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Ram Air

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Greg McFarlane

Joined: 12 Apr 2012
Posts: 57
Location: Albany Western Australia

Posted: Wed Feb 05, 2014 1:52 am Post subject: Ram Air

8 Just FYI, could be of interest,  having a removable engine air intake has several advantages and is well worth the effort. The bottom cowl is easier to put on and take off because the intake is attached after the cowl is offered up and before cowl removal. Because the 3inch scat is more flexible than the baffle seal setup there is less strain on the fab box and the throttle body/carb'. With the better seal that can be achieved with the slide in fitting expect a modest increase in MP (the scat is left about inch and half longer so is compressed holding the entry into the fab firm but is still flexible). The draggy flat bit just above the standard air intake on the cowl can be fared around the extended "dolphin Nosed" removable intake so........more speed. Cheers from Western Australia.

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bwestfall

Joined: 22 Oct 2008
Posts: 131
Location: Portland, OR

Posted: Wed Feb 05, 2014 8:55 am Post subject: Ram Air

That's pretty slick.  Do you have any pictures of how you secure the forward

portion into the cowling snort?  I see a couple holes in your "adapter" did

you epoxy in some standoffs for screws?  The 3 bladed prop guys might really

like this approach.  Of course its fiberglass work so there's a solid month

of build time spent in the "layup, sand, layup, sand, cuss, redo, layup,

sand" loop!!



-Ben Westfall



--

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Greg McFarlane

Joined: 12 Apr 2012
Posts: 57
Location: Albany Western Australia

Posted: Thu Feb 06, 2014 2:04 am Post subject: Re: Ram Air

Thanks Ben, The Snorkel is held with three screws (one each side one under) into nut plates that are riveted onto three small pieces of ally. The wings of the nut plates are bent to conform with the bent ally pieces which are then epoxied and riveted into place. On my 6 I got away with only two screws but the 10 is somewhat larger. Cheers from Western Australia

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rv10free2fly(at)yahoo.com
Guest

Posted: Thu Feb 06, 2014 4:16 am Post subject: Ram Air

Greg



Many thanks. Does the scat tube inserted into the air filter fit permanently on the lower cowl and then does that scat tube slide into the air filter when the lower cowl is fitted?



If thus is the case, why is there a need for the front air scoop to be removable please?



Your air inlet looks much larger than the standard, how much extra manifold pressure gain due you anticipate?



Your modification appears to be a pseudo cold air induction.  Well done. 



Can I call you to discuss please?



Warm regards



Patrick



Tel: 08 8236 6808

Mob: 0418 850 156



 	  Quote: 	
		   On 6 Feb 2014, at 20:34, "Greg McFarlane" <grbcmcfarlane(at)gmail.com> wrote:

 

 

 

 Thanks Ben, The Snorkel is held with three screws (one each side one under) into nut plates that are riveted onto three small pieces of ally. The wings of the nut plates are bent to conform with the bent ally pieces which are then epoxied and riveted into place. On my 6 I got away with only two screws but the 10 is somewhat larger. Cheers from Western Australia

 

 

 

 

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woxofswa

Joined: 12 Aug 2008
Posts: 349
Location: AZ

Posted: Thu Feb 06, 2014 9:31 pm Post subject: Re: Ram Air

I'm not an engineer, but I recall reading about the development  of NACA vent designs about how a protrusion around an intake can cause a damming or even vacuum effect when not pointed directly into the airstream, (such as a slip or crosswind gust).  Not trying to be alarmist but I would at least run the concept by an expert.

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Myron Nelson
Mesa, AZ
Flew May 10 2014

rv10flyer

Joined: 25 Aug 2009
Posts: 364

Posted: Thu Feb 06, 2014 9:43 pm Post subject: Re: Ram Air

When the SCAT is compressed 1.5", does it leave an aerodynamically smooth bore? My stock lower cowl binds up more due to cooling air inlet ramp rubber seals and only leaving 1/8" between spinner/cowl. Engine intake seems to be the easier of the three difficult areas on mine during installation.

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Wayne G.

Greg McFarlane

Joined: 12 Apr 2012
Posts: 57
Location: Albany Western Australia

Posted: Fri Feb 07, 2014 4:02 am Post subject: Re: Ram Air

Patrick, the whole thing as pictured with the fab box comes out when the screws are removed, only modest increase in MP expect inch or two, flying aircraft when this mod has been done have had increase when compared before/after. Wayne, as you'd expect the scat when compressed is not nice and smooth as you'd like, but it works, it's the compression that makes everything nice and snug. Myron, NASA would certainly know all about stuff hanging out in the airstream, however this extension nicely fared I guess could be compared with the other tube we all rely on and have sticking out in the airstream..........the pitot. Cheers from Western Australia

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woxofswa

Joined: 12 Aug 2008
Posts: 349
Location: AZ

Posted: Fri Feb 07, 2014 7:54 am Post subject: Re: Ram Air

The air in a pitot tube is pressurized higher than ambient because the consumptive rate is restricted by design creating a reservoir supply of feed air.



Engine air intakes have consumption rates which often create a vacuum/venturi effect that is much more sensitive to flow interruption. 



Early turbojet designs with relative narrow diameters and long intake nacelles were susceptible to compressor stalls due to airflow interruption which is one reason why jets, even those with straight wings, are never intentionally slipped.



As jet engine design has progressed, the forward nacelle has shrunk relative to the fan diameter and the problem of compressor stalls has become less and less of an issue.



Just musings of a hobbiast.  I readily admit I could be totally out to lunch. An expert opinion is always wise when modifying designs. Build on.

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Myron Nelson
Mesa, AZ
Flew May 10 2014

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