Perfect inflation procedure

[dhaglund]

How do you all inflate your SIBs? And how do you know if the baffles between the chambers are somewhat in their neutral position when you're done? Getting the pressure right is easy, all it takes is a gauge. But getting the baffles close to their optimal position is a lot harder. That takes X-ray vision, or is there a good method?

I guess this is more of a brain exercise than anything else, but is there an inflation procedure that yields a perfect result? I.e. when done all chambers are at the target pressure and all baffles are in their neutral position.

I've come up with a procedure that works in my head at least. I haven't tried it yet and I don't know how to verify it anyway since I don't have that handy X-ray vision.

Given that you have a pressure gauge, a manual pump and an uninflated SIB. Let's say that the target pressure is 3.5 psi. Then start at the rear and fill the first chamber to some number lower than 3.5, say 3. Then fill the adjacent chamber to the same pressure. Repeat until you get to the last chamber. It doesn't matter how many chambers there are in between the first and last. Before you start with the last chamber all the others should be at the same pressure (3 psi) and all baffles will be fully extended in one direction. Then fill the last chamber with the same volume of air as the first chamber. That means you have to count how many times you pumped the first chamber and repeat that for the last chamber. Now, shouldn't all the baffles be in their neutral position? Or no?

If you didn't arrive at your target pressure just pick a lower or higher starting point.

[Pikey Dave]

Start at the bow & work towards the stern. Inflate all the chambers to 1/2 WP. Then back to the bow & inflate to WP, continue towards the stern. Unless the manufacturer says differently.

[dhaglund]

Originally Posted by Pikey Dave

Start at the bow & work towards the stern. Inflate all the chambers to 1/2 WP. Then back to the bow & inflate to WP, continue towards the stern. Unless the manufacturer says differently.

Isn't that a sure way to leave all baffles in their fully extended position, all pointing towards the stern?

The last one or two chambers, depending on where you start, will always need more pressure than the previous chambers to be able to push back the baffles some, thereby leaving them more centered and all chambers at the same pressure.

[Steve509926]

Surely you would want the baffles inflated away from the prv so that if the pressure increased due to temperature, the prv could dissipate the excess pressure?

[Pikey Dave]

Usually cheaper SIBs only have one PRV in the bow chamber, so by pre-loading the bow chamber, the PRV can protect the other non-protected chambers.

[dhaglund]

I forgot to mention that my SIB doesn't have any pressure release valves (PRV) and my RIB has one on each chamber, so that's the scenarios I was thinking about initially.

So, you're right, if you have PRVs but only on some chambers it would be a good idea to preload those chambers so that the PRV can protect the other chambers as well. But even then I wouldn't want the baffle to be fully extended meaning that it can only work in one direction and not be able to even out pressure in both directions.

[User name]

I do it by inflating all to around 0.5bar/1PSI, stick the floor in, then go around again to bring them up to target pressure. Once done, check the pressures with a gauge.

If you have matching pressures then the baffle is not pushed excessively in one chamber or the other. You just have to be sure to check the pressures as you go. If you fully inflate 1 chamber while the next is empty, the chamber 1 will go up in pressure once chamber 2 is inflated. You simply check the pressures are all equal and the baffle will be fine.

[Pikey Dave]

0.5 bar is around 7.5psi

[User name]

Originally Posted by Pikey Dave

0.5 bar is around 7.5psi

Well spotted. I put the decimal point in the wrong spot.

[Sutty]

Wow, I didn’t realise that inflating a SIB/RiB was so technical, I have been boating longer than most of you have been alive and just blown the tubes up in no particular order and never used a gauge and never had a problem. Lucky eh.😄
.

[beamishken]

Originally Posted by Sutty

Wow, I didn’t realise that inflating a SIB/RiB was so technical, I have been boating longer than most of you have been alive and just blown the tubes up in no particular order and never used a gauge and never had a problem. Lucky eh.😄
.

Same here! Wierd eh🤷

[dhaglund]

Originally Posted by Sutty

Wow, I didn’t realize that inflating a SIB/RiB was so technical, I have been boating longer than most of you have been alive and just blown the tubes up in no particular order and never used a gauge and never had a problem. Lucky eh.😄
.

That way works just fine! As I said, this is more of an exercise for the mind than something practical. But I still think it highlights information that is good to have in the back of our heads. The baffles are a great idea by the engineers for leveling out pressure and keeping our boats performing as well as possible! But we as users need a basic understanding of this design to actually use it.

[Fenlander]

I don't worry too much about baffle direction either. The Aerotec doesn't have any PRVs to consider. The manual doesn't tell you which chambers to inflate first just stating to inflate all to 50% then all to 100%. While there is no reference to the baffles in the text they are drawn in as dotted lines facing rearward.

I just add in one extra step to the manual at the start and another at the end. I fill all the chambers in turn to shape but before any pressure registers. Then I go round and do the 50% in all and then 100%. About ten mins later when the motor and rest of the kit is on I go round again in case any element of material stretch has lowered the pressure.

Re the HP air floor I now over inflate by about 10% to offset the loss when launched into cold water rather than the faff of checking pressure after launch.

[dhaglund]

Originally Posted by User name

If you have matching pressures then the baffle is not pushed excessively in one chamber or the other. You just have to be sure to check the pressures as you go. If you fully inflate 1 chamber while the next is empty, the chamber 1 will go up in pressure once chamber 2 is inflated. You simply check the pressures are all equal and the baffle will be fine.

