Designing a sailing dinghy for expeditions

Almost any boat can be made better by lengthening it.
If you are, for instance, considering 10'-12' go with 13'.
OK, I exaggerate a little but not much.

 

Project Update 2: User segment

I made a small survey which I published on a Norwegian boat forum and a facebook group for long distance sailing. I made the survey to get a general idea of what the users wanted and to get a starting point to work from. 20 people participated in the survey. There was a consensus among the participants that the dinghy should have a crew of two, that stability was important and that it should be able to beach the boat. Most of the participants believed that it was more important that the dinghy is fun to sail than it being fast. Several participants commented that the ability to trim the sails and be able to sail in both strong and light winds would make it fun to sail. There were mixed opinions regarding if it should be possible to transport the dinghy on the roof of a car. Many people believed it would be easier to use a trailer. There were also mixed opinions regarding if the boat should have oars, motor or both.

I realized that it was not a homogenous user group that was interested in a sailing dinghy for cruising and exploring. I needed to narrow down the user segment. I sorted the users into tree different groups:

1. Expedition users
These users are interested in a rational, functional boat that can handle rough seas.

2. Family users
The family users want an all-round dinghy that is easy to sail and has a small outboard engine.

3. The nostalgic users
For these users, the aesthetics of the dinghy is the most important. They are interested in the culture that is connected to sailing and they are motivated by their emotions when they are choosing a boat.

After identifying these groups, I looked into what is already on the market to see if there is a gap somewhere. For the family users I found that the sailing version of the Walker Bay dinghy is meeting their needs well. For the nostalgic user, the classical wooden dinghies are fitting. But for the expedition users, I struggled with finding a dinghy that would cover their needs. I talked with two guys who have gone on longer expeditions with dinghies and they had used dinghies designed for regatta sailing (RS Aero and Topaz Xenon). I see this as a gap in the market, and therefore I wanted to develop a concept that can satisfy the needs of the expedition users.

So, who are these expedition users?
Their main motivations are to challenge themselves both physically and mentally, to get a sense of achievement and to experience nature. Comfort is not so important, it is more important to be close to nature. The people who want to go on extreme expeditions are part of a very small group, and there is a limited commercial potential here. I would like to reach a broader user group and would therefore like the dinghy to be fitting also for the people who wants to go on smaller expeditions. Still, these users have the same motivation as mentioned above. The dinghy should be able to be used for longer trips lasting for several weeks (for the extreme expeditions) and for shorter weekend or daytrips. Many of the users are interested in experiencing all the seasons at sea, so it should also be possible to use the dinghy even in winter. As the users are interested in challenging themselves physically, there is little need for a motor, but oars or a paddle would be nice in case the wind stops.

User story: Topaz Xenon from Stavenger to Lygra

Igor Stropnik sailed a Topaz Xenon from Stavanger to Lygra (Norway) in December 2018. Under is a series of screenshots from Stropnik’s YouTube video, ”Sailing Winter Norway”, that illustrates his journey.

 

I've just looked up the older and simpler original Jimmy Skiff, she has a bare hull weight of 96 lbs (44 kg), and a max payload of 450 lbs (204 kg), no internal floatation tanks, and no outboard option. So I'll guess it must be possible to stay within 60 kg hull weight with built in floatation.

 

I'm glad to see Terry's website is still online to harvest some ideas... (see the thread: Ancient Kayaker RIP)

The Ancient Kayaker → Sailboat

‘‘ - Mobility on Land

-

The finished hull is only 60 lb (27 kg) without the sailing rig, but it's not an easy thing to move around because it is too big to carry under one's arm!

I found a cheap replacement wheel for a snowblower, and a pair of incredibly cheap oars which I got from a department store. The wheel is attached to a simple frame that fits inside the daggerboard slot, and the oars make a neat set of handles, converting the boat into a wheelbarrow! ’’

 

Thank you, Angélique, for all your helpful tips. I think it is really interesting what Terry says about the boat being challenging to handle even with its light weight, but seems like he found a good solution. This is something I have to take into consideration.

