posted 12-19-2009 12:19 PM ET (US)        

First and foremost is the sinking of this expensive and premium brand yacht that stands out. As owners of Boston Whaler boats we often forget the peril of sinking. I truly believe that the unsinkable nature of the Boston Whaler boat is its greatest feature. At the same time, I think this often goes unspoken. As Whaler owners we tend to overlook the benefit of the enormous reserve floatation we have in our boats.

Secondly, the Bertram Yachts boat was built using foam-cored laminates. Construction of conventional hulls with foam-cored laminates has become common, yet there are still those who doubt the integrity of the structure. The massive damage suffered by this particular yacht seems to be linked to problems with its foam-cored laminates, particularly with loss of bond between the foam and the cloth laminates. In general these are problems of secondary bonds. The Boston Whaler Unibond hull has a primary bond between its foam and laminate components, as they cure together into a single structure.

Third, in a curious coincidence, I believe that the current president of Bertram Yachts is Mike Myers, the former president of Boston Whaler and former president of Brunswick Saltwater Boat Group. Mike Myers has been quoted in the discussion regarding the sinking of the Bertram Yachts boat.

A fourth connection--really just a gossamer wisp of thread--occurs between the CURD buoy company--who made the buoy which the boat is suspected to have hit--and CONTINUOUSWAVE. Promotional material from CURD's website uses a photograph originally published on CONTINUOUSWAVE in 2001. I emailed them to ask about the astonishing similarity of this image, but haven't heard back.

In any event, with all these connections, I will point readers to www.yachtforums.com for a look at what can happen to non-Boston Whaler boats at sea (and how it reinforces the benefit of the unsinkable boat), what can happen to foam-core laminate construction with secondary bonds compared to Unibond, and what can happen to former presidents of Boston Whaler.

If anyone has follow-up comments, please limit them to the three areas I mention above. I don't want to get into a discussion of the Bertram Yacht sinking itself. If you want to join that discussion, register at YACHTFORUMS.COM and join the fray.

posted 12-19-2009 05:25 PM ET (US)            

Whaler's Unibond and the core construction like the Bertram used are two different animals, and it remains to be seen how big Whaler can go with the Unibond method.

I have never been a fan of cored hull construction. It seems to me that it's a high-tech trade off to save weight and labor with vacuum bag and resin infusion.

We know there are 50-year-old Pearson Tritons still sailing, but they were resin rich and heavy. Tritons have taken severe beatings and keep on going.

I know of a new 36' cored hull sloop that fell of its jack stands and was considered a total lost due to the repair difficulties.

I do not want to be the one the goes to sea in the newest and lightest boat.

That is the second Bertram I've read about with substantial damage. Is it true?

posted 12-19-2009 10:10 PM ET (US)            

Some answers he gave to questions (2001) form Boat US. He is brilliant don't you think.

In your opinion, what is the future of outboard propulsion?
The outboard engine category continues to be strong. They are practical because they can be trimmed up for shallow water access or fully trimmed out of the water if the boat is left in the water for extended periods. And they are much easier to replace than an inboard or inboard outboard engine. And now that they are making quieter, more fuel efficient outboards, we'll probably see more people considering outboard propulsion in the future.

posted 12-20-2009 01:05 AM ET (US)            

I really would not expect a 63 foot boat to sink after hitting an SC reef buoy. But, who knows.

posted 12-20-2009 02:20 PM ET (US)            

Is it simply too expensive to make a 63 foot boat unsinkable, or is there a point (from a footage perspective or "sheer mass" perspective) where it just wouldn't work?

posted 12-20-2009 03:47 PM ET (US)            

The Boston Whaler Unibond technique requires molds which can resist the force of expanding foam (in order to create a higher density of foam). The force is proportional to the surface area and pressure, and, as the boat becomes bigger, the forces increase. A mold for making a Unibond hull 63-feet long might have to be so strong it would be unworkable.

posted 12-20-2009 08:04 PM ET (US)            

Frankly, the purpose of the foam is 1) to provide buoyancy and 2) to provide separation of the fiberglass shells - which significantly improves the bending strength of the structure. Any additional strength provided by the foam itself is insignificant - as the yield stress of foam is - well - close to ziltch. The strength of the "unibond" construction is due to the separation of the fiberglass shells - as provided by the foam. Previously, I have compared the BW unibond structure to an "I" beam - quite similar - where the foam does the same thing as the web on the "I" beam and the bending loads are taken by the fiberglass shells ("I" beam flanges).

