JP´s Catamaran - Pre study

Introduction

All the introduction is in my Dream page.

Basic design

The design of the intended catamaran is the following:
- Length: 12 meters (40 feet)
- Displacement: 6000 kgs (12000 lbw) - loaded
- Beam: 6 meters (20 feet)
- Sail Area: 80-100 sqm (800-1000 sqf)
- Mast height: 17 m. above water (60 feet, ok with the ICW clearance)
- Rigging: Bi-plane rig, unstayed masts with furling systems, the main being furled in the boom. That would be the desired rig but a thorough comparison is still been made, see below. By the way Aerorig is out of question as Carbospar has closed down.
- Engines: hybrid design, two electric engines with one diesel generator feeding a battery bank, for more details see below and check the site of Solomon Technologies.
- A dagger board to be fitted in one of the hulls, or should it be a swinging board?
- Three double cabins: one master and two doubles. The forth "corner" will be a workshop with generator and water maker.
- Galley and inside steering station to be included at deck level.
- Cockpit will be covered with a targa type 50% solid bimini. The back arch will include dinghy davits. Same arch will include solar panels, radar and radio antennas.
- Electronics: the works: GPS, radar, chart plotter, all instruments (wind, depth, auto pilot), VHF, global satellite phone system, two computers. One for navigation, the other for business.

Hull & Rig Design

At this point I am in contact with Derek Kelsall who is working on a new design called the Coral Sea. This design is partly influence by the work of Richard Glanville of Freewing Masts under the Twinrig concept (check corresponding page). Here below (at left) find a possible application of such a rig (note that it is on a Wharam like hull design which is not considered here - image courtesy of Freewing Masts). So it would probably look more like the image below at right (also from Freewing Masts). Before to say that this kind of design is a nonsense check the first and only (to my knowledge) bi-plane cruising catamaran that you can even charter in New Zealand: the Flying Carpet.

Twinrig

As the hull design is concerned, I am drawn to a roof design a la Lagoon including a cockpit covered with a targa top, here is several pictures that give an idea of my thinking. First the Lagoon 410, then 3 pictures of the Seawind 1200 TEC (from the Seawind site).

I have been comparing different types of rigging possibilities, from the intended unstayed bi-plane (option 2b) to a conventional sloop rig (4a & b), here below the table with descriptions, pros and cons.

Description

Pros

Cons

Option 1a:

Twinrig (2x 46sqm = 92sqm)

with furling booms

- Performance

- Ease of handling

- Possibility to lower masts

- Good windward performance

- Down wind square sail (bow lift)

- Mainsails go out further than 90 deg.
>

- Cost (2 masts, booms)

- Masts depends on each other and the connecting strut

- Gibing (weight of furling booms)

- Main sheets control

Option 1b:

Twinrig with jibs (est. 122sqm) with furling booms

- Performance (top of the list)

- Ease of handling

- Possibility to lower masts

- Best windward performance

- Mainsails go out further than 90 deg.

- Cost (2 masts, booms, jib furling gear)

- Masts depends on each other and the connecting strut

- Gibing (weight of furling booms)

- Main sheets control

Option 2a:

2 Freewing masts = 92sqm

with furling booms

- Masts are independent

- Ease of handling

- Mainsails go out further than 90 deg.

- Cost (see above 1a)

- Masts are heavier (no stays)

- Need space below for bury

- Gibing (weight of furling booms)

- Main sheets control

Option 2b:

2 Freewing masts + jibs on balestrons = est. 120sqm
Mains with furling booms

- Masts are independent

- Ease of handling

- Gibing (jibs counter act)

- Mains go out further than 90 deg.<

- Cost (see above 2a, probably the most expensive of all options)

- Masts are heavier

- Need space below (bury)

- Main sheets control
- Rig dimensions dictated by space beetween masts to avoid main boom clashing other side balestron.

Option 3a:

1 Freewing mast with jib =

46sqm + 24sqm (est.) = 72sqm

one furling boom (MK2)

- Cost (one mast, one boom)

- Known option

- Ease of handling (best of all, including gibing)

- Mains go out further than 90 deg.

- Performance

- bury (central position)

- Heavier than Twinrig

Option 3b:

Same as 3a but with mast in one hull (proa style, but hulls same lengths)

- Cost (see above)

- Ease of handling (as 3a)

- Mains go out further than 90 deg.

