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Dave Weisgerber
Joined: 27 Jul 2007
Posts: 1
Location: Ionia Michigan
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 Posted: Fri Jul 27, 2007 12:05 pm Post subject: Sam James Cowl air inlet rings |
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I have a Sam James cowl on my RV6. I am looking for a set of air inlet rings that are smaller inside diameter, but the same outside diameter so I can just put them in and not have to change the front of my cowl. I think I can get by with less cooling air because I only have an O-320 and the cylinder head temps. are low. I saw Dick Martin at the Airventure Cup Race and I think he had some different size rings for his, I am just trying to buy some rings to experiment with. If Dick reads this or anybody knows where Dick got them could you please let me know. My E-mail address is dweisgerber(at)homeworkswildblue.com
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Dave Weisgerber |
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gmcjetpilot
Joined: 04 Nov 2006
Posts: 170
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| Posted: Sat Jul 28, 2007 12:51 pm Post subject: Sam James Cowl air inlet rings |
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Get out the fiberglass. I have done this with a stock cowl and seen it done on a Jame cowl. You basically glass inside the existing rings or just make new inserts. You can make it temporary and changeable as you suggest. Be sure if you glass in the original ring to use parting wax. The inserts can secure with tape or tape. This way you can experiment with new shapes and areas. You could make something up with hi-dens foam and a carving knife. Than coat it foam with some resin. Just pop it in and fly. The down side is the more crude you make it the less change you may see with speed, but cooling changes should be valid. Speed wise, your change will be there but small. Consider cowl exit changes as well (cowl flap). For cooling fly on a 100F day in climb to really give the new inlet area the acid test.
You can do as you said you saw on the RV-8, and make a more a trumpet or bell shape inlet with a smaller throat.
http://img235.imageshack.us/img235/1166/image030aa6.jpg
The cowl profile is based around the major diameter of the insert, so you may end up with a wider lip around the inlet to make the throat smaller. The shape of the lip is important so play with that as well. Consider going out towards the prop, but with at least say 3/16" clearance?
How to do fiberglass and make the shapes, can't help. Consider just using foam inserts and than coating them with resin. Just keep that external lip in mind, don't make it too blunt, and internally when you go from inlet ring insert to the soft duct you may have a big lip or jump.
Here are two picture from a talent RV-6 tinker. He basically made his own inserts all together. The idea is as you desire, to reduce the inlet area.
http://img241.imageshack.us/img241/9087/dsc07624jw6.jpg
http://img241.imageshack.us/img241/3407/dsc07635qn8.jpg
The transition from the smaller diameter insert to the soft duct may trip turbulence. From the pics above you see that he flairs it back out to meet the soft ducts ID. You don't want a big area change. Consider a new soft duct couple. Buy an old wet suit and use different parts of the legs or arms to get the right diameter.
You may pick up speed but it will be small, but every little bit helps. Plan on doing some good BEFORE flights and after flight test. Also one flight will not be enough. You should do many flights and average the speeds. The scatter or error in our flight test can be over a MPH, so the change may be in that scatter. You did not say what OT and CHT you are getting but if you are running cold this will be of benefit. My O-320 RV-4 always ran cool and it took a lot of work with a smaller oil cooler and inlet mods to get the temps in the OT=180F and CHT=low/mid 300's.
(Do you have the spread sheet for averaging speeds on three legs on constant track?) As I said consider the exit of the cowl along with the inlet changes? (like a cowl flap).
Write me direct if you want to experiment, we can talk. George RV-7
>Subject: Sam James Cowl air inlet rings
| Quote: | From: "Dave Weisgerber" <dweisgerber(at)homeworkswildblue.com>
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| Quote: | I have a Sam James cowl on my RV6. I am looking for a set of air inlet
>rings that are smaller inside diameter, but the same outside diameter so I can
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>just put them in and not have to change the front of my cowl. I think I can get
| Quote: | by with less cooling air because I only have an O-320 and the cylinder
head temps.
|
[quote][b]
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ptrotter
Joined: 10 Jan 2006
Posts: 28
Location: Westchester County, NY
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| Posted: Sun Jul 29, 2007 12:47 pm Post subject: Sam James Cowl air inlet rings |
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Dave,
I believe that Dick Martin makes these and may sell them. I expect that
somebody here knows his contact info.
Paul
Dave Weisgerber wrote:
| Quote: |
I have a Sam James cowl on my RV6. I am looking for a set of air inlet rings that are smaller inside diameter, but the same outside diameter so I can just put them in and not have to change the front of my cowl. I think I can get by with less cooling air because I only have an O-320 and the cylinder head temps. are low. I saw Dick Martin at the Airventure Cup Race and I think he had some different size rings for his, I am just trying to buy some rings to experiment with. If Dick reads this or anybody knows where Dick got them could you please let me know. My E-mail address is dweisgerber(at)homeworkswildblue.com
--------
Dave Weisgerber
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=125932#125932
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Paul Trotter
RV-8 82080 Fuselage Kit
N801PT (reserved) |
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