The foam does not enter into the picture regarding penetration - as that resistance/support is solely dependent on the structure and thickness of the fiberglass. One can easily dent foam with your thumb - not much compressive strength there.

And I would bet that BW in their design does not consider one of their boats hitting a piling or other object at any speed.

The pressure of the expanding foam, by itself, does not materially improve the strength - but significantly increases the density of the foam - which improves the buoyancy of the structure. A lesser density foam will "hold" water if the region is penetrated. Further, with the increased pressure, albeit small, the foam will be expanded to completely fill the cavity up to the top of the gunwales - a lower pressure does not provide this feature.

And Rich - 50 years ago, the high stress levels of fiberglass was known and the structural integrity was known - as it was used in very significant applications. What was not known - was how much abuse it would take - as fiberglass is a brittle material. And as far as using too much glass - that is true - as fiberglass is very light - and well - "when in doubt, build it stout". And I don't doubt for a minute that a 25' Bertram with a 1 inch thick bottom was heavy. But I suspect that the thickness of BW boats has not changed much since their first design - however today's computer design capability of many manufacturers has undoubtedly had some effect that way. --- Jerry/Idaho

posted 12-20-2009 11:11 PM ET (US)         

The only downside of the whaler construction over conventional single skin layup and stringers is its less resistance to point loads as the inner and outer shells being thinner than that of a single skin and the chance that the point impact occurs on a stringer.

Although the initial impact, piercing the outer skin would meet little or no resistance from the foam core.

Only when the inner skin is reached would the tensile strength of the foam and its bond on the undamaged areas would come in to play.

This probably would not be the case of core construction as the bond is not as consistent or possible as strong as the Unibond on BW.

My second observation is presuming the transom was ripped off by a massive intake of water hitting the transom, would a whaler handle this better.

I’m not convinced it would under the same conditions
Firstly the main strength/support of the transom would be at the port/starboard joint. Most larger boats already have lost 50% of this by having a transom gate and so leaving most of the transom as a simple cantilever up from the deck.

I think also on some hulls the transom is a separate moulding and so reducing it’s strength further.

On some of the smaller hulls the transom is notched for the engine in the centre and this considerably adds to the strength. Also the classic whalers having a very low transom would fare better IMO.

I think the density of the foam would add little to the impact resistance and the deployment of the foam during the build process is a function of the chemical reaction, maybe more dense foam would expand less and so need more injection points to ensure no voids.

Jim the foam increases buoyancy when submerged as the displacement is greater than convention boats, as you note when afloat it just adds weight

posted 12-21-2009 08:19 AM ET (US)            

In the discussion at YACHTFORUMS someone mentions that the buoy under discussion was a "CURD buoy." I did not understand that term, so I GOOGLE'd it. It turns out the reference was to the company that made the buoy, CURD. The search results lead me to visit the CURD company website. As I was browsing their website I noticed a familiar image. Compare these images:

At the bottom of the page at:

http://www.curdbuoys.com/products.php#buoys

and the image in

http://continuouswave.com/whaler/reference/trailering/twoSchools.html

posted 12-21-2009 09:14 AM ET (US)            

Dave at Lockeman's Hardware and Boats sells YAR-CRAFT boats. They use a foam core laminate construction. To demonstrate the effect of the foam, they provide some samples of their hull laminate. One sample is the hull laminate without the foam layer. Another sample is the same laminate with a foam layer of about 0.5-inch in the structure. The difference in the resistance to bending of these two samples is amazing. The sample without the foam is easily deformed. The sample with the foam is impossible to deform (if holding it in your hands).

