Drawing building plans from an existing vessel

[Steve Sanford]

Good morning, All~

Dax Hinton recently asked me how difficult it would be to draw plans to build an existing gunning boat - specifically the sweet "Midwest Gunning Skiffs" (my term) he found recently in a museum (?).
The short answer, I suppose, is very difficult. It is usually the province of trained and licensed marine architects. On the other hand, I have done it - and I imagine there are others here on the site that have done it as well. So, I will give an overview of the process and some random thoughts. I would encourage anyone to make the attempt.
I would also encourage anyone to read all of John Garner's books. This one has a lengthy chapter on Four Canoes - that would be a good starting point for anyone approaching this task. A beamier version of one of the 4 - to be decked over - may work for Dax.



The example I will use is a Merrymeeting Bay Duckboat. John begins with some photos of the vessel - from various viewpoints. Note that none of the photos depict the boat in true cross section (aka section), profile (aka elevations) or from directly above (plan view).



Some terms.....

Lines Plans These are the end result of lots of careful measuring and drawing. For many small craft, all the necessary information is presented on a single sheet.....



Construction Plans - But construction details are usually depicted on a separate sheet.



Taking the Lines - This is the painstaking process of measuring an existing vessel - paying strict attention to level, plumb and square - even when most of the shapes are curves. Howard Chapelle spent many years taking the lines off small craft of all kinds back in his day. (Another book I recommend to all!)



Here's a jig I made to help me take the lines off the TED SANFORD - a Great South Bay Scooter designed and built by Benjamin Hallock about 100 years ago.



See the whole process - beginning around Gallery 13 - in my post about the TED SANFORD:
https://stevenjaysanford.com/great-south-bay-scooter/

Scantlings - These are the thickness and width of the pieces of lumber that go into a boat. Most gunning boats are built with "light scantlings" - many work boats are built to "heavy scantlings".

Sketch Plans - These are often not-to-scale conceptual drawings - either as the first step for sophisticated vessels - or as "the plans" for simpler craft. This sketch captures everything I needed to build SWEET GHERKIN.



So, if any designer - professional or dedicated amateur - wanted to draw plans based on a few oblique photographs, he or she would need to set some "hard" parameters: LOA, beam, depth, deadrise, crown - and then make lots of decisions about the actual shapes. The traditional process of hull design began with carving a half-model (Below probably not suitable for most gunning waters....), taking the lines from it, then scaling up to full-size.




With the advent of plywood, small-scale cardboard of thin balsa models can suffice for simpler craft.

S- Dax et al - I hope this overview has been helpful!

SJS

 

[D. Hinton]

Thank you Mr Sanford

 

[Ed L.]

Lofting boat hulls has come a long way baby! I had a little experience with scanning a boat hull for a company here in Illinois with a contract company before I retired. Here is a link that shows the procedure with a good description of how a boat builder goes about creating 3d models to create a mold from the scan. It's pretty interesting. I have some 3d models and cad drawings on a backup drive somewhere. I'll have to dig them out if I can find the files.

 

[Steve Sanford]

Lofting boat hulls has come a long way baby! I had a little experience with scanning a boat hull for a company here in Illinois with a contract company before I retired. Here is a link that shows the procedure with a good description of how a boat builder goes about creating 3d models to create a mold from the scan. It's pretty interesting. I have some 3d models and cad drawings on a backup drive somewhere. I'll have to dig them out if I can find the files.

Good morning, Ed~

Well...just pop the files into a 3D printer and then I'm all set to go hunt virtual Mallards!

Very cool stuff - thanks! I have been thinking of finding someone to scan one of my sleeping duck "hood ornaments" (bow handles) - for eventually casting some from bronze. A real back burner project - but I figure the first step is the scanned file...

All the best,

SJS

 

[Ed L.]

Good morning, Ed~

Well...just pop the files into a 3D printer and then I'm all set to go hunt virtual Mallards!

Very cool stuff - thanks! I have been thinking of finding someone to scan one of my sleeping duck "hood ornaments" (bow handles) - for eventually casting some from bronze. A real back burner project - but I figure the first step is the scanned file...

All the best,

SJS

That would be cool! I always liked that handle design you have. My son has a 3d printer....

 

[Scott Gilliland]

Been away for a while and just catching up on various threads. I have a little book put out by the New Brunswick Museum called "Catch a Line". It's been years since I read it, but it does provide a field method for copying lines off boats. Book is ~40 pages. I could scan it if someone is interested, but I'm not sure about copyright. Here's the cover.

 

[Steve Sanford]

Good morning, Scott~

I just found - and ordered - a copy of Catch a Line on eBay. I'm not sure how many more vessels I will measure up - but I am always interested to learn how others approach the many different "chores" that are part of boat building.

My first attempt at "taking off lines" was on my Dad's 22-foot gaff sloop - almost 50 years ago. I did it on a lawn - with stakes and strings for reference elevations. I needed an approximation of the underwater hull shape so I could design a new centerboard. The approach was evidently "good enough" because we sailed her happily for many years.

As an aside, I have often wondered how Howard Chapelle did his work - taking lines off scores (hundreds) of small craft in many different boatyards. Were I him, I would have towed a small flatbed trailer with marked centerline and stations and the works....

More recently, I took the lines off this Ralph Cranford Grassboat - built about 100 years ago. Some may know Ralph's name from Joel Barber's WILD-FOWL DECOYS - which shows a gorgeous natural cork Black Duck. Cranford was an architect who lived in Babylon (on Long Island's south shore) and included many fine details in this common type of gunning boat - common through most of the 20th century on Great South Bay.

