Bavaria Match 42 lost its keel...

Structural questions

Thank you for the replies.
This tragic event raises several concerns. We were impressed with Bavaria's claims of a kevlar reinforced hull and steel network laid in to the glass. Shouldn't any keel be directly bolted to this? Should the tensioners also be directly bolted too?

Which builders can you trust? Who might cut corners and how would anyone know how that is defined?

How thorough should one go over a boat. I think there is an awful lot of faith that goes in to reputation. Now, I want to know more strucutral details to help shop. Any suggestions?

Should even a new boat madate a mechanical/structural survey prior to purchase as a contingency?


Thanks,
Brian and Karen

 

Just found a link to a survey of the Bavaria 42match which has lost her keel and their sister ships with similar damages around the keel area. It's been commissioned by the charter company so it's not necessarily impartitial but nevertheless very interesting. Seems to be a serious design fault as there's no connection between the keel bolts and the floor plates but just relatively small backing plates on top of the laminate which is said to be too weak (just 12mm thick).

It's German only but there are some photographs included.

Survey

 

Nemo suggested;

"I think it would be far better to put a central longitudinal stringer with a high-density core in the bolt area, to create a structural continuity with the transverse bottom frames"

That was what I have been doing for quite long time, laminating a 4 cm. thick ply allmost through the entire lenght of the strongback midships, providing a superior base for the keel bolts till I was advised to omit this and bolt the keel directly to the outer skin of the boat, by the CE authorities with a very logical argumentation: If you connect two items, any other in between will jeopardize the whole since the bolts will get longer.
Now I have 4 boats in my yard, some nearing completion, and I am wondering why I have left my old proven system. It is a mess to reinforce the whole belly of the boat once the interior is there and still you don't believe in what you are doing.

preacherman

 

The solutions below (attached sections) are commonly used. Better than the Match 42 system or CE specifications? At least some structural continuity between transverse and longitudinal frames.

Twice the hull's thickness, is that enough ? I'd extend the plates, too..

I have seen a very small alu boat where the keel was just welded without ANY structure! it never lost its keel, but he always pulled to one side, like said in post #27.

 

preacher's comments sound reasonable. I believe the highest levels of stress occur in the keel just below the framing, rather that in stringers above. Very few non-engineers seem to have any comprehension of how heavily stressed that area is, taking the full force and moment acting on the keel with an exceedingly small lever arm (keel thickness) to resist a very long arm (keel depth). I would either thicken the area somewhat and/or make the thing out of solid stainless, bronze or whatever is strong enough. In the hull, it's the framing itself that needs to be strengthened laterally, not longitudinally. One option might be to make the framing somewhat flat on the bottom, to make room for a very solid plate to hold the keel, which itself has a widened, strengthened base. The whole assembly kind of flares smoothly from keel to hull, the materials lighter above and stronger below, so it's just about the last thing to break on the boat, not the first.

 

Bavaria Web Site

bandk,

Check out the Bavaria web site...

They have details concerning the BV42 accident.

http://www.bavariayachtbau.de/typo3/index.php?id=34

 

Hei Erik!

Det er nok ikke riktig at ingen tør kritisere Bavaria åpenlyst.
Jeg har korespondert med alle de store magasinene i Europa,
men det er bare Baadmagasinet i Danmark som har turt i publisere
historien min til nå.
Jeg er helt ny på denne forumsiden så jeg vet ikke hvordan jeg
skal få sent deg de mailene jeg har. Hvis du sender meg din mailadd.
skal jeg videre sende dem til deg!
Min mail er: ludvig@ingierkollen.no
Med vennlig hilsen Ludvig Daae (eier av en 42 Match)

 

New disturbing evidence in the Bavaria mess...

I have "ille Moro" aka Ludvig Daae's permission to post the letter that he has sent to the commision investigating the Croatian accident regarding the issues onboard his Match 42 and also the other Match 42 delivered in Norway last year (2004).

The text in full below:

I find the above extremely disturbing and I hope that when publically posting this letter it might help to cause the big giant to turn around.


It also makes me wonder about who actually was responsible for the design of that keel structure. J&J or Bavaria by themselves?


Any comments on the above?

 

ErilG,

What do you make of the modification Bavaria has posted on their website?

http://www.bavariayachtbau.de/typo3/index.php?id=66

 

Dunno...
It's very hard to read. Anyone who has access to the actual drawing could post it here pls.

It looks like just beefing up the lam. But that wouldn't do it IMHO. But since i dont know i cant really say yet

 

Looks like a "tray laminate". It is designed to attach the keel to the longitudinal and transverse hull stiffeners. Without this laminate the keel loads are transfered into the hull bottom and the only connection between the hull bottom and the stiffeners is a glue joint.

 

This could be an interesting one. Bavaria states somewhere that the keel structure has been designed to the CE regulations. That might actually be sort of true. Usually the regulations just specify loads. The keel bolts might actually be strong enough to hold the keel. The hull is strong enough not to let in water and the floor grid might be strong enough to support the keel loads. The only problem is that there was no proper connection between the hull (keel bolts) and the floor grid. The regulations usually don't go into such detail and it's pretty much up to the experience of the designer to ensure that there is structural integrity between the parts.
Now we could discuss how many structural qualifications Naval Architects actually have. In the construction industry you have an Architect that ensures everything looks nice and a Civil Engineer who ensures that buildings don't collapse.

 

Karsten I think you have made some sensible comments about the lost keel issue but I own a Match 35 and can confirm the internal floor frames are bonded with GRP laminate strips to the internal hull surface. I have detailed photos of my Match that prove this and the Adriatic fleet photos show the same.

Some might argue that this laminate bonding is not strong enough and photos from the Adriatic fleet show the laminate bonding is breaking at the 90 degree turn from hull to frame.

I think it is unfair to describe the keel support frames as “stiffeners”. A stiffener in a GRP yacht implies to me a small rounded structure no more than 5cm high, by contrast the frames that should take the keel load in a Bavaria Match 35 are very substantial in size at about 10cm x 16cm (box shaped).

 

We talk about the "bottom" sides of the Bavaria boats, but the upper sides of allmost all mass produced boats surely don't look better. Have you ever checked if the bulkheads are laminated to the hull and deck? If no, be ready for another surprise; they are just sika fastened.
Is that the reason why you hear those grinding noises and cannot close some doors when heeling, even loose some of those fancy shaped plexi portholes while sailing??
They twist and bend like a snake..

 

Could someone point me in the direction of the appropriate CE regulations regards keel attachments. This is a retorical question because ISO 12215-6 Part 6 Structural arrangements and details has not been harmonized. I guess the next best is ABS but some might take a view on that. I would be interested to see a copy of the Builder's Declaration of Conformity, to see what standard was used to demonstrate complience to the structural requirements of the Directive...

Ref. Preacherman's comments, is he refering to primary structure? If a tray moulding or ring frames of adequate strength and modulus are satisfactorily bonded into the hull bulkheads may not need to be structural. I would agree that I would prefer to sail a boat with traditional bonded in bulkheads, and if you are looking for a bluewater yacht that would stand the test of time this would be best.

As with all things in life, you get what you pay for...