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Pimp my lid

Discussion in 'Modifications and Projects' at netrider.net.au started by Bravus, Jul 13, 2009.

  1. We had a longish discussion here a while ago about the problem I was having with my helmet wanting to rise at speed. I take the point that I probably needed one size smaller, although my odd-shaped scone probably means what I *really* need is a more expensive helmet with adjustable padding so I can use more on the sides and less fore-and-aft.

    But there remains the issue of the upward force. I assume it's due to the laminar flow of air over the top of the helmet, and surmise that if I could break up that flow by adding a small spoiler, it might at least reduce the problem.

    Googling 'helmet spoiler' throws up a few, so obviously it's something that can be done, but most of those are specific to models other than mine.

    Any ideas about whether it can be done and whether it's worthwhile? I assume you'd want something that glues on, because any drilling would weaken the shell. Any other caveats?

    The lid in question is an HJC CL-14 ('Sword' graphics, not that that's relevant).
  2. I'd use the string and tape method to determine whether or not the air does in fact remain attached in normal usage. Get a camera or a mate to observe.

    I'm sure there is someone here with a better understanding of aerodynamics, but does laminar flow in and of itself create low pressure?

    I would have thought that for any significant lift to occur, the airflow would need to be 'smooth' all over, but faster on top. I can't see that happening with a helmet/neck/chest arrangement. But check it out by all means, and post the results up here!

    If laminar flow exists, and you want to break it up, you could test with some electrical tape pinched to create a ridge along its length, and place it from ear to ear.

    FWIW, a very quick google suggests that helmet spoilers are actually designed to reduce turbulent air, making the helmet look a little like a 'Kamm tail' car. See here.

    I'd be interested to see how you get on, but I'm not optimistic.
  3. Yeah, I'll have a play and report here, but the longer-term solution is definitely a new and better helmet. This one is 3 years old now, so I reckon I can probably hit the family up for a new one for my birthday next April...