Yes that cat heading out in Australia over the bar gets cleaned up by a big set surfs backwards for a age before the wave releases it I think that one had mini keels. Gets the next wave side on struggles with jammed rudders but headed off a few days later. Don't know if anybody has got a link to the film.
Keeping our Multihulls shiny side Up!
- Thread starter boardhead
- Start date
PIL66 - XL2
Super Anarchist
Wow.....Am I missing something here, seriously....... I challenge this theory of boards up to increase side slip to prevent a capsize...it makes no sense to use boards differently to what they were designed for........ happy to discuss.
If the cat has boards it's more performance orientated and therefore when sailing upwind you want both down as generally the boards and boats are designed to need both.... when the breeze picks up and the boat increases speed, you pull some board up a little. Every boat is different but it's all about best VMG.... When reaching boards come up more or all the way depending on speed and when running, they come all the way up.... When bare poles in survival mode then boards up.
There is no way you have time to pull the boards up in the moment. Easing sheets is the fastest way to prevent capsize.
Been there done that and learned from it
Agree Wess
If the cat has boards it's more performance orientated and therefore when sailing upwind you want both down as generally the boards and boats are designed to need both.... when the breeze picks up and the boat increases speed, you pull some board up a little. Every boat is different but it's all about best VMG.... When reaching boards come up more or all the way depending on speed and when running, they come all the way up.... When bare poles in survival mode then boards up.
There is no way you have time to pull the boards up in the moment. Easing sheets is the fastest way to prevent capsize.
Been there done that and learned from it
The story of the catamaran Ramtha during the infamous Queens Birthday Weekend Storm in the South Pacific is one the best (if not the best) example of bare poles catamaran stability.
A difficult choice but probably the crew were safer to stay onboard than risk the transfer to the ship.
The ship, the HMNZS Monowai, is by the way 295ft long and 3900 tons displacement, but compare the motion with little 38ft Ramtha.
Ramtha was eventually recovered, still floating, and still upright, and returned to cruising.
www.rutgerson.se
pangolin.co.nz
The HMNZS Monowai and Ramtha footage starts just after 52m30s
(click through to YouTube to watch - the video works, it just can't be embedded)
A difficult choice but probably the crew were safer to stay onboard than risk the transfer to the ship.
The ship, the HMNZS Monowai, is by the way 295ft long and 3900 tons displacement, but compare the motion with little 38ft Ramtha.
Ramtha was eventually recovered, still floating, and still upright, and returned to cruising.
The Queen's Birthday Storm - Rutgerson Marin
www.rutgerson.se
Queen’s Birthday Storm | Pangolin.co.nz
pangolin.co.nz
The HMNZS Monowai and Ramtha footage starts just after 52m30s
(click through to YouTube to watch - the video works, it just can't be embedded)
El Borracho
Barkeeper’s Friend
Sorry, my statement too general. Wind abaft the beam. (A likely angle with boards up?)
Keith
Super Anarchist
I followed the recommendations of Gavin Le Sueur , from his book, multihull seamanship....
Great advice, from a seasoned racer and family cruiser.
Great advice, from a seasoned racer and family cruiser.
boardhead
Anarchist
- Thread starter
- #27
So - I respect your skepticism PIL66 but out of interest, where were the boards when XL2 went dull side up and were you close or deep reaching?
I know you view the new bows as a serious improvement but would they have saved the day under the same circumstances?
I know you view the new bows as a serious improvement but would they have saved the day under the same circumstances?
Kenny Dumas
Non Binary About Anything
Maybe the side slip speed matters relative to the wave speed more than wind speed? Effectively stretching the wavelength from the boat’s reference frame?
PIL66 - XL2
Super Anarchist
my boards were fully up as we were running with a kite.... Yes the new bows would have saved me as we teetered on the edge.... my capsize is simply pushing too hard with too much sail.
Any boat designed to have boards down when sailing upwind will suffer bad VMG if you lift a board... makes no sense at all.....Fujin and any performance boat will reduce sail, not pull a board up............... However you could design bigger (cord) boards and only ever use one.
Wharrams have no place in this conversation.
I think lifting the boards was a suggestion for when you had run out of ideas and where just hanging on, obviously if your trying to sail to windward then you need the boards or board if they are asymetric to be down. If faced by a dangerous lee shore slowly clawing to windward with reduced sail would be a wiser tacktick than lying ahull. I was suprised how well the boat behaved slowly sailing upwind on the point of luffing in some really rough weather, just luffing a bit more in the big gusts.( my boat is designed to have both boards down upwind and they were) Had I tried to run downwind it would have been a pretty wild ride for sure. Like everything there are no real hard and fast rules just a load of tools in the toolbox it's a matter of choicing the right one at the right time.
Pinching in gusts while going upwind with both boards down is a reasonable strategy. In fact not having the boards down can make it harder as you might have lee helm, which in gusts may turn you sideways.
If you've on a reach though, and don't need to maximize upwind vmg, having the lee board up does provide an automatic release in gusts that take the windward board out of the water as well. You can carry a bit more sail this way and go faster.
