How a proa works / I'm making a 45ft one in Aluminum

Hi Smart boat engineers

First let me announce that I am building a proa in Alu based on plans for madness by John C. Harris.
Those plans are obviously not for an alu boat so I'm doing some changes but not allot to the boatdesign to compensate for this. Biggest change is the size
It's going to be a wopping 45ft long!

some of the other hanges are:
Some sort of viewing portal or a light bridge in the living compartment
Widening of the pod to accomodate for a regular 140cm wide matress.
Sliding hatch instead of hinging like the original plans call for.
many many more to come

Second of all I made a video explaining how a proa works and why I chose this design instead of any other conventional boat:


Go subscribe if you are eager to see me fail or succeed. entertaining in both ways.
I also have an instagram account , you can find me under the same name as my channel: Kingherog

I am not a boatbuilder, nor a welder for profession nor do I have any experience in this practice but I'm a person who likes to dive headfirst into challenges with full knowledge that I might fail and I'm ok with that.

I'm open for critique but if you're going to be a fatalist then know that I'm not inclined to listen too you because I'm not arrogant and 100 percent sure this will work and I am in no need for more insecurities with this project.
Just ask questions and make suggestions. Diving head first doesn't mean I don't think things through but I haven't thought of everything in advance off course!

I have certain specific questions I will ask in the future but this is basically announcing my plans and letting everybody who's interested know what I'm doing!

Wish me luck!
I probably need it!

Ps
I attached some pictures showing at what stage I am at this specific moment

 

Firstly - well done and good luck....and welcome to the forum.

However, secondly and should be firstly - you need to go learn how to weld aluminium. The welds you show, are shocking!
Too much shoot, implies so much, - basic QA for set up, gas settings, volts/amps etc etc
No prep's
No returns..
and craters/cold blobs...localised over heating
etc etc

I understand this is your first time....and to be expected.
However, if you wish to sail, in safety, you need to get someone else to weld. It takes many years to produce good quality aluminium welds consistently and with quality.

 

First of all. Thank you for your concern!

Here is all of my knowledge and thoughts about my welds and practice:

Gas flow is 16L a min
Using an esab 235ic weld machine with the voltage settings I start with using the chart inside the welding machine and then fine-tune too the hissing sound.

My research in papers from Miller and Lincoln etc learned me that sooth isn't that uncommon with high magnesium content weld wire like 5356. As long as the weld bead itself is nice and shiny.
I clean with acetone and wirebrush with a stainless wire brush either by hand or on the grinder when doing bigger longer pieces.

At the end of every weld bead I return a little bit to fill in the crater and I design most of the weld joint to be lapjoints since looking up welding aluminum shows that the weld itself isn't as strong as the original material and coldcracking is common and a lap weld is a good way to avoid that. Even though 5356 is less prone to cracking.

Most of the pieces are welded in with mostly Tack welds. Leaving the longer beads for when all the nesecary pieces are in place to check that the form is within reasonable bounds.

I've set this piece up in a cradle which I will tumble to make it easier for me to get into an easier weld position when doing the big longer beads.
Not too long to avoid distortion.

I'm willing to learn but I learn by doing. Ideally some welder comes over to help and shows me the tricks.

Both the hull are designed with watertight bulkheads.

I do share your concern for good welding quality and therefore have purchased a better machine.

I hope this information shows that I've done my research and don't do all of this blindly.
I'm taking my time to learn and improve! No need to hurry with this project. I've got the time!

But again
Thanks for the concern!

 

Pororoca has also started a thread on the YBW Forum here -
How a proa works/ building a 45ft aluminum proa https://forums.ybw.com/index.php?threads/how-a-proa-works-building-a-45ft-aluminum-proa.532963/

Re how you are building in aluminium - have you done a reasonably detailed weight estimate to see how it compares with the buoyancy available?
That hull looks very skinny........

 

I am curious, did Harris designed you a 45 Harry or did you just multiplied his offsets by 1.5?
What thickness Al plate are you using?

 

Ama hull
6mm on the bottom
4mm on the top
Vaka hull
10mm on the flas bottom plate
6mm on the bottom side
4mm on the top sides

I've done a basic volume calculation with the vaka hull alone. And the waterline seems pretty close too the original plans if I use the weight of all the aluminum I bought for the project as a reference

But this then is pretending use 100% of the aluminum
That the ama is flying so that all the weight and buoyancy needs to

 

I multiplied the patterns of the hull plates and most of the parts by 1.5 times.
Just getting the right patterns shapes and changing certain ways of building due to the different material and building style

 

I bet Harris is thrilled.

IMHO getting a profesional welder to weld it up after you tacked it to shape is your only chance to get her floating.
Keep us posted and in pictures.

 

Multiplying by 1.5 does not give you correct dimensions. The volume, and therefore the hull loading, increases faster than the surface. How did you calculate the structure? I see widely spaced bulkheads and a light angle at the seam. By the way, the welds are awful.

 

There is so much there...im not sure where to start. It would simply take too long!

I would recommend reading the article about basic fabrication and sequencing "Order of Assembly" in Proboat Magazine issue 151 Oct/Nov 2014.

But good luck ...

 

Good to see someone hopping out of their arm chair and having a go.

A friend built an alloy 29 foot cat, round bilge, seat of the pants design, with almost no internal structure except for the three beam bulkheads.
He had access to an English wheel so played around with full size sheets till he had a great looking shape. 30 years of hard racing and cruising later its still going strong.

On the back of this success his mate built a 45 footer similar method and its still going strong.



So Pororoca, don't listen to the neh sayers, good luck and keep posting.

Ps, 3 tons displacement seems about right for a mini minimalist boat.

 

It will be too late then! - this boat is so narrow you must finish the welds on inside on the way up to the gunnels. The other thing I don't like is how hes brought 2 sheets together to form the bow without making a joint surface between them(how do you weld the backside of the joint being so narrow?), is it done the same down the keel line?

He should start by buying a bottle of 100% argon. He's is using co2 the black around the weld gives that away, even on steel I use would speed shield(25%argon).

Love his idea, but he is doomed by lack of technical skills and finance. Get some tech assistance before you wreck a bunch of alloy plate..........

 

It needs stringers between the bulkheads. You need an engineer. Like the concept is great idea for liveaboard coastal hopper. Put an outboard on it, it will need it to navigate in ports and rivers.

 

Hi Pororoca
Seven years ago I built my Proa Nixe in Thailand. Many questions people asked me were about how the design was calculated and if I had an engineer to help me and if the design was safe. It looked like they worried about my safety but when I told them: No there is no engineer, I calculated myself, they went away and were never seen again.Nixe is a safe boat, she prooved that.
With all good advices from other people I got I could build a hundred boats.
So just go on and don't mind these people who although they never built a boat think they know it better.
They haven't seen your boat finished.
Alex

 

Nixe Alex, the above posters who are critical of Pororoca do happen to know what they are talking about (otherwise they wouldn't be posting here).
Especially Ad Hoc.
They are concerned enough to voice their opinions.
If Pororoca listens to them, he will end up with a (much) better boat.