06.0_Batman_Naval

Naval Architecture

This is a page to discuss the "Naval Architecture" of Protei. By this we mean the traditional boat design parameters that go into engineering an ocean vessel. The main collaborators in this page are Roberto, Gonzalo and Javier but anyone is free to contribute.

VPP (Velocity Prediction Program):

This is where the Protei team collaborates with the Naval Architects in Chile to iteratively design the vessel. We will be coming up with overall dimensions and hull/keel/sail combinations that are going to be inputed in a VPP (velocity prediction program) by Javier in Chile. From those results we will propose new designs, till we arrive at the desired characteristics for the vessel. The VPP results can be accessed below:

VPP Results (added 1st July 2011 and dimensions agreed upon 24 June 2011)

In Naval Architecture many times progress is achieved by finding existing boats with roughly the same proportions and desirable characteristics and imitating her design while changing some parameters around. Because Protei is such a one of a kind vessel, it might be hard to find boats that fit the purpose but nevertheless we should still look at designs like this for ideas. Below is the space in which to add these other boats:

Here are the dimensions used for this iteration of the design:

Dimension	Notation	Full scale	Units
Length	Lpp	5.8	m
Beam	B	0.84	m
Displaced	Volume	V	0.448
Mass	m	0.4592	t
Sail area to vol. ratio	AS/(V^2/3)	16.5	-
Keel depth	Dk	1.5	m
Kerel length	Lk	0.3	m
Keel area	Ak	0.45	m2
Keel bulb weight	Wkb	80	kg
Block coeficcient	Cb	0.5	-
Number of sails	n	1	-
Calculated Draft	T	0.18	m
Sail Area	AS	9.66	-

The table below shows the variations on dimensions (courtesy of Javier and the VPP software from Future Ship). these are done based on a hull that is 4m long (LOA)

	Mast Height [m] alturas	Speed at 10 kn TWS of wind [kn]	Heel at 60˚ [˚]	heel.pdf	vs.pdf
protei 9	5.5	3	33	protei9 heel.pdf	protei9 Vs.pdf
protei 10	5	2.9	32	protei10 heel.pdf	protei10 Vs.pdf
protei 11	4.5	2.7	30	protei11 heel.pdf	protei11 Vs.pdf
protei 12	4	2.6	29	protei12 heel.pdf	protei12 Vs.pdf

	Keel Variations (m) Lateral Area [m2]	Wetted Area sup mojada [m2]	keel Chord cuerda [m]	Mast Height altura mastil [m]	Beam manga [m]	Speed [kn] at 10 kn TWS of wind	Heel at 60˚ [˚]	heel.pdf	vs.pdf
protei 13	2.3	4.6	2.3	5	1	2.8	31	protei13 heel.pdf	protei13 Vs.pdf
protei 14	2.5	5	2.5	5	1	2.8	31	protei14 heel.pdf	protei14 Vs.pdf
protei 15	3	6	3	5	1	2.7	30	protei15 heel.pdf	protei15 Vs.pdf
protei 16	3.5	7	3.5	5	1	2.6	30	protei16 heel.pdf	protei16 Vs.pdf
protei 17	3.5	7	3.5	5	1.3	2.9	29	protei17 heel.pdf	protei17 Vs.pdf
protei 18	3.5	7	3.5	4.5	1.3	2.7	28	protei18 heel.pdf	protei18 Vs.pdf

Vessel Design:

We must first decide on what are our design constraints for the vessel (in a marine engineer sense). This is a preliminary list:

• Length overall (LOA): 5-6m This parameter will set a "theoretical speed limit" for our vessel. This speed limit is denoted the "hull speed" of the vessel and is when the bow and stern waves are constructively interfering to put the vessel at a trough and thus impede it from going faster. Some vessels can overcome this speed (especially small ones, and those that plane over the surface)

The equation for the hull speed is: v = 1.34 * (LOA)^0.5 where v is in knots and LOA is in feet (nasty imperial units)

• Steady-State Speed: 2-3 kts (this is with boom) This is the speed that we want protei to maintain, the actual value will depend a lot on the polar plot generated by VPP (this is also influenced by the load)

• Able to toll an oil boom (resistance unknown) We will run some extremely primitive tests in the sailing club this Saturday to get an idea of the order of magnitude of the resistance.

