Floppy tubes!!

[jambo]

Well went to my rib yesterday after 5 months in store and boy the tubes not all but the bow and stern starboard were as flat as pancakes the others were down but not out! This is unusual anyone else had the same problem? I put it down to the extremely low temps we have had over the last two months
Any thoughts?

J

[Ian M]

I found this effect with my old boat. During the summer no problems with tubes deflating, but during the winter one or two compartments would mysteriously deflate. My theory was that the pressure on the inflation valves got so low that it was insufficient to maintain a seal, and so the valves leaked, and the more they leaked, the worse the seal got. Never really confirmed it, just my theory.

[willk]

Originally Posted by jambo

Well went to my rib yesterday after 5 months in store and boy the tubes not all but the bow and stern starboard were as flat as pancakes the others were down but not out!
Any thoughts?

J

Fact is, Jambo, if you hadn't arrived early and interrupted me, they'd all be flat ;-)

[Hightower]

Originally Posted by Ian M

I found this effect with my old boat. During the summer no problems with tubes deflating, but during the winter one or two compartments would mysteriously deflate. My theory was that the pressure on the inflation valves got so low that it was insufficient to maintain a seal, and so the valves leaked, and the more they leaked, the worse the seal got. Never really confirmed it, just my theory.

I had two chambers go flat on me suddenly, a couple of weeks ago. After speaking with you guys up the Hill the other week I've come to the conclusion that one chamber has let air out the valve due to the cold weather reducing the air pressure to such a degree as not to be able to maintain the seal in the valve. This caused deflation of one tube, but because of the way the baffles are designed has made the other chamber in the tube look flat too. All filled with air last week and looking fine so far

[m chappelow]

[QUOTE=Hightower;343406] I had two chambers go flat on me suddenly, a couple of weeks ago. After speaking with you guys up the Hill the other week I've come to the conclusion that one chamber has let air out the valve due to the cold weather reducing the air pressure to such a degree as not to be able to maintain the seal in the valve. This caused deflation of one tube, but because of the way the baffles are designed has made the other chamber in the tube look flat too. All filled with air last week and looking fine so far [/QUOTE

I suppose you could get a couple of soft tubes if the next sections volume/pressure is perhaps smaller than the other , ,like you said it can depend on the adjoining baffles , if the boat has been topped up over a period of time and not in the correct sequence it could be pushing one of the baffles or both the wrong way causing the next tube along to then have a larger /smaller volume of air ,,perhaps a smaller bow quarter section or end cone that maybe be more prone to ambent tempreture changes giving an indication theres a leak ,.suppose you could drop the pressure in all the tubes and re inflate with the correct sequence and see if that has any effect ,

[willk]

Originally Posted by m chappelow

suppose you could drop the pressure in all the tubes and re inflate with the correct sequence and see if that has any effect ,

Could you explain this, please? There are seven chambers on my rib (6.5m) and I haven't encountered this technique - sounds useful.

[m chappelow]

Originally Posted by willk

Could you explain this, please? There are seven chambers on my rib (6.5m) and I haven't encountered this technique - sounds useful.

Hi wilk,when inflating start with the Bow tube/section and in turn work back to the stern ,,most baffles are designed to work that way ,if topping up tubes willy nilly over time one tube may have both baffles from adjoining tubes inverted into it which then causes less volume in that section ,not only can it put strain on a reversed baffle but it can have an effect on ambent temp change ,though i wouldent have thought it would make a tube go compleatly flat ,,, club boats or where different people may have the oppertunity to decide to top up the tubes not in order can be prone to it . i first read about it in an old rnli D class training manual .,,just as a response to the first post though by JAMBO could someone else have let the air out for some reason whilst in storage .

[C2 RIBS]

Originally Posted by m chappelow

Hi wilk,when inflating start with the Bow tube/section and in turn work back to the stern ,,most baffles are designed to work that way ,if topping up tubes willy nilly over time one tube may have both baffles from adjoining tubes inverted into it which then causes less volume in that section ,,, club boats or where different people may have the oppertunity to decide to top up the tubes not in order can be prone to it . i first read about it in an old rnli D class training manual .

This will open up another thread I guess, we received info from a Liferaft manufacturer who was invoved with RIBs to start port side stern and work around the craft in turn ensuring the stern sections were very firm due to taking pressure from waves and boat movements. I always assumed that was the way to do it but only working on last piece of info/guidance

[chewy]

I've always started from the bow and worked down either side, I usually find by the time you get to the stern the last chamber doesn't need any air as the baffles push towards the stern creating pressure.
The other theory been if you hole a tube then the baffle is going to act like an end cone.
If you start at the port stern tube then one sides baffles will be pushing the opposite way to the opposite side.

[m chappelow]

Originally Posted by C2 RIBS

This will open up another thread I guess, we received info from a Liferaft manufacturer who was invoved with RIBs to start port side stern and work around the craft in turn ensuring the stern sections were very firm due to taking pressure from waves and boat movements. I always assumed that was the way to do it but only working on last piece of info/guidance

suppose it depends on how the boat s baffles are made,and how each manifacturer decides how it should be ,
only boat i know of was some avon dinghy/tenders that my company had on a couple of their crusing yachts that were kept in a half deflated state on deck,,, bow rolled up and stern kept inflated with the engine bracket attached ,,,mind i suppose a soft tube on a r.i.b is not as critical that on a s.i.b .,,can of worms lol

[PeterM]

Originally Posted by willk

Could you explain this, please? There are seven chambers on my rib (6.5m) and I haven't encountered this technique - sounds useful.

I tried this last year only to see that it made all the baffles on my boats go the wrong way ( there were big 'pull' markes clear ).

Suck it & see I reckon ..............

[9D280]

My Humber strictly has 7 sections, but two of them (between front & "middle" sections) are only about 18" long. Never seen a "how to blow it up" instruction, but I find inflating the whole lot then hitting the short sections last seems to work.

I originally thought they may be designed to prevent too much baffle movement & a real softening of the bow should one of the side toobs get punctured, but it's only a theory....

[willk]

Originally Posted by 9D280

My Humber strictly has 7 sections, but two of them (between front & "middle" sections) are only about 18" long.

Was she built to be Coded? Mine was, the leisure versions have 5 sections. I'm guessing (as you suggest) that survivability must have been the aim. It's a PITA going round them all though

[9D280]

Originally Posted by willk

Was she built to be Coded? Mine was, the leisure versions have 5 sections. I'm guessing (as you suggest) that survivability must have been the aim. It's a PITA going round them all though

I guess so. Got a DoT plate on the transom (at risk of showing her age!!) Also got double skinning on a good proportion of the lengthm, triple rubbing strake, fuill set of lifting etyes (now removed as the 8 bolt threads in the water weren't helping fuel consumption or speed!)

I believe she started life in the North Sea - Fitted out by Delta before they started making their own........