Northwest Passage

Re: ice plates.
How thick would they have to be to serve the purpose? Just talking here about protecting gelcoat on a GRP boat, not turning it into some sort of icebreaker.
Is there an easily available metal (alu or ss) tape that would suitable? Thinking of something similar to those expensive self adhesive chafe pads that you get to protect gelcoat from running lines.
 
Kelpie said:
Re: ice plates.
How thick would they have to be to serve the purpose? Just talking here about protecting gelcoat on a GRP boat, not turning it into some sort of icebreaker.
Is there an easily available metal (alu or ss) tape that would suitable? Thinking of something similar to those expensive self adhesive chafe pads that you get to protect gelcoat from running lines.
Click to expand...
I have been thinking about this. The main role of plates would be abraision resistance and to resist the odd impact. For AR it should only require to be of a thickness where it isn't simply scraped off, a few mm of steel. For IR the malleable nature of steel will work well particularly if it is attached with a layer of a resilient substance which springs back into shape. For instance a silicone adhesive or a PU foam. It only needs to spread the force of the impact to prevent puncturing of the GRP outer layer. The risks are that the extreme temperatures, freeze thaw and associated pressures may cause the plates to de-adhere.

The extent of reinforcement could vary from within a few inche's of the bow to running from bow to the shoulders of the boat. The former would protect mostly against the inevitable impacts where as the later would also protect against general abrasion. Since simple GRP and wood boats survive ok without these alterations it may be overkill. An alternative is to get a lift-out in Alaska to repair the odd dent or damage to the paintwork.
 
Most of ice is under water, and sculpted into weird shapes so the idea that simply coating [part of] the hull with some abrasion resistant material would be worthwhile is pretty dubious - it might be if on a mooring in a freshwater river but not, I think, if at sea.

The damage one really must fear is probably to the propeller - in the high arctic or antarctic you will often be motoring and so to damage the prop or bend the shaft through collision with ice would be catastrophic and is possibly the greatest danger imho. No steel plating of the hull will help avert this.

I also think too much fuss can be made of the temperature. Unless planning to over-winter while living aboard, which is to take you into a tiny minority of the already tiny minority who venture into the arctic anyway, it's simply not that cold: if it were, you couldn't get there! You can't get there or move about until the seasonal ice has largely melted, which means that the sea temperature has to have risen to a few degrees above freezing. And days will be long or even 24 hours for much of the trip. Damn chilly on deck of course, hence the attraction of a doghouse or solid sprayhood, but I'm unconvinced that special tanks need be contrived for fuel or water.
 
jdc said:
Most of ice is under water, and sculpted into weird shapes so the idea that simply coating [part of] the hull with some abrasion resistant material would be worthwhile is pretty dubious - it might be if on a mooring in a freshwater river but not, I think, if at sea.

The damage one really must fear is probably to the propeller - in the high arctic or antarctic you will often be motoring and so to damage the prop or bend the shaft through collision with ice would be catastrophic and is possibly the greatest danger imho. No steel plating of the hull will help avert this.

I also think too much fuss can be made of the temperature. Unless planning to over-winter while living aboard, which is to take you into a tiny minority of the already tiny minority who venture into the arctic anyway, it's simply not that cold: if it were, you couldn't get there! You can't get there or move about until the seasonal ice has largely melted, which means that the sea temperature has to have risen to a few degrees above freezing. And days will be long or even 24 hours for much of the trip. Damn chilly on deck of course, hence the attraction of a doghouse or solid sprayhood, but I'm unconvinced that special tanks need be contrived for fuel or water.
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I think I agree with you regarding the tanks. I have not heard of others insulating their tanks and most people used plastic jerry cans of fuel on deck. I expect that the water system will benefit from the heat of being within the cabin of the boat (unless I insulate it too well). I could easily have a temperature sensor on the cold water tanks anyway so that if it approached freezing I could take action.

I think the vast majority of the ice is a threat to the bow at, or just below, the waterline. I understand that large bits of ice have a larger underwater component but the idea would be to avoid these. It would not be possible, however, to avoid all the small chunks and pack-ice and most videos I have watched show the boats churning through that stuff pretty often with football size chunks hitting the bow.

I think the prop is a significant issue although my boat design makes it less vulberable than some others. I will have a long fin keel and a skeg hung rudder with the prop occupying a cut-out between the two. It may be wise to fit a prop-guard of some sort also but I suspect that anything that gets past the keel is likely to rip off the guard. I will study this more as it is obviously an important component. I can, of course, have a system for rigging up an auxillary portable engine to get out of trouble but I don't fancy diving the prop in arctic conditions.
 
prv said:
At the end of the day, if the water's liquid enough to dive in then it can't be colder than -2° or so. Drysuit and some decent thermals?

Pete
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Ha :) I will give you a call when I need someone to go for a swim. I expect the volunteers to be rather low in number. Of course, like most things, it is do-able but I don't fancy it. That said, a quick skinny dip up there is supposed to be good for the health! :eek:
 
prv said:
At the end of the day, if the water's liquid enough to dive in then it can't be colder than -2° or so. Drysuit and some decent thermals?

Pete
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Done routinely in the Antarctic by scientists; as you say, if it is liquid enough to dive in, it is around zero (sea-water freezes a bit below zero). As you say, dry-suit and appropriate under layers; I think the most difficult bit is keeping the face and hands warm, especially if manual dexterity is required.

But the the only bath at Rothera Research Station is there to warm a potential hypothermic diver, and is right next to the re-compression chamber!

Referring back to the ice issue - of course, all ice floats with a large proportion below the water. But in protecting the hull, we're not talking about big bits of ice; you'd better miss those or you might get a hole. It's small bits up to a foot across that can abrade the hull, and they are ubiquitous in some waters, and can't be avoided.
 
prv said:
I guess if you had a suit flood you'd be in trouble pretty quickly.

Pete
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I would say so. I have dived in a semi-frozen quarry in Aberdeen while it snowed (worst dive ever) and it was not the warmest thing I have ever done despite having a top quality dry suit and wooly bear. The face and hands are the bits that suffer as they have to be in neoprene and so not dry. Your face and hands go into instant cramp mode until they get over the shock. After the dive I couldn't speak as intelligibly as after 10 pints of stout since my lips were not under my command. It didn't help that my mask had sprung a leak and a small jet of super cold water was being directed right at my eye. All the fish looked ill, the vis was ****, and there was nothing to see even if it had been good. I would actually love to dive in the arctic but not to fix a prop. Some of the underwater footage there shows that it is really an encredible underwater environment.
 
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