Aluminum Catamaran Build

[Manateeman]

We looked at the build of the performance catamaran. I think this is a good example of one way to build a boat. Speedy construction and light weight.
If you visit builders who construct commercial vessels, you will see quite a different approach...very heavy members and greater strength in the welds.
Somewhere in the middle are yachts in France and the Netherlands.
Full strength aluminum welding is not a simple skill.
The lighter you wish the vessel to be, the greater the difficulty to weld.
I sincerely doubt the vessel in this video would pass commercial inspection in several countries. Is aluminum suitable for such a high performance boat ?
It is, IF the entire construction process is done with extreme care. We just don’t see this level of professional welding in this video. In the end, you will find that aluminum requires controlled conditions.. indoors, not in an open shed... and a great deal of time. You get what you pay for. Aluminum is not the perfect Boatbuilding material. There is NO perfect material, method of construction, nor design. Commercial aluminum vessels bend, crack, leak, pit, and corrode. Every attempt to lighten the weight or speed up the construction process Increases the frequency of failure. Repairs become increasingly difficult.
Think aircraft. After x amount of time, they strip them to bare bones and examine every inch. Can you build a performance catamaran as light and strong as a commercial aircraft. Certainly. If you have the engineering, a highly experienced crew, the proper shop, and a huge amount of cash. We are NOT saying don’t do it...just understand what the consequences might be if you have underestimated the difficulties and overestimated your skills.
It’s like experimental aircraft. We love them. They push the creative, but there is a difference with vessels. If you fail, someone might have to put their life on the line to rescue you.
If you feel the need for speed, fine. No mayday calls, no EPIRB, no asking for rescue...are you a gentleman willing to go down with the ship? We’ve no problem with that, but understand as a professional mariner, I’m legally obligated to rescue with only one exemption. Again, we urge you to consider carefully, the complete consequences of what you propose to do.
Happy trails to you.
Captain Mark and the manatee crew.

[Sand crab]

An outfit in Port Angeles WA builds some pretty big alu power cats.

https://brixmarine.com/


And the same for these guys in Port Townsend, WA.

https://www.aciboats.com/ourboats/commercial


Couldn't hurt to call

[Constellation49]

We started building our aluminum monohull sailboat in March 25th 2016. We planned it for two year prior to that. Our expected launch date is spring 2026 and will transition from our home to the boat by October 16th 2026 on that day we will begin transit down river to the US GOM.

We haven’t worked on it continuously over that period. It is real similar to a production boat from Europe that we admired the lines of. I am fortunate because my wife is a mechanical engineer with her license. She has the entire yacht modeled in Rhino and performed all the stability calculations with Orca3d. We call the design a Constellation 49. We registered her in 2019 with the USCG and named her S/V Vela. Vela is a constellation in the Southern Hemisphere it is the sail of the sailboat Argo.

We purchased the aluminum from Phoenix Metals which is a large distributor primarily central to east USA. The majority of our plate was CNC cut on their large table. We have various grades of material the hull plating is all 5086, 5052 and 5356. The thickness vary from 1/2” to 3/16” thicker being on bottom and getting thinner as it gets above the waterline.

We have performed all the welding, machining, drape Moulding of acrylic. The only thing we farmed out was the machining of the rudder shaft because our lathe was to small.

We presently have 98% of all aluminum fabrication complete. We are almost complete install all glass and acrylic. I am also installing the EPdM rubber insulation inside the hull. We are looking good on our schedule. We should take delivery of our mast, boom and standing rigging by the end of this year from a reputable mast manufacturer here in USA.

I would highly recommend TIg welding all the hull plating and any welds you plan to grind down smooth. We have both a Miller Dynasty 400 and a Millermatic 350P with push pull gun.

A good website I can recommend is Odyssey yachts. He built an aluminum yacht several years ago and is presently out cruising with it. Good useful information on there.

[Sand crab]

Constellation, so cool
And where is your build?

[noelex 77]

Originally Posted by Constellation49

We started building our aluminum monohull sailboat in March 25th 2016. We planned it for two year prior to that. Our expected launch date is spring 2026 and will transition from our home to the boat by October 16th 2026 on that day we will begin transit down river to the US GOM. .

Nice looking boat .

[Constellation49]

Originally Posted by Sand crab

Constellation, so cool
And where is your build?

Building it in North Louisiana in a large airplane hanger we own at the local airport. Launch site is about 5 miles in local river that is navigable to the US GOM. One bridge has a limitation of 72’6” air draft our air draft will be 71’ 6” no antennas.

