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From: "Al Gietzen" <ALVentures@cox.net>
To: "'Rotary motors in aircraft'" <flyrotary@lancaironline.net>
Subject:  Jet Hot Exhaust Coating
Date: Mon, 27 Jul 2009 23:03:03 -0800
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As I have posted on this list before; doing some relatively simple heat
transfer calculations will tell you that putting these coatings on the
outside surface of the exhaust can reduce the temps by less than 1%.
Coating the inside will make a larger difference initially because of =
the
lower emissivity; possible as much as 5%, but after some buildup of =
exhaust
products, the difference will be about the same as coating the outside.
Anyone telling you it will reduce the temp by 65% is blowing smoke, and
hasn't the faintest idea of reality.

The coatings make the exhaust look nice, and will inhibit corrosion on
carbon steel systems, especially on the inside; but on SS system they =
are
pretty much a waste of money.

Ok; it's just my opinion.

Al G

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Mike Wills
Sent: Monday, July 27, 2009 8:45 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Intake filter box & Jet Hot Exhaust Coating

My exhaust is coated in and out with a 2000 degree coating. Its holding =
up=20
OK, but I wouldnt rely on it to keep the heat off of nearby components. =
I=20
have a stainless heatshield around a large portion of the exhaust and I =
have

a self adhesive fiberglass heat shielding material applied in various =
places

like the inside of the cowl. In places not protected by the heatshield, =
the=20
adhesive has gotten hot enough to release. I also have a couple of =
painted=20
parts fairly close to the exhaust that have gotten hot enough for the =
paint=20
to burn.

Mike Wills
RV-4 N144MW
----- Original Message -----=20
From: "Ben Schneider" <plumberben@yahoo.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, July 27, 2009 4:54 AM
Subject: [FlyRotary] Intake filter box & Jet Hot Exhaust Coating


>
> Thanks for the kind words. Let me answer some of the questions. The =
intake

> filter box has a K&N filter inside, and a butterfly valve for ram air =
that

> bypasses through the center of the filter. It also has a spring loaded =

> door that would suck open in the event of the opening being plugged. =
That=20
> is why the odd shaped top.
>  The pictures of the exhaust are pretty old. In the one picture, the=20
> exhaust had not yet been sent to the coater. I guess I should also add =

> that the coating is not actually Jet Hot coating as I have been =
calling=20
> it, (common trade name) It was actually done by High Performance =
Coatings=20
> (www.hpcoatings.com) It is their equivalent to the Jet Hot. Supposed =
to be

> good up to 2000 degrees, and supposedly reduces surface temperatures =
as=20
> much as 65%. I am wondering if that is true or just sales propaganda?=20
> Guess I'll find out.
>   The muffler is an Aeroturbine muffler, all stainless, 2 1/2" inlet =
and=20
> outlet. Don't have any idea if it will blow apart, quite the thing, or =

> just increase drag. Yet another unknown. Ahh, the life of an=20
> experimenter....
>
> ;)
>
> Will be off line for a few days, headed to OSH. Hope to see some of =
you=20
> there.
>
> Ben
>
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:=20
> http://mail.lancaironline.net:81/lists/flyrotary/List.html
>=20


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