Subject: [harryproa] Proa rudders
From: "cruisingfoiler@yahoo.com.au [harryproa]"
Date: 12/21/2014, 12:27 AM
To: <harryproa@yahoogroups.com.au>
Reply-to:
harryproa@yahoogroups.com.au

 

Concerning proa rudders, I've been looking into the performance of a fine entry rudder on the basis of Rick's concern that the Speer sections are likely to suffer from vortex induced hum at higher speeds.  Other than Kevin O'Neil's results where he was extremely happy with how the Speer sections worked, I have no real empirical results to go on.  O'Neil probably hasn't refuted this problem as I suspect his craft isn't reaching 20 knots plus.

Anyway the results are attached.  Rudder Sections.jpg shows the fine entry proa section I've developed (purple).  It's 12% and has a finer entry than the Speer 12 and 10% boards.  All are symmetrical.  Rudder 4m.jpg and Rudder 2m.jpg show results at Reynolds numbers of 4 and 2 million respectively.  The P rudder (yellow in the 4M results and red in the 2m) is comparable with the P30012 on L/D, mostly better other than with zero angle of attack, and given that rudders aren't balanced (particularly on proas) this result represents a good compromise.  In the bottom right hand graph it can be seen that  Cp min is lower with angles of attack +- 2 degrees, meaning the foil is less subject to cavitation with attack angle.  However the foil is only generating lift equivalent to the Speer section for a given Cp min for lift coefficients up to 0.1.

This result shows promise for high speed rudders where vortex hum becomes an issue.  I'm interested in the thoughts of others re this issue.  I probably won't be spending much time exploring different shapes in the near future as the broken hand is on the mend and it's time to get building.


__._,_.___
Posted by: cruisingfoiler@yahoo.com.au
Reply via web post • Reply to sender • Reply to group • Start a new topic • Messages in this topic (6)

.

__,_._,___

Deleted: Rudder 2m.jpg
You deleted an attachment from this message. The original MIME headers for the attachment were:
Content-Type: image/jpeg
Content-Disposition: attachment; filename="Rudder 2m.jpg"
Content-Transfer-Encoding: base64

Deleted: Rudder sections.jpg
You deleted an attachment from this message. The original MIME headers for the attachment were:
Content-Type: image/jpeg
Content-Disposition: attachment; filename="Rudder sections.jpg"
Content-Transfer-Encoding: base64

Deleted: Rudder 4m.jpg
You deleted an attachment from this message. The original MIME headers for the attachment were:
Content-Type: image/jpeg
Content-Disposition: attachment; filename="Rudder 4m.jpg"
Content-Transfer-Encoding: base64