Fibreglass CPU Duct for a Quiet Home Theatre PC

"Don't breath this"New Zealand Freeview has just launched it’s high definition DVB-T TV service and my existing HTPC was nowhere near up to spec for decoding the high def streams. It was also too noisy for a computer that lives in the lounge so it was time for a rebuild. I was pretty excited; this is my first brand new PC in about 10 years the last one was a Pentium 120 when I was still at school! Of course I’ve had plenty of second-hand and hand-me-down gear between then and now.

The two main requirements for the new build were enough power to decode high definition video and quiet enough not to drive me crazy. Quiet means efficient cooling, I.e. good air flow.

I wanted to run the fan at very low RPM while maintaining good air flow across the CPU and video card; the idea is to pull air past the passively cooled video card, though the CPU heat sink and vent it straight out the back of the case.

I could have hacked a duct together with cardboard and tape but that would been just too easy, besides I wanted to try my hand at some fibre-glassing. After much research, trial and error Here are the basic steps I went though.

Materials (Fibre glass bare essentials can be had for about NZ$50)

  • Polyester resin
  • Methyl ethyl ketone peroxide (MEKP – The catalyst used to harden the resin)
  • Fibre glass re-enforcing Chopped strand Matt (CSM)
  • Polyvinyl alcohol release agent (Used so you can separate your part from the mold)
  • Release wax
  • Acetone (For cleaning up)
  • Cheap bushes
  • Mixing containers
  • Latex gloves. (Keep the nasty chemicals from burning your skin, Box of 100 – you have to change them often)
  • Stirling sticks
  • Respirator mask
  • Casting plaster to make the mold (Not used in the end. See trial and error!)
  • Wood, plywood, tape, misc tools, sandpaper, etc etc

Thanks goes to NZ Fibreglass. They were very helpful; they sell in small and large quantities and took me though exactly what I needed to get started so if your in Auckland and need fibreglass gear it’s the only place to go check them out at:


1. Make a mold from wood (and masking tape!).

Basic Mold

2. Coat the mold with resin and some fibreglass re-enforcing where strength and shape is needed, around the corners and over the masking tape.

Mold Coated with Resin

3. Sand the resin coated mold very smooth

Cleaned and Polished Mold

4. Wax the mold with release wax; about 6 coats, till it’s very shiny.
The guy at the fibreglass shop was very kind and gave me the last of a tin of wax they had in their workshop; saving $30

Waxed Mold

5. Brush on polyvinyl alcohol release agent. This stuff is great, it forms a sort of plastic bag-like skin so you can release from the mold. It should really be sprayed on evenly with a proper spraygun but this will have to do.

Brush Mold with Release Agent

6. Now ready for the first layer of fibreglass. Mix up the polyester resin with the hardener. Soak the resin into the glass with a dabbing action too much brushing and the fibres will start to be dragged around with the brush. The glass should be saturated and become transparent.

Mix Resin and HardenerFirst Layup

The first layer is done!

First Layer Done!

7.Now the moment of truth; separate the part from the mold?

Separate the Piece from The Mold

Note the PVA film has formed a barrier between the resin and the mold.
At this point I’m wondering if the wax was really necessary.


The part released reasonably cleanly

Part separated from mold

8.Add more re-enforcing and a top coat of very thin glass tissue. (My homemade roller helps get out air bubbles)

Fibreglass Tissue Finish

9. Clean-up (sand), add holes for top of heat sink

Mold Sanded and Cleaned

10. Add bottom sections

Bottom Section Added to Mold

11. Lots of sanding to get it nice and smooth and ready for painting

Lots of sanding to prepare for painting

12. Into the “spray booth”….

In to the Spray booth

…Prime and paint


13. Done!


Thermalright Heatsink

Duct Instlled (Far)

Duct Instlled (Near)

