Could so easily have been a disaster

 I am recounting this tale with the permission of the boats owner.   A few years ago he had a 3.5 tonne custom made trailer manufactured for his boat, the boat was weighbridged fully loaded and came well within that load capacity.

Returning to Perth from Coral Bay on the June long weekend and travelling at speed just north of the 440 roadhouse the draw bar snapped causing loss of control, thankfully there was no oncoming traffic of we might well have been looking at more fatalities.  Lodging claims for the vehicle boat and trailer whilst the the car and boat were met by insurers the trailer was denied.  The reason for the denial was in no way related to the trailer being over loaded. An engineer appointed by the boat insurer determined that it was under-designed and that the steel used in the draw bar failed to meet Australian Standards.  Welding near the point of maximum bending stress had further weakened it and it failed through brittle cracking originating around the welded surface and then through complete shear failure.

The owner, through a fishwrecked member, came to me for advice. I had pretty strong views but wanted an engineer to look over the photos to comfirm so Seakem (Andy) was kind enough to review both the asessors report and the photos. Based on his thoughts I asked the owner to pay for and secure a mettalurgical report which confirmed our views. We then proceeded to make a claim against the trailer manufacturer for negligence.  Four months later and after much toing and froing he today signed a discharge securing reimbursement of the indemnity value of the trailer from the liability insurers.  A great outcome all around but it could so so easily have ended in tragedy.  


I see regularly when I travel north fisho's treating their boats like glorified trailers, loading them up to the gunnels with camping and other gear, freezers, beer (you name it and they load it) potentially overloading the trailer and risking a similar failure and putting at risk insurance coverage on both the car and boat. Please think twice when heading north even though this had nothing to do with overloading I hope it acts as a cautionary tale.

Image Upload: 

Swompa's picture

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You continue to demonstrate

Fri, 2019-10-18 14:22

You continue to demonstrate that you are a genuinely good bloke Sunshine. Your beer fridge must always be full!

Very lucky for the owner in the sense that it could have been a very different ending, even before the talk of insurance started.

uncle's picture

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Yep well done

Fri, 2019-10-18 15:29

 Beer time.


all aggressive fish love bigjohnsjigs

ranmar850's picture

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well done that man.

Fri, 2019-10-18 15:54

 bad place to have anything come adrift. A bit hard to tell from the picture, and I know it was put down to poor design, ie, welding at a maximum stress point, but what dimension material was used? RHS or SHS, hard to tell from the pic, what size and wall thickness? 

sunshine's picture

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It was RHS

Fri, 2019-10-18 16:19

 125 X 75 X 2.7mm.    even at 3.00mm would still have been undersized 

kirky79's picture

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Fri, 2019-10-18 15:58

That would of been a bloody scary situation. Well done to all involved in getting a good result.

quadfisher's picture

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Treat that drawbar well.

Fri, 2019-10-18 16:39

 Good outcome from a bad start. 

 I have made a few trailers for my drag and 4wd  quads and friends garden variety in the last few years , and go for robust strength over price or light weight.

(  ex boilermaker by trade) 

 I make extra sure of no welds or brackets are welded across beams , therefor not creating stress points , but was somewhat 

 dismayed when the inspector at the inspection centre ( private not govt of course) then proceeded to drill holes for the vin plate right 

 in the centre of the drawbar halfway between the hitch and trailer, before I could really react .( small drag bike trailer 75mmx 50mm drawbar)

 Now i realize there only small 3mm holes but with 2 above each other on the cheeks of the rhs were possibly the max deflection or weight could occur,

strikes me as ill advised.,,,,,,,,,,,,, And these are the guys inspecting your work?

 So surely theres a better way of attaching those vin plates than comprimising the drawbar, which is prob the most important structural part of the frame.

 Not implying in any way it is , but that trailer has a similar join , junction to my 5m melride , so I will be under it today looking for cracks.


 EDIT , just seen sunshines measurements , my double quad trailer , single axle 5.5m long , carrying 800kg of bikes 

       I used 125mm x75 x  4mm wall thickness drawbar ( its around 10kg a metre) x2 of course as its a traditional a frame ,

       not a single drawbar like a boat   and i think something like 100x50 x 3mm cross beams and frame.



quadfisher's picture

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Some simple diagrams on stress points.( trailer)

Fri, 2019-10-18 19:55



sunshine's picture

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Main reason I posted this

Fri, 2019-10-18 16:49

 Was to hopefully encourage everyone to double check their trailers, you can bet I did, so I hope more will do the same .....if it saves one accident it would put a huge smile on my face. 

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Whew how close was that

Fri, 2019-10-18 17:02

A close escape from what could so easily have been a fatality, and a costly outcome.
Thankfully all has ended well with lessons for all trailer boat owners.

sea-kem's picture

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 It was always a disaster

Fri, 2019-10-18 17:15

 It was always a disaster waiting to happen, as Gordon has mentioned wall thickness was way under and then top it off with galv brittillising and no good.

