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Old 10 January 2011, 13:02   #1
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SIB to a RIB ??

Hi, your thoughts and advice welcomed on this project.

Have been given a 18' SIB, only problem is floorboards are rotten / Fubar, and the rubber "hull" is also Fubar, BUT the tubes are in excellant condition with just a bit of oxidisation, and cleaned up like new, also NO leaks holding air for the past 3 weeks with no sign of loosing air.

SO having built several small boats using stitch and glue method, thinking maybe build a hull and glue the tubes on ? has anyone done this ? is it do able in your opinion ? if you have done this what problems did you encounter and how did you resolve them.

Apologies if this is in the wrong section, but as it is/was a SIB thought logical place to start.
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Old 10 January 2011, 14:06   #2
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Anythings possible!
You should find a few pics on here or RIB's with the tubes removed to get an idea of how it should look.
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Old 10 January 2011, 14:23   #3
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hi Chewy, got a good idea of how a RIB looks with no tubes, but just wondering if anyone else had ever done a project like this ? and if so what probs they encountered. The hull itself should present no problem, apart from working out hull depth as i would like a deep v one, thought about measuring my SR4 up and scaling up the dimensions, could even design it as a flooding hull ?
So back on track, has anyone ever done this before on here ? and any photos ?
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Old 10 January 2011, 21:41   #4
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It is possible, but you have to be able to speak french to do it:

http://www.pneuboat.com/reportages/b...semi/semi1.php

http://alexandre.coste.free.fr/modifYOYO/modif.htm
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Old 11 January 2011, 04:17   #5
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I bet you have it floating but no much more. Legal issues. Thus you may not get the papers to register it, neither assurance.
The hull number is associated to certain conditions.
How many chambers do your sponsons have? How many of them can be punctured and still have the rib version floating? You may get permissions for 2 passengers only.
Of course you can always register as prototype boat rather than homologated by manufacturer. But too risky.
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Old 11 January 2011, 04:26   #6
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Originally Posted by azzurro View Post
I bet you have it floating but no much more. Legal issues. Thus you may not get the papers to register it, neither assurance.
The hull number is associated to certain conditions.
How many chambers do your sponsons have? How many of them can be punctured and still have the rib version floating? You may get permissions for 2 passengers only.
Of course you can always register as prototype boat rather than homologated by manufacturer. But too risky.
Not of that business over here, I think it needs to be in use for 5 years as a home build to sell it on without RCD?
A well built/designed RIB hull should stay afloat with all sponsons deflated.

The sites translated courtsey of google:

http://translate.google.com/translat...i1.php&act=url

http://translate.google.com/translat...YO%2Fmodif.htm
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Old 11 January 2011, 06:02   #7
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Originally Posted by chewy View Post
Not of that business over here, I think it needs to be in use for 5 years as a home build to sell it on without RCD?
A well built/designed RIB hull should stay afloat with all sponsons deflated.

The sites translated courtsey of google:

http://translate.google.com/translat...i1.php&act=url

http://translate.google.com/translat...YO%2Fmodif.htm
Flooding hulls included?
Have you ever seen a 7 meters hull+ 150HP engine drowned while sponsons floating? I did.
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Old 11 January 2011, 06:48   #8
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The first R.i.b,s were only modified S.I.B,s made from plywood , ,even the RNLIs, atlantic 21,s hulls were made of plywood until the mid 70s ,
only difference that i can see is that if you make a hull from a normal inflatable boat , the bow deadrise will be probely in 1 or 2 angles or stages rather than a modern rib hull which is has a gentle curve ,
suppose the best way is to inflate the tubes ,tip it upside down and measure the angles of the bow deadrise to give you a better idea.That is unless you want wrinkly tubes ,,

good luck with the project ,mart
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Old 11 January 2011, 07:43   #9
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Flooding hulls included?
Have you ever seen a 7 meters hull+ 150HP engine drowned while sponsons floating? I did.
Theys a lovely photo of an Atlantic Lifeboat in Cowes with all sponsons deflated, twin engines fitted and about 8 crew on board.... still floating.

I think a flooding hull would sink but then who apart from Avon uses them?
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Old 11 January 2011, 12:36   #10
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mmm some interesting points already.

1st method as per the French way - buy an old speedboat and modify the hull to fit, cheap quick way but with the drawback of having a variable "v" hull.
2nd Method - build from scratch, the way i think i will be going.

IN reply to very good constructive comments:

I have already had the tubes inflated for the past few weeks, upside down, and the bow angle appears to be a steadish slope, don't think that will be to much of a problem with appearance of wrinkly tubes, as it has none at the moment.

As for homebuild with no RCD number, i intend to register the build as you have to with all homebuilt craft, but please note i have NO intention of ever selling the resultant build, it is just a project that will be for my own use and something i enjoy, sad i know, but living so far from the coast you have to have something to pass the time.

The hull will be of a twin skin system with a minimum of frames every two feet apart with stringers full length, giving 24 closed cell foam "floatation" sections, it will also be able to float when all 5 tube sections are inflated and the RIB filled with water, and most importantly, still remain afloat with all sections deflated and loaded with the equivalent of all normal items carried, ie engine of 150kg and a further 800kg to account for other gear and 4 crew.

As you might have guessed, i have spent quite a few hours already number crunching, and even passed hull size / construction to a mate who is a boat designer, and he confirmed my figures are correctly worked out, so it should be a go'er. Just need to wait a bit now for better weather to arrive, or finish my SR4 refurb and get it out of the shed so i can make a start.
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