New 6 meter sib and problems - Page 2

spainman · 16 May 2022, 21:50

If I stand on my tubes they flex.

I do not put so much pressure in because it is very hot and I worry that they will explote.

the owners manuel tell 0,25 bar tubes 0.30 bar inflatable keel.

The keel i put it all time to 0.30 bar but the tubes never. they are so big so i do not saw it neccesary

Could this be the realy problem ?

TmMorris · 17 May 2022, 05:47

It will mean that you do t have the intended rigidity so when the structure is being pushed from behind by the engine and the drag of the water is pushing it back the other way you're going to get more flex and deformation in the hull. That will always have an impact on performance. Whether it is the sole cause of your particular issue can easily be tested.

It may also be that the pressure in your keel falls once it's put in the cooler water after inflating in the sun?

Can't be any harm in buying a pressure gauge and checking the keel and tube pressures while on the water, possibly needing to add air to the keel while letting air out of the hull but checking whether this gets you those extra few knots.

Fenlander · 17 May 2022, 08:32

>>>I do not put so much pressure in because it is very hot and I worry that they will explote.... Could this be the realy problem ?

Having a 3.5m SIB low on pressure is bad enough but a 6m one is unthinkable. The transom end powered by that heavy 60hp is probably acting independently of the bow end. As TM says if you haven't already get a good gauge you trust. Inflate to maximum pressure and then recheck adding air if needed after five minutes on the water. Then give it a test. If it performs properly get a repair shop to fit pressure release valves to each chamber so you can safely keep it at the full proper pressure in future.

Steve509926 · 17 May 2022, 14:56

Quote:

Originally Posted by 909

You should be able to stand on your tubes with very little give.

Not exactly scientific! If my 60kg wife stands on the tubes when inflated to 3psi there is won't be any give, but the tubes would be under inflated.

Personally I'd use a pressure gauge.

jeffstevens763@g · 17 May 2022, 18:47

Found this might help the OP

https://www.nrs.com/learn/raft-overi...amage-from-sun

I’ve seen somewhere a manufacturer making a pressure relief valve that fits on the existing valve some research needed

jeffstevens763@g · 17 May 2022, 20:10

This could be a god send use for pumping up to 3 psi then have a end cap to seal the inlet and use as a PRV in the bow chamber which is pumped up first.

https://apaddleinmypack.files.wordpr...02/prv-opv.jpg

spainman · 19 May 2022, 19:58

So here my Reply to the Test of Today with 2 mecanics.

I inflate the Tubes and keel to the pressure it indicate also testes with special gauge I have.

after this we make a testdrive with the mecanics
( cavitation plate is a bit lower as the transom End down )

With 3 of us testing and the boat to not work well,

Slowly acelerating up to 4000 rpm it works +- after this problems with air, or whatever it is. But RPM goes up like without resistance and boat do not work.

TEST 2. change of props, same result, nothing better nothing worser.

Test 3 puting motor One Hole up now it was cavitation plate on same level as end of transom down.

All worser, not posible to acelerate, we change props and nothing.

Mecanics looking if the Prop and Cavitation plate has been in the water or out and taking air.

At the end the 2 mecanics call other mecanics who maybe could help and one told that the motor must come lower, because the hull or inflatable keel is making some water turbulance etc.

So my last Strike is cutting a bit the transom and make motor still lower.

The mecanics told this is the last option, because the boat is not drive able.
and it is new. The Dealer where I have bought the boat just give me stupid answers and will not help. New Boat it must work.

I am very dissapointed because a SIP in 6 meter class was always my dream
and I have asked Zodiac for a price of a new one but was 4 times more as what a payed for this shit of chines boat.

Maybe somebody can confirm that cutting out the Transom and lower engine it will workd or some idea.

Thank you guys,

Arthur

jeffstevens763@g · 19 May 2022, 20:13

Arthur don’t cut the transom until you get some pictures posted so we can look for problems you might have. also of the hull if the keel is out of centre you will get problems. Make sure the props are ok and the hub is not spinning, I said that the props aren’t allowing you to get maximum rpm so it will only achieve a certain rpm giving the stall in speed you mention. IMO the boat just needs setting up properly with the correct prop.

spainman · 20 May 2022, 06:44

Thank you for your answer.

