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  #21  
Old 08-14-2018, 08:18 PM
Dustyone Dustyone is offline
 
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Carl were they the later large rings or the earlier small rings?

Would you mind sharing what size yours are.

Cheers,
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RV-10 #40597
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  #22  
Old 08-15-2018, 01:57 AM
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Janekom Janekom is offline
 
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@ Dan - sitting halfway around the world is not easy. Shipping is way too expensive to get from SA to you guys in USA.
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  #23  
Old 08-15-2018, 07:11 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by Dustyone View Post
Dan,The cowl inlets on the RV-10 have reverse airflow at the blade root. I have observed this on my own aircraft where my first baffle rubbers would actually lift backwards into the A/C serpentine belt.
So any transition for the plenum would need to address this problem.
The simplest is adding round inlets as far outboard on the cowl and slightly higher than centre as recommended by Sonja Englert (Cessna TTX engineer )
I am not afraid of tackling the cowl and transitions and realize that this is only part of the equation to reducing cooling drag.
Sounds familiar.





Quote:
So my question would be,what size inlet rings ?
We know the first Sam James rings were to small,and I do plan to throttle the exit later in the project,so do I just start with 6” rings and work from there?
There is no "perfect" size; any size covers an operating range. All the data says low Vi/Vo is superior, so when in doubt, go larger. Experimentally, six inches diameter seems to work well with the 390 and 540. The external diffusion (pressure rise in front of the inlet) is frictionless. The practical limit seems to be set by external drag, i.e. flow separation as the excess air flows from in front of the inlet, to outward and around the inlet....something like this:



The aero guys call it spillage, although I think that creates a mental picture of air entering the inlet, reversing, and somehow flowing back out again. Whatever it's called, the cowl needs to be well rounded in the region surrounding the inlet, and as the inlet moves further outboard, further upward, or grows in diameter, there is less and less real estate within the frontal area envelope for shapely external curvature.

For external shape I look at the best radial engine cowls. In a previous thread, Steve Smith suggested looking at good fanjet inlets. I have no idea if this is optimal:

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Last edited by DanH : 08-15-2018 at 07:15 AM.
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  #24  
Old 08-15-2018, 08:32 AM
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Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by Dustyone View Post
Carl were they the later large rings or the earlier small rings?

Would you mind sharing what size yours are.

Cheers,
These rings measure about 4 3/4” ID, but James list them at 4 5/8” ID. Here is the link: http://www.jamesaircraft.com/?page_id=11

Note the 14” spinner. While I understand Van’s desire to standardize across kits, the stock 13” spinner is, in my opinion, out of proportion on an RV-10.

Carl
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  #25  
Old 08-15-2018, 09:38 AM
Dustyone Dustyone is offline
 
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Hi Carl,

Well done for getting the James set up to work correctly with the small inlets.
All the reports I had read mentioned that with the small inlets they had had to except higher CHT's than they would of liked.
In the end,it was only after fitting the 6" rings that there problems were solved.
They also mentioned having to run Turbo Rail Injectors for stable LOP operation because of the higher Vi of the smaller inlets.

It does look good with the 14" spinner
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RV-10 #40597
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http://www.vansairforce.com/communit...d.php?t=140051
Airflow Systems Air-Con
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  #26  
Old 08-15-2018, 09:49 AM
Dustyone Dustyone is offline
 
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Default Challenge accepted !

Hi Dan,

Looks like me and the " Dremmel " are going to be getting back together again!

So before I contact James Aircraft for a set of 6" rings,does anyone have a set lying around they would part with?
I am in Calgary for another two weeks.

Dan, you mentioned a while back about a 2 channel digital Manometer. I have found several expensive ones,but I remember yours was well priced ?
Can you supply the link ?

Also, how close to the prop can the intakes go ? I have read that 1/2" clearance is the go ?

Thank you to all that contribute to this amazing hobby !
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RV-10 #40597
Dual SDS CPI
http://www.vansairforce.com/communit...d.php?t=140051
Airflow Systems Air-Con
http://www.vansairforce.com/communit...4&postcount=15
VH-XTE 500hrs +
Redcliffe,Brisbane
Australia
Photos : https://goo.gl/photos/zsfBeVofHMe4ze7i7
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  #27  
Old 08-15-2018, 10:07 AM
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Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by Dustyone View Post
Hi Carl,

Well done for getting the James set up to work correctly with the small inlets.
All the reports I had read mentioned that with the small inlets they had had to except higher CHT's than they would of liked.
In the end,it was only after fitting the 6" rings that there problems were solved.
They also mentioned having to run Turbo Rail Injectors for stable LOP operation because of the higher Vi of the smaller inlets.

It does look good with the 14" spinner
Have no clue on such reports. I run LOP 95% of the time. Cruise is 170+kts at 9.5-11.5 GPH depending on altitude. CHTs in cruise are below 380. I run a standard Van’s IO-540 but replaced 4 injector nozzles to get the GAMI spread down to 0.1GPH. At $26 a nozzle this is the cheapest thing you can do to make your engine a better performer.

Perhaps your reports are about an RV-10 with some fire breathing engine - or other issues.

There is no free lunch. A plenum enables you to get the most cooling for every pound mass of air coming in the engine. As such, you can reduce drag by reducing engine cooling air coming in. While the inlet rings have a roll in this, remember the cowl outlet is a big player. I did install louvers on the bottom of the cowl (not the Van’s stufff) to add some additional cooling.

Every element of my RV-10 was optimized for cruise efficiency. If you want an RV-10 to be a climb monster, installing a plenum no longer makes sense.

Carl
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  #28  
Old 08-15-2018, 01:02 PM
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DanH DanH is offline
 
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Ashley, you have air conditioning and a front governor? If I were you, I would take a real hard look at the Acclaim and TTx. Then I would think about how I might add glass structure inside the cowl for optimized flap sealing surfaces. I might even make some molded seals for perfect fit.
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Last edited by DanH : 08-15-2018 at 01:16 PM.
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  #29  
Old 08-15-2018, 01:08 PM
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DanH DanH is offline
 
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Ashley,
Cheap mamometer is single channel, from eBay, about $35. Send an email and I'll send a white paper.

I don't remember how close the prop gets on mine.
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Last edited by DanH : 08-15-2018 at 01:11 PM.
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  #30  
Old 08-15-2018, 01:50 PM
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DanH DanH is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
Every element of my RV-10 was optimized for cruise efficiency. If you want an RV-10 to be a climb monster, installing a plenum no longer makes sense.
A plenum lid is just a sealing device. The flight regime matters not at all; better sealing is always beneficial, regardless of how it is accomplished.

That said, better conversation of available dynamic pressure (largely an inlet function) and better sealing are most valuable in the low speed climb regime, where there isn't much dynamic pressure available, and power setting is high.
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