Balance, Ballast & Chine Walking

[thomas]

I nipped over to Bembridge for a beer yesterday and experience chine walking for the first time, I know this gets covered from time to time but I guess most peoples problems are down to different things.

I started off on my own and it was terrible I then picked up a passenger at Chichest Bar (who was not enjoying sitting at the bow of another RIB) and I could go a lot faster but still had problems approaching top speed.

My trim sender is broken at the moment which is not helping but I also have an engine 10kg heavier than most which makes my bow sit very high when it's sitting still. Does anyone load up the front to balance the boat and if so what with? I was guessing 10kg but surly it can't be that simple - I have an 8kg anchor with 4m of 10mm chain that must offset the extra engine weight.

Would be good to hear what other people do to get round the problem, the boat is a Ribtec 585 with a Merc 115 - the steering has no slop at all.

[Pikey Dave]

Is this a new problem or a persistent one, has the boat been ok previously? If so what's changed?

[C-NUMB]

At what speed does it starts to do so? Adding weight in the bow would be an easy thing to test, but it does not always cure the problem.

[thomas]

This was my first proper outing in flat conditions since I bought it, I've had it up to speed before but not for any amount of time - where I am it's pretty lumpy and through decent waves its fine but not as fast.

It probably happens about 34 knots, can't be exact as I eased the throttle back when it started.

[Kernow Buoy]

Hi Thomas, I've also got a 585 Ribtec, originally it had a 90hp Yamaha, top speed 30 kts with no hint of chine walking irrespective of load.
I eventually put a 150 Opti on and at 30 knots it was starting to chine walk, at 34 knots it was time to slow down! I added an extra 7.5 kg anchor & 5m chain to the bow locker, brimmed the fuel tank and the handling was transformed, now cruises comfortably at 30 kts and has hit 46 kts but was starting to wobble (although that might have been me!)

[thomas]

Thanks, when you say an extra anchor and chain, what was there already and how many people?

I have a load of lead shot in bags plus I need a kedge anchor, as got blown on to the beach whist in the pub, nearly there a long time!!, so will fill the locker up and see, will try and persuade the Mrs I need a 150 Opti too but don't fancy my chances

[C-NUMB]

Flat conditions are typically the worst for chine walking, as then there is no "stabilizing" effect from the waves increasing the wet surface of the boat. Small chop from the bow works often well on boat that chine walks in the flat. lets hope the weight in the bow will sort it out. Then maybe lifting the engine or testing another prop will be the next stage?

[Kernow Buoy]

Originally Posted by thomas

Thanks, when you say an extra anchor and chain, what was there already and how many people?

I have a load of lead shot in bags plus I need a kedge anchor, as got blown on to the beach whist in the pub, nearly there a long time!!, so will fill the locker up and see, will try and persuade the Mrs I need a 150 Opti too but don't fancy my chances

There already was a fairly small (5kg I think) grapnel and 5 metres chain. Load on both occasions was 2 people, if I remember correctly I added about 50 litres of fuel so a not inconsiderable load as well, not sure I need a 150 either

[thomas]

There's need and nice to have.

I'll get myself a 7.5kg bruce copy to add to my 8kg grapnel and see it if helps.

[Pikey Dave]

What prop do you have on the Merc?