Why do divers use RIBs ? [Archive] - BSAC Scuba Diving Forums

pegcjs

10-02-2010, 10:35

My club is thinking of buying a small boat (we currently have a 30ft hard boat but its a bit useless anywhere except the area where we moor it). Many BSAC clubs use RIBs which are pretty expensive for their size so we are wondering why ? - Fibregalss DORY style boats of comparable lengths offer more deck space and greater stability in heavy seas but only cost ~ £4-5k including engines as compared to ~£20k for RIBs . In other words we could buy 4 of these for the price of one RIB.

Here's the kind of thing we're looking at:

http://dept106.eng.ox.ac.uk/oxfordbsac/media/images/fearless/boat.jpg

People have suggested that the inherent buoyancy of a RIB is necessary for use in heavy seas but what makes sense for the RNLI is not quite the same as for us divers who wouldn't leave harbor in the kind of seas that they have to traverse.

These boats have a built in floor making them buoyant even when swamped and are low enough to enter from the water as usual although we plan to get a ladder to make things easier.

Can anyone enlighten me as to why the RIB is the diver boat of choice and what it is that might make small hardboats less attractive ?

- PEGCJS

northern_diver

10-02-2010, 11:31

20K is new, get a good quality second hand RHIB (or two be better) for less than 10k, i was offered a 5meter RHIB+trailer etc inc. engine for 2.5-3k (cant remember, was last year and i was kitting up), so shop around.

I'm not au fait with maintain etc, so cant comment there.

John

Woz

10-02-2010, 11:45

Cos normal boats are wobbly at rest. A RIB has massive tubes on it which makes it very stable when sat in the water with a load of divers on the side of it.

Plus you can't sink them even if you try really really hard.

ChristianG

10-02-2010, 13:17

Cos normal boats are wobbly at rest. A RIB has massive tubes on it which makes it very stable when sat in the water with a load of divers on the side of it.
Quite so.

The other advantage is that if you drop your tank on a RHIB (as distinct from a RIB) the damage will be negligible, if any. Not so on a fibreglass thingy.

I dived for years on a fairly serious fibreglass thingy, a trihull (therefore very stable) with twin 90 hp Honda four strokes. The difference was that this was a private boat, very well set up for divers, which means that anyone who abused it didn't get invited again and we all knew it. It was towed by a Merc V8 AWD.

Club boats, as well as commercial boats, don't have the same "exacting" rules. As well, have you thought about towing this thing as against what I think would be a much lighter RHIB?

Having said that, my Club has a hardboat, designed and built for diving. It also sits in the water except when we want to clean it up or take it on a weekend away. Both are a major exercises and the towing vehicle needs to be sufficiently powerful, preferably AWD.

This boat also happens to be 100% aluminium and built like the proverbial Oz outside dunny. I know, I was one of the few people (three) that was involved in its build and we actually got it almost 100% right, no mean feat that. This boat is 23 ft and "pure luxury", cue the Monty Python gang.

Edit/: The Club's previous boat was also aluminium, an 18 ft centre console runabout that we stored on land when not in use. Wobbly is the word and although we got used to it the cox, often myself so I guess I should know, made corrections to trim "George, please change places with Fred" for weighting purposes.

Woz

10-02-2010, 14:48

Oh and you can take a RIB out in horrendous weather and get back. Do the same in a hardboat like Christian's play boat and you'll have a cry.

bootneck

10-02-2010, 15:13

I been asking myself about RHIB and Hard boats for some time, I have an old 5.5 rhib and the tubes are shot and with wear and tear its getting past it, so after much humming and ahing I purchased a 18 foot dory type boat with front cabin.

It had a large deck area, some where for the cox,n to shelter or check charts a small stove and dry deck and cabin storage , even enough room to kip in the cabin. I now looking at making a dive ladder for it, which as far as I could see was its only down side for the type of fare weather diving I do.

Once its set up I will look at doing an evaluation on how it compares to my little rihib as a day dive boat.

ChristianG

10-02-2010, 16:07

Oh and you can take a RIB out in horrendous weather and get back. Do the same in a hardboat like Christian's play boat and you'll have a cry.
Them's fighting words ;). That TUG allie boat has been out in the worst of conditions. Well, actually has returned in the worst of conditions. That Trihull fibreglass boat used to skate past TUG II at every opportunity, and was simply brilliant in the water, but then its skipper wanted to do that, even though he's a life member of TUG.

He, an Italian friend of mine called Carlo, he's going to be 80 this next Christmas Day and is still happily diving away to depths that might make some grown men weep - on air, and I were responsible for the building of TUG II and she's still going strong as ever.

