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  • #1

    Dual Purpose Fans

    Not my idea and this idea may have already been posted on the forum. Using computer fans to cool avionics and defrost the windshield. 80mm computer fans from amazon, grill covers from Steinair. Keeping it simple, fused of course but no switch, will come on with the master switch. My Maules defroster was hot enough to affect the plexiglas, was distorted and crazed above the two defroster vents, the lower heat from behind the panel shouldn't affect the windshield, will be slower to clear on cold mornings.

    DSCF1851.jpg
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  • #2
    I did similar and it works great. In the winter it clear the fog off the windshield nicely.
    Last edited by whee; 10-12-2022, 08:05 PM.
    Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.

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    • kestrel
      #2.1
      kestrel commented
      10-12-2022, 07:36 PM
      Editing a comment
      Uhhh... I get the first sentence... ;-)
    • whee
      #2.2
      whee commented
      10-12-2022, 08:07 PM
      Editing a comment
      Haha! Sorry guys.
  • #3
    Would a grill cover be enough without the fan? Heat rises after all

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    • #4
      It might, that is a good thought that I didn't consider. But no downside to the fans,inconsequential power use, will never hear them with the engine running.
      Last edited by rodsmith; 10-14-2022, 10:48 AM.

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      • #5
        I find frost/fog to be worst when I've just started and there isn't yet much in the way of cabin heat. ...and the avionics haven't warmed up yet. I think the active airflow is probably important. One of the things it does is prevent your breath from flowing onto the windshield. This is a bigger issue with our RV-4 where the bubble canopy is not so far from your face. We have a cold air vent in the panel that I direct directly on my face when it is very cold out do "blow away" my breathing and keep the canopy from fogging/frosting. Once engine heat comes to life, I can typically turn off the cold air vent.

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        • #6
          Originally posted by Battson View Post
          Would a grill cover be enough without the fan? Heat rises after all
          I think it’s possible that could work. Might need more area for the air to flow rather than a single grill.

          I my case, the fan is on a switch and I only turn it on when I need to de-fog the windshield. This could indicate a single grill doesn’t allow enough natural airflow to keep the windshield clear. Flipping the switch clears the windshield in a few seconds.
          Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.
          • Likes 1

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          • #7
            Originally posted by whee View Post

            I think it’s possible that could work. Might need more area for the air to flow rather than a single grill.

            I my case, the fan is on a switch and I only turn it on when I need to de-fog the windshield. This could indicate a single grill doesn’t allow enough natural airflow to keep the windshield clear. Flipping the switch clears the windshield in a few seconds.
            That is interesting. What sort of weather conditions are we talking about here?

            Comment

            • zkelley2
              #7.1
              zkelley2 commented
              10-16-2022, 09:01 PM
              Editing a comment
              In my experience from about 1C to 5C is the worst for your breath condensing onto the windshield.

              Just like your car, if you keep air movement on it before it gets condensation, you don't even need the heat. After it's there you do.
            • Battson
              #7.2
              Battson commented
              10-16-2022, 09:26 PM
              Editing a comment
              Breathing on it before the big fan starts, that's the worst.
              I find that even if the plane is covered, on some mornings the fog is almost impossible to stop. Even with the engine running and windows open, it keeps on fogging up. Cabin heat does next to nothing to help, unless the engine is doing some work (maybe 1800 RPM or more).
          • #8
            Originally posted by rodsmith View Post
            Not my idea and this idea may have already been posted on the forum. Using computer fans to cool avionics and defrost the windshield. 80mm computer fans from amazon, grill covers from Steinair. Keeping it simple, fused of course but no switch, will come on with the master switch. My Maules defroster was hot enough to affect the plexiglas, was distorted and crazed above the two defroster vents, the lower heat from behind the panel shouldn't affect the windshield, will be slower to clear on cold mornings.

            DSCF1851.jpg
            Looking at your picture, the engineer in me says your grilles are way too restricted. You just want to keep fingers out and maybe a pen. Check out my installation. The simple CPU grille provides good airflow. This kept my windscreen clear on a frosty -27°C day. I couldn't see out my side windows until I got some heat, but the windscreen was clear. I think that the comment about the airflow keeping your breath off the windscreen is probably correct. Real world Canadian winter experience right here. My fan is on a switch located under the panel. I will probably move the switch to the panel at some point.
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            Last edited by randerson; 01-01-2023, 02:05 PM.
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            • #9
              Funny I hadn't seen this thread but we all think alike at some point. I've got the opening and plan to install the fan for this exact purpose.
              • Likes 1

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