Transom Failure

[Bigmuz7]

Originally Posted by Andy Gee

I noticed a blue Northcraft at Rothsay the other weekend with a Verado on it. It had some rather substantial stainless knees/supports fitted to the transom. Might be worth trying to get a hold of the owner and see if he has had the same problems.
HTH
Andy

Thanks Andy .. will keep a look out

[Endeavour]

Can you put on a few more pics.
Is the deck ply and grp?

[Cookee]

Originally Posted by codprawn

i think the whole system should be scrapped - my 9m and my little Quicksilver are both rated C - I wonder which I would prefer to be on in the rough..............

And it has been discussed on here that the CE procedure may not have been rigidly adhered to in the case of your manufacturer as well

[andym]

I've got the blue northcraft spotted in Rothsay - the stainless legs got retro fitted after less than 10 hours running . More issues now coming to light - not what I would expect from the reputation of the boats . Dealer has been very good but all a bit concerning !

[Trickdog]

Andym I purchased a new Northcraft 6.3 metre RIB earlier this year, so I'm interested to hear what issues you have had with your boat. Can you elaborate? Would like to know if there is anything I need to look out for!

[andym]

They are good sea boats just watch the transom . The issue appears to be the weight of heavy modern four strokes hanging of the back of them . Shouldn't matter but there you are .

[Bigmuz7]

Originally Posted by Trickdog

Andym I purchased a new Northcraft 6.3 metre RIB earlier this year, so I'm interested to hear what issues you have had with your boat. Can you elaborate? Would like to know if there is anything I need to look out for!

Trickdog The 6.3 was the best Northcraft I had .. good boat

[Bigmuz7]

Originally Posted by andym

They are good sea boats just watch the transom . The issue appears to be the weight of heavy modern four strokes hanging of the back of them . Shouldn't matter but there you are .

Why after 10 hours Andy ? what did you you see ?

[nikster]

chaps,

people need to understand that these boats moulds are not new - the technology for making ribs is increasing by the day as is the powerplants that we hang on the back.

I doubt very much that northcraft moulds are CAD designed, nor have they been in test tanks to prove capability, mosty of the RIB moulds we have today are moulds from 10/15 years that have been passed down the line.

I can tell you from experience that a proper brand new mould from scratch costs in excess of 40k...... the point i am making is that not many people stress test or fatigue test moulds/ powerplants as the industry does not have that type of investment available ......they.... calculate EU requirements versus empty weight versus transom thickness = power rating x kw

No audit procedure, no batch numbers of kit used, no stress testing, nothing - just whack it in the mould, lay it up, when its cured, bung the tubes on, hang the donk on the back, fit it out with whatever we have and try and marry it up with what the client wants - tea break - ready for friday just in-time for the weekend.......!!! maybe i have just been in this game toooo long.... more creme de month - i say!!!!!! hooorarrrr

[alystra]

Originally Posted by nikster

chaps,

people need to understand that these boats moulds are not new - the technology for making ribs is increasing by the day as is the powerplants that we hang on the back.

I doubt very much that northcraft moulds are CAD designed, nor have they been in test tanks to prove capability, mosty of the RIB moulds we have today are moulds from 10/15 years that have been passed down the line.

I can tell you from experience that a proper brand new mould from scratch costs in excess of 40k...... the point i am making is that not many people stress test or fatigue test moulds/ powerplants as the industry does not have that type of investment available ......they.... calculate EU requirements versus empty weight versus transom thickness = power rating x kw

No audit procedure, no batch numbers of kit used, no stress testing, nothing - just whack it in the mould, lay it up, when its cured, bung the tubes on, hang the donk on the back, fit it out with whatever we have and try and marry it up with what the client wants - tea break - ready for friday just in-time for the weekend.......!!! maybe i have just been in this game toooo long.... more creme de month - i say!!!!!! hooorarrrr

Ah! Yes. But if they want to stay in business after this thread, they'll get some thicker plywood for the transom and knees, add a couple more layers of fibreglass and then have a beer, knowing they responded promptly to customer's needs and then advertise the virtues of their R & D department.

[Bigmuz7]

Originally Posted by nikster

chaps,

people need to understand that these boats moulds are not new - the technology for making ribs is increasing by the day as is the powerplants that we hang on the back.

I doubt very much that northcraft moulds are CAD designed, nor have they been in test tanks to prove capability, mosty of the RIB moulds we have today are moulds from 10/15 years that have been passed down the line.

I can tell you from experience that a proper brand new mould from scratch costs in excess of 40k...... the point i am making is that not many people stress test or fatigue test moulds/ powerplants as the industry does not have that type of investment available ......they.... calculate EU requirements versus empty weight versus transom thickness = power rating x kw

No audit procedure, no batch numbers of kit used, no stress testing, nothing - just whack it in the mould, lay it up, when its cured, bung the tubes on, hang the donk on the back, fit it out with whatever we have and try and marry it up with what the client wants - tea break - ready for friday just in-time for the weekend.......!!! maybe i have just been in this game toooo long.... more creme de month - i say!!!!!! hooorarrrr

Nikster ..I'm not new to RIBs.. so.. I think I know a bit out the gear .. but if the manufacturers plate says 300 ..sooo 275 should'nt be a problem. I made a point earlier in this thread about the way people 'code' their boats and I've learned from that.

