This baffle kit is very well done and comes with everything needed including the rivets and screws. The instructions are a little on the weak side but if you have come this far building your Bearhawk, you can easily figure this out.
Started: March 11, 2008
Baffles are required for any air cooled engine installation. The baffles create a separation between the top of the engine and the bottom. Cooling air then enters through inlets in the nose bowl, creating a high pressure area on top of the engine. Since the cool air has no where else to go, it is forced down through the cooling fins around the engine cylinders and the heated air exits out the bottom aft side of the cowl (the tunnel). It is important that the baffles fit snugly and that the only path for the air, is to go through the cylinder fins. Any loose fitting or leaky baffles will affect the engine cooling and will cause lots of overheating problems.
I have decided to save a lot of time and effort by going with the Baffle kit ($250 at the time of this writing) from Van's Aircraft. My engine is a Bob Barrows O-360 EXP. Bob makes this engine using IO-360 cylinder assemblies and case halves. Therefore, I ordered the IO-360 baffle kit from Van's. The kit is not a perfect fit for the Bearhawk but is a good starting point. It does require some alteration to properly fit the Bearhawk cowling.
Here is the Van's Baffle Kit as it comes out of the box:
This baffle kit is very well done and comes with everything needed including
the rivets and screws. The instructions are a little on the weak side
but if you have come this far building your Bearhawk, you can easily figure
this out.
The baffles, as they come from Van's, are oversized height-wise. This allows you to trim them to perfectly fit your engine cowling. The baffles near the nose bowl were undersized a bit and you have to add a little bit to them for a proper fit.
We will start by installing the side and rear baffles first, and then trim them to fit the engine cowling. Then the forward baffles will be fitted to size.
First a little engine modification. One thing I noticed while fitting my
cowling, was that I did not have sufficient clearance between the top of
the right front cylinder and the cowling. Specifically the baffle mounting
lug sticks up too far leaving less than 1/8" of clearance:
A call to Bob Barrows confirmed that this is a problem that a lot of builders using IO-360 engines have. That lug stands fairly tall and even some RV builders have an issue with it. The same problem doesn't exist on the front cylinder on the left side of the engine because that cylinder is offset further aft, so clearance is adequate.
The solution according to Bob? Cut it off:
The baffles will still have plenty of support without it and you will gain
at least 1/2" of clearance for your engine to shake, rattle and roll with
out hitting the cowling.
Now back to the baffles. I started by just seeing how well the baffles that came in Van's kit, fits right out of the box. The short answer is: "pretty darned good!"
Here are the side baffles slipped (actually snapped) in place:
The smaller pieces are reinforcement at the bolt holes. These fit so well,
they stayed in place without any screws.
Note that the baffles are oversized. They must be trimmed to fit the cowling later. The front and rear halves overlap each other by about 2".
Next I slipped the rear right baffles in place. Again a very good fit
right out of the box:
Some trimming will be needed later but not very much so far.
Here is the left rear side:
Again a great fit right out of the box. Note that on the left rear
side the baffles have to make a little joggle to get around the cylinders
that are offset to the rear on that side.
The left rear piece is made from thicker aluminum than the other baffles. This is in preparation for mounting the oil cooler, if that's where you want it.
The front floors also fit fairly well but will need some trimming:
Now I'll go back and carefully fit all of the baffle pieces and install all of the braces that hold them in place. Then they must be final trimmed to fit the cowling and the fabric baffle seals must be installed to create an airtight seal against the cowling doors, top, and nose bowl.