So what went wrong???

If you go to peter radclyffe's post #48 and click on the youtube link (that one you can enlarge to full screen), the launch starts at 1:55 into the video.

The boat looks pretty stable once it's on it's side.

 

OK, thanks for that. Painful to watch !

 

Here's a wild guess at what went wrong.

At 1:54 on the video, there is a long arm connecting the yellow crane to the front wheeled carriage. At 1:58 you get a good view at the stabilizing fins on the side(s) of the hull and a crowd of people at the stern wheeled carriage that are sticking chocks under the tires.

At 2:23 an hour so has passed. The boat is now being let down the ramp by the crane winch and it appears to me they have taken the long arm and reversed it so it is under the boat.

There are 4 teams of people on the ramp. There is a team on port and starboard at the rear carriage, ready to throw a chock under the wheels, if needed. That's what the guy has on his shoulder, is a big wood chock.

The 2 port and starboard teams up the ramp towards the bow each have a strap/rope that is connected to the end of the long arm so they can steer the front carriage, if needed. Once they get to the waters edge, they let the ropes go and the carriage arm from then on is not under control.

Once the boat gets in the water and starts to tip, it also turns a little and the motion is a little jerky, both as it lowers into the water and as it tips over. I'm wondering if the front carriage started turning on it's own and then the arm got caught in the starboard stabilizing fin and then just levered the boat over as the boat drifted back off the carriages.

(I can't see where they have a line attached to the boat to control it once it was afloat. What was the plan there?)

If you watch the 3 winch cables on the left (which must be connected to the carriages to bring them back out once the boat was launched) (at 2:09 you can see the 2 outside cables go the aft carriage and the middle cable goes to the front carriage) you can see where they are slack and then jerked and then go slack again as the boat maybe gets tangled up in the carriages.

Like I said, it's just a guess, and even if it's valid, the boat sure didn't need much of a push to fall over to begin with.

Along with all the other questions, once the boats was afloat, how did they expect to get it back on those carriages to bring it back out, or was there another plan for it? Maybe move it somewhere else to haul it out?

 

Well, I was obviously forgetting the long twilight in the higher latitudes worrying about it being night-time !

 

The hydrostatics attached at the end of this report are incomplete.
There are no KMT values. You can't even do a simple GM calculation with this data.

 

i wonder if by the time they put enough ballast in to make it stable to tow away, the windows may be underwater,
and these windows do not look strong, the way one was removed
the other northern marine yachts look like strong boats,

i read it is now being towed with a support barge

 

I just got some local info saying the carriage somehow ripped a hole in the hull, no other details than that.

 

If you look at the lower right corner of pages 6 and 8, you'll see KMT, FT, and GMT values.

 

The builder is now (in published news stories) blaming the ramp, claiming a hole tipped the boat initially.......

 

When looking at this boat before launch, I am struck by how much it reminds me of the Florida Bay Coaster. Lots of boat above the waterline and not so much below....... Wasn't there a well publicized capsize event a few years back involving one of those too? A different boat and different circumstances, I know, but the visual similarity is there....

 

Yes, I saw the odd KMT values for the specific conditions, but when you prepare a table of hydrostatics for a range of different drafts, you want the KM and BM values for the long. and trans. directions. You've got half a hydrostatics table at the end of this report, although you could work back on the KML from some of the other numbers, you have no recourse for KMTs.

 

http://www.passagemaker.com/article...anacortes-capsize-company-lays-off-workforce/

 

According to this guy it was no accident: he got fired last December for warning of exactly what happened.

http://www.tradeonlytoday.com/2014/05/video-fears-raised-10-million-yacht-capsized/

The former project manager for the build claims that he lost his job for raising concerns about the capacity and stability of the wheeled trucks that transported the boat down the launch ramp. He was worried that they might collapse tipping the boat and it is rumored that one of the trucks had at least one flat tire when it was hauled up the ramp after the launch. He also says that he's the one behind the additional stability analysis that called for more ballast.

There is one more large build at Northern Marine which was described as mired in "legal and financial" issues in the Passagemaker report on the staff being laid off. Does anyone know what that is about? It is beginning to look like the builder might have been in difficulty and pressed on ahead regardless.....

 

I guess they could always do what the builders did on the similar length boat we chartered in the Ecuadorian Amazon a few years ago.

Very obviously it was unstable when built and so outriggers, cunningly disguised as canoe launch areas, were added. More here, scroll down.

http://sailingcatamarans.com/index....rlin-sango-strike-eclipse-pixie-janus-transit

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

This sounds like the reason mobile cranes ashore are raised up off their pneumatic tires using outriggers when they are lifting a load: when the crane has a load suspended, the tires may flex unpredictably, causing unwanted side loads to suddenly occur on the boom. The outriggers provide a more stable platform for the crane to lift the load.

It's not clear from the launch video snippets available if the forward supports under the bow of the vessel were changed after the vessel was weighed ashore using load cells. At that time, the bow was apparently resting on two load cells placed in-line under the keel on centerline, while the stern was supported by a cradle which supported the stern port and starboard of the centerline. The readings from the load cells at the stern, according to the report of Roddan Eng. showed a heavier reading to port.

In traditional launches from a slipway, a special cradle was constructed to support the bow of the vessel during the last portion of the launch, when the stern is floating and a large reaction is produced at the bow as the hull pivots. This forward support, called the fore poppet, extended up the side of the bow for an appreciable distance from the keel and helped keep the bow upright as the vessel pivoted. The fore poppet was also designed to crush during pivoting, to allow the hull to change angle with respect to the launch ways without imposing loads great enough to cause damage to the vessel.

If this yacht's hull were resting on a single point at the bow when the stern became waterborne, there is little to restrain the bow to keep it upright if, for example, the vessel is heavier to port and wants to heel in that direction, or if some unobserved fault in the slipway causes the launching cradle to shift. The yacht is essentially grounded at the bow, as if on a pinnacle, and the reaction at the point of grounding can affect the stability of the vessel. Because the vessel is not fully waterborne, grounded stability is analyzed differently from the manner of just calculating the GM, as one would do for a vessel fully floating.