Thursday, June 30, 2016

Workin' on the plenum....again

If you have followed my adventures at all you know that the cooling plenum that I purchased from Sam James is not my favorite purchase.  I won't rehash that tired story but it is relevant because I spent the last couple of weeks working on the plenum again.  The short story is that my oil temps are still higher than I want them to be.  When we flew on a warm day I had a hard time keeping the oil under 220 degrees.  I've done several things to try to decrease the oil temperature on the aft side of the engine so this time I decided to try to do something on the forward side.  The inlets that allow cool air to enter the plenum area are about 5 inches in diameter.   The plenum necks that down to a much smaller size and then sits pretty tightly on top of the engine.  My idea was that if I removed some of those restrictions the amount of air available to cool the oil would increase.  So I did the left side of the engine a couple of weeks ago and it seemed to help (but still haven't flown extended periods in hot weather).  I spent the past few days doing the same thing to the right side.  This time I decided to take a few pictures to help describe the process.

On a related note we had our annual Young Eagles event last Saturday.  That's when we volunteer our time, airplanes, and fuel to fly young kids from 8 to 16 years old.  I flew 14 kids on Saturday and had a blast doing it.  Those kids are so much fun!
First things first, here is the 9A sitting with other airplanes at the Young Eagles event on Saturday.  The airplane before it should look familiar as I posted several pictures of it recently.  It is Greg's and was in the same paint shop as mine.

Ok, so in this picture you can see the restriction in the right side.  Its hard to see the top part but believe me its restricted.


Here I put a few lumps of clay on top of the plenum and then put the top cowling back on to measure how much room I have between the two. 

Then I mix up some pourable foam and make a mess...

Another view of the mess

Starting to trim down the mess to a shape I can work with.

This is the foam product that I used.

Ok, foam is now sanded to the shape I want.


Now I lay up 4 layers of fiberglass over the foam.  You will notice I used a lot of packing tape as a sort of mold release for both the foam and the fiberglass.

In this picture I have trimmed up the cured fiberglass, removed the foam, cut the plenum under the fiberglass away, and "glued" the new fiberglass piece in.  I used an epoxy/flox mixture to glue the two pieces together.

Another view of the two pieces but this is after they had set up and I had done a little sanding on the final assembly.

This is the section of the old plenum top that I cut out.  You can see the circles where I marked the clay locations and heights.

In this picture you can see where I cut the old top out and glued in the new.  All that's left now is a little sanding and maybe a layer of micro or two to clean it all up.

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