modern classic 37'

[GeoffD]

Hi everyone,

My name is Geoffrey and I live in Antwerp, Belgium, quite close to what I consider one of the most beautiful harbours in Belgium: the Willemdok.

For quite a while I have been playing around with the idea of designing and eventually building my own boat. Until recently it was mostly just sketching and experimenting, but I have now reached a direction that I like enough to seriously investigate whether I could actually build it.

My main profession is carpentry, and I also have extensive experience with CAD, AutoCAD and 3D modelling. However, I have no previous experience with boatbuilding or naval architecture, so I am very aware that there is a lot I still need to learn. That is actually one of the main reasons I joined this forum.

For the styling of the boat I started from what, in my opinion, are two of the most beautiful wooden boats/yachts ever made: the Spirit Yachts and the Riva Aquarama.

I experimented quite a bit with AI-generated concept images to combine some of the characteristics I like from both. Obviously these are only concept images and not engineering drawings, but they helped me establish the proportions and overall character that I would like to pursue.

The current concept is approximately:

11,4 m x 2,8 m
wooden construction
Primarily intended as a weekender, with perhaps one or two longer trips each year
For cruising around Antwerp and nearby waterways, my initial idea was to use electric propulsion, combined with a relatively small diesel generator as a range extender. The intention would be to do most shorter trips electrically while still having enough range and independence for longer journeys.

More recently I started thinking about adding a mast as well, which has slowly pushed the concept towards something closer to a motorsailer.

I realise that adding a mast changes the project considerably. It introduces a lot of new questions and practical problems.

I am absolutely not under the illusion that an AI render or a nice CAD model makes a seaworthy boat. My intention is to gradually turn the concept into a proper design, learn the required calculations and construction methods, and involve a naval architect or experienced designer where necessary.

Please feel free to be critical. I would much rather discover a bad idea now then after hundreds hours of drawing

I will add some of my current concept renders below so you can see the direction I am aiming for.

Thanks in advance!

Geoffrey

 

[TANSL]

Hello @GeoffD and welcome to the forum. I think I could help you in the subject of naval architecture and I'd be happy to. Please feel free to contact me if you'd like.

 

[HelmutSheina]

I feel that electric is a poor option for a motor sailer because you won't be able to operate it unless the diesel is running. A 40' motor sailer would need a 40hp diesel. You just don't have independent charging options for that sort of draw unless an engine is used, and if that engine is going to be running when the boat is underway, it may as well be used to run the boat.

However, if we consider a vessel designed as a pure sail boat with good upwind performance; an electric outboard could be used as auxiliary propulsion for marina operations etc, and also to power a tender dinghy; and you would rarely need to start an engine as wind/solar would cover usage.

 

[Paul Scott]

Geoffrey, it’s a fine madness! My $.02, from the point of view of our 40, uldb electric sailboat. (During our recent refit we went fully electric)

For the first couple of years after the refit, we thought we needed a range extender, but I’m beginning to question that.

You basically have shore power, solar power, regeneration, wind and current-how fast do you want to go, how far, and what power do you need to do that?

Solar can look really ugly, although some built in stuff can look really good, but you need a lot of it to make it worthwhile.

Sailing works, and motor sailing really works (I mean really works- apparent wind is amazing stuff- even in 2 knots of breeze downwind with our code zero up, and the electric giving us with what would 2-3 knots without sails (which would give a 6-7 hour motoring time), we can get 5-6 knots.

So given that, what do you need?

The most exquisite sailing performance hull you can imagine- one that can sail in very little wind, but has enough power to use the drag of prop regeneration in moderate to strong winds.

You need a rig that is easy to change gears with, from motor sailing in a zephyr up to strong winds with speed control, as some regen systems won’t work if you’re going too fast, like more than 10-12 knots.

You need to an upwind machine that tacks through extremely fine aoa in any wind, what with apparent wind velocity headers when motor sailing as a way of life. You need an easily driven hull that loves light air, and can get quickly to and stay in regen speeds, so a 10-12 knots hull. Although a planing hull is nice, you’d need to be able to change sail gears some to keep going a regen speeds. Open 60 type rigs with lots of roller furling might be useful for inspiration? (Otherwise you’re running around a lot for sail changes, reefing, etc.

I would go with an electric outboard, so you’re not dragging a regen turbine prop when you don’t need it- folding props, as far as I know, don’t do regen. Pull up the outboard when sailing, put it in the water when you need it. I suppose you could go with an inboard prop/shaft that folds into the hull? Might look better, but kind of a pain for upkeep.

So a cutter rig van Hoek (hope I spelled that right) type of hull, although a cutter SoT / pilot boat Irens aesthetic might work.

I need to walk the Terrier, so I’ll stop here. If you have any question, post here and I’ll respond.

 

[Paul Scott]

Terrier is happy, so back to motor sailing musings.

If you want solar in the equation, it gets harder to do aesthetically, although Grand Soliel has done a monohull -33’ Blue ?- that looks good, but small solar panels- which points towards multis, which may not meet your aesthetic criteria-

UK has some vaporware on the web about sails covered with solar panels. IIRR, some solar panel paint is in the works, as well as more efficient batteries.

Something like a sleeker Gougeon 32 Russell brown riggged catamaran covered with cells and two electric?outboards?

 

[Paul Scott]

Something 2 consider, room for solar cells, rig, couple of e outboards, larger size…

 

[Paul Scott]

Torqeedo non folding propellor that can do regeneration I think

 

[bajansailor]

Just some thoughts -
Your dimensions are 11.4 m x 2.8 m and the Length / Beam ratio is 4, which is relatively skinny - your hull looks tubbier than that.

