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Old 07 April 2008, 05:15   #11
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,539
Originally Posted by Boatlover View Post
Hi Guys,

I am new here
Hello and welcome. As Willk says, you'll almost get as many answers as replies to your post!!

Originally Posted by Boatlover View Post
If i want to move 10 people in an inflatable or RIB then how many HP outboard would i need? I want to move at maximum 15 MPH.

I heard you can now get electric powered outboards, are they any good, fast?
That's a small question with a big answer, so I'll try to give an overview: 15mph is the sort of speed where a rib will "lift out" the water and skim across the surface rather than ploughing through the water like a ferry (think of it like skimming a flat stone off the beach). As a general rule, the more weight you have aboard (remember the "average" adult weights the best part of 80Kg) the more power you need to lift it out the water. So, you then need to have somewhere for these people to sit, store the fuel for your bigger engine etc and so the boat gets bigger and heavier...... As said above, you could easily be looking at 80+ HP to get a RIB for 10 "on the plane". Having said that, if you are happy toddling along watching the scenery drift by, a much smaller engine will do the job as you will be staying "in" the water, and so a RIB will probably not be the best thing to use. For that kind of trip a small inboard 2 cyl diesel in a "workboat" type hull may be a far more comfortable and infinitely more fuel efficient way of travelling.

Forget electric - you will need half a ton of batteries to manage that distance!

Originally Posted by Boatlover View Post
One other thing, with a RIB do you inflate them yourself? Or is that only with inflatables.

You know in whitewater rafting are those boats inflatables or RIBS?
Unless you have a willing volunteer to hand, yes, you inflate yourself just like a white water raft.

There are essentially three types of inflatable boat:
1) White water raft type - the inflatable tube goes all the way round, nowhere to attatch an outboard, and the floor is "floppy" and made form the same material as the tubes. Power comes from the paddles.
2) "SIB". A bit like the raft, but with a small inflatable "keel" and a plywood transom at the back to fix an outboard engine to. The inflatable keel keeps the underside of the boat "rigid" and the bottom of the hull taught to allow it to plane. Very bouncy ride in waves, and usually nowhere to sit except the tube round the edge.
3) RIB - Essentially a solid boat with an inflatable tube round the sides. Again a solid transom to hang an engine from. Bigger RIBS can have inboard engines, usually diesel. The solid floor gives better handling through the waves than a SIB, but can't be deflated & rolled up for starage. The Tubes give bouyancy & stability when not on the plane, but generally are lifted clear of the water when moving fast which reduces drag.

Originally Posted by Boatlover View Post
any help much appreciated

Many many thanks
I would second all the "get on a course" posts - that way you will get a better feel for what's out there and what the various boat types are capable of. The "Sportsboat" Certificate (at risk of showing my age ) used to have a "displacelment craft" subsection - any of you insructor types know is that is still the case?

Also you'll need to take into account how you plan to store the boat. For example I am limited in size because I keep mine in my garage, so instantly most of the RIBs out there are too wide to go through the door. If, however you keep it in a Marina / storage yard that's not a problem.......

My initial reaction would be that if there's normally only 5 of you, work out how often you'll have 9 aboard. Mine's 5m long and plated to carry 9 , but there wouldn't be a lot of room! If 10 is only occasional there may be a way round it by having 2 propellors - essentially a "high geared" one for when there's 5 of you and a "low geared" one for hauling 10 bods through the water, but more about that later......

Don't worry about asking more questions, coz that's why we're here - to exchange knowledge. And let's face it we've all probably just created more questions than we've answered!

Oops. That post got a bit long........

9D280 is offline   Reply With Quote
Old 07 April 2008, 07:33   #12
Country: UK - England
Join Date: May 2006
Posts: 127
Originally Posted by willk View Post

Hello Boatlover!

A first post is always a brave step! Your's asks a lot of questions and we'll (always!) have a lot of answers, often condradictory.... If you give us some idea what you're planning to do, we'll have more to go on. 30 miles is a fair lick in any craft. Many will be itching to inform you that RIBS/Inflatables have nothing in common with whitewater rafts, and they don't, despite superficial similarities (tubes). Let us know!
Well said. Another arrogant comment from one of the "ribnet mafia"

springtide66 is offline   Reply With Quote
Old 07 April 2008, 08:13   #13
Locozodiac's Avatar
Country: Other
Town: Lima-Peru
Boat name: Nautile
Make: Sea Rider Boats
Length: 4m +
Engine: Tohatsu 18 /30 HP
Join Date: Sep 2007
Posts: 1,706
Go for the largest HP engine the sib/rib factory recommends (see atached transom plate) if you would like to get the best performance out of it, a real danger to inflate sibs/ribs with air tanks, too much pressure, only permited with prudence on boats that have automatic pressure relief valves. Get a good electric inflator and a manometer.

Happy Boating

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