Rib leaning during power up

ChrisB123 · 13 September 2006, 15:44

Have noticed that the rib leans to the left when i excelerate. Is there an adjustment for this?

Chris B

havener · 13 September 2006, 17:08

What's your setup - seating, etc ?

Applying power will highlight any poor weight distribution issues.

Alternatively (assuming you're running an outboard not inboard) check the alignments of the steering.

And check tube inflation on the aft quarter opposite to the direction of pull.

Hope this helps.

wavecrosschris · 13 September 2006, 19:26

What you are experiencing is paddle wheel effect or propwalk - similar to torque steer on a car.

heres all about it as its too long for me to explain...

http://en.wikipedia.org/wiki/Propeller_walk

Two engines sort your problem out - as does duoprops (I think invented as it is now by Volvopenta - not 100% sure tho) - but it was originally invented to keep tordepos straight so they hit their target in the water!! - Basically a set of contra-rotating props on one outdrive shaft counteract the prop kick and keep the boat straight...

heres about duprops...

http://www.marinepartsexpress.com/promo/duoprop.html

Any boat with one engine and one prop will propwalk - sometimes (in mooring up) you use it to your advantage - other times, when trying to get the stern in its a right bas**rd!

Hope this helps!

Regards

Chris

codprawn · 13 September 2006, 19:45

Try trim tabs.

ChrisB123 · 13 September 2006, 19:51

Thanks for the info.

I have only had the rib a few months. Its a Humber 6.3mtr Ocean Pro with a 150 Evinrude 2 Stroke.

Does this mean my combination is wrong and i may not be able to sort it?

Chris

wavecrosschris · 13 September 2006, 20:09

nooo, it doesn't mean anything! - as above trim tabs will probably help - try some smart tabs maybe? (they are activated by preasure from the water pushing up, so one will dig in further than the other) - but it is totally natural reaction from the boat!

codprawn · 13 September 2006, 20:33

It is perfectly normal. Most people soon get used to it but if you have a very pronounced lean then you could try trim tabs. For a boat your size the new Volvo QLs would be great - the easiest to fit quite cheap. I have a pair but haven't fitted them yet!!!

http://www.foreandaftmarine.com/VO-QL3841717.htm

Most British Volvo dealers can order for you but most have never heard of them!!!

Obviously to counteract lean you use the tab on one side more than the other but extra drag will slow you down.

BogMonster · 13 September 2006, 21:01

Do most boats suffer from this then? I just ask as my Humber doesn't seem to at all. From a standing (floating?) start you can open the throttle to WOT and accelerate to full speed and you don't need any steering input worth mentioning as the speed rises, and nor does the boat seem to lean at all, not even a little bit. I've been in other boats though, that feel like they are going to sink when you open up the taps. Am I just lucky? No trim tabs or bling props or anything... just an ordinary eggwhisk on the back spinning a bog standard prop.

Ian Sharlot · 13 September 2006, 21:05

Is your engine off set and if so by how much

Biggles · 13 September 2006, 21:33

Quote:

Originally Posted by BogMonster

Do most boats suffer from this then? I just ask as my Humber doesn't seem to at all. From a standing (floating?) start you can open the throttle to WOT and accelerate to full speed and you don't need any steering input worth mentioning as the speed rises, and nor does the boat seem to lean at all, not even a little bit. I've been in other boats though, that feel like they are going to sink when you open up the taps. Am I just lucky? No trim tabs or bling props or anything... just an ordinary eggwhisk on the back spinning a bog standard prop.

My boat seems the same.

codprawn · 13 September 2006, 21:59

Quote:

Originally Posted by Cracker

Is your engine off set and if so by how much

Yup many single engines are offset - mine is by a noticable amount.

Makes me wonder why there has only ever been 1 duoprop outboard(I think) - the Yamaha vmax 150.

BogMonster · 13 September 2006, 22:31

I would have thought a duoprop would be horrible with the downstream prop suffering from all sorts of odd turbulence effects off the trailing edges of the upstream prop, but I guess they work if people make them!

I've never measured my offset and its cold outside and I am sat down with a bottle of something so I'm not going to go and do it now, another day maybe

wavecrosschris · 13 September 2006, 23:10

I don't notice prop steer on mine either - but let it run on its own at high speed for long enough on a calm day and you will notice a gentle curve or the boat bank off to one side - not sure why it is worse on some boats that on others - but guess the torque at the prop has a lot to do with it - how much power you have and how much hull is in the wet stuff!

found the bit about Volvopenta inventing the duoprop...they say...

When Volvo Penta introduced the patented Duoprop in 1982, it was the biggest event in boating since the propeller was invented. Twin counter rotating propellers bite hard to produce unparalleled thrust, straight and true tracking – even in reverse – plus faster acceleration on the plane.

The counter rotating twin propellers eliminates the lateral forces existing in conventional single prop sterndrives. That means the engine’s energy and power is concentrated on driving the boat forward – not sideways

Straight tracking
Duoprop tracks straight. Check over the transom of any Duoprop powered boat. The evidence of cleaner, unruffled delivery of power is there in the wake.

Faster acceleration
Duoprop provides up to 30 % faster acceleration and produces a top speed some 5 % faster than any conventional single propeller system – without increasing the fuel consumption. At partial load you can expect between 10 and 12 % lower fuel consumption.

Faster planing
Better grip in the water means getting up and onto the plane faster. And staying there at lower revs.

Handling is better too
Whether at speed, round the buoys or when docking in a crowed marina. The grip is there – even when making sharp turns at high speeds. Duoprop also reduces the boats tendency to roll.

Lower vibration and noise levels
Duoprop produces lower vibration and noise levels due to the fact that the shock pulses are distributed over more blades. With its counter rotating propellers it’s almost cavitation free.

They don't mention its twice the cost when you hit something though!!!

Cypman · 14 September 2006, 03:29

Engine offset will often cure this problem, as will careful location of heavy items ie battery, spare fuel etc, A slightly offset console will also solve the problem.

I have the same boat as you with a Suzuki DF140 on the back. My engine is offset 1.5ins to the right and the dual console is 2ins to the right, the boat is well balanced as a result. However, I would not suggest you should try relocating your engine and/or console at this stage unless it is an easy fix but just live with the issue.

LURCHER · 14 September 2006, 15:03

I had the same with my Humber , a pronounced list when powering up , it appears that the engine was not fitted vertically by the previous owner so under power the engine made itself vertical and caused the boat to list. We had a new alloy plate fabricated to realign the engine and all is well now .The reason for the plate was that the transom had been hacked about to accomadate a short shaft engine in the past and so many holes drilled .Hope this helps .

jwalker · 18 September 2006, 14:52

Quote:

Originally Posted by codprawn

...the new Volvo QLs would be great ..........I have a pair but haven't fitted them yet!!!