GUNBOAT Dismasting

[Cuttyhunk]

I think the idea that any $2.5mm boat can be thought of as a couple's cruising boat is the real fantasy here. You're not likely to self insure a $2.5mm boat and even if you just have liability coverage (if you can afford this boat you are going to insist on at least liability, because you will have lots of other assets to protect and marinas demand it anyway), the insurance company is not going to let the two of you do ocean passages alone, and maybe not let you go anywhere without a professional captain aboard.

There was a Gunboat 55 at the Newport show, and even though I was there early on Friday and there was no line to get aboard, I passed it over. It's a mean, angry-looking boat. I like friendly-looking boats for cruising. I can't imagine dinghying over and inviting them for a drink. I'd expect to be greeted with Uzis.

[Imprezza72]

Originally Posted by Cuttyhunk

I think the idea that any $2.5mm boat can be thought of as a couple's cruising boat is the real fantasy here. You're not likely to self insure a $2.5mm boat and even if you just have liability coverage (if you can afford this boat you are going to insist on at least liability, because you will have lots of other assets to protect and marinas demand it anyway), the insurance company is not going to let the two of you do ocean passages alone, and maybe not let you go anywhere without a professional captain aboard.

There was a Gunboat 55 at the Newport show, and even though I was there early on Friday and there was no line to get aboard, I passed it over. It's a mean, angry-looking boat. I like friendly-looking boats for cruising. I can't imagine dinghying over and inviting them for a drink. I'd expect to be greeted with Uzis.

I believe that was Rainmaker and there is a video of their passage there from NY

https://www.youtube.com/watch?v=P0PA-tpzVUM

[downunder]

Originally Posted by Jon Eisberg

When I saw RAINMAKER in Newport and Annapolis, I wish I'd had a closer look at that whole "longeron" arrangement. I must confess, I'm having a bit of difficulty following what that's all about in the technical discussions about it over on SA...

However, it seems apparent that in the event of a dismasting, the fact that it's no longer supported by the rig could present a serious liability when motoring into any significant seas... So, even if RAINMAKER's props had not been fouled, it seems likely that she still might not have been able to effect a self rescue, by attempting to motor back into Beaufort Inlet against any significant wind and sea...

One of the more interesting tidbits dropped by Mr Johnstone, is that the boat did have the use of her engines after the rig was jettisoned, and lines were wrapped around the props AFTER the rig was "cleared away"...

Oooops...

First thing that occurred to me when I read that one, I was reminded of Bill Belichik 'throwing Tom Brady under the bus' during his first "Deflategate" press conference...

:-)

Not sure why the longeron would be an issue motoring when not supported by the rig.

This M & M design is even more radical and I can't believe that losing the rig would make it dangerous motoring in heavy seas. If so the structure would be inadequate in any circumstance.

http://www.morrellimelvin.com/shootingstar/gallery.html

[44'cruisingcat]

Originally Posted by donradcliffe

I think you are right on any mast which can pump forward in the middle. In a mono, the solution is easy--put the runner on. On a GB, knowing what I know today, I'd rig a temporary runner from the spreader to the stern.

It can be done easily and permanently. Just add lower shrouds, from the spreader base to the original chainplates.

The only downside is it hinders going forward slightly.

[Jon Eisberg]

Originally Posted by downunder

Not sure why the longeron would be an issue motoring when not supported by the rig.

This M & M design is even more radical and I can't believe that losing the rig would make it dangerous motoring in heavy seas. If so the structure would be inadequate in any circumstance.

MM50 Shooting Star Photo Gallery - Morrelli & Melvin | Multihull Design * Engineering * Brokerage

Well, this is the exchange on SA that caught my eye... According to the guy who's supposedly writing the 'report', it would have presented a problem...

Emphasis is mine:

zzrider, on 17 Feb 2015 - 1:05 PM, said:

MR.CLEAN, on 17 Feb 2015 - 12:38 PM, said:The longeron was supported enough to not fall in the water, but it would have made motoring into any sea state a problem. I only know because that's the paragraph I just edited after breakfast.

Gotcha. Thanks for that Clean, look forward to the finished report.


