GRP Modifications For Ice / High Latitudes?

[Tim Good]

I notice a few references to small modifications on wooded boats for trips up to high latitudes where the abrasive action of small chunks of ice can cause waterline wear.

I wonder if anyone knows of similar temporary mods people have done for GRP boats? I wonder if something i roll format could be installed temporarily and secure at various points along the toe rail and then removed, rolled and secured for longer ice free passages.

Here are some pics of inspiration:

SS

Kevlar

 

[Sybarite]

I notice a few references to small modifications on wooded boats for trips up to high latitudes where the abrasive action of small chunks of ice can cause waterline wear.

I wonder if anyone knows of similar temporary mods people have done for GRP boats? I wonder if something i roll format could be installed temporarily and secure at various points along the toe rail and then removed, rolled and secured for longer ice free passages.

Here are some pics of inspiration:

SS

Kevlar

John Gore Grime's Najad 441 is reinforced with kevlar and the Wauquiez Pilot Saloons with "twaron" as in bullet proof vests.

Jeanneau also incorporated kevlar into their Sun Fizz from 1985 onwards.

 

[Tim Good]

John Gore Grime's Najad 441 is reinforced with kevlar and the Wauquiez Pilot Saloons with "twaron" as in bullet proof vests.

Jeanneau also incorporated kevlar into their Sun Fizz from 1985 onwards.

Interesting. I tried to find details online with no success. Any idea how each of those was achieve?

 

[sighmoon]

Dehler's were also Kevlar reinforced from the 80's, and in that case it's a layer in the lay up, so the gel coat is not harder than usual.

I suspect the others are the same.

 

[Kukri]

I've been in high latitudes in a wooden boat and a steel ship but not a GRP one.

Kevlar and quite a lot of it, epoxied on in way of the waterline, would add useful strength but I am unsure of the abrasion resistance of Kevlar.

You won't be forcing ice so you only really need to worry about the occasional bump and scrape.

I would be cautious about something in a roll secured to the rail because the ice could, I think, drag it out of place

At risk of teaching grandma, beware of integral water tanks...

 

[pmagowan]

I had this same question in my head. I was thinking steel plate, quite thin, could be attached with sikaflex or similar in a slightly overlapping structure so that the final bent bow plate could protect the edge of the plate aft of it. The thin steel would spread the load and the sikaflex would act like padding to protect the hull while holding the steel on. It must be possible to get a sika that would work for this and be removable so that the gel coat would be returned to normal. I suppose a spare tube could be carried and the plates attached to the guard rail so that any that were knocked loose could be reapplied.

 

[Deleted member 36384]

The thing about ice, especially old ice, is that it is hard, very hard. So if you whack an edge of old ice at a few knots, it will take more than 'quite thin' plate to protect the GRP.

There were lost of tests done on ice for offshore platforms and old ice is far harder than concrete, significantly so.

I think that a strong envelope, like the pictures in the OP, but wrapped more, at 3 mm thick, should provide some protection. A poor buy version could simply be a section of angle iron bend around the bow and fastened in place. I believe any meaningful protection would be so heavy that one may as well use a round chine steel hull. GRP is not really made for ice deflection, best to avoid. There is a risk that water trapped between the plate and GRP could cause serious damage if it froze and was constrained from expanding. If the plate was attached in such a secure way, the ice may just crush or rupture the GRP.

 

[pmagowan]

The thing about ice, especially old ice, is that it is hard, very hard. So if you whack an edge of old ice at a few knots, it will take more than 'quite thin' plate to protect the GRP.

There were lost of tests done on ice for offshore platforms and old ice is far harder than concrete, significantly so.

I think that a strong envelope, like the pictures in the OP, but wrapped more, at 3 mm thick, should provide some protection. A poor buy version could simply be a section of angle iron bend around the bow and fastened in place. I believe any meaningful protection would be so heavy that one may as well use a round chine steel hull. GRP is not really made for ice deflection, best to avoid. There is a risk that water trapped between the plate and GRP could cause serious damage if it froze and was constrained from expanding. If the plate was attached in such a secure way, the ice may just crush or rupture the GRP.

But it is not the strength of the steel that is in question, it is the steel, sika, grp composite. The steel simply provides the external 'scratch resistant' coating. There is a big difference in strength of a simple steel sheet and one that is bonded to a substrate with a flexible adhesive. The force needs deflected and spread aver a wide area. You could even glass over the steel to give it further impact resistance.

 

[Deleted member 36384]

But it is not the strength of the steel that is in question, it is the steel, sika, grp composite. The steel simply provides the external 'scratch resistant' coating. There is a big difference in strength of a simple steel sheet and one that is bonded to a substrate with a flexible adhesive. The force needs deflected and spread aver a wide area. You could even glass over the steel to give it further impact resistance.

I am not questioning the strength of the steel which is the only thing that matters in the context of the OP. There is no additional strength in the composite that you imagine; the Sikaflex may add some damping which will allow a deceleration slightly longer than in the non damped case, but at a value that is probably negligible.