I'm not saying that you guys should all-of-a-sudden give up on your RHIBs, in fact I didn't say that in my first post, it's just that there are other alternatives in other conditions and ours eminently suit us.

Woz

10-02-2010, 16:12

Them's fighting words ;). That TUG allie boat has been out in the worst of conditions. Well, actually has returned in the worst of conditions. That Trihull fibreglass boat used to skate past TUG II at every opportunity, and was simply brilliant in the water, but then its skipper wanted to do that, even though he's a life member of TUG.

He, an Italian friend of mine called Carlo, he's going to be 80 this next Christmas Day and is still happily diving away to depths that might make some grown men weep - on air, and I were responsible for the building of TUG II and she's still going strong as ever.

I'm not saying that you guys should all-of-a-sudden give up on your RHIBs, in fact I didn't say that in my first post, it's just that there are other alternatives in other conditions and ours eminently suit us.The worst of conditions where you are with your play diving would barely raise a ripple round here with our hairy chested man-diving.

Deep air's a piece of cake in calm, warm water in 30m viz. Try doing it in 3.5 degree water in 2" viz. I did. Last weekend.

ChristianG

10-02-2010, 16:22

The worst of conditions where you are with your play diving would barely raise a ripple round here with our hairy chested man-diving.

Deep air's a piece of cake in calm, warm water in 30m viz. Try doing it in 3.5 degree water in 2" viz. I did. Last weekend.
You're trying to provoke me? I don't provoke.

30m viz is what we sometimes get, albeit rarely. I've been in a thermocline where, from the waist up I am in the clearest of water but, looking down I can't see my fins. Yet I know that I have a lot of metres to go to actually reach the dive site.

It's all relative.

northern_diver

10-02-2010, 16:38

You're trying to provoke me? I don't provoke.

HAHAHA oh yes you do:rolleyes: ;)

30m viz is what we sometimes get, albeit rarely. I've been in a thermocline where, from the waist up I am in the clearest of water but, looking down I can't see my fins. Yet I know that I have a lot of metres to go to actually reach the dive site.

Yep, not always the best of conditions in the UK either. Had Haloclines on the BREDA at Oban where you cant see your gauges...but its normally only a couple of meters.

It's all relative.

Thats very true, horses for coures.

I was unaware of a difference between RHIB and RIB:confused: Between a RIB/RHIB and a zodiac/gemini/other squishy sure but my understanding(which maybe at fault) is that RIB/RHIB's are the same, Ridged Hull Inflatable Boat.

Please correct if i'm wrong.

Sounds like a nice warm climate boat to be honest, would be interesting to see it in action against a RHIB/RIB in a full variety of conditions...I'll volunteer to be on the RIB/RHIB:) (i like rubber:eek: :rolleyes: :p )

John

ChristianG

10-02-2010, 16:51

I was unaware of a difference between RHIB and RIB:confused: Between a RIB/RHIB and a zodiac/gemini/other squishy sure but my understanding(which maybe at fault) is that RIB/RHIB's are the same, Ridged Hull Inflatable Boat.

Please correct if i'm wrong.
Actually you answered your own question.

A RHIB is a rigid Hulled boat, whereas a RIB - is not.

Gosh, even I know that and I live where there are not many of those at all, although I've been in a RIB and it's decidedly uncomfortable in anything like chop.

Woz

10-02-2010, 16:55

Anyone else want to have a pop? My fingers are getting tired.

northern_diver

10-02-2010, 17:10

Actually you answered your own question.

A RHIB is a rigid Hulled boat, whereas a RIB - is not.

Gosh, even I know that and I live where there are not many of those at all, although I've been in a RIB and it's decidedly uncomfortable in anything like chop.

Ocean Diver WorkBook pg 82-83 current edition-

RIBs(Rigid-Hulled Inflatable Boats)

Constructed with ridged hulls surmounted by air filled tubes to support the hull in water, RIBs are manufacted in various sizes and can generally carry from 6 to 12 divers.

Common characteristics are that:
-Hightly maneuverable
-They are almost unsinkable diving plateforms (commonly used as in-shore lifeboats)
-Entry and Exit is ussually over tubes
-They are open boats and are therefore exposed to the elements
-They ususally have cylinder racks...

Wiki-confirms.

RIB magazine (i dont subscribe, just a google search) does as well.

Gosh, i thought there wasnt a difference, in other than that some people include the full title and some a shorted, but still accurate version.

Can't find it, but havent looked too hard, but i think what your thinking of is more a soft hull/bottom boat, such as the gemini/zodiak et al

John

ChristianG

10-02-2010, 17:20

Anyone else want to have a pop? My fingers are getting tired.
Are you trying to tell me something Woz?

