Ice Propellers

Ah, Penguin poppers.

Black Coast Guard boats--Work boats--Buoy tenders and such.

White Coast Guard boats--Enforcement--Cutters and such.

Red Coast Guard boats--Research and Ice breakers--aka Penguin Poppers.

So what do you want--Do they employ C P wheels with cort nozzles and are they steerable nozzles or do they use rudders?

My guess is they are nozzled as it would give them the traction to drive up on the ice--but it is all just guess work from here.

The big red boats are huge and expensive--Are there design flaws? What is the problem with their props?

The Polar Rollers (or Penguin Poppers, as you so eloquently put it) use three (3) controllable pitch propellers, each 16 feet in diameter.

They don't use kort nozzles. That is one of the technologies that we are looking into for this future design, however. I'm not positive, but I think the reason that they decided not to was because they are very inefficient at higher speeds. It might be a trade-off that the Gov't will have to consider this time around, however.

They do have standard rudders, albeit really beefed up to survive an encounter with ice.

As far as I know, any design flaws have since been worked out over the 30 years the ships have been in service. They use 1960s technology; state-of-the-art back then; archaic now. It's been suggested (many times over the last decade, actually) that because the current CG assets have worked this well for so long, why not just dust off the old blueprints and re-build them all again? Hopefully you all can see why this isn't the most cost effective way to go.

My personal thoughts are that the CG needs to go with current state-of-the-industry technology, however I'm not exactly sure what that is yet. I can't let my own views bias my research, but if I can find substantial evidence to back them up, I can justifiably include them. I'm not the final decision making authority though; just one of many cogs in the machine.

Speed and steering get sacrificed with nozzles--But I would think you would need the improved thrust to crawl onto the ice.

How bad is the loss of speed with a CP wheel in a nozzle?

Ice breaking is a tough business and those boats don't look like they are designed for speed anyway--I wouldn't think getting self conscious about the rate of travel is that big of deal knowing what the vessel is capable of. I spent a decade and a half traveling no faster than 12 knots.

I am sorry, but I won't have much to offer in the way of technical help, here. I suppose we keep this thread alive long enough for someone to come along with some help for you?

How many Big Red Boats are there, anyway? I knew a couple guys that worked on them and they gave me the impression that ice breaking was going the way of the Dodo.

The Polar Rollers have upwards of 75 kHp; I'd imagine they have plenty of thrust... I'm not sure of the exact data for a CP-Kort combo, but if I remember correctly, the efficiencies of open props and ducted props is roughly equal at around 10 knots.

True, normally breakers don't care about speed, however the CG needs to have multi-mission platforms that can handle law enforcement, search-and-rescue, etc. that require a vessel at least capable of 20-ish kts. Cruising speed is probably in the ballpark of 10 or 15, though.

Besides the two Polars (well, one and a half really, now that the Polar Star is permanently dockside), the only Icebreakers the CG has are the Healy and the Mackinaw. The Healy is made for arctic science, and it's not very good at breaking ice, while the Mighty Mac is on the Great Lakes. The most we ever had at any one time was 8 ocean-going breakers. The last of the older breakers was decommissioned in the late 1980s. For a long while the CG thought it was going to give up the icebreaking mission, but within the last 5 or 6 years the general consensus has shifted 180°. You can read the full report here if you're really interested, but I have to warn you that it's a little dry...

I'm pretty sure that the CG will start asking design firms for bids within the next 5 years. I'd be willing to bet on it, actually.

Is there any possibility for multiple systems? Both props for torque power and jet nozzles for speed, for example?

Is there any possibility for multiple systems? Both props for torque power and jet nozzles for speed, for example?

look into the mark 5 special ops craft for the seals..........(probally up to the mk7 now)

It's a possibility, however jets don't work well in the bollard-pull condition. They're mainly for high speed in open water. And "high speed" for a 15k LT ship is not quite the same as a USN special ops boat. But we'll consider it. One problem I can foresee is that while under jet-drive, the props would get sheared off unless they can be retracted, which then may weaken their overall resistance to being pounded by ice.

The hamilton water jets are mainly used for covert deployment and pickup in shallow water.

Speed, they relay on the twin 3,000 HP MTU engine with surface peircing props.

just throwing things at you.

remember ice or any foreign object in the water is hard on the props, (as well as the hull)........look into how the military handles it

I'm well aware, actually. I've designed an icebreaker for the Coast Guard (albeit as an academic exercise; I doubt they'd ever use my ideas), and I could practically write a dissertation on "how the military handles it." In all of my research, I haven't seen anyone use jets in ice, but that isn't to say that it can't be done. The Swedes and Finns are pretty clever when it comes to ice and boats; I'll leave it to them to figure out how to make it work!

Maybe, but if by "retracted" you mean what I would, that they're hauled screw, shaft, and all up into the hull, I don't see why they couldn't be Hell for stout.

I guess that could work, too. I've never seen any modern ships retract their propulsors, but I'm sure it could be done if you could somehow engineer a really strong connection between the movable part and the rest of the ship. The only ship I've seen that could do something like that was the Fram, which was designed to intentionally beset itself in the ice floe so that it could drift to the Poles instead of trying to crash through the ice. Pretty ingenious, actually. Another potential issue with a retracting prop, shaft, etc. is the internal space it would take up. Even on a 400 foot Polar Roller, space is at a premium. Maybe on the 500+ ft nuclear-powered breaker I dreamt of could do it, but it's doubtful the Gov't is willing to spend the cash on that monstrosity.

