alpa 42 sailboat

Review of Alpa 42

Basic specs..

The hull is made of fibreglass. Generally, a hull made of fibreglass requires only a minimum of maintenance during the sailing season.

The boat is equipped with 401.0 liter fresh water capacity.

The Alpa 42 is built with a ketch rig. A ketch rig is generally considered easier to handle, because the sails are smaller, and because it can sail on most points to the wind with one sail completely taken down for repair or while reefing. The sail configuration of a ketch allows for better comfort and stability when sailing downwind or on a broad reach.

The Alpa 42 is built with a fin keel. A boat with a fin keel is more manoeuvrable but has less directional stability than a similar boat with a full keel.

The boat can only enter major marinas as the draft is about 1.85 - 1.95 meter (6.07 - 6.37 ft) dependent on the load. See immersion rate below.

Alpa 42 may be equipped with an inboard Perkins diesel engine

The fuel tank has a capacity of 201.0 liters (53 US gallons, 44 imperial gallons).

Sailing characteristics

This section covers widely used rules of thumb to describe the sailing characteristics. Please note that even though the calculations are correct, the interpretation of the results might not be valid for extreme boats.

What is Capsize Screening Formula (CSF)?

The capsize screening value for Alpa 42 is 1.47, indicating that this boat could - if evaluated by this formula alone - be accepted to participate in ocean races.

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 8.2 knots. The term "Theoretical Maximum Hull Speed" is widely used even though a boat can sail faster. The term shall be interpreted as above the theoretical speed a great additional power is necessary for a small gain in speed.

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Alpa 42 is about 263 kg/cm, alternatively 1473 lbs/inch. Meaning: if you load 263 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 1473 lbs cargo on the boat it will sink 1 inch.

Sailing statistics

This section is statistical comparison with similar boats of the same category. The basis of the following statistical computations is our unique database with more than 26,000 different boat types and 350,000 data points.

What is Motion Comfort Ratio (MCR)?

What is L/B (Length Beam Ratio)?

What is a Ballast Ratio?

What is Displacement Length Ratio?

What is SA/D (Sail Area Displacement ratio)?

Maintenance

When buying anti-fouling bottom paint, it's nice to know how much to buy. The surface of the wet bottom is about 45m 2 (484 ft 2 ). Based on this, your favourite maritime shop can tell you the quantity you need.

Are your sails worn out? You might find your next sail here: Sails for Sale

If you need to renew parts of your running rig and is not quite sure of the dimensions, you may find the estimates computed below useful.

This section is reserved boat owner's modifications, improvements, etc. Here you might find (or contribute with) inspiration for your boat.

Do you have changes/improvements you would like to share? Upload a photo and describe what you have done.

We are always looking for new photos. If you can contribute with photos for Alpa 42 it would be a great help.

If you have any comments to the review, improvement suggestions, or the like, feel free to contact us . Criticism helps us to improve.

Alpa 42 - Alpa / STW003804

cabin cruiser

overall length

hull length

waterline length

standard draft

minimum draft

displacement

diesel tank

mast height

Accomodation layouts

standard version

If you find some wrong or lacking data of this boat, you can propose an update.

Technical forum: alpa 42.

I am looking for the technical manual of the Alpa42 ketch. Can you help me. Giancarlo Moro tel +393482650815. Mail: [email protected] 17/08/2022 by stw-2210

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• Sailboat Guide

Alpa 42 is a 39 ′ 4 ″ / 12 m monohull sailboat designed by Sparkman & Stephens and built by Alpa Yachts starting in 1973.

Rig and Sails

Auxilary power, accomodations, calculations.

The theoretical maximum speed that a displacement hull can move efficiently through the water is determined by it's waterline length and displacement. It may be unable to reach this speed if the boat is underpowered or heavily loaded, though it may exceed this speed given enough power. Read more.

