Boat/ship mods

My sincere sympathy to those who lost loved ones on the sinking of the prawn trawler out of Carnarvon last year. I am raising this subject with the hope that wee all can benefit from the inquest currently being held into the tragedy.

Has any body else been reading the reporting's of the coronial inquest into the sinking of the prawn trawler out of Carnarvon last year with the subsequent loss of 3 lives, I think the trawler was named "Returner"

From the reports in the "West" it is appearing that the removal of a lot of lead ballast put the ship at risk through loss of stability. This may have played a very significant part in the cause for this vessel to be lost.

The reason I am bringing this up as a form subject is this, how many times do we read on this site about members doing mods to their pride and joy and I wonder just how many of us really know to what extent we are altering the sea worthiness of our boats. I know I have made some mods, fitting fixed trim tabs and putting in another fuel tank without really sitting down and doing a bit of serious thought about the possible effects this may have on stability in heavy weather.

The trim tabs worked great in reasonable seas, however after coming home one time with a quite large following sea and imitating a Collins class sub doing an emergency dive I quickly changed them so that I can raise them to a neutral position when coming home with a following sea.

I think this tragedy should be a bit of a wake up call to all of us who do our own mods to boats to get some advice from the people who build boats for a living and are/should be well qualified to give their advice about our plans to alter our craft.


black gen's picture

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Date Joined: 13/04/11

 That's a fair point you

Sun, 2017-07-30 06:40

 That's a fair point you make 

I don't think many rec boat owners would give it too much serious thought.

 

it wasn't out of carnarvon I believe it was lost off Dampier 

carnarvonite's picture

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Stability

Sun, 2017-07-30 06:50

One only has to look at the rocket launchers with about 10 rods and reels sitting on top of small boats.

Take the weight of the pipework then add what rods and reels weigh times the height and it can be a very bad idea in rough weather.

Shifting or adding an underfloor fuel tank doesn't alter the stability very much as its well down towards the boats centre of gravity, any weight changes can be fixed by trimming the boat.

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Date Joined: 23/04/14

A bit more to it

Sun, 2017-07-30 07:21

For boats you need to consider centre of gravity, centre of buoyancy, moment of inertia, and probably other things.  Shifting a fuel tank will absolutely have an effect.

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sea-kem's picture

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Date Joined: 30/11/09

 That's a good point John, I

Sun, 2017-07-30 09:31

 That's a good point John, I had a woman contact me about a 7m boat she had bought to go fishing with her sons. She said there was cracking around the base of the cabin and could I repair, so I said to bring it in for a look. I could see that this massive tall cabin was an add on afterthought and was way too tall for the boat. I said she should seriously get a marine engineer to have a look for advice, I basically didn't want to touch it as I could then be found liable if anything I did was detrimental to the hull or if it started cracking somewhere else. I could though basically see that this huge cabin was making the bulkhead connectin  'flex' when driven through the sea, she said the whole thing would rock when they would go over a swell. People need to remember ali is a rigig material that doesn't like to flex like fibreglass will and over time ali becomes brittle. 

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Love the West!

z00m's picture

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Launcher

Sun, 2017-07-30 11:36

 According to John though you shouldn't have the rocket launcher filled with rods and reels as seen in your avatar unless it has been surveyed  

I agree that changing the fundamental structure or balance of your vessel is not the best idea unless you seek expert advice but I don't see that adding a bimini, rocket launchers, rods, bait board, beer, ice, fish etc is outside the intended use of a boat.

Centre of balance is what needs to be considered and you need to understand your weight budget for a given hull.

sea-kem's picture

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 Lol my canopy will snap

Sun, 2017-07-30 14:49

 Lol my canopy will snap before the boat does.

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Jackfrost80's picture

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Maybe for those who run with

Sun, 2017-07-30 19:09

Maybe for those who run with skull dragging combos. Most of us have about 6 combos up there weighing in at around 3.5kg in total. A gust of breeze into the bimini would have more chance of tipping the boat...

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 Big fish need big gear 

Sun, 2017-07-30 19:44

 Big fish need big gear 

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Date Joined: 23/04/14

Interesting topic

Sun, 2017-07-30 07:08

The only real way to ascertain the effect of such changes is to have a naval architect do a weights and moments study.  I'm not sure what the requirements are for commercial vessels but I'd say there are very few recreational vessels, of trailer boat size, in Australia that would have been designed in this way.

