Choosing The Right Tashiba Boat: A Comprehensive Guide

The Tashiba is a long-keeled cutter sailboat designed by Bob Perry and built in Taiwan by Ta Shing Yacht Builders. The Tashiba comes in 31, 36, and 40-foot models, all of which are monohull designs. The 31-foot model was built between 1986 and 1988, while the 36-foot model was introduced in 1986. The Tashiba 40, the largest of the three models, has a displacement of 29,000 lbs, a waterline length of 34'6, and a sail area of 865 sq ft. All three models are known for their spacious interiors and luxurious finishes. When choosing a Tashiba boat, it is important to consider factors such as the intended use, performance specifications, and personal preferences.

Sail area/displacement ratio

When picking a Tashiba boat, it is important to consider its Sail Area-Displacement Ratio (SA/D). This ratio is a calculation used to express how much sail a boat carries relative to its weight. It is an indicator of the boat's performance—the higher the SA/D, the more powerful the boat.

The SA/D is a "non-dimensional" value, meaning it facilitates comparisons between boats of different types and sizes. For example, a 30-foot boat with an SA/D of 20 will have just as powerful a rig as a 60-foot boat with the same SA/D.

In general, a boat with an SA/D under 15 would be considered under-canvased, while values above 15 indicate reasonably good performance. Anything above 18-20 suggests high performance, provided the boat has sufficient stability and a low enough displacement-length ratio to take advantage of its abundant sail area.

The Tashiba 31, for instance, has a sail area of 552.50 ft² and a displacement of 13,790 lb. This gives it an SA/D of around 16.7, which indicates reasonably good performance.

The SA/D is an important consideration when choosing a boat, as it gives an idea of how the boat will perform under sail. However, it does not provide information about how the boat will behave in a storm or upwind. For a more precise understanding of the boat's performance, other factors such as hull speed, ballast/displacement ratio, and displacement/length ratio should also be taken into account.

Ballast/displacement ratio

When selecting a Tashiba boat, it is important to consider the ballast/displacement ratio. This ratio is a critical factor in determining the stability, stiffness, and overall performance of the boat.

The ballast/displacement ratio indicates the amount of weight placed in the boat to maximise stability and minimise the risk of capsizing. A higher ratio translates into a stiffer and more powerful boat that can better withstand strong winds and rough seas.

For the Tashiba 31, a ballast/displacement ratio of less than 40 would indicate a less stiff and less powerful boat, while a ratio above 40 would mean a stiffer and more powerful vessel. The ballast/displacement ratio for the Tashiba 31 is calculated as follows:

> Ballast/Displacement Ratio = Ballast (lbs) / Displacement (lbs) * 100

For example, if the ballast is 4,700 lbs and the displacement is 13,790 lbs, the calculation would be as follows:

> Ballast/Displacement Ratio = 4700 / 13790 * 100 = 34.08

So, for this example, the Tashiba 31 would be considered less stiff and less powerful, as the ratio is less than 40.

Similarly, for the Tashiba 40, a ballast/displacement ratio of 40 or more is desirable for a stiffer and more powerful boat. The calculation method is the same as for the Tashiba 31.

When choosing a Tashiba boat, it is essential to consider your intended usage and the sailing conditions you are likely to encounter. If you plan to sail in strong winds or rough seas, selecting a boat with a higher ballast/displacement ratio will provide a stiffer, more powerful, and stable platform. Conversely, if you intend to sail in calmer waters and prioritise manoeuvrability over stiffness, a lower ballast/displacement ratio may be more suitable.

Additionally, it is worth noting that the ballast/displacement ratio is just one aspect of boat design and performance. Other factors, such as sail area, hull design, and overall weight, also play a significant role in the boat's overall performance and should be considered when making a purchase decision.

