SIB in heavy seas - ~4ft waves - how to navigate safely with speed ??

zurk · 06 June 2013, 20:05

i have a 10.5ft soft inflatable with alum floor and 15HP. goes ~30kph with two on board + fuel + gear. caught in relatively bad seas (4ft waves). waves were 45-65 degree angles with 2-3 ft spacing in deep water (21 miles offshore by GPS). it planes well in 2 ft waves but with 4 ft it was hitting the water pretty hard so i went at 1/4 throttle and 8kph. took nearly 2 hours to return.
any idea on how i can go faster in heavy seas with a SIB ?? is there something i can add (maybe a foam block or inflatable triangular block at the back) to convert the planing hull shape of the SIB to a displacement hull so it rides faster in heavy seas ??

captnjack · 06 June 2013, 20:12

To go faster you have to add a couple of meters to your length! Or go downwind.

Displacement speed on a 10.5ft boat is about 4 knots. So about the same speed you were travelling.

Not sure where you were, but the whole excursion sounds incredibly iffy (and lucky). 21miles offshore in a 10.5ft SIB?!?

willk · 06 June 2013, 20:17

My SIB is 9ft. long. It's a category below yours and I take it all sorts of places and get raised eyebrows. However, I'm inclined to agree with most of what captnjack says. You need a bigger boat..., you're waaaay outside the envelope!

Simply put, a 4 foot wave (which is commonplace everywhere) has reduced you to crawling for two hours. In two hours, things can get a lot worse. There's a limit to what a 10ft SIB can handle.

bingosucks · 06 June 2013, 20:41

i would agree a bigger boat is needed , having just done sibfest durdle door i can honestly say it was pretty mental on the way back i couldn`t see most of the way due to the splash mist from smacking the waves,it was a case of judging the waves inbetween the bounce so glad i was out with ribnet and in particular xs400

GJ0KYZ · 06 June 2013, 20:45

Quote:

Originally Posted by captnjack

Not sure where you were, but the whole excursion sounds incredibly iffy (and lucky). 21miles offshore in a 10.5ft SIB?!?

I know I do my fair share of crazy stuff but I have to agree, that's a long way offshore in what is effectively only a rubber dinghy.

Poly · 06 June 2013, 20:58

Quote:

Originally Posted by zurk

i have a 10.5ft soft inflatable with alum floor and 15HP. goes ~30kph with two on board + fuel + gear. caught in relatively bad seas (4ft waves). waves were 45-65 degree angles with 2-3 ft spacing in deep water (21 miles offshore by GPS). it planes well in 2 ft waves but with 4 ft it was hitting the water pretty hard so i went at 1/4 throttle and 8kph. took nearly 2 hours to return.

Locozodiac · 06 June 2013, 23:43

Quote:

Originally Posted by willk

you're waaaay outside the envelope!

Very funny expression, almost flipped my desk chair laughing +1 on that.

Zurk, do like doing cracy things myself, but venturing on a 10 Ft sib that far from coast is out of this cracy world..

Happy Boating

mister p · 07 June 2013, 00:01

Hmmmmm

zurk · 07 June 2013, 01:59

i planed for a bit when coming back. then the sea got too rough so it took two hours to return after that. probably planed for 15 minutes at full throttle, then had to cut back which accounts for the time difference.
we go out further all the time (its 30 miles or so to nanaimo). i dont think its too dangerous as you cant get swept out into open ocean without hitting land unless youre really really unlucky. and plenty of boats are out here. we even one paddle boarders coming through but the coast guard stopped him doing the crossing as he was not wearing a life jacket.

frankc · 07 June 2013, 04:44

I believe you are in a over your head running that far out in such a small craft. You don't need to worry about being swept to sea, as you are already there. Hope you are actually wearing your type 1 PFD while running. A type 2 would be nearly useless in seas bad enough to cause a capsize.

Having other boats in the area may not be so comfortable if you realize what would be involved in getting you aboard safely in rough water. This could put a rescuer in danger as well as you and your crew. His first responsibility is to get his own crew home safely, so you may remain in the drink much longer than you planned.