Classic hull speed formula:

Hull Speed = 1.34 x √LWL

Max Speed/Length ratio = 8.26 ÷ Displacement/Length ratio .311 Hull Speed = Max Speed/Length ratio x √LWL

Sail Area / Displacement Ratio

A measure of the power of the sails relative to the weight of the boat. The higher the number, the higher the performance, but the harder the boat will be to handle. This ratio is a "non-dimensional" value that facilitates comparisons between boats of different types and sizes. Read more.

SA/D = SA ÷ (D ÷ 64) 2/3

• SA : Sail area in square feet, derived by adding the mainsail area to 100% of the foretriangle area (the lateral area above the deck between the mast and the forestay).
• D : Displacement in pounds.

Ballast / Displacement Ratio

A measure of the stability of a boat's hull that suggests how well a monohull will stand up to its sails. The ballast displacement ratio indicates how much of the weight of a boat is placed for maximum stability against capsizing and is an indicator of stiffness and resistance to capsize.

Ballast / Displacement * 100

Displacement / Length Ratio

A measure of the weight of the boat relative to it's length at the waterline. The higher a boat’s D/L ratio, the more easily it will carry a load and the more comfortable its motion will be. The lower a boat's ratio is, the less power it takes to drive the boat to its nominal hull speed or beyond. Read more.

D/L = (D ÷ 2240) ÷ (0.01 x LWL)³

• D: Displacement of the boat in pounds.
• LWL: Waterline length in feet

Comfort Ratio

This ratio assess how quickly and abruptly a boat’s hull reacts to waves in a significant seaway, these being the elements of a boat’s motion most likely to cause seasickness. Read more.

Comfort ratio = D ÷ (.65 x (.7 LWL + .3 LOA) x Beam 1.33 )

• D: Displacement of the boat in pounds
• LOA: Length overall in feet
• Beam: Width of boat at the widest point in feet

Capsize Screening Formula

This formula attempts to indicate whether a given boat might be too wide and light to readily right itself after being overturned in extreme conditions. Read more.

CSV = Beam ÷ ³√(D / 64)

From the same hull mold used to built the ALPA 12.7 (1969). The tooling was later purchased by the Zuanelli yard where, with a few modifications, it became the Zuanelli 42.

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• About Sailboat Guide

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The Alpa 42 is a 39.37ft staysail ketch designed by Sparkman & Stephens and built in fiberglass by Alpa Yachts (ITA) since 1973.

8 units have been built..

The Alpa 42 is a moderate weight sailboat which is under powered. It is stable / stiff and has an excellent righting capability if capsized. It is best suited as a heavy bluewater cruising boat. The fuel capacity is average. There is a good water supply range.

See all sailboats built by Alpa Yachts (ITA)

See all sailboats designed by Sparkman & Stephens

Alpa 42 for sale elsewhere on the web:

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1974 alpa 42 for sale

• 1974 alpa 42

Alpa 42 ( 1974 ) for sale

English This Sparkman & Stephens Alpa 42 has had a major re-fit with A new Thornycroft engine, Kiwi Grip deck, New Rigging and...

ALPA 42 KETCH

Alpa 42 ketch.

Place de port disponible (à vendre ou à louer)

1974 Alpa Alpa 42 sailboat for sale in Outside United States

VIEUX MALIN - ALPA 42 1974 (n. 7) Visible in Linton Bay Marina, Panama Belgian Flag PROFURL Genoa roller (2008)...

For Sale: Sparkman & Stephens Alpa 42

Sparkman and stephens 42.

This Sparkman & Stephens Alpa 42 has had a major re-fit with A new Thornycroft engine, Kiwi Grip deck, New Rigging and sails....

Alpa 42 Ketch Sparkman & Stephens ( 1974 ) Usato

Alpa 42 ketch sparkman & stephens.

Consigliata visita a bordo. Imbarcazione in perfette condizioni, completamente refittata e pronta a navigare. Nessun lavoro da eseguire. Tanti accessori tra cui,...

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