Microbursts and Multihulls

[maxingout]

I just read an article about a microburst striking SV Concordia off the coast of Brazil. The vessel is 188 feet long, and had at least forty high school and college students on board. The microburst knocked the vessel down pinning the sails to the water, and in fifteen seconds they had to abandon ship as it was taking on water and sinking. Everybody made it into liferafts, and all were rescued.

Here is the question. Do you know of any instances of a microburst hitting a multihull sailing offshore when not racing, and if you do, what was the outcome?

[maxingout]

The Canadian Press: Captain of floating university: Sudden 'microburst' knocked ship onto side off Brazilian coast

This is a link to an account of the microburst and sinking of SV Concordia.

Additional comment:

I am not so much interested in the behaviour of an overcanvassed multihull in a race during a microburst. I know the multihull will probably flip. I am interested in the behavior of a cruising multihull in a microburst.

Do you know of any cruising multihulls offshore caught in microbursts?

[clockwork orange]

Dave ,i dont know if it makes much difference if the multi is racing or cruising,any amount of sail is over canvassed if it catches you unawares,we get these things on the great lakes which i would have to call microbursts where you have very light winds and have lots of sail up,then you see this big black wall comming at you and you scramble to get everything down and secured before you get whacked by instantaneous 70 knots,a few minutes later its dropped to 30 or so and you get reefed sail up and plug on.I looked at buying a racing cat that flipped with loss of 2 souls in one of these that struck them at night,they probably never saw it comming, i dont know what sail they had up but main and working jib would have been too much,would a cruising cat have fared better,i dont know,probably more stabilit due to more weight and less sail area.Ive been in 2 of these things, the first in a 24ft uldb i designed and built and we were racing,i had never seen one before and we were a bit late getting the sails down and were knocked down with the mast in the water,we waited it out,reefed,changed to the self tacker and completed the race,no water down below due to the open transom so no real danger,im sure we were down for several minutes,other boats were taking water down the companionway. The second time we were cruising on a 34ft we had built ,this time we recognized it and got everything down in time and the engine running but still ended up with the mast in the water and a stray sheet around the prop.
Steve.
.

[maxingout]

Originally Posted by clockwork orange

Dave ,i dont know if it makes much difference if the multi is racing or cruising,any amount of sail is over canvassed if it catches you unawares,we get these things on the great lakes which i would have to call microbursts where you have very light winds and have lots of sail up,then you see this big black wall comming at you and you scramble to get everything down and secured before you get whacked by instantaneous 70 knots,a few minutes later its dropped to 30 or so and you get reefed sail up and plug on.I looked at buying a racing cat that flipped with loss of 2 souls in one of these that struck them at night,they probably never saw it comming, i dont know what sail they had up but main and working jib would have been too much,would a cruising cat have fared better,i dont know,probably more stabilit due to more weight and less sail area.Ive been in 2 of these things, the first in a 24ft uldb i designed and built and we were racing,i had never seen one before and we were a bit late getting the sails down and were knocked down with the mast in the water,we waited it out,reefed,changed to the self tacker and completed the race,no water down below due to the open transom so no real danger,im sure we were down for several minutes,other boats were taking water down the companionway. The second time we were cruising on a 34ft we had built ,this time we recognized it and got everything down in time and the engine running but still ended up with the mast in the water and a stray sheet around the prop.
Steve.
.

When you got hit by the 70 knot winds, did you feel the chill of cold air before the full force of the microburst hit?

I've been sailing many times and felt the chill of the high altitude cold air coming my way before the full force of the wind hit. Whenever I feel the cold air, I take my sails down.

[Zednotzee]

Originally Posted by maxingout

When you got hit by the 70 knot winds, did you feel the chill of cold air before the full force of the microburst hit?

I've been sailing many times and felt the chill of the high altitude cold air coming my way before the full force of the wind hit. Whenever I feel the cold air, I take my sails down.

You may be interested in this article, from the Great Lakes Alberg Association newsletter-

The Great Lakes Alberg Assoc.

From his account, the only warnings were visual & a shift in wind direction. One (fully canvassed) boat was sunk.

[Palarran]

Originally Posted by clockwork orange

we get these things on the great lakes which i would have to call microbursts where you have very light winds and have lots of sail up,then you see this big black wall comming at you and you scramble to get everything down and secured before you get whacked by instantaneous 70 knots,a few minutes later its dropped to 30 or so
.

