lean to port and Chinewalking on a Humber Ocean Pro 6.3

Ferdi · 29 March 2013, 14:49

Hello,
I recently bought a used Humber OceanPro 6.3 with an E-TEC 200HO in Germany, but boat (named StormChaser) ran in England until 2010.
First testruns on river danube at freezing temps were very successfull and made me a happy Humber owner.
The boat/motor combination is incredible, the performance is outstanding.

But, some things I am not familiar with, I noticed.

1) going fast, with empty boat and me alone, the boat has a little leaning to port (left) side (driver/me is right, batterie, oil tank, auxiliary engine ( 5hp mariner, 20 kg) are left.
I suppose, with a second person sitting on left side, this leaning to port will even be more

2) going really fast - more than 83-84 km/h (45 KN) and trimming motor our at WOT it gets a real bad Chinewalking, which only can be stopped by reducing rpms and speed.
With 21" Cyclone 4-blade prop max speed at WOT and about 5900 RPM is about 90 km/h (48-49 knots), but only for seconds because of too small eggs ;-).
I still have a 24" Raker (3 blades), which maybe a little to hight pitched, but will see how this will work.

3) engine is mounted offset to the right (starbord) some centimeters (maybe 1,5-2")

I have alreaday read here that some english RIB manufactures recommend offset mounting of outboards, and that many of you here have their engines mounted offset.
But, whats the deeper reason for this offset mounting ?
I am not very familiar with english RIBs, but this offset mountig is not common with italian RIBs, even they are used with the same outboards ?

PS: by the way, unfortunatly I am not able to change my profile to the new boat/motor. after saving the changes the old entries are still there.

C2 RIBS · 29 March 2013, 16:23

First thoughts on port lean may be a trim issue at speed, try raising engine trim higher slowly and see what effect this has at each speed

Cypman · 29 March 2013, 19:00

Having rigged my own Humber Ocean Pro 6.3m, albeit with only a Suzuki DF140 outboard, I would say that a 2in offset is the minimum you require for a 200HP donk.
In addition, I offset my console 2in to the right so that the boat ran "more level" when I was on my own. The Ocean Pro is a great hull but is sensitive to lateral trim, the lean is caused by the prop torque allied to a slim hull.
In order to correct your trim I would suggest one or more of the following:-
-Move console 2in to the right
-Transfer battery, auxilliary etc, etc to the right hand side of the boat
-Fit trim tabs (will cure all your problems !!)
Finally, the vertical position of the engine is fairly critical, the cavitation plate needs to be circa 1in above the keel when the leg is fully down.
I hope this information is of some use, 200HP on a 6.3m Ocean Pro is some rig.

RIB-Teccie · 29 March 2013, 19:59

Agree with that, but raise the engine so cav plate is above hull by 1" first, it may just be an easy fix.

RIB-Teccie · 29 March 2013, 20:49

Just looked at the picture of your RIB. Is there too much weight Aft? The sponsons aft look low in the water and the bow looks too high out of it.

Cypman · 29 March 2013, 21:04

The 200HP outboard is quite a weight on this hull. Nonetheless, Ocean Pros tend to sit with the rear end of the tubes in the water.
Having rigged a number of Humber RIBs and operated others, I am of the opinion that consoles and seats are often located too far aft. However, fore/aft trim is not so critical and can usually be sorted by careful engine trim.

Ferdi · 29 March 2013, 21:34

thanks guys, will try your suggestions as long as I can do and realize them.

yes, motor seems quite heavy for the boat, the smaller 200 HP E-TEC would fit better, I think, even the boat drives really well, until 80 km/h. just with a little lean to left.
and the motor is unbelievable. the boat really jumps out of the water :-) .

whats new for me is, that a hull is so sensitive for motor mount and weight distribution.
I am used to italian RIBs and they are much less sensitive in this respect. ok, most or many of them have the ends of the tubes in water, but my former Zar53 had them also out.
and they all have motor mounted centered.

maybe I can drive without aux, but did not want it the first runs on danube, which has quite a lot current in my sector and I did not want to end without advance with a new to me motor in front of a carrier ship.
I also can distribute weight of the storage under the seats more to the right.
All together will solve the problem, I am sure, if you guys drive it to your satisfaction.

So, it is really so that the motors on these hulls have to be mounted offset ?

lets say load distribution during driving is perfectly centered and well balanced.
what would happen if motor would be mounted also centered on this hull ?
would it lean to the right or to the left ?
And which lean does motormount to the right correct ?

Cypman · 29 March 2013, 22:58

My understanding for the lean to the left is that when this boat is on the plane the tubes are completely clear of the water so there is no lateral support for the hull (also no additional drag!) so the torque effect of the outboard has a greater effect.
I am sure someone will tell me if I am wrong !!

If you go to the "search" facility and enter "Lemon Zest" you will see photos of my old boat, now in Iceland, which clearly show how she sits at rest and also how she rides at speed (only 40kts !!).

