Transom Failure

[Bigmuz7]

After only 80 hours use, my Northcraft transom has had enough.. for an 8.5M boat and rated to 300hp, my 275 Verado has been too much for it, and the transom has failed. I only do 'light cruising' and it is clear the transom has failed due to a manufacturing defect. Thankfully my dealer is sorting out Northcrafts shortfalls, all be it, much more slowly than I would have liked ..But ..finally ... I am satisfied.. their methods are correct .. my question is .. as the boat was coded to Cat B spec on purchase, how did Northcraft obtain this coding in the first place?and after the dealers modifications... how do I retain it ?.. shouldn't they retest it?

It should be said.. Northcraft were asked to repair the transom failure after it was noticed,.. and their effort was nothing short of laughable.. They have produced a great hull (copy) but have blamed this hull failure on the Verado and its installation..

Its the last Northcraft I'll be buying .....And this is my 3rd ...

Disappointed owner

[Downhilldai]

What has actually failed and what is being done to remedy it?

[codprawn]

Sorry to hear about that - how about some pics - what kind of failiure are we talking?

[Bigmuz7]

Its suffered a delamination due to a lack of bonding /or strength from the stiffenening knees that support it

[codprawn]

Worrying but shouldn't be too hard a job to fix??

[Bigmuz7]

Originally Posted by codprawn

Worrying but shouldn't be too hard a job to fix??

Well they have completely relaminated the transom and have removed the stiffening knees, to be replaced by two stainless struts which will be connected to brackets which are bolted to the bearers (which are bonded to the hull) under the floor. IMO it will be stronger than the original.

[Richard B]

It looks suspiciously like (as per JW's advice to Bruce B on consoles) that your "knees" are only bonded to the surface lamination on the inside of the transom. Given that you (or the fitter) had added a steel plate to the back of the transom for the o/b, it seems difficult to reasonably argue that the outboard installation is to blame!

Edit - is that ply all sealed? Looks a bit "naked" in the pic!

[Bigmuz7]

Originally Posted by Richard B

It looks suspiciously like (as per JW's advice to Bruce B on consoles) that your "knees" are only bonded to the surface lamination on the inside of the transom. Given that you (or the fitter) had added a steel plate to the back of the transom for the o/b, it seems difficult to reasonably argue that the outboard installation is to blame!

Edit - is that ply all sealed? Looks a bit "naked" in the pic!

Yes the original bonding of the knees was the problem .. they didnt have a good bond to the transom .... a slight misgiving on such a craft I am really Pissed off at how Northcraft have dealt with this though .. you should have seen how they attempted to repair it

A survey proved there to be large boss areas either side of the knees, on the first photo

.. yes Richard the bearers are sealed ok,.totally glassed,.. or as far as I can tell anyway

[jwalker]

Originally Posted by Bigmuz7

Yes the original bonding of the knees was the problem .. they didnt have a good bond to the transom ....

The bond between the fibreglass and the transom ply may or may not be the best but a bond between ply and fibreglass is always poor. The ply should not be the main strength of the transom. In a way, the ply is just a filler and spacer between two sturdy layers of fibreglass to make for rigidity and in your case the fibreglass has not been sturdy enough. I can't see a problem with the original knees. The laminating around them appears intact in your first photo. It is the laminating over the surface of the transom which has failed. The knees also look to be about 50mm thick and fairly substantial. Of course, I can't see the original joining of the knees to the deck and hull structure. Be mindful that strengthening one area transfers the load to another area.

I'm not going to comment on the method of repair but....

[Downhilldai]

Who's doing/done the work on it?

[Nasher]

Stainless legs need to be designed very carefully, in my opinion they were the only design fault on the smaller Flatacraft range.
Its very difficult to stop small amounts of movement around the bolts becoming large ones over time as they allow the transom to flex.

I'd have thought the original style knees bonded in over the stringers and attached through into the ply with Stainless steel screws before being over-bonded in place would be a much more suitable repair.

Who is doing the work? and what sort of guarantee have you got from them or Northcraft now that the design differs from its original spec?

Nasher

[codprawn]

I would have been inclined to drill some large holes through the transom and into the knees and insert 1" wooden dowels liberally coated with epoxy.