Copied below for comparison is the GA for the Spirit 37 from Sailboat Data - she is 11.3 m x 2.13 m.

If the helmsperson is of average height, are they able to see over the top of the deck saloon, or do they have to look forward through the windows of the deck saloon?
Have you also considered having two helm stations, one on each side, at the aft end of the cockpit?

That mainsheet in the location shown could be a menace to the crew when tacking and especially gybing.

On the side profile, the roofline is angled forwards quite a lot - might it look better if it was more horizontal?
Although that then restricts the headroom in way of the entrance even more. I see that there is a step down, but no sliding companionway hatch - will the crew have to duck their heads down to enter the cabin?

 

[GeoffD]

Hi,

I didnt look into regeneration yet but its something I can explore and read more about.

For the most part I will be on the Schelde towards Zeeland, since its a busy area with some of the biggest commercial vessels passing by, (container and cruise) sailing there is an absolute no go.

So the main propulsion would be electrical.
7-8 knots should work with 20KW if the current isnt to strong.
Since batteries alone wont do it for the longer trips, I need a form of hybrid like generator or sails or both.

I gave up on the idea for a planing hull since batteries would give up after 30 minutes or so.

 

[GeoffD]

Just some thoughts -
Your dimensions are 11.4 m x 2.8 m and the Length / Beam ratio is 4, which is relatively skinny - your hull looks tubbier than that.

Copied below for comparison is the GA for the Spirit 37 from Sailboat Data - she is 11.3 m x 2.13 m.

View attachment 209834


If the helmsperson is of average height, are they able to see over the top of the deck saloon, or do they have to look forward through the windows of the deck saloon?
Have you also considered having two helm stations, one on each side, at the aft end of the cockpit?

That mainsheet in the location shown could be a menace to the crew when tacking and especially gybing.

On the side profile, the roofline is angled forwards quite a lot - might it look better if it was more horizontal?
Although that then restricts the headroom in way of the entrance even more. I see that there is a step down, but no sliding companionway hatch - will the crew have to duck their heads down to enter the cabin?

thank you for the drawing. I am planning on finishing the first side and topview in CAD this week so I get an idea for length to width that would work for the deck saloon and cabine. However I find it difficult to determine the waterline and height. I fiddled a bit with Delftship but I just cannot manage to get the right hullshape that I want. If I have a weight estimation I could see how much m3 I need under water. I can get volumes out of Fusion 360 so I can model the underwatership accordingly.

The place of the helm is really conceptual at this moment. Once I have the 3D model I can place a camera in the software to determine line of sight with renderings.

A question from my side, a helm in the deck saloon alone wouldn’t work for sailing?

 

[bajansailor]

A question from my side, a helm in the deck saloon alone wouldn’t work for sailing?

No reason why the helm in the deck saloon cannot work - after all it is a motor sailer, so when sailing you will just set the sails according the wind angle on that course and forget about them, unless you have a major course change or a big wind shift.
Many motor sailers have a hatch above the helm in the wheelhouse, so the helmsperson can look up and see if the mainsail is luffing or setting nicely.

Re the image you posted above, you could also consider having the helm on one side, rather than on the centreline.
When underway under power you generally have to give way to most vessels approaching from your starboard side, so very often the helm is on the starboard side of the wheelhouse.
And if you are singlehanded, you can come alongside a dock starboard side to and lean out the window and toss a spring line on to a dock cleat (if you have a suitable cleat on deck within reach). Put the engine in slow ahead, and turn the helm to port, and you will hold her there very happily while you add the bow and stern lines at your leisure.

 

[GeoffD]

With a bit of delay I was able to start sketching. I decided to plan the toilet in the cockpit itself so that there is still full standing height to enter the toilet cabin itself.
For now I didn't take into account a helm in the deck saloon. the saloon itself had a step down. I decided to make use of a electric saildrive with the batteries installed under the cockpit floor to try to lower the center of gravity.

please, if you would find any major flaws that I didnt take into account let me know
I will use these sketches to start making a first version of the hull in 3D.

 

[gonzo]

The maximum beam is way too forward. That looks like the lines from a boat of centuries ago. Also, you need to design the Center of Buoyancy and the Center of Gravity to align vertically in both longitudinal and transverse directions. That means calculating your expected submerged volumes vs weights and locations of everything. Then repeat for several degrees of heeling and compare.

 

[bajansailor]

The maximum beam is way too forward. That looks like the lines from a boat of centuries ago.

The classic 'Cod's head and mackeral tail' design approach.
This article explains it nicely.

Navalapp

During the 18th and 19th centuries, hull design was still based mainly on intuition. Although not supported by any scientific evidence, the belief was that underbodies shaped like a fish operated...

www.facebook.com

 

[GeoffD]

Hi, thanks for the feedback. I took this into account and started off a bit smaller. I'm also considering lowering the measurements to 9 m x 2,5m which seems less overwhelming to build.
For this exercise I used the drawings of an existing boat and try to model the hull like so.

I also tried to do a rough estimation for weight calculation (good thing I got the displacement 1,6T from the boat I based myself on) which will help me find the center of gravity ...
On this estimation I could figure out the volume I needed for the desired waterline. According to the surface area on the DWL I would sink or rise 1mm per 10kg.

As per images i'm tending more to a pure sailboat.