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Old 22 October 2004, 16:32   #11
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Loa, Lbp, Lwl

Seb is both correct and incorrect.

For marketing the max length is an advantage. This will take into account rubbing starkes, bow snubbers etc.

However for RCD or coding calcs the LBP and LWL may well be taken into account. As an example the LWL (length on waterline) will come in to say coding calcs of anchor size. (LWL&LOA/2 if mem. serves right)

LBP (between perpindiculars) was easy to calculate on a traditional craft whereby the perps. were stem and rudder stock - for a RHIB more difficult to define. However it can still come into RHIBs whereby various n.arch calcs come into play particularily where in those calcs assumptions need to be made.

It would be great if we had a set of standards for RHIBs and my guess would be LOA,LWL, CB (block coefficient) and CP (prismatic coef). This would give indication of speed/planning ability/loading capability/overall stability. The problem though will be that we will all read too hard into the figures rather than listening to the experience of others !

Cheers

John
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Old 22 October 2004, 16:54   #12
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Old 22 October 2004, 16:57   #13
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Quote:
Originally Posted by John Kennett
For a boat that is sold as a 7.5 metre I would expect that to be the overall length, meaning a hull length of something like 6.5-7.0 metres. Do you know of any that are markedly different?

John
Yes Ribtec. someone needs to buy them a new tape measure. A 535 turned out to be more like 510 (LOA) and a 6.45 that was nearly 7.

Pete
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Old 22 October 2004, 17:05   #14
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Manos, you can call your boat whatever you want 535, 510, whatever, it doesn't have to relate to the boat length at all, it's just the designation of the boat, and may or may not relate to any particular measurement of it's length. It's nothing to do with BIBOA or the RYA
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Old 22 October 2004, 17:07   #15
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LOA should actually include the engine, if it protrudes further out the back than the toobs

Quote:
Originally Posted by Manos
Yes it is on ships and cruisers (although there you take into account the swimming platform which is not a part of the boat) and it suppose to be for RIBs but it an't.
When you say I want a 7 mtr RIB you mean a 7mtr total length (OVERALL) not hull length.
When you go to a marina and you have a RIB you pay fees not on the hull length but on the OVERALL lenngth i.e. the total length from bow to the end of the pontoons. When you go on a ship with the trailer you again pay fees on the total length (OVERALL) and not the hull leght.
As I said check with MOST (95%) of the RIB manufatcurers how they advertise the length of their boats and what the actual hull legth is.
As the word says OVERALL LENGTH in naval terms means from bow to the of the stern. On a RIB in this case is the end of the pontoons for most of the manufatcurers as they are a part of the hull. for some others is from the end point of the bows to the end point of the hull stern.

Education makes a lot of difference by the way
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Old 22 October 2004, 17:12   #16
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Sorry, reading back it seems that everybody is making pretty much the same points!!

Dont think my heads working properly tonight (like it ever does!) but whatever the case, its up to the individual owner or maker at the end of the day as to how they classify the length of their boat right?

Regardless, its a great idea and a top project so good luck to all involved! Hope you enjoy it very much and are able to draw loads of valid conclusions from it which will benefit many others in the future!

Good effort and keep us posted!
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Old 22 October 2004, 17:15   #17
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MadMat I am not arguing about what the term LOA is.

What I am saying is that for RIBs different standards apply as to the meaning of the term LOA.

As many recognise as the OVERALL LENGTH of the boat the total length foward to the end of the tubes or swimming platform whichever the greater rather (which is the correct IMHO) to the end of the hull. And when one says I want a 750 RIB I always have in my mind a hull loa of 6.8-7mtrs rather than anything more.
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Old 22 October 2004, 17:42   #18
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Quote:
Originally Posted by Manos
When you say I want a 7 mtr RIB you mean a 7mtr total length (OVERALL) not hull length.
So tell me again what I am so wrong about?

No one is doubting that there are several ways to measure a boat. Only one of these is the length overall (LOA, shown in green below), which goes from the furthest projection forward, to the furthest projection aft. That's from the very front of the boat, to the very back, including (in a RIB) the tubes and the drives. In a sailing boat it includes the pulpit, bowsprit and anything else that is permanently part of the boat. LOA is the biggest possible length measurement for a boat. Any other measurement is not the LOA, it's something different.

Depending on the design of the boat, the LOA may be more or less the same as the hull length (or more technically the LBP that quinquarimarine referred to, which for a RIB would generally be from the transom to the point where the front of the hull meets the tubes, shown in yellow below). Take a rowing boat for example; it's just a hull so the LOA is the same as the hull length. A cruiser with a swim platform and one of those sticking out anchor beaks will have a LOA rather greater than the hull length. A RIB with tubes sticking out at both ends also has a longer LOA then the hull length. But you agree with that -- it's what I quoted above.

Then there's the waterline length LWL (shown in blue below) which may be the same as the hull length and the LOA (consider a dutch barge for example). A RIB has a raked bow so the LWL is less than the hull length which in turn is less than the LOA.

How the RYA or BIBOA choose to measure RIBs for race classification is not relevant to this debate. If their chosen measurement is less than the LOA, then it doesn't make it a different sort of LOA!

Generally speaking RIB model designations are based on LOA with a degree of artistic licence to make the boat sound a bit bigger than it really is. It would be interesting to compile a list of measurements of LOA, hull length and LWL for different RIBs -- anyone got a tape measure handy?

John
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Old 22 October 2004, 17:51   #19
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Yeh, but you don't want to let let any of that get in the way of a good argument!
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Old 22 October 2004, 17:52   #20
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Quote:
Originally Posted by John Kennett
So tell me again what I am so wrong about?
On a RIB is the norm when you say that you want a 750 mtr RIB to actually get most of the time a 6.5-7ish LOA RIB. If you say you want an 8mtr RIB you will get again most of the time a 7.5ish mtr RIB and so on.

Quote:
Originally Posted by John Kennett
How the RYA or BIBOA choose to measure RIBs for race classification is not relevant to this debate.
Agree, but I was making the point that when they say a min LOA 6.5 mtr RIB can enter F2 class the mean mean the boats hull LOA and not the total length with the tubes and IMHO should had been the other way round - TRYING TO GET IN THERE VERY HARD

Quote:
Originally Posted by John Kennett
It would be interesting to compile a list of measurements of LOA, hull length and LWL for different RIBs
I was about to suggest that. It will be an interesting survey I believe
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