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Old 26-01-2012, 11:47   #31
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Re: Cost of Aluminum Hull and Deck ?

Correct. First spotweld the sheets together and the final welding has to follow in certain stages to keep the sheets in a straight form. For that certain welding schemes are composed.
Aluminium is very sensitive to welding in the correct sequence.
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Old 26-01-2012, 12:19   #32
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Re: Cost of Aluminum Hull and Deck ?

I think the original poster should take a few courses at a community college and see if welding is really too difficult.
Labor is much more expensive than materials.
And even if in the end you don't build it yourself, you have a much better understanding of it, which will help you evaluate the quality and price of the work.
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Old 26-01-2012, 13:06   #33
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Re: Cost of Aluminum Hull and Deck ?

Frameless building is absolutely the heaviest way to build a boat. I've never been a fan of it. It may or may not take less labor--the plates are much thicker than designs with frames, and so fitting plates and welding each seam and butt would take longer than a framed boat. Of course, for a framed boat, you have to make the frames first, and that is a lot of labor. But the boat with frames, in the end, will be much lighter.

Typically, in metal boats, the metal structure is about a third of the total boat weight, and of that weight with a framed design, 2/3rds is the plating, and 1/3rd is the framing. If you want to make the boat lighter, add more frames so that the plating thickness can be thinner. That is axiomatic in metal boat and ship construction--one of the first lessons you learn in metal boat building. With frameless construction, I would not be surprised if you have to increase the thickness of the plating by a factor of 2 at least, so that would make the metal hull and deck structure about 44% of displacement. That leaves less weight for other things that go into the boat. That is a high percentage.

Something to remember about converting plans from steel to aluminum is that a lot of metal boat structures are stiffness critical as well as strength critical. Aluminum is only 1/3rd the weight of steel, but it is also 1/3rd the stiffness. So structure for structure, what usually happens is that thicknesses are doubled in the conversion from steel to aluminum, and frames are made somewhat deeper. In the end, aluminum boats come out about half the weight or so of steel boats, all other things being equal.

Finally, another thing that affects the overall weight, strength and stiffness of metal boats is that in steel construction, you can consider that the welds are as strong as the virgin material. No extra material is required to make up for lost strength or stiffness due to welding, because there isn't any loss. Not so with aluminum. Welded aluminum can be roughly one half to three quarters as strong as the virgin metal, depending on alloy and temper, and so you have to compensate by having extra thickness in the welded structures. You always design to the welded strength and stiffness.

I hope that is all worthwhile.

Eric
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Old 26-01-2012, 13:29   #34
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Re: Cost of Aluminum Hull and Deck ?

Frameless buidling does not mean that frames are or should be absent. Frameless building is actually only feasible when building a multi or hard chine boat. That the platethickness should be doubled is not really required. Reinforcements are required in certain spots where stresses occur or designstrength is needed. Frames, in way of bulkheads and internal parts may take over the obligatory traditional framing.

Aluminium is a total different story. Aluminium requires framing whether multichine or not.
I know of a yachtbuilder in Holland specialised in Super' s who builds 45 metres out of 4mm plates. Not really my choice but he can get away with it by placing lot's of frames and internal reinforcements in order to prevent the buckling of platematerial. And alu is certainly very sensitive to buckling and denting.
Next to that I would not weld aluminium but glue and rivet. The Germans knew this process already in WWII when constructing the "Flieger boote" - special fast craft to pick up pilots from shot down plane in the Nort Sea.
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Old 26-01-2012, 15:18   #35
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Re: Cost of Aluminum Hull and Deck ?

Welding has come a long way since WW 2,
Back then it was a fairly new process,
Everything was rivetted back then, Including big ships and buildings,

The Liberty ships were the first welded ships I believe, and they had a rivetted band to stop them cracking in half,

All long welds are back stepped to avoid distortion, even aluminium,
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Old 26-01-2012, 15:43   #36
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Re: Cost of Aluminum Hull and Deck ?

Not steel. Aluminium yes, mostly.

Glueing and rivetting came again in the picture on the 1988 Yachtbuilding Seminar at HISWA, Amsterdam when I discussed this topic with Wolter Huisman who at that time had build the Flyer for Conny Van Rietschoten. Carbon etc, was at that era not in the picture but Huisman said at that meeting that if he had to build another alu yacht for pure racing purposes he would definitely consider the way of glueing/rivetting. Due to the known aspects of alu. For the same reason, one uses the same technique in the construction of aircraft.
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Old 26-01-2012, 19:00   #37
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Re: Cost of Aluminum Hull and Deck ?

