My custom design 62FT DS homeboat

Hello, boat design community!

This is my first post on this forum, and I anticipate many more to follow.

I am starting this thread to document my work over the last couple of months and will continue to do so in the years to come.

Since it is my first post, I think it makes sense to introduce myself:
I am Vinicius, raised in Brazil, and after living in a few European countries, I currently reside in the Netherlands.

I decided to fully embrace the boat life, with ambitious plans and a sizable vessel. The boat? Let's talk about it, right? Ultimately, this is a boating forum.

My boat is being designed with the following criteria:

• First of all, it will be my future home where I will spend most of my time, so it has to be very comfortable.
• A monohull because they are safer, in my opinion, and I can't afford to build a cat.
• A deck saloon because I don't like to live in a hole; I want plenty of saloon space.
• Electric propulsion: A big saloon also provides a vast area for solar panels.
• Sailboat: I would like to take an affordable ocean cruise at some point, so as not to be limited by the electric propulsion.
• Plenty of space for guests: 2 Double beds, two single beds total.
• Budget for materials and parts < $200k.
• Woodcore fibreglass: It is easier to build than Alu; Alu would also be too expensive.

Given those requirements, I started to select a boat that would be closer to what I want.

I found the Moody DS62 with a different room planning to be the perfect fit for my needs.

Using Gene-Hull, Thanks to Jean-François for this excellent tool, I started to reverse-engineer their hull design.


Those are not the final numbers, I still have to fine-tune the bow shape:



With the offset results from Gene-Hull, I wrote a plugin for Autodesk Inventor, my CAD of choice, that imports the offsets and creates the necessary splines for the lofting operation:


That provided me the foundation to design the hull, stringers and frame structure I desire:



One may notice I only have a stringer on the keel line. This is a design choice that facilitates construction.
Following Dave Gerr's Boat Strength book calculations for this size of vessel, I would need ~51mm planks for a wooden boat. I will make my hull thickness 60mm instead, with 8mm of fibre on each side, producing a way stronger hull. If you guys like, I can dive deeper into the calculations later, but the idea is for the hull to act as an exoskeleton.
The hull's extra thickness also provides me with additional thermal insulation. I will be spending most of my time in warm weather, and I don't intend to visit the poles. So, we only need to keep the insulation for the ACs during the summer.

A 3D printed model version of the hull:


This is a 4,8% scale of the final hull, even with plastic, which is quite soft, the hull is incredibly rigid with those construction parameters.

For now, I'll keep you posted on the progress later. Feel free to shoot me questions!

 

Welcome to the forum, and I hope you find many valuable answers and advice here.
What surprised me most of all you've told us so far is the fact that you've planned 51 mm thick planks, in addition to additional fiber layers. Frankly, I think—although this is just an impression since I haven't done any calculations—that 51 mm thickness is outrageous. Just thinking about how to bend those planks makes my heart swell. I know that what is proposed is feasible, of course, but I sincerely believe you would save a lot of weight and many hours of work if you had calculated the scantlings more precisely. I think there's much to discuss and improve on this issue, although it's not the only one. The construction system could also be optimized. Have you considered strip planking or something similar?
I'm at your disposal if you need anything. I also work with AutoCAD.

 

As TANSL said, your scantlings need a full rework. 60mm thickness would be slightly excessive even for a carvel planked fishing boat of this lenght. Add the fiberglass and it becomes a waste of money and weight. 59kg/sqm for the skin is ridiculous for a pleasure yacht.
Boats this size are never buildt as pure monocoques. You don't want stringers and frames, it's fine, that's what buklheads and furniture is for, to stiffen the skin.

"Facilitating construction" by having only "one stringer" is another red herring. How many stringers and frames a boat has doesn't relate at all with how easy or fast the construction is. Longitudinally framed boats (what's called stringer frame construction in the wooden boat scene) can be one of the fastest and easiest methods to build a boat this size.
Anyway, the real boatbuilding time is in the finish and the interior. The hull is the easy part, regardless of method.

