storklappe

For a 100cc engine, do you put a baffle on the bottom of the front cowl opening, or do you also make baffles for the top and sides to direct as much air as possible to the fins?

Does anyone have any pictures of how they made their baffles?

Thank you!!!!

crfabbro

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Check out Cactus Aviation's site. They have a few pictures and stuff on baffling. chris

stomper

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Here you go >
http://www.cactusaviation.com/Tech/baffling.html


HTH

3D Joy

Really nice information [8D]!!

I wish I had this info when I did mine.

I & C Tech

I just looked over that info at Cactus. Why wouldn't you want airflow over the bottom? That was an Extra. What about a round cowled plane?

3D Joy

For the first part of the question : "Why wouldn't you want airflow over the bottom?" Because the airflow naturally needs to go down, the only air exit is down. You need to cut at least 2 times on the bottom from what you have as an opening in the front of the cowling so the air goes out happily.

As for the round planes, I don't know [:-][] but still interested in the answer.

sillyness

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There is still plenty of airflow over the bottom... it is sucked down through the fins. If you don't baffle like the cactus pics then the air diverts toward the bottom as soon as it passes the lip of the cowl... bypasses the bottom fins completely.

The engine is not cooled by ram air... the air behind the prop is almost static. It is cooled by higher velocity air passing the outside bottom of the cowl, creating a low pressure area, and sucking air out the exit hole. This in turn suck air in the intake.

Aso for baffling the top... I think it depends on the motor. DAs run cooler, 3Ws and BMEs run hotter. I can't speak for others. On my DAs I don't baffle the top and they are plenty cool.

Yes... round cowl airplanes need baffling.

RTK

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This is all the baffling I am using on my BME 110/Comp-arf and to date no heat related problems. I have NOT enlarged the exit area either. I would baffle any engine that is completely cowled, it is cheap insurance and weighs next to nothing.

stomper

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Heres one

Richard D Bahmann aka/Wrongway

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Any of you guys have any tips on material for the baffles and install techniques? What about a single cylinder baffle install? Does a 50CC make enough heat to be concerned?

stomper

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I use Balsa sheet cut and fit to the cowl and engine. I then take the balsa and lay some lite fiber glass cloth over the balsa with some thinned epoxy on one side. After it has cured I reinstall the balsa baffle in the cowl with some more glass cloth and epoxy bonding the baffle to the cowl. I then paint it black.

Zeeb

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That material you've used looks flexible, is it? If so, would you mind telling me what it is?

I'm just getting ready to try the baffling install thing on my first twin cylinder model, and I was thinking some sort of flexible material similar to that used on full scale aircraft but thinner, would be the way to go. You can get that stuff in a couple of materials including silicone but it would be a pain to work with on something as small as a model since it's about 3/16" thick and kind of stiff. It's also pretty spendy since it's sold as FAA/PMA approved parts. Perhaps one of the thicker flexible type gasket materials?

RTK

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Zeeb--Yes it is flexible but nothing special, plain old balsa painted

sillyness

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1/32" lite ply stiffened (where you can't see it) with 1/4" balsa square stock after the baffling has been cut. After it's cut and stiffened, I give it a light coat of high temp flat black paint. Then I install it with a bead of Plumbers Goop. Is very light and works like a champ.

I & C Tech

Doug,

Why isn't the bottom baffled? I would have guessed it would be like you did the top. And on RDB127's question, do 50cc classers generate enough heat to be concerned or are there to many variables to generalize?

stomper

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In the 100cc Yak picture I posted, the Baffle diverts the air coming into the cowl down and over the cylinders.

On my 50cc Yak I have no baffling at all as it's just not needed.

Swat Cop

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I have found its a lot easier to cut up some 3X5 card to make the template for each section of baffle and tape them together. Once you have each piece the right shape in cardboard cut them out of balsa. I CA them together then paint them with with epoxy and then paint to color after that drys.

Supermod56

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I use .016 aircraft aluminum skin, works great and available at any metal distributor, cut it with aviation snip and pop-rivet it together, balsa also works good.

Tom

athos341

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I baffle all four sides of all my cowls so that the airflow from the openings in front of my cylinders has no choice but to go over the cylinders. I get them as close as possible. My DA100 in normal flight has temps of 165 on the left and 158 on the right. With a 3d flight she runs at 185 on the left and 183 on the right. Baffling if done right is priceless.

Zeeb

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Well I work on full scale stuff as well as models, and on the piston engine aircraft proper baffling along with inlet and outlet sizes, is imperative if you want the engine to live...

So I'm familiar with the principles, but the stuff used on full scale while very durable just isn't going to work on a model. I've seen some gasket material that was slightly stiff but still flexible, it reminded me a lot of what they call baffle sealing material on the full scales, but it wasn't as thick. Maybe I ought to go bug Mr. Dick Hanson who's just up the road from me, and find out where he got that stuff. He wasn't using it for baffles but I think it would work great, although it would be slightly harder to attach on the inside of the cowl.

RTK

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athos---Have you used a thermo couple and telemetry to gather these number?

RTK

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Here is the coolest way I have seen to make baffles. The next time I put together a plane I am going to try this.

http://www.flyinggiants.com/forums/s...ead.php?t=1325

stomper

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Hey thanks for posting that as that is an awesome idea and will have to try it>

Tired Old Man

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That's a good idea. Makes a hell of a mess inside the shop but the shaping/sanding part of the operation can be moved outside. Using light glass and epoxy, it should come out as light or lighter than balsa sheet, glass, and epoxy and still be durable.

Rcpilot

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Does anyone have any ideas for how to baffle a single cylinder engine mounted inverted?

I'm using a Fox 3.2 in a Great Planes 1/3 Pitts.

There are 2 large bubbles in the top of the cowl and I'm sure a lot of air is going to pass right out those holes on top of the cowl. I can easily close them off and divert more air down and out the bottom of the cowl.

90% of the cylinder is inside the cowl. Only the top of the head and plug sticks out the bottom.

I am afraid that with such a big and roomy cowl, I won't get enough cooling. As was previously stated, air takes the path of least resistance.

I think the only way to actually get air right down on the cylinder is to build enclosed tubes or "ducts" and point them right at the engine. I've never done this before, and it looks like an impossible task. I know it can be done, I've just never had to worry about it. And I have no idea where to begin.

Any ideas?