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Old 06 September 2004, 10:32   #1
Country: UK - Channel Islands
Town: Jersey
Boat name: Bateau de Hell
Make: ProSport
Length: 8m +
Engine: 4 stroke Suzuki 250
Join Date: Oct 2003
Posts: 38
Tube stress!

Should the tubes be clear of the water when the boat is at planing speed? The tubes on my boat drag, and obviously wobble like mad at speed. I am concerned that this might put undue stress on them, and also can't do much for efficiency both in terms of fuel economy and speed. Should I be concerned? Are my tubes normal?

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Old 06 September 2004, 10:43   #2
Country: UK - England
Town: I.O.W/Bristol
Boat name: HotShot
Make: shakey
Length: 5m +
Engine: 70hp Tohatsu
Join Date: Jul 2003
Posts: 1,543
A quick answer for you...

depends on your boat
Some have high tubes that clear the water at speed (only coming into effect when cornering) which mean higher speeds but less stability.

Some have lower tubes for more stability at rest and at speed. The extra drag reduces top end speed a bit though.

The tube will wobble around like jelly but I think this helps to absorb some of the shock of a heavy sea.

Hope that helps


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Old 06 September 2004, 11:01   #3
Country: Ireland
Town: Dublin
Boat name: WIZARD
Make: REDBAY 7.4
Length: 7m +
Engine: OPTI 225
Join Date: Aug 2002
Posts: 417
I think that tubes should be run farily hard......

Because as the tubes vibrate... they are moving around , and they could be chafing against the fiberglass mounting coller, this over a long period of time could wear a hole in a tube , in a place which is a pain in the arse to repaire....

Just a thought ?
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Old 06 September 2004, 11:07   #4
Country: Austria
Town: vienna
Boat name: --
Make: avon
Length: 4,7
Engine: Mercury 500
Join Date: Jun 2004
Posts: 37
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Yes, many boats handle this different. Some are designed to get out completely. Mine for example has a pretty high deadrise and comes out of the water completely. Some others i saw, always have some Tubes in the water, and go pretty fast though.

The drawback with the Tubes out of the water is the stability at higher speeds. When i go around 27knots, my boat "whips" a bit, when i do some slight turns, while the other desingns are lying rock solid in the water.
On the other side, i always stay dry in my boat, where the others get some spray inside.

To be honest, in my region the vast majority of RIB's always have the Tubes in the water at the Transom and some way forward. My Avon is quite exotic here. All the "italian style" RIB's have a much lower deadrise an the Tubes down...

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Old 06 September 2004, 11:11   #5
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Country: UK - England
Town: Bucks
Boat name: Blue & Ding Dong
Make: Ribeye,SR4 & Bombard
Length: 6m +
Engine: 115,50 & 15Hp Yams
Join Date: Feb 2004
Posts: 3,246
Sounds like you may want to put some more air in your tubes!
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