Wave height vs freeboard

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c_witch

c_witch

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Dec 20, 2010
294
Yankee Condore 21 Halifax
Hiee,

I'm curious as to what conditions people feel comfortable with sailing their boats in when you are dealing with waves/swells. Our boat has about a 20'' freeboard at the stern ie vetical distance from the top of the cockpit locker to the waterline. I feel ok in conditions where the waves are 3 feet or perhaps a bit more and at least 35 feet apart crest to crest. I've neglected wind conditions here as that can be accounted for by reefing/motoring etc. I was stuck inside for most of the season as out in the open atlantic the waves were running 2 meters (6 feet) or more.

c_witch
 
Manureva

Manureva

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Jan 14, 2011
243
tanzer tanzer 28 bathurst nb
i have been in some 10 to 15 with no issue, the bigger the wave they get space longer in most situation, you just have to make sure you dont get a breaker on the beam when they are above 8 to 9 feet.
 
c_witch

c_witch

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Dec 20, 2010
294
Yankee Condore 21 Halifax
Really,

That is amazing as from the reading I've done our boat would only survive a 4' foot breaking wave beam on. Anything else is suppose to cause a 100% capsize. At 4' feet its also a guarantee'd knock down.

c_witch
 
Joe

Joe

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Jun 1, 2004
8,200
Catalina 27 Mission Bay, San Diego
I'm not sure that's how the physics of ocean waves works when compared to the freeboard of a boat. Your assumption would rule out the safety of the inflatable life raft. We sail in 6 to 8 foot seas all the time...... the boat floats over the waves. They don't break. I'd be more concerned about windspeed, bottom depth and tide conditions... than wave height.... and if the wind caused them to break.... only the tops would capsize.
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
23,050
Catalina 34 224 Maple Bay, BC, Canada
c_witch said:
I've neglected wind conditions here
Click to expand
But you simply cannot do that. Why? Because the waves have two characteristics: height and frequency.

7 feet and 20 seconds is relatively easy to deal with.

7 feet at 7 seconds is a bloody washing machine, and very uncomfortable going upwind (believe me, we did it June this year).

In addition to the swell frequency, there are often wind waves TO BE ADDED ON TOP OF THE swell height.

Also, the direction you are going in makes a BIG difference. Once we turned around, going downwind in the 7/7 was reasonable. Going upwind? That's why we turned around.

Unless the waves are breaking, your boat should float like a cork. However, the closer you are to the water, the higher the perception of danger or discomfort.

If you go to the noaa website, there should be info there are what their reports include and what each dimension means.
 
anchorclanker

anchorclanker

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May 27, 2012
1,152
Oday 222 Beaver Lake, Arkansas
Stu

Never set foot on the ocean. Have swam in it, but never been "on it". Explain turning 180 in 7/7 waves??
 
Bill1565

Bill1565

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Jan 22, 2008
1,483
Hunter 37 C sloop Punta Gorda FL
Heard a presntation last night from Lynne and Larry Pardy about 80 knot winds, 50 foot seas in a 24 foot wood boat. They survived, prospered wrote a book about storm prep.

The "break" at the top of a wave will roll you right over if it catches you on the beam. Otherwise think amusement park ride, up, down and around. Somebody already mentioned wind and distance between crests. We've been out in 10-12 footers in a MacGregor. In the trough the sails slatted while on the peak we were heeled pretty good, but the crests were a long way apart and none were breaking.
 
kpgraci

kpgraci

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Jun 12, 2010
936
Oday 22 Orleans Marina, NOLA
I've seen a formula that says a breaking wave on the beam with a height 1/3 the lenght of the boat can capsize it. On a self righting boat non breaking waves cannot capsize a boat. Sounds resonsble but I don't know for sure.
 
rgranger

rgranger

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Jan 19, 2010
12,584
Hobie 16 & Rhodes 22 Skeeter Charleston
kpgraci said:
On a self righting boat non breaking waves cannot capsize a boat. Sounds resonsble but I don't know for sure.
Click to expand
I think that is correct. When a boat is in knock down, essentially all of the heeling moment is dissipated as the wind spills out of the sail. So the boat starts to right itself. So long as a breaker doesn't roll it over it will come up. The wind knocks you down and the breaker rolls you over.

Caveat: I'm just stating what I've read, I've never been rolled over (thank God) so school me if I'm wrong.
 
W

Winkfish

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Jul 28, 2010
914
Boston Whaler Montauk New Orleans
mesange said:
and take your boat out with some experience sailor, i will get you confidence in you boat.
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Amen, Brother! I've been told more than once by experienced people (who know me) , "your boat can handle bigger seas than you can."
 
centerline

centerline

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Mar 20, 2012
3,983
Cal 34-III, MacGregor 25 Salem, Oregon
depending on how much water is breaking from the crest of the wave (determined by wave height and wind as well as other factors) the part that breaks can swamp you from either side or either end and tumble you. not that it will always, but it always has a strong potential for it. from the side, beam on, the potential is many times greater.
and as winkfish said, "your boat can handle bigger seas than you can.", is almost always so, and with a bit of experience in the rough water you will learn to be comfortable with your boats capabilities.
 
zeehag

zeehag

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Mar 26, 2009
3,198
1976 formosa 41 yankee clipper santa barbara. ca.(not there)
took an irwin citation south bound from avalon to oceanside day after an el nino winter storm in lost angeles 1994, january. seas were over 25 ft----wont do that again-not because of the seas, but because it was so difficult steering the improperly balanced fin/spade boat. didnt likeit. sailed down hill in an ericson 35--loved it--still a tad bit too much weather helm, but better than citation 37...
seidelmann 37--passable-- has lots of weather helm in th e winds and seas associated with severe tstorms off florida...... seas were not over 10 ft, but were confused, gulf of mexico seas....formosa 41 in 25ish pacific rollers --downhill---decent ride--sometimes a tad rolly--seas taller than 15 ft--not too horrible--some seas were breaking, some not--i will try to take pix when i go to zihuatenejo in a month's time......i enjoy heavy weather sailing....is a definite challenge--as my formosa needs more than 10 kts winds to steer her decently, sheis a heavy weather boat--tolerates 60 kts well....
 
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