I'm afraid I have to disagree with some of this. Even if the chambers have matching pressure that says nothing about the baffle position. Checking that pressure is all equal makes no difference at all. The baffle can be in any position when pressure is equal. That's the whole point of this design. The only thing one can be sure of is that if pressure is not equal then the baffle is fully extended.

But when you say that "chamber 1 will go up in pressure once chamber 2 is inflated" that is key! The second chamber will always need more pressure than the first to push back the baffle into a more neutral position. The result will be that both have the same pressure and that pressure is a little higher than what chamber 1 had to begin with. This part is easy to prove. Because if the baffle is pushed back some into chamber 1 then the volume of chamber 1 has decreased. Since the amount of air is the same the pressure will rise. So unless pressure has risen the baffle has not been pushed back. This assumes no leaks and constant temperature. Both of those variables can mess this up greatly.

[Pikey Dave]

Originally Posted by dhaglund

I'm afraid I have to disagree with some of this. Even if the chambers have matching pressure that says nothing about the baffle position. Checking that pressure is all equal makes no difference at all. The baffle can be in any position when pressure is equal. That's the whole point of this design. The only thing one can be sure of is that if pressure is not equal then the baffle is fully extended.

But when you say that "chamber 1 will go up in pressure once chamber 2 is inflated" that is key! The second chamber will always need more pressure than the first to push back the baffle into a more neutral position. The result will be that both have the same pressure and that pressure is a little higher than what chamber 1 had to begin with. This part is easy to prove. Because if the baffle is pushed back some into chamber 1 then the volume of chamber 1 has decreased. Since the amount of air is the same the pressure will rise. So unless pressure has risen the baffle has not been pushed back. This assumes no leaks and constant temperature. Both of those variables can mess this up greatly.

I take it you're somewhere north of the Arctic Circle & the sun hasn't come up yet

[User name]

Originally Posted by dhaglund

I'm afraid I have to disagree with some of this. Even if the chambers have matching pressure that says nothing about the baffle position. Checking that pressure is all equal makes no difference at all. The baffle can be in any position when pressure is equal. That's the whole point of this design. The only thing one can be sure of is that if pressure is not equal then the baffle is fully extended.

But when you say that "chamber 1 will go up in pressure once chamber 2 is inflated" that is key! The second chamber will always need more pressure than the first to push back the baffle into a more neutral position. The result will be that both have the same pressure and that pressure is a little higher than what chamber 1 had to begin with. This part is easy to prove. Because if the baffle is pushed back some into chamber 1 then the volume of chamber 1 has decreased. Since the amount of air is the same the pressure will rise. So unless pressure has risen the baffle has not been pushed back. This assumes no leaks and constant temperature. Both of those variables can mess this up greatly.

That's exactly my point of partially inflating, rather than fully inflating one by one.

[Steve509926]

This is now getting very confusing for the uninitiated. I completely understand where everyone is coming from, however it really does depend upon whether the sib/ rib has prv's fitted or not and whether it has only one fitted (in the bow) or one per chamber. To my way of thinking at least three scenarios (maybe more) are correct and one cannot say "my way is right and your way is wrong" it all depends upon what sib/rib you have. I'd suggest follow the makers advice, if it's given.
I do agree with Fen though, I over inflate the keel and deck by 10% (this is in the UK) because as soon as my sib hits the water, it's acts like a turtles gonads and shrinks!

[jeffstevens763@g]

My boat has a prv in the bow so bow first then to the stern inturn so it releases all chambers on a temp rise, having said that if the bow gets a large slit all chambers go down not a great scenario at sea. I preferr to pump stern forward so at least my engine has support if I do hit something causing bow chamber failure. My baffles face the stern but will still inflate even if the previous chamber is at working pressure. I control my chambers manually if required.

[Right Turn Clyde]

BTW, in addition to the procedure, there's the question of quick gauging of psi.

I recently spoke with the owner of K-Pumps here in the US, whose K-100 I have used (on our whitewater rafts). He shared a new product that helps reach a targeted psi without the need for a finnicky gauge.

The K-Air devices have pre-set "blow off" valves that use a known psi. The lowest psi model is ~2.5psi. So, if you keep pumping after the tube has reached 2.5psi, the new air you pump will bleed out the side valve.

It's a pretty interesting design, and very compact. There are some additional benefits that their web site and YouTube videos explain.

BTW, the owner, Jim, is 80yr old and still daily running the Oregon company.

s

[jeffstevens763@g]

Originally Posted by Right Turn Clyde

BTW, in addition to the procedure, there's the question of quick gauging of psi.

I recently spoke with the owner of K-Pumps here in the US, whose K-100 I have used (on our whitewater rafts). He shared a new product that helps reach a targeted psi without the need for a finnicky gauge.

The K-Air devices have pre-set "blow off" valves that use a known psi. The lowest psi model is ~2.5psi. So, if you keep pumping after the tube has reached 2.5psi, the new air you pump will bleed out the side valve.

It's a pretty interesting design, and very compact. There are some additional benefits that their web site and YouTube videos explain.

BTW, the owner, Jim, is 80yr old and still daily running the Oregon company.

s

Yea the pump I use shuts off at the predetermined psi but it’s not an exact by any means if you pump up to the working pressure and then sit on it in my case 18 stone the psi rises to what I don’t know even more when bouncing in the chop in my experience pump em up until their solid let air out when it gets too hot end of.never had any problems in 50 years of boats