VansAirForceForums  
Home > VansAirForceForums

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

- Today's Posts | Insert Pics


Go Back   VAF Forums > Model Specific > RV-8/8A
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #21  
Old 09-19-2011, 04:57 PM
CMW CMW is offline
 
Join Date: Mar 2007
Location: Livermore, CA
Posts: 165
Default Thanks

Thanks for all the nice comments. I'll try and answer some of the questions:

Quote:
The only potential gotcha I see is the amount of air you're stealing at the back of #3. I think you'll find your oil is going to run pretty cool with that monster cooler. I have Van's standard cooler with a 4" SCAT in the same location as you do, and a 2" scat for cabin heat is taken off of my #4 baffle.
I agree and I can't tell you how many time I went back and forth on what to do here, but I finally just decided to build it and deal with it during testing. I figured I can always choke down the flow to the oil cooler if I need to but adding flow would be more difficult. The cabin heat scat can also be moved to behind #4 if necessary. I'll have to see how the cabin heat works also, since I have mufflers and am running them in series. More experimenting.

Quote:
Did you lay up the top from the top of the cowl?

What cooler did you use and did you make the plenum for the oil cooler?

The only thing I see that could be an issue is the inlets being aluminum and mating with the glass. The engine moves and the cowl is fixed. Any insulator between the cowl and inlets?
Yes, I used the top of the cowl as a form to lay up the top of the plenum.

I used some non-reinforced silicone rubber to join the cowl rings to the diffuser. I've posted a link to a video below that shows how much movement the system can accept. I hope its enough.

Quote:
I'd suggest cutting back the length of the aluminum intake diffusers and increasing the length of the silicone rubber. The engine case torque reaction is significant, and adding length to the silicone tube will reduce load on the aluminum parts. My intakes are glass reinforced urethane. Your unreinforced silicone should give a bit more, a plus.

Same or related issue...make sure you have at least 1/2" cowl clearance at those upper front corners. Your parallel valve heads are easier to package in this regard so it may not be an issue. My angle valve head offers less clearance to work with in the RV8 cowl. I thought it had enough clearance but it still bumps on start-up or rough running.
Dan, first off I want to say that a lot of this design was inspired by if not directly copied from your plenum. I've got a long ways to go to get to your level of craftsmanship and knowledge but it's something to strive for. Thanks for raising the bar.

You may be right about cutting the diffusers back some but right now I think the system should allow sufficient movement of the engine relative to the cowl. The non-reinforced silicone stretches fairly easily. How long it will last is another issue that I'll have to keep a close eye on. Here's a link to a video showing how much movement the system will accept easily.

http://www.youtube.com/watch?v=7WIbDXnEhjU

I have 1/2" of clearance all the way around between the plenum and the upper cowl.

Quote:
Do you have also a 4" Scat on the exit side of the oil cooler.In the affirmative how far down did you carry the scat tube: between the exhaust pipe ?
No, right now the oil cooler has no exhaust ducting. If I find I need to choke the flow to the cooler, I'll probably make something that will allow me to choke the exhaust rather than the inlet.

Quote:
Which oil cooler did you use, can you post a couple pictures that show that setup better please?
I have an Aero Classics 8000074 nine row cooler. I'll try and post some in a couple of days.

And, NO! I don't want to go into business making these. This was a ton of extra work. About 3/4 the way into this I was kicking myself for not just building to plans but the first things I made were the cowl rings so I was kind of committed.

Thanks again for the comments,

Chris
__________________
Chris
RV-8 Wings
Reply With Quote
  #22  
Old 09-20-2011, 08:28 AM
DanH's Avatar
DanH DanH is online now
 
Join Date: Oct 2005
Location: 08A
Posts: 7,801
Default

Quote:
Originally Posted by CMW View Post
.....I think the system should allow sufficient movement of the engine relative to the cowl.
The video is illustrative...I think you're right.

So far the fabric-reinforced ducts are holding up fine, but I'll be interested in lifespan for your unreinforced silicone version....internal pressure and membrane tension will be similar, about 100-110 lbs/sq ft at 200 knots down low. Your very low modulus approach is superior if the reinforcement isn't required, as the glass transmits more load to the baffle tin.

Overall your design is much more substantial. I experienced some fatigue cracking in the formed flange (1) and at the front 1/4-20 baffle screw (2).



There is no structure at all where the urethane ducts meet the glass plenum lid, only a clamp strip with three nutplates. The loads at (1) and (2) are large, much like the anchor points of a rope bridge.



The flange is highly formed and the material choice (3003) was too soft, so I'll need to replace it. I've already revised (2) for higher local strength.

You've sidestepped all that with significant structure above and around the inlets passages. Flip side will be turbulence behind the section change in the plenum entry if inlet velocity is high (high Vi/Vo). Big deal? I dunno With work that pretty I sure hope you grab some pressure measurements in due course.