- unproved design (asymmetry)

- Performance (to improve bigger boom and mast could be considered)

- Main sheet control

Option 4a:

Conventional stayed aluminium mast incl. jib = est. 90sqm

with furling boom (Profurl MK2)

- Cost (one mast, one boom)

- preferred option by Profurl
(aluminium mast)

- Stays

- Gibing

- Large loads on rig, hulls and bridge deck

Option 4b:

Conventional stayed aluminium mast = est. 110sqm

With furling boom (Profurl MK3)

- Performance (ratio goes up to around 57, like the Crowther 42)

- Preferred option by Profurl (aluminium mast)

- Stays

- Gibing (bigger boom)

- Handling (biggest main sail)

- Large loads on rig, hulls and bridge deck

Option 5:

Unstayed masts with wishbone mains (no jibs) see Wyliecat web site.
100 sqm

- Less weight (mast is a tube, wishbone is lighter than furling booms, no jib furling gear)
- Lower cost if using standard masts (?) - Main sheet control (does not need track)<
- Performance
- Mains go out further than 90 deg.

- Reefing in place of furling mains
- Need sail covers and lazy jacks

I need some more data on costs to have a better view, anyone can comment, the pros and cons have been discussed with the designers and others have contributed as well (e.g. from the Multihull mailing list, thanks to all!).
Performance has been estimated using a sail/weight ratio (like the Bruce number but calculated on decimal measurements, Bruce # also included). The table below refers to existing catamarans in the range of 37 to 44 ft. The Kelsall Coral Sea with the Twinrig is at line 13 with a Bruce # of 1.33, so it does not look like an extreme design but it should be in the top half.

	Brand	Model	Length ft	Length M	Displ. Kgs	Total sail M2	Ratio	Bruce #
1	Crowther Multihulls	Crowther 42	42	12,80	6000	109,0	0,575	1,448
2	St. Francis	St Francis 44	44	13,45	7000	115,0	0,561	1,413
3	Multicap Caraibes	Punch 11.50	40	12,00	5000	90,0	0,555	1,398
4	Soubise Plaisance	Freydis 42	42	12,80	7000	109,0	0,546	1,375
5	Atelier Outremer	Outremer 40 std	40	12,10	5500	92,0	0,543	1,369
6	Catana France	Catana 431	43	13,10	8000	118,0	0,543	1,369
7	Crowther Multihulls	40 MK II	40	12,20	5450	90,0	0,539	1,358
8	Crowther Multihulls	Crowther SP40	40	12,19	6400	100,0	0,539	1,357
9	Nauticomposites	Bohème 43	43	13,45	5900	94,0	0,537	1,352
10	Farier Marine	F41	41	12,10	5300	87,2	0,536	1,350
11	Schionning	Cosmos 1250S	41	12,50	7000	104,0	0,533	1,343
12	Bader Catamarane	Sunact 40	40	12,09	5000	82,0	0,530	1,334
13	Kelsall	Coral Sea 40	40	12,00	6000	92,0	0,528	1,330
14	Schionning	Wilderness 1230	42	12,30	6350	95,0	0,526	1,326
15	Atelier Outremer	Outremer 38	38	11,60	4200	72,0	0,526	1,325
16	Brazapi	Brazapi 40	40	11,99	6500	95,0	0,522	1,316
17	PDQ Yachts	PDQ 42 Antares	42	12,20	7250	102,0	0,522	1,315
18	Alliaura Marine	Privilège 435	43,5	13,45	8300	111,0	0,520	1,311
19	Moorings Yachting	Moorings 4200	42	12,62	8650	114,0	0,520	1,311
20	Catana France	Catana 401	40	12,50	6500	94,0	0,520	1,309
21	Fountaine Pajot	Belize 43	43	13,00	8600	111,0	0,514	1,296
22	Edel Catamaran	Helios 38	38	11,68	5000	76,7	0,512	1,291
23	Multicap Caraibes	Punch 12.50	42	12,70	6500	90,0	0,508	1,281
24	Voyage Catamaran	Voyage380	38	11,50	6000	85,0	0,507	1,279
25	Fountaine Pajot	Athena 38	38	11,60	6000	85,0	0,507	1,279
26	Edel Catamaran	Helios 42	42	12,68	6400	86,0	0,499	1,259
27	Seawind	1200 TEC	39'4	12,10	8100	100,0	0,498	1,255
28	Fountaine Pajot	Lavezzi 40	40	11,90	7000	90,0	0,496	1,250
29	Manta USA	Manta 42	41,8	12,75	6125	82,0	0,495	1,247
30	Prometa	Cat. 41	41	12,60	9000	103,0	0,488	1,230
31	Dufour	Nautitech 395	40	11,98	6600	82,5	0,484	1,220
32	Lagoon/CNB	Lagoon 410	41	12,37	7400	89,0	0,484	1,220
33	Alliaura Marine	Privilège 37	37	11,17	6500	80,0	0,479	1,208
34	Fortuna Catamarans	Coralinne 40	40	12,20	7200	85,2	0,478	1,205
35	Manta Enterprises	Manta 40	40	12,00	5900	74,0	0,476	1,200
36	Pedigree catamaran	Farrier 41	42	12,00	7700	87,0	0,472	1,190
37	Robertson & Caine	Moorings 3800	38	11,00	7300	83,0	0,470	1,183
38	Lagoon/CNB	Lagoon 380	38	11,55	7120	79,0	0,462	1,164
39	Prometa	Cat 38	38	11,45	7000	75,0	0,453	1,141
40	Prout	Prout 38	38	11,58	6500	70,5	0,450	1,134
41	Prout	Prout 39	39	11,90	8500	75,0	0,424	1,069

