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Old 21 February 2006, 16:50   #1
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planing surface???

i see that on some ribs, there is a flat area which tapers to the keel.
what does this do? and does it give a different measurement for the length of the shaft on the engine leg?
one boat i saw was a osprey vipermax 7.00, and this by the looks of it has an insert placed in the mould before manufacture. if the hull was made without this flat surface then the actual keel would be 1 3/4" lower.

steve
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Old 21 February 2006, 16:55   #2
pop
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i think what would happen is she would just dig in and never get on the plane . this is on the back 3ish ft i presume you are refering to? this is a part of the hull that works hard to get you on the plane . hope this helps
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Old 21 February 2006, 17:00   #3
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Quote:
Originally Posted by pop
i think what would happen is she would just dig in and never get on the plane . this is on the back 3ish ft i presume you are refering to if so this is a part of the hull that works hard to get you on the plane . hope this helps
Don't think so, our boat is flat towards the stern so are the RNLI atlantics and a few more!! This is the planing area, as long as your cavitation plate on the outboard is in line or just below this area as with all hull designs will give you no problems!!
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Old 21 February 2006, 17:03   #4
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oooooooo very nice
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Old 21 February 2006, 17:06   #5
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This is called a planing pad, which as its name suggests, gives improved lift, helping the boat get out of the hole and 'onto the plane' quickly. It can also add stability at high speed and reduce the likelihood of the boat chinewalking, as it offers more of a contact patch with the water.
The 'transom height' or position of the cavitation plate, relative to the underside of the hull will vary according to what the demands of the boat are. Basically, the less leg in the water, the higher top speed will be achieved through less drag, but drive in turns may be compromised with some ventilation (prop spin) on tighter turns, particularly when the motor is trimmed out. Some boats with a constant 'vee' keel have the motors rigged high, while others with a planing pad have the motors set lower, depending primarily on boat load and application.
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Old 21 February 2006, 17:34   #6
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It would follow that a slightly flatter section at the back to the boat would allow it to plane more easily, but surely if it was a completely flat section, the handling at flat out speeds would be messed up?

What I'm thinking, is that if the boat's well up to speed and trimmed out with only the back section in the water, it would tend to skid sideways from the stern when you cranked the wheel over, there being no v-section to hold onto the water...... Sideways you go. And bloody scary too

Does that make any sense?
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Old 21 February 2006, 17:55   #7
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Quote:
Originally Posted by endeavour boats
i see that on some ribs, there is a flat area which tapers to the keel.
what does this do?
It saves rib makers waiting for XL shaft engines in my opinion.

Jono
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Old 22 February 2006, 03:41   #8
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Quote:
Originally Posted by Franx
It would follow that a slightly flatter section at the back to the boat would allow it to plane more easily, but surely if it was a completely flat section, the handling at flat out speeds would be messed up?

What I'm thinking, is that if the boat's well up to speed and trimmed out with only the back section in the water, it would tend to skid sideways from the stern when you cranked the wheel over, there being no v-section to hold onto the water...... Sideways you go. And bloody scary too
Does that make any sense?
I hear what your saying but on the Viper hulls it just doesn't happen. The planning pad helps to get a heavily loaded boat up on the plane quickly but possibly at the expense of some high speed handling however we are talking high speeds. At 50 mph the 5.25m is getting a little flighty but then it is only a 17 foot boat.

The big advantage in addition to getting on the plane quickly is that the engine is mounted 3 - 4 inches higher on the transom and therefore the transom top can be higher reducing the amount of slop that comes over the back of the rib if you stop quickly or have a boat full of heavy divers.

The viper series don't go sideways and do carve a turn beautifully with full control.

Pete
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Old 22 February 2006, 06:39   #9
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My Ribeye 785 has a flat planing wedge at the rear and although it took some getting used to(how easy she gets on the plane)she rides very well with strong grip on turns and no aeration on the prop and surprisingly no slamming from the flat section.
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Old 22 February 2006, 14:20   #10
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My Northcraft 6.5 has one. Its 3 feet long by about 18 inches wide. At WOT she sits on it steady as a rock, no turning problems at all, no chine walking. What I will say is my cav plate is a good 3-4 inches higher than the pad, running an opti 150, when it was level, to start with we lost 1000 rpm, and it laboured horribly, now it breathes much more easliy. The only crit I've got of this combo is, that if you do a full power take off, or if you are pulling up a skier, you get a certain amount of prop slippage, due to flat bottom preventing all of the prop 'getting water',once you start moving, but its a small price to pay.

Also I can launch in very shallow water off the trailer
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