Different type of test

[depthofit]

Hi, i am a marine student in Singapore doing my final year project. My team and i are going to build a catamaran model out of balsa wood and coat it with fibreglass cloth and epoxy. Other than a towing test, what other type of test can i conduct to investigate stability and comfort of the passenger and how exactly am i going to execute them. It is a 2-man recreational catamaran, 60cm length and about 25cm beam.

Another thing on my mind is that what do you guys thing about our project, is the theme and result worth the time?

We have decided to propose a hull design and its propulsion system. So we proceed with designing and building a model for testing. At the end of the day, we should be able to assess our hull base on the tests that we have conducted, what type of engine, how much power, how stable it is exactly, how long can it run things like that. ( The idea of the project was came up by us and not the lecturers) So i guess the more tests we conduct, the more detailed and broad our final presentation will be. Please feel free to give me some opinions.

[Marvic]

I think its a good idea. If you have the time and facilities go for it.

Some of the problems today is that students rely to heavily on results from software programs without knowing if the results are correct. This way you can compare your test results with results from a software package.

I would recommend reading annex 7 of IMO 2000 HSC code

[TeddyDiver]

Originally Posted by depthofit

]what other type of test can i conduct to investigate stability and comfort of the passenger and how exactly am i going to execute them

Accelerations affecting passanger in different parts of the vessel in varying circumstances?

[Marvic]

These papers may be of interest to you..

[rwatson]

Great articles Marvic.

I note that the vertical accelleration of the human body is cited as the biggest "sickmaking" feature.

For a catamaran, may I also mention (based on experience) that the Yaw factor can be pronounced. On a wave piercing cat, the steering was done with the port and starboard waterjets being increased. Normal (autopilot) steering induced a pronounced yaw, combined with a dip in the hull being accellerated, that was extremely uncomfortable. They would have been better off to employ a conventional rudder for near straight line directional control - it would have made the journey much more comfortable.

After the initial trials, a marketing survey was conducted - and due to the unpopularity of the catamaran travel, they bought conventional passenger ferries.

That was a great quote in those papers from Anacharsis "People may be divided into three classes, the living, the dead and the seasick"

[depthofit]

Hey thats something very interesting and something i did not know at all because i haven been on a catamaran before, how ironic isnt it. I will definitely look into it. Thnks anyway. I most probably will have more question after reading, so please stay around to help me out. Thnks alot!

[Ad Hoc]

If the test tank allows, perform some standard RAOs. Use values from other papers, as a source, so you can then relate your own design directly with another. Just the general Heave, Pitch and Roll would suffice. You can then of course over lay such data onto the standrad ISO seasickness curve.

Wave Piercing cats tend to "cork screw". Their slender hulls up forward do not have the reserve of buoyancy (that's the point of them) in large sea's. Trouble is this creates 'odd' motions, she cork screws. The rudder thing is applicable to all vessel with waterjets, mono,cat etc. The reaction time of the jets and the vector thrust creates a slight turning to port or stbd. The constant 'wiggling' slows the vessel down. Small rudders are the answer. I have designed 2 HSC vessels with such small rudders which are 'programmed' for minor rates of turn with excellent result.

[Alan_VA]

Originally Posted by rwatson

I note that the vertical acceleration of the human body is cited as the biggest "sickmaking" feature.

Motion sickness (see IMO acceleration v. frequency charts) is the first thing people think of when they consider boat/ship motion, and I do not wish to understate the effect it can have on enjoyment of the transit or on the performance of watchkeepers. I would also add, though, that there is also a relationship between vertical and horizontal accelerations and the subsequent ability of the crew to simply stand upright and perform mechanical tasks. The combination of those accelerations can result in tripping, dropping objects, and other hazards.

Good luck with the project.

[Ad Hoc]

Motion sickness is very interesting topic and many papers on the subject.
However, motion sickness is a generic term for the discomfort and associated emesis (vomiting) induced by a variety of motion conditions: on ships, in aircraft, or in vehicles, on a swing or amusement park ride, in zero gravity environments (space), and even in elevators. Actually, the term “motion sickness” is somewhat of a misnomer from two perspectives. First, it can
be induced in the absence ofmotion as during a virtual reality simulation, and secondly, sickness implies that it is a type of disease, when in fact it is a perfectly normal response of a healthy individual without any functional disorders.
Read the excellent paper by S.Stevens and M.Parsons "Effects of Motion at Sea on Crew Performance: A Survey". It should be the bible on the subject.

[Manie B]

Marvic

thanks very good reading

[Guillermo]

Marvic
I found particulalrly interesting the paper on 'habitability on personal space in seakeeping behaviour'. I didn't know it. Thanks for posting.

Here another interesting link:
http://www.nps.navy.mil/orfacpag/res...dexed/1a_3.pdf

Cheers.

[Marvic]

Hi Guys,

I thought you may be interested in this manual as well.

Marvic