Displacement/length ratio

When selecting a Tashiba sailboat, it is important to consider its Displacement/Length ratio (D/L ratio). This ratio is a tool used by yacht designers to evaluate the boat's performance and characteristics. The D/L ratio measures how heavy a boat is relative to its waterline length, and it is calculated by dividing the boat's displacement in long tons (2,240 pounds) by the cube of one one-hundredth of the waterline length (in feet).

The D/L ratio provides a more nuanced understanding of the boat's performance. A lower D/L ratio indicates that less power is required to drive the boat to its nominal hull speed, and it is more likely to exceed that speed. Conversely, a higher D/L ratio means the boat can carry a heavier load more comfortably. For cruising, a moderate D/L ratio is generally recommended, with coastal boats favouring the lower end and offshore boats the higher end of this range.

• Ultralight: Below 100
• Light: 100-200
• Moderate: 200-300
• Heavy: 300-400
• Ultraheavy: Above 400

Additionally, the D/L ratio can be used to compare the relative "heaviness" of boats, regardless of their size. For example, two boats with the same D/L ratio but different waterline lengths would be considered equally heavy relative to their respective waterline lengths.

When evaluating boats based on their D/L ratios, it is important to use a realistic displacement value, as the ratio can vary significantly depending on the displacement used in the calculation. It is recommended to correct the displacement figure published by the boat's builder upwards to account for the load the boat normally carries when sailing.

In summary, the Displacement/Length ratio is a crucial factor to consider when choosing a Tashiba boat, as it provides insights into the boat's power requirements, speed potential, load capacity, and comfort level during cruising.

Comfort ratio

The comfort ratio is a measure of motion comfort, comparing yachts of similar size and type. It was created by Ted Brewer and is based on the fact that faster motion is more upsetting to the average person. The comfort ratio formula is:

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

Where:

• D = Displacement of the boat in pounds
• LWL = Waterline length in feet
• LOA = Length overall in feet
• Beam = Width of boat at the widest point in feet

The comfort ratio categorises boats as follows:

• Numbers below 20 indicate a lightweight racing boat, small dinghy, etc.
• 20 to 30 indicates a coastal cruiser
• 30 to 40 indicates a moderate bluewater cruising boat
• 40 to 50 indicates a heavy bluewater boat
• Over 50 indicates an extremely heavy bluewater boat

The comfort ratio is one of several specifications to consider when choosing a boat. The Tashiba 31, for example, is a 35' 4" monohull sailboat with a comfort ratio of 30-40, categorising it as a moderate bluewater cruising boat. The Tashiba 40, on the other hand, has a comfort ratio of 41.5, which is high for a cruising boat, meaning it has a smooth and gentle motion in waves but a slow and heavy feel at the helm.

Capsize screening formula

The Capsize Screening Formula (CSF) is a method of determining a boat's ability to resist capsizing. It is calculated using the following formula:

CSF = Beam / ((Displacement/64.2)1/3)

Where the beam is the width of the boat at its widest point, and displacement is the weight of the boat in pounds. The resulting value indicates the boat's suitability for ocean racing. A CSF value of less than or equal to 2 is considered suitable for ocean passages, while values greater than 2 are more suitable for coastal cruising.

It's important to note that the CSF is a "`rough`" estimate and does not consider factors such as hull shape or ballast location. As a result, two boats with the same CSF may have very different stability characteristics due to differences in hull design and ballast configuration.

The CSF came into use after the 1979 Fastnet race in England, where a storm caused the destruction of many yachts, with 75 out of 303 yachts capsizing. The Cruising Club of America (CCA) developed the CSF to compare boats based on readily available data, specifically their beam and displacement.

While the CSF is a widely used screening tool, it is controversial due to its simplicity and lack of consideration for other factors influencing a boat's stability. More comprehensive stability assessments, such as the EU's STIX index, consider a wider range of factors but require more detailed information.

When choosing a Tashiba boat, or any boat for that matter, understanding the capsize screening formula and other stability indicators is crucial to ensure the vessel is suitable for its intended use and provides a safe boating experience.

Frequently asked questions