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Old 04-16-2017, 11:06 AM
Senko Senko is offline
 
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South Africa and SAMSA Buoyancy

Good day good people.

I am new here so please bare with me. I am in the process of designing and building a casting deck onto a small tug 10 vessel. My questions are as follows: #1 What wood can I use for the support structure underneath the deck? (Obviously needs to keep it as light as possible.)
#2 Concerning the SAMSA regulations regarding the buoyancy, how do I calculate the 30% required buoyancy when I will be using the SPX 30 foam from Sondor?
#3 Will I be able to install it myself and gain a Buoyancy Certificate or must a certified installer do it?

Thanks in advance
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  #2  
Old 04-17-2017, 04:26 AM
Wynand N's Avatar
Wynand N Wynand N is offline
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Hi Senco,

Im retired from boating for a few years now due to old age but I have to chime in here.

Buoyancy issues are a farce in SA due to incompetent installers and I would venture to say lawmakers are not beyond question as well.

For starters, 30% buoyancy (for inland use) does not float most of the powerboats out there, period. I made it my business about 7 years ago and informed a senior member of the then BIASA of which I was a member to take it up with SAMSA. Nothing came of it and many, if not all boaters with Category "R" are under the impression that their boats are unsinkable hence the 30% buoyancy installation if it was correctly calculated and installed by installer I must add.

The 30% I believe was obtained by the lawmakers when one takes the submerged weight of laminated fiberglass in water, whereas the density of water comes into play, for example:
Laminated GRP SG = 1500kg/m3 (SG=specific gravity)
Submerged factor multiplier = 0.33
IOW, a cubic meter of laminated GRP submerged weights a third of its dry weight, and suddenly the 30% buoyancy requirement for Cat 'R" make sense as to how they arrived at the number. Here is a short table with conversion factors for different submerged materials - full list can be seen at http://www.uscgboating.org/safety/bo...n/table4-1.htm



However, what they seemed not to have taken into account is all the other stuff that goes onto the boat and the engine jumps at you because it is mostly made from steel and aluminum and looking at the SG's above and submerged converting factors made your hair stand up. Not to mention the battery(s) stainless steel and all other heavier than fibreglass items on a boat.
And it even get worse with boats with two outboard engines and larger the engine the worse it gets...
However, the 60% buoyancy to displacement ratio called for offshore boats makes more sense for most boats if the second engine is factored into the calculations.

But as said in my opening remarks, the problem lies with the buoyancy installer. They should have had some training which a few years ago was in the form of workshops arranged by foam manufacturer and SAMSA which yours truly attended. As a boat designer (Diploma from an accredited institution) I was not very impressed by their MO and calculations and kept mum - you know the saying about arguing with someone ...
Every buoyancy installer in SA will tell you impressive things about how it all work and most, if not all, cannot tell you why a boat floats. I once recalculated the figures on a certificate that was suspect for a client that stated that the buoyancy ratio installed was over 60% whereas it was actually only 27%.
At least in your part of the country you can perhaps find a credible installer, (just be glad you are not in my part of the woods) but again he will only install as required by law (SAMSA) and the 30% only put you in a sense of false security in believing you boat will be OK when holed and taking on water big time.

I do not know the current state of affairs with the buoyancy issues and as I said Im retired from boats et al since 2013 and try to keep it this way, but I heard a rumour that the 30% is now replaced by sufficient and if this is true, it even gets worse. Hopefully it is just a rumour and should be treated as such.

Imagine how an owner whom had built a boat out of marineply wood that have a positive submerged buoyancy ratio of nearly 50% going to convince a buoyancy installer that without an engine his boat exceeds the 30% required by SAMSA by far. Remember, most of these installers are boatshop workers without any "boating design" expertice and in my town the installer's main work is fencing, gates etc...

As a parting note; download the USA Coastguard buoyancy manuals (bulky and complete with sketches and calcs on how to do) etc. if you want a proper take on how it should really be done and calculated, and I would suggest SA maritime lawmakers do the same.
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Old 04-17-2017, 05:20 AM
Senko Senko is offline
 
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Thanks for the reply Wynand N. Yes I did do a lot of searching on the west side of the Atlantic's websites and found a lot of good info. The boat I am in the process of "upgrading", hope it won't downgrade him, is a smal 3m fibre glass " dingy" from Outdoor Marine in PMB with a 4hp Mariner. I fully understand that the 30% seems a bit on the low side but I am intending to mainly use the boat alongside the banks of the local waters here up north. I just want to decent chance to get to land in the event of something going wrong, but mostly I want to keep SAMSA and the Authorities off my boat and my shoulders.
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Old 04-17-2017, 05:30 AM
Wynand N's Avatar
Wynand N Wynand N is offline
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Because of the size of your outboard motor (15hp or less) you do not need a skipper license or COF and I believe the length and engine combo also expels it from a buoyancy certificate requirement if Im not mistaken. However, the skippers and COF Im 100% sure of.
That said, SAMSA requires boats with engines 15hp and under that are exempted from the above certification to have the nessecary safety equipment on-board like life jackets, first aid kit, oars and bailing bucket for example.
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Old 04-17-2017, 08:30 AM
Senko Senko is offline
 
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I found this from an Australian Site: http://www.mast.tas.gov.au/wp-conten...iler-Boats.pdf

Can you please have a look at it and give me your feedback? I would appreciate it a lot.
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Old 04-18-2017, 02:57 AM
Wynand N's Avatar
Wynand N Wynand N is offline
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Hats off to you for finding this excellent but basic article on buoyancy.
It is well presented with simple calculations everyone can understand and execute. You will notice the "K" factors given in my list in a previous post is very similar.
Wish SAMSA can get hold of this and use it as a template for aspirant retro buoyancy installers. Take not that by law all new boat manufactured for at least the last 10 years should comply with SAMSA buoyancy requirements and supply with certificate to the effect.

The problem, even when local installers use the formulas in the link you supplied, is the lack of knowledge for the most of them to determine the amount of volume available under floor due to the different hull shapes boats have, and herein lies the sting with current certification and most will be in error....

As a side note: The SONDOR foam you specified is the best available bar none, but the average retro installer has no clue to what they deal with from past experience of a friend of mine in Pretoria, also in Centurian - they only know close cell expanded two part polyurethane foam, which I despise due to the fact that it absorts water like a sponge, regardless of what the manufacturer or installer will tell you.
During my tenure as boatbuilder (GRP division) I had cut open 3 boats that was so heavy we had to use a crane to get them off trailers and when floors/decks were taken off, the close cell PU foam was one solid piece of trapped water when taken out with spades. I took videos of these events as proof.
Imagine yourself if some water getting into the boat and is trapped between the hull and foam - as the boat runs over waves and the hull flexes and presses on the foam with water in between, where will the water go? Simple, the path of least resistance, IOW into the foam rather than into the rock solid hard fibreglass. When the PU foam is poured into hull space, it is not solid to the floor and will always leave holes, cracks and spaces for water to be trapped if it found a way into the hull by whatever reason.

beste groete
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