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Old 23 July 2005, 11:42   #11
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...And if your tube is in the water at speed, you will have very poor high speed handling.
Yer reckon? I take it you've tested this? How about the extra buoyancy giving the boat substantial stability, especially in a beam sea, and allowing rapid progress when others will be rocking, rolling and falling off the crests. After all, a true rib is an upwards development of the inflatable boat.
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Old 23 July 2005, 15:36   #12
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I take it you've tested this?
Yes.

I do take your point about beam seas, but I believe that's only going to be the case at low speeds where the hull has reached it's limit for the conditions. So for small craft, a lower tube will be useful. If the hull were still sitting out of the water, then its going to be using the hard running surfaces and not the soft tube. Hence the technique of "keeping on top" of nasty chop, ie incereasing speed when the conditions get uncomfortable.

Anyway, true RIB a development of the inflatable boat? They're mostly flat, fabric bottomed, whereas most RIBs bear a closer relationship to fast planing craft, speedboats if you like!
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Old 23 July 2005, 16:31   #13
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..Hence the technique of "keeping on top" of nasty chop, ie incereasing speed when the conditions get uncomfortable.
I do that with my tubes in the water, it works fine. However, that technique is mostly only valid in a head sea. For the boats I've had experience of, the effect only really begins to happen at 30ish mph but it becomes reasonably effective at about 35mph+. Given that a reasonable sea is going to have waves advancing toward you at about 15-20mph then the combination of boat speed plus wave speed is in the region of 50+mph for the boat to start cresting the waves neatly. If you are in a following sea, then it would seam reasonable to assume that the boat speed is going to have to be in the region of 50+mph to achieve the same effect. However, because of the wave shape, it does tend to help by ramping the boat up the slope for the jump to the next wave so there is the benefit this gives. The upshot of all my blethers is, that you need a seriously fast boat to use that technique into anything but a head sea and even then the boat must be capable of a good turn of speed. And, if you don't have a very fast boat, in a following sea a comfortable speed to travel is just a couple of mph faster than the wave speed. This eliminates slamming and the boat doesn't attempt to dive into the face of the wave in front. Given that wave characteristics are essentially 'now you see them, now you don't', having the stability of the tubes in the wallowing sea if a definite plus. And, as I previously said, they're a plus in a beam sea too.

Tell me again why I don't want my rib tubes in the water...
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Old 23 July 2005, 16:41   #14
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I take it that you don't ever take any maths classes?

And you certainly don't want your tubes dragging in the sea in a following sea, I would want the least area presented aft - look at a "canoe-sterned" yacht.
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Old 23 July 2005, 17:14   #15
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I take it that you don't ever take any maths classes?
Approximation for easy reckoning.

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And you certainly don't want your tubes dragging in the sea in a following sea,
Yes, I certainly do!

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I would want the least area presented aft - look at a "canoe-sterned" yacht.
That is to allow a following sea to pass by cos they travel slowly.
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Old 23 July 2005, 17:27   #16
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Approximation for easy reckoning.
That's a new way of spelling wrong... I guess you don't take English classes either

So why, in a following sea, would you want to drag your tubes in the water?

And why would you want to exceed the wave speed by 45+mph in a following sea? Do you want to stuff it?
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Old 23 July 2005, 17:32   #17
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Richard, are you drunk?
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Old 23 July 2005, 17:33   #18
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No, but I think you are!
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Old 23 July 2005, 17:33   #19
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I can assure you he isn't but you need to look at your figures again Jeff! (IMHO of course!) And please explain to me the advantage of having tubes in the water in a following sea? (Cos I'm just a girlie! )
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Old 23 July 2005, 17:43   #20
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Please, someone else, is what I've written unintelligible?
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