• Heeling angles and stability

• Hull Displacement?

http://www.kastenmarine.com/_pdf/coefficients_of_form_equations.pdf

• Sail Area The sail area is going to depend primarily on the wetted surface of the vessel (because at low speeds the viscous resistance due to wetted area is more important than the wave making resistance) A good rule of thumb is the ratio between the displacement^2/3 and sail area as follows:

15 to 17 = SA / (Displacement)^(2/3)

The above ratio is between 15-17 for non racing sailboats (for racing sailboats this can go higher than 20, and even more for multihulls)

http://www.kastenmarine.com/_pdf/sail_area_ratios.pdf

• Hardware Carrier: 100-150kg of load (includes batteries, rig and electronics) but not the ballast (although we could use the batteries as ballast)

http://www.kastenmarine.com/design_calcs.htm

Thanks to Kasten Marine (kastenmarine.com) for their information.

Sail Rig Design: (look here for info)

So far we are weighing the possibilities of three different types of rig, feel free to suggest more!

Marconi Rig (or Bermuda Rig)

This is the rig used by many (if not most) sailboats today. It involves a triangular sail that slides into the mast and it attached to a boom from the clew. Many times the mains'l is accompanied by a jib (like in the popular sloops)So far all the Protei with sails have used a marconi type rig for the sails.

Advantages: Very Simple Rig

Gaff Rig This rig is also very popular today. This is a squares'l rig where the luff is attached to the mast (most of the time by rings) and the head of the sail is attached to another spar (the gaff), and the foot is attached to the boom. Normally, a gaff rigged sail is hoisted using two halyards: the peak halyard and the throat halyard.

Advantages:

• More sail area per height of the mast.
• Lower Centre of Effort (less heeling moment)
• More Tolerance to high winds than Marconi sail.

Lateen Rig (or also called 'latin' by some)

In a lateen rigged vessel the sail is triangular and it is held up by a spar that is attached at a medium height of the mast. These sails are extremely aerodynamic and offer excellent upwind sailing. However tacking is more complicated because the spar needs to be moved after tacking.

Advantages: Good upwind sailing

Disadvantages:

• Reduced Sail Area
• Difficulty to tack

Standing Rigging (stays and shrouds):

An important part for the construction of a sailboat is the "standing rigging" this refers to the "wires" (shrouds and stays) that hold the mast upright.

We will most likely have only one mast in our vessel, so we could use 1-4 stays (or none!). Larsson recommends a minimum angle of 9 degrees between the shroud and the mast.

Running Rigging (lines):

These are the halyards, sheets, downhauls, cunningham, outhauls that in a regular vessel are responsable for hoisting/striking and trimming a sail. In protei we will be using a limited amount in order to prevent entanglement.

Free standing mast (no stays nor shrouds): Inspired from a news post on the Subzero boat : a rotating mast with a kind of chinese Jonque sail. The mast doesn´t necessarily need to rotate, maybe only the sail can rotate around the mast.

Have a look at this great web resource from Sponberg Yacht Design, Florida, on such masts, with other inspiring designs, including traditional ones, which have the merit to be simple to build and use local & natural materials. In the Articles section, Sponberg also provides with basic Naval architecture ratios for small crafts and simple performance ranking spreadsheets ("the S number"), which looks very interesting. A great read!

Keel Design:

The keel is an important part of the design, especially because we depend on it for steering and self righting. We need to agree on:

Shape of the keel (how full will the keel be?) -important for wetted surface area and for steering Ballast Size and shape?

Rudder Design:

We will be designing a rudder (with help of VPP) so we can have something to test the effectiveness of the articulation against.

The rudder will probably something we can get second-hand from a sail club but some research will be done in order to make sure everything is in balance.

Construction Materials:

A very important part of Protei is that it is a DIY project. Meaning that most of the materials we use have to be easily accesible to anyone.

• Sails: Dacron or Mylar.
• Rudder: Wood
• Hull+Keel: Wood, Fiberglass, pvc tubes, foam.
• Ballast: Sand (or lead?)
• Mast: Aluminium, Reinforced PVC, carbon (probably too adventurous)
• Rigging: Steel Cable and Lines.

Again feel free to add more stuff to the list! --> What about Green composites? I strongly recommend to talk to APC Composite in Northern Sweden - ask Henrik to translate the Swedish, the English page is very limited.