Electric propulsion

I am really attracted to the idea of electric propulsion, I have been following the development of the Electric Wheel at Solomon Technologies. Lagoon Catamarans will now offer these engines as an alternative, see the Catamaran Company announcement.
I have been in contact with Solomon Technologies and have drawn a design, based on the ST37 engines, which must be fine-tuned but give a reasonable idea (check here). It can also be described as follows:

Description	Item Code	Quantity	Dimensions (inches)	Weight (lbs)	Tot. Weight
ST37 motor 4.5kw	ST37	2	13Dia x 13L	78	156
Battery Charger	KS 091 127	1	16 x 21.5 x 3	42,5	42,5
Main Distribution Box	MDB-TW	1	8x10x10	?
Safety Power Mgt & Distr. Panel	SPDM	2	15x12x6	10	20
Battery Cable Assembly	CA-01	1	NA	50	50
Motor mounts	MTS-RBR	2	NA	4,5	9
Digital read-out	E-Meter	1	2" Dia		0,5
Sub-Total					278
Batteries Group 4D	LL4DL	12	20.75”Lx8.71”Wx10.44H	135	1620
Mini Electronic Throttle control	MN-CTRL N2	1	NA		0,5
Digital Amp meter	AMMD	2	NA
144V DC Generator 9kw	Gen 9	1	44.8"Lx23.6"w 25"h	550	550
Genset starting battery	LL31T	1	12,9"Lx6,75"Wx9,27"H	69	69
Inverter 144DC to 120 AC (3000 Watts)	INV3	1	13x25,5x9	150	150
DC/DC Cross charger/Converter	DDH300V15	1	7 x 9 x 3	4	4
Sub-Total					2393,5
Total weight in pounds					2671,5

I have also worked on the electrical loads on the house batteries (2x230Ah) and as they are charged from the main battery bank through a cross charger, they should not discharge below some 70% as long as you maintain a correct charge in the engine batteries. These would be recharged when and if needed with a diesel generator. Basically it is expected that the regenerating possibility of the electric engines will maintain the batteries charged. Solar pannel have also been included in the study. Worst case according to current estimates would be to use the generator about one hour per day while sailing or at anchor.
In the case of motoring the battery bank would be maintained with the generator. The electrical engines would run at 80% of power and the system could be used on a 24h basis (speed probably around 6-7 knots).

Project Planning

This whole project has been planned with a tentative objective which is to be sailing by the summer of 2007 and have the opportunity to see (in Portugal?) the next America's Cup defence by the Alinghi team! The whole plan looks something like this:

Project plan

As you can see, I should be getting a study plan early 2004 and will update this site as we go along, comments are always welcome: [email protected]

Thanks

I would like to thank all the people that one way or another are helping with comments and ideas, some of them are appearing in the links below.

Links

Updated but never finished - August 31, 2003 - [email protected]
Back to JP´s Corner home page

JP´s Catamaran - Pre study

Introduction

Basic design

Hull & Rig Design

Electric propulsion

Project Planning

Thanks

Links

Design and marine architects

Boat builders

Others