I have been saving this plastic for a while now. I am doing a gravel grinder this weekend: www.chainbusterracing.com
This will be a very cold race. High speeds and freezing temps are expected. I usually have an interior layer of insulation in my helmet, but this plastic will give me some aerodynamics.
Like a TT helmet with no forward vents, this plastic will smooth out the windward profile.
This is heat moldable plastic that came off my spinach container.
I cut the container lid before taking the photos, so this is all that remained.
Take an ordinary helmet
And with a heat gun mold the plastic to the shape of the helmet. I used the heat, then my sleeve to press the hot plastic into the helmet.
You end up with this, a clear plastic form of the helmet. Next step for me is to clean the sticker residue.
The final step is to secure it to the helmet. I used electrical tape which is able to stretch to the contours of the helmet.
With it clean an optional step is to paint the underside. It will appear shiny from the outside.
Now I have a more aero helmet that will also keep freezing air from flowing through the hemet.