Swim platform issues

[Nick_H]

Since the full to empty difference is about 3T

Fuel difference < 2 tonnes I'd have thought, allowing for 2650 litre tankage, reserve, and specific gravity of diesel.

 

[Nick_H]

If I read the Princess reply correctly, they are saying that the OP's boat has a minimum depth over the fully lowered platform of 362mm (ie. at low fuel levels). Jimmy informs us that the Williams has a draft of 300mm max. If both those are correct, then is it just the chocks that get in the way? If so, the easiest solution must be to design some very thin chocks?....QUOTE]

in order to follow the profile of the Williams I doubt the chocks could be much lower than 40mm, this would only allow 22mm of clearance, fine in dead calm conditions but with any kind of chop the same problem arises.

I've not had a hi-lo platform, but I guess you pull the tender on from the side, bow first, so you don't need to clear the full height of the chocks, only the lowest point. Even if this isn't normally required, it may be a solution for the OP. I suspect the issue is deeper than this though, or should I say shallower.

 

[Deleted User YDKXO]

Great thinking Mike. You can see that this owner has a similar prob trying to get his bathing platform to stay underwater, and in line with your suggestion has rejected ballast in favour of 'something useful'...

Wey hey Jimmy, even though I am 'old' thats my kind of ballast

 

[FloydLyons]

I am having the same doubt i guess. Can't overlook that fact.

 

[MapisM]

Fuel difference < 2 tonnes I'd have thought, allowing for 2650 litre tankage, reserve, and specific gravity of diesel.

Well, I didn't consider any reserve, since I guessed the 83mm they quoted was a theorical number based on the dry vs. full load difference. Besides, I included the fresh water tank.
Anyhow, the 83mm would be even more ridiculous, if you consider 2T.
The hull should have a footprint of only 24 sqm to go up and down that much with such little difference, go figure....

 

[Deleted User YDKXO]

To start with, a boat weighing less than 25T dry, according to the builder specs.
And they are suggesting that a 750kg ballast astern would bring the stern draft of your specific boat "back to normal", so to speak.

Now, forget the effect on performance. The first thought is that there isn't much else other than the main GRP shells, where that weight might have been lost.
But it is difficult to know (I mean, without some inside knowledge - the builder must know exactly, of course), the weight of the bare hull and superstructure.

I suspect what we're talking about here is a bit of a cock up in the design dept, rather than an inherent hull issue, in that the designers have calculated the position of the platform based on a certain spec of boat. Put this together with a platform that has quite a limited range of movement and then you may have a problem with fully submerging the platform on a lightly specced boat. It would be interesting to know what the spec of the OP's boat is and where it is based (UK or Med). Does he have aircon, pasarelle, crew cabin and other weighty equipment or not? Does he have the standard gennie or upgraded one?

 

[Lozzer]

On the Princess 85 the range of the platform is also not great. We have to float our Jetski off backwards to clear the chocks because of the profile.

Launching and recovering is a two man job in any sort of seaway. Flat calm easy for one person.

The remedy of adding weight to lower stern is laughable when they invest millions to lose it. Makes a mockery of the design really.

Can Princess provide you with accurate data compared to other 56's with hydraulic platform? Out of the 36 they compare you to how many have platform? Surely this has already added a fair amount of weight so why you are lighter than most is even more bizarre!!

I hope you manage to resolve the issue amicably. Going legal will mean only one happy group, the lawyers!

 

[MapisM]

I suspect what we're talking about here is a bit of a cock up in the design dept, rather than an inherent hull issue

+1.
Re. options, of course the cock up would be even worse if the OP has a loaded boat, but let's assume the boat is NOT a loaded one.
The 25T displacement I previously mentioned is for a base boat anyway.
In fact, in their website they say 26.2T, specifying that it's calculated "with 50% fuel and water but with no optional equipment fitted or other gear or crew aboard". That's why I said 25T dry, give or take.
They just don't say if the number is related to Cat or VP engines, but the difference is neither here nor there, in this contest.

