Exhaust Manifold Heat Box Patterns

Based on the OX-5 parts list, under the right hand exhaust manifold there was a heat box.  I would assume it was for Carburetor Heat to stop ice forming in the carburetor.  But, according to Ted Barber, in his book The Barnstorming Mustanger, the WACO NINE he flew herding Mustangs in Oregon did not have Carburetor Heat.  It was only when he got a newer plane that he learned about Carburetor Heat.  I'm not sure what the heat box on the Curtiss exhaust was used for.
The picture of my WACO NINE from 1927 clearly shows the heat box on the right exhaust with a piece of tubing going into the cowling.  Nothing in the WACO drawings shows a Carburetor Heat arrangement of control to operate it.  I'm adding the box to both manifolds and we will have Carburetor Heat.  I wonder how someone with straight pipes gets Carburetor Heat?
The lack of Carburetor Heat appears to be one of the reasons this engine developed a bad reputation.  The other reasons, according to Parks Air College, were the need for Miller valves, better fits assembling the engine, and better oil.  They flew 1,000 hours between overhauls doing flight training in 1929.  I believe the coil in the magneto was also a problem, shorts and opens.

 One of the planes at the Airpower Museum has heat boxes on both sides but they are not connected to anything.  They are very nice looking stampings in a streamlined shape.  The streamlining seams excessive but I believe it was actually easier to stamp the parts in this shape because of how the steel stretches.
They are very nice looking but I believe they are a little small to get enough temperature rise.  The inlet is on the engine side so the air has to flow around the exhaust to enter, giving a little more heating.  They also placed the outlet near the edge opposite the inlet to give as much time for the air to heat as they could in such a small box.
The outlet pipe is spot welded to the box and the box is spot welded to the lower shell.

 I decided to make the box with curved sides but welded corners.  It is under the exhaust after all.  I could form such a nice box and make the rights and lefts from the same formed box by sawing off the inlet edge.  I think for the few I need it will be easier to weld the corners. The box is gone on my RH manifold.  If I had a known original box to duplicate I might form them.
I started by deciding what size to make the box and the made cross section strips from poster board to work out the size of the blank.  Clearly I could have done this on the CAD system but sometimes its more fun to just make patterns.

 I made it a few inches longer and place the outlet where it appears to be on my NINE.

 To give the air more time to heat up, I also decided to add a baffle in front of the outlet tube.  The box is 1" deep and the baffle will leave a 3/8" gap between it and the manifold.  It also only goes half way down each end so there is plenty of room for air to flow to the outlet without restricting the flow.
I'll  gas weld the corners and the outlet tube, then spot weld the baffle to the inside of the box.  The bend in the baffle is to direct the flow around the ends to add more time for heating.

 Hear is the position inside the box.

I made galvanized patterns from the paper patterns.  The baffle is at the top and a blank the size needed to form the outlet tube is in the middle.  I'll spot weld it closed to make the tube.

Now I need to make the blank pieces.