My Prestige 560 is sinking (well not quite yet)

[MapisM]

Dont let fact get in the way of a good story

Well, I don't know if that's just a story or not, in this particular case.
But If there's one thing I'm sure of, is that my view on fiberglass cored bottoms is very simple, i.e. over my dead body.

Back to the point, basic math tells us that it takes somewhere between 600 and 700 kg to make a boat like that sit one cm lower in the water.
Now, according to the OP, last year "the exhaust was always way above the water".
So, based on the pics, I would guesstimate that the difference is at least 6 to 8cm, if not 10.
The resulting weight difference spans from a very best case of 3.6T to a whopping worst case of 7T (!).
Now, on a boat like that, even the best case is a very substantial difference, enough to be seriously worried - not to mention if we were talking of 7T! :ambivalence:

Far from wishing the OP that Portofino's guess is correct of course, but if AOTBE the w/line really went down as much as he's saying, pretty sure it ain't just a matter of putting the crew on a diet, I reckon!

 

[MapisM]

With respect to all the fanciful notions on this thread, you seem to be comparing the starboard side to the port side and without seeing a photo of the starboard side this year it is difficult to make comparisons because many boats exhibit a slight list to one side or another because of equipment location

M, of course I agree that it would be interesting to see pics of the same side last year and this year, but the OP said that the above stbd side pic is from another "normal" sistership.

 

[BruceK]

Im struggling to believe that a cored fiber glass hull full saturated is going to add 3 to 7 ton to weight.

 

[MapisM]

Me 2, and I agree with Deleted User calculations, in this respect.
In fact, his assumptions (850kg for 50% water saturation in a 25mm thickness) equals to 680kg for each cm of waterline, which fits nicely with my guess of 600 to 700kg.
We can't get round physics, though: IF (and it's a big if!) the boat is sitting 10cm lower in the water, there must be an additional 7T or so somewhere onboard.

 

[JumbleDuck]

That was exactly my very first thought and I’d say that’s exactly what’s going off with it .boats don’t get lower in the water without added displacement it’s simple maths.

Or reduced salinity - sea going boats sit lower in canals and rivers. Any chance the water could have been fresher when the second picture was taken - full river discharging into the area, for example?

 

[julians]

the two pictures are of different boats (but the same model) and different sides of each boat . Therefore cannot be compared (in my opinion) without knowing exactly how the higher in the water boat is configured.

My money is still on fouling .

 

[Portofino]

If not the actual "core " ( what ever or where ever the material) its water between the liner layers in voids .
Any vac bagging delaminatings also gives rise to potential voids to fill up .
Anyways it's a manifestation of the construction technique used .
The down side of said method chosen.
There's water hiding somewhere.
No point dismissing that .
Assuming clean bottom and the OP s knows his boat WL ?

 

[alandalus11]

The exhaust outlet on the other 560 (although from Stb side) appears to be higher up on the hull and the anti foul and copper stripe also seems to be higher up against the swim platform/aluminium strip... also, your overhang (where hull/swim platform splits) appear longer than the other boat ... Could just be picture angle though ....

+1 on this. The other boats exhaust does seem to be higher up when comparing against the SS rub rail and the curve of the hull structure.

 

[Portofino]

+1 on this. The other boats exhaust does seem to be higher up when comparing against the SS rub rail and the curve of the hull structure.

Nope !
See post #1 the OP
Says
"even when the water tanks were full last year the exhaust was always way above the water.
"
Don't get hung up on the pics they are typical examples not his last year - obviously.

 

[Bouba]

Ok, I thought this might be of interest but I’m having trouble posting it, but the link does work

 

[MapisM]

Blimey, it's remarkable that the video was posted by Beneteau America.
How can they think that a technical choice clearly driven by production efficiency and cost reduction when building in high numbers can be "sold" as a plus to boaters, that's well above my pay grade.
I guess they might think that most boaters don't have a clue...

 

[Bouba]

I just wanted to show how the little squares of balsa are infused to separate them from each other
The argument between volume and bespoke production is eternal

 

[Mr Googler]

Is the bathing platform full of water not an obvious potential cause?

#10 supports it or am I missing something?

 

[CLB]

I am wondering of the OP is putting too much credence on the picture of a different boat. I would like to see the same pic of the OPs boat last summer. Is it really lower than it was, or has the OP convinced himself it is lower? My money is still on fouling. Just look at that waterline!

 

[burgundyben]

I just wanted to show how the little squares of balsa are infused to separate them from each other
The argument between volume and bespoke production is eternal

The squares also assist in vacuuming out the air and passages for the resin to run in during the infusion process and allow the sheets of core to conform to the shape of the mould.

Foam cores have grooves milled in them for that reason.

 

[EME]

I always find it difficult to agree with with 'real' Mechanical Engineers cos they always spoil a good story but , for once, I agree with Deleted User. Pictures in Post 1 are comparing Apples and Pears although the OP believes his boat is settling lower in water.

Loads of reasons to check other things first :-
1) Salinity does increase with heat -- and its been kin cold in Antibes recently.
2) Snow melt does reduce salinity at this time of year in that area.
3) My wife can load more stuff on a boat than former Mech Engineers bits & pieces ( and that's a lot).
4) Im not sure that id spend too much money without thoroughly investigating the obvious' potential solutions to the real problem.

- Props - Antonio (the diver) will do a you a dive for you and clean them / tell you how bad they are. Others will tell you his current rate.
- Growth is a matter of fact and only you know its current state -- I remember one boat there that wouldn't plane without a clean almost every time it went out.
- How much fuel / water / Black Tank are you carrying .
- Different fuel / the bug
- Extraneous water that's built up in scuppers etc over winter

Just saying --- but I know nothing. Hope it isn't anything more than the normal joys of boating.

 

[A_8]

I don't think the pics are at all relevant, plenty of indications they are not comparable. Might not even be the same model or one with or without the platform.
That said I think (only know the ones up to the 500S) the hulls are cored also underwater however the thru hull stuff, if factory mounted are properly installed with the core material well isolated from the hull openings.
Unless the boat has hit something opening the outer grp or some idiot drilling a hole and not isolating the balsa stuff properly it is more likely imho that water has accumulated between the inner lining and the hull if this is a actual case of unintentional added weight.
It's also an IPS boat with the tanks sort of aftish so maybe it will settle more downward aft if tanks are full.

 

[DavidJ]

Assuming that this size of boat can be lifted by crane, I’m sure that cranes register a load reading (for safety)
If it is 7T over this will certainly show.

 

[rubberduck]

My thoughts.
Boat has changed behaviour, so what has changed, drive, so which side is it, is it fitted properly ? Do new drives weigh more (yes I know rather unlikely) Every action has a ..................

 

[Deleted User YDKXO]

I always find it difficult to agree with with 'real' Mechanical Engineers cos they always spoil a good story but , for once, I agree with Deleted User. .

I hope youre not accusing me of being a 'real' mechanical engineer, EME, because I'm not. I trained as a Civil Engineer and that was an awful long long time ago