 

[pan]

We don't know what other correspondence OP has had from Princess, so it may be unfair to suppose that the posted response indicates they are in defence mode, without any other suggested remedies, but as others have posted here (mapis, etc) their defence defies logic, let alone the preposterous suggestion of 'lobbing several kilos of extra weight into the stern' makes me wonder what happens to the waterline when the williams is lifted on to the bathing platform in addition to this extra weight, unless the platform sits very high out of the water, there is the possibility of it acting as a massive sea anchor, particularly in a strong swell..

Princess appear to be very 'economical' with the build data so far, as well seemingly unable to do the maths correctly.

 

[jimmy_the_builder]

Wey hey Jimmy, even though I am 'old' thats my kind of ballast

 

[jfm]

So what would a typical bathing platform drop be? Actual measurements rather than guesses please.

I have the .dwg files here for the HB Technics lift system but can't open them on this office computer. Can do tonight at home. But flick to 5:08 in the vid below of my previous boat. Actually that is the still already showing in the freeze frame below - you do not need to play the vid. That is platform down. The vertical stroke of the platform is about a metre and the level of the teak below waterline when platform is down is 800mm or so

To help interpret the picture at 5:08: the Yamaha on the tender is longshaft, so transom height is 20inches = 500mm and as you can see the depth of the platform's teak below the waterline is approaching double the tender's transom height. Also, the black antifoul paint is close to the boat's waterline - it doesn't come up much above the actual waterline

Designing a platform that sinks to only 362 or 400mm or whatever below the w/line is just stupid. You can't do these things to the nearest few mm because the boat and tender bob about in waves and you need plenty of clearance to stop things bashing. Platform surface needs to be about 550 or 600mm below nominal waterline

750kg of ballast - sheesh. That's like carrying 10 extra passengers!

This is a Princess mistake alas. They have saved cost by buying an inferior lift system that has too little vertical stroke

 

[jfm]

ROTFL, I suppose that "whatever" includes a notorious curved equipment.
So, eventually we are understanding why it was chosen for the P56.
Nothing to see with vectorial analysis, 'twas all down to someone in Plymouth saving a few quids...!

Sorry jfm, but I REALLY couldn't resist this one.....

Haha, get you MapisM! You ran away crying from the other thread about curved fins when the kitchen got a bit hot (even though you turned the heaters on) but hey when a fresh opportunity comes along to lob in an unfounded criticism of someone's innovation you cannot resist!

Sleipner's vector fins won the overall DAME award this year, by the way. And they are not fitted by Princess to the 56 afaik - that was a custom install done on the 56 built for the family that owns Sleipner

Anyway, let's not drift this thread too much. I have a plan to collect proper data to demonstrate the performance of the curved fins, but need a bit longer of course

 

[BartW]

So what is a normal or recommended drop ?

More and more boats seem to be fitted with moving platforms or variations so I think it would be a useful thing to know.

I presume there is an added complication with movable platforms in that you don't want them too close to the water when up and closed otherwise the platform acts as part of the hull or a giant trim tab when underway, particularly when it is a nice deep platform. If in contact with the water a lot of stress will be placed on it as it supports the vessel.

Henry

here is a drawing of my H+B setup,
full stroke is 1060mm
on the drawing mine is 450mm below waterline when fully submerged
in reality up to 600mm when more weight in the stern, scuba tanks, dive gear, full on fuel, ....
and I guess that our fixed platform is higher then on many newer installs,

most people ask about what happens during navigation,
but this is actually a non issue,
the platform is sometimes getting wet from spray along the sides, ...
I have two ladders permanently fixed under the fixed platform, until just above the water surface, and they are fine, without any special reinforcement.

