Discussion in 'Boat Design' started by JohnRichard, Aug 26, 2021.

1. Joined: Sep 2020
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### JohnRichardNew Member

After speaking with several knowledgeable people about which type of boat design was right for me, we settled on a custom modification of traditional lines. My plan is to build this ship over the next 4 -5 years, including cutting the lumber. It will be traditionally built with plank and frame construction out of oak and pine, which I have in ample supply; live oak being the goal for frame material.

I have attempted to draw up the lines, this is my first go. I will certainly need to do it again, but I wanted some guidance at this stage. The line drawing ended up being two feet taller than planned on the centerline, which is my fault in not calculating correctly. This will be fixed, but I did these drawings mostly freehand, or used whatever thing I could manage to make curves with.

Some questions came up during this process which hopefully someone will be kind enough to opinionate on:

Do I need more frames? There seem to be several options on the internet regarding calculating displacement, station spacing, et al. When I did the maths for frame spacing, the average answer I got was 16.5", which seemed like a lot.

I studied what lines I could find for Oyster smacks, and they mostly use a 3-foot spacing. That's a difference of 35 frames versus 17. Or maybe split the difference and use a 24" spacing. What are the general consensus on this? I have read that frame spacing is - put them where you need them, then go based off that at intervals that are easy to manage.

As far as the sail plan goes, I did not measure where to put the mast yet, I just drew the sail plan based off the amount of sail I wanted. The mast may need to be moved back based on the drawing. How does one calculate where the mast needs to go? The sail plan drawing is based on a mast that equals the deck length.

This is not suppose to be a race car, its a work truck. I'm designing it to be a live-aboard, long distance, ocean crossing, expedition boat, with a shallow-ish draft, brick farm house. No teak, no varnish, just wood and paint. Repairable anywhere in the world for mostly cheap, able to be sailed short-handed, no giant sails or forces.

Here are the working details, which I have been designing to:

Length on deck: 48'
LWL: 43'
Draft: 5'-8"
Displacement: 30T
Mast height: 48'
Sail Area: 1611 sq.ft.
Rig: Topsail Gaff Yawl

Any other general thoughts?

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### SkyakSenior Member

My first thought is that frame spacing is not the kind of question someone should be asking if they expect to design and build such a boat in under 5 years. Have you considered building to an existing design? I don't think there have been major improvements in the past hundred years and it is easy to draw something that can't be made.

(2049) Sampson Boat Co - YouTube

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### TANSLSenior Member

@JohnRichard, you should make a preliminary General Arrangement drawing and a Body Lines plan that will allow you to take actual measurements and perform some calculations to confirm the data you already have and to check that the shapes are fairly smooth.
After that, you can talk about the separation of frames and many other issues that must be defined.
If you need help on any subject, I would be happy to provide it. Send me a PM in that case.

4. Joined: Sep 2020
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### JohnRichardNew Member

@TANSL I don't think I am able to send private messages yet? Perhaps a forum requirement I have not met. I will read about the General Arrangement drawing and try to make one.

Thanks!

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### sharpii2Senior Member

As far as I know, frame spacing is proportionate to plank thickness.

This means that the thicker the planks are, the further apart the frames can be. This is because the frame's primary job is to hold the plank edges together.

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### TANSLSenior Member

It can be said like this although it is necessary to qualify it a bit. It is the thickness of the panel that depends on the separation between the reinforcements that make up its perimeter, transverse and longitudinal reinforcements.
When scantling a hull, the first thing to do is propose a distribution of the primary and secondary elements. The scantlings of the resulting panels and the reinforcements are then checked, and the necessary elements are corrected.

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### sharpii2Senior Member

A good thing for you to check out is "Salt and Tar" on YouTube.

It documents a photogenic young couple's quest to build a 35 ft cruising sailboat.

Like you want to, they made their hull out of plank-and-frame wood. They made everything themselves except the engine and the sails.

By day 1,620, they had competed the hull, deck and cabin top. They launched it with no ports, no companion way hatch, and no interior. The engine was on board but not installed.

This should give you some pause.

Their boat is not only less than half the displacement of your proposed boat (about 12 to 13 tons), but it is a single-chine vessel with straight sawn frames (far less carving the backs of the planks, shaping their fronts, and cutting them to fit precisely).

Not only that, but it was drawn by a professional naval architect.

With this in mind, I think you may need more like a decade to complete this project, if not more.

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### Will GilmoreSenior Member

Traditional rigs are beautiful, but the simple Bermuda rig is, just that, simple and effective and easy to handle. Sail lofts all over the world know this rig. If practical is what you are really looking for, I suggest a Bermuda or Marconi ketch instead of a yawl. The ketch will allow you to balance the sails better for single hand sailing by dividing the sail weight more evenly between the main and the mizzen.

How much sailing experience do you have?

-Will

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### CT249Senior Member

Surely there is no way to move a beamy 30 tonner without giant forces?

Your main has about 50% more area than that of a typical modern 45' racer/cruiser. Isn't that a giant sail?

How does one define "knowledgeable people"?? How do you know they have more knowledge than people who prefer completely different boats and have enormous experience?

In how many parts of the world will you find planks of the right type and size for repairs? Would that really be easier than using other materials?

If you were building a car, a travel trailer, a plane, a bicycle, a tent or any other comparable device, would you copy the design of an 1800s commercial example of the same sort of device? Is a Model T truck the ideal car for modern touring? Is a Curtis Jenny the best plane for travelling around today? Is a cotton and wooden-pole tent with a wood fire the best tent one can make these days? Is a 1920s delivery boy's bicycle with wooden rims, no gears and spoon brakes the best bike for touring in 2020?

Last edited: Aug 27, 2021
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### TANSLSenior Member

@CT249, although I could agree with everything you say, how can we express an opinion or give advice without knowing the SOR that the OP has conceived for the ship?.
All we know is: "This is not suppose to be a race car, its a work truck. I'm designing it to be a live-aboard, long distance, ocean crossing, expedition boat, with a shallow-ish draft, brick farm house". Can you, just with that information, say that the choice is not adequate?. I would not dare to say anything about it. Let the OP explain more to us, if he wants, before smashing his project.

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### CT249Senior Member

I didn't say the choice wasn't adequate. I was just interested in exploring the reasoning behind the choices.

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### TANSLSenior Member

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### gonzoSenior Member

This is like designing a Conestoga wagon to commute to work. There is a romantic appeal to it, but unless you join an Amish community, very impractical.

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### clmangesSenior Member

@JohnRichard, for your stated uses, you might consider a junk rig. There's a lot to like about them in terms of ease of use, comfort, and safety. Go on over to:

The Junk Rig Association - HOME https://junkrigassociation.org/

If you sign up there (cheap), you can download entire books from their library at no further cost. Best of those is Practical Junk Rig by Hasler and McCleod; it's a bit dated, but JR fans call it the 'bible'.

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### rangebowdrieSenior Member

Looks quite like an enlarged Spray,, cods head, mackerel tail.
Proposed time frame seems conservative.

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