Editing Make a fiberglass fan shroud

This in-progress article demonstrates one way to build a fiberglass fan shroud. The techniques used in this article can be applied to just about any part that can be constructed from fiberglass.

===Measurement and analysis===
This radiator in a 1961 Ford Galaxie needs a fan shroud.

[[Image:161_starliner_radiator.JPG|thumb|center|600px|Radiator in a 1961 Ford Galaxie, in need of a fan shroud.]]

Start by measuring all of the dimensions, taking care to consider all of the following:
#How the shroud will attach to the radiator.
#If there are any obstructions you need to take into consideration.
#The distance between the fan and the radiator.
#Any significant angles or off-center components.

For example, this fan is off-center towards the passenger side by about 1/2 inch, sets back about 1 3/8" ,and it swings about 1" above the top of the radiator. It is parallel with the radiator, and there are no hoses or other obstructions to deal with on this particular project.


[[Image:261 Starliner rad rh.JPG|thumb|center|600px|Side view of radiator in 1961 Ford Galaxie.]]

===Constructing the foam buck===
Using a piece of thin plywood is a good way to start on any part that has a flat mounting surface. The plywood gives a sturdy base upon which to lay out and construct your foam buck. 

[[Image:3start laying out.JPG|thumb|center|600px|A piece of plywood is used as a sturdy base for constructing the foam buck.]]


[[Image:4laid out.JPG|center|600px]]

I had a bunch of 2 lb polyurethane foam left over from other jobs, so I thought this project would be a good place to use some up.
It also can illustrate how easy it is to use this foam -- it cuts so easily and shapes so well that piecing it up doesn't add all that much time to the project. This foam is available in thicknesses from 1/2" up to 6" thick at any fiberglass supply house. You can also use the polyurethane insulating foam that is available from building supply stores. Just peel the foil layer off. (Keep in mind that styrofoam won't work under any resin with styrene in it, unless you can bar the resin from it.)
[[Image:7box o scrap foam.JPG|thumb|center|600px|Leftover scraps of polyurethane foam are useful for constructing a buck.]] 

Cut foam to shape with a handsaw, putty knife, or bandsaw. Then, fit and glue pieces of foam larger than your layout on the board. A hot melt glue gun makes gluing this foam fast and easy. Glue the foam down with an expanding urethane glue, or some of the expanding foam that comes in an aerosol can. The different glues can make sanding over seam lines difficult, as they are usually a different density and hardness than the surrounding foam. 

Shaping this foam can be done with sandpaper, sureform files, knives and picks. Even your fingers can shape this foam quite easily and rapidly.
[[Image:5start foam.JPG|center|600px]]

 

[[Image:6scribe a circle.JPG|center|600px]]

[[Image:8laying out the circle.JPG|center|600px]]

Keep the hot melt glue away from where you will be sanding, it is gummy and will not sand properly, making your buck alot harder to shape than it needs to be.

[[Image:9it's hot melt glue.JPG|thumb|center|600px|The glue won't sand properly, so keep it off the areas you will be sanding.]]

I knew that one part of the shroud was going to be perfectly round, so I set it up with a bolt in the center and made it so it could be spun by hand against an end mill. This will make it easy to shape the circle, as well as cut the box section down to its proper thickness.

[[Image:10fast way to make a perfect circle.JPG|center|600px|A bolt centered in the buck allows it to be spun against an end mill to shape the circle.]] 

[[Image:11more shaping.JPG|center|600px|The buck is spun by hand to form the circular portion of the shroud shape.]]

[[Image:13roughed out some more.JPG|center|600px]]

[[Image:14edge detail.JPG|center|600px]]

[[Image:15final shape.JPG|center|600px]]

[[Image:16more final shape.JPG|center|600px]]I made a small miscalculation in laying out my initial circle, so I needed to add a bit to the outer edge.

[[Image:18even still more final shape.JPG|center|600px]] 

One step that I do on these kinds of parts is to paint the buck with resin after shaping it. It makes it a little more dmensionally stable, and toughens up the surface for the next steps.



[[Image:19paint with resin.JPG|center|600px]]

Once I have painted the buck with resin I can clay up any low spots, and then wax the resin. I then spray a coating of polyvinyl alchohol on the waxed surface. Polyvinyl alcohol, or "PVA", is a water-soluble plastic commonly used as a release agent for molds. Using PVA will make removing the foam much easier after the part is laid up.

[[Image:20wax and PVA.JPG|center|600px]]