Just finishing the build of 39ft aluminum. It is just like a marriage. Really hard to be exact on price, timing, deadlines... We are filming TV series for Discovery about that boatbuild and sailing from Canada across the North Atlantic to EU.

FB page about the boatbuild is SeaRover Julius - A TransAtlantic Voyage | Facebook

"Like" us and follow the last tasks being performed before the seatrials this summer;-)
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Old 27-01-2012, 04:26   #38
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Re: Cost of Aluminum Hull and Deck ?

Quote:
Originally Posted by MacG View Post
Frameless buidling does not mean that frames are or should be absent. Frameless building is actually only feasible when building a multi or hard chine boat. That the platethickness should be doubled is not really required. Reinforcements are required in certain spots where stresses occur or designstrength is needed. Frames, in way of bulkheads and internal parts may take over the obligatory traditional framing.

Aluminium is a total different story. Aluminium requires framing whether multichine or not.
That doesn't make sense: "Frameless" means no frames. There are builders who build aluminum chined boats which have only bulkheads, no frames of any sort. That is frameless construction. And in order for the plates on such boats to not buckle, the plates have to be quite thick. That is why such boats are heavy. This applies to any type of material, whether aluminum, steel, or plywood.

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Old 27-01-2012, 04:49   #39
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Re: Cost of Aluminum Hull and Deck ?

I've built many Joe Adam's designed yachts in round bilge and chine steel and aluminium mainly A45's. I cannot imagine doing any of them as 'frameless'!! The stringers cross frames and bulkheads to form a grid that can be faired prior to sheeting. These frames are the connection point for subsequent fit-out.

It is this grid that gives the 'panel strength' that is required and it is the stringers that give the longitudal strength.

Frameless would mean building over a ply form like a strip plank boat and removing the forms later. This works in a strip or foam construction as furniture etc can be glass taped to the hull giving further local strength.

Frameless would require tabs be welded internally to connect furniture etc..

Much simpler and cheaper for any amateur is to go down the ring frame method methinks....Cheers
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Old 29-01-2012, 10:04   #40
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Re: Cost of Aluminum Hull and Deck ?

Building that way doesn' t make any sense to me. Mulitchine can do without longitudinals but needs some structural bulkheads. And a keel-sole/motorfoundation, maststep etc.
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Old 29-01-2012, 10:25   #41
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Re: Cost of Aluminum Hull and Deck ?

Are we talking about an aluminum deck on a steel hull? We have friends with a Roberts 495 built by Topper Hermonson that is well done. Our steel boat has steel decks, and that is where 98 percent of the maintenance is. If I had thought about it then, I would have made the decks out of stainless. Then again 28 years ago plasma cutters were in there infancy and very expensive. It would have been quite difficult to build it.
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Old 29-01-2012, 10:26   #42
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Re: Cost of Aluminum Hull and Deck ?

Worked as operations manager for an alum boat builder. High speed rec and military stuff. Small boats to 38 ft but mostly 32 ft and less. No frames, heavy logitudinals. These boats could typically do 60 MPH and do a hard over hairpin turn at that speed. Very rigid. It's all about design really, not whether it has frames or not. Typically these boats would have a few bulkheads just by necessity to separate the fuel compartment etc. any extruded piece used athwartships to attach decks etc could be considered a frame I suppose!
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Old 29-01-2012, 10:33   #43
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Re: Cost of Aluminum Hull and Deck ?

There are unfinished steel and aluminum hull boats of different types on Yachtworld. Seems like the way to go. Assuming survey etc.
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Old 29-01-2012, 13:08   #44
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Re: Cost of Aluminum Hull and Deck ?

Stainless just isn't the go because of cracking however putting stainless where wear points are is a good idea.

Bulkheads should be part of the design for water tight compartment divisions, of course there are multitudes of design choices to be had.

Van-de-stadt are extremely good designs check them out.
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Old 29-01-2012, 13:19   #45
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Re: Cost of Aluminum Hull and Deck ?

Bulkheads are needed to accommodate sections. You can/may use sections as potential and structural reinforcements. In wooden boat design you can use the floor-sections and berths, pantry and drawers into extra stiffeners of the hull. Where access is needed you make manholes. Same is do-able with FRP/plywood bonds but keep in mind that the polyester (FRP) bond between plywood and hull materials is not eternal but starts separate after 25+ years.
In cold forming (one could call it woodcore) it is practised.
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