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[98.95.183.188]) by mx.google.com with ESMTPS id n20sm7233739anl.19.2012.12.15.09.07.27 (version=SSLv3 cipher=OTHER); Sat, 15 Dec 2012 09:07:28 -0800 (PST) Message-ID: <50CCAE4E.7020007@gmail.com> Date: Sat, 15 Dec 2012 11:07:26 -0600 From: Charlie England User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: Duct Fabrication References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------030300010400010300030502" This is a multi-part message in MIME format. --------------030300010400010300030502 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Disclaimer: I'm a long way from even running the engine. I tried to copy (at least in spirit) Tracy's install, as well. Renesis in RV-7. For fit (& financial) reasons, I used a Civic racing rad that has a more or less square face & is a downflow design instead of a crossflow 2 pass like the Scirocco style that Tracy used. It's around 400 cu in volume. One thing I intend to try is to use an exit duct. Because of this, my duct is on the engine side of the rad (Tracy dumps his exit air toward the engine). The layout in my cowl (I wanted as straight a shot as possible into the wedge) & the desire for an exit duct forced that change for my installation. I tried to use the formulas & guidance from the K&W book as a starting point, but discovered that some of the stuff about wedges doesn't seem to match 'real world' application. Tracy saw my 1st draft & warned that it wasn't thin enough at the back of the wedge, & he was right. I used canned foam to re-shape the wedge to thin it out at the back. Once I determine that the internal shape actually works, I'll glass over the canned foam. I also used a turning vane in the duct to get more even air distribution through the core (thanks to Al Gietzen for that tip). The vane was needed because the inlet height is well above the center-line of the rad. I did try to use the K&W streamline diffuser concept to transition from the round inlet to the somewhat larger area of the entrance to the 'wedge'. I used clear packing tape as a release on the flatter areas, and cheap electrical tape on the highly curved areas. Tape works fine as a release, but any texture on the form will get reproduced in your part. I had to do a lot of work to smooth the interior of the duct because of the ridges formed by wrapping the tape around the form. It's a lot like painting; if you do a lot of prep work, there will be a lot less finish (repair) work on the duct. Shots showing the core I made, & the resulting duct with turning vane are on Photobucket at > http://s1155.beta.photobucket.com/user/rv7charlie/library/radiator%20duct Video of the airflow is at > http://www.youtube.com/watch?v=D0mUJdzzrG0 Charlie On 12/15/2012 08:20 AM, Tracy wrote: > I used a male mold made of foam. Use the good stuff, not the closed cell styrene or the canned foam which is hard to work with. After shaped, I 'paint' it with drywall compound sand it smooth then cover with vinyl tape or coat with molten paraffin as mold release. > > 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 the leaf blower flow test method showed pretty good distribution with higher flow near the back (should have been even thinner there). Fixed that with a bit of ridge vent material (porous coarse fiber stuff) stuffed in the back section. 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 wrote: > >> Hi Guys >> >> I am about to reinstall the Renesis engine in the Glasair SII and create the ducts to the exchangers. >> I plan to copy as closely as possible Tracy's 20B setup. >> Questions: >> >> 1. What is a good process? Shaping foam, sounds good. So how do you then seal it before applying glass/epoxy? >> >> 2. Tracy, why is your diffuser not a simple wedge? Do you believe you are getting a more even pressure to the top and bottom? Have you ever measured your pressure distribution? >> >> Thanks >> >> Steve Izett >> >> >> >> -- >> Homepage: http://www.flyrotary.com/ >> Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html --------------030300010400010300030502 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit
Disclaimer: I'm a long way from even running the engine.

I tried to copy (at least in spirit) Tracy's install, as well. Renesis in RV-7. For fit (& financial) reasons, I used a Civic racing rad that has a more or less square face & is a downflow design instead of a crossflow 2 pass like the Scirocco style that Tracy used. It's around 400 cu in volume. One thing I intend to try is to use an exit duct. Because of this, my duct is on the engine side of the rad (Tracy dumps his exit air toward the engine). The layout in my cowl (I wanted as straight a shot as possible into the wedge) & the desire for an exit duct forced that change for my installation.

I tried to use the formulas & guidance from the K&W book as a starting point, but discovered that some of the stuff about wedges doesn't seem to match 'real world' application. Tracy saw my 1st draft & warned that it wasn't thin enough at the back of the wedge, & he was right. I used canned foam to re-shape the wedge to thin it out at the back. Once I determine that the internal shape actually works, I'll glass over the canned foam. I also used a turning vane in the duct to get more even air distribution through the core (thanks to Al Gietzen for that tip). The vane was needed because the inlet height is well above the center-line of the rad. I did try to use the K&W streamline diffuser concept to transition from the round inlet to the somewhat larger area of the entrance to the 'wedge'.

I used clear packing tape as a release on the flatter areas, and cheap electrical tape on the highly curved areas. Tape works fine as a release, but any texture on the form will get reproduced in your part. I had to do a lot of work to smooth the interior of the duct because of the ridges formed by wrapping the tape around the form. It's a lot like painting; if you do a lot of prep work, there will be a lot less finish (repair) work on the duct.

Shots showing the core I made, & the resulting duct with turning vane are on Photobucket at  
http://s1155.beta.photobucket.com/user/rv7charlie/library/radiator%20duct

Video of the airflow is at
http://www.youtube.com/watch?v=D0mUJdzzrG0

Charlie


On 12/15/2012 08:20 AM, Tracy wrote:
I used a male mold made of foam.  Use the good stuff, not the closed cell styrene or the canned foam which is hard to work with.   After shaped, I 'paint' it with drywall compound sand it smooth then cover with vinyl tape or coat with molten paraffin as mold release.  

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 the leaf blower flow test method showed pretty good distribution with higher flow near the back (should have been even thinner there).  Fixed that with a bit of ridge vent material  (porous coarse fiber stuff) stuffed in the back section.  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

I am about to reinstall the Renesis engine in the Glasair SII and create the ducts to the exchangers.
I plan to copy as closely as possible Tracy's 20B setup.
Questions:

1. What is a good process? Shaping foam, sounds good. So how do you then seal it before applying glass/epoxy? 

2. Tracy, why is your diffuser not a simple wedge? Do you believe you are getting a more even pressure to the top and bottom? Have you ever measured your pressure distribution?

Thanks

Steve Izett



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