Home |
Search |
Today's Posts |
#11
|
|||
|
|||
Sara Gamp comes ashore
On Thu, 10 Nov 2005 17:08:29 +0000, Peter Wiley
wrote: Notwithstanding, I like aluminium for boats myself and if I ever get the urge, would weigh carefully the first cost vs maintenance issues WRT steel and aluminium. If I recall, Ted Brewer wrote an article on this very subject (and he should know). Overall, he saw it as about a 50/50 situation as regarding ease of building (easier with Al, but trickier to weld), strength vs. weight, cost of materials, corrosion and electrolysis, etc. If you go into it understanding the materials fully, it's pretty straightforward. One point, however, to note is that while the vast majority of under 60 foot/under 19 metre yachts are built in various types of fibreglass, the majority of high-latitude boats are in metal, and a strong minority of passagemakers are also in metal. The Europeans and the South Africans make some lovely...and fast...boats in steel and aluminum, and they are not as widely appreciated in North America as is GRP, etc. But if it was good enough for Moitessier... R. |
#12
|
|||
|
|||
Sara Gamp comes ashore
rhys wrote:
On Thu, 10 Nov 2005 17:08:29 +0000, Peter Wiley wrote: Notwithstanding, I like aluminium for boats myself and if I ever get the urge, would weigh carefully the first cost vs maintenance issues WRT steel and aluminium. If I recall, Ted Brewer wrote an article on this very subject (and he should know). Overall, he saw it as about a 50/50 situation as regarding ease of building (easier with Al, but trickier to weld), strength vs. weight, cost of materials, corrosion and electrolysis, etc. If you go into it understanding the materials fully, it's pretty straightforward. One point, however, to note is that while the vast majority of under 60 foot/under 19 metre yachts are built in various types of fibreglass, the majority of high-latitude boats are in metal, and a strong minority of passagemakers are also in metal. The Europeans and the South Africans make some lovely...and fast...boats in steel and aluminum, and they are not as widely appreciated in North America as is GRP, etc. But if it was good enough for Moitessier... R. I think that generally steel boats are best above a certain size. But they are too inefficient or heavy below that threshold. Once you are up into the steel size range, all the other annoying things about steel boats become bearable. I just discovered that the steel boat that I Captain has areas 50% corroded due to stray current over the past three years. That just doesn't happen in fiberglass and happens faster in aluminum. Welding new plates on is a bigger job than grinding out blisters and no boat ever sank from blisters! Gaz |
#13
|
|||
|
|||
Sara Gamp comes ashore
Oh, I see why we are having this conversation.
I wasn't talking about Sara Gamp. There doesn't appear to have been much pounding in that case. A steel boat would have done fine as well and probably would have experience less deformation and damage. If you want to experience minimum deformation and damage from typical impacts, steel is stronger. However, if you really beat on a boat in extremis, the energy absorption and yielding of an aluminum structure may leave you with something deformed and battered but mostly watertight in a situation where the steel hull would have ruptured. The strength and resistance of the steel concentrates the impact. It's the rubber boat vs fiberglass dinghy thing except that the aluminum doesn't spring back. I'll admit that it's difficult to justify in typical engineering terms and, yeah, I'm talking about examples I'm familiar with that are anecdotal and without the controls of having a nearly identical steel hull go ashore at the same time. Professionally, it's not defensible to claim that an aluminum hull is more survivable but, hey, this is a newsgroup. The point is that aluminum is certainly an excellent choice for a long distance cruiser that is careful about the electrical system (and those pennies). If you were faced with getting a really badly damaged hull, patched, jury rigged, and back to safety, you might be glad that it was aluminum. If you make a habit of banging into things though, your boat will end up carrying more permanent dents if it is aluminum than if it is steel. I've seen enough steel hulls broken to be pretty sure that the boat I was