I did read that the fishing vessel that sank had undergone a survey after the mods. 

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peterm8's picture

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Date Joined: 25/10/13

Mods

Sun, 2017-07-30 15:56

 Good topic and good points raised. If you want to look at a situation where mods really get out of hand, look at a site called "The Captain" on FB. An old, renovated V17 Haines in centre console configuration with 300hp strapped to it! Nice looking job on the reno, no doubt about it, but the owner claims 60kts, which I suspect is a bit quicker than the original designers had in mind in the 80's or 90's. 

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Swompa's picture

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 Please correct me if I am

Sun, 2017-07-30 19:01

 Please correct me if I am wrong, but didn't they take 3t of lead out of the trawler that would have weighed around 30t? Strange for sure.

Stevo81's picture

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2.6T of lead ballast weighing

Sun, 2017-07-30 19:12

Yeah, 2.6T of lead ballast was removed during mods

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Added bimini

Sun, 2017-07-30 20:31

2 years ago I watched a 12' tinnie out on the Mandurah estuary crabbing, in it was Mum Dad 1 small kid, it looked the perfect scene, a family out catching a feed of crabs, great stuff.

This tinnie had a Bimini added to it that was quite large and provided a good amount of shade for the tinnies occupants a bit of good thinking I thought.
A couple of hours later I observed the same boat having quite a few uncomfortable moments trying to come across the estuary when the south westerly was blowing 10-15 knts the water had some white caps on it and the family had decided to call it a day, smart thinking.

When hit by gusts of wind this boat healed over alarmingly and you could see that the occupants where a bit upset at this. I watch them get safely back to the ramp and didn't give it any further thought until I got home, then thought how a real pleasant day on the water could have ended with a bad if not serious outcome caused by the bimini acting as a sail and causing a light displacement boat to take on a large lean/list. Happily all turned out ok, the lesson I learnt was think about what at first seams a simple mod can have unthought-of consequences.

Am I advocating you should consult a marine architect for every time you do something to your pride and joy, absolutely not.
But we all need to thing it through fully.

ranmar850's picture

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A common sight

Wed, 2017-08-02 08:31

 WRT what Meglodon said, people adding these huge biminis in light tinnies always makes me uneasy, for the reasons he gave. Cheap and easy to  obtain, they are very popular, and "seem" to makes sense. Then some think they can get even better, and add clears, and you are deep  into dangerous territory. I've seen some examples of massive clears fitted to small boats, and they will be making the boat almost unmanageable in a fresh breeze. Even a 5m runabout style, fitted with barwork and a full set of clears to enable the driver and passenger to stand up, in a boat that was designed to be driven sitting down, is adding a real element of risk, IMO, and certainly making handling more difficult in wind. And if there is no wind, you don't need clears.  You  just can't make a small boat into a bigger one by wrapping it in barwork and clears--you are actually making it less of a boat.

But the problem is certainly not limited to the owners of tinnies who don't want to get wet/sunburnt. I got into a bit of an argument on another forum with a bloke who was heavily modifying a, from memory, 6.5m (?) boat. He was building a big ali hardtop onto the boat, which was originally supplied with a soft top , with a stack of rod holders. OK, common enough, but this thing was HEAVY. Someone was asking why he was building it so, and he replied that he needed to load up the roof with swags, gear, and fuel--yes, fuel, he was having racks made to carry jerry cans, quite a number of them. Unbelievable, and he couldn't see the issue, because he already had to carry the extra fuel, couldn't see the difference between having it on deck and having it shift his C of G by putting it on a roof. Not to mention the rest of the gear he was proposing carrying up there. The hardtop alone, with glass, was around 300kg. 

On the subject of excessive clears, I'm sure someone will take me to task, because I've seen more than one members' boat on here with what I would consider grossly excessive amounts of added windage, ie, clears. So be it.   On the subject of the Returner, rumors flew that she was a real pig, as those small steel hulls can be. I'll leave it at that, except to say that I personally knew Mason Carter, he grew up in Kalbarri  at the same time as my kids. Tragic for Barry ,Bridget and the other kids.