what size guage steel for this type of hull?

[Steve32]

So here is a boat we bought last year a great mod v hull now my question is the hull of this boat is made from 5052 .100" aluminum now if i was to get ideas from this boat but build it out of 44w(mild steel) how much thinner could i go? here are the specs of the aluminum boat..

Length 18' 4''
Bottom Width 60"
Max. Recommended HP 60 HP
Beam 84"
Max. Person Capacity 8 Persons
Hull Material 0.100 5052 Marine Alloy
Transom Height 20"
Max. Weight Capacity 1600 Lbs.
Max. Person Weight 1040 Lbs.
Hull Weight (approx.) 595 Lbs.

[Steve32]

here is a layout of the boat

[Wynand N]

honestly, I would go the fiberglass way with this boat. But that is only my 2c worth...

[aranda1984]

This boat is built like a brick shipyard!

Depending on the type of usage you expect from a size of boat like this, you could build it out of (maybe even less then ?!?) 1/16" aluminum.

Look at helicopters and airplanes, their clever use of stiffener angle braces or ribs.

Look at some 150 feet long (or longer) aluminum hulls.

They use ribs welded into place with roughly just twice the hull thickness (or a bit more) of your boat!

It is the way you design the structure that will basically determine the cladding thickness.

There are many computer aided softwares out there.

Once you finish the design, the software will do a finite element analysis on it and it will give you the stresses at any point on the boat.

I would never make a boat this small out of mild steel. (Too heavy!)

You could scratch the living daylight out of this aluminum boat and it will do fine!
However, make a microscopic scratch on the steel hull and it will start rusting under the paint!...

[Steve32]

What are some of the better marine design programs out there? I am in no way a engineer just a aluminum and steel welder/fitter for the last 10 years but i like messing around with cad software. Right now I just downloaded maxsurf but I haven't had a chance to try it out.

Also, where can i get some info on the design aspect of smaller modern fishing boats say 20' and under thanks in advance.

[aranda1984]

Hi Steve32.

Like you, I am not a boat designer either.

However, I have been designing and building automated machinery all my life and since 1984, I have my own company doing the same.

The last 3 years I have been bitten by this bug called "design your own boat".

I have searched high and low, but there is no way to shortcut and bypass the years it takes to become a Naval Architect.

As with every trade and profession, there are many secrets that you may or may not be able to learn from books.

I guess, you have to make your own mistakes.

I had lots of "great ideas", (like everyone else who never designed a boat) before I started my research into boat building.

A few of those turned out to be wrong, but I can see now why...

Designing a small craft under 20 feet is much simpler then building a 100 or 150' luxury yacht.

Beside, almost everything will do if you work on a small scale, except it might not be very seaworthy or might not be in trim or liike a friend's boat, it might want to go in circles...

Look at what others done before you, see if they fit your needs.

Alter some of these features to suit your custom needs. Read a few books on boat design and boat building...
The more time you spend on the preliminary stuff, the less mistakes you'll make.

... See if you can hang out with people who have built some boats...

The only advice I can give, (if I may) .. you do like building things... fine.
Buy a proven and succesful plan from some outfit and build it in your backyard.

Don't put too much hope into computer aided design softwares.
Firstly, they take quite a while to master and they will only do what you tell them to do.

To proove a point, in 1966 with my engineer (mentor) friend we built a plywood tub, it was about the size of your boat.

Vertical sides, flat bottom, 30 degree slope on the bow, but we had 4 small hydrofoils under the tub.

It was making nothing but waves 'til it lifted out of the water.
Once "airborn" it was flying... The only problem was stopping. As soon as the bow hit the water, it was a ton of bricks again!
Lesson learned, we should have made it a twin "V" hull cat. The slow down would have been more gradual.
We also built a propeller driven ice sled.. but that is another story...

Stephen I. M.

[Steve32]

this is true.... my theory for me is to start with a somewhat stock hull and change up the things I don't like about it and have my self a great handling boat.

My uncle who has built luxary yachts for 30+ years for Kanter yachts told me he would help me with the design phase but told me to find a hull style i like, make some basic drawings and come back and see him.

I'll tell you, this boat will not be in any big sea or the great lakes but in and inland lake that get a steady 4' - 6' chop. So I want something that has good speed better fuel efficentcy and a hull that can withstand a pounding. So I was interested in a mod v hull with say a 7 degree deadrise (sure a deep v would be a smoother ride but not when your running 80+ miles a day gets hard on the gas bill.

I am reading Aluminum boatbuilding by stephen pollard from spectrum boats!

[kmorin]

Steve32
I read the first edition of Boat Building in Aluminum, and many years later bought the updated edition. My impression is both books might be better subtitled "A General Overview of the Concepts of Building Boats of Welded Aluminum".

The subtitle "A Complete Guide for the Amateur and Small Shop" relies on the word "Guide" meaning someone who knows telling you where to go. But that doesn't mean the Guide is teaching you what they know, just telling you - then we do this step, but not HOW to do that step.

The book is not a tutorial in building, just an general idea of the basic sequences not down to real live, hands on shop methods. In addition these methods are those used in one shop and vaguely followed by some other builders. I think this book gives the non-builder, armchair boat fan a good look at ideas that are used; but it's not a How-To book for future builders as might be implied from the cover notes and bullet points.

If this book were placed in a full welded metal boat building course it would be limited to the introductory class only. In fact, it would be a good use of the book to create a full study each chapter/section/topic using "B/w Aluminum" as a syllabus for your studies.

Cheers,