Overpowered Rib

[medlineIII]

This 8m Astec rib with Yamaha 350V8 seems a bit over powered, maybe 250 HP would have been more than enough, especially considering that almost wears nothing on board...

Astec Rib Yamaha 350 V8 Geas - YouTube

Although maybe it is to catch the bad guys if they escape, but rather it is a vessel for use by divers

[Nick Hearne]

Originally Posted by medlineIII

This 8m Astec rib with Yamaha 350V8 seems a bit over powered, maybe 250 HP would have been more than enough, especially considering that almost wears nothing on board...

Although maybe it is to catch the bad guys if they escape, but rather it is a vessel for use by divers

Don't know about overpowered, but it looks like it blew the budget as nothing left in the kitty to fit it out!

All looks very tame to me!

[Trimix]

What happens if you over power a RIB, doesn't it just go faster

[Maximus]

Originally Posted by Nick Hearne

Don't know about overpowered, but it looks like it blew the budget as nothing left in the kitty to fit it out!

All looks very tame to me!

Power looks fine to me!....Definatly needs some weight forward to make the most of it though

[Poly]

Originally Posted by Trimix

What happens if you over power a RIB, doesn't it just go faster

or it starts to chine walk and flips the crew who appear to have no seats out!

[Dirk Diggler]

Why would "overpowering" cause it to chine walk?

[RMS]

Guardia Civil tend to keep the boats they pull that are shall we say in the "import business" so this could be a a boat that was intended to be run with a bit of weight up front.

[bartiny]

The vids a bit poor but woth the effort

https://www.youtube.com/watch?v=I0sp9S_VHec

[Poly]

Originally Posted by Dirk Diggler

Why would "overpowering" cause it to chine walk?

I'd have thought that would be obvious to you. Are you suggesting that power is not a significant contributing factor in chine walking?

Which bit of my logic is flawed?

Increased power = faster. Faster = more lift. More lift = less surface area in the water. Less surface area = more likely to imbalance. Imbalance + high speed = chine walk.

The advice always given here to people who experience a chine walk is to back off the throttle. There is other advice about trim, engine height etc to try to prevent it - but the universal message is that to stop it rather than make it less likely: slow down.

Its probably exaggerated on boats which are overpowered because they tend to be badly set up too with heavy engines etc.

Now I'm* not saying 350HP on an 8m boat is overpowered, I was answering the question "What happens if you over power a RIB, doesn't it just go faster".

*although ISO6185 suggests it might be!

[Chris]

[QUOTE=bartiny;652381]The vids a bit poor but woth the effort QUOTE].... and is an excellent demo of what happens when you overpower a rib !. Chine walks as soon as he opens it up so a complete waste of time

[bartiny]

.... and is an excellent demo of what happens when you overpower a rib !. Chine walks as soon as he opens it up so a complete waste of time

Thats why I posted it

[Maximus]

Originally Posted by Poly

I'd have thought that would be obvious to you. Are you suggesting that power is not a significant contributing factor in chine walking?

Which bit of my logic is flawed?

Increased power = faster. Faster = more lift. More lift = less surface area in the water. Less surface area = more likely to imbalance. Imbalance + high speed = chine walk.

And Chine walking....if you don't Back off...may well lead to the whole Boat "Hooking"....on its Axis..especially in certain sea States.....not much fun I'm reliably informed!!

[Powerboats]

Can't see any chine walking in the OP's video.

Boat seems to plane early despite being fitted with one of the heaviest outboards on the market and crew and console aft.

Still riding with bow a bit high suggesting capacity for additional weight forward.

Looks like a nice deep-vee forward as well. Totally different boat to the second video.

Not enough evidence to form a negative opinion.

No connection - never heard of them.

[Nick Hearne]

Originally Posted by bartiny

The vids a bit poor but woth the effort

Ha this reminds me of my SR4 she kicks like a mule

[bartiny]

Originally Posted by Powerboats

Can't see any chine walking in the OP's video.

Boat seems to plane early despite being fitted with one of the heaviest outboards on the market and crew and console aft.

Still riding with bow a bit high suggesting capacity for additional weight forward.

Looks like a nice deep-vee forward as well. Totally different boat to the second video.

Not enough evidence to form a negative opinion.

No connection - never heard of them.

Nobody said it was chine walking, the referance to chine walking is in response to post No. 3

[Powerboats]

Fair enough, but as I read it the suggestion was that the original boat was overpowered, and it was then suggested this would cause chine walking.

My point, and I'm sure what Poly was alluding to as well, is that a poor combination of weight distribution, hull design and power delivery are the true factors that result in any badly performing RIB or powerboat design.

[Bigmuz7]

Originally Posted by Poly

or it starts to chine walk and flips the crew who appear to have no seats out!

Originally Posted by Dirk Diggler

Why would "overpowering" cause it to chine walk?

Originally Posted by Poly

I'd have thought that would be obvious to you. Are you suggesting that power is not a significant contributing factor in chine walking?

Which bit of my logic is flawed?

Increased power = faster. Faster = more lift. More lift = less surface area in the water. Less surface area = more likely to imbalance. Imbalance + high speed = chine walk.

The advice always given here to people who experience a chine walk is to back off the throttle. There is other advice about trim, engine height etc to try to prevent it - but the universal message is that to stop it rather than make it less likely: slow down.

Its probably exaggerated on boats which are overpowered because they tend to be badly set up too with heavy engines etc.

Now I'm* not saying 350HP on an 8m boat is overpowered, I was answering the question "What happens if you over power a RIB, doesn't it just go faster".

*although ISO6185 suggests it might be!

Slap on the arse for you Dirk ... and an experienced member too ohh dear

Im with you Poly

[willk]

Originally Posted by Bigmuz7

Slap on the arse for you Dirk ... and an experienced member too

Mr Wiggler has been an Outstanding Member longer than most...

[Dirk Diggler]

Originally Posted by willk

Mr Wiggler has been an Outstanding Member longer than most...

That probably goes over the top of the majority of heads.

I'm fully aware of the reasons for chine walking, and "overpowering" can certainly be a cause of it, but it's more common for it to be caused by incorrect set up, slack steering, too higher motor, worn engine mounts, hull defect or a drivers inability to correct the problem with proper throttle control or incorrect steering inputs.

In my limited experience of set up etc, I've found the biggest problem is not over powering, but driver error.

[Dirk Diggler]

Originally Posted by Poly

*although ISO6185 suggests it might be!

I'm a bit rusty on the current rulings, but I think that wouldn't apply to this particular boat.

I assume you mean iso 6185.62?