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Old 24 September 2011, 10:28   #1
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Rib lose control at 30knots

Hi all i am new here and i donít know if this is the right place to ask you if you could help me with my problem.
I own a maxxon rib 4.80mtr and powered with a mercury 60hp 4 stroke all bought new this year when i try to reach high speed the rib at 30knots lose control and start swinging from rear and it becomes very danger and will have to slow down. What i have been told to do is to rise the outboard but this didnít help. some told me it is over power but i donít think so. Total weight of the rib is approximately 400kg. What do you think ?.Thanks Jason
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Old 24 September 2011, 10:42   #2
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Swinging from the rear? Or rocking violently from side to side?

From the lead-up to the problem, it sounds like a case of chine walking. Do a search on this site, and you'll find a substantial amount of information on what it is.

jky
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Old 24 September 2011, 12:52   #3
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yes that is the right description. thanks for your help
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Old 26 September 2011, 06:20   #4
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Hi and thanks for your information as it was very helpful. Last Saturday i went for a ride with the rib and tried to see if the chine walking was less after i raised the motor by 1” and what i noticed that when i was at W.O.T at about 32knots and was steering to starboard the rib was very stable and good running trim all down but as i steering straight it to trim it out it started cine walking violently. Now i have to ask you what is the best way to try eliminating the chine walking i have read a lot of things here that can cause chine walking. What i have noticed on my steering that it has a little clearance from right to left it has about Ĺ” on both sides. Will this affect the chine walking. Do i have gust to add weight or install a jack plate or hydraulic steering. Thanks to you all again and your help will be appreciated. Jason
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Old 26 September 2011, 07:28   #5
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Quote:
Originally Posted by Jason calleja View Post
What i have noticed on my steering that it has a little clearance from right to left it has about ĹĒ on both sides. Will this affect the chine walking. Do i have gust to add weight or install a jack plate or hydraulic steering. Thanks to you all again and your help will be appreciated. Jason
1/2" will make it difficult to stop the chine walking - take out the play and the boat will behave much better. Hydraulic steering can also have play if not maintained properly but is generally considered to be better other than by the purists.
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Old 26 September 2011, 08:28   #6
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I see its only a 60hp outboard. Is it power trim or not? Would suggest the trim angle is too high so perhaps try 1 hole "in" if manual or just trim down a bit if power trim.
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Old 26 September 2011, 09:45   #7
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32 kn is a good speed for a hull of that size. I would say you are trying to squeeze too much out from the hull
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Old 26 September 2011, 11:20   #8
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32 kn is a good speed for a hull of that size. I would say you are trying to squeeze too much out from the hull
Agree. Trimmed all the way down you are keeping hull in the water, raising the trim is raising the bow. With less wtted surface the chine walking starts. 30knts is about all that hull is going to do with stability.
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Old 26 September 2011, 13:26   #9
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Yes it is power trim and when it starts chine walk it is trimmed all down and the other thing is i know another person that has same rib with same outboard it is identical with mine and he is doing 40knots with it and had never chine walked and my brother has a 14ft rib that weights 250kg including outboard and it has 50hp tldi on it and never had problems like this i can’t understand what does my rib could have i will try eliminate steering clearance then i will see if it will reduce the chine walking. Thanks all for your help. Jason
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Old 26 September 2011, 14:25   #10
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trimmed in? at full speed? Why?
try trimming out gradually as you speed up-you are trying the equivalent of pushing a weathervane the wrong way into the wind and obviously if the pressure one side of the bow is stronger than the other it will try to whip round. Get the bow up.. with the limiting factors being either the prop will draw air and the motor will over rev OR the boat will become unstable again. Our 4m searider was good for well into the thirties with no problems...our 4.3 humber assault was also ok with the proviso it needed a bag of sand in the front for balance-but both still had to be trimmed out.
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Old 26 September 2011, 16:32   #11
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Might be worth having a chat to the dealer or factory as it is a new boat so shouldn't have any steering or mount wear and they must have encountered the problem before.

Did I read it right, you raised the engine 1 inch on the transom? Did this make the chine walking better or worse? How about top speed?

As for trimming, trim in (propellor closest to the transom) till on the plane, then as suggested start trimming out and you will feel the boat going faster up to a point when the prop starts to slip. At this point bring it back in a touch.

Play in the steering makes it worse, so tighter steering will make it better but probably not eliminate it.

