Oyster Problems?

[jmaja]

Originally Posted by boatpoker

If I spent the time to go through my files I could show you hundreds of photos that would make any reasonable person wary about buying a boat. How about the new 45 catamaran found to be only 3mm (not a mis-print) thick around the saildrive.

Some of you wonder about the cynicism of those of us in the business. I can assure you it is well earned.

So that 3 mm is measured from the recessed area for the sail drive "seal" rubber. Does that area have any structural or water tightness function? Doesn't it all fit inside the engine bed laminated to the hull? Thus it would have water on boat sides and the engine bed as a ring frame around it. Since it is recessed, the laminate is considerably thicker outside it. Is the recession ground into the original hull laminate or has there been a bigger hole which is then laminated just for fitting the sail drive "seal"?

You can find very thin laminates on many boats close to the sail drive. E.g. X-Yachts do not use the rubber seal. They use very thin laminate to guide water and reduce drag. That has nothing to do with the saildrive being prone to be damaged when hitting something. That would depend on how well the engine bed is supported.

[gjorgensen]

Originally Posted by minaret

Pocket tape:

Wow, that is completely ridiculous on Beneteau's part. It's hard to imagine the bow surviving a head on collision with anything solid at more than a couple knots.

Having had to have some bow work done on my 40.7 (long story, but rest assured not a low speed docking accident) I can at least say that the 40.7 is significantly thicker. I never measured it, but I'd guess twice as thick along the hull up front. What the strength of that actually is I don't know. I do know that the glass along the nose of the boat and all the way down into the bottom of the hull (through which the chain plate is fastened) has to be close to 3 inches thick.

So I'd be curious if this sort of thinness is now universal for them in this size range (e.g. on the Oceanis 38)?

[neilpride]

Originally Posted by gjorgensen

Wow, that is completely ridiculous on Beneteau's part. It's hard to imagine the bow surviving a head on collision with anything solid at more than a couple knots.

Having had to have some bow work done on my 40.7 (long story, but rest assured not a low speed docking accident) I can at least say that the 40.7 is significantly thicker. I never measured it, but I'd guess twice as thick along the hull up front. What the strength of that actually is I don't know. I do know that the glass along the nose of the boat and all the way down into the bottom of the hull (through which the chain plate is fastened) has to be close to 3 inches thick.

So I'd be curious if this sort of thinness is now universal for them in this size range (e.g. on the Oceanis 38)?

Yours is thicker compared to the oceanis , but hell not, not even close to 3 inches, and I replace a couple of those furler tangs in both 40,7..

[Muckle Flugga]

Originally Posted by Just Another Sa

They should not be allowed to hit the drive leg by design.
Put that extra weight into the keel structure which is going to hit those solid things, and not to somewhere else that is (or at least should be) protected by the keel. Pretty easy to add a horizontal string from the bottom of the leg to the back edge of the keel preventing any hits to the leg, while being much lighter than all the laminate needed to make the leg and the structure around it capable of withstanding the hits.

Ok, are you trolling? They shouldn't be ALLOWED to hit the drive by design? What??? You are aware that keels don't surround the drive like a fortress, right? And that objects in the water may spin round as they are hit by the keel, subsequently hitting the drive… or may be moving (whale, or in a current etc), or else be pulled towards the drive by the fact that the drive accellerates water towards itself by its very function??? Or the drive may take a hit from the bottom, by either an object or, well, the bottom?

You appear to be living in some kind of magical fantasyland where everything is simple, clean and easy to fix. Frankly 3mm structural skin on ANYTHING below the waterline is a freaking toy.

[neilpride]

A PVC Kayak skin is around 5 mm...

[jmaja]

Originally Posted by Muckle Flugga

Frankly 3mm structural skin on ANYTHING below the waterline is a freaking toy.

Yes, but is that structural or just a fairing?

[transmitterdan]

Originally Posted by jmaja

Yes, but is that structural or just a fairing?

