New F-Rib 375 - Feeling Somewhat Deflated

[harrison]

This is very weird Harrison, there must be some answer to the problem. .

Yes, there is an answer to the problem, fit a reliable over pressure valve or don't fit one at all!

[blootac]

All fixed now then Harrison?

[harrison]

All fixed now then Harrison?

Not fixed, but definitely resolved!

[Paul]

All fixed now then Harrison?

Not fixed, but definitely resolved!

Hi Harrison
Sorry to read you've now returned your F-Rib for a refund as I was looking forward to your comparisons against your Bombard
I know they are totally different boats by way of construction, design and usability but just wondered just the same
How you ended up with a boat with 2 defective pressure relief valves fitted on the same boat is very, very unfortunate
Maybe you'll return with your F-Rib ordered without relief valves fitted in the near future.

Paul

[harrison]

Paul,
Thanks. I don't think I had a boat with two defective over pressure valves, I think the valves fitted are just an inferior product. Both valves were clean but would blow off prematurely, one at approx. 0.18 and the other at 0.20 bar, they would then proceed to leach pressure at a slow rate so after 4 or 5 days the pressure in the three tubes would drop to 0, 0 and 0.05 bar.
Even within an hour on the water the tubes would be well under 0.18 bar, and that's after re-inflating after temp drop when on the water. In fairness to boat, it is essentially a rib, so soft tubes really doesn't affect performance, but the stated running pressure on the transom is 0.25 bar so I think the tubes should really be capable of maintaining this operating pressure. It is worth noting most larger non folding ribs only run their tubes at 0.20 bar!
I think the biggest problem for me was I leave my boats inflated (albeit at half pressure), and covered, on a trolley in the season, so the F-Rib wouldn't even hold its shape after a week or two. This may not be an issue, or even a realisation, if you inflate and deflate your boat after each use. In addition to this it would always be difficult to tell whether you ever had an actual leak elsewhere on the tubes in the future.
In terms of performance I was impressed on the water. It out performs any sibs I've piloted, so in fairness should really be compared to the smaller/lighter ribs out there. The hull is significantly more efficient (faster per hp) and has lots more bite in the turns, thanks in part to the hard/reversed chines. One thing to note, as it is only a 12 degree shallow V hull, it is more suited to flat water, as found in its home market. It will however handle swell and chop, but don't expect a comfortable ride as apart from lacking the deep V it just doesn't have the weight or length to cut through the water.
As for build quality, I would rate the glass fibre hull first class and the tubes as average. Aside from the questionable pressure relief valves, overall neatness and visual quality of the seams and finishing detail is below average compared to the more well established brands of sibs available here. This is purely based on aesthetics and in no way is a reflection of the strength and integrity of the tubes.
For the price and performance benefits, I could live with the minor aesthetic niggles, but for me I really need the confidence the tubes will remain at the desired pressure.
Will really miss mine, hope you guys enjoy yours.
Harrison

[Paul]

Harrison
I didn't realise you had actually had your F-Rib out on the water because of your relief valve problem so it's nice to get your comparison and impressions
I got my F-Rib360 about the same time as you took delivery of yours so I was rather concerned that I may have the same pressure relief issues with mine so immediately inflated it to .25bar as recommended and left it overnight. The following evening I rechecked the pressures and had to give it a minor top-up but that was about it. I think the small drop was due to the warm air from the initial inflation and air temperature change overnight.
The boat then sat in my garage for nearly 4 weeks with me rechecking the pressures and I'm pleased to say it maintained the correct pressures throughout this time period, hence my post of your unfortunate problems and could only assume that 2 defective valves were to blame.
This assumption of defective relief valves was also based on myself inflating the F-Rib375 Steve gave us to sea trial with my Bravo pump. I inflated that boat personally to 0.25bar and rechecked with a gauge prior to going out to sea once we had transferred and mounted my outboard and other ancillaries, that boat also maintained its pressure during the days testing.
A comprehensive test of my relief valves will take place during my summer holidays in Spain where the boat will remain inflated for 3 weeks moored on a pontoon albeit with a cover over it to prevent UV erosion but will be subjected to the heat/air temperature changes.
Thanks again for your comments

Paul

[Paul]

Following on with this thread and with a 'free' weekend in the 'man shed' I decided to carry out my own experiments with my F-Rib relief valves and possibly shed some light on their operation to possibly help other owners in the future

My 360 hasn't had any loss of pressure issues at all even over long periods of inflation so I pumped it up to the specified 0.25bar and left it 12 hours, rechecked the pressures and they were still 0.25bar.
I began to release the dust covers which takes no effort at all with your fingers and immediately both valves began to release air and continued to do so until both side chambers reached 0.20bar and the valves then closed.
I connected the Bravo pump to inflate each chamber with the dust caps off and sure enough 0.20bar was the maximum the relief valves would allow.
I left the boat another 12 hours with the dust caps off, rechecked the pressures and they remained at the 0.20bar and the front un-reliefed valve baffle chamber also gave a reading of 0.20bar, which it should being a baffle chamber.

Below are some photos of the valves and hopefully they will shed some light on what I believe is their way of operation

Here are the two valves side by side. The right side valve (black) is the inflation valve with its plunger, rubber diaphragm and 'control' spring. The left hand (red) valve is the relief valve with its plunger, rubber diaphragm but the spring is out of view as this valve works in the opposite way the inlet valve does.

