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Old 06 April 2006, 14:07   #11
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Quote:
Originally Posted by Caledonia
I recon that being able to run the boat onto a beach is a very attractive atribute. I've used a 18ft aluminium boat for 10 years on a fish farm where we run the boat onto the beach at the shore base every time we use it - without fear of damaging the structure or the gelcoat.
Aluminium will withstand severe abuse better than GRP, and for a small minority of people it will make aluminium a better choice.

For normal use aluminium and GRP are both more than adequately robust.

I'm not convinced that long life and low maintenance are real benefits of Ali over GRP either. GRP hulls do not require much maintenance, and they are not noted for wearing out either! While we're at it GRP hulls aren't exactly difficult to customise, and I'm not sure that Aluminium if any more envornmentally friendly than GRP (just different!).

Although I'm sounding pretty begative, I don't have anything against alumimium. I'm just not convinced that for many applications it has any advantages.

John
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Old 06 April 2006, 14:35   #12
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Hi Calendonia,

I work on an ali RBB. There are a couple of previous posts where it has been discussed briefly. See:

Single outdrive, any differences from single o/b? Advice

As we use it for a commercial application where beaching and general abuse is common (heavy lead-lined nets, trawls etc smashing around the deck), ali was a major factor over the GRP dories and RIBs that we had operated in the past.

However, the major thing that won us over from GRP was the ease of customisation. You can move major components eg, lockers, console, seats around with little hassle. Rather than having a limited choice, or the major expense of a one off GRP mould. Also on a RBB you can have D shaped sponson to win more internal deck space. Additionally, once a hull shape has been designed it can readily be adapted for a range of different propoulsion units, for the same reason. I also like the fact that the fuel tanks could be constructed under the deck as an integral part of the hull structure on our vessel.

I guess that I am saying for a commercial application or where a vessel needs to be robust ali is a good way to go.

I'm not sure it is any better for the environment than GRP (given the energy needed for ali production), but it does probably last a lot longer (given the right cathodic protection).

Good luck with your project. Having looked around the market there are bugger all <7m boats that can be used as heavy duty workboats, so if you come up with a ali RIB in that size range I would have thought you'd get a fair bit of interest.

t
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Old 06 April 2006, 22:47   #13
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Re: aluminum hulls

Being as I own a aluminum rib I feel eminently qualified to weigh in on this thread regarding glass vs. aluminum. As to strength, boy that's a good question... I think fiberglas probably has it's advantages and aluminum has it's advantages, one dents, one doesn't, one will shock the shit out of you, one won't, so on and so forth. In the U.S. aluminum probably has a higher material cost. I can tell you by experience Aluminum is not a colder material than glass just quicker to react, heats up faster and cools off quicker, temperature is temperature. If the sun is shining on the hull it's going to feel hotter, if it's not, colder. Noisier? Would probably depend upon hull thickness/strength/construction in both instances, "War Machine" generates the least amount of hull noise of any boat I've ever rode upon but the hull is 3/8 plate overall and 1/2 at the keel, a one off, she is overbuilt by anyone's standards.
A great benefit is customization you can just weld, throughbolt, and drill and tap holes just about anywhere, making modifications easy, inboard jet today? How about outboard prop tomorrow? Eliminate rotten stringers and transom as a future potential problem with aluminum. Is it better? A well built glass boat can be extremely tough just as a well built aluminum boat can be extremely tough. Choose your poison. My final comment is that my current rib handles waves better than any of the glass boats I have had,(4 hard, 5 rib) it also has greater weight, length and hull thickness than all of the prevous ones, ultimately if you want the ride, you must add length and weight, that's why AIRCRAFT CARRIERS do so well in the slop!
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Old 07 April 2006, 09:42   #14
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Ali hulls are very popular here. I would say more cause of the constant beaching and logs in the water around our coast. We have quite a few manufacturers here which helps to keep the cost down.
In perspective you could build a similiar hull to hurricanes 733, customize the deck layout add hatches or whatever for the same price if not cheaper.
Just because you get an ali hull does not mean that it will last forever, a bad design can cause it to crack and fall apart. I believe it really depends on the builder/design
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Old 07 April 2006, 11:27   #15
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Thanks very much for the comments guys, both ways.

