Best Prop guard?

[Rokraider]

We are investigating fitting propguards onto our club safety RIBs. They are currently equipped with 50 HP E-tecs. They will be operating in Chi harbour and will invariably get knocked about in the shallows, so need to be tough. Any recommendations?

[TonyC]

Personally, no guard and extra training

[Rokraider]

Originally Posted by TonyC

Personally, no guard and extra training

I agree and we are trying to raise the standards of driving. We have a very good safety boat driver course that is basically the RYA course with add ons that cover the peculiarities of Chi Harbour and Hayling Bay and rescue and towing techniques of the wide range of dinghies that race at the club, but accidents do happen.
Our problem is that members who have PBL2, volunteer to drive the RIBs for safety cover for dinghy racing. Being a large club with a fleet of 10+ club Ribs, we are always struggling to get enough volunteers to helm the RIBs. These volunteers may only drive a RIB 2 or 3 times a year and are often rusty. As a responsible club we are looking to reduce the odds of an accident and if propguards help with that, it makes sense to go with them. They will also reduce the number of damaged props hopefully.

[rigi36]

From my experience in a safety setting, prop guards make people complacent.

"Oh, it doesn't matter if the prop gets a little too close to the bottom, i've got a prob guard."

"Because i've got a prop guard fitted, it will be ok to get just that little bit closer to that sailor in the water."

In fact, prop guards can make and injury worse.

[Rokraider]

Originally Posted by maxhar

From my experience in a safety setting, prop guards make people complacent.

"Oh, it doesn't matter if the prop gets a little too close to the bottom, i've got a prob guard."

"Because i've got a prop guard fitted, it will be ok to get just that little bit closer to that sailor in the water."

In fact, prop guards can make and injury worse.

That's interesting, how does it make injuries worse?

[gotchiguy]

Originally Posted by Rokraider

That's interesting, how does it make injuries worse?

Trap the limp inside reducing the (already slight) chance of it being thrown out.

[wavelength]

equipped with 50 HP E-tecs.

which will become 35/40 hp with a propguard.

Don't like 'em, get a pebble rattling around inside the guard and the props gone. However in the event of a mishap it might impress an ill informed investigator that you had taken all reasonable precautions and excercised all due diligence The local beach lifeguard boat used to have one just for that reason..made it a slow thirsty slug though. Whatever you get I'd get just one fitted and see if ya can live with it.

[Poly]

The general RYA advice is against prop guards for safety boats.

http://www.rya.org.uk/sitecollection...d%20policy.pdf

Obviously you need to risk assess it yourself, in your specific situation - but will it:

- lead to complacency about prop safety?
- discourage safe practice, e.g. use of kill cords / engine off when alongside people in the water?
- reduce speed at recovering casualties ashore if required?
- increase the risk that someone gets struck by a boat at speed (because it is 'safer')

I do understand your problem but if you aren't confident about safety boat drivers ability to keep props away from people in the water can you really trust them to:

- know how to deal with an unconscious casualty in the water?
- respond correctly to an entrapment?

or any other critical issues.

From a prop-life prospect then whilst you might go through fewer props I think you might find people take bigger risks with the "bottom" and when you do hit something it will be hard and could be the whole leg not just a prop that needs replacing.

Perhaps if buying a new safety boat and really worried about this I would consider the jet drive leg options on the market. Personally though I would be ensuring that I was confident that all my safety boat crew were proficient at handling the boats and if not:

- providing additional training (many clubs consider PB2 to be the minimum, others insist on full safety boat qualification in addition, that is quite a big time demand for training a large number of people, but you could probably produce a shortened course which focusses on the priorities, e.g. I would want to see first aid and probably VHF protocols covered in more detail from what I've seen at typical clubs, as well as a good understanding on the local emergency procedures).
- insisting on regular competence reviews and assessments (e.g. once every 3 yrs having to do a 1/2 day refresher / workshop to ensure up-to-date). This would also be a good opportunity to carry out an "exercise" to test all procedures from recovering casualties to resus on board, recovery to shore etc.
- having procedures in place to remove incompetent operators, and a "management" process in place so you can spot those who need coaching before a problem happens.