The steel will yield at the value for that material and sikaflex will not increase that, so if hard ice strikes the thin steel at a suitable velocity, then the force may puncture it and peel it open. If one is planning on pushing ice then a steel boat is required unless the ice is very small. Small brash ice could be pushed clear but that would be a very serious matter for a GRP hull to undertake, even if it was protected. From what I have read about ice navigation in GRP boats, all ice is avoided like the plague and great care is taken to do so. Would you run your GRP hull down a floating concrete pontoon, no you wouldn't.

Abrasion is caused by friction and it can be dealt with by reducing the coifficient of friction along the water line by using something live VC Offshore with Teflon, or even just adding additional layers of GRP/Epoxy with graphite and polishing it to a very smooth finish. This latter method would also provide sacrificial protection for the harder knocks. However, if pushing ice is the remit then GRP is not suitable, in my humble opinion. By the time its beefed up for the forces involved, one may as well have bought a steel boat (which incidentally can still be punctured by brash ice mass.

 

[pmagowan]

Steel will yield at different forces in different circumstances. A plate held tight and impacted by a sharp object directly will yield at much lower forces than one which has some 'give' and is at a deflecting angle. You need something strong enough for the job at hand and there is no reason why steel could not be fixed to a grp hull to achieve this. It may be that other substances or composites would be better but steel is a good start. I would imagine the bow would have a greater size plate with larger dampening (perhaps some foam or similar) behind it. This would overlap with progressively thinner plate. It is only required in certain high impact areas and deflected ice is a much less destructive force than the initial hit.

My hull is wood and I have already tested it against a few impacts with minimal concern. I do wonder at why steel, with its sensitivity to temperature, welds, and propensity to buckle under impact would be a better defence than a steel grp composite. Personally I am interested in how a strip plank cold moulded steel reinforced boat would manage.

 

[Kukri]

I think the real dangers are bergy bits and growlers, and, if going to Spitzbergen, or anywhere in that direction, floating logs, which are really quite numerous. In open pack up to 3/10 you ought to be able to avoid any contacts and the good thing is the sea will be flat. So I would put effort into strengthening the bow area.

 

[Pete7]

Personally I am interested in how a strip plank cold moulded steel reinforced boat would manage.

See i you can find David Scott Cowper's book about his adventures in the lifeboat Mabel e Holland. Rather him than me though.


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

 

[jdc]

I think the real dangers are bergy bits and growlers, and, if going to Spitzbergen, or anywhere in that direction, floating logs, which are really quite numerous. In open pack up to 3/10 you ought to be able to avoid any contacts and the good thing is the sea will be flat. So I would put effort into strengthening the bow area.

As far as reinforcing is concerned, it's a bit of a waste of time imho. Ice is 9/10 under the water, in weird shapes, as every one knows. That means that a piece of ice you can see sticking foot or two above the water extends ten feet below - deeper than your keel, prop or rudder - and almost certainly is wider below the water. So it's not necessarily or usually your bow near the surface which strikes it. The prop is perhaps the most vulnerable bit from this perspective.

Also it's not banging head-on into a hitherto unseen bit of ice which is the real danger I believe, but ice closing in around the boat. This will as likely crush the sides as anywhere.

For a 'fun' video of a boat being towed through ice look at this https://www.youtube.com/watch?v=nsOsWEo4p1Y. A bit of a special case so perhaps not that representative (being towed behind an ice-breaker!!) but it clearly shows the keel striking ice more than the hull near the waterline.

PS: We saw very few logs around Svalbard (aka Spitzbergen) on the west coast since the N.A. drift is from S to N on that side (which is why it's also ice clear most summers). It's only on the E side, where vastly fewer yachts visit, that there are [reported to be] significant numbers of logs. Don't be put off, or feel the need to play around with mods etc: we saw boats from France, Belgium, Netherlands, Germany and Norway. The French were there in normal plastic benjav AWBs (complete with toddlers on board of course). But none from the UK except us: I fear we in the UK are fast becoming H&S obsessed wimps compared to our continental neighbours.

So just go! It's a great cruising ground and the dangers are much exaggerated. Chances are it'll be quiet summer weather with 24 hour daylight.

 

[jerrytug]

Good post jdc!

 

[pmagowan]

I certainly don't want to be an H&S nut, I want to be able to hit some ice! If I venture north and there is no ice to hit I would be sorely disappointed.

 

[jdc]

I certainly don't want to be an H&S nut, I want to be able to hit some ice! If I venture north and there is no ice to hit I would be sorely disappointed.

Best go soon then - the glaciers are all in retreat! But seriously, there will be ice to hit all-right but you won't want to do so. Even small bits of ice like this one (in Smeerenberg fjord) will weigh ten or more tonnes and would sink even a steel boat if struck hard enough.View attachment 43371

 

[pmagowan]

Just a nudge!