Another sad accident.

[Mr-d]

Just had a look at them propguard things, they are £150! for a piece of plastic!

Oh, i think i am wrong but dont quite understand, so i have decided to animate the situation of MOB on the left hand side.

Steering Left
Steering Right

Both situations appear to be alright... but in practice its probably very very different.

Oi, no snickering there at the back, i did my best at art!

[roohairy]

Sorry, steering away from the casualty is (dangerously) wrong. Remember that a boat does not pivot about the engine, but rather about a point approximately 1/4 to 1/3 of it's length from the bow. As forward speed increases the turning point moves further forward and at high planing speeds may well move outside the boat. Going astern will make it move aft.
Next time you're out have you boat completely stopped, put a fender alongside right aft and try both manoevres!

[BrendanS]

Agree. If anyone goes overboard, stay straight ahead, then turn. Not really a worry, as no one's reactions times are that goood.

Last thing you want is prop getting near person in water

[Observer]

I think the original post did say "man overboard at high speed".

If I remember correctly from my PB level 2 (many years ago), the 'Williamson turn' calls for a 90 degrees turn AWAY from the MOB side, count to three then 270 degrees turn in the opposite direction which brings you back with the MOB dead ahead. Not sure why turning away is recommended - possibly allows better view of the MOB as you execute the turn?

At slow speed I agree must turn toward the MOB to get the prop clear.

[SteveHall]

Originally Posted by Observer

I think the original post did say "man overboard at high speed".

90 degrees turn AWAY from the MOB side,

I may be wrong but are you going to create a nice big wave when you turn away that will go straight for the MOB?

[Observer]

Originally Posted by SteveHall

I may be wrong but are you going to create a nice big wave when you turn away that will go straight for the MOB?

Not sure really - the MOB will be some distance back by the time the helmsman has reacted and started a turn so any wash will be the same either way the boat turns.

I have picked up the following from the web:

The Williamson Turn is a maneuver used to bring a ship or boat back to a point it previously passed through, often for the purpose of recovering a man overboard.

The Williamson Turn is most appropriate if the point can be allowed to go (or already has gone) out of sight, but is still relatively near. For other situations, an Anderson turn or a Scharnow turn might be more appropriate.

Put the rudder over full.
If in response to a man overboard, put the rudder toward the person (e.g., if the person fell over the starboard side, put the rudder over full to starboard).
After deviating from the original course by about 60 degrees, shift the rudder full to the opposite side.
When heading about 20 degrees short of the reciprocal, put the rudder amidships so that vessel will turn onto the reciprocal course.
Bring the vessel upwind of the person, stop the vessel in the water with the person along-side, well forward of the propellers
If dealing with a man overboard, always bring the vessel upwind of the person. Stop the vessel in the water with the person well forward of the propellers.

Retrieved from "http://en.wikipedia.org/wiki/Williamson_turn"

Thnking about this, the Williamson turn was invented for ships where it is feasible a turn could be commenced while the MOB is still 'alongside' part of the ship. In that case, a turn towards the MOB must be correct. In a small boat at high speed I think direction of turn is academic but I suppose it is better to develop an instinct to always swing the stern away from a MOB.

[Paul Glatzel]

Man overboard

If someone goes overboard:

• As they fall, turn the helm immediately towards the side they fell. This moves the prop away from them. Don’t do this so violently that you loose someone else overboard too! (NB: MOB is not soley a high speed issue, whilst turning towards the casualty will make no difference at high speed at slow speed it it pushes the rear end away reducing the chances of them being pulled towards the prop(s). By always turning toward the casualty it becomes a natural reaction, when it happens you won't have time to think in the first second or two so your reaction should be instinctive.
• Alert the rest of the crew by shouting ‘man overboard’. Instruct one person to point at the man overboard and continue to do so until the rescue is competed. If it is feasible and you are close to them, throw them a lifebuoy even if they have a lifejacket on – they will take comfort from holding onto it.
• Take power off entirely and effect a slow turn and return towards the casualty.

This then leads towards the assessment of the casualty, your options and your best method of approach - NB: ONLY consider wind, tide/current is not relevant as the casualty is (usually) moving with the tide as the boat is.

A slight wave will be the least of of the casualties concerns so don't worry too much re that

Williamson turn

This technique involves executing a perfect 180º turn to head back along your path to search for the casualty. It is particularly effective for larger craft and where restricted visibility (eg at night) means that you need to be sure you are heading in the right direction.

• Add 60º to your compass heading and turn to starboard to that heading.
• Once on that heading, turn the wheel an equal amount to port (ie however many full or partial rotations of the wheel you previously turned to starboard).
• When the heading is the reciprocal of the original heading (ie +/- 180º) or you are running down your own wake, straighten up and commence the search.


Paul

[Manos]

I thought I'll bring this thread up.


I was reading the advert on one of the Greek RIB mags about prop gurads.

The advert claims the following:

TRANSLATION
ONly prop guard offers the following advanatages:

Safety to you and people around you
Protects your expenssive SS prop
Increases the performance of your prop
Increases the acceleration of your boat
Reduces fuel consumption
Reduces forces that come from the propencity (hope this is the right word) of your prop
Improves boat steering
Makes your prop to be seen from istance when you are or want to be on tow
It does not rust
Easy to assemble
Is supplied for prop diameter 7"-16" for inboard and outboard engines

QUESTION:
If any one has own experience, what if any of these remarks is correct?

[Louise]

Prop guards have been discussed before. Try doing a search. HTH

[Manos]

I know that Louise (there are 3 threads this one included) and thanks for the info.

I looked 2 of the previous threads but it does not seem that any one actually has used them and everyone talks hypotheticaly.
So I am asking whether any one has used them and what they think if they have.

[Louise]

Some of the old posts do recount people's own experience rather than being purely hypothetical, e.g. the thread titled 'Any opinions on propeller guards'. Others report on magazine tests. Might be worth another look while you wait for responses from current forum members?

[Manos]

Thanks Louise will do it again but is getting 9:30 here and have to get a RIB in the water in a while. Possibly later. Thanks again

[Simon B]

We had one fitted to our dive boat. It came as "a special offer" when we had the new engine put on. This was a plastic schulz nozzle design from propguard corp in the USA. It did reduce speed by about 5 knots.

It met its sad demise on rocks which is another thing to bear in mind in that if you do run aground the prop and the guard will be damaged, ours was completely destroyed with some tip damage to the prop.

We have not replaced it I'm sad to say, mainly due to cost. The speed loss was never subjectively tested as there appears to be a great deal of opinion spouted as fact without people saying ok lets test this and record the results on paper. What happens is beer is drunk and what seemed like perfectly clear facts suddenly arent?! Weird ey!!

[Manos]

Thanks Simon I thought that it is not possible to give you better performance (speed wise). It was just an idea for the hored RIBs to avoid propeller banging but will forget it. Better to change them over and do the repairs to the old ones.

[Simon B]

Manos,

There is a theory that the schulz nozzle does allow the prop to be more efficient I dont know exactly how, this effect is used by this type of prop guard to make it in theory at least, able to operate without loosing speed. It is supposed to be a tunnel wing used underwater I think.

I would hazard a guess though that the increased appendage drag does means speed will be lost at higher speeds. Though slow speed manouvrebility may be better.

Again it really falls to more exhaustive testing to prove either way or an expert in the field to shed more light, my green blobless status is sadly a reflection of my paper thin veneer of knowledge.

[SteveHall]

Another Sad Accident..

http://www.sky.com/skynews/article/0...156953,00.html