YANMAR Technical Review

Abstract

The EX Series, which takes advantage of Yanmar's expertise in diesel engines with a single shaft, was released for recreational fishing. The first model, the EX35, was released in 1995. The development concept of the EX35 was "hull for fishing + bridge for pleasure", and at this point the focus was on suitability for fishing.

Then, market demand shifted from fishing to occupant comfort. The EX33A, featuring a large cabin, was released as part of the Wide EX Series. This gave rise to the second golden age of the EX Series. Shifting to passenger comfort was a turning point, but the EX Series has continued to earn a favorable reputation, due partly to the recovery of the economy.

In 2014, the long-awaited EX30B installed with the 8LV350J electronically controlled engine was released. In addition to its suitability for fishing, the eco-friendly EX30B achieves perfect livability. This review is an overview of the newly designed boat.

1. Introduction

Although the EX30B is the smallest model in the Wide EX Series, Yanmar did not think "It's the smallest model so there's nothing special we can do", but rather based its design concept on "We will utilize the advantages of a small size to create a unique model."

To achieve this, Yanmar started development based on the following basic design policies.

• (1)Achieve fishing space and cruising comfort of upper grade boat => Adoption of a new boat design and new propulsion system
• (2)Achieve extremely low noise => Installation of 8LV350J electronically controlled engine
• (3)Achieve a spacious cabin => An original new design

These design objectives set an extremely high hurdle.

2. Product Overview

The following is an overview of EX30B.

2.1. Styling

2.2. Main Specifications

Table 1 Main Specifications

Table 2 Installed Engine

3. Incorporated Technology and Effects

3.1. Adoption of New Propulsion System and New Boat Shape

In general, when the boat length is reduced, motion performance in the direction of the boat length worsens. This is because the cycle of motion in the vertical direction becomes shorter and its amplitude increases, reducing occupant comfort. To overcome this issue, an "internal propeller, internal rudder" system has been adopted in this boat instead of the previous "external propeller, external rudder" system.

In terms of the boat design, an optimum chine line and fin keel has been combined, and a newly designed flare with a unique outer chine has been adopted, which greatly reduces punching impacts. As a result, vertical acceleration at the bow is reduced by 25%, achieving extremely gentle occupant comfort even when cruising through waves.

Also, by adopting this system, motion performance does not worsen even though it is a wide boat design, enabling a level and spacious deck to be provided. (Fig. 4) At the same time, the boat has been made more suitable for fishing by the inclusion of a walk-around side aisle and a bulwark with the optimum height.

3.2. Installation of 8LV350J Electronically Controlled Engine

In the past, Yanmar tried many times to release electronically controlled engines, but they did not become popular in the domestic market. This time, however, the sales department participated from the product planning stage, creating a product that emphasized the appeal of such engines.

In terms of vibration and noise, the unique high performance of the 8LV350J delivers excellent results. In particular, combining this engine with a soundproof structure that includes the unique double deck of the EX Series achieved a noise level of 57 dB (A) (when stationary), an excellent result for a diesel inboard boat.

A high performance level not seen before has also been achieved for the vibration feeling level. There is no resonance at all in any speed range, minimizing the stress caused by vibration.

The adoption of an electronically controlled engine has also improved product strength from various other perspectives. First, the adoption of the VC10 control system enables engine information to be acquired in real time. This greatly improves safety by ensuring the user is continually aware of the engine condition. The boat also features panel meters made by Livorsi that have excellent visibility, greatly improving the design around the operator seat. In particular, the latter directly improves product value in terms of appearance, and also improves product strength through a synergistic effect with the appearance and ease of use of the control lever.

Second is the excellent acceleration. The response when the boat accelerates relative to the movement of the control lever is far superior to engines with conventional mechanisms. This response lag is one of the main causes of stress on the boat operator, but this boat has extremely good operability to remove all such stress.

Also, although black smoke emission usually has an inverse relationship to rapid acceleration, no black smoke at all is emitted. This combined with a more lightweight boat design creates a product with low fuel consumption that is gentle to the environment.

3.3. Spacious Cabin

As previously described, the Wide EX Series provides a level and spacious deck, but at the same time it also achieves a spacious cabin by tilting forward the front window.

Previously, a tilted front window gave rise to two major issues. The first was styling that affected user appeal, and the second was the manufacturing method for fiber-reinforced plastic (FRP) boats. The first issue was addressed by suggesting a total design to dealers who had conducted market research. Regarding the second issue, the undercut that causes a problem during FRP molding was overcome by using an integrated structure made from a separate frame for the front window and side windows.

By adopting the previously described structure, a cabin space ratio of 98% was achieved for the 33 ft boat despite this being smallest model in the series, and while providing a private toilet with enough space for an adult to stand and a berth space where people can lie down (Fig. 11).

By tilting forward the front window, forward visibility while cruising has also been greatly improved. Combining this with a new propulsion system minimizes the boat trim angle and improves visibility from the windows, providing a spacious cabin that enables stress-free boat operation.

4. Evaluation and Results

4.1. Maintaining Suitability for Fishing

The minimum requirements for a fishing boat are a walk-around deck and a large stern deck space. Even though this is the smallest model in the series, it has been recognized as maintaining its suitability for fishing. Because the features that are beneficial for fishing reduce cruising performance, it was important to overcome these issues.

4.2. Improved Comfort

As previously described, the low noise performance of the 8LV350J is the biggest factor in improving comfort. By working together with the Research & Development Center, the optimum combination with the boat soundproof structure of the EX Series was performed for the engine to achieve a low noise performance not previously experienced in a diesel inboard engine.

The adoption of a new "internal propeller, internal rudder" propulsion system in the EX Series has improved ride comfort, with the boat also being highly regarded for its general comfort, leading to higher sales.

4.3. Enhanced Livability

Since the development of the Wide Series EX33A released in 2009, Yanmar has worked on the livability aspects of the design; in other words, factors such as cabin space, seat layout, berth space, a large toilet, and air conditioning. Although being the smallest model in the series makes livability design a challenge, the reaction of users at events such as test meetings has been extremely positive.

Yanmar started promotional activities in September 2014 and launched sales on December 1 of the same year. Deliveries to date total 15 boats, with the production schedule for 2015 already full with a planned 29 boats.

5. Conclusions

The development of the EX30B boat faced uniquely difficult issues in terms of using an electronically controlled engine and adopting a design that had hardly ever been used in the domestic market. To overcome these issues, an understanding of sales was required in the product planning stage, and working together with the sales department to achieve this was a major success.

The development of this product was a practical application of "Imagine and Do", the sixth item in Yanmar's Guiding Principles in its mission statement. In the future, we will continue to make our best efforts to develop hit products.

-IMPORTANT-

The original technical report is written in Japanese.

This document was translated by R&D Management Division.