Tube diameter

Arctic · 24 March 2016, 11:25

More modern inflatable boats appear to have larger tubes than the older boats, especially the small boats. Based on experience here, does it make much difference regarding a dry ride? Some of the boats I have looked at in the circa 3.4m to 4m range have had tube diameters ranging from 38cm to as much as 48cm. I do see the benefit of larger tubes but there must come a point where the internal space is reduced for these smaller boats.

Is there an optimum size for a 4m sib?

jeffstevens763@g · 24 March 2016, 11:42

Quote:

Originally Posted by Arctic

More modern inflatable boats appear to have larger tubes than the older boats, especially the small boats. Based on experience here, does it make much difference regarding a dry ride? Some of the boats I have looked at in the circa 3.4m to 4m range have had tube diameters ranging from 38cm to as much as 48cm. I do see the benefit of larger tubes but there must come a point where the internal space is reduced for these smaller boats.

Is there an optimum size for a 4m sib?

my mercury is 48 cm i wouldn't want anything less as i like to sit on the tubes with bent knees at the right height, plus more load carrying capacity with the bigger tube more free-board safer feeling there are some 50 cm too OMO

cheers

Arctic · 24 March 2016, 11:57

Cheers. My last boat had 45cm tubes and those seemed about right.

Do you happen to know the internal dimensions of your boat and, if so, how they are measured? The spec. sheet for my last boat stated an internal width of 84cm but I am not sure if they measure that at deck level or if it is the min. distance between the tubes.

jeffstevens763@g · 24 March 2016, 12:18

here you go cheers

office888 · 24 March 2016, 12:18

The main reason for this was 4 stroke engines.

Arctic · 24 March 2016, 12:56

Excellent, thanks for that. Now I see the internal width specified is between the tubes as the tube diameters plus the width specified equals the total width. Seems that these type of boats have got wider to allow for the bigger tubes.

That makes sense, 4 strokes are quite heavy, although my latest Suzuki 20hp isn't as bad as they used to be.

Fenlander · 24 March 2016, 13:00

>>>does it make much difference regarding a dry ride?

Yes and to the overall feeling of security out in iffy sea states.

Max... · 24 March 2016, 13:11

All boats differ, eg the Aerotec has a very narrow beam whereas Suzumar boats are big open wide things.....but the bigger tubes are always a better idea in my book

Arctic · 24 March 2016, 13:32

Thanks. I will aim for a boat with reasonably sized tubes then. Never had a boat with less than 45cm diameter tubes and, as mentioned, they seemed fine and the ride was as dry as it can be for a SIB I suppose.

two stroke mick · 24 March 2016, 13:36

In My opinion bigger tubes is not allways better. If the boat is fitted with an oversize tubes I believe it will act like a reverse chine and will result in a harsher ride in adverse sea conditions. My Valiant dr 490 has a tube diameter of 0.48 M. I suspect that these are a bit big for the size of the hull but great to sit on.

jeffstevens763@g · 24 March 2016, 14:05

Quote:

Originally Posted by Arctic

Excellent, thanks for that. Now I see the internal width specified is between the tubes as the tube diameters plus the width specified equals the total width. Seems that these type of boats have got wider to allow for the bigger tubes.

That makes sense, 4 strokes are quite heavy, although my latest Suzuki 20hp isn't as bad as they used to be.

OMO but the 800 mm between tubes is just right the 46/8 cm tube is at the right height for sitting without the need to stretch the leg out [29 in inside leg].wet ride their all wet if the winds in your face and the sea state choppy but thats part of it getting the briny on your face.
i know i keep banging on about the Ron hale site but its very good for comparing different boats and engine specs i short listed them printed the specs out juggled the engines and made my choice based on a sib that would take on what i was prepared to go out in form experience of my diving days with an engine make that i trust having had five of them.

good luck with your choice let us know what you decide on

stainless welder · 27 July 2025, 07:51

I came across a Humber destroyer rib that had been given a major over haul, including the tubes,
The original of tubes with a beam of 5.4m. after the over haul (which in my view was good) the owner put on over sized tubes, what are the pros and more so the cons with doing this?
and what are the cons if they are ill fitting?