 

To explore the order of magnitudes and the issues to consider, I did for you a preliminary approach of a dinghy 12' hull using Gene-Hull application, and inspired by the RS Aero but with :

• more payload capacity (up to 200kg, proposed drawings are done with the waterline for 150 kg payload)
• more free boards for seaworthy (42 cm at bow, 34 cm at midship),
• good initial stability through a bit more beam (1,50m, and 1,07 m at waterline) and a bit less length (3,7 m) to compensate for the weight
• a bit more more beam also allows more righting moment without too physical extension of the body, so more confortable ergonomy in the context of a 8 hours sailing, at the cost of a small loss of speed likely.

A preliminary mass breakdown gives 77 kg light weight, including 200 liters of floatation foams, I think it is possible to be lighter although 60 kg is challenging.

The payload is the main difference (RS Aero is given for 35 to 95 kg sailor), which can influence the speed potential, especially the access to usual planning speeds for a dinghy : from payload 100 to 200 kg, the Displacement Length Ratio DLR jumps from 126 to 197. With DLR > 150, you can be limited to the so-called hull speed, here about 4,5 knots.

About EU rules , 4 design categories are considered : A, B, C or D

Design Category C ~ 'INSHORE' : Designed for sailing in coastal waters, large bays, estuaries, lakes and rivers where conditions up to and wind force 6 and significant wave heights up to, and including 2m may be experienced.
>>> I suppose you aim this one.

Design Category D ~ 'SHELTERED WATERS' : Designed for sailing on small lakes, rivers and canals where conditions up to, and including wind force 4 and significant wave heights up to, and including 0.5m may be experienced.

In addition, you have the list of safety materials depending of the type of sailing you envisage, usually either at less than 2 NM of a shelter or at 6 NM of a shelter. Here for example is the mandatory equipment lists in France :
https://www.ecologique-solidaire.go...iles/equipement_secu_plaisance_4p_DEF_Web.pdf

By hoping these can be helpful,

 

This is really helpful! Thank you! Hope you didn't use to much time on it. I agree with you on design category C, or maybe B (but that can be difficult). I have to check out the Gene-Hull application. I was planning to use the free version of DelftShip, but Gene-Hull looks easier.

 

That's an interesting analysis of users.

What I find fascinating is how it seems that the expedition users seek to maximise their exposure to the elements - relying on modern protective clothing rather than any sense of accommodation inside the boat. It makes me wonder if boat types more normally associated with warm conditions such as outrigger canoes, catamarans and sailing rafts (small Jangada?) might be favoured for this lightweight on-water expeditioning?

Another thought is that a packable boat might have more appeal since it can easily be transported to interesting locations - maybe an 'expedition' Tiwal would indeed be a very good starting point?

 

Dolfiman started the thread: Gene-Hull : hull generation for sailing yacht early stage design

 

Exactly!

I have been thinking about this, but I'm wondering how much time people are willing to use on rigging. Why are solid canoes and kayaks so much more popular than the foldable ones? I suspect that you have to sacrifice too much for making it packable, both in seaworthiness and in that it will take more time to get it ready for sailing. But I will definitly look more into this.

 

I agree that packable boats can be a pain to get ready. I have a Pakcanoe 150 and it takes about 35-40 minutes - not so much of a problem at the start of the day but a real drag when you are packing up, which does put me off. The videos I have seen of people inflating drop stitch SUP's with a hand pump make it look like a long workout before you even get on the water.

Good folding boats are very seaworthy though, arguably more so than rigid ones. The many adventures (both military and civil) in Klepper kayaks (round Cape Horn, transatlantic etc. are some evidence of this.

Having said all that, something I could just throw on and off the car roof, preferably with minimal rigging for sailing would get my vote.

