Sails pumping in medium winds

[kingoffixin]

I have a 1987 S2 22 and it sails beautifully in light winds (less than 10 K) but when I get into heavier winds things start going crazy. It seems like the sails start "pumping" and I have very poor control of what's going on with the sails. I'm sort of an advanced-beginner sailor so my skills are not perfect by any means.
We went out racing the other day and the winds were blowing at 15-20k and we couldn't keep things under control and I decided to drop everything and head in because I wasn't comfortable that I was in control and didn't want to tear something loose. My shrouds seem to be plenty tight when I checked them with the LOOS. I have a roller furling so I'm not sure how to check the tension of the forestay.
Any suggestions on what to do so I can stay on the water when the winds come up?

 

[celticwinds]

I don`t know what you mean by sails pumping. When the winds reach 15 knots try reefing the main and shorten the headsail. Ease the traveller and mainsheet. Flatten both sails and tighten the backstay. When you start to feel in control again then you can slowly add some power with the traveller and main sheet, but keep the reef in and keep the sails flat.

 

[Stu Jackson]

Reef, reef, reef.

Even if you're racing.

 

[BobM]

Is it a CDI furler by chance? I had one on my last boat and it could oscillate like mad at times. No more flexible foils for me. I presume since you mentioned a Loos gauge that you checked your backstay tension?

 

[kingoffixin]

It is a CDI Furler. I have the adjustable back stay tensioner and I did tighten until I had what looked like a lot of mast bend.
At what point is reefing recommended?

 

[RichH]

Something is not being communicated well here, as even without reefing in a hurricane a boat should be able to be blown over to have the mast almost flat to the water ... and there shouldnt be any sails or other structure 'vibrating'/ pumping as, I think/perceiving, youre describing.

Exactly what was vibrating? ... the WHOLE rig PLUS sails, just one sail, both sails, partial sections (leechs or luffs, etc.) of sails, etc. etc. etc. From just what you described tends for me to believe that you have an 'induced harmonic vibration' thats resonating with 'something else' on your boat, etc. How much mast prebend do you have on your S2 and was that mast vibrating in sync with what you saw in the sails? Whats your average rigging % stress that you set up with your Loos?

Please try to explain in more detail what happened and what you saw, etc. including your description of the wind and how stable or unstable/gusty, etc. ;-)


Why I ask for details is that Im several hundreds of miles downwind from your location and late last week the wind (NW @ 5-25 kts. in a 10-15 second cycle) was so unstable, 'rolling' actually, and with unbelievable micro-gusts embedded and which came from each and every direction within a 120° range (W through NNE) .... I saw what was happening and decided to just sit at the dock and enjoy a few 'tinnys' instead of going out and working my arse off. Im an experienced long distance blue water sailer and when I saw how this 'unstable wind frenzy' was behaving ... I stayed at the dock.

 

[BobM]

i had the same phenomenon with the CDI and never had it since with a Hood metal foil. If you tensioned the stay, did you increase tension at the base of the luff? You need to flatten the sails in high winds by doing that and moving your genoa cars or snatch blocks aft. That being said 20 knots can be a lot for a 22 footer and reefing is called for if you cant otherwise control the bpat. What tack were you on and how big is the genoa?

 

[kingoffixin]

Thanks for all the replies. I was trying to hold it on a close reach as it seemed like that would be the least stressful on things. The "pumping" I get happens about once per second and it's hard to tell exactly where it's originating from.
I'm thinking I should go through setting all the standing rigging and make sure I have things set right. If you have a similar boat (6.9) which attachment point do you use for the headstay? There are three choices on my boat and I have it on the one that's furthest forward but it is raised slightly higher than the two aft of it.
When you set your rigging do you do it based on the percentage of breaking strength of the cable or are there other criteria you use?
Thanks again for the help.

 

[RichH]

Here's the URL of the most comprehensive rig tuning guide available on the internet and includes accurate rig tension without the use of a tension gage - just a 'meter stick'.
In this rigging manual you also note 'mast prebend'. Setting correct mast prebend is the preferred way to stop 'mast pumping'
http://www.riggingandsails.com/pdf/selden-tuning.pdf

 

[JoeWhite]

I had the pumping induced by the jib . I purchased a new jib. All is OK now. The original jib was stretched out and had lost its shape.

 

[BobM]

If the pumping is driving you nuts, recognize that it is frequency related and try changing the tension on the luff with the jib halyard. Scientifically speaking it should have an impact as the pumping is likely due to the wind being at the right harmonic to cause the foil to move like that. It is putting a standing wave into the system which it can do because it is flexible...in my opinion anyway!


http://youtu.be/-gr7KmTOrx0