The point I made was ..duh .. dont code your boat for 300 when you'd be lucky if it takes 200 .. and how do you rate the transom in the first place .. perhaps you could enlighten us on that because its kind of .. erm important?

[Bigmuz7]

Originally Posted by alystra

Ah! Yes. But if they want to stay in business after this thread, they'll get some thicker plywood for the transom and knees, add a couple more layers of fibreglass and then have a beer, knowing they responded promptly to customer's needs and then advertise the virtues of their R & D department.

I doubt it..... after they way I was treated .. you would laugh at the repair job they did on my transom...... I'm saving this gem

[Cookee]

Originally Posted by nikster

chaps,

people need to understand that these boats moulds are not new - the technology for making ribs is increasing by the day as is the powerplants that we hang on the back.

I doubt very much that northcraft moulds are CAD designed, nor have they been in test tanks to prove capability, mosty of the RIB moulds we have today are moulds from 10/15 years that have been passed down the line.

I can tell you from experience that a proper brand new mould from scratch costs in excess of 40k...... the point i am making is that not many people stress test or fatigue test moulds/ powerplants as the industry does not have that type of investment available ......they.... calculate EU requirements versus empty weight versus transom thickness = power rating x kw

No audit procedure, no batch numbers of kit used, no stress testing, nothing - just whack it in the mould, lay it up, when its cured, bung the tubes on, hang the donk on the back, fit it out with whatever we have and try and marry it up with what the client wants - tea break - ready for friday just in-time for the weekend.......!!! maybe i have just been in this game toooo long.... more creme de month - i say!!!!!! hooorarrrr

As a manufacturer myself you're going to have to explain how a CAD designed mould would have any bearing on the strength of a transom?

In my opinion the strength of any boat lies in careful consideration of the stresses involved and making something "up to the job" and nothing more than that - of course how you get to that decision is the tricky bit. I am sure our surveyor makes all sorts of calculations as to the strength of everything when it comes to doing the CE stuff, but at the end of the day if we over stress everything and it all stays in the same place as it came out of the mould then it works for me - see photo!

The problem is that some manufacturing methods of attaching knees to transoms and the transoms themselves have not changed since the days that 100hp 2 stroke would be considered a lot, and the same construction would suffer with a 300 Verado on the back.

The only answer is to look at second hand well used examples of boats that have at least the same amount of HP you're thinking of putting on a new boat and hope that it isn't a Friday boat!

[ALANT]

I had a 7.4 Northcraft the transom was really thick had a 225 opti on it, boat was coded so lots of weight and upto 10 divers. Can't remember the thickness of transom but the donkey motor bracket would fit as it was to thick.
Have they reduced the thickness?? shame I thought the boat was great and most seem to be used for commercial purposes.

[nikster]

cookee...... im not sure i know of any Rib mfr's who have a Hydronamics expert on their books with the Savitsky spreadsheeds for working out all loads and stresses... when you have this data and model then put in your gucci design in to the cad machine, it works it all out to ensure nothing breaks and gives you the smoothest / optimum ride.

Thats why Halmatic cant make ribs for 30k!!!! the MOD takes no chances and Avon, Halmatic etc have departments that do nothing else other than model new boats and designs and work out the stresses, flexing momentum, maximum KW rating and rig the boats to a HUMS system to datalink the stresses through its operating environment and better understand computational fluid dymnamics and hydronamics.

Making fast ribs is fun, but making them properly that last for tens of years and remain structually sound for their life is something that the Rib industy is not renowned for.....!

I've only been messing about in them for 30 years, but as the saying goes - you get what you pay for, some rib mfr's are great, others are ok, and some we laugh at - but each to their own...

[Lugnut]

Originally Posted by Cookee

As a manufacturer myself you're going to have to explain how a CAD designed mould would have any bearing on the strength of a transom?

I don't know what the original poster had in mind, but I personally would assume (yeah I know what they say about that, LoL!) that if the mold was designed in CAD, the RIB itself would be as well. If so, a structural analysis can be performed and weak points identified and redesigned.

Regards,

Chuck

[codprawn]

I seem to remember the Millenium Bridge and our local harbour defences were both designed by experts using CAD - I don't think Brunel had access to computers and yet I would far rather trust his engineering............

[nikster]

in the south atlantic i much preferred Halmatics...... and my one definately was a CAD design...

[Lugnut]

Originally Posted by codprawn

I seem to remember the Millenium Bridge and our local harbour defences were both designed by experts using CAD - I don't think Brunel had access to computers and yet I would far rather trust his engineering............

Shrug... There's an old saying when it comes to computers. "Garbage in, garbage out"

It's just a tool, but one still has to know how to use it.

[codprawn]

Originally Posted by Lugnut

Shrug... There's an old saying when it comes to computers. "Garbage in, garbage out"

It's just a tool, but one still has to know how to use it.

Very true - unfortunately the engineers they tend to employ today are taken on for their management skills rather than their engineering skills!!!