A peek into Fujin's playbook would indeed be interesting.
If you've on a reach though, and don't need to maximize upwind vmg, having the lee board up does provide an automatic release in gusts that take the windward board out of the water as well. You can carry a bit more sail this way and go faster.
A peek into Fujin's playbook would indeed be interesting.
PIL66 - XL2
Super Anarchist
When reaching in breeze, both boards should be up.... speed will eliminate side slip
bushsailor
Anarchist
I think on any cruising boat the boards up thing would not do much at all. A light round hull day boat maybe but why would you try and get the boat to slip sideways down a wave anyway? The rudders are going to stop the stern from side slipping so all that will happen is the boat will dramatically bear away and power up more.
On most good sailing cats they can go upwind quite well with a balanced sail plan without boards down.
I would think if you get caught in a heavy storm a deep reef in the main and storm jib hard on the wind going forward at 2kn would be the best or a sea anchor off the bow and bare poles but the attachment points for the sea anchor tend to have a really hard time as the rode snaps tight with the waves.
Heaving too with the jib on the opposite tack also works well but the boat is sitting 45 degrees to the wind with no forward momentum which may be bad in say 8m plus breaking seas.
One other thing the longer the bows and the further back the mast is the less likely a pitch pole will occur.
Generally the autopilot will lock the rudders up if required.
On most good sailing cats they can go upwind quite well with a balanced sail plan without boards down.
I would think if you get caught in a heavy storm a deep reef in the main and storm jib hard on the wind going forward at 2kn would be the best or a sea anchor off the bow and bare poles but the attachment points for the sea anchor tend to have a really hard time as the rode snaps tight with the waves.
Heaving too with the jib on the opposite tack also works well but the boat is sitting 45 degrees to the wind with no forward momentum which may be bad in say 8m plus breaking seas.
One other thing the longer the bows and the further back the mast is the less likely a pitch pole will occur.
Generally the autopilot will lock the rudders up if required.
Kenny Dumas
Non Binary About Anything
A key tool for safety is to measure near misses in addition to actual accidents. Maybe a smart boat should tell you how often you almost capsized, or from a process control reference, whether you are within the control limits?
boardhead
Anarchist
- Thread starter
- #35
Getting a bit bogged down theorizing about whether or not lifting the lateral resistance clear at a serious heel angle on a catamaran will allow the boat to slide out from under and escape capsize - fact is that some contributors here are aware of this phenomenon and their experiences are exactly what this thread is seeking!
It may not work on all types - heavy platform/ light rig with a more forgiving stability curve (read older designs) would likely survive while lighter platforms/taller and heavier rig (newer designs) may not but the concept is something to be aware of and obviously news to some readers.
Does anybody here have a stability curve for their own boat? How about righting moment numbers and how they relate as to when it's time to reef and how deeply to reef. Perhaps if that kind of information was made available, particularly on higher performance boats, sailors might be more aware of when they are getting into dangerous situations.
Capsize may occur laterally, diagonally, longitudinally foreword or even backwards by either wind, wave or a combination of the two. Depending upon how and where you intend to sail and an understanding of your particular multihulls strengths and weaknesses would surely help avoid a capsize.
It may not work on all types - heavy platform/ light rig with a more forgiving stability curve (read older designs) would likely survive while lighter platforms/taller and heavier rig (newer designs) may not but the concept is something to be aware of and obviously news to some readers.
Does anybody here have a stability curve for their own boat? How about righting moment numbers and how they relate as to when it's time to reef and how deeply to reef. Perhaps if that kind of information was made available, particularly on higher performance boats, sailors might be more aware of when they are getting into dangerous situations.
Capsize may occur laterally, diagonally, longitudinally foreword or even backwards by either wind, wave or a combination of the two. Depending upon how and where you intend to sail and an understanding of your particular multihulls strengths and weaknesses would surely help avoid a capsize.
Both the Wharram and Kelsall sites have stability formula's. I used the Wharram site's and just made a table using all the various sail combinations. It suggested first reef at 15kts and it's worked out fairly accurate as the boat speed really drops but she feels a lot tamer.
I found a Gunboat one supplied to owners it has tables for upwind,reaching and broad reaching. Included are min and max aws, sail combination, daggerboard position, jib sheeting angle, min and max awa and target twa. The broad reaching one has max tws and is for use between a twa of 130 to180 degrees.
So pretty comprehensive, I think they are all linked to load alarms now which alert you when certain paramaters are met. I think as the boats get bigger it's harder to judge when you are maybe pushing a bit too hard, on smaller lighter boats it's more obvious.
I found a Gunboat one supplied to owners it has tables for upwind,reaching and broad reaching. Included are min and max aws, sail combination, daggerboard position, jib sheeting angle, min and max awa and target twa. The broad reaching one has max tws and is for use between a twa of 130 to180 degrees.
So pretty comprehensive, I think they are all linked to load alarms now which alert you when certain paramaters are met. I think as the boats get bigger it's harder to judge when you are maybe pushing a bit too hard, on smaller lighter boats it's more obvious.
yes please?Care to share a copy with the rest of us please?
