I think it is worthwhile to share some of my experiences here on the forum about a recent project that I did.  So here goes....

The idea for this project began several years ago.  It started when I first got my 801 up and running.  Zenith/Zenair had changed the cowl at some point, and when I ordered my FWF kit, I got the new cowl.  The cowl fit well, and most importantly cooled well in flight.  But it was quite difficult to fit the air intake.  Basically, I did not fit.  The supplied air filter housing was to be fitted to the cowl air intake, front and center - just below the prop.  But there was not room for it inside.  The exhaust interfered, and there was just no way to make it fit.

<-- Here you see the engine - no cowl.  Note the exhaust position below the flywheel......

Then over here you see the cowl on -->

and if you are keen you will notice that the air intake is exactly in the position of the exhaust system.  And guess what?  They don't fit together without any interference.  Just in case you are skeptical, here is a 3rd pic that shows the problem I encountered.....

Well as you can see, that is not going to work.  There is about an inch between the exhaust and the air intake.  That just could not work.

So I came up with a work around....

It looked like this.  I basically used the space I had to make a sheet metal intake (out so stainless as it sat right on the exhaust).

It wasn't pretty, and it wasn't very efficient air flow either.  But I figured I wanted to get flying, and elegant solutions could wait.....  But it always nagged at me.

There were additional problems on the other end of the air intake as well.  The airbox that mounts to the bottom of throttle body (vertical induction IO-375) would not fit in the cowling.  To be fair - that was my own doing.  The throttle body was larger than the normal one, because I had decided to use the Precision Airmotive Eagle EMS. Unfortunately the only way to fit the airbox was to turn it sideways, and then run my air intake around the side of the engine to wind its way in there.  All of these things ended up working OK.  I flew with them for a couple of hundred hours.  But I just figured it could be better........  

What I really wanted to do was to come up with a way to duct air straight in, and up the vertical induction.  Probably worth a few horsepower anyway.......  but how in the world to figure a way to do that?  It would require the meshing of some very complex geometry. And trial and error did not seem like the way to go.....  Then, EAA decided to let everyone have a free go at Solidworks.  I'm not an engineer.  I had never used Solidworks before (or honestly even heard of it).  I got to playing with it at AirVenture a year or two ago in the innovation tent, and got just enough information to try some very simple things.  It was sort of fun.  I enjoyed playing with it.  But had no idea how to apply it to my air intake problem.  Then one day I stumbled across some information about a 3d scanner.  Handheld.  The kind you can walk around an scan real life objects in 3d......into programs like SolidWorks.  Too bad they were about $15,000 - which is right out.  But the idea stuck with me, and searching eBay I came up with a 'low end' scanner for $400.  I decided to give it a crack.  The scanner (a first generation Sense scanner) had some pretty mixed reviews.  Most people said it lost tracking easily and couldn't complete a scan.  Other said it wasn't detailed enough for the small things they wanted to scan.  OK, well I figured I had patience, and my cowl and engine were not small figurines, so a tolerance of 1/4 inc would be plenty fine for what I wanted to do.  It actually turned out much better than that. 

First up was to scan the airplane (or at least the front part) with the cowl on.  It took just a few tries, and came out much better than i expected.  Maybe my low expectations made it seem easier.  Anyhow - it worked.  I think you can see from the pic - it is pretty spot on.

Next I scanned the entire FWF without the cowl on.  That was much more of a challenge.  Lots of patience required, but after about an hour or two of trying, I got a pretty good scan.  Good enough to work with.  The screen shot from my phone does not do the detail justice.  It was pretty good.

Next I used common reference points on the fuselage and gear to overlay the two scans on each other.  Figuring out how to do this probably took the longest of any part of this project.  But once I had them positioned properly, I could see the space between the cowl and FWF and design within that space.  

At about this time, I learned that the little laptop I was using was just not up to such work.  So I did end up having to pony up for more computer horsepower.  Fortunately I learned that Dell has an outlet, that sells refurbs and such for a steep discount.  Just my thing.  Anyhow, I digress.....

I was able to pare down the cowl to just the area the I would need to work with, and get some really good geometry planes.  I was able to design an airbox (based upon a K&N filter sized to fit my needs).  This airbox was going to fit inside the cowl just fine!  And be a straight shot to the cowl air intake.  So I used the magic in Solidworks called lofting, and guide curves to generate the shape of a duct connecting the cowl air intake and airbox, while avoiding all other hardware.

The red structure is the duct and airbox, laid in against the FWF 

And here it is on its own.....

Once I had the structure designed I needed to turn it into reality.  I have a 3d printer, but if you don't you can send of these files to get printed and shipped to you.  Probably would actually turn out better that way,  I had to slice my design into 5 different pieces to print, then glue them all together.  The final product came out pretty good.  I printed it all in ABS plastic.  I will be filling the seams, and then coating with gel coat and using as a male mold to make the final duct from fiberglass with a slick inside surface.  

Thats about as far as I am right now, but like I said, I thought it was worth sharing.  This stuff is just amazing to me.

It seems complex and overwhelming to start, but if I can do this, anyone can.  

Anyhow, blue skies tand tail winds to all....