This plenum needs a lid to both hold the air filter and allow access to get it out for cleaning.

The blue foam on the plenum has been contact glued, ready to make the lid. The other parts still need quite a bit of work.

I wanted to make a lid with curved edges so the carbon would sit well. On reflection a longer lid lip would have made the nutplates easier later. I’m not known for making anything easy.

After cure and separation I have a tight fitting lid.

An hour or so got all the blue mold foam out and a clean hole in the top.

The air-filter is that tight fit to the lid I wanted. With a hose clamp goes on the outside it doesn’t need to be RTV’ed in place and I’ll be able to completely remove the filter for cleaning.

Looking through the still rough ‘firewall opening’ you can see the model airplane spinner I have on top of the filter. The idea here is to cleanly separate the incoming air that is then sucked into the sides of the filter. Just using the flat filter top is a bit of a sudden handbrake even for the slowing and expanding air.

The U shaped pipe still has to be joined to the long piece but I have enough for some trial lining up now.

It looks like this is going to work out. I’ll need some aluminum pipe pieces where hose clamps will go. I will use two of those silicone rubber joiners which I hope will be enough of a buffer between the fixed firewall plenum and the movement of the engine.

This is where the plenum will sit. (Now a week or so later I will have to adjust this by about 3mm or so. Such are the very tight tolerances.)

How was I going to make this work? I went for a 5 ply layup with some reinforcing strips. The odd shapes, oddly worked.

Ahhh so pretty. This was a challenging job under the plane that took all day if you include the prep work. I think just this part was around 7 hours.

After the cure and a bit of a clean up, we have a plenum fitted and angled. As I said earlier, it will need a tiny adjustment to juggle the angles.