If getting volunteers to man boats who can demonstrate competence is a problem:

- are you supporting them adequately?
- do you want them if they don't see the importance of these skills?
- could you get a smaller team of more dedicated volunteers who take it seriously and train well? Are there people who would like to do it regularly in return for good training? Could you recruit volunteers (possibly from outside the club) just to do this? How do you reward your volunteers? e.g. are those who do their fair share given any discount on membership? if you had non sailing volunteers would you expect them to pay for membership?
- if you need "professional staff" it may be time to consider employing people. I know of one club whos entire safety boat team is paid (albeit minimum wage).

[Rokraider]

It is an interesting topic. I have been perusing several sites to get an overview. The advice seems pretty universal, nice idea but very problematic. I have also been looking at Outboard jets as a possible way forward. Does anyone have any feedback of the current models, they would care to share? If they work, that could be a good solution.

[9D280]

Does someone not make tunnel props? A weird halfway house between conventional prop & jet.

Firewall is blocking anything with a pic to link to at the mo, but the basic concept is your bog standard prop in a toob. Doesnlt stop small things getting ingested, but would mean in the unfortunate case of comatosed sailor meeting it they are infinitely less likely to get "chopped", and the ring round the blades means it may survive a bottom strke a little better, unless of course it just collapses.

[captnjack]

Originally Posted by Rokraider

It is an interesting topic. I have been perusing several sites to get an overview. The advice seems pretty universal, nice idea but very problematic. I have also been looking at Outboard jets as a possible way forward. Does anyone have any feedback of the current models, they would care to share? If they work, that could be a good solution.

They work with a substantial loss of total HP power and loss of some general performance in the mid-rpm ranges. Idling they are highly manuverable and fine. At WOT or nearly so they are enjoyable to use IMHO. Mid-range expect some sluggish responses, difficulty staying on plane, and general finickiness compared to a prop outboard.

They will suck up stones in shallow water and seaweeds something fierce. Most of this debris will lodge in the inlet grate and stay there until you shut the motor off, tilt it up, and clear it by hand or with a rake. Which pretty much requires hanging over the transom.

Originally Posted by 9D280

but would mean in the unfortunate case of comatosed sailor meeting it they are infinitely less likely to get "chopped"

As the RYA link points out, arms and heads etc can still get struck anyway. AND may actually be more likely to get struck by a ringed prop since the operator <thinks> the prop is immune to such things.

Originally Posted by 9D280

the ring round the blades means it may survive a bottom strke a little better, unless of course it just collapses.

The rings I have seen don't collapse nor is the prop bent typically. The aluminum casting of the lower unit just cracks instead.

[Rokraider]

We are not looking for blistering performance, the RIBs spend long periods just chugging about, but they do need to be able to tow and be able to get a dash on when needed. They usually have a 2 man crew. The worse case scenario would probably be to tow a keelboat such as a SB3, or Flying Fifteen back over the Chi Bar in high winds and big waves against a 5-6 knot tide with 2 or 3 more people on board. It is not unusual to have a string of smaller dinghies with their crews on board being towed, but that is usually in a no wind situation but may be against a strong tide. The current boats have their hands full in these conditions, we would need to have the equivalent of around at least 60 HP at the jet IMO. Based on the sort of losses being suggested, I imagine it will need around 90-100 Hp from the motor?

[Poly]

Rokraider,

As an afterthought - I'm not sure how a jet outboard handles, if it is like a "real jet" then its quite different to an outboard in which case you might have some training issues anyway.

[captnjack]

Originally Posted by Rokraider

we would need to have the equivalent of around at least 60 HP at the jet IMO. Based on the sort of losses being suggested, I imagine it will need around 90-100 Hp from the motor?

A 90hp jet is roughly = a 70hp prop in actual thrust.

While jets are amazingly manuverable at low speeds, I am not sure how the performance will be towing loads at displacement speeds. I would guess rather anemic.

Sounds like you have a pretty big RIB, most of the sailing club safety boats around here are much much smaller. 3.5 to 4.5m, 9.9 to 25hp type things.

