Boat measurements

jwalker · 22 October 2004, 16:37

< Edit: Split from the RIBnet project boat thread JK >

JK, look at the actual hull length when choosing the boat. It varies considerably between manufacturers for a given boat length. It can be close to metre variation in the 7 - 8.5mt range.

John Kennett · 22 October 2004, 18:14

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

Matt · 22 October 2004, 18:23

Even my hardboat sold as 29'2 is actually 30'11

Manos · 22 October 2004, 18:28

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 6.5-7.0 metres. Do you know of any that are markedly different? John

John everyone knows that the RIB manufacturers measure the boats from bow to the end of the pontoons and not the hull LOA.
So yes is is different.
If you want a 750 RIB the hull LOA may be between 6.20-6.60. If you want a hull LOA of 750 then you are talking for a RIB total LOA (inc tubes) between 8-830 mtrs.
Now there are some manufacturers (very few) that measure the actual hull LOA. So you need to check.

John Kennett · 22 October 2004, 18:49

Manos, there's no such measurement as "hull LOA". LOA means "length over all" which is the total length. Not the hull length.

Like I said, for a boat (and we're talking about RIBs here) 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. The waterline length would be a bit less still . . .

John

Manos · 22 October 2004, 18:53

John YOU ARE VERY WRONG my friend

Shall I mentione the names BIBOA and RYA? Check with their rules and you will see. Also every book on RIBs and boats you look mentions this. I'm sorry but you are wrong

John Kennett · 22 October 2004, 18:54

I am always ready to learn from an expert. Perhaps you'd like to explain exactly where I'm going wrong?

John

Manos · 22 October 2004, 18:58

Check above. Just added a bit in about BIBOA and RYA rules.

LOA means Length Over All i.e. from bow to the end of the boat wherever that is. HOWEVER, there are two ways of doing it on RIBs, hull LOA and Boat LOA. So there you go. Examples, 8.5 mtr Scorpion Hull LOA 8mtrs (I think), 7mtr Falcon Hull LOA 6.10 mtrs. 640 mtrs Falcon Hull LOA 580 or as above can't remember etc etc

....and I'm NOT and expert (others are though), but I have a few Degrees including a Masters

Seb · 22 October 2004, 20:03

LOA is the LENGTH OVERALL. OK, the 'rigid hull length' is less as rightly said but a boat model marketed with a measurement, i.e. Avon SR8.4, Halmatic Pacific 22, Ribcraft 585 etc etc etc is a reference to the LOA right?!

So, being educated or not is irrelevant. A RIB is measured as any other boat, from bow to stern. LOA again.

The actual hull measurement however is a simple figure that may be calculated if required. Its not, IMHO a 'standard' and recognised industry dimension. Its simply not needed.

Check some boat specs, do any of them state hull length or beam? Nope!

Just my views

Manos · 22 October 2004, 20:26

Quote:

Originally Posted by Seb

A RIB is measured as any other boat, from bow to stern. LOA again.

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

quinquarimarine · 22 October 2004, 20:32

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
www.quinquari.co.uk

Manos · 22 October 2004, 20:54

Pete7 · 22 October 2004, 20:57

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

Matt · 22 October 2004, 21:05

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

Matt · 22 October 2004, 21:07

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

Seb · 22 October 2004, 21:12

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!

Manos · 22 October 2004, 21:15

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.

John Kennett · 22 October 2004, 21:42

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

Matt · 22 October 2004, 21:51

Yeh, but you don't want to let let any of that get in the way of a good argument!

Manos · 22 October 2004, 21:52

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