 

Actually, I am developing several versions of Gene-Hull dedicated for either sailing yacht, double-ended yacht, catamaran, canoe and, under construction, sailing dinghy. I took the opportunity of this thread to test the Dinghy version. That works as you can see but I have not finished the users interface neither the User Guide. Here attached is the application in its current state of advancement (an .ods file to use with either Open office or Libre Office) with the input data in place for the Dinghy, in cells B12 to B83 + an User Guide for another version but which could help you a bit. At short term, a learning by testing process for you could be to try to change some of these input data and see what happens, it is fun and anyway not time consuming as you can stop at any moment (the initial input data being saved in the Hulls storage sheet).

Gene-Hull objective is the early stage of a project, for a hull generation, a 2D sailplan and a preliminary mass spreadsheet, with as output the Hull 2D linesplan, the hydrostatics data, the stability issue (within a specific subroutine, with input data in cells B409, B410 and B411) and the balance issue (the lead) (and I have also in mind to connect a VPP in the further versions). It allows to do fastly a lot of iteration on the hull with at each step an update of all the usual data and ratios used by naval architects. Then, project next step is to switch to the 3D renderings (using the geometrical data also given as output) and the detailed engineering, Gene-Hull cannot do that, you need powerful 3D tools like Delftship.

The current operationnal versions of Gene-Hull are there :
- for sailing yacht :
Gene-Hull upgrade 2,3 https://www.boatdesign.net/threads/gene-hull-upgrade-2-3.60748/
Tutorial for Gene-Hull UE 2,3 https://www.boatdesign.net/threads/tutorial-for-gene-hull-ue-2-3.61498/
- for canoë, attached to the quote#58 of this thread :
Canoe length, efficiency and speed https://www.boatdesign.net/threads/canoe-length-efficiency-and-speed.61301/page-4
- for catamaran :
Gene-Hull version for Catamaran https://www.boatdesign.net/threads/gene-hull-version-for-catamaran.61654/

 

Impossible a priori …, Category B means a minimum weight of 1500 kg and Cat. A a minimum of 3000 kg :
Sailboat Design Categories for Ocean, Offshore, Inshore and Sheltered Waters https://www.sailboat-cruising.com/design-categories.html
… and I would add not wishable : I think you should mention "coastal" to your objective "Dinghy for coastal expeditions" , you should not encourage a sea or ocean crossing with your dinghy purpose even if some adventurers did that successfully at their own risk.

 

Oh, okay. I did not know. Thanks!

 

Project Update 3: Design brief

Name of project: Sailing dinghy for costal expeditions
Goal: To end up with a concept for a new sailing dinghy that can give more people the opportunity to experience nature at sea, powered by the wind.
Target user: The users are interested in exploring nature and challenge themselves both physically and mentally.
Areas of use: It is assumed that the dinghy will be used for daytrips, weekend trips and longer expeditions lasting up to several weeks. Some of the users will sail long distances with up to 10 hours of sailing per day. The dinghy can be used during all seasons, even in cold climates. It is assumed that the dinghy will be used near the coast where it is possible to get to the shore if the weather becomes too challenging.
Market: The main focus is on the Nordic market, but it should be possible to expand.
Delivery: Renders and illustrations of the concept, technical drawings and a scale model.
Deadline: 7. June 2019

Requirements for the dinghy:

Must:

• Not demand a place in a marina
• Stay afloat in case of swamping or capsize
• Be possible for one person to right after capsize
• Be possible for one person to rig, launch and beach
• Be able to carry a crew of two with equipment for camping (around 200 kg)
• Be possible to row or paddle
• Have a hull that is rigid enough for beaching on a rocky shore
• Be possible to secure camping gear to the boat
• Be possible to secure the crew to the boat (so that the dinghy does not blow away when on the side after a capsize)
• Have a centerboard and rudder that can withstand rough treatment
• Have the possibility to reef the sail

Should:

• Have a gennaker, jib or genoa
• Plane
• Have a place for the crew to sit with back support
• Be possible to transport on the roof of a car
• Be easy and fast to rig and launch for one person – max. 30 min.
• Have a hull weight of max. 60 kg.

Could:

• Have room for one or two people to sleep onboard