Oh no, There is every danger that this thread can degenerate into the perennial wheels up/wheels down when landing a glider on water debate!
:) > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:aus-soaring- > [EMAIL PROTECTED] On Behalf Of Patrick Barfield > Sent: Tuesday, 9 May 2006 8:42 AM > To: 'Discussion of issues relating to Soaring in Australia.' > Subject: RE: [Aus-soaring] aquaplaning - was Cruise Controls and Gliding Ops > > The rough rule of thumb for dynamic hydroplaning (i.e. aquaplaning) is 9 x > SQRT (Tyre pressure). If tyre pressure is in PSI, this gives the minimum > hydroplaning speed in knots. If the car tyre pressure is 36 psi, > hydroplaning should happen above 54 nm/hr or 100 km/hr which is roughly > consistent with the figure that Ann quoted. That's why Harvards can fly in > formation skimming along the water and super-cubs with 18" balloon tyres can > land on the water in Alaska and roll up to the river bank (See video in > http://www.alexisparkinn.com/aviation_videos.htm) > > > The formula is only an approximation and the tread width and tread length > also has a bearing on the speed. > > The other types of hydroplaning such as viscous and reverted rubber (as in > wombat's worst-case scenario) happen at lower speeds. There are many > internet references on the subject if anybody wishes to find more > information. > > Happy landings, > > Patrick Barfield > > > > > >A car will normally aquaplane when it is travelling at approximately > >112 kph without cruise control on. There is nothing you can do > >about it once it starts. > > > >It happens often on the motorways in the UK. > > > >Ann > > There is an old formula relating aquaplaning speed in MPH to some > factor times Square root of (tyre pressure in PSI) - but I can't > remember the factor. I thought there was a 27 there somewhere - > perhaps SQRT of 27 x TP which roughly fits Ann's numbers. Water depth > must also exceed ability of tread to clear the water, so worn tyres > increase the risk. Anyone else remember the formula? > > Worst-case scenario is aquaplaning on melted rubber from locked > wheels, which rapidly wears flats on the tyres. However if you lock > wheels the water also accumulates more than if the wheels are > turning, and the aquaplaning speed decreases dramatically - this is > the origin of the Dunlop "Maxaret" anti-skid device which is the > precursor of ABS brakes. Both work by releasing brake pressure if one > wheel stops rotating and the others keep on turning. > > Wombat > > > > > _______________________________________________ > Aus-soaring mailing list > Aus-soaring@lists.internode.on.net > To check or change subscription details, visit: > http://lists.internode.on.net/mailman/listinfo/aus-soaring _______________________________________________ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