[Bigmuz7]

Originally Posted by Nasher

what sort of guarantee have you got from them or Northcraft now that the design differs from its original spec?

This is the question I was asking in my original post. How did Northcraft clasify the hull to Cat B, and after this work, how do I retain it, does the hull have to be retested ?

It was my understanding that the hull was a heavier design with extra stringers or ribs heavier lay up etc, amongst other things, to meet cat B spec.

Ok so its two questions. What I'm getting at with the second one, is,.. shouldnt it have been less likely for a cat B hull to fail in this manner ? As I have photos inside the hull from the stern and can see no evidence of extra stiffening.

[Bigmuz7]

After more research today, the best info I can find is on this link here

http://www.ceproof.com/recreational_...htm#Categories

And a chat with one of the chaps there, suggested there is no obligation for the category approval to be 'maintained' as it is a snapshot of the crafts manufacture which allows it to be sold throughout Europe, and it is not a requirement or standard which requires testing. Seems a bid odd why they bother CE marking them with different categories then ? I cant find any info other than hull length which designates what a cetegory is.

[Cookee]

As a manufacturer I won't comment on the hull directly, but as far as the CE system goes there is nothing that actually says a cat b boat has to be stronger than a cat c - if they are both designed for a 300 they should be as good as each other. The whole CE thing is actually misleading in my opinion as the general buying public can be misled into thinking that a cat b boat is better than a cat c - in fact it will need to get through much more testing (quite expensive), but to pass cat c we have to provide layup schedules, fill it full of water and drain it out within a time frame, perform handling tests and it has to be generally up to the job.

In short a CE category b boat isn't necessarily any better - it just passed some tests a cat c boat didn't take!

In addition I think the CE rating of this boat has nothing to do with the issues that you're having.

[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..............

[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

[Bigmuz7]

Originally Posted by Nasher

Its very difficult to stop small amounts of movement around the bolts becoming large ones over time as they allow the transom to flex.

This was certainly a concern of mine, IMO some sort of small hatch beside the brackets is the way to go, since a service inspection of the fixing bolts is a must, at regular intervals, I didn't consider the bolt grade (x4 per bracket) being good enough not to loosen slightly during use, the repairer simply used nylock nuts on standard metric threaded bolts, personally, I'd prefer double lock nuts and some type of marine grade stud lock or lok-tite, also a plate on the inside of the through bolt on the stringer instead of simply washers on the nut side, so as to spread the load, as the stringer is essentially compressible, and hauling up a bolt and nut will never stay solid due to that compression, then I thought maybe not, nylock might suffice, as due to the compression, a nip up now and again might be neccessary, although with a spreader plate, hopefully this would be minimised, but as always Gents, your thought are welcome.

Personally I'm surprised & disapointed the manufacturer has acted in the way they have since like it or lump it.. the plate says 300HP and its only done 80 hours for Gods sake. Its a cop out for them to try and walk away from this, which is what they have done.

If this boat was in commercial hands, I'm sure the story would be different !!

[bedajim]

Originally Posted by Bigmuz7

This was certainly a concern of mine, IMO some sort of small hatch beside the brackets is the way to go, since a service inspection of the fixing bolts is a must, at regular intervals, I didn't consider the bolt grade (x4 per bracket) being good enough not to loosen slightly during use, the repairer simply used nylock nuts on standard metric threaded bolts, personally, I'd prefer double lock nuts and some type of marine grade stud lock or lok-tite, also a plate on the inside of the through bolt on the stringer instead of simply washers on the nut side, so as to spread the load, as the stringer is essentially compressible, and hauling up a bolt and nut will never stay solid due to that compression, then I thought maybe not, nylock might suffice, as due to the compression, a nip up now and again might be neccessary, although with a spreader plate, hopefully this would be minimised, but as always Gents, your thought are welcome.

The under floor part of the bracket could of been twice the length with a few more bolts and it is begging to have a plate fixed to the inside to spread the load. If its not sealed why not ask them to do it and double nut them its your boat !

Will the transom have a large plate on the outside with the new brackets bolted all the way through ?

James

[Bigmuz7]

Originally Posted by bedajim

Will the transom have a large plate on the outside with the new brackets bolted all the way through ?

James

Yes it will have, the transom its self is 3 inches thick at the top now, so its pretty heavy duty.