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Old 20 February 2018, 15:13   #1
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Planing speeds & harbour limits...?

Can anyone offer a general view on typical speeds that a 5-6m rib would get on the plane???

The local harbour limit is 10kts... and extends a long way :-(

Possibly renders a rib pointless...?
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Old 20 February 2018, 15:37   #2
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Can anyone offer a general view on typical speeds that a 5-6m rib would get on the plane???



The local harbour limit is 10kts... and extends a long way :-(



Possibly renders a rib pointless...?


13-15kn depending on engine & prop. Planing speed is a function of hull length.
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Old 21 February 2018, 04:25   #3
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Thanks, thatís the sort of speed I had in mind... and explains why most ribs I see motoring around look like they are wallowing stern down and not quite planing :-(

Depending on interpretation / enforcement it is either 4.5 or 7km to get outside of the 10kt limit 😳
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Old 21 February 2018, 04:31   #4
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Thanks, thatís the sort of speed I had in mind... and explains why most ribs I see motoring around look like they are wallowing stern down and not quite planing :-(



Depending on interpretation / enforcement it is either 4.5 or 7km to get outside of the 10kt limit


It's all bollocks really, a planing hull at displacement speed will throw a much bigger wash than if it was allowed to plane. But that's bureaucracy for you.
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Old 21 February 2018, 05:29   #5
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It's all bollocks really, a planing hull at displacement speed will throw a much bigger wash than if it was allowed to plane. But that's bureaucracy for you.
Trim the engine right out, place all the weight at the back, drive at 6.9 knots past the enforcement guys and the G&T brigade, saying "What?, i'm under 7 knots "
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Old 22 February 2018, 07:49   #6
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Planing speeds

Most Ribs do start planing around 12/13 knots, however SIBs can plane at much slower speeds due their flat hull profiles and certain Ribs, such as the unusual Hysucat and some non deep V flat bottom Ribs can plane below 12 knots.

In general though, the reason for speed limits is to limit the amount of wash and this can be significant on larger cruisers etc, although ironically most ribs create less wash when planing than they do at 10 knots!

Basically, unless you have sizeable trim tabs (unlikely) to keep the bow down to assist the crafts attitude, you will have to join the rest of us who adhere to harbour/river speed limits.
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