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Old 04 June 2008, 13:01   #1
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Small ribs - Big seas?

Recently I've been doing a bit of boating in a small brig rib, owned by my uncle and making some modifications to it as he doesn't know all that much about boats, and I've been wondering about the seakeeping qualities of smaller ribs. The boat is a falcon 500 (pics enclosed) 5m long. If you were in a big sea in a rib of this size what would be the advantages of being in our 8.4m redbay? Is there actually any real danger of being in a smaller rib e.g. more chance of being flipped? If helmed by a competent skipper is there any reason why you shouldn't be able to take a rib like this up to the scottish isles?

I have noticed its quite bow high gets airborne alot more than our redbay. Is this necessarily a bad thing? I'm moving the console and fuel tank forward and I'm going to put ballast in the bow lockers to hopefully make it "slice" through the waves rather than leaping over them.

Thought/opinions/views?

Regards

Conor
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Old 04 June 2008, 13:17   #2
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I would not want to stuff the Brig RIB with a nose that big, the damage could be extensive.
In general think the speed you could travel at in comfort would be affected by the length, given the same hull shape.
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Old 04 June 2008, 13:40   #3
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I would not want to stuff the Brig RIB with a nose that big, the damage could be extensive.
..
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Old 04 June 2008, 13:51   #4
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Is stuffing really such an issue on a small boat? I thought weight would've been the problem with stuffing and I can't imagine that boat being more than 500kg fully loaded - how likely are you to stuff it? We've put over 600hours on our redbay and it's only been stuffed once in about a force 7-8.
Why is it that ride comfort is reduced in a smaller boat - is it to do with the v or the weight or the waterline?
I think really I'd be talking about taking it afar on fairly calm days but it would be nice to know if you were our in something a bit big that the boat would handle it.

Regards

Conor

P.S. About the bow being too high, do you think moving the console, fuel tanks etc. forward and using ballast should help?
what would you recommend as ballast and how much of it?
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Old 04 June 2008, 13:57   #5
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The main disadvantage is probably the lack of a deep V hull. It looks similar to a Zodiac Mediline. This means it will have a tendancy to plough, especially if coming off a wave into a trough.

I use my 4.2m Zodiac Pro on the west coast (Lewis) in the Atlantic and in the Moray Firth. Both areas can experience sudden changes in sea conditions, as with any location, but the Atlantic is not for the faint-hearted. Even on a relatively calm day - you will still experience a degree of wave movement, and your speed has to reflect this.

It depends how far offshore you are planning to go. If accompanied by other boats with an experienced skipper on board - then there shouldn't be a problem. Personally I'd stay within 5 miles of the coast.

The chances of flipping it - will be down to inexperience, agressive speed and prevailing sea conditions.

An auxilliary engine would be sensible precaution.
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Old 04 June 2008, 14:52   #6
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What do you mean by "plough"? Is that the same as stuffing?

I would only be taking it to relatively near scottish islands such as gigha and I think the furthest you are from either ireland or scotland is about 4 miles and it would always be with another rib.

I considered an aux engine as we have a 5hp yamaha that would do the job, but I cannot see how you would fit it on the transom as once the main engine is locked to either side there is only about 4 inches till the a-frame. I would have thought that if you're always traveling with another boat and with a modern engine like an etec that the chances of both of you breaking down simultaneously is highly unlikely or is that being naive?

Regards

Conor
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Old 04 June 2008, 15:23   #7
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That doesn't look much different to the valiant 490 I had . My experience was the crew have had enough long before the boat ever felt compromised .

I liken it to riding a motocross bike on a rough track , you can't do it for long but the bike can
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Old 04 June 2008, 15:29   #8
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Quote:
Originally Posted by chorscroft View Post
The boat is a falcon 500 (pics enclosed) 5m long. If you were in a big sea in a rib of this size what would be the advantages of being in our 8.4m redbay? Is there actually any real danger of being in a smaller rib e.g. more chance of being flipped? If helmed by a competent skipper is there any reason why you shouldn't be able to take a rib like this up to the scottish isles?
Conor great little boat but could do with a proper jockey seat. Little chance of it being flipped unless your in breaking waves or driving recklessly. Is there an advantage to being in an 8.4m rib, no, apart from the smaller rib will give to the waves, notice in the last five years on Ribnet it is the big 8m+ ribs that have suffered tubes being torn off. The little rib will be slower, wetter and take some concentration to drive safely but it will get there and unless you hit something it's the crew are likely to give up first before the boat does.

Quote:
Originally Posted by chorscroft View Post
I have noticed its quite bow high gets airborne alot more than our redbay. Is this necessarily a bad thing? I'm moving the console and fuel tank forward and I'm going to put ballast in the bow lockers to hopefully make it "slice" through the waves rather than leaping over them. Thought/opinions/views?
Yes to the console move / replacement but wouldn't put ballast in until you have tried it first.

This little Osprey Sparrowhawk went to the IOM from Strangford Lough 5 times in 1992 in practices for the Round Scotland Race which we completed later that year.

Later we did stuff it off Whitehead, Belfast Lough, but to be fair it was F7 in the North Channel and we were going down the waves with 4 divers and lots of kit. We learnt to use the throttle with bottle from that experience.

Pete
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Old 04 June 2008, 15:42   #9
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Looks like a great wee RIB Conor
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Old 04 June 2008, 16:07   #10
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A ribcraft 4.8M rib has done a full UK circumnavigation. I guess it boils down to the competence of skipper - I have a 5.3M rib and at displacement speeds see no reason why it should flip in anything other than very extreme conditions......the kind of the conditions that I simply wouldn't be out in!!
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Old 04 June 2008, 17:00   #11
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console position

I take the 500 stands for 5 metre rib ?
I have a 4 metre Narwall,I fitted under console stainless petrol tank,but in proportion was farther forward than your Brig,still had some problems with nose coming up when moving off,fitted trim tabs that preety much sorted it out and made more stable in rough conditions.
Stuart
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Old 04 June 2008, 17:17   #12
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Thanks for all your feedback and suggestions guys, keep it coming
Yea jockey seat is a must as the bench seat provides little support and you can't stand up with it but I will leave it in for when other people come out on the calmer days.

@Pete7 I have tried it out and found it to be bow light, but do you think moving the console a metre or so forward and moving the fuel tank will affect the balance enough to do without ballast?

Yea my parents used to have an osprey sparrowhawk that they used for diving around Ireland and it was a terrific boat aswell.

@stul Was it actual trim tabs you fitted or hydrofoils on the cavitation plate? Which one do you guys think is better - bearing in mind how expensive trim tabs are?

Regards

Conor

Also if you could please help me out, I've started a thread entitled securing console/seat to the deck. If you have a chance check it out and give me a few pointers - http://rib.net/forum/showthread.php?t=24880
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Old 05 June 2008, 03:49   #13
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Conor, I would move the console and fuel tank first then take it out with a heavy weight and move it about the boat to see the effect. An old 56lb shot weight should do nicely, but you may find the console and therefore the drivers weight enough. Trial and error I think.

Pete
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Old 05 June 2008, 04:05   #14
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I can vouch also for trim tabs on my 4m Avon, was much for stable in the big stuff and controlled the nose going to high a bit more -
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Old 06 June 2008, 02:17   #15
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What trim tabs did you guys use and how much were they? I don't fancy spending too much so I thought maybe I would just fit hyrdrofoils/doel fins What do you guys think about using these on a small rib?

Regards

Conor
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