Tuesday, October 20, 2020


 Actually I've been working on much more than the baffling but since the cowling and the baffling work together to keep the engine cool its a bit of a mixed bag of tricks.  I'm paying extra attention to the baffling because these tightly cowled RV's run hot and I don't want to spend time chasing cooling leaks after I start flying.

As I mentioned in a previous post I had planned to split the lower cowling in half to ease the installation/removal of this huge hunk of fiberglass.  This picture shows the "jig" I created with multiple strips of aluminum to hold the two halves in the exact position needed after I make the cut.  In this picture the cut has been made and as the picture below shows the 5 layers of glass that will become the flange that the fasters attach to.

This is the inside of the cowling with the glass flange laid up and epoxy curing.

Much of the baffle work began with edge deburring, hole cutting, and as indicated by this picture...modifications.  In this case two specific modifications are evident.  First is the little square "patch" you see in the middle of the picture.  This area of the lycoming cylinder has no fins for cooling.  That means if the baffling is flush against the cylinder no cooling air can pass in this area.  If you look at the cylinder picture below you will see what I mean.  My patch basically creates a small gap that will allow air flow past this area.  The second modification is a little harder to see.  On the far left side of the aluminum plate you will see a bracket with a bolt hole in it.  The baffle kit that comes from Van's is for a wide deck engine, my engine is a narrow deck.  They are similar but have a few differences such as the shape of the block and a few bolt holes.  In this case the inside edge of the baffle needed to be cut and reshaped to fit.  Along with that the bolt hole flange had to be fabricated to fit the new shape.

This is a picture of the inside of the same baffle piece.  Here you can see the small air gap that will allow air flow past the smooth portion of the cylinder wall...see below.

Here is the back side of the #5 cylinder.  You can easily see the small area where there are no cooling fins.

On the front side of the engine case there is another area that needed adjustment.  In this picture you can see the original baffle piece shape (it has the part number in blue ink on it) as well as the shape of the piece that I had to fabricate to match the shape of the engine case.

And here is the final product after cutting the improperly shaped baffle material off and attaching the correct shaped piece.  Much better fit.

I had to add this picture as well.  My good friend Ben has been helping me with a few tasks.  In this case he is back-riveting the stiffeners to the wing root top skin.  

I took this picture to help me fabricate a seal for the prop governor area of the baffles.  This is taken from inside of the ring gear opening looking outboard at the left side air inlet.  I need to fabricate a baffle plate that will seal the sides and top of the governor to the top cowl which can be seen at the top portion of the picture.

In this picture you can see the paper clips I am using to slowly trim the baffles down to fit within 3/8"-1/2" of the inside of the top cowling.  It took many iterations of install clips, install top cowling,  remove top cowling, measure, mark, and trim the baffling.

This little area took a LOT of time.  On the sides of the air inlet you will see some curved baffle pieces.  These have to be hand fabricated using paper templates and then aluminum bent to fit.  It took several tries before I was happy with the final product.  I also put one of these curved pieces on the inboard edge even though Van's plans do not call for it.  I may change that in the future but it seems like it prevented yet another possible air leak.

Finally, this is the left side air inlet with the prop governor issue I mentioned earlier.