Will this force enough air down and past the fins to cool properly?

Do I need the "tunnel" behind the cylinder fins to direct the air down and out of the cowl?

OR:

Can I cut the tunnel off right after it clears the back of the fins?


I might end up trying to bury a can muffler sideways under the motorbox. I'm running out of room and I don't want cut a huge hole in the side of the cowl for the muffler to hang out. If I cut the sides of the tunnel off right behind the cylinder that will at least keep the air around the fins for the full pass down the sides of the fins. But I would not have any way to forcefully direct that hot air out of the cowl. That would open the area behind the cylinder for a sideways cannister muffler.

Obviously, I still need to cut an exit hole on the bottom of the cowl. That exit hole will take up all the space behind the cylinder fins. It's about 2" x 3" square.

That will be perfect. The idea is not to force air in, but pull it thru and out. Put a low pressure lip at the exit and you will be fine. All the air will have to pass thru the fins and will be pulled out the bottom

I figured it would work as is.

But can I cut the balsa out BEHIND the cylinder and put a cannister in there?

Sure, just be sure to have a good low pressure area to extract all the hot air out. You could even place some cool louvers there too.

I want to put a cannister muffler under the motorbox. But I'll have to cut out the tunnel of balsa behind the cylinder fins to fit the cannister.

Would that screw up the cooling flow of air over the fins?

Yes, I am putting a 1/4" lip at the exit opening of the cowl to create vacuum.

If I just scrap the cannister idea..........

Will this work to cool the engine the way it's built right now?

It shouldn't hurt, basically all the air that will come in has to enter via the front of the cowl and pass thru the fins. Home depot type stores sell little louver which could also be place in the bottom of the cowl below the engine. The more air you can pull through the better.

Cool! Thanks RTK.

Yes


You are doing a fine job of baffling, more people should give it a try. It will make your engine last longer and perform better too.

It wasn't all that hard. It was time consuming. I just started slapping 3/32 sheet on and went where it took me. I have about 8hrs in this baffle. I worked on it most of yesterday and today. Still need to paint it black. It clears the cowl by about 1/8" or 1/16" all around. I'm going to use some cockpit coping (foam rubber) and run it around the outside of the baffle to give me a seal and some vibration isolation. I don't want the cowl touching the baffle and I'm hoping the foam coping will provide the air seal I need without letting the fiberglass touch the balsa.

See the whole thread here, if you're interested. There's a lot more pics of the baffle in that thread.
http://www.rcuniverse.com/forum/m_7778877/tm.htm

wow

Those interested in baffles might find this interesting reading.
http://www.supercoolprops.com/articl...delengines.php

RCPilot;
Here again is the baffle I made for my Brison 6.4, which is powering my big WH Sukhoi. The cowl has also open louvers, which helps to suck the hot air out.

Virginian:

Can you post a pic of the open louvers?

Where will your carb get its intake air from? It appears from the pictures that with the cowl in place, the carb might be in a semi sealed chamber. Also, I wonder about the exhaust. While we all know that cylinder cooling is important, I prefer to have some airflow over the exhaust also. I'm not sure whether you'll have airflow in these areas or not.

Unfortunately, the carb will be sticking out in the airstream. It won't fit inside the cowl. [] Ugly, but plenty of air.

Muffler is a different story. If I use the stock muffler, it's going to be hanging out in the air as well because it's 3x4 and about 2" thick. Not gonna fit inside the cowl. I might purchase an aluminum muffler from www.wackerengines.com . I need to call him and make sure it will fit before I plunk down the $30 for it. If the aluminum muffler fits, I'll use that. If the aluminum muffler won't fit inside the cowl I will cut the stock muffler apart and braze a much smaller chamber that will fit inside the cowl.

I was thinking about the heat too. I'm not sure what to do. Maybe add some of these famous louvers the other guys are talking about? That would pull some air past the muffler. My baffle is not totally sealed. Air can go escape by going around the crankshaft and prop hub. Some of that air should find it's way to the muffler.

I have about 1.5" of space between the side of the engine and the cowl. I even thought about making a custom muffler that would will that entire space (large expansion chamber = quiet) and just have a 1/2" tube exit the cowl near the same place where the cylinder air exits. That space runs from the F2 former to the baffle. Probably 6" long. It's going to vary in height as the cowl slopes up in the front. That space could end up being about 30 cubic inches.

You might want to look into using neoprene vacuum tubing from a auto parts store, very cheap and it comes in many sizes. I just slit it and slide it on the part.

What about some wax paper over the edges of the baffles and then put a bead of silicone over that. Then attempt to install the cowl without knocking the silicone off the edges. I'm thinking that the silicone would stick to the cowl and seal up any irregular surfaces.

Sure can. I'll take a couple of pictures when I get home tonight.

...shoe goo is another suitable adhesive, and sticks very well to cowls. But the silicone would be much easier to remove if you ever needed to.