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Old 09 May 2014, 10:25   #1
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RIB Hulls Classification

Hi everyone!

I'm new into boating, but I've enjoyed so far.

I bought last year a small inflatable (3.3m) with a view of going out on the sea. I realized that is not quite suitable for that, especially when the sea is anything above slight state.

I'm now thinking to buy a RIB, but I want to do a bit more research before buying it.

Now there is the question.

Is there a classification system for different hull types? So far I could only see shallow V or deep V, but that's very vague. I'm sure there is more than that. Could anyone, please help? Also is there a table showing the correlation between boat length, hull shape and sea state that the boat can safely handle?

Cheers!
Nick
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Old 09 May 2014, 11:18   #2
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- What your going to be using it for?
- How many people are you are carrying?
- What's your Budget?
- Are you intending to buy it new or second hand?


Should be able to nail it down to what sort of boat would suit you with those questions.

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Old 09 May 2014, 11:54   #3
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Hi and welcome

Boat size is not necessarily representative of its handling and sea keeping characteristics. As you have already established, hull design plays a big part, and there is plenty of info on the forum about big RIB's handling terribly and little ones handling well.

To answer your question: Yes, there is a EU Recreational Craft Directive that categorizes boats based on their ability in various sea states. However, there are varied opinions of its effectiveness, as two boats from the same category can have completely different abilities. Each boat that is certified to conform to the RCD will have a plate with manufacturers details, max load, engine rating and category stamped on it.

Use the forum search facility for this as well, as there is plenty of information to help you. Here is an example...

Categories B, C etc - what does that mean ?

Enjoy and happy searching
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Old 09 May 2014, 13:26   #4
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Welcome. I was in your shoes last year. I started with a Sib then got an Avon SR4 which has deeper V than most boats that size. It cut through anything and I took it out in horrible weather. It was an amazing little boat. Then I got a Zodiac Hurricane 533 which has a "w" shaped hull that slapped hard like a Sib. I think I cracked a few backbones on that one.

Just go take a ride on different ribs and pay attention to the hull shape and how they ride.
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Old 09 May 2014, 14:25   #5
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Thank you all for your replies.

@henryfreston
- fishing.
- 2-3 people.
Questions 3 & 4 are not relevant to this as I'm trying to find the right boat and then I'll see how to pay for it.

@Exe treme
EU RCD is too a wide classification. My little boat is cat. C same as a Warrior 17', but the difference is huge.

I'm after something more precise. For instance with the sea there is the beaufort scale. Looking at that I can very accurately compare the sea state in two different days.

The same thing I'm looking to find out about hull shapes. Something that is factual, numbers that you can compare.

This takes me to the tworotorturbo's reply. It's a way to test different hulls and find out the best. However that's very difficult to achieve (unless you've got lots of money you can't line up 10 RIBs and test them in exactly same sea conditions and even if you do that, you're feeling are not always the same) and not too factual. You mentioned about SR4 that has deeper V than other boats. That's not quantifiable. How deeper? 10% more, 20% more etc.

I'm still searching.

Thanks all again.
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Old 09 May 2014, 15:14   #6
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Quote:
Originally Posted by naexparvu View Post
Thank you all for your replies.

@henryfreston
- fishing.
- 2-3 people.
Questions 3 & 4 are not relevant to this as I'm trying to find the right boat and then I'll see how to pay for it.

@Exe treme
EU RCD is too a wide classification. My little boat is cat. C same as a Warrior 17', but the difference is huge.

I'm after something more precise. For instance with the sea there is the beaufort scale. Looking at that I can very accurately compare the sea state in two different days.

The same thing I'm looking to find out about hull shapes. Something that is factual, numbers that you can compare.

This takes me to the tworotorturbo's reply. It's a way to test different hulls and find out the best. However that's very difficult to achieve (unless you've got lots of money you can't line up 10 RIBs and test them in exactly same sea conditions and even if you do that, you're feeling are not always the same) and not too factual. You mentioned about SR4 that has deeper V than other boats. That's not quantifiable. How deeper? 10% more, 20% more etc.

I'm still searching.

Thanks all again.
If I'm honest I wouldn't worry how specifically deep it is (I.e. 10, 20, 30% deeper than another rib).

Some Ribs perform better than others in different condition.

I would just think about which rib is going to suit your needs better.

Personally I would think if you are looking to fish 2-3 and want rough water handling capability then a searider 5.4 would be ideal- there's one for sale on ebay with a nice 2009 optimax 90hp now

They have a very deep hull and are renowned for having excellent sea keeping ability. It should have enough room to comfortable fish 3, if you look at benjtaylor's profile you will see some of his seating arrangements in SR5.4s and he seats 3-4 comfortably.

Henry
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Old 09 May 2014, 15:15   #7
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Quote:
Originally Posted by naexparvu View Post
Thank you all for your replies.

I'm after something more precise. For instance with the sea there is the beaufort scale. Looking at that I can very accurately compare the sea state in two different days.

The same thing I'm looking to find out about hull shapes. Something that is factual.

I'm still searching.

Thanks all again.
Ah. That's a different question. In short, no there isn't anything. Try this for starters and search for similar...

http://www.motorboatsmonthly.co.uk/n...rib-group-test
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Old 10 May 2014, 08:26   #8
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SR5.4 is too big. My garage is only 5m long, so it's got to be below 5m.

What about Ribcraft? It looks that they are pretty good and they have a 4.8m model.
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Old 10 May 2014, 08:38   #9
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Ribcraft 4.8 is a good call.

I'd have a search regarding putting ribs in garages - a 4.8m rib on its trailer will be considerably longer - need to factor in engine and trailer drawbar.

However, there are some good solutions forum members have come up with.
Boat diagonally across garage.
Removeable / folding drawbars etc.
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Old 10 May 2014, 08:53   #10
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Hi Nick

As per above, if you're looking for a seaworthy rib Ribcrafts are generally thought to fulfil this requirement pretty well.

But on a more general note when looking at hull forms find below some thoughts:

For being able to keep going quickly into a chop or head sea:
Narrow waterline (or chine) beam
Deeper V (higher deadrise angle is the tech term)
Longer is better

Seariders typically have narrow hulls and a deep V. Good for sea keeping but very little space on board for seating.
Ribcrafts being a newer design are a little better in this respect.

The Scorpion hull, for example, was designed specifically to deal with the Solent "chop" - short waves often 1m or so high. Has very narrow beam, extremely deep V, especially forward, and mine, although not all have the tubes well clear of the water at rest. Great for going upwind but:
High tubes and narrow beam make it very tippy at rest.
Extreme deep V at bow can cause bow steer or hooking when travelling down sea.

Other disadvantage of deep V is that it needs more power for the same speed.

It's all a compromise and can't really be assessed numerically.

Most sub 5m ribs will have a wide beam for their size and a relatively shallow V to allow good performance (speed) with the family on board and modest power.

Ribcraft 4.8 goes best with 60hp plus.
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