Once the seas become rough enough that you cannot make speed, you are in a bad situation which should be avoided if at all possible. You should carry enough fuel to be certain that your craft can slug it out at displacement speed for however long it takes to reach sheltered waters. The cost of fuel will be the last thing on your mind if the tanks run dry in sloppy water. A sea anchor might be a good investment for you.

In my humble opinion, you are putting others in harms way as well as yourself by running so far in such a small boat.

Nick Hearne · 07 June 2013, 08:15

When Zurk says open seas
I think you have to remember where he is!
Not saying it is right or wrong but he is in a capable little sib which will remain afloat bar the total air loss!
Where is your spirit of adventure you knockers?

willk · 07 June 2013, 08:31

Quote:

Originally Posted by Nick Hearne

Where is your spirit of adventure you knockers?

I appreciate that you're probably joking, but I put a lot of thought to his question. He's having trouble with 4 foot waves and wants to go faster in them. I mess about quite a bit in a similar boat, going as far but closer to shore. Sea state is the big decider for me - a swell of 6' is no issue, but choppy waves are a nightmare - such a small boat with so much power is sooo easy to flip.

His issue isn't how far he's going, but what his plan is if he capsizes. A larger boat would solve a lot of his problems. A sense of adventure is fine, so long as you really understand the risks.

Nick Hearne · 07 June 2013, 08:54

Wilks OK I agree if he wants to go out in these condition & go faster he needs a bigger boat!

simsy · 07 June 2013, 09:05

All you can do to make the sib run in rough water is makes sure its inflated well, and engine and its mounts are perfect, AND GET TO THE GYMM TO MAN UP and open the throttle.......

simsy · 07 June 2013, 09:06

All you can do to make the sib run in rough water is makes sure its inflated well, and engine and its mounts are perfect, AND GET TO THE GYMM TO MAN UP and open the throttle.......

prairie tuber · 07 June 2013, 09:11

If the total beeline distance from Vancouver to Nanaimo is 30 miles, the furthest off shore you could possibly be while along that path is 15 miles.

frankc · 07 June 2013, 10:30

Aren't we back to the original problem of running a small craft in an area which may be subjected to large waves? It does not matter if you are one mile or 15 miles offshore, you are still facing the same problem.

Willk gives a thoughtful reply which pretty well covers the problem. Looking at the chart does indicate an out would be to take shelter on the far shore to wait out the worst of the sea conditions, but once you are navigating them, you must be certain you are self sufficient.

As far as an inflatable being sea worthy, they are used for life boats. As long as they do not capsize you are safe.

Running along the shore, you would not go out if the waves were 4 feet with a short fetch. If the sea state deteriorated while running though, you should have only a short run to calmer waters. That is completely different from making a long voyage and trying for speed with a small craft.

A spirit of adventure is one thing, but there are reasonable limits. You only have to over reach once to have a problem.

dpround · 07 June 2013, 12:08

Remember that you need margins. I was out with the canoe club. Sea state nothing and a light breeze, but a slightly iffy forecast. A squall came through with the wind speed measured at 40kts. Within minutes we had sea state 3. None of this was an issue as we had an easy landing at any point, the wind was cross shore and the boats are good for sea state 4 at least, but it was a hell of an eye opener!

David

captnjack · 07 June 2013, 16:48

Quote:

Originally Posted by Nick Hearne

When Zurk says open seas
I think you have to remember where he is!
Not saying it is right or wrong but he is in a capable little sib which will remain afloat bar the total air loss!
Where is your spirit of adventure you knockers?

I know exactly where he is, my RIB is 15.5 ft long (33% bigger) and I don't go out in the Strait of Georgia with 4ft seas. Mostly because 4ft seas can turn into 8ft (or 12ft) seas, often with a 5 second period especially if the wind opposes the tide - they are punishing to the boat and me.

He may not be able to actually sink, but if the boat fully swamps (or flips) his gas will be water contaminated, his engine will stall and stop, and he'll be adrift in heavy seas with at best a handheld VHF to call someone to bail out his butt. And he'll be sitting in 50F water getting hypothermia.

Crappy seamanship all around.

Brady · 08 June 2013, 10:02

I've done that crossing a few years back from Eagle Harbour in a 28ft under sail. It's a great stretch, but wouldn't fancy it in a small SIB.
I am a cautious type though.. And in the world today fingers get pointed if you endanger others as a result of your actions.