platey sunk NE of hutchies?

[Shark Poker]

Not really getting what you mean muddy toes.
Over a long, long 3hr period.... putting a rope and float on the vessel would seem to help monitor its movement and location.
"85m NE off Hutchies" is subject to massive changes in depth and the current can really rip thru there in differing directions.

It would require a vessel to land in very shallow water without any current for a rope to be a hazard.
Hopefully the vessel was insured and wished to be written off, but it might have been on everyone's' mind, over such a long period, to mark it with a buoy.

[fly_1]

The decision to Not mark it with a buoy was made by the water police after they spoke to the vessels insurance company. After it was certain it was going to sink, and not just sit under the surface they water police told us to make a note of the position and let it sink.
Of course we would have put a buoy on it, but after being instructed not to we didn't.
Trent

[Muddy Toes]

Not really getting what you mean muddy toes.
Over a long, long 3hr period.... putting a rope and float on the vessel would seem to help monitor its movement and location.
"85m NE off Hutchies" is subject to massive changes in depth and the current can really rip thru there in differing directions.

It would require a vessel to land in very shallow water without any current for a rope to be a hazard.
Hopefully the vessel was insured and wished to be written off, but it might have been on everyone's' mind, over such a long period, to mark it with a buoy.

I think you're clutching at straws here............

So you attach a rope and float to it.....It gets washed along the sea floor in to deeper water......float and rope=useless.
So you get smart and tie a very long rope and a float to it to counter this possible scenario........just created a navigational hazard if it goes shallower.
Not really hard to pick the direction and speed it would move if it does move.
Not really hard to find it on the sounder.
Who is going to want to recover a trailer boat in that depth?

[ric]

With the laws of basic flotation, how can the boat sink? I thought basic was meant to keep the boat afloat, but not necessarily the right side up? Aren't all boats required to be basic flotation to be registered?

[Grim Reefer 750]

So pump action was air chambers or foam filled ??

I'm guessing it would not of sunk if it was foam filled, anymore info on this incident???

Cheers

[gofishin]

...Aren't all boats required to be basic flotation to be registered?

Yes, those under 6m and constructed or imported after 2005, maybe 2006 from memory - can't remember exactly.

The choices are 'Basic' or 'Level' flotation, but the important part..."how is this flotation achieved"...is/was not required to be included on the ABP.

It has been a long while (9+ yrs) since I have read any of the applicable standards, or designed/specified flotation requirements for recreational vessels <6m, so things could have changed a lot, but builders used to have a choice as to what standard/how they determine the flotation required for their boat under the ABP.

ISO and US standards (not to mention other countries that also adopted these regulations) have/had for many decades imposed restrictions on the use of air chambers for 'flotation requirements'. If air chambers were used as flotation devices with vessels <6m, then the largest two air chambers were not allowed to be used when determining 'conformity' with the standard.

This constraint was in place for safety reasons, to account for the possibility that air chambers can 'for many reasons' not hold air as they are supposed to. This requirement meant that for the majority or rec vessels <6m, it was pointless using air chambers as part of the 'flotation design'.

Here we get in to the definitions of 'flotation' and 'positive flotation' - the latter being where a material or device is used to positively displace the water, i.e. foam flotation material.

I'm not implying that this boat had air chambers, it may have had any type of flotation. At the time of the incident it just did not have 'sufficient' flotation to remain afloat.
Cheers
Brendon

[tunaticer]

I know of two boats that had thwart seats and foatation removed and fully floored.
Under the flooring they stuffed sealed plastic milk bottles for floatation tanks.
Probably not a bad idea to cram every small area with a sealed milk bottle I guess.

[Noelm]

Yeah, that's a great idea,except for the fact that plastic milk bottles degrade to almost nothing after a while.

[WalrusLike]

Yeah, that's a great idea,except for the fact that plastic milk bottles degrade to almost nothing after a while.