Here is a closer look at the relief valve and notice the outer ring locating 'tabs'

Here's a close look at the dust cap and after measuring the cap it appears the central raised ring pushes onto the (white) relief valve to hold it closed above 0.20bar.
Also notice the caps outer ridges to grip onto the receiving locating 'tabs'

So unless the dust cap is pushed fully 'home' at its centre and then pushed 'home' at its outer locating rings the relief valve will not seat fully allowing inflation to 0.25bar to be maintained
Here's how the dust caps should look fitted correctly

I re-inflated my boat to 0.25bar following this procedure of the dust cap fitment and after 12 hours it maintains its pressure.
If I start to disturb the dust caps from their 'square' or fully 'home' position air starts to escape and will drop to 0.20bar and then stops.
The dust cap is easily removed by a flick of a finger nail so I believe it's designed to 'pop' off if the tubes receive a sudden impact, sudden air pressure influx or sudden heat increase causing air pressure increase with the diaphragm taking over to stabilise air pressure at 0.20bar.

This experiment was purely carried out to satisfy my inquisitive nature and learn about my boat with the hope of benefiting others that maybe experiencing inflation problems.

Paul

[philpot]

Most interesting Paul and thank you for that.

One small niggle in my mind is that it is possible that if the boat was inflated, pumping the front bow chamber first, as on most SIBs, could that upset the balance of the tubes as the Frib is inflated via main tubes first ----------------- doubt it, just a passing thought.

Phil

[harrison]

Hi Paul,
Thanks for posting data on your pressure test readings, most informative. I too found if you inflate with caps open the valves blew off at about .18 bar.
Below are the results of my tests, which were sent to F-Rib, and carried out over a two week period in an integral garage.The garage has a fairly constant temperature and used the same battery operated pump/gauge throughout (we have 3 gauges and all read within 10%) so am confident we were getting consistent readings.
The tests have been done with the overpressure valves in three different conditions - 1. Valve caps closed, 2. Valve caps open and 3. Valve caps closed with foam packer under (to exert slight pressure on valve). Results listed below;

Edit; (Apologies column tabs not working in post!!)

1. Valve Caps Closed

Pressure - All tubes inflated to .25 bar
Starboard Rear Front Port Rear
2hrs .17 .17 .18
24hrs .13 .14 .15
48hrs .11 .12 .13
72hrs .09 .11 .12
96hrs .03 .08 .11
120hrs .0 .06 .09

2. Valve Caps Open

Pressure - All tubes inflated to .25 bar
Starboard Rear Front Port Rear
2hrs .15 .15 .16
24hrs .13 .13 .13
48hrs .10 .11 .12
72hrs .05 .08 .11
96hrs 0 .07 .08
120hrs 0 .05 .06

3. Valve Caps Closed with Foam Under

Pressure - All tubes inflated to .25 bar
Starboard Rear Front Port Rear
2hrs .20 .20 .21
24hrs .17 .17 .18
48hrs .15 .15 .16
72hrs .10 .13 .14
96hrs .3 .10 .10
120hrs 0 .08 .09
144hrs 0 .05 .06
168hrs 0 .03 .04
192hrs 0 .02 .03

I also inflated the front tube to .05 bar with both rears left deflated (only very low pressure as to not damage baffles) - After 24 hrs the front tube read 0 bar !!

After initial inflation to .25 bar both valves blew off at around .18 bar.
While the different OP valve conditions did vary the rate of pressure drop, the end results after a few days are all similar - dramatic to total loss of pressure in all tubes.
I could understand the rear tubes going down if the OP valves are faulty/dirty etc, but I cannot understand why the front tube goes down also. OK, as the baffles deflect to the rear, the pressure will drop in equilibrium to a point, but nowhere near the loss measured Where is safety factor if a tube is punctured? This could be a major concern as the baffles didn't appear to be airtight.

One OP valve even had clear silicon sealant between the fitting and tube - didn't seem right that a manufacturer should be using this around a fitting, although I notice traces of sealant also on your pics.
I soaped the tubes all over and couldn't see any leaks/bubbles apart from round the OP valves. Bubbles were produced not only from the valve centre, around the cap, but also from the back of the valve body next to the tube. Indicating the valve was not correctly sealed to the tubes.

Silicon on one?

But not on the other

Leaking around perimeter/tube. Cap closed

Leaking from both with caps open

Having looked at your pics again I've noticed the valve bodies are different. At first I thought they were just a different colour. Perhaps yours are an improved design with a larger diameter valve!

Sorry for long/boring post but thought worthwhile indicating sort of pressure loss experienced on this boat.

harrison

[Paul]

Harrison

Many thanks for this very detailed series of events investigating your pressure loss, it's all very interesting as an owner
Yes as you say the valves do appear to be different and the central valve body on mine seems larger in diameter to yours
I've just gone and rechecked the pressures again tonight and they're all holding at 0.25bar
From your results it appears the valves were malfunctioning/not sealed against the tube
In the interest of experimentation I've just connected the gauge to the front chamber and fully deflated the rear tubes to see what happens
Although the gauge reads zero the front chamber is still inflated and feels to me to be reasonably firm and would provide buoyancy for sure.
It's difficult to gauge 'firm' so I asked my 15 year old lad of about 10 stone to stand on the tubes and I was surprised how firm the tubes were at a zero reading and this would apply to most inflatable boats

for all the info
Paul