When we would trim our boat out to travel across the gulf of Alaska-We would look at the weather first. If it was going to be rough, we would press our tanks and ride it out--If it was going to be nice we would transfer fuel out of our stern tanks and pump out our aft fish holds to get light and get the stern out of the water--We would tank back down before the weather turned.

Maybe propulsion isn't the only important aspect of gaining speed and being able to break ice--Just not with same configuration of ballast.

Make it long and slender with the stern high while trimmed for speed--With a wider taper and rolling chocks to dispatch the ice while tanked down and bring the bow up and bury the stern and CP wheel deep away from the ice.

?????

Hopefully, you've looked into Russian designs. They have some impressive technology for dealing with ice.

Next Russian Icebreaker

Hooker

Yeah......no kidding! A fleet of 140 icebreakers compared to Canadas 2.

Many were built for them by Wartsila of Sweden.

good direction Hooker...... russian or norwegian, they are years ahead of USCG designs

Thanks for the article! Yeah, we've looked at the Lenin, Yamal, 50 Let Pobedy, Arktika, and the Taimyr nuke-breakers. They can't transit through tropical waters due to the nature of their cooling system, so hopefully if the US decides to go with nuclear powered icebreakers (which I hope it does), they can improve upon this. I don't think it'll be an issue, as we already have nuclear powered submarines, aircraft carriers, and cruisers that can traverse the world's oceans.

My bias runs in the opposite direction. For the application, variable pitch props are state of the art. Unless you learn something from the Russian's or Swede's that demonstrates otherwise, a field tested and proven design for a mission critical component like a prop can't be beat.

If you need the boat to go faster then the prop diameter will have to come down. Edge cavitation is a primary limiting factor in prop speed and RPM times circumference yields edge speed, no getting around that.

If the diameter comes down all other things being equal then so does the power, and there goes your ice breaking mission critical performance.

The only realistic compromise is a gear box and twin screw design including variable pitch props. Seek out a reliable vendor for this and get their input. Unless there is a mission critical need that drives innovation there is NO reason to innovate.

Innovation is a very expensive process and the costs are not all economic. If you end up responsible for an equipment failure that strands a boat and crew above the arctic circle you will never be asked for your opinion again.

Doubly so if your innovation causes the loss of the vessel and all hands. (I only mention this one because a seal failure on the prop shaft of a retractable prop shaft is basically a certainty, and a bearing failure is a great likelihood. If the bearing fails during a prop shaft extension or retraction then the possibility of a big hole in the most critical part of the vessel is certainly a possibility.)

I know you are just doing some preliminary canvassing and out of the box thinking which I strongly approve of, the next step in the decision tree building process is to weed out the dumb and or dangerous ideas and focus in on what works. I am being a bit of an ass about it, but, I am also trying to help you with that next stage.

I don't even like my own suggestion of twin screws. If they are beside each other there will be more frequent and more energetic impacts of the impeller blades with the ice chunks and if they are in line with each other then the turbulence of the first will interfere with the proper function of the second. On many twin screw twin engine vessels if one drive system fails for any reason the vessel can still limp in on one engine. This would not be true of an ice breaker breaking ice. The vessel would be stranded. Because of the unique mission of this proposed vessel many things that work else where are of no benefit for this application.

In my opinion if the coast guard wants an ice breaker then you should give them an ice breaker. If they want an ice breaker that also functions as a PT boat then you should give them an ice breaker. On the other hand if the rear admiral wants an ice breaker with a sauna on board by all means give the man a sauna, so long as it does not interfere with the ice breaking, its all good. Given the service area for an ice breaker a sauna would certainly be popular with the crew and might even save someone's life in the case of hypothermia. We can all be thankful to the Swede's for that particular design innovation....

Sincerely,

Mr. Gee

Good solid points Mr.Gee, but I feel compelled to pass this along.......

Just in the off chance you ever run into someone who is hypothermic--The last thing to do is to give them a hot shower or sauna. That cold blood in the extremities will hit the bodies core and heart and kill them. They must be warmed slowly from the core outward--The body will decide to dialate the vessels in the arms and legs when the core temperature rises.--COLD WATER NEAR DROWNNG.

http://www.scuba-doc.com/hypoth.htm

Very interesting and informative post. Yes there are compromises, I kinda hate that word, Also design/size of prop can vary the cavitation, But I don't think they would care too much about silent running

We were doing a coastal patrol boats for the coast guard, they wanting to upgrade the fleet.

The yards engineers and naval architect understanding was to included a new hull design, We basically lost it, because they wanted to used the existing designs.

Times like that, one wonders what the hell is going on. Are the wrong people involved, do they know whats going on, or understand the scope.

The CG might have wanted a new design, but were told they did not. They, too have higher authorities...

I have a feeling the that the people on our side, had misunderstood the scope, just by the way as we were preparing the bid, creating models for tank test purposes, the people in charge seemed vary unsure of themselves, but because they didn't have confidence they did not want to put a stop to something they started.

I felt that there were allot of red faces at the yard, when the CG rejected our quote because it was not what they were looking for, we had less than three days to correct, requote submit it. That along is not enough to give confidence to the customer (being the CG)