Totally baffled

Blankton · 05 July 2020, 22:06

last year I brought a zodiac cadet SIB. Unfortunately when I got it home I found that it wasn't in good order, there were lots of leaks. I also noticed that when I let down one side, the other side appeared to loose air, which I assumed to be a failed baffle. This was the final straw, as I wanted the boat for fishing and I didn't consider a single tube to be very safe. I ended up packing it away and buying a new boat.

I got it out today to put it on Ebay. I pumped it up to take photos, when I went to deflate it, I took out one of the bungs, and sure enough the other tube began to deflate, just like before. If I squeezed the tube with the bung in, I could hear the air whistling out of the bung on the opposite tube. What I then realised, was that after a while this sopped and the tube with the bung stopped loosing air.

I am now thinking that perhaps what was happening was that the baffle was "inverting" which caused an initial loss of air in the full tube. What I would like to know is how much deflation in the adjacent tube is "normal"

I've made a video. I should point out that the tubes just had enough air to hold the shape, I hadn't inflated to full working pressure. I had inflated the right hand tube first, then the left, so in theory the baffle would be protruding into the left to begin with. Then I release the valve on the right hand tube.

https://youtu.be/OCFXEboYjjs

I hope this makes sense. I would like to understand if I have a duff baffle or not, I think it will affect the price quite significantly

Is there any other test I could do? I know its not Good practise to pump up one to a high pressure and not pump up the other.

Fenlander · 05 July 2020, 23:08

Is that a two plus bow or just a two chamber SIB?

jeffstevens763@g · 05 July 2020, 23:10

Funny how the two sides go down but not the bow

Fenlander · 05 July 2020, 23:13

Yep thought the same hence my question Jeff to see if the bow is its own chamber.

Blankton · 05 July 2020, 23:17

It's just two chambers.

As you look at it the baffle is in the black segment on the right hand side. So one chamber is just the right hand tube, the second chamber is the bow and the left hand tube.

jeffstevens763@g · 05 July 2020, 23:19

Yes if it is have both baffles gone I would open one valve and see if it goes totally flat

Fenlander · 05 July 2020, 23:22

Yep similar to Jeff to prove it leave one valve open and add a modest amount of air to get the other chamber fully up to shape without being pressured and then lean on it again. If it stays up and no hiss from open valve the baffle is fine.

jeffstevens763@g · 05 July 2020, 23:29

We have a zodiac 310 solid at work 3 chambers plus the keel so sum isle yours same

Blankton · 05 July 2020, 23:30

I think I'm going to do this experiment in reverse. If I pull the plug from the tube which was pressurised second, then the baffle can't invert itself and the other tube shouldn't change at all.

I left the boat for an hour after doing the original test above and the left hand tube didn't get any flatter.

jeffstevens763@g · 06 July 2020, 08:57

when you pump the bow tube up does it stay inflated

Blankton · 07 July 2020, 17:05

I think I have sorted this now. The baffle is good!

I repeated the test, but inflated the opposite tube to the one I was going to deflate first. This ensures that I knew which way the baffle will be inverted. When I pull the plug this way, the other tube stays hard.

https://youtu.be/xdWwjNjR-TE

The baffle must be a sock type structure which can invert either way (depending on which side is inflated first) and holds a not insignificant amount of air - certainly enough to make the non-punctured tube loose some rigidity if the baffle inverts when deflating.

I've made a sketch below. The effect would probably be even worse if the large chamber (the one that incorporates the side tube and bow) was deflated, as the second chamber is only one side tube, so proportionally this would loose more of its air in filling the baffle. I think when using this boat it would be good practise to inflate the small chamber first meaning that this scenario can't happen.

My other boat is 3 chambers, perhaps this lessens the effect, or the baffles are designed in a different way.

I now need to cancel my ebay advert, as I've lusted is as having a faullt with the baffles, which I now think is incorrect.

jeffstevens763@g · 07 July 2020, 17:17

the baffles point towards the stern so pump bow first then sides to fill but not pressurise then bow again then sides to pressure you can do it in three stages if you want i only do twice

Blankton · 07 July 2020, 17:30

Jeff, the boat only has 2 chambers. I thought adding a sketch would make it clearer

Fenlander · 07 July 2020, 18:01

Jeff loves a three chamber SIB!

You are right the baffles are quite large. If you are carefully inflating just part of the boat for some reason it's a surprise how far they "invade" the adjacent chamber... and also how much topping up one chamber will tighten the adj one as the baffle equalises pressure.

jeffstevens763@g · 07 July 2020, 19:37

i must apologize ive never seen a two chamber sib since i owned a rover 40 years ago now it makes sense if you dont pump them both the same then you will get your scenario
still got there in the end

david's right though 3 chambers but ive now progressed to 5

Blankton · 07 July 2020, 19:51

I can't blame anyone for not realising it was only 2 chambers, it doesn't seem to be a very good idea!

Other zodiacs I have seen have also been 3 chamber. Is the cadet a budget model?

I wouldn't fancy getting a puncture in the big chamber when out at sea, it would leave you with a glorified banana boat to try and get home on!

jeffstevens763@g · 07 July 2020, 19:58

Quote:

Originally Posted by Blankton

I can't blame anyone for not realising it was only 2 chambers, it doesn't seem to be a very good idea!

Other zodiacs I have seen have also been 3 chamber. Is the cadet a budget model?

I wouldn't fancy getting a puncture in the big chamber when out at sea, it would leave you with a glorified banana boat to try and get home on!

I think the cadet is the zoom 310 solid is that's budget to be honest any sib with a chamber down would be a nightmare that's why I carry tear aid patches and an electric pump to get me home or to shore.

deeeeps · 06 October 2020, 13:04

Hi, This is probably a daft question but....:
I bought this bung from the RIB Store. It has a one way valve that clearly has to let the water out of the dinghy when in the hoist etc. BUT looking at it the cap on it's little bit of string would have to fit on the outboard side, which seems a bit daft to me.

Please could one of you more knowledgeable folk just confirm for me this is right and that I am not losing the plots? Sadly I have not been able to find installation instructions for this bung assembly (perhaps it is too simple for instructions.)

jeffstevens763@g · 06 October 2020, 13:12

the water should press against the mushroom valve from outside, when underway the water inside the boat pushes past it. the cap is there to shut it off if needed mine has a gate valve on it not a cap. if you cant blow through it thats the seaward side.

deeeeps · 06 October 2020, 15:42

Quote:

Originally Posted by jeffstevens763@g

the water should press against the mushroom valve from outside, when underway the water inside the boat pushes past it. the cap is there to shut it off if needed mine has a gate valve on it not a cap. if you cant blow through it thats the seaward side.

Hi Jeff, many thanks for confirming my thoughts. I just think the bung on a bit of string on the outboard side is a bit daft but I understand.

Thanks again.
Regards
Steve