referring to was more watertight than a steel hull of similar size and weight would have been after that treatment. When I saw it, it was about 150 feet back from the normal high tide line on a rocky island. -- Roger Long "Peter Wiley" wrote Oh, come ON. That boat (SG) is ballasted to a displacement of 14400 lbs. The steel version is ballasted to a displacement of 14400 lbs. Both versions have all inside ballast. The keel shoes are 1" thick plate in both cases. The chine bars are 3/4" thick rod. The frames are 2 1/2" by 1/4" flat bar. Can you explain to me how this ballast mysteriously changes between a steel hull and an aluminium hull? How the aluminium hull managed to keep water out that a steel hull would have allowed in? Why would a 4mm thick steel hull plate be ruptured, allowing water ingress, when a 6mm aluminium plate hull kept the water out? |
#14
|
|||
|
|||
Sara Gamp comes ashore
"Peter Wiley" wrote
Nice boat. Thanks. I have 2 30', 6 tonne alum boats, 4 jet barges and a number of other small craft. However I also have steel vessels up to 6500 tonnes. How did you end up with all those boats? -- Roger Long |
#15
|
|||
|
|||
Sara Gamp comes ashore
On Thu, 10 Nov 2005 19:09:35 GMT, Gary wrote:
Welding new plates on is a bigger job than grinding out blisters and no boat ever sank from blisters! Agreed. I am looking at steel, aluminum AND fibreglass for ocean-capable cruisers in the 40-45 foot range. I am seeing decent examples of each, with a few observations: The aluminum boats are very touchy about galvanism, and dent easiest. However, they tend to sail very nicely, but command a premium in price and, I expect, attention from the owner to keep them free from electrical issues. To build them is easiest; to weld them is tougher. The steel boats have a huge variability in fit, finish and general construction. A lot of homebuilts are utter crap, particularly those ubiquitous Roberts designs; on the other hand, I have seen that about 1 in 10 are as good or better than any production boat of similar dimensions. The break point of steel in term of "too heavy" is around 40 feet for a cruiser, but you can get a "leisurely" sailer that is pretty bulletproof in that range if you are willing to wield a chipping hammer and stay on top of the paint schedule. The fibreglass production boats of today are generally insufficient in design and strength for offshore. They have too much freeboard and not enough beef where it counts. There are exceptions, of course, but if you can find and live with designs 25 years or so old (and the boat isn't a wreck or needs immediate repowering and refurbishment), you can find some nice deals. In sum, I am finding a pilothouse cutter and/or ketch that can sail semi-decently in any material is difficult, but not impossible. You won't find "names" in these category, however, because the vast majority of recreational sailors stop at coastal or perhaps Caribbean sailing grounds. That's fine: they have scads of choices, particularly lately as the charter fleets are cycling out middle-aged boats because there's reduced mooring due to hurricanes, etc. But a three cabin, two head Beneteau is a long way from what I want to cross the Pacific with. R. |
#16
|
|||
|
|||
Sara Gamp comes ashore
On Fri, 11 Nov 2005 01:33:03 -0500, rhys wrote:
The break point of steel in term of "too heavy" is around 40 feet for a cruiser, but you can get a "leisurely" sailer that is pretty bulletproof in that range if you are willing to wield a chipping hammer and stay on top of the paint schedule. I would contest this slightly, I have a 31' steel boat that weighs in at (allegedly - I never checked) 6,5 tonnes, which is not really any more than a similar sized cruiser of other materials. There are certainly much heavier wooden and plastic boats out there.. My hull is mostly 3mm I think, multi-chine with plenty of framing and after 20 years and 2 atlantic crossings the external plates are not significantly buckled except in a couple of places under the waterline where I think the hard stuff has been in contact. In your comment, you seem to be implying that a cruiser and a leisureley sailor would be different things? If so then maybe a steel yacht under 40' would be too leisurely for you, but I find fast boats are uncomfortable and noisy when I'm trying to sleep. -- http://maps.google.com/maps?q=irelan...9,0.082191&t=k |