This seems to point out a fundamental design flaw with this particular boat, yes? If you lose the rig, you also essentially lose the ability to motor thanks to that huge water scoop you now have between the bows, unless you also go out and cut away the longeron. Presumably there is going to be a sea state to contend with if you just lost the rig.


PLEASE SAY A PRAYER FOR RAINMAKER'S CREW - Page 6 - Multihull Anarchy - Sailing Anarchy Forums

[downunder]

QUOTE
"This seems to point out a fundamental design flaw with this particular boat, yes? If you lose the rig, you also essentially lose the ability to motor thanks to that huge water scoop you now have between the bows, unless you also go out and cut away the longeron. Presumably there is going to be a sea state to contend with if you just lost the rig."

Definitely a design flaw if correct.

[Polux]

Originally Posted by donradcliffe

I think you are right on any mast which can pump forward in the middle. In a mono, the solution is easy--put the runner on. On a GB, knowing what I know today, I'd rig a temporary runner from the spreader to the stern.

Yes, sailing hard and fast on very short and steep seas, with the pumping motion associated on the mast, is the most dangerous situation in what regards breaking it. On my boat manual it says specifically that if the boat is to be pushed and hard sailed (raced) on that particular situation running stays should be used.

[beiland]

Originally Posted by Going Walkabout

Jon, I'm one of those who mentioned the wave crashing over the front and then the mast came down. I carefully read every quote I could find from the Coast Guard. This piece of information is amazing and so very important. I am sure that since the helo arrived after the event the Coast Guard Officer didn't make this up but was told about the large wave and the mast then splitting in half by someone from the Gun Boat.

I find it very strange indeed that all of the crew making self serving statements on SA (another site) have not mentioned a word about this. I think an eyewitness account fresh at the time of the incident is worth a great deal more than clever sanitised versions that come out later.

The problem I am having with this explanation is that we are told it was a 'white-out' squall that occurs as the mast fails. From that are we to believe that this sudden BIG squall occurs exactly at the time of this BIG wave? ...not likely they occurred at the very same time, in my opinion. And if this was a white-out squall, how did a crewmember really determine it was a wave that took the mast out?

I really believe we are going to have to examine the forces exerted on this mast design in more detail to find a more plausible explanation. Just briefly consider the forces exerted by the head of that triple reefed mainsail that gets hit by a 60-70 whatever squall, and where along the 'unsupported lower panel of that mast it exerts its force, (does anyone have a dwg showing the various sail plan configurations?). Then remember what's holding up this reefed mainsail....the halyard all the way to the masthead, and likely a 2-part halyard,...even more compression force to a mast that is being forced out-of-column by the mainsail's headboard down low.

In concession I must say that Nigel Irens has been designing a LOT of similar mast for ocean racing multihulls. And I would certainly give him the benefit of doubt as to having designed it wrongly.

I have done a fair amount of investigating into mast loading details as a result of some of my unusual rig proposals. I do not profess to be an expert at all, and particularly at my older age and associated memory problems. But I will try to find time to go thru this subject thread I started long ago and recall more details associated with these problems:

Sail Loading on Rig, Rig Loading on Vessel

[beiland]

To those posters that are debating this issue, I would submit that in the multihull vessel we tend to favor the opposite of what monohulls do,..we tend to find it safer to fall off.

That said when we are confronted with a VERY sudden blast of air, we don't always recognize from what direction that air comes from. And then we have to formulate the proper response, and then it takes some time for the vessel to actually start the maneuver,...all precious moments that the vessel and the rig can experience very hi loads.

[beiland]

Originally Posted by beiland

.... But I will try to find time to go thru this subject thread I started long ago and recall more details associated with these problems:
Sail Loading on Rig, Rig Loading on Vessel

I was just reading thru that subject thread a little, and ran across this posting....

