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Old 09 September 2004, 12:28   #1
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Flexing Floor! (and other stuff)

A bit of advice please from the wise and knowledgeable of the RIBnet Forum.

I had a look at a Northcraft 6.2m RIB today. While on sea trial I felt the floor ‘flexing’ beneath my foot. I could feel the floor moving slightly either side of what I guess is a transverse strengthening rib. On closer inspection there are some hairline cracks running transversely along the top of this rib. The guy driving felt nothing even after I pointed it out.

This rang the alarm bells for me and I walked away from the RIB. I have never come across this before but my experience is with smaller RIBs. Has anyone any experience or knowledge of this phenomenon? Is it as serious as I thought?

Another thing I noticed; how many RIB manufacturers put the (petrol) fuel tank and battery in the same compartment (as is the case with this Northcraft)? To me the risk of fumes+spark=BOOM! would make it much more sensible to locate the battery elsewhere.

Many thanks


Andy Beach
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Old 09 September 2004, 12:56   #2
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Andy the deck of any boat should not move according to a cheif Naval Architect who designs super fast cruisers mate of mine that has happened to be with me today. Also, he says, if there are hair line cracks, on the deck it means that either the boat has been used heavily/mistreated and heavy items have banged on the deck or that is of very poor built.

Re Fuel tank and batteries been together a BIG NO NO NO!!

Hope I helped
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Old 09 September 2004, 13:00   #3
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Andy, If the floor was flexing it probably means that (assuming its marine ply overlaid with fibreglass) that water has got in and the ply is rotting. Since replacing a floor on a rib usually is a big job you did the right thing in walking away IMHO!
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Old 09 September 2004, 13:20   #4
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Quote:
Originally Posted by Alan
Andy, If the floor was flexing it probably means that (assuming its marine ply overlaid with fibreglass) that water has got in and the ply is rotting. Since replacing a floor on a rib usually is a big job you did the right thing in walking away IMHO!
No argument from me .

Our club RIB had the same problem and we had to re-glass the whole rear section. But we do have dive cylinders dropping on it twice a week .

There is a European regulation regarding fuel and battery compartments. The only way around it is to a sealed battery box that has an external breather.
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Old 09 September 2004, 16:01   #5
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Thanks for the responses

Many thanks all - I'll keep looking.

Andy Beach
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Old 09 September 2004, 16:05   #6
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Quote:
Originally Posted by tue
There is a European regulation regarding fuel and battery compartments. The only way around it is to a sealed battery box that has an external breather.
For the record, I did not look to see if the battery box was sealed so it may well comply with regulations.

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Old 09 September 2004, 17:04   #7
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Does this sealing have to be retro fitted?
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Old 09 September 2004, 17:58   #8
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When I'm slamming waves I have my feet wedged under the tubes for support, I feel my floor flexing. I haven't got my feet on the Fiberglassed wood deck but on the inside of the hull (between deck and tubes), is this OK? I have hairline cracks where hull and deck meet, I guess this is to be expected!

Andy
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Old 09 September 2004, 18:14   #9
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Quote:
Originally Posted by Andy Beach
I felt the floor ‘flexing’ beneath my foot. I could feel the floor moving slightly either side of what I guess is a transverse strengthening rib. On closer inspection there are some hairline cracks running transversely along the top of this rib...This rang the alarm bells for me and I walked away from the RIB.
No matter what anyone thinks, you wouldn't heve been happy after buying the RIB, so best to do what you did.

For what it's worth, before I bought my RIB I spent a season cruising with BIBOA members and observing what RIBs (and other equipment) they used. Northcraft didn't feature anywhere, and I've never felt a RIB's floor flex under my feet.
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Old 10 September 2004, 03:08   #10
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Our dive club had two ( early) Northcrafts) - 5.5 and 5.9m.
BOTH suffered similar issues - flexing , cracking and delaminating decks, and hills splitting along the chines !!!
A couple of features - insufficiennt stringers ? in the build up - and a lot of wood unglassed ........ add water .......and ..... sponges
The hulls were particularly thin which I guess was a feature of the low cost build but in the end ( 2000) we scrapped them as unseaworthy
......... I am sure the latest ones are much better designed and built ????!! but I personally wouldn't ........
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