There are other things worthy of discussion, for example the electric propulsion and budget, but that can wait. First thing is to revisit the scantlings and do weight calculations.

 

First of all congratulations on such a thorough piece of design.I completely agree with the points raised by TANSL and Rumars.We often hear of the "design spiral" that leads to the correct design for an intended use and I would suggest that this is a very useful step along the way.I would add to the points raised by posing the questions that follow:who might be building the boat and where?How long has been allowed for the process?Do you have a large family to accommodate?Since there is provision for a keel and twin rudders,how much of the budget would you estimate for the sailing rig?Why would you omit a bilge stringer on either side as sailing usually involves heeling?

 

Thanks TANSL, Rumars and wet feet for the design feedback. I plan to explore the Mediterranean extensively, and with the amount of crazy people there, I thought of building my boat more like a tank, so if someone hits me, they are the first to sink!

Just to clarify I had the intention for the laminate to be 8mm GF + 44mm Wood (Considering Yellow Pine) + 8mm GF.

Strip Plank construction is what I'm aiming for here.

I came up with the initial 51mm based on the formula for Plank Thickness from The elements from boat strength:

Thickness (mm) = 18.79 x Sn ^ 0.4
Being Sn = LOA (m) x Beam (m) x Hull Depth (m) / 28.32.

Given:
LOA = 19.30m
Beam = 5.26m
Height = 3.5454
With that:

Sn = 12.70
Plank Thickness = 51.93
I took the 60mm from my butt, adding the 20% extra thickness felt like a good additional safety margin. Of course, this calculation is for wooden boats, and GF is immensely stronger in compression and tension than wood.
The reasoning was also that I plan to use softer, easier-to-work, and less expensive woods for planking, such as Abachi or Yellow Pine.

The current spine structure, combined with stringers on the edges, is designed to increase torsional stiffness.

The spine also has the objective of holding ballasts, batteries and tanks.

Speaking of that, I think it's important to mention that I will be working with daggerboards here and no ballasted keel. And since we are there, I also plan to have drum rudders ( but this is a discussion for later).

Speaking about the budget, as mentioned. I am planning to build this boat in stages. The reasoning behind this is that I don't have the money to complete this project as I want right now, and I want to have a liveable boat as soon as possible.
The first stage is to build the entire hull, bulkheads and roof. For that, I am budgeting EUR 100 K.
The idea is to have all the rooms, no furniture, fully painted white at this stage.

About 10m3 of wood = ~ 14K.
Amount of resin = ~ 15- 20k.
Amount of GF = ~ 10k.
Foam cores = ~ 5k.
Paints = ~ 15k ?
The rest for tooling, gigs and anything else that will show up as an expense.
Hatches and, if any money is remaining, some windows.
Those are rough numbers.
I am working towards having this money in about one year. I will build the boat myself and rent a piece of land to assemble a tent in Spain.

I estimate this phase will take about 1,5-2 years. I will be making the money for the subsequent phases during this period.

The next phase will be building the bare minimum systems and furniture to be a liveable floating home.

• Electrical power train + batteries + solar panels.
• Finish the galley.
• Finish one of the bedrooms.
• Fully functional heads.

Sails, guest rooms, fancy verniers and furniture will come later; it's too early to discuss this yet.

I appreciate your constructive feedback!
Vinicius

 

I don't want to offend anyone, but I would honestly forget about Dave Gerr and try to calculate the scantlings according to one of the regulations currently in force for such calculations, not those from 40 years ago (no matter how "updated" they claim to be).
I just calculated the scantlings for a 15.5 m long sailing catamaran made of plywood (plus two layers of fiberglass inside and two outside), and the maximum thickness, for the keel alone, is 18 mm. The rest of the bottom is 15 mm and the sides are 12 mm. The crossbeams (3) reach 48 mm. Because the client cannot obtain plywood of a different thickness, I had to increase the thickness of some panels.
I've spent my entire life in the Mediterranean, where there aren't as many collisions as you might fear, and I haven't seen 50mm wooden hulls on fishing vessels off these coasts for over 50 years. Nor have I seen such thicknesses on current fishing vessels in the Basque Country, which operate in much more extreme conditions.