Originally Posted by brian eiland

Thanks Tony for that posting. Now can we go a bit further and see how Pierre Gutelle treats the subject of getting the rigging loads to the vessel??
________________________________
I was looking thru some misc materials I had saved on the subject, and thought this might make an interesting addition to the thread. To give proper credit, this was contained in an article by Jim Taylor for a Feb issue of SAIL mag:

Stresses, strains, and bent boats
The primary loads on a typical sailboat hull result from having to resist not only the forces exerted below the waterline by a heavy ballast keel, but also those exerted above it by the mast and sails. These loads can often be measured in tons…many tons, in the case of an IACC boat. A how and arrow can he a useful illustration of the rig loads on a sailboat hull (Fig. 1). When the arrow (mast) is drawn back, the bow strings (headstay and backstay) are tensioned, and the bow (hull) bends. All boats with fore-and-aft rigging bend to some degree; the only question is how much. Starting with the rig relaxed, a stiff boat might have thousands of pounds of backstay tension and minimal headstay sag after swallowing 6 inches of permanent backstay length. A more flexible boat can swallow that same backstay length but can have a sagging headstay with jammed cabin doors, slack lifelines, and a shortened waterline.

A boat’s hull and deck can also be viewed as a combination of I-beams loaded near mid-span (Fig. 2). The headstay and backstay pull up on the ends of the fore-and-aft beam, which is pushed down by the mast. In order for the I-beam to bend, its lower flange (the bottom of the hull) must get longer, while its upper flange (the deck) must get shorter. This means the lower parts of the hull will he stretched in tension, while the deck will he shrunk in compression. Because IACC boats have long, shallow hulls, the stresses in these flanges are even greater. There can also be stress concentrations where the decks are cut away to create optimum working areas for the crew.

In the case of oneAustralia, my guess is that her hull failed under the tension, and it split wide open near the keel, causing her to sink like a stone. In contrast, it appears that USA 53’s deck failed in compression and that her hull bent dramatically but remained substantially watertight, allowing her to make it hack to the dock.

Static verses dynamic loads
A significant common denominator in those two IACC structural failures is that both occurred in choppy seas. The design community has a good working knowledge of the static rig and keel loads that a sailboat’s structure must bear, and it has sophisticated computer tools to model the stresses, strains, and load paths that those static forces generate. However, there are no comprehensive models for the additional dynamic loads that tall rigs, long, shallow hulls, and deep, heavy keels generate when slamming through waves. The various scantlings rules for offshore racers and empirical rules of thumb for cruisers account for these dynamic loads with arbitrary safety factors that are not based on any precise knowledge of how large these extra margins truly have to be—they are simply set high enough so that failures do not occur. The win-or-bust culture of IACC racing forces the designer to attempt to accurately quantify all of the loads, static and dynamic, in all the wind and sea conditions a boat may face. Unfortunately, bitter experience is still sometimes the best teacher.

Is carbon the culprit?
Absolutely not. In fact, the trickle-down of carbon-fiber composites from the aircraft industry has allowed a variety of lighter, stronger, stiffer solutions to boatbuilding problems. It is important to understand carbon’s strengths and weaknesses. A material’s properties can be characterized by locating it on a conceptual properties scale—with elastic-and-tough materials at one end and stiff-and-brittle ones at the other. Broadly speaking, elastic-and-tough materials deform relatively easily under load but can absorb a great deal of energy without failing. The materials at the stiff-and-brittle end of the scale do not stretch or compress as much under the same loads, but are not as forgiving in absorbing the energy of impact or shock loads.

Over the past 25 years, the materials that make up all components of a sail— boat have undergone a dramatic shift from the elastic to the stiff end of the scale. This has set in motion a continuous 'find the weak link' design loop. This shift began when Dacron sails gave way to Mylar and Kevlar, exposing sheets and halyards as too stretchy. As running-rigging technology improved to keep up, deck hardware began to both march across the deck and come to pieces. When the decks were locally reinforced and the hardware was beefed up, flexible hull structures were exposed as inferior to stiffer ones. In each cycle around the loop, the use of stiffer, less-elastic materials has proved to be faster, but what has been lost is the shock-absorbing effect of all those previously elastic elements.

Carbon-fiber composites definitely fall at the stiff-and-brittle end of the scale. They can be used to form exceptionally light and stiff structures, but they are not effective in absorbing shock loads. The micro-engineering required for a carbon laminate to withstand the readily quantifiable static loads is straightforward. The macro-engineering needed for them to with stand the less accurately known shock loads encountered in a seaway is geometrically more complex.

