Safe Boat Size and Wave Height

sea_ledford

Not bad, but it would suck at speed in strong windchop with all that weight in the back from the outboards.

What it really wants to be is one of these:

Tech Specs

Ex-Navy Seal boat I would be happy to drive in 20ft seas. Well maybe not happy, but I know she could do it.

also some video at Movie Gallery
"North Shore.m4v" has some shots of the boat, but the boat jumping tend to scare off some of the clients!

Back to the OP, there are a lot of variables to consider, and I don't think that boat length vs wave height is one of them I would think about. I have captained boats the same length as the NSE boat, the Pailolo, that have given me a sphincter factor of 9 or 10, in conditions that the Pailolo could run through with one hand on the wheel. Hull design, and weight distribution are probably more important than anything other than a competent captain.

Chris

divingtoors

Hi There

I think it is not just about the size of the boat, although that matters quite a lot. When going to sea...bigger is better.
My boat is a 5m (16Ft) Gemini RIB, and most of the charter operators here in Cape Town, South Africa use between 6.5m and 9m RIB's (21.5 ft - 30 ft).
Sea state 4 is the most I reckon a diver will handle in boats such as these before sea sickness becomes a factor, due to increased roll and pitch of the boats.

There is also a safety / danger factor, as usually with sea state 4 conditions thre is marked surface chop, meaning seperation from the boat and the possibility that the divers wont be seen by the skipper is a real threat.

It is also extremely uncomfortable and sometimes difficult to get up the boat if there is a lot os roll or pitch.

The US NAVY SeAL's or any other nations special forces don't have much of a choice as to the weather they want to operate in, and usually the worse, the better.

Sport divers can most often make that choice, and should excerise it.
We have been in conditions, far from safe landing, that turned ugly within hours of launching, where waves were breaking over the bow of my RIB (5m - 16Ft) for at least 45min, while we navigated the storm back to a safe harbour site.
Although my RIB and most RIB's are designed for conditions like that in mind, it is not fun sitting almost knee deep in water, with every second wave crashing over the crew. The nominated skipper (as we take turns in driving the craft, and all the crew mates are qualified and experienced skippers) had to don a diving mask and snorkel , to afford him the opportunity to actually see ahead some in the howling wind and sea spray conditions. In the pub afterwards, while we waited for our beating heart rates to subside, and the knotted nerves to come undone (asisted off course with a strong local brew) we realised the folly in our way, and how easily things could have gone really bad.
Lose a motor due to mechanical failure in conditions like those, and chances are that you may not make land in any semblence of a water going craft...

There is no point in being at sea in anything more than sea sate 3, with 4 being the maximum.

But, you milleage may vary..

Regards

kwinter

Eric -

Wouldn't you rather have one of these?

Johnny Christensen

This is my preference of transportation when the weather turns bad.

Why bounce arround in a open boat and be beaten half to death, when you can sit in comfort and watching the others being seasick ?

23,3m long (about 75-80 ft) and 5,8m wide (19 ft)
Why would you have it any other way??
Are extra points being awarded for starting the dive in a compromised state?

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silent running

Hi John, excellent question. I hope somebody more knowledgeable than me
comes along to give you a more precise answer, but here's my 2cs:

Liveaboard-bigger is better, as long as it's not an ex oil rig tender with an extra story added and 2 of the 4 engines removed. This describes many franchise boats, which as oil rig tenders, were originally built for speed, not stability and with an added story for more crew and less weight in the hull, become very pitchy and too much motion for normal people in anything over 4ft seas. I had an lb Capt in the TCI turn around one of these x oil rig tenders in 3-4ft liveaboard in seas because he said it was "too rough".

A full displacement hull is better for a liveaboard, a full displacement 80 ft+ boat with gyroscopic stabilizers is best and will get you through anything up to 20ft seas. I have slept through an on beam crossing in 12 ft seas in such a boat. In general, look for more feeboard, a deeper hull a wide beam and not to tall a super structure. A mid point entry/stairs will give the most comfort in bigger seas as there is less motion at the mid point of the boat. I have exited the water onto such a ladder/stairs in 6ft seas without any problem.

Day boats- main thing is a flexible body, like an RIB that will absorb more abuse before transfering it to the passengers. And don't forget the ladders, make sure they have a good one that extends into the water by a few feet. I'd take an RIB over 12ft in seas up to 10ft, but I'm not the most cautious passenger... -Andy

silent running

I tried to edit the above post as I wrote it on the fly. I meant to say that while I would ride in a 12ft RIB in 10ft seas, and have, I don't like to dive off one in seas bigger than 6 feet. I would also add that proper stowing of your CCR on the bottom of the boat towards the rear is crucial to avoiding damage in rough seas as that's where there is the least motion. I leave my unit on it's back and when it's time, sit it upright on the floor, then sit down to don it, very easy to do, even in big swells. Putting your CCR in the bow of any small craft, if there's any chance of seas over 3 ft, is asking for breakage...

What happened to the edit button? -Andy

jkaterenchuk

Andy

Thanks for the reply and clarification. I think the edit button disappears after one hour and then you cannot edit any longer.

John

O.C.Diver

mempilot

Flat as a lake is a 'might go' for Padipro. Now, flat as a pancake, and he is 'all in'!

Padipro (Scott), are all these videos making you queasy? Come on bro, you know they are! :D

silent running

Hello Ted, while agree with you in general, I was speaking from having been on trips to far away places where I only had limited time to get dives in. I don't like doing dives in 6+ft swells, but it is manageable with a boat(s) that are set up for it. I have done some great dives in weather that was less than optimal, or where the weather turned sour while underwater. And I really hate the idea of dragging all my gear to the other side of the world only to have a Capt say that we can't make a crossing to the best sites in his luxurious but barely seaworthy, floating hotel, because of 6ft seas.

That being said, you wouldn't catch me trying to get back on board a boat that had one of those hinged stern ladders in anything bigger than 3 ft. I like having all my fingers in good working order. When you get right down to it, it's often the type of ladder and where they are placed that is the limiting factor in how big a sea you can safely dive in. I wish more boats had a mid or just aft mid entry point. And when will somebody make a proper ladder for a RIB? It seems to me all you would need to do is attach the boat end of the ladder to a wide, curved foot that would conform to the curve of the pontoon and distribute the weight of the ladder/diver over a greater area of pontoon, which would hopefully make it stable enough to climb on/over.

I guess a moon pool is the best possible design to shelter divers from swells, short of a lift. But I have never dived from a boat that had a moon pool, sounds nice though... -Andy