Speaking of pretty work, fess up...how did you machine those inlet rings?
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #23  
Old 09-20-2011, 10:41 AM
CMW CMW is offline
 
Join Date: Mar 2007
Location: Livermore, CA
Posts: 165
Default

Quote:
Originally Posted by DanH View Post
.......I sure hope you grab some pressure measurements in due course.

Speaking of pretty work, fess up...how did you machine those inlet rings?
Thanks Dan, If I ever finish I will certainly take some pressure measurements. That's what it's all about, education.

The inlet rings I machined on the mill you can see in the background of one of the shots. I've converted it to CNC. It took a little layout work in CAD to get the shape close but then it was pretty easy.

Chris
__________________
Chris
RV-8 Wings
Reply With Quote
  #24  
Old 12-31-2016, 02:29 PM
Chkaharyer99 Chkaharyer99 is offline
 
Join Date: Oct 2011
Location: Pilot Hill, CA
Posts: 817
Default "My Attempt at a Plenum"

Chris,

I have an RV-8 and was researching plenum ideas. I'm mostly interested in ideas like yours that used the stock Vans cowl inlets.

It's been a few years since youve built it. Hows it working? Anything you'd do differently?

Charlie
Chkaharyer99@yahoo.com



Quote:
Originally Posted by CMW View Post
Here's a few shots of my plenum. This has taken forever. I hope it works well.













__________________
Charlie
RV-8
Reply With Quote
  #25  
Old 01-01-2017, 04:28 AM
dbuds2's Avatar
dbuds2 dbuds2 is offline
 
Join Date: Nov 2005
Location: Palm Beach Gardens, Fl
Posts: 378
Default Love more photos

Do you have a build site with individual part photos?

And how do you remove the top to service plugs/injectors?
__________________
Bud Smith, RV-8, ECI IOX360 , Dual PMags, Dynon SkyView, Whirlwind 200GA, IFR and N88ZP has "slipped the surly bonds of earth".
Reply With Quote
  #26  
Old 01-31-2017, 01:13 PM
elev666 elev666 is offline
 
Join Date: Feb 2013
Location: Kincardine Ont,Can
Posts: 76
Default

What up piece of art , nice work Chris and I'll be watching for your disclosure posts on how you got the fibreglass so nice !

Some guys just seam to set the bar too **** high !
__________________
C-GARV RV 6
1946 C85 J3
RV 7 project /IO-360 -200
Dues paid 08/ 17
Reply With Quote
  #27  
Old 01-31-2017, 02:15 PM
sblack sblack is offline
 
Join Date: Dec 2009
Location: Montreal
Posts: 1,267
Default

I'm doing my baffling now so this is really timely for me and I have a stock Vans cowling. I was going to put sheet diffusers to the cowl inlets but now I see where that would likely not have worked.

I like the way the inlet rings have a bead in them for rigidity. I am going to steal that - a good project for my bead roller.

The big difference with mine (or at least the one I have in my head) is that I am doing a split plenum, so the left inlet will feed the left bank of cylinders and the right will feed the right. I think it will be simpler in the long run. But experience may prove otherwise. Thank you for posting this.
__________________
Scott Black
RV 4, with an engine...and other stuff
VAF dues 2016
Reply With Quote
  #28  
Old 01-31-2017, 02:31 PM
Bavafa Bavafa is offline
 
Join Date: Oct 2007
Location: Sacramento, CA
Posts: 2,413
Default

Quote:
Originally Posted by sblack View Post
The big difference with mine (or at least the one I have in my head) is that I am doing a split plenum, so the left inlet will feed the left bank of cylinders and the right will feed the right. I think it will be simpler in the long run. But experience may prove otherwise. Thank you for posting this.
A friend of mine had done it this way on his RV7 and end up removing the middle part to make it all one plenum due to hot temp issues. Once he removed the middle part, his temps were much better.
__________________
Mehrdad
RV7A - IO360M1B - SOLD
Dues paid
Reply With Quote
  #29  
Old 01-31-2017, 06:59 PM
Sixgun Sixgun is offline
 
Join Date: Dec 2016
Location: Ct.
Posts: 19
Default

Quote:
Originally Posted by RV8R999 View Post
Chris - honestly I don't think you can say "attempt" at all. You solution looks absolutely superb. Very nice.
Real nice !!...
Reply With Quote
  #30  
Old 05-20-2018, 02:47 PM
cdeerinck's Avatar
cdeerinck cdeerinck is offline
 
Join Date: Mar 2014
Location: San Marcos, CA
Posts: 306
Default Oil access

Quote:
Originally Posted by CMW View Post
Here's a few shots of my plenum. This has taken forever. I hope it works well.
Chris - How do you handle access to your Oil dipstick and cap?
__________________
~Chuck

DG-800S Sailplane
QB RV-8 -- Working on the canopy and wiring
84CX Reserved
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 09:26 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.