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Bulbous Bow Addition to 93 Aft House Inace Yachts Under Construction

Bulbous Bow Installation

93 Aft House Inace Yachts Under Construction

I have recently returned from a visit to INACE YACHTS SHIPYARD to inspect the 93' aft house with her owners. Among the numerous things going on that I thought people would find of interest, is the fitting of the bulbous bow to the boat. A few things to take note of, the hull structure was fully finished and the bulb is being fitted as a separate element. What this means is if the bulb should impact something and the watertight integrity be compromised it will not have any effect on the water tight integrity of the hull.

Also of interest is the basic design and structure of the bulb. Please note that the bulb is not just a simple round cylinder, it has a fine top and bottom entry. It is very easy to understand why the bulb would be designed with a sharp entry on the bottom in order to reduce slamming. What I found very interesting is that from a number of studies done, slamming not only occurs from the pounding of the bottom of the bulb back into a sea but from the seas dropping back on top of the bulb. The sharp entry on the top helps to cleave the sea as it drops back and reduce drumming. There are a number of large yachts operating today with a more sophisticated looking bulb, sort of a banana shape that has shown very good resistance, however their flatter bottoms and tops appear to cause drumming and vibration transfer at a higher rate then their less styled brothers.

Click Image at Left for Larger

I must caution that this has not been proven conclusively in tank testing but has been noted in real life application. The problem with real life application is it is subject to different interpretation. However, it does seem to indicate another area were the KISS principal of yacht construction may apply.

The other point to note on the bulb being fitted to the 93' AHD is the massive structure. The structure is not just to hold the bulb to the boat, but is designed so it can take substantial impact without failing. Purely from a visual stand point I would have to say between a partly sunken container and the bulb, I would put my money on the bulb. As this 93' is being built to ABS the bulb also meets their requirements. She will have a fill and drain point and once the vessel is floated it will be determined if she will need any liquid ballast. The bulb is designed to have neutral buoyancy and have a small amount of fish/vegetable oil inside.

Over all progress on the 93 AHD is coming very well, she was inspected by a independent Surveyor for PATTON MARINE in addition to the ABS inspectors. The PATTON Surveyor was quite please not only with the 93 but with the over all quality of the all of the vessels under construction at the yard.

Please feel free to contact me with any questions of comments on the above. Contact me for more information to build your own Inace Yacht.