Pictorial guide/worklog of modifications to 'HTPC', GAM's Home Theatre PC; Making a cheap, simple case better - Page 7

By Greig Mackenzie

Fibreglass Duct

This is initiation attempt into fibre glassing; the method I am using to create an irregular formed air duct.

NOTE: The front intake mod, including the fibreglass duct, won first prize in the Jan - Feb 2007 OCAU Friendly Modding Challenge (January 2007 Modding Competition Worklogs) held by Overclockers Australia (OCAU).

Objective

Form an air duct from the two front panel intake grills to the case mounted 120mm fan behind:

After measuring the openings to be mated and their relative locations to each other, I drew it up in illustrator and created some blends.

This gives you the idea of what was meant to be.

This is the template I was to use on each layer, but things change...

I had the idea to create a mould form using several templates, 5-6mm thick, stacked together to guide the subsequent shaping process.

I spent a couple of half days checking with various businesses in my local light-industrial area (Brookvale, NSW) to obtain the materials I (thought I) needed to do create this duct. No luck on the 'architectural foam' I had in mind for each template form. I did manage to obtain an off cut tail from a surfboard 'blank', though, thanks to one of the surfboard makers in the area.

Long story short, this is what resulted—unsatisfactory. As the initial piece I started with was not square nor of equal thickness, my roughly shaped form was irregular and wouldn't mate with the two surfaces correctly.

Plan B – Home manufactured foam sheets from 2-part polyurethane foam.

I was very impatient as I had to get this mod done by the 31st of Jan for the 'OCAU friendly modding challenge'. Patience is not always one of my virtues ;-).

NOTE: The official work logs of each entrant in the competition can be found on the Jan - Feb 2007 Modding Competition Worklogs thread.

At least this way each template would be square and of the same thickness. 6mm was cutting it too fine for this simple mould exercise, so I settled on four 8mm sheets (32mm overall). Front to back of the duct needed to be about 30mm.

I made a simple mould to form each foam sheet by nailing three strips of timber onto a piece of scrap melamine sheet, forming three edges of the foam sheet.

Polyurethane mixed and poured onto the mould with waxed paper on the bottom and the top for subsequent separation and removal.

Before the foam started to rise, I clamped another piece of scrap sheet on top to form the top surface of the foam sheet. Once the foam had expanded out of the mould and had hardened, I could remove it. The hardening process only takes minutes when the proportions of the 2 part polyurethane are correct. I made some mistakes and waited over an hour before I realised that something was wrong.

Once hardened, I removed the top sheet, the waxed paper and then the foam sheet.

Four home manufactured foam sheets.