VAF Forums

VAF Forums (https://vansairforce.net/community/index.php)
-   RV General Discussion/News (https://vansairforce.net/community/forumdisplay.php?f=2)
-   -   Forming aluminum for a cooling outlet fairing (https://vansairforce.net/community/showthread.php?t=83719)

hydroguy2 03-13-2012 03:09 PM

KHLN 131953Z 20022G33KT 10SM SCT100 14/M07 A2932 RMK AO2 PK WND 22034/1941 SLP938 T01441072

OK no test flying today for me.

But I'm getting the cowl outlet rough draft snipped out.


Something I'm wondering about is: My 4 pipe exhaust really fills the JamesCowl outlet in comparison to the larger Vans cowl. AND they hang below the cowl outlet and are uneven with each other. (also offcenter) So I'm contemplating cutting off about 1/2" of the exhaust pipes at an angle to get them out of the slipstream a bit. Anyone else modify the pipes to get them out of the breeze?

Bruce 03-13-2012 04:28 PM

Brian,
I have the 4 pipes but they are straight.
There is a pic on the Exit cowl thread.
Maybe that will help.

I think if you shorten them you will have
more turbulence on the bottom though.

My .05

hydroguy2 03-13-2012 05:12 PM

Thanks Bruce. Your pipe set up is different. I see you "A" model folks are dealing with a clogged outlet also, but looks like you have a lot more exit area.

I am trying to streamline the exit flow So thought trimming the pipes a bit might actually help and be less turbulence.

Here's a pic looking aft, you can see the PAX side hangs down more than the pilot side. Thought I could even them out a touch.

gereed75 03-13-2012 05:57 PM

Nice progress Brian

I am not sure what to think of the whole pipe thing. Mine angle and hang down significantly and I am considering shortening them and turning them back directly aft with a little angle connector Larry Veterman makes. Not sure yet. Using the oil drop method, I do see a small stagnation point directly aft and above my pipes. Oh well, can't get it all perfect.

I think that if the fairing and other cleanups work to smooth your exit airflow, you will find that your exit area will be more than adequate even with the four pipes. I am trying to think now of an efficient way to reduce my exit area without chopping up the cowl. See the next post.

Its always something

Mike S 03-13-2012 06:25 PM

Quote:

Originally Posted by gereed75 (Post 639372)
I am trying to think now of an efficient way to reduce my exit area without chopping up the cowl.

Airfoil shaped (flat on top, curved on bottom) after fairing on the bottom of the fuse-----fit it between the sides of your cowl extensions, depending on size and how far forward, you get to choke off the outlet, but at the same time give it a smooth ramp for the air to follow. Coanda stuff that Paul Lipps talked about, I seem to remember him posting a drawing of something like this.

You can also research stuff like it on the CAFE website------as I recall the guy who runs the CAFE foundation did this to a Mooney with good results. http://cafefoundation.org/v2/aboutca...oard.php#brien

More info for you techie types here. http://cafefoundation.org/v2/tech_en...greduction.php

RV8R999 03-13-2012 06:32 PM

Quote:

Originally Posted by gereed75 (Post 639372)
Nice progress Brian

I am trying to think now of an efficient way to reduce my exit area without chopping up the cowl.

Its always something

as per the discussion on Exit Drag


Mike S 03-13-2012 06:52 PM

More reading
 
http://cafefoundation.org/v2/pdf_caf...localflow2.pdf

Look at drawing C, it is depicting the airfoil ramp I was discussing a couple posts ago.

Ron Lee 03-13-2012 08:05 PM

Quote:

Originally Posted by Mike S (Post 639382)
http://cafefoundation.org/v2/pdf_caf...localflow2.pdf

Look at drawing C, it is depicting the airfoil ramp I was discussing a couple posts ago.

I can't access that file

gereed75 03-13-2012 08:07 PM

Mike, Can you get me to that link another way?? I'm getting the "forbidden 403" message. Thanks

Ken, That is looking good. I was thinking about something similar for my two pipe exit. I think I would like to tuck the pipes up and out of the airstream first. Then squeeze down the exit area from the bottom as you have done. ... and I thought I was done with this project!! It continues to morph.

hydroguy2 03-13-2012 08:55 PM

Well, got home from cowl fab work and the phone ran. Mike the hangarhome owner next door called and said the small old hangar is collapsing. I jumped in my truck to run out and check for other damage. the backwall blew out and sheared the posts. When it flipped over, part of the hangar went over the top to the next taxiway, landing next to my hangar. Debris field is about 300yards, but zero damage to anything else. Luckily no plane was in this hangar.

told you it was too windy to do testing. 60/60day. 60 degrees and 60mph


All times are GMT -6. The time now is 07:47 AM.