Making 20 feet Aluminium boat and free planas

Hi, I'm planing to make this boat from aluminum.
http://svensons.com/boat/?p=MechanixIllustrated/BudgetHouseBoat
All ideas and suggestion are more than welcome. I don't have experience with aluminum and with boat building (except one 10 feet polyester on ply fishing boat).
I need suggestion on thickness of Al sheets 2mm or 3mm, to weld or to rived, how thick Al profiles I need for battens. Can I use combination of wood and Al battens. How to make joins to be waterproof, what do I need to take in to consideration during the process of building and similar stuff. I'll work at metal workshop. I'll be glade to give the favor back by posting pictures from the process and explain how some difficulties are solved.
I'm planing to start the project one mount from now since I need time to collect information and to finish other project which I already started.
I truly hope that some of you will help me to make this dream come true

 

You can't build that boat out of aluminum without a whole new set of plans being drawn up for the different material. Aluminum's structural needs are very different then plywood, so you just can't switch materials and hope for the best with any reasonably expectation of success.

 

Thank you for reply,
Ok, I understand the problem, can you help me how to make the changes in the plan, or give me some reference from where I can learn how to do it by myself.
Or if I made this boat from plywood and encapsulate it with epoxy resin and fiberglass how long it will last at fresh water, by your opinion?

 

You need more that references. Start with basic books on boat design. Then compare other similar designs for the same materials you plan on using and see if they are similar. If you are way off with your design, it is probably wrong. All this will take you several years to become proficient on.

 

Aluminum welding isn't something you can just learn overnight either, Yane. Nobody is saying that you can't do it, just that it'll take time to gather the skills & you'll need plans designed for an aluminum boat.

 

There are two basic issues here, the first is the premise that you can design an aluminum structure, that will withstand the rigors of use and the hydrodynamic implementation in the overall design, so it'll preform within the preformance envelop you desire.

Welding can be learned as Cthippo is fond of mentioning. It's not an easy skill, but can be acquired with practice and instruction.

As far as learning about aluminum structural design, well you can pick up much of this with basic engineering courses or possably reference texts, though a good head for math is necessary as with all engineering disciplines. The hydrodynamic elements of the project can be had again through courses and references, though you could solve both issues with a WestLawn course.

In the end, most decide they don't want to become a yacht designer or structural engineer, instead just buying a set of plans, which quickly solves the problem.

Lastly, a fully encapsulated plywood boat can last for generations. I have a boat I built two decades ago. It's never had a drop of paint on it (bright finish) and very little epoxy was used too. It's a molded hull and just as solid now as it was when built. What I'm trying to say is durability and longevity are more about care and upkeep then material choices in construction. The boat I just mentioned, has been kept under roof when not in use and has received timely upkeep, before issues arise.

 

I was thinking to use the basic plan and to modify it according to some general rule (rule of thumb). For example, there is need for more battens than making it from plywood, or there is need for curved surfs to compensate thermal movements of aluminum, more ribs and similar modification on the basic plan. Or may be to use DELFtship or similar software to re-design the boat according to material from which it will be build. And for the welding I'll let professional welder to do it for me.
When you speak about encapsuling plywood is there possibility for making real good quality encapsulation by using polyester and polyester gel coat, since obtaining bigger quantity of epoxy can be complicate.
p.s. Thank you all for your replays

 

Take a look on this post, what do you think about this approach

http://www.boatdesign.net/forums/me...rt-wood-plans-aluminum-construction-4186.html

 

What isn't mentioned in that post, though is hinted at, are the differences in the physical properties between aluminum and plywood. A classic example is take a sheet of 1/8" aluminum plate, say 48"x96" and clamp it's 48" edge to a table. Do the same for a 1/8" sheet of plywood. The plywood will be self supporting, though will have adopted a considerable bend, while the aluminum sheet will have bent to the floor, unable to support it's own weight. As a rule, aluminum will need considerably more internal stiffening compared to a plywood hull, especially if the plywood hull is of taped seam construction. Knowing why and where to place these supports is the engineering part of the equation. Shaping them into a boat that will do as you ask of it, is the yacht design side of the problem. Yes, you can make a plywood to aluminum conversion, but just sizing the wooden pieces into aluminum will not work, if for no other reason (there are others) then the differences in modulus of elasticity of the two materials.

 

Let say, if i make bottom grill with dimension 1'x1' and expend those ends which are perpendicular to central line of the boat to make them ribs. Then connect the ribs in between on three places (bottom, top and middle).
I can use 1"x2" aluminum profiles for grill and for ribs.
am I on good tracks?

 

You haven't the foggiest idea what you're doing. Without engineering the structure for the anticipated loads you'll encounter, you're just guessing. If you want to guess at it, then have fun with your project, but stay close to shore on launch day, so you'll be able to swim back.

 

You are not even close to the tracks. Why do you want to build a plywood design in aluminum? There are plenty of plans for aluminum boats. I am not trying to be offensive, but by the questions you ask, your knowledge is not enough to understand the answers. In your other posts about your attempt at building a plywood boat, it seems like you had serious problems with it. The metal boat will be more difficult.

 

Hi,
I find this interesting post about my problem

http://www.metalboatbuilding.org/phpBB3/viewtopic.php?f=64&t=250&start=10

 

Again, your problems are two fold. First you haven't any idea about the engineering requirements necessary to expect a successful outcome and second; you haven't the knowledge necessary to develop sheet materials into a boat shape that will not drown you.

These things has nothing to do with welding skills.