I like the cold beer best, then let all good ideas slip back into oblivion.
I just worked out a Yak with a customer. Some very simple disk attached to the firewall, and some sticky window foam in the cowl did the trick. A cardboard template was cut out in 5 minutes, and it sported both the baffle, and bent back tabs acted as the air guide jacket alongside the fins. Had we made it out of coroplast, we would have needed nothing else.

Round cowl engines are the easiest, especially if the cowl is truly round. Remind me to get back to you on that last (ancient?) pm. I keep getting busy with something or forgetting. CRS syndrome I suppose

Baffling seems only ussefull for twin opposite engines, am I wrong?
Maybe my monocylinder GF45i inverted engine could take advantage of this engineering, any pic or comments about it?
Now I´m in gasser it would be great a handy "bibble" on engines cooling tech, any link or web site?

No specific sites that I'm aware of. Some of the engine distributors have a blurb here and there about baffleing. DoD (down on the deck) would be the most likely to having anything specific that would be educational on the subject but I haven't gone looking. I'm certain that someone will be quick to clarify anything that's specifically available at any given site. Just hang tight for a few minutes and it should be forthcoming.

Most singles are left hanging out in the wind, clear of the cowl, to a great extent. The more of the engine outside the cowl the less the benefit. It never hurts to direct the air to the location that needs to be cooled, but with an exposed single the methods needed to create a low pressure area can be extremely awkward. Basically, it amost of the gead on a single is outside the cowl I would not be much concerned about cooling air. If the cylinder is mostly inside the cowl then cooling air entry and exit should be looked into a bit more.

Innitially what I spected to do was follow the rule exit air area should be at least 4 times the fresh air intake area. My Christen Eagle´s cowling is big enough.
I got interested baffling not only by the engine but keep the warm air far from the ignition box and other plastic hardware surrounding the engine
I´ll look a little on the DoD web for a while...

The baffles in Chip Hydes plane follow full scale practice of a high pressure plenum.

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Still learning to upload photo

OK, I think I understand the principle and what is to be accomplished.
I decided to lean my engine for max power.
I now have it set to rip my 26x10 propeller.
It has never done that before.
When I land, the engine is a lot hotter than it has been in the previous 800 flights or so.
I will have to look at installing cardboard to the inlet to see how it looks.
I have relied on the exhaust pipes to create the negative pressure.
It may be wise to put damns in the outlet opening to generate more negative pressure.

This is a dumb question but which of the baffles offer better flow.
1) Top directing air down
2) Bottom directing air to the center of the engine jugs
3) Side to direct the air to the cylinder top.

What is the interaction of the three.
Thanks

They way I would do it is similar to the picture Dick Hansen posted somewhere here recently.
Bottom to jugs, side to caps and top to make it flow down the backside of the cylinders and out.
Use lip on bottom of cowl to create a low pressure zone for better draw.

On the BME the caps dissipate a lot of heat so they must be in the airflow. This is straight from Keith.

Making a pressure plenum gives the best airflow with the least resistance. I have several links in my other computer to the why and how of engine baffles including model and full scale but it crashed and I haven't had time to recover the files.

skypilot--If you ever recover those files post the links, I would like to read them and I imagine everyone else too.

I was going to say the same thing.
I see guys with baffles in there planes but I have tried to glue balsa in a cowl and it didn't seam to work to well. Could not get it to stay long enough to glass it.

0-200 engines as installed in C-150 are baffled similar to the Chip Hyde example but in addition have sheet aluminum wrapped around and spring clipped to the cylinder. These have an ~2 inch wide seam, on the centerline of the cylinder, for air inlet and exit. The purpose of this is to force air through the cooling fins for a much longer cooling path than just the !QUOT!edge!QUOT! effect next to the baffle. this results in a more even cooling around the circumference of the cylinder.

When I first this I was appalled, there was no way there was enough airflow around the cylinders to handle the cooling. Rational thought then took hold and I realized the guys that designed the baffling knew what they were doing.

More even cooling around the total circumference would help to promote ring seal at running temperature probably not a huge consideration.

I do not advocate doing this to our aircraft unless a thorough test setup is contemplated with proper temperature monitoring.

You have to contain the inlet air - the flow intensity will depend on outlet low pressure setup.
the setup I used here - is held to motor box with four #2 skt head screws -comes off in a minute -but has never unintentionally loosened
If you want to glue stuff into cowl - use clear silicone rubber on cleaned glass surface - make little angles in any plates at their bases to provide good support. epoxy or goo can cause dimpling which will show on outside of cowl.

Hi Dick,

That is very much how I did my OS 160FX with an additional horizontal shelf glued to the cowl to direct the air to the center of the cylinder and the port side was blocked and partitioned off. After reading a few articles I found that it is better to have a larger Plenum above the cylinders. I suppose it really doesn't matter that much in our engines and your baffles are better than most people would ever make.


I found one good link to full scale, still can't find the one where the guy was machining model engine heads.
http://www.avweb.com/news/savvyaviator/188945-1.html

You will need to register for free to view the link.

The one piece cowl meant a plate and seals would be required to get the full scale setup - heavier and a Bit-h to do - so I opted for a discrete setup -stopping air flow at upper inlet of cowl --this setup is very light and close enough for folk music.

another example, mich like Dick's alu boxing.
from NACA publications:
Station 1 is the high pressure plenum chamber, station 3 is the low pressure exit. A single baffle plate (red line) works surprisingly well, because there is a lot of turbulence in the high pressure area, and the baffle plate creates new turbulence that "scrubs" the cooling fins in the low pressure region.

Good Stuff Guys[sm=thumbs_up.gif]

Pe,

I sure as heck don't want to know where you got that stuff. It looks too much like something I've seen before.

the system used on the early VW automobile engines is also adaptable
The system Pe shows is a good one -
When I studied Fluidic valves - the principle of wall attachment by fluids (edit) (Coanda effects) was really interesting and it was a quick leap to seeing how the flow of air in intake ports - exhaust ports -cooling ducts etc., all shared common ideas.
editorial comment: fluidic valves have no moving parts-- the valve retains or changes direction of output from air attachment to interior walls .
air flow is at low speeds and valve interior sizes are very small - once a path is setup the direction continues unless some interruption occurs such as a short impinging air stream which then flips the attached flow to another output path.
on very small passages the attached air creates strong control of entire airstream moving thru - as the pathway increases in size this effect changes . the air may be slower along the walls and faster in the center of the passage
wings and lift and all that stuff acts in the same manner.
ditto for flutes and trombones etc..
FWIW-----

Good point, Dick. The understanding of fluid dynamics goes a very long way in understanding the airflow over/through our engines and inside a cowl. Air is a fluid, as some may have forgotten, and follows all the same methods and theories.

That's the reproduction of some of the ideas exposed above, couple of things:

1) 2 removable halves, joined by "upper bridge".

2) Use balsa sheet reinforced with CF clothing, will use some foam and/rubber to seal any gaps against the cowl.

... needless to say that is a painful and slow process. I am posting the picture of a carpenter's tool that I used during this process. This tool can help those that would like to replicate the inner contour lines of your cowl, very useful.

[sm=thumbs_up.gif]

OK, I changed my baffling and now my engine does not come up to temperature.
Made 4 flights today and following each flight, I could touch the cylinder within 3 minutes of stopping.
Ambient temps were around 60-65.
I notice that the midrange is now rich and going in and out of four stroke.
My question is should I lean the low end some more or leave well enough a lone?

Lean it slightly. See what a difference good baffling can make.