Who cares whether it's structural, it's keeping the ocean on the outside. Isn't that the number 1 job of the hull?

[jmaja]

Originally Posted by transmitterdan

Who cares whether it's structural, it's keeping the ocean on the outside. Isn't that the number 1 job of the hull?

Is it? There is "ocean" on both sides of the sail drive fairing. The actual seal keeping the ocean out is between the engine bed and the sail drive (the top of the ring with many bolt holes). The engine bed is laminated to the hull. My question earlier was whether that 3 mm laminate was actually just part of that fairing.

[minaret]

Originally Posted by jmaja

Is it? There is "ocean" on both sides of the sail drive fairing. The actual seal keeping the ocean out is between the engine bed and the sail drive (the top of the ring with many bolt holes). The engine bed is laminated to the hull. My question earlier was whether that 3 mm laminate was actually just part of that fairing.

Having installed a fair number of sail drive engine beds, I think it's safe to say the builder didn't make a perfect disc of super thin laminate in the hull to land the bed on, with perfect alignment, all just to save a pound or two of glass and resin. Almost certainly the entire area was that thin, and they counted on the bed tabbing to build up enough strength in that area. I think this is nuts, as sail drives are obviously going to be a high load area even without an incident. This part of the hull should be full thickness, with the bed heavily tabbed onto that. Anything else is ridiculous. The pic you posted is a great example-does that look like 3mm laminate to you?

[jmaja]

Originally Posted by minaret

Having installed a fair number of sail drive engine beds, I think it's safe to say the builder didn't make a perfect disc of super thin laminate in the hull to land the bed on, with perfect alignment, all just to save a pound or two of glass and resin. Almost certainly the entire area was that thin, and they counted on the bed tabbing to build up enough strength in that area.

But that area of 3 mm laminate was in the recessed area for the sail drive rubber fairing. Hard to say from the picture, but it may well be more than 5 mm below the hull surface. Thus the laminate is maybe 8-10 mm outside that rectangular recession?

[transmitterdan]

If it doesn't do anything (not structural, not water tight) why have it there at all?

[minaret]

Originally Posted by jmaja

But that area of 3 mm laminate was in the recessed area for the sail drive rubber fairing. Hard to say from the picture, but it may well be more than 5 mm below the hull surface. Thus the laminate is maybe 8-10 mm outside that rectangular recession?

Do you think maybe the recession is molded in? Why would they cut out all the glass in that area instead of just glassing over it? It'd be a substantial extra step for a negative result. Certainly they didn't machine that recession in place, which would have to be the case for what you are saying to be true.

[neilpride]

This whole 3mm drive leg hull issue It has been discussed here...
http://www.cruisersforum.com/forums/...e-87514-4.html

[jmaja]

Originally Posted by minaret

Do you think maybe the recession is molded in? Why would they cut out all the glass in that area instead of just glassing over it? It'd be a substantial extra step for a negative result. Certainly they didn't machine that recession in place, which would have to be the case for what you are saying to be true.

It doesn't look like it is molded in. Hard to say from the pictures, but maybe a bigger hole is cut and then the engine bed is installed. So maybe the 3 mm is actually part of the engine bed and not the hull laminate. No idea why they would do it like that instead of cutting just the minimum hole for the leg.

The other thread shows that this area is covered by a thick grp plate, thus the 3 mm is protected by that plate. If there would be a leak through that 3 mm, where does it leak to? Into the engine bed probably, but that is laminated to the hull.

[jmaja]

Originally Posted by transmitterdan

If it doesn't do anything (not structural, not water tight) why have it there at all?

It could be just a fairing used for reducing drag due to the opening around the drive leg. Like this one. Note it is quite thin and has no structural nor water tighness function. It is there to guide the flow past the opening around the leg. I don't know about this one, but my boat has just 5 mm gap between the leg and the fairing.