 

Could you reach out to me in the inbox?
Cheers,
Vinicius

 

This is my current floor plan.

The room layout will likely remain unchanged, but the room sizes may change once I have furniture and accessories in place.



Doors are omitted.
The orange lines represent watertight bulkheads. 7 Wettable zones.
Tender Garage, Mechanical Rooms and Machine rooms have a lower ceiling level.
The other rooms have 2M of head clearance.

On the saloon level, I will have the galley, office and living spaces.
It will be divided into three deck levels, with the stern being the lower level, the mid-level mid-ship, and the high level at the bow.

Cheers,
Vinicius

 

Vincius ~ Gerr’s calculations are a way to learn and understand boat strength, but they would not be used to finalize a design.

I am not a designer or architect, but have read the Gerr text cover to cover. One thing to note is trading hull thickness for stringers is part of the Gerr text, iirc. And your boat only has a single keel stringer and no other longitudinals. As a boat builder, I can’t fathom this is a good idea in tradeoff with skin thickness.

I’d say you need to search for a competent naval architect.

Your budget is at least only 50% of reality or perhaps 25%.

 

Vinicius, the Van de Stadt design you posted isn't overbuildt, it has a 34mm cedar core with 1500gr/sqm fiberglass outside and 1000gr/sqm inside. 1000gr/sqm layup with unidirectional fabrics comes out at ~0.9mm thickness. The designer played the core thickness vs. skin thickness to get what he decided to be the optimal balance.
You can find similar examples, RAN Sailing (wich I recommend you watch to see the realities of building alone) at 50ft uses a 28mm core and a more glass.

With your planned 16mm of fiberglass you can just as well contemplate monolithic fiberglass construction, just add a few frames and stringers. That would have two benefits, it would take care of your collision fears and it would enable the switch to polyester resin making the build cheaper.

What's the target displacement of your boat? I'm curious because boats with inside ballast are heavy anyway and I want to know how you married that with sail area and electric propulsion.
The more I look at your proposal the more I am thinking catamaran, and I really can't see this boat beeing cheaper then a cat with equivalent living space.

 

I agree with Rumars regarding monolithic glass,but without a mould the fairing and finishing would be a mammoth project in itself.The subject that hasn't been discussed is the amount of practical experience the OP has.It is no small matter to complete any facet of a 19 metre boat and even if some elements are given to specialists,for example the electrical installation,there would still be many thousands of hours of work.There is also a need for quite a lot of equipment for lifting,access,cutting of materials and even supporting the part complete hull and superstructure.It certainly can be done but does require the sacrifice of many years of one's life and the reality that the completed boat will have only a modest value should one wish to sell it in the future.

 

Noone understands time budgets. I budgeted a minimum of two years for my build and had way over 14000 hours.

 

Vinicius,

Did you consider steel construction?
In this size range it would be worth it.

 

I would love to, since carbon steel is very cheap, but I think the risk of corrosion is too high, in my opinion.
There is also the issue of needing heavy and expensive machinery to form shapes.

Strip planking composite with vinyl ester GF is what I estimate to be a good balance between labour and investment in machinery.

Resin infusion, although requiring meticulous planning for execution, is a highly effective method for glassing the wood core.

 

You are true there,
In my case, I am dropping any side projects not related to the build. I can work part-time, and I am single with no kids.

I also have the ability in engineering and construction. I grew up in the construction business.
I have already worked on designing electrical and electronic systems.
I have already worked designing and assembling HVAC systems.
I already had a hardware manufacturing business.

So I think it varies for each individual according to their circumstances.