Full System Specs

  • Motherboard: Intel DP35DP Media series
  • CPU: Core2Duo E8400 3.0Ghz 45nm
  • RAM: 4GB Crucial
  • Video: Passively cooled Nvidia 8600GT (Gigabyte SilentPipe II)
  • Hard drive: Seagate 320GB SATA
  • Power supply: Enermax liberty 400(watt)
  • Case: Lian li PC61 (Big thanks to Chris for this very nice all aluminium case)
  • CPU Heatsink: Thermalright Ultra 120 Extreme
  • CPU Fan: Yate Loon D12SL-12 (700RPM @5 volts)
  • TV Cards:
    • Satellite (DVB-S)
      • Technisat SkyStar 2 (PCI)
      • Technotrend S1500+CI Module (PCI)
    • Terrestrial (DVB-T)
      • Hauppauge HVR-2200 Hybrid Dual Turner (PCIe)
    • Analog
      • Hauppauge PVR-150 (PCI)
      • Hauppauge HVR-2200 Hybrid Dual Tuner (PCIe)

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10 Responses to Fibreglass CPU Duct for a Quiet Home Theatre PC

  1. ray April 19, 2011 at 5:20 pm #

    sure mate, id be happy to do a guest post next project. what ive done you pretty much know but you might pick something up that you havent tried. you mentioned that you d tried to make a cast out of plaster, i ve thought of trying that myself, what went wrong? i can only imagine that maybe the plaster was too absorbent. if your ever in melbourne i could tee it up to take you through the factory that i worked at. i m sure the boss would be impressed with what you have done on your own. cheers

    • RhysGoodwin April 22, 2011 at 12:03 am #

      Hi Ray,

      To be honest I can’t really remember what went wrong with the plaster or paris except the resin never set up. I think that I didn’t let the plaster harden/dry for long enought and I think it was still too damp and cold. I wouldn’t rule it out as a mold making medium. I probably just didn’t apply enough patience!


  2. ray April 19, 2011 at 4:42 pm #

    its gelcoated and yes it is polyester as for the mould, well thats what i like about your work you actually made the plug from wood, i just took my rc car shell and made a mould out of that. my first attempt was the same thing only making a 3 piece mould. it was really just an experiment and the final product had join lines but i wanted to have a go at it, would have been better suited to a boat hull where the join line is on the bottom. i ll take some pictures of the moulds if you like and send them to you somehow. cheers and keep up the good work!! you ve inspired me to make my own plug!!

    • RhysGoodwin April 19, 2011 at 4:56 pm #

      Good stuff. Yeah I’d be keen to see. And maybe you could do a “guest post” here sometime if you’re keen?

  3. ray April 19, 2011 at 3:45 pm #

    would be very interested to see. i used to work in a fibreglass factory in melbourne australia, but only in the finishing area where we would trim , repair and clean the finished products. i have bought some supplies and just started to make a couple of moulds myself (trying to sell an rc car shell on ebay at the moment but not going to well, probably a bit too plain ) i m really looking forward to seeing your work and maybe getting a few tips 🙂 cheers mate

    • RhysGoodwin April 19, 2011 at 4:24 pm #

      Wow Ray that’s really nice! How do you do the mould for that? And is it painted or gel-coat? Or do you just put pigment in the resin. Polyester I presume? I think I should be getting tips off you! My current project is just a basic cast resin box for housing another electronics project I’m working. I’d like to do a full PC case one of these days from fibreglass. So many projects! but must finish some before I start any more!


  4. ray April 19, 2011 at 10:32 am #

    very nice indeed amazing for a first go at fibreglassing well done mate

    • RhysGoodwin April 19, 2011 at 1:16 pm #

      Cheers Ray. Thanks for stopping by. I’m in the process of doing some more stuff with resin, this time with clear casting resin. I’ll post about that in the next couple of weeks hopefully.


      • Charlee May 16, 2011 at 7:02 pm #

        I feel so much happier now I unesdrtnad all this. Thanks!


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