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Re: The bike that slowtwitch built [23]
wow. apologies in advance, but there is virtually nothing aero about this bike. the wheels and the fork perhaps, but the frame is an unmitigated disaster from the top tube on down. the top tube should be ovoid anywhere rear of the head tube airfoil - full stop. and if the attempt here is to develop negative drag, airfoils of no more than 15%-20% should be considered - e.g. NACA 0015 or 632-015 - or even better, truncated Kammtail airfoils (e.g. a truncated NACA 0020 with a 3:1 aspect ratio) which will be much more forgiving in crosswinds, yet just as slippery and still generate forward thrust. furthermore, the rounded front on the head tube and elsewhere on the bike likely experiences complete flow separation well before its apex (at about 82 degrees) creating pressure drag and turbulent airflow. moreover, the undulating sides of the frame are simply creating skin friction and/or flow separation and pressure drag - you'd be better with nothing at all. and that tail? sorry.

the best thing you might be able to do to repair some of this is install 'trip wires' -- around 0.5mm-1mm thick should do it - the entire vertical length of the head tube and anywhere there's a forward facing tube surface. place the 'trip wires' on either side roughly 30-45 degrees away from center axis -- this may at least re-attach the airflow to the sides of the frame.

the other option is to rip it all out and order truncated NACA 0020 foam cores from someone like Flying Foam (http://www.flyingfoam.com) and then cover them with a fiber composite layer.

then of course there's the reduced trail in the fork by going 'funny' with the 650c on the front. no issue going to a 650c, but important to go with a 650c wheel in the rear as well. that'll drop the bottom bracket to just above the UCI/USAT minimum of 240mm (hey, you're already about half-way there...), and by re-introducing the correct amount of trail in the front fork, you'll also get some control back (all the more so since the bull bars have been cut off...)
Last edited by: chadman_98126: May 14, 13 0:18

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