I have seen that exact storm several times on Lake Michigan. Once the black cloud was only maybe a 1/4 mile high and rolling along the water. It was one cool looking front. But, I'm not sure it would be a micro-burst. I think they tend to hit when the storm is already there.

Dave, I'm wondering if you'd be interested in sharing what you think would happen if a cat was hit by a microburst. I thought I'd read somewhere that catamarans sails where designed to basically blow out if hit with to much wind. If they didn't blow out, I wouldn't think the boat would capsize as the inertia would be to great. Rigging failure?

[maxingout]

Originally Posted by Palarran

I have seen that exact storm several times on Lake Michigan. Once the black cloud was only maybe a 1/4 mile high and rolling along the water. It was one cool looking front. But, I'm not sure it would be a micro-burst. I think they tend to hit when the storm is already there.

Dave, I'm wondering if you'd be interested in sharing what you think would happen if a cat was hit by a microburst. I thought I'd read somewhere that catamarans sails where designed to basically blow out if hit with to much wind. If they didn't blow out, I wouldn't think the boat would capsize as the inertia would be to great. Rigging failure?

I have wondered many times how a microburst would effect Exit Only. We tend to sail in a conservative manner, but from what I read, any sail that you have up is too much in a microburst.

My catamaran is over-rigged for a 39 foot catamaran in my opinion. So I don't think the rigging would go in a microburst. I am very meticulous about the condtion of my rigging. My sails are 9 oz, and I never blew out a sail since the boat came from the factory. I have never lifted a hull out of the water.

I really don't know what would happen if I got hit by a microburst. Our autopilot steers the boat 98% of the time, and if we ever got him by a microburst, the autopilot would probably be steering the boat when it happened.

I guess how a microburst would affect the boat would depend to a significant degree on our point of sail, and how the autopilot responded.

If a microburst hit Exit Only when there was no sail up, I don't think there would be any problem. In every other situation, I really don't know how things would turn out.

[DotDun]

Cruising cats are heavy enough the rig will go before a hull lifts out of the water. My rig is big also, all 14mm, but the engineers at the manufacturer told me the rig would go before wind would flip the boat.

I don't want to test it!

[barnakiel]

I would be very careful with what finished off Concordia. It is not the first training ship that claims microburst. Somehow, neither Gorch Fock, nor any other of the dozen of tall ships or so had this kind of trouble. Why?

Quite recently a Polish training ship lost her sticks. Why?

b.

[John A]

There is no warning when a micro burst will occur. They're the same thing as wind shear around airports.
Its caused by a downdraft from the layer of wind that flows above the surface winds when they flow in the same direction and is the sum of the two.
A very mild micro burst is called a gust of wind.
The following was taken from a google search.
A microburst is a small, very intense downdraft that descends to the ground resulting in a strong wind divergence. The size of the event is typically less than 4 kilometers across. Microbursts are capable of producing winds of more than 100 mph causing significant damage. The life span of a microburst is around 5-15 minutes

[s/v Beth]

My family and I got caught in a microburst on Utah Lake. Even though our boat was heavily reefed, we broached but popped up immediately afterwards. The only warning we had was the whitecaps racing to us (about 30 seconds worth). About 2 minutes of pure h$!!, then picking up the pieces and going home...

[John A]

Sailing east from Panama I was in the middle of some pretty stiff winds with a full keel cutter. All of a sudden a gust of wind hit the boat and I stood in the cockpit and watched as every plastic sail slug on the main exploded! Faster than you can read this!
The main was attached by the top and bottom metal slugs.

I'd kept my old main but changing it in 15ft seas by myself took awhile, because of the double tether for the safety harness.

[Laidback]

In Which Latitudes have so called Micro Bursts been OFFICIALY recorded?

What is the difference between a Tropical Line Squall and a "Micro Burst" ?

[Blue Stocking]

When A square-rigged ship, such a Pride of Baltimore, Marques, (sunk by microburst north of Bermuda in 1984), or Concordia, are sheeted in for windward work, and are knocked flat, the sails fill with water, and the ship cant stand back up.
The sheets and braces are cleated to the submerged rail, and cant be released.
With a centreline sheeted arrangement we would have a better chance of releasing, IMHO

[GordMay]

A squall line is a line of severe thunderstorms that can form along and/or ahead of a cold front, whereas a microburst is a very localized column of sinking air.

More ☛ Microburst Handbook