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Old 30 July 2020, 20:29   #1
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convert SIB into RIB

Hi
I'm new to the whole SIB RIB world. I have a 18 foot SIB with a 20HP. Love the boat but I find it is a bit sloppy on the ocean. Any kind of wave etc and you really have to watch it. Personally I think for a SIB the boat is too long. 14 Foot would be the biggest my guess.
Ive been thinking about making a fiberglass hull and putting on my SIB convert it to a RIB

Any thoughts or information would be greatly appreciated. If anyone also has any tips or tricks I can do to my SIB to make it a bit more stable maybe I could try that rather than convert it.

I don't mind the boat as is. I get out and enjoy the bay just looking for options
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Old 30 July 2020, 23:59   #2
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A SIB is designed as a SIB. A RIB is designed as a RIB. Converting a SIB to a RIB, if it could be done at all, would produce a costly and unsatisfactory hybrid.

Try adjusting the pressure in your tubes and keel.

If it is still not performing as you would like, then consider trading for one that suits your needs.

The RNLI (Britain's life boat service) uses SIBs of 16 feet length, 50 hp, crew of 3 and up to 5 rescued persons, plus all the heavy safety kit, for rescues on the sea in adverse conditions. A properly set up 18 ft boat — 2 feet longer — with only 20 hp, used within its design limits, shouldn't be "a bit sloppy".

Your problem is likely to be either too little tube pressure or too high expectations.
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Old 31 July 2020, 02:09   #3
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Welcome to RIBnet.

The path that you are describing is the one followed by Atlantic College when they first came up with a RIB. Their initial reason for the conversion was to reduce the damage to the bottom when it was being dragged across the beach but they soon after discovered other benefits of the hard hull.

Does it have floor boards? Are these connected together?

Tube pressures will make a big difference.
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Old 31 July 2020, 03:51   #4
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Hello ECA and welcome to the forum. A photo of your outfit would help us to comment on your idea so we can see what you're starting with.
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Old 31 July 2020, 04:56   #5
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your tube & keel pressures are way too low the boat below is 11 m long and solid as a rock
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Old 31 July 2020, 06:43   #6
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Personally I wouldn’t. You’ll destroy any residual value in the SIB & any result, good or bad will be un saleable.
It sounds like you have a setup problem with the SIB, sort that before you start butchering it.
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Old 31 July 2020, 10:16   #7
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Hi
Thanks for all the responses. My conversion idea was dumb just a thought out of frustration.
I like my boat. From what I have read it's a cheap version. I have a Saturn but it will do me fine.
I think my issue is not enough air. I have a new pump I am going to try. I'll make sure I have proper inflation. I'll test it tomorrow and post an update.
Thanks again
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Old 31 July 2020, 15:05   #8
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Quote:
Originally Posted by east coast angle View Post
Hi
Thanks for all the responses. My conversion idea was dumb just a thought out of frustration.
I like my boat. From what I have read it's a cheap version. I have a Saturn but it will do me fine.
I think my issue is not enough air. I have a new pump I am going to try. I'll make sure I have proper inflation. I'll test it tomorrow and post an update.
Thanks again
What sort of floor does it have? If it's an air floor, pump it up to the right pressure, and check it after it's been in cold water for a few minutes. The cold makes the air contract and the pressure drops.

If it's a sectional wooden floor, you should have side pieces ("stringers") which lock some of the boards together.

And yes, plenty of pressure in the main tubes. If you don't have a gauge, do it firm enough that when you slap the tube with your hand it "rings" rather than giving a flat "bonk".
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Old 31 July 2020, 17:25   #9
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Hypalon sibs are bendy, pvc ones are much more rigid. However, many years ago I had a conversation with Paul Lemmer, some folks may know him others may not, but he's been around boats and ribs for many years; anyway, we were discussing me modifying the hull of a Bombard sib and during that conversation he mentioned that fibre glassing the hull of that model of sib had been tried and was actually very successful so you're not the first to have the idea nor, it seems, is it a completely daft idea.
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Old 31 July 2020, 20:48   #10
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Your 20hp engine is not even close to being big enough. You’ll need a 50+HP engine. It’s slot bevies it’s not getting enough speed.

Air is also a major factor. Pump it up...
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Old 01 August 2020, 17:49   #11
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Originally Posted by Pikey Dave View Post
Personally I wouldn’t. You’ll destroy any residual value in the SIB & any result, good or bad will be un saleable.
It sounds like you have a setup problem with the SIB, sort that before you start butchering it.
Pikey Covered everything I was thinking.
And I like to fabricate shit. But a conversion project will just be expensive and have a street value of less than zero.
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Old 03 August 2020, 14:34   #12
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Quote:
Originally Posted by Mikefule View Post
A SIB is designed as a SIB. A RIB is designed as a RIB. Converting a SIB to a RIB, if it could be done at all, would produce a costly and unsatisfactory hybrid.

Try adjusting the pressure in your tubes and keel.

If it is still not performing as you would like, then consider trading for one that suits your needs.

The RNLI (Britain's life boat service) uses SIBs of 16 feet length, 50 hp, crew of 3 and up to 5 rescued persons, plus all the heavy safety kit, for rescues on the sea in adverse conditions. A properly set up 18 ft boat — 2 feet longer — with only 20 hp, used within its design limits, shouldn't be "a bit sloppy".

Your problem is likely to be either too little tube pressure or too high expectations.
Well said
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