Ferdi · 31 March 2013, 11:14

thanks again for your answers.

But, has someone also an answer to my following question ?

lets say load distribution during driving is perfectly centered and well balanced.
what would happen if motor would be mounted also centered on this hull ?
would it lean to the right or to the left ?
And which lean does motormount to the right correct ?

alystra · 31 March 2013, 12:04

Quote:

Originally Posted by Ferdi

thanks again for your answers.

But, has someone also an answer to my following question ?

lets say load distribution during driving is perfectly centered and well balanced.
what would happen if motor would be mounted also centered on this hull ?
would it lean to the right or to the left ?
And which lean does motormount to the right correct ?

If the boat is driving perfectly level with the motor offset to starboard, then if the motor is centred, the boat will lean to port (left) when driving. This is because the propeller thrust has a sideways component as well as a forwards component.

The motormount to the right corrects the lean to the left when driving. When you stop, the boat will lean a little to the right because of the engine offset.

Certainly, on the Humber Destroyer, the factory installs engines with an offset to the right (starboard). They build these boats and are pioneers in RIB building. If they install engines with an offset, I would accept their expertise.

gotchiguy · 31 March 2013, 15:46

Quote:

Originally Posted by Ferdi

thanks again for your answers.

But, has someone also an answer to my following question ?

lets say load distribution during driving is perfectly centered and well balanced.
what would happen if motor would be mounted also centered on this hull ?
would it lean to the right or to the left ?
And which lean does motormount to the right correct ?

I would suggest that much easier for you than moving the console will be to fit trim tabs. "Chris" on here has fitted two sets but I can't seem to find his threads. "Erin" detailed his in the link below. It would allow you to lower the tab on the left hand side which raises up that side by creating more lift at the stern. On the canals it will also enable you to plane at lower speeds which I imagine will sometimes be useful! Loading evenly matters much less because the tabs can be used to counteract any imbalance.
http://www.rib.net/forum/f36/la-frette-tabd-47468.html

Erin · 31 March 2013, 20:59

Interestingly, my boat leans to port when underway even though the engine is mounted about 30mm to starboard. It also always dries out port to I suspect the layup is not perfectly balanced. Having the battery to port may not help. It has never been a problem running with a slight lean to port, but I can now correct that with tabs. I also raised my engine but didn't notice any appreciable difference.

Chris · 31 March 2013, 21:21

Prop type can have a big and surprising impact on boat trim. When we first bought pigs ear it had a laser 2 prop on the Honda. When we switched to a large diameter Mirage prop the difference was huge. The boat ran flat and even when coming out of the water it has no tendency to twist to port.

Balance will help when stationery or at low speeds and moving the battery to starboard would help Erin but once you are are planing the torque affect of the prop is what affects the trim.

I would try some different props before changing anything.

Barfly · 31 March 2013, 22:17

Port lean can also having to do with current and or wind direction

I also have it 'sometimes' on the scorp - deep v ribs are sensitive to that

Ferdi · 31 March 2013, 22:48

thank you guys, good hints .

your answers help me to understand the new for me deep V hulls much better.

yes, the sensitivity is new to me

HUMBER P4VWL · 31 March 2013, 23:40

Our 6.3 op leans to port when trimmed in, as we trim out it balances up to neutral. Ours too sits v low at the rear, it's just the design. Freeboard on transom is excellent though. Tubes drag slightly in water but gives great stability.

Where are your tanks? We have 140L in console. That should stop chine walking. Ours only just chine walked at 52mph... It's v rare though, we need to be v lightly loaded with no kit on.

The 200 must fly.

willk · 31 March 2013, 23:50

Quote:

Originally Posted by Barfly

Port lean can also having to do with current and or wind direction

I also have it 'sometimes' on the scorp - deep v ribs are sensitive to that

Yes, boats with a lot of "windage" (e.g. a Cabin RIB) will often heel INTO a cross wind, which isn't what you might expect...

gotchiguy · 01 April 2013, 00:12

Quote:

Originally Posted by willk

Yes, boats with a lot of "windage" (e.g. a Cabin RIB) will often heel INTO a cross wind, which isn't what you might expect...

Yes that is odd. How come?

willk · 01 April 2013, 00:15

Quote:

Originally Posted by gotchiguy

Yes that is odd. How come?

Damned if I know why, but it does. I've noticed it while helming a twin rig running counter-rotating props. I'm sure Phyzzix has the answer...

apples · 01 April 2013, 08:13

Quote:

Originally Posted by HUMBER P4VWL

Our 6.3 op leans to port when trimmed in, as we trim out it balances up to neutral. Ours too sits v low at the rear, it's just the design. Freeboard on transom is excellent though. Tubes drag slightly in water but gives great stability.

Where are your tanks? We have 140L in console. That should stop chine walking. Ours only just chine walked at 52mph... It's v rare though, we need to be v lightly loaded with no kit on.

The 200 must fly.

'we need to be very lightly loaded WITH NO KIT ON'

not a problem in present weather conditions then