A general question about boat construction and how they are designed to handle the fo

[MicHughV]

that website is a wonderful and vivid visual display of forces at work on a sailboat !!!

[ShinyHappy]

Thank you all for commenting! I've learned quite a lot from the comments and links.

The question came up while reading some of the threads about dismasting and other mast issues. Understanding the systems helps a lot.

[MicHughV]

a good friend of mine set out to do a specific voyage....a very experienced sailor, he sailed thru' the canal and on to Easter Island, then around Cape Horn for the run home. His boat was built to take it. Everything on it was supersized.
Coming up the east coast of Argentina, in relative smooth water and a light 5 knot breeze, his mast came tumbling down, just like that, completely unexpected, the cause later attributed to one of the shrouds coming loose from it's fitting.

There is no telling what can happen offshore. Despited having the best possible boat, one also has to have a plethora of tools, spares, parts, etc, and the ability to jury rig something...anything....at any time...day or night....

[ShinyHappy]

Originally Posted by Singularity

And don't forget about the monocoque principle.

I thought this might be the whole of it. Not really seeing the structure underneath the sole and cabinetry I thought that might be the answer. Kind of like the guy laying on the bed of nails, each small piece takes a little bit of the strain making up a strong whole.

[ShinyHappy]

Originally Posted by roland stockham

The simplest way to picture this is rather than thinking of the hull overall think in terms of a wire frame. In the center of the hull at the mast is a ring (it is sometimes referred to as a ring frame)...

Thank you, this really shined the light. In searching, I couldn't find this part that ties it together.

[ShinyHappy]

Originally Posted by Stu Jackson

One other thing to add to the fine info already provided:


Chainplates. Many neophytes believe they are connected to the deck. Not true. The chainplates connect to the shrouds and run through the deck to supporting structure that connects to the bottom of the hull. On my boat they are heavy duty ss rods which go to a structural grid below.

I would be one that didn't know this about chainplates and was something I questioned. I wondered how the deck could handle it.

I've seen those supports below deck but without seeing where they attached didn't put the whole thing together in my head.

[ShinyHappy]

Originally Posted by MicHughV

Many years ago now...I built my own boat....at that time there was a book called "Skene's elements of yacht design", which led a person thru' the various load aspect on a sailboat. Ok, it's an old book, written back in the time, when everything was worked out by hand on a sheet of paper, which makes it easy to understand today.

From this book, one could calculate the compression loads on mast, tension loads on rigging, etc...I think it is downloadable in pdf format now.
That book originally came out in 1904 , I think, with various upgrades since.

To cut to the quick, I calculated the compression load on the main mast for my boat....a Roberts 38, plus rigging loads, etc, and was stunned to find out the incredible loads involved. Mast compression can easily top several thousand lbs or more...same with the rigging.....add a few safety factors for fatigue and age and the loads skyrocket even more.

The loads on the mast, rigging, turnbuckles, sheets, turning blocks,winches, etc, are enormous.
The hull has to carry all these loads...plus the bending moment of a keel weighing 1,000's of pounds and also movement thru' the water, up, down, sideways, etc.

Off course, you make anything big enough, you can make it strong enough, but the tricks is make it as light as possible, yet retaining it's strength.

It's a complicated science to get all right and working together, and really is the domain of a nautical architect.

Off course, today, we have the computer to aid in the design...and 3D modeling, plus various other engineering programs, etc.

It's not so easy, you can " wing it" and " hope for the best"....but ultimately, your life may depend on the integrity of your boat...so it's not a place to take short cuts.

Today, we also have the exotic materials, carbon fiber, kevlar, etc which are all finding their way into boat construction.

There is no quick and easy answer to your question. It will require you to spend some time to study all the different aspects of boat design. Maybe a lot of time.....

I understand the complexity. In this case I'm trying to see it from a user rather than a builder. I like to tinker, but I'm certain I don't have the patience to build a whole boat.

As a kid, I grew up at least 50 miles from an ocean so it was kind of odd to discover that someone was building a sailboat near my house. It was in a massive sling in his yard and over the years it slowly took shape. At college and after, I realized it's no longer being built but now just sitting and weathering.

I wasn't interested in sailing at the time, but even a couple decades later I wonder if that boat is still there.

[MicHughV]

Ha, as a youngster, I knew several people in the neighborhood building boats in their driveways, at least 500 miles from any ocean. Then one day, the boat would be gone.

If the bug gits ya, it gits ya.

I was around 13 years old, still in school, when someone handed me a Bruce Roberts "build your own" boat catalog. Therein, was a picture of a Roberts 38, which I cut out and kept. I kept that picture in my wallet for another 13 years, before an opportunity came to build it and build it, I did. It was the start of a lifelong journey on the water.

[MicHughV]

I thought I would attach a pic of my first boat that an artist friend of mine sketched up...