I had a level floor (Village of Babylon Historical Society) as a reference - and very few curves - so measuring was simpler than most boats. I have a foll of marked-up sketches and will someday turn them into drawings/plans.



All the best,

SJS

 

[Tom Whitehurst]

Steve that looks like a nice South Bay Puntie. I do hope you document and develop some drawings of her. Tom

 

[Steve Sanford]

Steve that looks like a nice South Bay Puntie. I do hope you document and develop some drawings of her. Tom

Good morning, Tom~

It's quite the gunning boat. I hope to show it at the March 2026 LIDCA Show - as the Vintage Vessel.

When I measured her up - crawling around on the carpet for an hour or so, I discovered that her bottom was double-planked. This was evidently done both for water-tightness and to add a bit of camber. Never seen either in a puntie!

Wish me luck (finding the time) !

SJS

 

[Tom Whitehurst]

Good morning, Tom~

It's quite the gunning boat. I hope to show it at the March 2026 LIDCA Show - as the Vintage Vessel.

When I measured her up - crawling around on the carpet for an hour or so, I discovered that her bottom was double-planked. This was evidently done both for water-tightness and to add a bit of camber. Never seen either in a puntie!

Wish me luck (finding the time) !

SJS

Interesting, is there a layer of painted muslin or canvas between the bottom planks?

 

[Steve Sanford]

Interesting, is there a layer of painted muslin or canvas between the bottom planks?

Tom~

This old brain does not recall. But I certainly imagine a light canvas + white lead in the sandwich.

Here is the camber at the stern. I imagine it's a big help when the water gets really skinny. No runners or skeg.



The inner planking runs athwartships - and the outer planking runs lengthwise. I do not know who built this vessel - but they knew what they were doing!



A comfortable backrest. You can just make out the cross-planking. And, the deck is canvas-covered and most of the thatch is held there by a network of bronze wires. There are more conventional thatch rails elsewhere on the boat - coamings, stool rack - even the folding oarlock stanchions.



A closer look at the inner hull. Looks like clear Atlantic White Cedar - or maybe Cypress - to my eye.



All the best,

SJS

 

[Scott Gilliland]

Good morning, Scott~

I just found - and ordered - a copy of Catch a Line on eBay. I'm not sure how many more vessels I will measure up - but I am always interested to learn how others approach the many different "chores" that are part of boat building.

My first attempt at "taking off lines" was on my Dad's 22-foot gaff sloop - almost 50 years ago. I did it on a lawn - with stakes and strings for reference elevations. I needed an approximation of the underwater hull shape so I could design a new centerboard. The approach was evidently "good enough" because we sailed her happily for many years.

As an aside, I have often wondered how Howard Chapelle did his work - taking lines off scores (hundreds) of small craft in many different boatyards. Were I him, I would have towed a small flatbed trailer with marked centerline and stations and the works....

More recently, I took the lines off this Ralph Cranford Grassboat - built about 100 years ago. Some may know Ralph's name from Joel Barber's WILD-FOWL DECOYS - which shows a gorgeous natural cork Black Duck. Cranford was an architect who lived in Babylon (on Long Island's south shore) and included many fine details in this common type of gunning boat - common through most of the 20th century on Great South Bay.

I had a level floor (Village of Babylon Historical Society) as a reference - and very few curves - so measuring was simpler than most boats. I have a foll of marked-up sketches and will someday turn them into drawings/plans.

View attachment 68451

All the best,

SJS

Hi Steve,

Been offline for a while now.. putting up a small timber frame for my pizza oven and it's taken a little longer than I anticipated. Been a fun project. I've scanned and shared the book with Eric. I think he will post it to the resources section. I scanned it with my phone, maybe you will have a better device for scanning. I dug it out a couple of years ago. Here on the Lac St. Pierre there are a lot of marshes that have to be polled to get into the good spots. A friend has a little boat that he loves for pooling in the marsh and I was going to try and capture the lines format.

Hope you find it useful.
Scott

 

[Carl]

“Just a little timber frame for the pizza oven”.
Understatement I believe!

 

[Steve Sanford]

Hi Steve,

Been offline for a while now.. putting up a small timber frame for my pizza oven and it's taken a little longer than I anticipated. Been a fun project. I've scanned and shared the book with Eric. I think he will post it to the resources section. I scanned it with my phone, maybe you will have a better device for scanning. I dug it out a couple of years ago. Here on the Lac St. Pierre there are a lot of marshes that have to be polled to get into the good spots. A friend has a little boat that he loves for pooling in the marsh and I was going to try and capture the lines format.

Hope you find it useful.
Scott

Good morning, Scott~

Gorgeous! I can practically smell that pizza from here!

As a good friend once observed: "There is nothing like building!"

Our house and 2 of our barns are post-and-beam. I hope (someday!) to build a little cabin out back in the log house style. The house v. cabin distinction is that each log in the house is squared all 4 sides before all the intricate notching et cetera. My "foundation" will (would?) be Black Locust and the logs Red Pine - both cut here on the farm and sawn by my neighbors. Lots of projects on The List, though, before I get to it.....

All the best,

SJS

 

[Scott Gilliland]

I did not make the frame. A retired framer made and it sat in his building for 12 years ... the new owner need the space and sold it. I'm more of the Lego builder . The posts. beams and rafters are white pine, all the braces are black walnut and the King posts and tie beams are all cherry. It is all pegged with white oak. I just finished the roof decking that is 1 1/4" spruce t&g. I'm very happy with it.