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Old 05 September 2007, 18:17   #1
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Sib handling in choppy waters?

Hi guys, got my sib (3.7m, 40hp) out for the second time today and thought id make the 7 mile trip to brighton in it.

I found it a real struggle to be honest (esp way back), it was very choppy and i seemed to be stuck at either *very* low speeds, or when i gave it some gas it would soon hit a big wave, the front would pull nearly vertical and id think i was close to capsizing the thing, before then slapping down again hard!

I now realise why a glass v hull is useful as i saw other boats and jet skis handle the conditions in there stride. Is their any techique to dealing with such conditions in a sib? Im not sure whether the SIB is something im going to have to leave at home until we have pond like conditions - or maybe look for a RIB! Perhaps the sib wouldnt of capsized and i should be brave, get an extra cushion and attempt to ride it out but we really were getting chucked about like nobodies business today.
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Old 05 September 2007, 18:31   #2
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The RNLI seem to manage with their D class. Yes it gives a hard ride - try reducing tube pressure a little. A foam mat on the floor if it's made of wood also helps.

As to flipping over you need to put your crew as far forward as possible into head seas - right aft in a following sea. Proper use of the throttle is also essential.

You certainly need to read the sea correctly - often a zig zag course is best. Read Dag Pike's book called "Inflatables" - it's mainly aimed at SIB users.
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Old 05 September 2007, 18:39   #3
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I think you've got to accept that your boat or you will only do so much. Of course the big boys will fly past you but whatever size boat you get there will always be a bigger one about.
I should imagine that your boat will handle just about any sea. Its just a case of you getting used to going slower and as codders said reading the waves. Sounds like your getting some good experience now. At least your out there. Use what you have now as much as possible and if you want to upgrade then the experience you are getting now will make you a much better skipper when you get that bigger boat.
One thing I remember from my relatively small boat days (3.6m RIB) is that you get very wet and so does all your kit. Moving up to a 4 meter Searider was a big leap and a fantastic experience.
Enjoy for now and post some pics.
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Old 06 September 2007, 06:10   #4
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I presume you are using tiller steering, if so it is a good idea to put your fuel and boat kit as far forward as possible even go as far as taking a bag of sand as ballast in the bow make sure everthing is tied down secure also a 40hp is on the large size for your boat mabe a 25hp would be more managable.
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Old 06 September 2007, 07:01   #5
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I second codprawn's comment "buy Dag Pike's book called Inflatables".

A zig zag course helps a lot (not hitting the waves at 90 degrees, but say at 60 degrees for a few hundred yards and then change course to 110 degrees for the next few hundred yards and then back again.

Lots of weight forward keeps the nose down, but throttle control helps too - you don't want to be hitting the peaks at full power and then accelerate again past the peak if you want to reduce the slamming.
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Old 06 September 2007, 07:08   #6
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Quote:
Originally Posted by zodiacman View Post
even go as far as taking a bag of sand as ballast in the bow
From experience I would recommend one or more spare cans of fuel in the bow rather than sand ballast. I put it down to excitement, but I have run out of fuel on maiden voyages on both my SIBs, but on the second occasion I did have the spare can with me ...
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Old 06 September 2007, 09:08   #7
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I've used an foot zodiac SIB with inflatable keel for a number of years and found that with a 25 hp motor the ride can be quite lively in a chop. Their will definitely be limitations as to how much throttle you can use in rough conditions as compared to larger boats, but as Biggles pointed out, no matter big/capable your boat, there is always a bigger/more capable boat out there to lust after. The key is that you are out there and that even if you might not be able to go full throttle, you will still make headway in a safe (albeit wet) boat with positive bouyancy. Here are some simple things you can do which will help a fair bit;

1. Pay close attention to the weight distribution of the fuel, gear & passengers, as well as. As mentioned previously, moving the fuel tank(s) further forward helps alot. I found that about 2/3 - 3/4 toward the bow generally worked best. Too far forward would tend to cause flexion of the floorboards and cause the boat to porpoise at speed. This may flexion might not be as much of an issue depending on the boat design & type of fabric.

2. Strap everything down tightly to the floor! You can add nylon webbing daisy chain type anchor points to the floor by gluing the ones that already come stitched to PVC or Hypalon patch bases. If you have wood floorboards you can simply bolt (use small SS bolts & nuts) the nylon webbing down, forming loops between each successive bolt. You can also add foot straps for yourself and passenger in this same manner.

3. Thicker ropes for handholds help alot. Hanging on tightly to the thin stock polyethlene ropes that run along the top of the SIB's sponson while bouncing along is very hard on the hands. Adding on a 1 1/4" 1 braided rope (nylon or poly) that is securely anchored to the tops of the sponsons for handhold will be far more comfortable than using the stock rope.
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Old 06 September 2007, 10:37   #8
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great advice on here...
I have a 3.8 sib and 20 hp Yam as well as the SR4.
I learnt so much from running the SIB that it really helped when I got the SR4, particularly with reading the wave action.
Relatively smooth conditions can still be really bumpy in a SIB at speed.
Pay attention to wind / wave direction tides etc... a smoothish run down the coast can turn into a bumpy wet slow crawl back into a head sea, even when
running diagonal to the waves. Confused water and short chop is even worse.
BUT a tiller extension also helped when by myself in the SIB for getting weight forward. Sometimes you just have to slow down. The big Ribs handle it easily, but they have to stand off a beach when you can run the SIB right up on it.
Enjoy
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Old 06 September 2007, 12:06   #9
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thanks for the replies. Mine has a console, not tiller - but next time i will put my passenger nearer the front.

I did find myself trying to read the waves and cutting at angles to my destination but it was so incredibly choppy it was all hard work. I was also trying to work the throttle, esp letting off as i peaked on the top of a big wave and then back on once over it.

I take it letting the waves come at you side on is a big nono?

Ive ordered a copy of 'Inflatables'!
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Old 07 September 2007, 11:21   #10
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Quote:
Originally Posted by prairie tuber View Post
I've used an foot zodiac SIB with inflatable keel for a number of years
PT; that's a pretty small boat...

One thing that PT didn't mention: In choppy conditions, you're going to have to slow down to keep from beating the cr*p out of yourself and your passengers. Swell doesn't matter all that much, but chop is nasty stuff in a SIB.

I was on a dive once when the wind came up while we were down. 2 of us and dive gear in a 14' SIB/40hp. Took us a full 45 minutes to travel the 2.5-odd miles back to the boat ramp, taking the wind from the beam. Ugly day. (In truth, a boat that was pulling up as we were leaving the site dragged anchor, and they lost one of their dive group for about 6 hours, recovered several miles away later that evening.)


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