As usual, I could be wrong, and often am, but I think degradeable plastics are degraded by UV light.... so if the milk bottles are underfloor they _might_ be right for 200 years.

I think that physical abrasion from boat vibration and movement would be a greater risk. Personally I would be very careful with flotation.... I've seen foams that were just sludge after a while.

I wonder what my boat has?

Sent from my iPad using Tapatalk HD

[Shark Poker]

On the subject of flotation, most big plateys in the past have been built with air chambers rather than foam.
(As a window/hatch fabricator - trying to sort out cabin/top deck/roof arrangements - I climbed into more half built different plate boats than probably anybody)

I guess the logic is that people like the strength and rugged durability of plate boats. How are you going to break open stiffened plate to release the air? And even if you did, it is underfloor beneath a sealed deck.

However, these sealed compartments are welded shut, but not properly sealed or pressure tested (as we would do when building a fuel tank) so in a capsize or similar drama it would be possible for the air to slowly disappear and be replaced by water.
When this happens, it is hard to explain how quickly something buoyant turns into a weight bound for the sea floor so quickly.

That is why foam is seen to be the solution.

Some concerns that some ally builders had ( have) is that some foam products absorb moisture, and others hold build-up of salt against the alum surfaces leading to potentially major corrosion issues.

For many builder the 'jury is still out' on the subject of flotation, especially on hulls that have compartments welded shut, and therefore you can NOT inspect the interior, EVER.

I will check with the builder later today or tomorrow and if I learn anything suitable to post, will do so.

[gofishin]

...Under the flooring they stuffed sealed plastic milk bottles for floatation tanks.
Probably not a bad idea to cram every small area with a sealed milk bottle I guess.

A few problems with this theory, and with this type & shape of plastic bottle.
1. Milk bottles are designed to hold a liquid which is under no pressure, and are square in section as a result. (the benefit for the milkman is that they package better in crates!) The lid is not a good seal under pressure either. Plastic soft drink bottles on the other hand are round (because they are designed to withstand pressure from within), and hence have a much better sealing lid.

2. With basic flotation, the boat will turn turtle and most likely float in a stern down or even vertical position. If you have a 6m boat with 'bottles' for flotation, with some at the stern, and it becomes submerged just like the one in the photo - i.e. vertical & 1m of bow above the water, then the bottles at the stern will be 5m under water and subject to ~50kPa (1/2 an atm) of pressure from outside. What do you think will happen to a milk bottle at 1m deep let alone 5m? It will crush, thus it displaces less water and hence it offers less buoyancy, so the boat sinks a little deeper, the pressure gets greater, the bottle crushes more....the cycle repeats itself until the boat hits the seabed....

3. The volumetric efficiency of bottle bundles are not that good. By this I mean the amount of water displaced by a number of bottles vs the physical space these bottles take up together. There are lots of gaps between the bottles, no matter how you arrange them. Therefore, you will need more spaces to fill with bottles than say if you were just using foam in those spaces.

4. Voids in boats available for flotation are normally odd shapes, hence when filling this space with bottles it becomes even harder to maximise the 'displaced water'.

cheers

[stevej]

As usual, I could be wrong, and often am, but I think degradeable plastics are degraded by UV light.... so if the milk bottles are underfloor they _might_ be right for 200 years.

Sent from my iPad using Tapatalk HD

Uv Rays can penetrate many surfaces, heat can be transferred from the floor surface to the bottles causeing them to be come brittle

[WalrusLike]

Yeah.... 'Tell him he's dreamin'.

Thanks for the physics reality check. Milk bottles would be near useless if any deeper than a few inches.

[Tinspo]

Hi All,

Does anyone have the contact details for the poor bloke who lost his boat? I have done some salvage in the area and would be keen to give it a go.

Best,

Jeremy

[GBC]

AMSA uses ping pong balls to keep holed tankers afloat. Don't know about the long term stability of the plastic, but they are used, I know that for sure.