[Rokraider]

I was wondering about that. Do they have a bucket for reverse? The spec sheets make it sound as though they have a forward facing port that opens for reverse and close the rear outlet?
We are taking all our drivers through ongoing training programmes, so I don't see a problem with some additional training. In fact it would be a compulsory refresher course before they would be allowed to use the new setup.

[captnjack]

Originally Posted by Polwart

Rokraider,

As an afterthought - I'm not sure how a jet outboard handles, if it is like a "real jet" then its quite different to an outboard in which case you might have some training issues anyway.

They are similar in forward although a bit more manuverable I think (depends on deadrise). They are pretty weak compared to a prop outboard in reverse. I have a few hundred hours on jet outboards in the ~75hp range although only on 2 different hulls.

[captnjack]

Originally Posted by Rokraider

I was wondering about that. Do they have a bucket for reverse? The spec sheets make it sound as though they have a forward facing port that opens for reverse and close the rear outlet?.

Yes, commonly called a "clamshell" which swings over the outlet. The engine and impeller always turn in the same direction.

[Rokraider]

Originally Posted by captnjack

A 90hp jet is roughly = a 70hp prop in actual thrust.

While jets are amazingly manuverable at low speeds, I am not sure how the performance will be towing loads at displacement speeds. I would guess rather anemic.

Sounds like you have a pretty big RIB, most of the sailing club safety boats around here are much much smaller. 3.5 to 4.5m, 9.9 to 25hp type things.

All of our RIBS are around 5.5 - 5.8 metres and the proposed new ones will be around 6.0.
They have to operate inside the harbour in strong tides and occasionally lumpy water as well as out in the bay where it can get very rough and windy. To get out into the bay, you have to cross the notorious Chichester bar which can get extremely rough with waves that are quite capable of rolling a RIB if caught off guard. The 5.5's are pretty uncomfortable out in the Bay in rough weather, the 5.8's are better, but still too small really if you are on duty for 8 hours or so.
The club is quite large by UK standards and hosts a lot of World cup events. Last year we hosted the Laser Worlds which involved (I believe) around 700 Lasers (Olympic class) over a 3 week period, all out in the Bay. As you can imagine, the club RIBS got quite a hammering.

[9D280]

Originally Posted by Rokraider

As the RYA link points out, arms and heads etc can still get struck anyway. AND may actually be more likely to get struck by a ringed prop since the operator <thinks> the prop is immune to such things.

The rings I have seen don't collapse nor is the prop bent typically. The aluminum casting of the lower unit just cracks instead.

Not sure my description was so great. I'm not talking about a toob attatched to the leg / skeg, more like what those in the pumping world would describe as a "shrouded impeller".

To describe explicitly: Take your prop off the boat, and into a workshop. Then take a length of sheet material slightly longer than the prop hub length by <pi x blade tip dia>. Wrap it round the blade tips, and weld to the tips, thus enclosing your prop in it's own toob. (of course if you have cast it from scratch the toob will be cleverly shaped to improve the thrust - that's the one I can't for the life of me find the link to). Replace the prop.

This then gives you what from the outside is a rotating cylinder, no blades to catch stuff that drifts past. As I said, it will still ingest, but there's a lot less there to potentially go wrong, as any unconcious limbs would need to get past the gearbox and be pretty much parallel to the keel at the keel to be fully entrained. If you look dead astern at the midpoint of your gearbox, that's only about a 3"-ish gap on a 50Hp.

Mt comment about collapse was more related to if you hit something like a rock, the outer ring could transmit the force to all three blades, which will either help as you have more metal to move, or collapse the whole thing as the force is transmitted round the ring.

It also behaves more like a prop, so no re- training on operation required. Point out to the drivers that it's still a prop & will still mince, so treat it like a normal prop & risks should be reduced.

[Poly]

9d280,

I think you are possibly thinking of: RingProp? They seem to have dissapeared. There is some history here: RingProp | Propeller Guard Information Center [a rather weird american site which seems to spend more time telling you what everyone else offers than they do]. Whilst 'waybackthen' says: Ringprop - News