John, on the environmental subject, think i might have been pushing it a bit on that one!!

I suppose that the nagging thaught in the back of my mind is that an Aluminium boat is less desirable to the boating public than an identical GRP one. But I think that's less true in a commercial market.

For some people the ease of modification is a real bonus and I do think that it is significantly easier than GRP.

Have a good weekend on the water everyone!

Andrew
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Old 07 April 2006, 15:51   #16
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Quote:
Originally Posted by Caledonia
I suppose that the nagging thaught in the back of my mind is that an Aluminium boat is less desirable to the boating public than an identical GRP one. But I think that's less true in a commercial market.
Wouldn't see why, unless it's based on misperceptions (Al is colder/hotter, Al is more prone to lightning strikes, Al will dorrode away in salt water, etc.)


Quote:
For some people the ease of modification is a real bonus and I do think that it is significantly easier than GRP.
Not sure this is true, either. For instance, you can, with reasonably thick al plate, bolt just about anything on anywhere. With GRP, you're going to have to go through making up and installing backing plates and such. Want to move something? Unbolt it, drill a few holes, and re-bolt. Want to create a new structure? Take it to a welding shop (or do it yourself if you're handy) and have at it.

I do like the fact that Al is stronger for a given weight than glas, and has none of the chipping/peeling/crazing problems that gelcoated GRP does. And a lot less of the cracking problems (though, to be fair, a poorly designed boat in either material will show a greater propensity for that one.)

My boat is no noisier (that I can tell, anyway) than my buddy's Pro16. It certainly is no colder (we dive in low 50 degree water, so I may not really notice that one anyway.) It does not get uncomfortably hot in the summer. It does not have dive-equipment-caused chips and dings, either. And the one floating whatever-it-was that I hit did nothing more than leave a very slight ding in the hull, where a glas hull would most likely have needed some fairly major repair.

Luck;

jky
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Old 09 April 2006, 09:09   #17
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Quote:
Originally Posted by jyasaki
Wouldn't see why, unless it's based on misperceptions (Al is colder/hotter, Al is more prone to lightning strikes, Al will dorrode away in salt water, etc.)





.)

My boat is no noisier (that I can tell, anyway) than my buddy's Pro16. It certainly is no colder (we dive in low 50 degree water, so I may not really notice that one anyway.) It does not get uncomfortably hot in the summer. It does not have dive-equipment-caused chips and dings, either. And the one floating whatever-it-was that I hit did nothing more than leave a very slight ding in the hull, where a glas hull would most likely have needed some fairly major repair.

Luck;

jky
Nice looking rig jyasaki, looks very well built. I looked into buying a Polaris for a while, their boats exhibit quality. I Like the outboard bracket. I have to agree with your comments regarding aluminum boats, they have a lot of advantages. Much sturdier overall as aluminum is stiffer than an equivalent thickness of glass. I do not think a glass boat is anywhere as easy to modify as an aluminum hull, I have been having great fun doing extensive changes to my current boat, fill a hole? weld it shut, sand it off, paint, done! Not so easy with glass. A much much more flexible platform for innovation. Most aluminum boats tend to have a industrial look about them (especially mine) due to being made primarily out of plate or sheet, so none of the pleasing curves of the glass molded boats but someone will overcome that eventually. put up more pictures if you have them.
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Old 09 April 2006, 17:49   #18
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Naiad

I was very impressed by these boats - there seem to be a couple around the UK
Advert . Their website is here
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Old 11 April 2006, 12:15   #19
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Thanks to everyone who's commented. I'll let you know if the project takes off.
Cheers
Andrew
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