Keel is perfect in his position.

2 Props tested, I do not know which prop to test more.

MY Opinion is, That maybe the boat runs correct with a lot of load on it so than it is a bit heavier and the transom more in the water.
I do not know, it makes me crazy this sib.

TmMorris · 20 May 2022, 07:00

Can you return it under your EU consumer rights? It's almost certainly the boat to blame not the engine and it may be that it's design means it will never work as intended?

Pikey Dave · 20 May 2022, 08:11

As soon as you cut the transom, you can say good bye to any chance of recourse with the retailer under warranty. You’d be stuck with it.

spainman · 20 May 2022, 08:38

The problem is,
After 8 month I have got it, anybody think that somebody will return me something or give a new Boat ?

I got it over 4 month packaged without fitting the motor, because problems of Covid etc.

lightning · 20 May 2022, 16:17

As above, could unfortunately be just a cheap Chinese boat with poor hull design.

ln the end if you are still not happy, maybe your only option to sell the boat and buy a better one. lf you cut the transom, and it still doesn't work, the boat will be almost worthless.

ls there any chance you could borrow a different engine to try, long shaft maybe?

GARYSHORT · 20 May 2022, 16:25

As others have said, you are underpowered. You really need a 90hp motor.

Fenlander · 20 May 2022, 18:03

Not sure how 90hp will help if a 60hp is already massively exposing the limitations of the hull design. Could be better with a lightish 40hp.

TmMorris · 20 May 2022, 18:29

Quote:

Originally Posted by Fenlander

Not sure how 90hp will help if a 60hp is already massively exposing the limitations of the hull design. Could be better with a lightish 40hp.

It does seem like it's the boat rather than engine. Rather than cutting the transom, I would think it's worth trying a small outboard and a bigger one just to confirm things but ultimately, it may just sadly be that the design can't cope with any more than 20 knots?

Steve509926 · 20 May 2022, 18:48

Quote:

Originally Posted by spainman

The problem is,
After 8 month I have got it, anybody think that somebody will return me something or give a new Boat ?

I got it over 4 month packaged without fitting the motor, because problems of Covid etc.

Was it a direct import from China, an internet purchase (ie: Alibaba) or from a retailer in Spain. If its the later you will be protected under EU consumer law "If" and its a big "If" the SIB is not performing to specification. Get in touch with the retailer and ask for their help/advice.

Today I stood next to a 6 meter RIB, it's big! It's very big! I just can't get my head around a 6 metre SIB not flexing so much that it will act like a wet mattress being pushed through the water.

I really do hope you purchased from a reputable retailer and they help you to get things sorted.

Steve509926 · 20 May 2022, 22:02

One thing that hasn't yet been mentioned is the floor.
I'm assuming it is an aluminium floor, has it been correctly assembled? Is the floor flexing?

spainman · 20 May 2022, 22:45

The floor is correctly fitted.

The only think I have done aditional is put 2 stringers as an reforcement from the Last Floorplate to the up side of the Transom

To have the transom stronger just in case, I see it on some older Sibs.

But I can not imagine that this has en influance of the boat.

Fenlander · 21 May 2022, 08:42

>>> I just can't get my head around a 6 metre SIB not flexing so much that it will act like a wet mattress being pushed through the water.

That's very much my feeling right through this thread. The Zodiac commercial/military SIBs of this size weigh getting on for another 250lbs over a 6m leisure use SIB to support use of large outboards. The Excel 5.9m I note is only rated to 30hp. So I do wonder if the maker of the OP's SIB has just pulled an allowed outboard power out of the air to look impressive.

I just have a gut feeling his 252lb 60hp is part of the problem. I could imagine it pinning the transom end to the water and the rest of the SIB towards the bow suffering some significant longitudinal and torsional deflection... not to mention that length of flappy rubber floor deforming under load.