#17
|
|||
|
|||
Sara Gamp comes ashore
In article , Roger Long
wrote: "Peter Wiley" wrote No it wouldn't and saying that demonstrates that you don't know the characteristics of materials. Steel is more ductile than aluminium - it will deform more before reaching its plastic limit and tearing. It is also less susceptible to work hardening and notch sensitivity, and welds can be 100% the strength of the parent material, which is not the case with al. Steel is also far more resistant to abrasion. True, (except for the first line), but we are talking about the behavior of an entire structure not a test specimen. The aluminum hull behaves sort of like a rubber inflatable boat and the steel hull like a fiberglass one. The glass hull is "stronger" but may be more likely to puncture in many situations. How does this work? The aluminium has a lower elastic limit (amount of flex before permanent deformation), lower plastic limit (deformation before rupture) and lower resistance to abrasion than steel does. It is structurally an inferior material. It compensates somewhat due to its lighter weight enabling thicker sections to be used, regaining some of the difference, and in shipbuilding due to its better corrosion resistance. The steel hull would have been in pieces not because it is weaker but because it would have flooded and been rolled around on the rocks full of water instead of retaining enough buoyancy to get up above the surf line. Oh, come ON. That boat (SG) is ballasted to a displacement of 14400 lbs. The steel version is ballasted to a displacement of 14400 lbs. Both versions have all inside ballast. The keel shoes are 1" thick plate in both cases. The chine bars are 3/4" thick rod. The frames are 2 1/2" by 1/4" flat bar. Can you explain to me how this ballast mysteriously changes between a steel hull and an aluminium hull? How the aluminium hull managed to keep water out that a steel hull would have allowed in? Why would a 4mm thick steel hull plate be ruptured, allowing water ingress, when a 6mm aluminium plate hull kept the water out? This argument has no credibility. BTW, I have a full set of blueprints for a Colvin Witch hull so I do know how they're built. Obviously, anything can happen in any accident but I've seen enough damaged boats to have great respect for aluminum. I have enough understanding of the materials characteristics to design boats like this one: http://home.maine.rr.com/rlma/WHOIrv.htm Nice boat. I have 2 30', 6 tonne alum boats, 4 jet barges and a number of other small craft. However I also have steel vessels up to 6500 tonnes. Any impact that an aluminium boat will withstand, a steel boat will also withstand, and likely with considerably less structural deformation. PDW |
#18
|
|||
|
|||
Sara Gamp comes ashore
On Fri, 11 Nov 2005 09:56:57 +0000, Iain Hibbert
wrote: On Fri, 11 Nov 2005 01:33:03 -0500, rhys wrote: The break point of steel in term of "too heavy" is around 40 feet for a cruiser, but you can get a "leisurely" sailer that is pretty bulletproof in that range if you are willing to wield a chipping hammer and stay on top of the paint schedule. I would contest this slightly, I have a 31' steel boat that weighs in at (allegedly - I never checked) 6,5 tonnes, which is not really any more than a similar sized cruiser of other materials. There are certainly much heavier wooden and plastic boats out there.. By contrast, my 34' 1973 GRP cruiser-racer is 4.5 tonnes. I check it in the slings at haulout, because too much weight affects my trim. 6.5 tonnes for a 31' steel boat is, to my mind, pretty light. Of course, a 31' foot cruiser in steel is pretty rare in itself. My hull is mostly 3mm I think, multi-chine with plenty of framing and after 20 years and 2 atlantic crossings the external plates are not significantly buckled except in a couple of places under the waterline where I think the hard stuff has been in contact. Out of curiosity, what are your interior hull coatings and how have they held up and/or been maintained? I am always interested in hearing how various coatings fair with heavy usage. In your comment, you seem to be implying that a cruiser and a leisureley sailor would be different things? If so then maybe a steel yacht under 40' would be too leisurely for you, but I find fast boats are uncomfortable and noisy when I'm trying to sleep. No, I am actually implying