I'm in the midst of my trailer rebuild and went to buy the springs ( 9 leaf )and the the trailer fella to go for the parabolic single leaf which makes sense as less corrosion as salt won't get between the leaves. He also told me of the trouble they had when they were galvanising the single leaf parabolics and that a few were coming back snapped as that's what galvanising does. They heat it then it's quenched so it work hardens the steel, not  a good mix. They don't do it anymore.

I'll just coat the springs and axle  with tar epoxy.

I've gone for 100 x 100 x 4 for the draw bar and 75 x 50 x 2.5 for the cross members up from the existing 50 x 50 and also adding an extra one in. 


Love the West!

ranmar850's picture

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2.7mm?? For 3.5 tonne trailer?

Fri, 2019-10-18 19:15

 jeez, why didn't they just use patio tube?  Agree with all the above, 4mm for that task, even for a 2 tonne trailer, IMO. I tend to over-build things, I know, but they never break.  I upgraded a Roadmaster once, after consulting them, needed to go above the 1400kg  existing rating to closer to 2 tonne to match the boat that was on it when I bought it. They got me to measure the drawbar thickness---the engineer, or the person acting in that capacity, said I could go to 1800kg( with tandem) with a 2.8mm wall thickness, or 2000kg with 3mm. I was honest, measured it at 2.8MM, they issued a new plate upgrading to 1800KG was enough for that rig. When I built a complete trailer, I used 75/50 and 75/75 4mm for all the SHS/RHS, and 6mm angle, for a 2 tonne boat trailer. You'll never break that one. 

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 What metallurgical test were

Fri, 2019-10-18 19:16

 What metallurgical test were carried out , out of interest?

sunshine's picture

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Hardness by Vickers to AS1817.1

Fri, 2019-10-18 22:05

Chemical by optical emission spectroscopy.  Microscopic examination of fracture surfaces established origin of fracture.

Conclusion on the failure was unequivocal. 

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 Had a mate with a bar

Sat, 2019-10-19 07:00

 Had a mate with a bar crusher and found a crack weld in the hull allowing water ingress. Bar crushed didn't know what hit them when he issued a NATA approved radiography report to them. In the end they swapped him a new hull. Helps being in the inspection game

sea-kem's picture

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 That's really interesting,

Sat, 2019-10-19 12:34

 That's really interesting, do you know what the fault was?

I'd like to know what NDT testing if any the hulls go through and if they oven temper them. So many factors can come into play, welder operator, material quality and even filler wire quality.

Traceabillity is the big thing these days and is becoming more mainstream. I've built DNV offshore skids and you literally have to compile a dossier on everything involved down to every section used being charpy tested. 


Love the West!

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 He's on this site, Winta1 

Sat, 2019-10-19 22:33

 He's on this site, Winta1  if he reads the thread. 

Next to no NDT I bet, welds on boats have never looked the same since I started in NDT. Material also is a big thing in my eyes, different grades etc, just because someone sells it in stainless steel doesn't mean you receiving a superior product.

sea-kem's picture

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 Agree, I get certs with

Mon, 2019-10-21 13:23

 Agree, I get certs with every order of stainless I place and once again stick with local suppliers. Ha ha it's the first thing I look at when eyeing off a boat are the welds. 


Love the West!

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More fatalities ?

Fri, 2019-10-18 21:42

Was anyone killed in this incident ?  


 My wife understands why I clean my rods n reels in the shower....


sunshine's picture

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No but luck was with them with no oncoming traffic

Fri, 2019-10-18 22:07

I have little doubt the outcome could have been much worse than some bent and broken steel.  

backlash's picture

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Sat, 2019-10-19 13:04

Good observation on the overloading piece.

ive been watching some fishing vids on YouTube where the guys are heading to remote locations and there is way too much gear in the boat.

lucky as you said that no one was hurt

timboon's picture

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 Fark that woulve been scary

Sat, 2019-10-19 14:09

 Fark that woulve been scary having that thing shunt you up the ass at highway speed...


I had a drawbar hitch snap on me on a tandem trailer with 4 x Hereford bulls in the trailer, i was only going about 40kms on a dirt road when i felt it go at the top of a slight rise, as soon as i came down the other side it shunted me sideways and the trailer tipped on the side...


Happens fast but certainly feels like slo mo!!


Quite a scary thought that the mob that built this trailer has built others before it...


Its a no brainer to over engineer, I'm sure Andy or Quadfisher would be able to enlighten us on costings for a length of steel going from 2.7-4mm? Surely this isn't going to be a major expense for the sake of longevity and endurance purposes.


