What's New?
  For Sale
  A History
  Email List
  Members Only
  Marine Weather
  Local Weather
  Contact Us

Mast Pumping


February 10, 2009

Greg Johnson, Moondance, Yankee # 85 and your webmaster, Marionette, Marscot/O'Day #12 had an exchange on The Forum's Technical Section regarding Dolphin mast pumping that may be interesting to others. If and when more information comes in on this subject we will add it here.


Dear Dedicated Dolphinites,
A friend helped me tune my rigging and all seems well when sailing, however  on bare poles when the wind is blowing  the mast starts pumping a bit causing a mild thumping sound you can feel and hear down below. Anyone else experience this problem? My friend says it is normal on some boats. Any suggestions?

Capt. Thumper (Greg - #85)


Hi Greg
I have had fore/aft mast pumping happen on my boat, O'Day # 12, in strong breezes. We have only one set of lower shrouds and they are in line with the uppers. Setting up mast prebend on a telephone pole type mast like mine is problematic. On Yankee Dolphins there are 2 sets of lowers set fore and aft of the mast centerline, and presumably a lighter mast section, so setting up some prebend is a lot easier and should help. This will also flatten out the mid section of the main a bit, usually a good thing for sail performance especially if you have an 'older" main. Probably about 2" prebend. If you have been thinking about a new main you can get your sailmaker (hopefully one experienced with Dolphins) to look at your rig and get some professional advice on mast tuning.

For boats rigged like mine a baby stay could be set up that should stop the pumping and that is what I am considering. The plan would be to reinforce the topping lift block and fastenings and use one of the high strength synthetics as a halyard. In heavy breeze conditions this halyard would serve as a baby stay by being snap shackled to an eye fitting on the deck. However, that means a setting up a removable wire support below the deck fitting which would be just forward of the leading edge of the house. It would dead ended in a strong fiberglass tabbed base at the V in the hull - unclipped when not in use so it would not 'invade' the V-berth space.

Ron (Marionette, #12)


February 23, 2009

As an after thought - regarding the 'baby stay' approach discussion I should have mentioned that there may be a simple way to set this up without the hassle of setting up a support back up stay below deck for the deck fitting. It would still require, I think, beefing up the topping lift block and its fastening, and going to a low stretch halyard.

Run the low stretch topping lift halyard to a shackle made fast to the forestay fitting. This would be a hassle when sailing to tack around but not an issue if at anchor or motoring under bare poles. This might still be a reasonable solution for boats with double lowers that, for whatever reason, cannot fix the pumping problem with prebend tuning.
I wonder what a mast builder/rigger would say to this idea?

Ron (Marionette # 12)




1 [Home] [A History] [Technical] [Restorations] [Stories] [Forum]
[Members Only] [Links] [Marine Weather] [Local Weather] [Contact Us]

© Copyright 2007. All Rights Reserved.

Website Design by EasyWebCreations.com & Powered by ASP Hosting