If your trim and engine height is right and your engine is centred, I think balance is your only other tool.

Stopped in the water with you sitting in the driving position, have a look at the port to starboard balance. Is it leaning to one side? If not, play around with front to rear balance.
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Old 27 September 2011, 09:46   #12
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Yes this morning went to the dealer and told him that the steering clearance is normal and he told me too that with the 60hp it is a good speed for a rib that i don’t agree with him i thing that i could have more from it . yes i raised the engine 1” and i think that it was better what i will try to do is to eliminate all the steering clearance as i am suspecting that it is all the causing the chine walking. I will try to buy a steering helm that have friction adjustment then will see what happened. Thanks all
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Old 27 September 2011, 10:38   #13
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before you go buying things get out there and play with the trim. We have had any number of folk here with their boats that thought it was an on/off sorta switch. By trimming up at speed all their boating woes disappeared. I suspect it will all come right for you when you have been out there and done it for yourself.

Quote:
engine is centred
you would be better with the engine off set 1/1.5 inch to the right to counteract prop effect
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Old 28 September 2011, 03:16   #14
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you would be better with the engine off set 1/1.5 inch to the right to counteract prop effect
I have a similar size/ weight / HP and mine's dead centre - no chine walk or biased steering offset on mine.......



If your engine is fully down, I doubt it is even chine walking - for what it's worth as an experiment years ago I had an SR4 with a 25 on the back, and made it do exactly what you describe by putting the trim pin (no PT on that!) at the lowest hole. Opening the throttle felt like it was trying to do submarine impersonations, the stern lifted and it wobbled to & fro as the bow tried to go underwater!

Before you start mucking about & / or spending buckets of cash, play with the trim! Eek it up slowly until it starts to ventilate (cavitate) then notch it back down a tiny bit. You'll hear the engine star to "sing" as it hits the optimum trim position. There is also an argument for raising the stop pin up a couple of holes to prevent this happening accidentally if you are not paying attention. (mine is 3 holes up from the bottom, for what it's worth)

Also here is a description of chinewalking I wrote recently: http://www.rib.net/forum/f8/chine-wa...tml#post421932 (post #8)
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Old 28 September 2011, 05:46   #15
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yes i read your description on chine walking and it helped me a lot and no it is not trying to go down but i think it is all coming from the steering. i will try to check the helm and if necessary will replace it as for me there is not so much speed that the rib is out completely on the keel. do you know what tipe of helm can i use that has an adjustmanet to eliminate the loose. thanks jason
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Old 28 September 2011, 05:51   #16
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I was borrowing a friend's Valiant V490 the other weekend and found that with only one up it chine walked badly at anything over 30knots with just me in the boat - however it was a lot more stable with a few more people on board.
I'd try fitting a hydrofoil to the outboard - can throughly recommend the StingRay Stealth.
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Old 28 September 2011, 06:55   #17
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The Hull in the V490 is the same as mine dr 490. I would be fearfull in mine at 30 kn. It would need to be very lightly loaded to achieve this speed. I usually have 30-40 kg of lead in the bow locker along with 60 lt of fuel and assorted fittings this has reduced its max speed to 26 - 27 kn. The boat is comfortable in most sea states at 18 -20 kn it gets lively at 23/24 kn. It can carry a load with ease and handles better with a load.

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Old 28 September 2011, 12:30   #18
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Quote:
Before you start mucking about & / or spending buckets of cash, play with the trim
yep-think thats what I said
Quote:
If your engine is fully down, I doubt it is even chine walking
exactly thats why we have all said to trim it up
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no chine walk or biased steering offset on mine
no not for chine walking but for balance and to counteract any pull to one side-I would and do always offset but if yours is fine in t'middle then thats all good

Quote:
I usually have 30-40 kg of lead in the bow locker
I suspect that may well be his most useful tip yet once he gets the trim sorted out. Our little 4.3m humber assault with a 50 merc four stroke was well overpowered and evil at WOT. A bag of sand in the front both cushioned the anchor and stopped chine walking when the little bugga was at full chat
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Old 29 September 2011, 12:02   #19
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Old 11 October 2011, 13:16   #20
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I have tried the rib after done settings to steering friction the ride was more comfortable at full trim out it was like flying on the waves but still chine walked. Now when you sad to add a sand bag for weight will it have to be on the front or if i add weight at the transom will stop chine walk?
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