've seen some dubious things when it comes to this topic. In the rare event that you suffer an engine fire, seconds count and may make the difference between making a safe emergency landing or suffering other consequences. So think carefully before you drill any hole in that stainless.

The number one rule is to make sure that what ever you put in that hole, is at least as tolerant, or more tolerant, of heat and flames as the stainless steel you're replacing. That usually means putting stainless steel back in its place. The largest hole will likely be your cabin heat box. Make sure it is constructed of stainless steel and has a stainless steel flapper. There are aluminum ones floating around. They are unsafe. Don't use one. Van's used to sell both. I know they sell the stainless one.

When passing cables through your firewall, I am partial to the steel eyeball fittings. I know they are expensive at $30 a pop, but you only need three or four max. I like these units because they allow me to direct the cable in any direction, they don't come loose or unscrew, they look fine, and they are impervious to flame.

Finally, and the area where I've seen some real "creativity" is passing wires into the engine compartment. I try to drill as few holes as possible so I like to keep the engine wires into two bundles. One bundle contains all the noisy wires like alternator, starter, field, and magneto wires. The second bundle is for all the other wires like sensors, EFT, CHT, etc. I use the stainless firewall passthroughs sold by http://www.epm-avcorp.com/tubeseal.html. I put the noise bundle dowm low even with the crankcase split to facilitate running the starter and alternator wires forward. I put the the sensor bundle up high. These units are very good at sealing out fire and come with a tube of fire stop to apply in and around the wire bundle.

It's perfectly fine to use stainless steel grommet shells like Van sells as long as you cover the opening with some fire putty as a final step. I also choose to use steel bulkhead fittings for things like brakes, fuel, and hydraulic lines. They stand up better to the constant shaking of the hoses, although I suspect that there are many, many airplanes flying with aluminum fittings.

There are many ways to do the same thing. I'm not suggesting that my way is the only way or even the best way. I do think it's a safe way. If you have any doubt, consult with a mechanic friend or fellow builder.

Fire Putty?
 

Can someone tell me where to get some of this "fire putty"?
Thanks!

Aeroelectric firewall penetration notes
 

There's a guide for a recommended firewall penetration method on the Aeroelectric website. Here's the link:

http://www.aeroelectric.com/articles.../firewall.html

heater box
 

noted your comment about the aluminum heater box. vans sold me the aluminum one with the fwf kit. guess i have to toss out ANOTHER item from that very expensive sub kit.

firewall putty
 

vans sells some stuff called firewall sealant, MIGHT be the same stuff.

The folks at http://www.epm-avcorp.com/tubeseal.html worked with Bob to come up with a commercial, off the shelf, package for firewall penetration that Bob described in this article. That's not to say you can't roll your own.

BTW, I'm not affiliated with these guys in any way. I just like their product, it's complete, easy, lightweight, and delivers as advertised.

Also, I do not know of a source for homebuilders of fire stop putty, but I know it exists somewhere. A building buddy of mine was a AP/AI for United Airlines and he used this stuff on his RV-6.

3M makes a product which I think is equalivent to "fire Putty" You can find it to buy at

http://www.cableorganizer.com/3m-fir...ier-ic15wb.htm

I plan on using the 3M product to fill the gaps on the firewall recess hatch and plan on using http://www.epm-avcorp.com/tubeseal.html for my firewall penetration openings.

I just looked this stuff up and I don't think it is appropriate for the firewall. The maximum continuous operating temperature is only 120 degrees F. The area behind the engine will routinely see temperatures between 200 and 300 degrees F.

Fire Putty
 

I have always used the Red/Orange High temp Permatex stuff you get at the auto store. Good for 700F. It is called:

PERMATEX? ULTRA COPPER? Hi-Temp RTV Silicone

http://www.permatex.com/auto/autouh....&item_no=81878

The stuff sets nice, firm but flexible and sticks like crazy (like pro-seal but not as bad). :D Cheers G. :)

:mad: I agree the Home Improvement Fire Putty does NOT sound acceptable with a 120F limit temp? :eek:

Fire Putty
 

Home Depot sells it. Go to the 'caulk' aisle, and it is there. For whatever reason it is always on the top shelf, no matter what Home Depot I have been in. I cannot recall the names (they sell 2-3 brands) but it is labeled as 'Fire Barrier Caulk'. Being in the security business, when we wire apartments or any multi-level structure, fire codes dictate we seal every hole between floors with this barrier/caulk. After buying it for years at our distributors, we have found the same formula/product at Home Depot for half the price. It has been a few years since I have bought it, but I have seen it recently on the shelves when buying regular caulk products. It is around $8-9 per tube, if memory serves me.

Thanks,