Javron - Firewall

[Scott A]

On the Piper Drawing 12365 'Firewall Assembly' it shows four 'reinforcement' patches Part number 10792-3.


I'm not seeing them in any of my parts. I will add it to my ask Jay list but if someone has already checked into it or knows something more.

Also, it probably doesn't matter with a blank firewall but it looks like the stiffener beads bump out on the forward side of firewall correct? I have seen a few cub images with them on the inside but looks like most are bumped out to the front (and cross-section A-A looks like it means forward)

I thought it made more sense to have them pointing back so the flange would rest flat against the firewall when riveting - but that is moot since the top and bottom are on opposite sides of the boot cowl flange anyway.

[Scott A]

..hmmm, well okay the reinforcement are not shown in the cowl assembly drawing 12381

[tempdoug]

engine cowl U channel L bracket reinforcement. are they with your U channels L brackets? pipers were made out of 3 x 1 1/2 inch pieces.

[Scott A]

I just checked the U channel bag before seeing this, not there. Thanks for the response.

What material where Pipers made from, I don't see that called out in the drawing?

I just found in Bill's thread he made up his own, it looks like stainless firewall material but not sure.

engine cowl U channel L bracket reinforcement. are they with your U channels L brackets? pipers were made out of 3 x 1 1/2 inch pieces.

[tempdoug]

this old firewall that i have piper used the same turnplate steel as the firewall or whatever you call the metal for those, .025 thick. i made mine but dont remember what i used for thickness? i remember priming and painting them before riviting them on. 2 rivits out from the edge aways to hold them on and 2 rivets when fastening the firewall to the bootcowl. i will have to try and find the name of the sealer i used, its still holding up great after 25 years.

[tempdoug]

are a lot of the holes drilled in your firewall?

[Scott A]

No, none other than the engine mount holes. Probably thinking what I was - could use the scrap from cutting cabin airbox hole etc. although not sure would be enough. But maybe not where you were going with that.
If they are supposed to be included Jay will send some - just too late to call him. And not holding me up yet.
Thanks again for the response.

are a lot of the holes drilled in your firewall?

[tempdoug]

scott i have a old 150hp piper firewall about 20 ft from my desk hanging in the garage if you need a measurement, wont be around all the time but if i can i will give a measurement if needed. good theres no holes you can do it your way.

[fishhook]

Just built up an Atlee firewall and 3 piece bootcowl, no sheet metal doubler, the doubler inside the fuselage is extended to catch both bolts for the cowl attach angles. Atlees newer ones are the stock thickness, there older ones were .100 or .125 thickness and have much more rigidity. All the atlee ones I see done do not have the sheet metal doublers on the drawings, and they all work great.

[fishhook]

Photo of bootcowl on fuselage is a .020 bottom skin 2024t3 with the newer atlee inside brackets (bottom cowl support), photo of bootcowl not installed is a mid 2000s atlee bootcowl that never got installed (showing thicker inside brackets they used to do). Last photo the cad plated piece is the cowl supports that came with my javron stuff, I went with the atlee brackets as they are heavier duty. Top skin on my bootcowl is .032 2024t3, and the top support is rigid as a rock, bottom one has a little bit more give but still way more rigid than a stock one. I decided against using the sheet metal doublers as nobody I know has ever done those, and they can be added later if need be (albeit not ideal).

[supercub83a]

My Javron kit did come with all of those brackets so it is something Jay produces. They had the correct angles and size but I had to drill the holes in them


Sent from my iPhone using SuperCub.Org

[phdigger123]

On the Piper Drawing 12365 'Firewall Assembly' it shows four 'reinforcement' patches Part number 10792-3.


I'm not seeing them in any of my parts. I will add it to my ask Jay list but if someone has already checked into it or knows something more.

Also, it probably doesn't matter with a blank firewall but it looks like the stiffener beads bump out on the forward side of firewall correct? I have seen a few cub images with them on the inside but looks like most are bumped out to the front (and cross-section A-A looks like it means forward)

I thought it made more sense to have them pointing back so the flange would rest flat against the firewall when riveting - but that is moot since the top and bottom are on opposite sides of the boot cowl flange anyway.

Sam, Jay told me they were not needed because his firewall is stainless and Pipers was galvanized. I made some doublers from .045 5052 aluminum and riveted in place as the drawing you posted shows.

[skywagon8a]

On the Piper Drawing 12365 'Firewall Assembly' it shows four 'reinforcement' patches Part number 10792-3.

..hmmm, well okay the reinforcement are not shown in the cowl assembly drawing 12381

Sam, Jay told me they were not needed because his firewall is stainless and Pipers was galvanized. I made some doublers from .045 5052 aluminum and riveted in place as the drawing you posted shows.

Let's address why on one drawing they are there and the other drawing they are not. Why are they addressed at all? What is happening in these four corners of the firewall? Not shown on these two drawings is the flange which attaches the firewall to the wraparound in both cases. The engine cowl has four channels which support the entire cowl. These four channels are screwed/bolted through the firewall at these four corners. These four channels exert a flexing load on these four corners. On drawing 12365 the screws attach to the firewall where all the loads must be distributed into the firewall. On drawing 12381 the screws attach through the firewall to L brackets which further distribute their loads to the wraparound cowl. On drawing 12365 the loads stop at the firewall, with the concentration of the loads at each screw hole. Over time the firewall will crack due to the movement stresses of the cowl, regardless of the type of thin material the firewall is made of. By installing the half moon doubler the firewall is strengthened against that flexing retarding any tendency for crack propagation. On the 12381 drawing those loads do not stop at the firewall, they are transferred to the wraparound.

If you use the L brackets to the boot cowl you can eliminate the half moon. If you do not use the L bracket, you should use the half moon.

I have the utmost respect for the knowledge and abilities of Jay. Thin stainless steel can crack under these circumstances if not properly supported.

[Scott A]

Thanks all!

This is what I have. I would like the inner angle better (part 12840) if it had the longer flange and picked up both 10-32 Machine screw holes on the 12379 cowl channel support bracket instead of just the one.

[fishhook]

Make up some that are longer or give Atlee dodge a call, they have ones with a joggle in them to account for the firewall flange thickness. Ask for undrilled ones. Personally I would make up my own thicker ones, the newer thinner ones I just installed seemed to flex whereas the older thick ones had zero give at all. Catching both screws helps a lot, I originally tried the 1 screw bracket and it had a bit of give to it for sure.

[Scott A]

Thanks, I like the idea of the joggle and picking up both screws.

Make up some that are longer or give Atlee dodge a call, they have ones with a joggle in them to account for the firewall flange thickness. Ask for undrilled ones. Personally I would make up my own thicker ones, the newer thinner ones I just installed seemed to flex whereas the older thick ones had zero give at all. Catching both screws helps a lot, I originally tried the 1 screw bracket and it had a bit of give to it for sure.