VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #11  
Old 01-02-2017, 04:13 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,596
Default

Quote:
Originally Posted by DanH View Post
With all due respect Carl, that's nonsense.

Again, a plenum lid is just a sealing device. There is no "design point" speed, and it does not control how much mass passes through the system. It only ensures none of the mass can bypass the engine and thus fail to pick up heat. As such, a plenum lid benefits every part of the performance envelope, but low velocity climb most of all, as that's when the least total pressure is available. When starting with very little, there is none to waste.
I should have been clearer. My design target was high efficiency cruise, not rate of climb competition. With that target, total engine cooling drag can be reduced (as compared to a stock cowl) while still providing adequate cooling. With a good plenum, you can do more engine cooling drag reduction and still retain adequate cooling at your target operational envelope as compared to leaky baffles.

If rate of climb is the target, open up to let as much air in and out as you can. The addition of a plenum would help at the margins.

Carl
Reply With Quote
  #12  
Old 01-02-2017, 06:05 PM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 9,500
Default

Quote:
Originally Posted by Carl Froehlich View Post
I should have been clearer. My design target was high efficiency cruise, not rate of climb competition. With that target, total engine cooling drag can be reduced (as compared to a stock cowl) while still providing adequate cooling. With a good plenum, you can do more engine cooling drag reduction and still retain adequate cooling at your target operational envelope as compared to leaky baffles.

If rate of climb is the target, open up to let as much air in and out as you can. The addition of a plenum would help at the margins.Carl
There is no target speed or margins. Leakage reduction is a benefit across the entire operating range.

Clarify this one for us please:

Quote:
Originally Posted by Carl Froehlich View Post
If you are not using the James Cowl there is little to be gained with a plenum.
Seems be be at odds with your signature line:

Quote:
RV-8 in progress (will use stock cowl and homemade plenum)
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #13  
Old 01-02-2017, 06:13 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,596
Default

Yep - stock cowl for the new RV-8 project and a homebrew plenum. While I know there will be no big cruise gain with the stock cowl, I'm hopeful a few tweaks of the stock cowl will gain something for me.

If not for the required prop spacer for the James RV-8 cowl I would use it.

Carl
Reply With Quote
  #14  
Old 01-02-2017, 10:42 PM
Janekom's Avatar
Janekom Janekom is offline
 
Join Date: Jan 2006
Location: South Africa
Posts: 840
Default

Hi John, you have asked about the rvbits plenum. I always say that if you can fabricate well fitting rubber seals, you do not need a plenum lid. But most battle a bit with this. With my plenum you build the cooling baffles as per the plans up to the point where you do the final trim and rubber seals. Then add the plenum lid. The guidelines can be found at rvbits.com
__________________
Jan Hanekom
South Africa
Approved Person nr 325
http://www.rvbits.com
RV10 - ZU-XOX - (Flying)
RV7A - ZU-JRV - (Flying)
RV10 - ZU-JVR - (Written off)
RV7 - ZU-LOL - (Flying)
RV10 - ZU-RVI - (Flying)
RV7A - ZU-MER (Bought back)
RV7A - ZU-JAD (Sold Flying)
Dues paid for 2020 WITH A SMILE
Reply With Quote
  #15  
Old 01-03-2017, 06:30 AM
johngoodman's Avatar
johngoodman johngoodman is offline
 
Join Date: Feb 2006
Location: Peachtree City, Georgia
Posts: 440
Default

Thanks, Jan. I've pretty well figured it out. I finally figured out how the oil door is handled. The real reason I thought about it is the problems with putting the top cowling on without folding a rubber baffle the wrong way.
John
__________________
John Goodman - 40572
First flight was 25 June, 2011
N711JG
Reply With Quote
  #16  
Old 01-04-2017, 08:34 PM
civengpe civengpe is offline
 
Join Date: Nov 2010
Location: Houston, Texas
Posts: 212
Default

Quote:
Originally Posted by johngoodman View Post
Thanks, Jan. I've pretty well figured it out. I finally figured out how the oil door is handled. The real reason I thought about it is the problems with putting the top cowling on without folding a rubber baffle the wrong way.
John
John,
I have the RVBits Plenum and have had no cooling issues to date. The oil door seal is accomplished by simply installing a seal from McMaster Carr around the perimeter of the plenum oil door cutout. I believe the instructions even list the part number.

I don't have it handy, but it is something along these lines: https://www.mcmaster.com/#catalog/122/3516/=15ru6jt

Shannon
__________________
Shannon
RV-10
Flying September 2015
Reply With Quote
  #17  
Old 01-05-2017, 05:02 AM
Plummit's Avatar
Plummit Plummit is offline
 
Join Date: Apr 2010
Location: Covid Country-SoCal
Posts: 1,081
Default

One thing I didn't see mentioned is the additional engine service issues caused by a plenum. With a stock cowl sans plenum, you remove the top cowl and the engine is right there. With a plenum, at least on my airplane, you still have to remove a boat-load of small screws to get access to the top of the engine.

It's part of the "no free lunch" deal. Also, it's tough to seal the dip-stick tube so that it doesn't leak air. If I was building I wouldn't waste my time with a plenum.

-Marc
__________________
RV-10
N814RV
2020 Donation Made
Reply With Quote
  #18  
Old 01-05-2017, 12:17 PM
civengpe civengpe is offline
 
Join Date: Nov 2010
Location: Houston, Texas
Posts: 212
Default

I'm not sure if my plenum leaks air around the dipstick tube cut out or not, but I don't have any cooling issues either. I am based out of Houston and have flown in temps over 100f with no issues what so ever. Isn't that the real goal?

I will admit that it does take a while to get direct access to the engine verse just taking off the cowl. The reality is that I haven't had to do it that often since phase 1 anyways. Oil changes, condition inspection etc. It takes an extra 5 minutes to remove the plenum.

Shannon
__________________
Shannon
RV-10
Flying September 2015
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 02:26 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.