Am I, perhaps "Persona Non Grata" simply because I was passionate about a certain subject?

Perhaps I'm being paranoid, but perhaps not, who knows what is going on behind the "Closed Door" of the Forum devoted to members only where, presumably, that subject is now being discussed.

Anyone want to comment? Preferably on a separate, appropriately described thread?

I have this distinct feeling that I'm not wanted and, if so, I'm happy to leave but I want it out in the open, rather than snide comments.

I hope that makes some sort of sense, not much, but at least some.

Woz

10-02-2010, 17:21

Are you trying to tell me something Woz?

Am I, perhaps "Persona Non Grata" simply because I was passionate about a certain subject?

Perhaps I'm being paranoid, but perhaps not, who knows what is going on behind the "Closed Door" of the Forum devoted to members only where, presumably, that subject is now being discussed.

Anyone want to comment? Preferably on a separate, appropriately described thread?

I have this distinct feeling that I'm not wanted and, if so, I'm happy to leave but I want it out in the open, rather than snide comments.

I hope that makes some sort of sense, not much, but at least some.Fzzzzzzzzzzzzzzzt he casts a provoking hook and gets a paranoid bite. Result!

ChristianG

10-02-2010, 17:31

Ocean Diver WorkBook pg 82-83 current edition-

Can't find it, but havent looked too hard, but i think what your thinking of is more a soft hull/bottom boat, such as the gemini/zodiak et al
You still don't get it.

I don't know about the "gemini/zodiak et al", no idea, but if they don't have a rigid hull, why, they're RIBs, rather than RHIBs, I just can't see the problem in differentiation.

Nigel Hewitt

10-02-2010, 18:01

You still don't get it.
We know, we know...

Come on Christian. You're an opinionated old pedant who loves to argue.
Takes one to know one. :p

bythesea

10-02-2010, 19:46

They are easy to tow, stable, reasonably cheap to run, for a boat, easy to maintain, can blat along at a rate of knots to get you there for slack and back for beer, they are cool, unsinkable, orange, easy to roll off, easy to get back on, can be picked up at good prices, engines can be swapped easily...

Did I miss anything out?

Oh yeah..there is no H, unless you are really precious or american, don't believe me, go to a RIB forum and ask, see how long you survive ;)

Here's one http://rib.net/forum/

northern_diver

10-02-2010, 20:05

Maria CM

10-02-2010, 23:23

Perhaps I'm being paranoid, but perhaps not, who knows what is going on behind the "Closed Door" of the Forum devoted to members only where, presumably, that subject is now being discussed.

I joined BSAC in the main so I could see the members forums:o I'm paranoid too:eek:

best wishes,

Maria

Maria CM

10-02-2010, 23:24

We know, we know...

Come on Christian. You're an opinionated old pedant who loves to argue.
Takes one to know one. :p

I think Nigel might have got you there Christian:p ;) :D

best wishes,

Maria

Hickdive

11-02-2010, 08:22

Years ago I found that, in conditions we in the UK would consider perfectly acceptable for diving, dories slammed terribly and had to be driven at lower, less efficient speeds for comfort and safety. We used to cross to Rathlin in NUU Rescue in company with Portstewart BSAC's RIB and would invariably be left for dead in anything other than a glassy calm despite having a significant HP advantage.

Unless hull design on dories has been improved radically in the last twenty years I can't see there being any change in that. Dories are great for the tropics where it is either a hurricane or completely calm but not ideal for for round the UK where we often transit rougher water to find sheltered sites.

People typically see deck space on dories as being superior to RIBS but that's mainly because of the fashion in dive RIBS to fill the deck with nonsense like huge jockey seats, cylinder racks and fuel tanks instead of laying cylinders flat and having fuel tanks built into or stowed under a single cox'n seat.

davebarber

11-02-2010, 08:59

I can't see any cost advantage in a Dory.

Most of the money in an outfit goes into the engine/trailer/instruments/fitting out.

The actual hull is only 25% of the total cost.

Dave Lee

11-02-2010, 09:49

People typically see deck space on dories as being superior to RIBS but that's mainly because of the fashion in dive RIBS to fill the deck with nonsense like huge jockey seats, cylinder racks and fuel tanks instead of laying cylinders flat and having fuel tanks built into or stowed under a single cox'n seat.

Agree on the jockey seats & fuel, but in my experience bottle racks are much, much better than having kit on the deck (unless it's tied down) where it can shift around in a big sea. I've had situations where a big wave has caused the kit to slide to the back of the boat & completely bugger the boats trim making it much harder going in said big sea. Fortunately no ones been hurt in these incidents, although they have precipitated some multi coloured yawns!:rolleyes: . The bottle rack if possible should be mounted toward the bow of the boat so the bottle/kit weight offsets the engine & trims the boat better.

