The Radiator Duct
The standard Stalker has a very attractively shaped radiator inlet that opens to a radiator deep behind the nose. Unfortunately it also has very large gaps around the radiator. This allows air to spill around the radiator rather than going through it which reduces cooling efficiency. Colling is normally not a problem with Stalkers, but every little bit helps, especially here in Tucson. The gap is also not very attractive.
The first step was to cut standard blue insulation foam board into the appropriate shape to fill most of the gap around the inlet back past where the radiator will be.
This picture shows the first layer complete. At this stage there is NO adhesive holding the foam to the bonnet, just mechanical fit of the foam board. The shaping was done with a razor saw and a Stanley Surform. There are gaps between the foam pieces and the bonnet and between the foam pieces. These will be filled in with two part expanding foam. The reason I chose not to use the two part foam for the entire buildup was cost and efficiency. The blue foam board was $7.50. The expanding foam is a $25 per cubic foot expanded. This also allowed me to cheaply test the idea.
This picture was taken shortly after the previous picture. There is still no adhesive holding the foam in so I can easily change my mind if this doesn’t look feasible. It is difficult to see in this picture, but the gap around the radiator is less than 1/2 inch and I haven’t added the second layer that will match the shape of the radiator cooling core
The next step was to fit the rear bulkhead that will form the mounting plane for the grill. This was pretty painstaking and in retrospect I should have just formed it from several smaller pieces, it would have taken far less time.
Here is the bulkhead in final position before I opened up the radiator opening:
The yellowish stuff is the two part foam mixed up and used as an adhesive.
After gluing in the bulkhead I cut out the radiator opening then fill the space in front of the bulkhead with expanding foam. The trick is to use a piece of smooth plastic as a fence to guide the foam as it expands. The foam sticks to just about everything so you really don’t want to use anything but plastic. I used a standard white kitchen garbage back taped up in the rear. Then I pulled it forward through the opening and poured a bit up foam mix in and pulled on the trash bag. The resulting surface is not the desired final surface but is safely outside it so I can remove material to get where I want.
This is after the first pour:
It is too hard to control the foam with a dingle large pour, so I went with several small pours using the trash-bag to guide the foam.
Hear is after the third pour, starting up the side:
After I filled all the void spaces I removed the trash bag and had this:
The smooth finish is from the plastic trash bag, but will not remain after I establish the correct duct shape. Note all of the extra foam, a better fence would have prevented the waste, but taken a lot more time.
Here is the duct after shaping the foam:
This what I had after laying the first two layers of glass on the top of the duct. The point here is that if done correctly you CAN’T see the glass. The resin reenders it transparents which makes it easy to find delaminations and bubbles.