In making Boston Whaler boats, I do not think the hull or hull liner structures are ever taken out of their molds prior to being joined and infused with their foam core. It would be interesting to see how strong (or perhaps how weak) the hull structure would be if not backed by foam. The laminate is rather thin, and I wonder if it would even retain its shape once out of the mold.

posted 12-21-2009 09:43 AM ET (US)            

Was that for real and what was the out come of that?

posted 12-21-2009 02:03 PM ET (US)            

The weight of foam is very small - and insignificant relative to that of water. Generally, I would not be surprised that BW ignores the weight of foam - but then, fiberglass is not very dense either.

The laminate sample illustrates the benefits of separation of the shells. Their 1/2 inch separation is "amazing" - but now, consider the strength of a similar structure with a 2 or 3 inch separation, as in our boats - it will be very much stronger. And remember - this strength is only the bending strength - and does not improve the tension or compression strengths.

I would be surprised if the "shells" are removed from their molds prior to injection of the foam - however, I do not know the thickness and allowable loading of those shells - which could be sufficiently strong to withstand some light pressure. However, this could be done if the pressure of the expanding foam was very small. Unfortunately, I did not see this process when I toured the Edgewater facility several years ago.

Indeed, denser foam has a higher compressive load than less dense foam - no question. A less dense foam contains a lot of air - which is not a good structural material. But, any strength of foam is immaterial when compared to that of fiberglass. I doubt that the strength of foam has ever been determined - forget it. And as I have mentioned before - the strength of the BW boats stems from the separation of the skins provided by the foam.

Be assured - BW uses many engineers. And further, many will have Ph.D's. In fact, my tour of their Edgewater facility was a private tour by one of their engineers - impressive and one I will remember for a long time. And with the computer aided design capability that exists today - the requisites for more knowledgable engineers is increasing all of the time. --- Jerry/Idaho

posted 12-21-2009 06:00 PM ET (US)            

A theme in the discussion about the Bertram Yachts boat that sank is a decline in quality under the current ownership and management from the original quality that gave the brand its cachet. This is a popular theme for fans of many brands where the original owner has been bought out by someone else or by a corporation. In the case of Boston Whaler I do not believe you can make a case for a decline in the quality of the brand after Brunswick took over. I think Brunswick have introduced production controls and processes that have helped Boston Whaler retain its good reputation and have expanded and improved it.

posted 12-21-2009 08:25 PM ET (US)         

As for hitting a container the boat would of had to push the container under the boat and you would of thought the removed bow section would of sheared off and hit the upper deck/cabin.

Sorry Jim in advance

The force of the impact was enough to delaminate the core construction. I think the bond strength of the BW would not of delaminated as easy but you would likely see more hull deformation being stiffer.

The downside of this is a bit like 4x4 in an accident they don’t crumple up and absorb the same as a saloon car and so impact more on the occupants

posted 12-22-2009 09:43 AM ET (US)            

The bow area of the boat was virtually destroyed. I believe Everglades hulls are foam filled between an inner and outer laminate much like a Whaler hull. What was surprising to me was that the damage shown indicated that the foam between the laminates had separated from both sides.

What was also noteworthy was that the Everglades remained afloat and the deck was not awash. A police boat towed it to a trailer launch site where it was recovered using the trailer hand operated winch.

If that boat had been sawed into two pieces I believe it would have remained afloat.

posted 12-22-2009 07:01 PM ET (US)            

"From the pics. I would say find the anchor find the answers.
It looks to me like the boat was under way at speed and the anchor was dropped. The anchor hung and drug the boat under at the same time tearing it out of the boat."

Possibly the anchor hooked the buoy and was then stretched back to the prop and was entangled, stressing the rear bulk area.

posted 12-22-2009 10:27 PM ET (US)            

Firstly, hitting a buoy of that size and weight cannot cause the massive damage seen in the photographs. And then, the buoy, if hit by the boat, would show a lot of damage.

What distance is between the buoy and the wreck?

posted 12-22-2009 10:48 PM ET (US)         

But there seems conflicting reporting that the crew were not unduly thrown around, which seems strange for so much damage.