Firewall top cut

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Includes: Highlander, Escapade, Summit and SuperSTOL.

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Firewall top cut

Postby b1x4nqb » Sat Jan 05, 2008 11:24 pm

I was cutting my firewall plate today.  Book said to basically trace your boot cowl for the top cut but I was wondering at what height to trace it at.  In reference to the first vertical mounting tab off the side firewall, starting at the top and going down.....Where does your boot cowl sit in reference to this?  Or is there some other trick you guys lined up to?  I may be ahead of myself as I wasn't ready to fit the entire cowl yet so if I should wait for that than tell me.  I simply had my front jig off the plane and it was on saw horses temporarily and before putting it back on the jig I wanted to fit the firewall plate and cut it approprietly.

Some other news, a friend of mine about 3 hrs west of me received his 2nd Highlander today.  What a lucky guy to have 2 of them.  His name is Sam Peachy.  His plane is the Blue and White one in all the original photo's.  Another friend of mine through Sam, (Chris Marquette) is having JA build one for him and he said he should get his sometime later this month.  Chris lives about 1 hour Northwest of me.  Amazing how many are starting to pop up in places!  I like what someone else said earlier, let's get them flying in '08.  My goal is Fathers day.

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Postby Dave Krall CFII SEL SES » Sun Jan 06, 2008 12:01 am

In our case we wanted all the room possible for the largest engine so placed the boot cowl at highest point its edges would allow, then scribed onto firewall, which was short, so will rivet lap in some more stainless sheet.

Speaking of rubber material in aircraft, we did not like at all the meltable rubber seal material JA sent, so will replace firewall seal with high temp material and insulate with fire blanket from Aircraft Spruce. If there's a fire in the engine/cowl, I want it to stay there, not blow up over the top edge of the firewall, melted & burning into the cockpit. Same thing goes for the JA fuel lines, we threw theirs out and went with high temp, flexible braid milspec.
Last edited by Dave Krall CFII SEL SES on Sun Jan 06, 2008 9:19 pm, edited 1 time in total.
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Postby stede52 » Sun Jan 06, 2008 2:28 am

Paul, personally I won't cut the firewall until you have the cowl and boot cowl fitted. Once everything is fitted and aligned correctly to the prop hub then trim the firewall to the shape of the boot cowl.  Just a word of advise, when fitting the cowl make sure your exhaust is also installed.  It's also easiest to fit the the cowl and boot cowl prior to fabric. Like Dave said the firewall is slightly short on top and adding an addition section of firewall to the top is your choice.

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Postby scubarider » Sun Jan 06, 2008 9:58 am

I placed the top boot cowl in place.  Put the firewall to the bottom of the frame.  Traced the boot cowl shape on the top of the the firewall and cut it out.  Worked fine.  I did use the rubber on top and just used rivets.  
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Postby b1x4nqb » Sun Jan 06, 2008 1:27 pm

Thanks guys.  I am waiting for a new cowling with more material on the back end for the airbox.  It should arrive sometime this month and once it does, I'll go ahead and fit everything up and then cut the firewall.

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Fire wall cut

Postby Lynng » Tue Jan 08, 2008 8:11 am


The boot cowl should overlap the firewall by about an inch so don't cut it back like my "helper did.  You can cut the firewall in place if you have a good set of snips or a air snip.  I cut mine about 1/2 to 3/4 short of the boot cowl and riveted the rubber baffling to the top edge.  You don't want the firewall to rub your boot cowl.  I hope that helps.


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