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Old 30 December 2006, 10:23   #1
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Deadrise - speed vs comfort

If I get the orange peril fixed and sold later in the year, I'll obviously be replacing it. The Mac range of plastic boats is the favourite option at the moment because of toughness and not needing to antifoul, but I was just looking through a "rib buying guide" thing that came with Rib Intl a couple of issues back and looking at the specs of some of the other craft, it is not as deep V hull. The Mac 570 is 18 degrees deadrise versus 25 deg on the current Destroyer, which I suppose is probably the same hull as mine? The Ribcraft 5.85 is 22 deg, the Ospreys (which is what I am most interested in) don't appear in the guide at all, which is odd as there are a load of makes that I have never heard of. One thing I really do like about the Destroyer is that it rides very well in choppy conditions and having been out in a similar size fibreglass boat yesterday afternoon, it was so noisy after the RIB, even in fairly nice conditions.

I know there are a lot more variables than purely the deadrise but is this likely to make much difference to the ride in choppy conditions? There are some video clips of the boats on a DVD that I got sent to me but only in relatively calm conditions so its hard to tell.

thanks

Stephen
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Old 30 December 2006, 12:50   #2
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Stephen, I think you might find your Humber has a variable deadrise along with the central planing pad. It's never quite a simple as we might like it to be.
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Old 30 December 2006, 13:32   #3
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Bow shape and weight has a lot to do with ride quality, particularly in the rough stuff. You will, I suspect need a deep V as well. For your environment I suspect you'll always have to comprimise on outright performance but that is all relitive, as optimum performance for a given geographical area will differ.

I like the Viper as it seems to have all the bits in the right places and dosen't seem to comprimise it's Sea Keeping qualities for outright performance. I haven't found anyone who has a bad word to say about it.
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Old 30 December 2006, 14:06   #4
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Hi Steve

You find it hard to beat the hull you've got!

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Old 30 December 2006, 16:21   #5
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Hi Steve

You find it hard to beat the hull you've got!

Jono
Jono,

I agree, the hull is great, its just the floppy bit around the outside that spoils it... by the way you have a PM.

The other thing with the Mac is that it seems to be pretty constant V all the way down the hull (about 3/4 the length) till it tapers to the bow whereas the Humber hull, as jwalker suggests, is a sort of tapered arrangement with a greater angle at the sharp end.

Would really like to try all the options back to back in the same conditions but I suspect that's not very practical! Mac do a deeper V boat which doesn't look like a RIB (don't really like it anyway) but the hull shape looks all wrong to me for performance.

Maybe if somebody gives me a free hull & tubes I won't need to buy anything
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Old 30 December 2006, 16:33   #6
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The other thing with the Mac is that it seems to be pretty constant V all the way down the hull (about 3/4 the length) till it tapers to the bow whereas the Humber hull, as jwalker suggests, is a sort of tapered arrangement with a greater angle at the sharp end.
I should have been more precise. What you described is known a warp. Variable deadrise is a V-hull with more than one angle in the V. If you look closely, or get out a sliding bevel, you'll see that the lower part of the hull up to the spray rails at your transom is a lesser angle than from the spray rail up to the tube flanges. This is not uncommon. I have also seen the angles the other way, ie. sharper at the lower section although I have no experience of a hull like that.
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Old 30 December 2006, 17:23   #7
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Stephen

If your thinking of a hard boat, have you looked at a rigid raider?

Jono
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Old 30 December 2006, 17:33   #8
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Stephen i have owned various ribs and hard boats to hoot, and every time i want to go out and the water looks a little lumpy i say it all over again. i
want my osprey back,
Ribs are what they are. a bloody hard to beat water craft,
you have been unfortunate in your purchase, but sort your tubes out you will not regret it afterwards, specially with the sea states we have to deal with,
good luck with whatever you choose,
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Old 30 December 2006, 17:39   #9
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Stephen

If your thinking of a hard boat, have you looked at a rigid raider?

Jono
I have, in fact I was trying to separate one from its owner before I bought the RIB but he wouldn't sell. Two months later it was up for sale for a lot less than I paid for the RIB and damn don't I wish I had waited with what's happened since but its now been sold again and its the only privately owned one here AFAIK.

The trouble is the ones available ex-MOD all seem to need a huge amount of work doing and the other problem is that they either need loads of power (twin Suz DF140s on the Defence Force one here) and that means loads of fuel and will limit my use, or with a smaller power unit they aren't that quick - and I must admit I have grown fond of the fun side of 30 knots in the last few months


On a separate question but related to the issue, has anybody got any comments about the likely performance of a 5.5m 80hp Vipermax versus a 5.8m 115hp? Jono has got an excellent deal on both and I wondered if I could save 5 grand and go for the smaller one without losing too much fun...?
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Old 30 December 2006, 18:27   #10
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Stephen

I would go for a Mariner 2 Stroke as dead simple if anything goes wrong.

Jono
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