We already have the trailer built underneath and have pulled it out of hanger once to reposition in the center to get the useable height above it. He built the hull on one side of the hanger upside then flipped it. Plan will be to use the large farm tractor to get it to launch site where there is a concrete boat ramp.

[Manateeman]

All the hull TIG welded. Miller 400. In house licensed engineering.
The manatee crew tip their hats...a VERY nice job.
Congratulations. Beautiful vessel.
Captain Mark and crew

[elsener44]

Yes I have talked to Jamie from Jupiter and seen footage of the tabbing process. It does make sense to help keeping things somewhat straight

[elsener44]

Thank for the info. I will definitely check them out!

[elsener44]

Very nice looking build! I also plan on getting as much cnc cut as possible and will check with Phoenix as well. Thank you

[elsener44]

That's true there is no perfect material. The mumby cats have around for over 20 years and are very strong and stiff boats that had encounters with reefs and rocks. So far they haven't had any catastrophic failures. The plates have a full penetrating weld and a full weld on the backside where plates meet. The bow is 6mm and the hull is 4mm, only the top is 3mm. If I had the cash I would go with the explorer 52 cat but this is as good as it gets for me. Definitely feel better about a mumby then a fiberglass production boat.
After having welded alu now I have to say it really isn't that difficult if you follow industry standards and know how to handle a welder.
i get with all the info out there it can seem a little daunting but for me personally it's not. Best to try welding alu for a few days and then decide if you're confident with a project like this. Nothing beats hands on experience

[mcarthur]

I assume the only way to tell what alu you have - 5 series, 6 series and the subvariants - is via a metallurgist? Any ideas how to find one?!

[elsener44]

Originally Posted by Constellation49

We started building our aluminum monohull sailboat in March 25th 2016. We planned it for two year prior to that. Our expected launch date is spring 2026 and will transition from our home to the boat by October 16th 2026 on that day we will begin transit down river to the US GOM.

We haven’t worked on it continuously over that period. It is real similar to a production boat from Europe that we admired the lines of. I am fortunate because my wife is a mechanical engineer with her license. She has the entire yacht modeled in Rhino and performed all the stability calculations with Orca3d. We call the design a Constellation 49. We registered her in 2019 with the USCG and named her S/V Vela. Vela is a constellation in the Southern Hemisphere it is the sail of the sailboat Argo.

We purchased the aluminum from Phoenix Metals which is a large distributor primarily central to east USA. The majority of our plate was CNC cut on their large table. We have various grades of material the hull plating is all 5086, 5052 and 5356. The thickness vary from 1/2” to 3/16” thicker being on bottom and getting thinner as it gets above the waterline.

We have performed all the welding, machining, drape Moulding of acrylic. The only thing we farmed out was the machining of the rudder shaft because our lathe was to small.

We presently have 98% of all aluminum fabrication complete. We are almost complete install all glass and acrylic. I am also installing the EPdM rubber insulation inside the hull. We are looking good on our schedule. We should take delivery of our mast, boom and standing rigging by the end of this year from a reputable mast manufacturer here in USA.

I would highly recommend TIg welding all the hull plating and any welds you plan to grind down smooth. We have both a Miller Dynasty 400 and a Millermatic 350P with push pull gun.

A good website I can recommend is Odyssey yachts. He built an aluminum yacht several years ago and is presently out cruising with it. Good useful information on there.

It is a very nice looking boat you built. For sure capable of sailing high latitudes as well. Are you going to stick rubber insulation verus spray foam to insulate? I am leaning towards the Millermatic as well. The newer machines with various start and finishing computerized programs don't justify the slower TIG specially when grinding flush with the hull for my application. I will have the appropriate space between plates for a full weld penetration on the outside and a full weld on the backside. I looked at both options myself and Tim the architect advised me not to bother with TIG.

[elsener44]

Originally Posted by mcarthur

I assume the only way to tell what alu you have - 5 series, 6 series and the subvariants - is via a metallurgist? Any ideas how to find one?!

In the US you can send samples to a lab but the better option is to request certification like ASSET cert.
Here's a good discussion about Alu purchase and making sure you getr what you pay for.
https://www.boatdesign.net/threads/w...um-from.49764/

[ozolli]

We ask for a 3.1 MTR on each order. Unless we make parts which are specifically surveyed (DNV, LR, ABS) this is sufficient.