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Subject: Re: [FlyRotary] Duct Fabrication
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From: Tracy <rwstracy@gmail.com>
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Date: Sat, 15 Dec 2012 09:20:22 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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I used a male mold made of foam.  Use the good stuff, not the closed cell st=
yrene or the canned foam which is hard to work with.   After shaped, I 'pain=
t' it with drywall compound sand it smooth then cover with vinyl tape or coa=
t with molten paraffin as mold release. =20

The rad duct was shaped based on my imagined airflow within the duct.  It is=
 compound curves everywhere, not a simple wedge.   Much thinner at the edges=
 than in center for example.  Is it better than a wedge?  Don't know, but th=
e leaf blower flow test method showed pretty good distribution with higher f=
low near the back (should have been even thinner there).  Fixed that with a b=
it of ridge vent material  (porous coarse fiber stuff) stuffed in the back s=
ection.  Not the best solution there but I've not had water cooling problems=
 so good enough.

Tracy

Sent from my iPad

On Dec 14, 2012, at 7:33 PM, Stephen Izett <steveizett@me.com> wrote:

> Hi Guys
>=20
> I am about to reinstall the Renesis engine in the Glasair SII and create t=
he ducts to the exchangers.
> I plan to copy as closely as possible Tracy's 20B setup.
> Questions:
>=20
> 1. What is a good process? Shaping foam, sounds good. So how do you then s=
eal it before applying glass/epoxy?=20
>=20
> 2. Tracy, why is your diffuser not a simple wedge? Do you believe you are g=
etting a more even pressure to the top and bottom? Have you ever measured yo=
ur pressure distribution?
>=20
> Thanks
>=20
> Steve Izett
>=20
>=20
>=20
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