Yes, I meant cavitation. I’m getting old, and I didn’t have my glasses on. The technical definition is that the local pressure is lower than the vapor pressure, so a bubble forms, then collapses in a loud and violent manner. I doesn’t have to be a prop, anything moving fast enough can cause it. Ventilation is when air travels down from the surface, usually along a leading edge of a surface piercing foil, such as a stern mounted rudder. This leads to the dreaded “dead stick” in planing boats, which is usually followed closely by a broach, spilled drinks, capsize, etc. Aft sweep makes this worse, and that is why most fast dinghies have the leading edge of the rudder vertical . Some very fast multihulls have anti-ventilation “fences” on the rudders. Other than the prop (and there is nothing that you can do about that), there will be little concern for such issues on a C-27.
Keith Sneddon From: [email protected] [mailto:[email protected]] On Behalf Of Joe McCary Sent: Tuesday, March 30, 2010 10:04 AM To: [email protected] Subject: RE: [IC27A] a rudder with a mind of it's own I just can’t resist… Perhaps the best way to stop this problem would be to cut off the head of the rudder as in decapitation. I am betting you meant cavitation and spell check “helped” you out. Cavitation is when water swirls into a funnel and air is sucked into the prop field and instead of pushing water it is pushing air/water mix. Joe McCary Aeolus II. #4795, West River, MD www.aeoluswestriver.net joe at photoresponse dot com From: [email protected] [mailto:[email protected]] On Behalf Of Sneddon, Keith - ES/IS. Under power from an inboard, the flow over the rudder is usually at a much higher velocity, and because of that plus the proximity of the prop to the rudder, is very turbulent (small scale phenomena) plus not very organized as per direction (due to swirl, capitation,etc.). __________ Information from ESET NOD32 Antivirus, version of virus signature database 4983 (20100329) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ________________________________ This e-mail and any files transmitted with it may be proprietary and are intended solely for the use of the individual or entity to whom they are addressed. If you have received this e-mail in error please notify the sender. Please note that any views or opinions presented in this e-mail are solely those of the author and do not necessarily represent those of ITT Corporation. The recipient should check this e-mail and any attachments for the presence of viruses. ITT accepts no liability for any damage caused by any virus transmitted by this e-mail.
