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Old 30 March 2004, 13:23   #1
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Dead rise and nothing to do with Hammer House ...

So you techo bods out there can you explain in short, easy terms, what deadrise means.

Chow

Paul

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Old 30 March 2004, 14:01   #2
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It's the V of your hull, (angled bit between chine and keel).
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Old 30 March 2004, 14:13   #3
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Thanks Mr D,

why can't they all say V and not deadrise.

I don't know boat builders

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Old 30 March 2004, 14:27   #4
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It's this angle:
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Old 30 March 2004, 14:35   #5
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Definitely not this one then?
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Old 30 March 2004, 14:40   #6
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I have just looked at that picture again. Engine could do with trimming in a touch. Fnarr
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Old 30 March 2004, 15:29   #7
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Who's that then, have ya painted your red red then

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Old 30 March 2004, 16:36   #8
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Then how does it then affect your boat?

Low deadrise faster I assume but less seaworthy?

Mines 24 degrees is that low/med/high?

Also i seem to have concave chines how does that affect the boat?
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Old 30 March 2004, 17:17   #9
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Steedthrust

The shallower the V, the easier the boat is to get on the plane. It will need less power, but won't necessarily be faster as this will depend very much on the sea conditions.

The deeper the V the more the hull cuts through the waves giving a smoother ride. It requires more power to drive the boat though.

RIB hulls tend to be medium V (10-16 degrees-ish) or deep V (around 16-24 degrees-ish).

Medium V hulls give a generally good performance with modest size engines, but will be hard work when the sea is choppy. You wil tend to find these at the smaller end of the leisure market.

Deep V hulls are more suited to offshore use, but tend to need bigger engines and are less economical to run.

This is a gross simplification of course as there are all sorts of variations, such as variable deadrise hulls and planing pads to take into account.

Concave chines will add lift, but tend to make the ride harder.

Planing hull design is a remarkably complicated art, and although it may seem that different designs are similar there are often considerable differences. On the other hand there are also occasion when they are a direct copy of something else . . .

John

PS Robin, no not that angle!
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Old 30 March 2004, 17:26   #10
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anything over 18 degrees is considered a deep V ie your at 24 degrees, this cuts through waves, rather than slamming over them. this means deep v hulled boats are more comfortable in choppy / rough conditions. anything less is considered a medium V, generally down to 12 degrees, below that it is unlikely to be found on ribs intended for sea use.

while i was checking my info (it is over 6yrs since i studied boat design - grey cells diminishing) i also found this website that gives some info on boat design aspects- beware though its yankee doodle, so some terminology could be different.

http://www.marathonmarine.com/Boat%2...m#_Toc38684154

boats can be constant deadrise ie. the same angle all along the hull, or variable / progressive deadrise in which case the deadrise increases towards the bow.
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