I'd say that trailer would've lasted one trip into Ningaloo station before the hull was sitting on the corrugation....

sea-kem's picture

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 Probably another $50-60 p/l

Sat, 2019-10-19 18:19

 Probably another $50-60 p/l max mate, I'm trying to work out the 2.7mm thickness as you just cant buy that size. It's either 2.5 or 3mm, or they bought imported shite which is milled to whatever and is cheap. I only buy local tube from Orrcon/Bluescope. 


Love the West!

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I bet that

Sun, 2019-10-20 19:03

I bet the trailer landing on its side upset the cattle no end, glad you ended up ok how about the cattle you where transporting did they survive. 

quadfisher's picture

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Recycled washing machines?

Sat, 2019-10-19 21:22

 Agree , that unless your on a death wish , buy Aussie steel everytime, most steel suppliers carry both chinese (  or asian)  or Aussie , and the price difference

 is minimal on home jobs or small trailers etc.

 The imported stuff welds like crap , with small impuritys visible on the end grain, so therefor introducing them into the weldment ( or weld) 

 That imported steel probally wouldnt pass destruction weld  testing , so all structural or built to a standard fabrications will specify only steel built AS 4100.

 Homebuilt trailers are covered under the

 Its not that hard to conform to it ( as indeed you must for licencing) and anyone building , repairing or even maintaining small trailers below 4500kg 

 should have a read.

 The section below deals with techincal requirements , the safety factor bit x3 times normal load is telling, as the failed trailer above

   surely couldnt have achieved that

 And finally the section on drawbars, again did the above trailer pass or even aim for that standard?


 So using the above formula , converting newtons to lbs to kgs , my quad trailer drawbar with a ATM of around 1300kgs should be able to handle around

 2000kg without distortion or failure.



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Sun, 2019-10-20 06:44

so this is a good result in this instance.

There are likely other trailers from the same manufacturer still out there. Let’s hope they hold up better.

it would’ve been good to see some kind of mandatory recall.....or do we need to wait for a fatality for that to happen? 

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Date Joined: 02/01/12

Geez how ignorant can I beI

Sun, 2019-10-20 08:23

Geez how ignorant can I be

I would have assumed that as the insurance company had found that there was a problem with the engineering of the trailer purchased and in good faith by the owner, the insurer would have paid out all expenses and sued the manufacturer for their losses.

sometimes I wonder why we have insurance 

Great work there sunshine 

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Sun, 2019-10-20 21:37

 Good karma coming your way sunshine, once again. Great outcome and glad it wasnt a road fatality.


Site Admin - Just ask if you need assistance

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Well done Sunshine

Mon, 2019-10-21 08:53

Your contribution to this site is second to none

When I reached out to you on behalf of my friends, I was only expecting a generalised response.

Your detail and urgency to rectify this matter is exemplary

If their was an award for an outstanding fw member, it would have to go to you

Once again thank you for your help and contribution to this site

If your ever in Rockingham, please feel free to drop in to Mangles Bay Fishing Club, I owe you a couple of cold ones



timboon's picture

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Meg, Trailer landed on its

Mon, 2019-10-21 10:34

Meg, Trailer landed on its side in slo mo.... The 4 bulls brushed themselves off and walked off into the roadside bush...


All typically happened last thing in the day so then it was a shitfight finding the fucking things and getting them safely off the road in the dark...


Herfords - Mellow as generally speaking

Brock O's picture

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Great thread...well done

Mon, 2019-10-21 12:28

Great thread...well done Sunshine & Sea-kem....2.7mm FFS

still trying's picture

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 It's amazing the short cuts

Mon, 2019-10-21 13:10

 It's amazing the short cuts some companies take to save a few dollars at the time. 


 rather be fishing

sea-kem's picture

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 Yeah probably buying the

Mon, 2019-10-21 13:17

 Yeah probably buying the imported stuff, it's ok for benches and shit projects but not something as critical as a boat trailer. The suppliers also can only offer a cetificate of conformity no heat numbers or chemical analysis for traceabillity. It wouldn't surprise me the Chinese mill was skimming .3 of a mm off the sections and literally saving bucket loads of cash. I've seen the quality of Chinese steel sheet, all laminated around the edges absolute garbage. 


Love the West!

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 Awesome thread, read this

Mon, 2019-10-21 13:53

 Awesome thread, read this and got to work and checked our 3.5t flat bed trailer, bugger me if it isn't cracking from the welds down through the box section on each side where the A frame is welded to the chassis, never overloaded, towball weight always been well under, cracks were hidden under dirt that had washed down. So thanks guys for this, probably saved a disaster from happening 

little johnny's picture

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Ive had same trailer

Mon, 2019-10-21 19:58

Since 2011. Been in and out off water more than most. Pretty sure same company , mine still solid.i went 800 kilo above my boat weight.