My tuppence worth.

Hickdive

11-02-2010, 10:23

Agree on the jockey seats & fuel, but in my experience bottle racks are much, much better than having kit on the deck (unless it's tied down) where it can shift around in a big sea. I've had situations where a big wave has caused the kit to slide to the back of the boat & completely bugger the boats trim making it much harder going in said big sea. Fortunately no ones been hurt in these incidents, although they have precipitated some multi coloured yawns!:rolleyes: . The bottle rack if possible should be mounted toward the bow of the boat so the bottle/kit weight offsets the engine & trims the boat better.

My tuppence worth.

If the bottles are already at the back they can't go any further. You can also make use of the boat's 'self-propelled ballast' to trim it ;) .

Dave Lee

11-02-2010, 11:24

If the bottles are already at the back they can't go any further. You can also make use of the boat's 'self-propelled ballast' to trim it ;) .

True, but you've also probably got an unbalanced boat & are burning alot more fuel than you need to. On our 6m Humber we've found tying off to the rack & stowing as much kit forward works by far the best for us.

Hickdive

11-02-2010, 12:35

True, but you've also probably got an unbalanced boat & are burning alot more fuel than you need to. On our 6m Humber we've found tying off to the rack & stowing as much kit forward works by far the best for us.

Hmm, the self-propelled ballast weighs an awful lot more than its kit, has a greater effect on trim and is easier to shift around, even under way, to achieve a perfectly balanced boat. It also means that, without a rack, you can readily accomodate eight divers in a 5.2m Humber Attaque.

But, each to their own, racks at least make for a convenient hand hold.

ChristianG

11-02-2010, 12:56

Hmm, the self-propelled ballast weighs an awful lot more than its kit, has a greater effect on trim and is easier to shift around, even under way, to achieve a perfectly balanced boat. It also means that, without a rack, you can readily accomodate eight divers in a 5.2m Humber Attaque.
On our previous 18ft tinny, what you guys tend to call a dorie, we always had as much of our gear stored forwards as possible, at least the tanks and w/belts. Cameras did tend to find a place well away from all that heavy stuff that had a tendency to slide, and bounce, around.

We actually had a slatted plastic box, IIRC a milk crate, for the weight belts and that was permanently secured way forward.

Ralph

14-02-2010, 22:58

RIB's (no H unless you really want to) are excellent sea boats for a couple of reasons, the main ones being that if you stick big round tubes that weigh naff all on the sides, the centre of gravity is kept a lot lower which is better in practically every situation.

Now that you've got the tubes on it, you can get away with a narrower hull which allows you to have a deep vee hull form which will again contribute to making it better manoeuvring at speed in a seaway.

The tubes provide shock absorption from the water underneath and also to the bums on top and when you stop, they should give a higher waterline beam when the tube sits in the water (as long as it's been designed right). If you manage to stuff the whole thing into a wave, you've got not only an enormous reserve of buoyancy but a rather large lifting surface to assist in pulling the whole lot back out again.

In short, they tend to be better boats for the conditions around the UK coast where the waves tend to be shorter and steeper. If you raced a RIB and a dory in something like the Solent chop, the RIB would win by miles and the dory driver would need all their fillings replaced.

littlerattle

27-05-2010, 13:05

did anyone see the dive dory at swanage recently?

pegcjs

28-05-2010, 16:52

Yes - I did. Dived off it too. It was one of these:

http://www.solentfisher.co.uk/DSCF0116ano.jpg

Timw

28-05-2010, 22:27

True, but you've also probably got an unbalanced boat & are burning alot more fuel than you need to. On our 6m Humber we've found tying off to the rack & stowing as much kit forward works by far the best for us.
That depends how the boat was built.
My Ribcraft 585 was specced for diving and has the console forward and a 90L fuel tank built in under it. The bottle rack is behind the jockey seat - over the centre of the boat so it is still nicely balanced when loaded up - even with a few stages on the floor when the rack is full.

Starnetman2001

03-06-2010, 22:26

Just thought I'd join the debate :)

I have just put a small cabin on my 6.5 RIB and its worked a treat! I wanted a shelter where the kidz could get out of the weather as well as still using as a dive rib.

No bottle rack for me. You can always wedge so they won't move and it simply issn't a problem for me. Had 10 twin set's and didn't budge.

The reason why I wanted to keep the RIB and not go for a cabin boat is very simple. You hear of loads of day boats including dorys, fishing boats and many others being lost at sea. Granted, it's often by inexperienced handlers but I have never heard of a RIB sinking.

Next project is to build my own 7.5 with full size cabin ;)