MAIB report - RIBQUEST owners

[9D280]

Originally Posted by codprawn

Self tappers are the spawn of the Devil - I would NEVER use them on anything!!!

Better not have too close a look under the bonnet of your car then........

"self tappers" or more accurately thread forming screws are no better or worse than nuts & bolts IF they are spec'ed properlty for the application. In some cases they actually hold better, because the threads of the screw totally fill up with the material they are screwing into, whereas a "standard" machined thread there's only about 1/3 of the thread (and most of it at the thread tip where the material is thinner) actually doing anything due to the manufacturing tolerances you need to make sure any nut of a given size will fit on any bolt.

There are numerous types of thread formers, some which are only specified for use with certian materials due to the shape of the treads. Assuming whoever used the screws spec'ed them properly, and did the maths to work out a suitably safe number of them to use, if the sealant didn't work properly (for whatever reason) then when the wood goes soft even thru' bolting is going to make no difference - it's going to pull out eventually!

And if you're fixing a console down, just how do you get under the floor to put the nuts on?

[tinker]

Self tappers as good as 'nuts and bolts'

[Matt]

IMVHO self tappers into ply backed glass can hold OK, althuogh requires sealing. Self tappers into any glass only - bad move. Not only does it tend to not have much holding power, the minute crack in the gel created as you screw in often propagates if the unit flexes.

Purely based on my own experience, no googling or recycling other peoples opinions (jw )

Originally Posted by 9D280

And if you're fixing a console down, just how do you get under the floor to put the nuts on?

[Cookee]

Just to add the way we do things - on our smaller RIBs with regular consoles they are fibreglassed down to the deck, we feel one advantage apart from the strength is there are no extra holes in the deck.

[Poly]

The MAIB have now got round to officially publishing the safety bulletin relating to this incident:

http://www.maib.gov.uk/cms_resources/SB2-07.pdf

[jwalker]

Hey Mollers, there's an example of good, professional workmanship,... and you wonder why I'm rather scathing of them.

[K&S]

Hi, it says in the report that 'ribquest have ceased trading'.

I found this on boats and outboards today

http://www.boatsandoutboards.co.uk/view/RIQ002

Does anyone know the story? Is it a new manufacturer? Have they changed the way seats are attached?

[Rogue Wave]

Originally Posted by Matt

IMVHO self tappers into ply backed glass can hold OK, althuogh requires sealing. Self tappers into any glass only - bad move. Not only does it tend to not have much holding power, the minute crack in the gel created as you screw in often propagates if the unit flexes.

Purely based on my own experience, no googling or recycling other peoples opinions (jw )

I don't think self tappers are designed for ply and therefore not suitable. . So it's all fine until the nobber thats installing eveything gives it too much arm and breaks the thread in the ply/glass. I believe this is known as graunching, well it is in my world!


agree that straight into GRP is utterly unacceptable
I wouldbe happy to use self tappers to hold something down that also had some Sikaflex in the join.

[Limey Linda]

Having read the report it not very difficult to conclude that that is just a terrible piece of workmanship. Whoever was responsible, including the company owner should be shot. Only heaven knows what other crap is included with that make of boat. Was it made in China?

Nothing wrong with S.Tappers and urethane adhesive if done properly. In fact the only reason I would not use it is because I consider it a permenant installation.

[Mollers]

Originally Posted by Limey Linda

Having read the report it not very difficult to conclude that that is just a terrible piece of workmanship. Whoever was responsible, including the company owner should be shot. Only heaven knows what other crap is included with that make of boat. Was it made in China?

Nothing wrong with S.Tappers and urethane adhesive if done properly. In fact the only reason I would not use it is because I consider it a permenant installation.

Steady, many top US brands now out-source to China for manufacturing and some real 'crap' is still 'made' in the US often using cheap immigrant labour, sorry 'labor'.

[jwalker]

Originally Posted by Rogue Wave

I don't think self tappers are designed for ply and therefore not suitable. .

I think they are eminently suitable when used across the ply because the plies fit reasonably into the threads and make for a good hold. The problem arises when;

Originally Posted by Rogue Wave

the nobber thats installing eveything gives it too much arm and breaks the thread in the ply/glass.

