Traditional "Rule of Thumb" methods

[gonzo]

This thread is about describing traditional rules of thumb. If you want to criticize or otherwise argue about these methods, please don't post in this thread; start a new one. Thanks.
There are still many places in the world where shipwrights build by rules of thumb. These have evolved through a process of small changes. Experienced shipwrights build vessels that are adequate for the intended use and usually from local materials. Some techniques are odd to those not used to them. For example, frames that are not symmetrical port and starboard, or spaced equally.

 

[Angélique]

Some old Rules of Thumb from the Vikings . . .

Vikingskip og norske trebåter = Viking ships and Norse wooden boats → How to build a Viking ship & Principles of Norse boat building

There's still a constant further development of existing Rules of Thumb in shipbuilding and engineering, and even new Rules of Thumb are developed all the time, like in the below example . . . .

- European Inland Waterway Navigation Conference, 10 - 11 - 12 September 2014, Budapest, Hungary

- Submission: Delft University of Technology, Department of Ship Design, Production and Operation

A building cost estimation method for inland ships - - Note: ‘‘estimation method’’ = Rule of Thumb​

Delft University of Technology → Repository → A building cost estimation method for inland ships → PDF = also attached below

‘‘ Abstract
There is very little publicly available data about the building cost of inland ships, especially for ships that have dimensions that differ significantly from those of common ships. Also, no methods to determine the building cost of inland ships are described in literature. In this paper, a method to estimate the building cost of inland ships is presented. Furthermore, the method is used to develop rules of thumb for the cost of inland ships as a function of their length, beam and draught. All material that is presented in this paper is based on or taken from Hekkenberg [2013]. ’’

By: Robert G. Hekkenberg
- Delft University of Technology
- Faculty: Mechanical, Maritime and Materials Engineering
- Department: Marine and Transport Technology
- Mekelweg 2, 2628CD, Delft, the Netherlands

Publisher: Budapest University of Technology and Economics

Edit = added ‘‘ Note: ‘‘estimation method’’ = Rule of Thumb ’’ + attached PDF​

 

[DCockey]

The center of lateral effort, center of lateral resistance and "lead" between them for balancing sail boats can be considered as a "rule of thumb" which ultimately is based on experience.

 

[Angélique]

Some definitions:

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Wikipedia: Rule of Thumb

‘‘ A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination. It is based not on theory but on practical experience. ¹

Compare this to heuristic, a similar concept used in mathematical discourse, psychology, and computer science, particularly in algorithm design.

¹ "rule of thumb, n. and adj." OED Online. September 2016. Oxford University Press. ’’

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Merriam Webster dictionary: Rule of Thumb

‘‘ - - 1: - - a method of procedure based on experience and common sense

2: - - a general principle regarded as roughly correct but not intended to be scientifically accurate​

First Known Use: - circa 1658 - - ’’​

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[gonzo]

Some old Rules of Thumb from the Vikings . . .

Vikingskip og norske trebåter = Viking ships and Norse wooden boats → How to build a Viking ship & Principles of Norse boat building

There's still a constant development of existing the Rules of Thumb in shipbuilding and engineering, and even new Rules of Thumb are developed all the time, like in the below example . . . .

- European Inland Waterway Navigation Conference, 10 - 11 - 12 September 2014, Budapest, Hungary

- Submission: Delft University of Technology, Department of Ship Design, Production and Operation

A building cost estimation method for inland ships - - Note: ‘‘estimation method’’ = Rule of Thumb​

Delft University of Technology → Repository → A building cost estimation method for inland ships → PDF = also attached below

‘‘ Abstract
There is very little publicly available data about the building cost of inland ships, especially for ships that have dimensions that differ significantly from those of common ships. Also, no methods to determine the building cost of inland ships are described in literature. In this paper, a method to estimate the building cost of inland ships is presented. Furthermore, the method is used to develop rules of thumb for the cost of inland ships as a function of their length, beam and draught. All material that is presented in this paper is based on or taken from Hekkenberg [2013]. ’’

By: Robert G. Hekkenberg
- Delft University of Technology
- Faculty: Mechanical, Maritime and Materials Engineering
- Department: Marine and Transport Technology
- Mekelweg 2, 2628CD, Delft, the Netherlands

Publisher: Budapest University of Technology and Economics

Edit = added ‘‘ Note: ‘‘estimation method’’ = Rule of Thumb ’’ + attached PDF​

Interesting how it gives enough information to build the boat. Any shipwright would be able to follow the basic directions. Usually, each modifies it to suit his building preferences and available materials.

 

[Angélique]

Interesting how it gives enough information to build the boat. Any shipwright would be able to follow the basic directions. Usually, each modifies it to suit his building preferences and available materials.

Yes, I came across some nice examples of this, I think I'll start a new thread to post these, as I don't want to distract this thread about Rules of Thumb with a lot of Viking Ship building.

P.S. - ‘‘ I think I'll start a new thread to post these ’’ - Done → Viking Ship Building

 

[hoytedow]

You all post some cool stuff and I thank you.

 

[DCockey]

Billy Moore builds a traditional Chesapeake Bay deadrise boat without plans or loft.

 

[DCockey]

César Newashish builds a birch bark canoe without plans, molds, etc.
César's Bark Canoe https://www.nfb.ca/film/cesars_bark_canoe/

 

[gonzo]

A method I've seen in several areas around the world, is to first lay down a keel and attach a bow stem and transom. Then they place the frames at the widest beam. After, they fill in between while using some battens for fairing. Some of those shipwrights would make fun of me for lofting. They teased me about having to draw a boat before building it. I've learned a lot from both approaches.

 

[DCockey]

Several years ago I visited a boat builder in Virginia who was building a flat bottom outboard skiff for crabbing. He was working in a shed with a dirt floor and the boat was being built inverted. The stem, keel and transom were in place with the stem and transom fastened to stakes driven into the ground. The stem and keel were straight pieces of timber. The builder said the owner had requested a 2o foot boat but because the timber for the keel was longer he was building a 22 foot boat. A temporary frame representing a section near the middle of the boat was also in place with battens representing the chines and sheer. The building was experimenting with the width of the bottom and amount of flare to find a combination he liked. Then he would build a stronger mold/frame and bend the planks for the sides into place.

The builder said he could not build a boat using plans and offsets. He and a friend one time had looked through Chapelle's book "American Small Sailing Craft" and saw a Chesapeake Bay skiff they liked. So they looked at the plans, and then built a boat. He said it came out looking like the boat in the plans.

 

[Angélique]

The center of lateral effort, center of lateral resistance and "lead" between them for balancing sail boats can be considered as a "rule of thumb" which ultimately is based on experience.

Here's a "Rule of Thumb" for the "lead" on Schooners from the thread...

Centre of Lateral Resistance, Centre of Effort and lead ---> post #47​

‘‘ . . . . She is the best balanced boat I have ever sailed. I still use her lead [with a long 'e' as in 'need'] for the gold standard when drawing schooners: that is, a 10% lead (with the full rudder included in the CLR). You can control her simply by trimming the mainsheet. The rudder sometimes seems redundant. . . . . ’’

Please see for the sources and/or responses and/or discussion about the above quoted so called ‘‘gold standard’’ the above linked subject thread about "lead" where this as a ‘‘Rule of Thumb’’ for the "lead" on Schooners came from.

 

[Angélique]

→ Estimating Epoxy Amounts

 

[Angélique]

'guesstimate' the displacement​

Thread: - 36' x 16' Cat Hull for Tiny House Project - Need Help Please - ---> - Post #26