that certain steel boats in the "motorsailer" category are somewhat undercanvassed in that they sometimes don't move effectively in the light airs typical of coastal work, the Great Lakes, etc. Conversely, give them 20 knots and they'll move smartly. The debate between "fast, light cruiser derived from racing notions to get out of the way of weather" versus "heavy, spacious full-keeler that can heave to and endure" is informative and I have no particular axe...or metal...to grind. Currently, I favour safety, comfort and that abstract quality of "sea-kindliness" over pure zip, like you find in, say, the larger J-Boats marketed as cruisers. But that's because if I have to save for a larger J-Boat, I'll never go a-voyaging. G R. |
#19
|
|||
|
|||
Sara Gamp comes ashore
On Sat, 12 Nov 2005 04:56:46 -0500, rhys wrote:
By contrast, my 34' 1973 GRP cruiser-racer is 4.5 tonnes. cruiser racer.. Of course, a 31' foot cruiser in steel is pretty rare in itself. I'll excuse you because you are on the other side of the atlantic, but its a common enough size here. In fact I bought it on your side and got a good deal because presumably nobody wanted such a small boat, heh. actually, they did put a large enough rig on mine (12m mast) and I found in a marina with other boats the same size, my mast was one of the tallest excepting the fractional rigs, so I guess they may have worried aobut the weight. I have thought it might be interesting to offload all the junk and see how we sail but that could take days. Out of curiosity, what are your interior hull coatings and how have they held up and/or been maintained? I am always interested in hearing how various coatings fair with heavy usage. Inside is still pretty good, I believe it was sandblasted and sprayed with coal tar epoxy inside when new. I had to deal with a few crusty bits under the floorboards last year (very difficult to get to) and it didnt look as if any maintenance had been done before down there. In a couple of high usage areas (bottom of cockpit locker, and anchor locker) I have had to cut and weld, but the worst continual rust problems I get are on the inside edge of the inwardly leaning 4" high toe rail where the deck is only about 8" wide behind the cockpit coaming and you can't even see any rust without a small mirror never mind cleaning it off, poor design. -- http://maps.google.com/maps?q=irelan...244,0.0822&t=k |
#20
|
|||
|
|||
Sara Gamp comes ashore
On Sat, 12 Nov 2005 12:53:15 +0000, Iain Hibbert
wrote: On Sat, 12 Nov 2005 04:56:46 -0500, rhys wrote: By contrast, my 34' 1973 GRP cruiser-racer is 4.5 tonnes. cruiser racer.. Of course, a 31' foot cruiser in steel is pretty rare in itself. I'll excuse you because you are on the other side of the atlantic, but its a common enough size here. In fact I bought it on your side and got a good deal because presumably nobody wanted such a small boat, heh. You rarely see it here, admittedly, although a local couple and their kids circumnavigated a few years back in a steel, junk-rigged 30 footer called "Lorcha". Out of curiosity, what are your interior hull coatings and how have they held up and/or been maintained? I am always interested in hearing how various coatings fair with heavy usage. Inside is still pretty good, I believe it was sandblasted and sprayed with coal tar epoxy inside when new. I had to deal with a few crusty bits under the floorboards last year (very difficult to get to) and it didnt look as if any maintenance had been done before down there. In a couple of high usage areas (bottom of cockpit locker, and anchor locker) I have had to cut and weld, but the worst continual rust problems I get are on the inside edge of the inwardly leaning 4" high toe rail where the deck is only about 8" wide behind the cockpit coaming and you can't even see any rust without a small mirror never mind cleaning it off, poor design. That's sometimes the problem with steel. Designer assume you've got ordinary seamen available to chip and paint constantly. That looks like Fenit, Co. Kerry, facing the Dingle Peninsula. I know the area well, but as a cyclist, not a sailor. There's at least four bike shops in Tralee, and all seem to be owned by (if I recall) a family called Cable. Is that dockage pretty rough? It looks a bit exposed. R. |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Sara Gamp (look quick) | Cruising |