 

[Deleted User YDKXO]

This is a Princess mistake alas. They have saved cost by buying an inferior lift system that has too little vertical stroke

Never having been in the fortunate position of specifying a new boat with a hi/lo platform, what do boatbuilders sell these things as? Do they sell them specifically as tender launching systems or as get yer feet wet paddling pool extensions? I'm just wondering if Princess might turn around and claim to the OP that they never sold it as a tender launch system. Also is there not the option to lift the tender in with the pasarelle on some boats as well as the hi/lo system?

 

[jimmy_the_builder]

Never having been in the fortunate position of specifying a new boat with a hi/lo platform, what do boatbuilders sell these things as? Do they sell them specifically as tender launching systems or as get yer feet wet paddling pool extensions? I'm just wondering if Princess might turn around and claim to the OP that they never sold it as a tender launch system. Also is there not the option to lift the tender in with the pasarelle on some boats as well as the hi/lo system?

See post #40.

At the MBY 40-foot sea trial day last year I was on the Princess V42, which also had a hi-lo platform. The salesman from PMYS did say that in that case the platform had a lifting capacity of just 100kg and was not intended as a tender lift (the V42 does have a tender garage, so this does make sense).

 

[Deleted User YDKXO]

See post #40.

At the MBY 40-foot sea trial day last year I was on the Princess V42, which also had a hi-lo platform. The salesman from PMYS did say that in that case the platform had a lifting capacity of just 100kg and was not intended as a tender lift (the V42 does have a tender garage, so this does make sense).

Yup I remember that post but the description doesn't actually state that the hi/lo platform is designed to be used for drive on/off launching of the tender. It could equally be read as the platform being suitable for just storing the tender. I'm just wondering whether Princess have any wriggle room here or whether they're banged to rights

 

[david_bagshaw]

Been following this thread with interest.

I am from a displacement only background, I thought of barges and propellor immersion when empty.

Although the correct answer is a longer drop of the deck, would fast filling, and emptying ballast tank in lazarette be a sensible answer.

Would get the depth for rib launch without the weight penalty underway

 

[Asm]

I asked if were possible to specify a passerell that could lift a rib onto a fixed platform. No! was the answer ( a transom glass panel fitted to a lot of current models prevents it ) unless you wished to push your rib over the platform to launch it, you had to order the lifting platform. For the Med you still have to spec a passerell, but it's off to one side and cannot lift. Apparently it's what boat owners want!

 

[jimmy_the_builder]

I asked if were possible to specify a passerell that could lift a rib onto a fixed platform. No! was the answer ( a transom glass panel fitted to a lot of current models prevents it ) unless you wished to push your rib over the platform to launch it, you had to order the lifting platform. For the Med you still have to spec a passerell, but it's off to one side and cannot lift. Apparently it's what boat owners want!

Doesn't this completely depend on which specific boat manufacturer and model you're referring to?

 

[henryf]

Been following this thread with interest.

I am from a displacement only background, I thought of barges and propellor immersion when empty.

Although the correct answer is a longer drop of the deck, would fast filling, and emptying ballast tank in lazarette be a sensible answer.

Would get the depth for rib launch without the weight penalty underway

Not ideal and it adds a load of effort as well as taking up space but an interesting solution. Self venting over the side when full so no need to monitor particularly when filling, the issue would be how quickly they can fill and empty.

Ultimately though you are only talking a couple of inches.

I've always assumed the benefit of a lowering bathing platform is the ability to have a decent size platform. With a passerelle / crane you don't want to go too large otherwise the leverage reduces your lifting capacity. Heaven forbid the passerelle can't keep up with the beer goggles when moored stern to in the SOF. With my more modest bathing platform I can bring a good heavy load on board. Gosport spec

JFM came up with an interesting solution at the Magnificent British boat Builders show. He simply carried a couple of cases of beer on board and sent someone down to Iceland for finger food. 30 plus people later the back end was suitably low down.

I remember thinking the boat looked a bit too low in the water, then I did a quick head count in the cockpit and realised why. You don't get many Great British boat owners to the tonne, not like these bikini clad beach babes

Henry