Aluminum Catamaran Build

[elsener44]

Hello, I am in the planning stages of building a 48 foot Mumby Alu Cat in San Diego. I got the site secured and I am in the process of sourcing materials.
I will use Selium 5383 for the hull and deck which is 4mm hull and 3mm deck.
For the stringers etc it wil be 6061 grade and the filler material I plan on using 5356.
I would love any input on where you would recommend I should purchase the materials in bulk obviously. I do have the order list from the architect.
Also any input if someone has experience as far as using anz different materials as far as fillers for the different grades goes.
I appreciate any feedback in regards to this upcoming build. Cheers

[ozolli]

5383? Most probably 5083.

[elsener44]

I know 5083 is the most common. In Europe they do use 5383 for some of the builds and if the price difference isn't that much and I can get the 5383 in North America I would go with the 5383 as it has slightly better qualities.

[Chotu]

Although I can’t help with specifics, when you are ordering hull materials, go straight to the manufacturer.

It’s still a fairly small order for them, but they may often have leftovers or other deals.

I got a fantastic deal on the core of my boat going straight to Gurit, the manufacturer. Did well on glass too. They spun it to fill my order at the factory.

The order is big enough that you should be able to do the same with your aluminum.

[elsener44]

OK great thanks. I take it Gurit doesn't manufacture alu?

[Chotu]

Originally Posted by elsener44

OK great thanks. I take it Gurit doesn't manufacture alu?

No, they definitely don’t. They manufacture Corecell structural foam and a bunch of other fiberglass related products.

I don’t know why the word Alcoa is coming to my mind, but that one’s probably too big. A nice medium size manufacturer is what you need. Maybe you can Google local aluminum manufacturers nearby you to start with.

Possibly, these days, it might also all be imported from China. So maybe you can find out who the importers are. Someone may come along in the thread I know a source, but this is out of my wheelhouse as they say these days. I just wanted to make sure you remember to go to the source. Because if you go to retail, you’ll pay significantly more.

[elsener44]

I found one that seems to have 5383 plates. Anyone have any experience with them?
piercealuminum.com

[hpeer]

FWIW ....
There is a place in NJ that has a lot of stock metal usually at very good price.

Occasionally they have some left over at very good prices.

It is a long shot but may be worth a look.

They have a complete inventory online.

Google Fazio Metals should get you there. You want the Glassboro branch.

[elsener44]

Thanks, I will check them out!

[Dave_S]

Originally Posted by elsener44

Hello, I am in the planning stages of building a 48 foot Mumby Alu Cat in San Diego. I got the site secured and I am in the process of sourcing materials.
I will use Selium 5383 for the hull and deck which is 4mm hull and 3mm deck.
For the stringers etc it wil be 6061 grade and the filler material I plan on using 5356.
I would love any input on where you would recommend I should purchase the materials in bulk obviously. I do have the order list from the architect.
Also any input if someone has experience as far as using anz different materials as far as fillers for the different grades goes.
I appreciate any feedback in regards to this upcoming build. Cheers

This might be a good start.
https://www.hobartbrothers.com/downl...lecti_1lOo.pdf

[elsener44]

Thank you Dave,
Yes very helpful. Looks like the 5356 filler works perfect for both the 5383 and 6061. The only point where I get a C rating is on corrosion when welding 6061 with other 6061 but that's all inside non exposed and other than extending a stringer I won't be welding those 2 together anyways.
I didn't see another filler that looks like it will do better overall unless you know a trade secret that's not listed in the chart
Thanks again
Cheers

[rocks]

Hi We order aluminium from the mill in Brisbane. They have a min MOQ of 250 kg. That 250 kg can be made up of different product. Do not buy aluminium China you will not get what you order.

[noelex 77]

Congratulations on the build.

Keep in mind it takes great skill to weld aluminium as thin as this without distortion, especially 3mm. One comment often made is the extra fairing compound and paint needed can result in a finished structure that is no lighter than starting with slightly thicker aluminium material. The stiffness rises roughly as the cube of the thickness so small differences In thickness make a appreciable difference to the final structure.

6061 has significantly lower corrosion resistance than any of the five series aluminiums so try and limit its use as much as possible. These days 6061 can be replaced with computer cut 5383 or 5083 for many applications. Unfortunately, many older designs use T shaped stringers and the only practical way of producing these shapes is via an extrusion. This is not possible with the five series. Nevertheless, all flat bar and T shaped bulkheads can be cut from 5 series, reducing the corrosion potential.

The photo below is an example. All the aluminium shown including the stringers is 5 series.

6061 is also an older aluminium series that has largely been replaced in more critical situations with newer versions of the six series such as 6063, 6082 etc. These are typically more costly but have more suitable properties such as higher corrosion resistance (although nowhere near the 5 series) and strength.

The take home message is do plenty of research before ordering materials.

[ozolli]

It's also worth noting that 6082 loses 40% of its mechanical properties when welded, so basically gets down to 5 series mechanical properties.

[Manateeman]

There are a lot of yards building in aluminum for the oil field in the Gulf and for fishing in Alaska. It will be worth your time and money to actually talk to professional boatbuilders who have in depth experience in aluminum.
Happy trails.
Captain Mark and the manatee crew.