The IACC structural failures do not mean that contemporary composite boats are globally suspect. The designers are not idiots, and the boatbuilders are doing a better job now than they have ever done. Scantlings rules have been very effective in promoting safety and maintaining reliability in the fleets that they control. The Americas Cup is simply a unique event that places a special premium on cutting-edge design development and technology with as few rules constraints as possible. These incidents show that we still have much to learn and that the process may he more difficult than we ever imagined.

Jim Taylor has been creating racers and performance cruisers since 1978 from his design off/ice in Marblehead. Massachusetts.

[GoingWalkabout]

Originally Posted by neilpride

Then according to the CG dude this is getting more clear to me, no lowers, DW fast and seconds later stop dead in the wáter , mast snap in 2 pieces and game over, is not even a Gun Boat flaw or whatever, it happen at monos to with CF mast or Alu, there is obviously a lack of midle support in RM mast, 2 lowers and maybe would be talking about a diferent isue..


Lesson learned , dont sail to fast against step seas....my 2 cents.

If it is as you say then of course it IS a Gun Boat flaw. It is their vessel. They approved ALL design elements.

[GoingWalkabout]

Originally Posted by neilpride

Then according to the CG dude this is getting more clear to me, no lowers, DW fast and seconds later stop dead in the wáter , mast snap in 2 pieces and game over, is not even a Gun Boat flaw or whatever, it happen at monos to with CF mast or Alu, there is obviously a lack of midle support in RM mast, 2 lowers and maybe would be talking about a diferent isue..


Lesson learned , dont sail to fast against step seas....my 2 cents.

If the mast came down because of poor design of course it IS a Gun Boat problem.

[neilpride]

Originally Posted by GoingWalkabout

If the mast came down because of poor design of course it IS a Gun Boat problem.

Its a Hall Spar problem, GB dont design mast not even build it, thats why you have spar makers, they design a rig for you , Gun Boat cant send the exactly especifications to Hall Spar , is obviously Hall Spar the boss when they design the rigging , mast, spreaders etc...who choose to go with a single diamond spreader set and no lowers? Hall Spar ....

[Palarran]

I guess that's the difference between a pro and amateur then. Pro's when hit by a squall close reaching head down wind and amateurs turn into the wind. Pro's blow their main to drop it while turning back into the wind and amateurs don't get caught in that situation. Pro's sail weapons and amateurs sail troop transport ships. I'm pretty comfortable staying an amateur.

[leftbrainstuff]

Originally Posted by Jon Eisberg

One thing that really had me wondering about soma's account posted on SA and above, is it sounded to me like it presented a great risk of an accidental gybe, which could be catastrophic in such a situation... Another poster followed up with the question of whether he was practicing "leech feathering" in that situation... Needless to say, there was no response given... ;-)



Agree, that seems a very likely scenario, to me... Especially, given Mr Johnstone specifically mentioned the "large South swell" they were running into, making the conditions particularly boisterous...

Perhaps I've missed it, but one question I'm a bit surprised that hasn't been given a more attention, is the role that RAINMAKER's "wave piercing" bows might have conceivably played in the accident... With the loss of the Alpha 42 last year, that was a much-debated aspect of the design, and how it might have contributed to being punched by that wave...

Much earlier in this thread, I questioned someone who had made a reference to a heavy wave strike over the bow being the cause of the dismasting... A cite for that reference couldn't be found at the time, and I never came across one in print... However, turns out that poster was right (my apologies, I've forgotten who it was):

Could be just me, but I've never understood the appeal of a "wave piercing" bow on a boat designed to be an offshore passagemaker... None of the higher bows on most of Gunboat's older models would be considered 'bluff', by any means, but for a boat intended to be taken offshore, they sure look a lot better to my eye...

The wave piercing hull is a common design outcome for power boats trying to beat the sail boat circumnavigation records.

Wave piercing offers comfort, speed and fuel consumption benefits. (at least during the modeling phase) A caveat is having a clean deck. Anything with a mast cannot be considered a clean deck.

Why would a wave piercing hull be a desirable feature on a cruising sailboat? Reserve bouyancy, the opposite of wave piercing, is a well understood benefit. (I'm an engineer but can't think of a practical hydrodynamic benefit)

Longer waterline length for speed and marketing spring to mind but these are racing concepts.

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