Improving the air flow in the Milan; air out-flow

It’s been in my head lately to create an SPAI (Stagnation Point Air Intake) for the Milan, to improve air flow through the velomobile. My WAW has an SPAI and it adds decent air flow, even though the headlight takes up quite a bit of the space inside the SPAI. I rarely ride at night, so should look at figuring out a different headlight set-up for the WAW.

I will be starting this week on making a plug, and then a mold for SPAI, but today I have a fellow Velonaut coming to my house and we will be going for a ride. I wanted to get this air-flow improvement started, so yesterday I began what should be an improvement by adding ventilation holes to the rear of the Milan.

There are many threads on recumbent forums about installing fans to push air into the velomobile, but just as important is out-flow of air. To me it’s similar to how I ventilate my house in hot weather. My house has a whole house fan installed in the second floor bedroom ceiling, and it pulls air out of the house, exhausts air into the attic, which has extra ventilation to the outside.

Open some windows in the house, turn on that fan (which is about 26″ in diameter), and it’s amazing how much cooler outside air it sucks into the house, far better than box fans trying to push air into the house. Air flow past the velomobile should suck air out of the holes (eductor or venturi effect).

So with that in mind, I began by improving the out-flow of air from the velomobile. On the rear of the Milan there was already one opening, about 7/8″ in diameter. And I had three nut rivets that I wanted to remove, remnants from mounting the Fly6 camera back here. The Fly6 rear-facing camera is now mounted up on my camera pylon, so those nut rivets are not needed. Here is how it looked like when I started:

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7/8″ hole, and 3 nut rivets that were used to mount Fly6 camera.
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Fly6 rear-facing incident camera, and Garmin 360 camera now mounted on top.

I happen to have a hole saw with a diamond encrusted cutting edge, 1.25″ in diameter, so I used that to cut the larger holes; this also was large enough to perfectly cut around those nut rivets. Cutting through the carbon fiber composite is fairly straightforward, but the builder also puts Kevlar on the joint areas. That’s a good thing for structural integrity and crash protection, but it does make things a little less clean looking when you’re done. Here are the cut outs.

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Top one has the 3 nut rivets, middle one shows all the Kevlar

I wanted to make it look good at the same time, so drilled 3 of the larger holes, and then another 7/8″ hole on the bottom to mirror the top hole. I then used a razor knife and buffing wheel on my Foredom rotary tool to clean the Kevlar up as good as possible. Used a red permanent marker to color things in better. My Milan is red and white gel coat (the blue part is a vinyl wrap) , but on the tail end it was a combination of the red gel-coat and some red vinyl reflective wrap. Wasn’t the cleanest look, but I kept telling myself “That’s good enough, don’t do anything else”….. that lasted about 5 minutes!

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The holes completed and trimmed.

I decided to put some 1″ wide black reflective vinyl tape over the area, to tie it together visually. I used 2 vertical pieces of the same tape that you can see on the sides, covering the bonding line. Also touched up all the hole edges with a black permanent marker instead.

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Before trimming for the holes.

Then, decided it needed some gold edging too 😉

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Hopefully this will add some decent air flow through the velomobile. Here are photos with the camera flash on and then flash off. This is how my lighting is for my rides lately; I’ve gotten into the habit of riding with the turn signals funtioning as running lights/turn signals (nice feature! turns on or off with a toggle switch). And the Fly6 I run with red lights flashing, to help get attention of vehicles approaching from the rear.

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Camera flash on, the black tape is reflective.
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Camera flash turned off; tape shows as black