Skeg Induced Vibration
20m boat vibrated after repower, with increased speed - speed, vibration frequency, and vessel characteristics - dictated problem was from skeg vibration at hull frequency - fix was simple modification of skeg trailing edge.

Stabilizer Fin Induced Vibration
50m boat had major vibration particularly when turning at cruise speed. After expensive shaft and propeller checks and changes, J&A conducted diagnostic tests and traced the issue to shedding from stabilizer fin fit-up to hull. Inexpensive fairing blocks at the fin root eliminated the problem.

Carbon Shaft Issue
A new workboat having carbon shaft drive lines was experiencing high vibration and shaft seal rubbing. J&A conducted laser, non-contact, shaft motion studies and shaft dynamic calculations to verify the problem, and evaluated practical fixes, which were implemented by the shaft designer/supplier. Problem fixed.

Shaft/bearing Induced Vibration
Hull vibration and noise in a 70m yacht in cabins close to shaft seal. J&A test and calculation showed cause to be interaction of torsional shaft mode and seal/thrust bearing interaction. Fix using steel and structural adhesives fixed the problem without requiring hot work and realignment.

Quiet Refit
20m research vessel was built with little regard to noise control and was noisy. J&A sea trials identified a series of improvements, including machinery mounting and insulation improvements. The corrections were made in a yard period, and results to 10 dB(A) noise reduction were achieved.

Modification of New-build Production Boat
Owner of a new 38’ sport fish yacht wanted improved quieting compared to stock models. J&A trials on a stock boat identified practical improvements for his new construction. Fixes for exhaust, propeller, and insulation resulted in significant noise reduction, and a happy owner.

Simple Solution
80’ sport fisher had a major new noise after a yard period. Gearbox and shaft bearings were suspected. J&A examination determined that the renewed propeller coating was the cause, and correction was achieved by grinding the coating an the trailing edges. Problem solved.

Before and After
J&A performs before and after haul out noise and vibration trials which provide protections for both shipyards and vessel owners for evaluation of improvements and surprise “it didn’t used to do that” situations. Our work quality is recognized by A.B.S.