Part of the problem is the poor quality of most of the marine ply. It is possible to source good stuff but I've not found it readily available. In good ply, a stainless selftapper will snap before the ply thread strips.

I agree with Linda.

that is just a terrible piece of workmanship.

And, six self tappers just isn't going to do it for that application.

[Matt]

I just bought a load of ply from these guys after hunting round for something more specific than generic "marine ply" of unknown origin.
3 Choices of BS1088 ply depending on your requirements. Gaboon, Mahogany or Sapele.
http://www.robbins.co.uk/Pdf%20Files...wood_guide.pdf

[Wight Skipper]

http://www.ybw.com/auto/newsdesk/200...bogeneral.html

(Sorry if this has already been posted.)

[SeaSkills]

I've always felt a bit nervous with consoles and seats that are simply screwed to the deck. I've only had one boat built that way, and couldn't wait to replace screws with decent bolts through the deck - not easy to get access, but at least you feel a bit more confident when the boat starts bouncing about a bit.

[J S]

Originally Posted by SeaSkills

I've always felt a bit nervous with consoles and seats that are simply screwed to the deck. I've only had one boat built that way, and couldn't wait to replace screws with decent bolts through the deck - not easy to get access, but at least you feel a bit more confident when the boat starts bouncing about a bit.

I have never felt nervous in Humbers which i have driven many, because they use plenty of decent sized screws.

James

[Cypman]

In my experience self-tapping S/S screws are more than up to the job, BUT you must use sufficient to ensure security. Humber have used this method without problems for as long as I can remember, spacing the scrwes approximately 10-15 cm apart thus using some 20+ screws for each seat. Hence the seats remain in place!!

[John Kennett]

Originally Posted by Wight Skipper

(Sorry if this has already been posted.)

That's OK, it was only a month or so ago!

I've merged the threads now . . .

John

[Rogue Wave]

Originally Posted by jwalker

Part of the problem is the poor quality of most of the marine ply. It is possible to source good stuff but I've not found it readily available. In good ply, a stainless selftapper will snap before the ply thread strips.

I always though that self tappers were designed for sheet metal but If your saying they were designed for plywood then that's good enough for me.


If I've snapped my self tapper, in my good ply, then have I still got a bad fastening?

Given a few years when the ply becomes a little moist and the screw a little rusty what gives first ?

[jwalker]

Originally Posted by Rogue Wave

I always though that self tappers were designed for sheet metal but If your saying they were designed for plywood then that's good enough for me.

Stu, I think you are right, real self tappers are designed for cutting into sheet metal but they are made from very tough, hard steel. Stainless selftappers are not much use for that because they are too soft and also they tend to pick up and tear. I think they are pretty much just a style of screw which has good holding, in the same way as twinfast wood screws have just about superseded normal wood screws.

If I've snapped my self tapper, in my good ply, then have I still got a bad fastening?

I wasn't meaning that. It was just an illustration of how strong and durable a good quality plywood can be. It's not specifically a marine ply problem, most of the commonly available plywoods are softish in nature. A piece of quality birch ply is very strong.

I've got a couple of offcuts of good quality marine ply which came from a Zodiac and a piece which was cut from my Humber. I'll take a snap of them to show the difference just to sorta complete this thread. Having said that though, the bits of Humber have been lying out in all weathers for the best part of 4 years and they're still ok, so the resistance to weathering of the wood and adhesive must be alright. On my previous Humber, all the fittings were held to the deck using selftappers and silicon, including a 50 gallon stainless tank, and none of them came adrift, the deck didn't leak water either. On my present Humber, the trimtabs are held to the transom with selftappers and they must take some battering but they seem fine so I think it is mainly down to how well it's done. Lots of silicon as a sealer and the fattest screws you can lay your hands on. Thickness is better than length but both is the best....

[Limey Linda]

Good post JW. problem is that most folks ( including boatbuilders) do not know how to do it properly. D'ont have time to write it up at the mo. However, it is not as simple as drilling a hole and whacking in a screw with a Black and Decker, as I know you know.