I second Marks comments on overdoing heat shielding - its only really a cowl 
issue in very close proximity to the exhaust.

But I would suggest a focus on keeping some critical in cowl components cool.  
Specifically-  electronics and fuel delivery.   I’ve cooked a mag and an 
alternator in my Osprey. Similarly, vapor lock is not uncommon in hot weather. 
I like fire sleeve for fuel lines and simple heat shields and a bit of air can 
keep components cool enough to stay reliable. 

There is fair debate on methods to keep heat in the exhaust.  Many (including 
the RV folks) say don’t do anything.   Increasing the temp of the exhaust metal 
(by wrapping) can increase likelihood of cracking.  Internal ceramic coating 
(such as Jet-Hot) makes re-welding the inevitable cracks impossible - so you 
have to replace the entire system.   However, my concerns over  in cowl temps 
with my Osprey persuaded me to use Jet-Hot coating.  I’ve had ~700hrs service 
since with minor flaking and significant in cowl temp reduction.  But I do know 
I’ll have to throw the exhaust out when it cracks.   The Osprey is very tightly 
cowled.  The KR is a little better, and I’m leaning to wrapping the exhaust 
(but no silicone).  

Picture of Osprey Cowl:


> On Jul 25, 2018, at 9:00 AM, krnet-requ...@list.krnet.org wrote:
> Message: 6
> Date: Wed, 25 Jul 2018 05:29:51 -0700
> From: <m...@n56ml.com <mailto:m...@n56ml.com>>
> To: "KRnet" <krnet@list.krnet.org <mailto:krnet@list.krnet.org>>
> Subject: Re: KR> Heat shielding the cowl
> Message-ID:
> <20180725052951.d04b1abb1c854b54fd3150a99c6879d4.5a2570f229....@email04.godaddy.com
> <mailto:20180725052951.d04b1abb1c854b54fd3150a99c6879d4.5a2570f229....@email04.godaddy.com>>
> Content-Type: text/plain; charset="utf-8"
> This is for all builders, not necessarily just the original poster.  One
> word of caution on all of this wonderful heat shield information....it's
> not weightless.  I took about 7 pounds of heat shielding out of N891JF's
> cowling (the KR2).  The total cowling weight started out at 21 pounds
> (compared to N56ML's total weight of four pounds), and about a third of
> it was heat shielding. On top of the fiberglass was silicone, then
> fiberfrax, more silicone, and then some thin aluminum blanket.  It was
> quite an ordeal to strip it all out, but it made it quite a bit lighter.
> And you know what?  Not even the paint is discolored where it was all
> removed!  It's also worth mentioning that the N891JF's cowling is very
> thick, with way too many layers of fiberglass, which makes it even more
> insulated, but also makes it downright brittle.  If I didn't have so
> many other irons in the fire, I'd pull a mold off that cowling and make
> a CF one that weighs a fraction as much.  Maybe after I retire!
> By contrast, N56ML's (KR2S) cowling is two layers of carbon fiber (with
> an extra "X" reinforcement for the relatively flat top....just like the
> hood of your car), and weighs 4 pounds total, including the aluminum
> attachment hinges.  No heat shielding, super thin, flexible when
> disassembled, fairly oblivious to exhaust pipe heat.  I have had exhaust
> components in direct contact with it, and all it does is burn the epoxy
> out of the matrix....the CF is still there (although rather anemic from
> a strength standpoint).  My point is that by providing a little bit of
> clearance, and maybe a small bit of heat shielding strategically placed
> only where it is really needed, is all you need.  Don't overdo it.  I'd
> bet serious money that Ken Rand had no such thing in his KR1!
> There are many safety measures that are very prudent in our airplanes. 
> I'm not sure that heat shielding the cowling is one of those...
> Mark Langford, Huntsville, AL
> ML "at" N56ML.com <http://n56ml.com/>
> www.N56ML.com <http://www.n56ml.com/>

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