Inclining Experiment....

[Sunny.K]

Can someone help me with this inclining Experiment??

If I'm to conduct an incline experiment on a double hull boat of like 39meters and a displacement of like 445tonnes but there was new renovations to the boat.....

I need to know where I could find informations on how to perform the experiment or someone can help me. I understand using pendulum and weights but how and where should I have to drop it from is what i need (whether bridge deck, main deck etc) and what actually should I do?? please if someone can help it would be much appreciated??

Regards,
Sunny

[Guillermo]

Read Annex A in this document:
http://www.nmsc.gov.au/documents/NSCV/PART6C.pdf
(Well, as a matter of fact, read all the document)

Cheers.

[Ad Hoc]

It worries me that if you are performing an inclining expt yet do not seem to know the basics. Are you a qualified naval architect?

[Sunny.K]

This experiment is gonna be done by a Naval Architect...this is for my own learning purposes!! so when the experiment is done I would already have a clue....I wanna learn every operations that is happening in this shipping company in PNG....like I said before I am engineering graduate of other discipline but wants to shift into marine and naval so I could study it and continue on to uni with it........

[Ad Hoc]

If another Naval Architect is doing it and are you with him? why not ask the naval architect....this is the most obvious route!

Not being picky here, but if you have "one to hand"...it is the most logical person to ask...and they can explain to you in real time not bitty by email

[Sunny.K]

true...

[Sunny.K]

but it is always good to have your own info and researches!!!

[Ad Hoc]

Guillermo gave you that already....

[Ike]

if you simply google inclining experiment you will find lots of references

[Sunny.K]

what if I can't be bother reading alot of ********...to get the right thing you need the place!!!:D:D

[Joakim]

Read Annex A in this document:
http://www.nmsc.gov.au/documents/NSCV/PART6C.pdf
(Well, as a matter of fact, read all the document)


How typical is it to use a digital inclinometer? What is the reason for not allowing it to be the only tool used? With current technology and some care a digital inclinometer can be at least as accurate as a pendulum and is not affected by wind and the skill of the person reading the pendulum.

I have designed and made some digital inclinometers, which have an accuracy of 0.5% (of angle difference) +- 0.01 degrees and a resolution of 0.001 degrees.

Joakim

[Guillermo]

Digital clinometers are only good if the vessel doesn't roll at all when at the inclining experiment, unless they have means to promediate readings, as it is very difficult to do that by 'eye'.

Most inclining experiments are performed in waters that are not perfectly flat (sea is not a pool) and so the vessels always move slightly, making the digital clinometer to show constantly varying measurements difficult to 'catch' if they are not provided with the adequate software. Those are easier to estimate when using pendulums, although some practice is required.

I use one or two pendulums, depending on the length of the vessels, promediating 10 pairs of deviations for each weight movement. If conditions are good enough, I also use a digital clinometer only to cross-check results after we calculate the angles from the pendulums readings.

Pendulums are great if conditions are not perfect (which happens most of the times). They are also cheap...:)

Cheers.

[Ad Hoc]

Using the digital inclinometer is also bit of an over kill. Considering everything else is "rough". For example, how accurately can you read the draught marks??..look at the systematic percentage errors of this whole procedure and you'll see the displacement can vary considerably.

The more accurate you try, the less accurate the answer. A series of good rough estimates are far better than one single attempt at an accurate answer. I would never believe an answer of 0.001 degree too

[Guillermo]

Totally agree.
For very small commercial fishing boats, where it is imposssible to mount a pendulum, we use a simple air bubble clinometer, with precision of only 0.5 deg. That's enough precision when you're measuring 14º tilts, as the 1964 spanish norm asks for (not to reach that angle, nor submerge the sheerline, using some heavy test weights).

Cheers.

[Joakim]

Digital clinometers are only good if the vessel doesn't roll at all when at the inclining experiment, unless they have means to promediate readings, as it is very difficult to do that by 'eye'.

Most inclining experiments are performed in waters that are not perfectly flat (sea is not a pool) and so the vessels always move slightly, making the digital clinometer to show constantly varying measurements difficult to 'catch' if they are not provided with the adequate software. Those are easier to estimate when using pendulums, although some practice is required.

I use one or two pendulums, depending on the length of the vessels, promediating 10 pairs of deviations for each weight movement. If conditions are good enough, I also use a digital clinometer only to cross-check results after we calculate the angles from the pendulums readings.

Pendulums are great if conditions are not perfect (which happens most of the times). They are also cheap...:)

Cheers.

Yes, of course an appropriate software is required. My inclinometer records the angle 10 times in a second for one minute (600 samples), draws a curve, calculates an average and error estimates for the average for each of the 9 measurements for the standard test.

I actually think just the opposite. A digital inclinometer is better when the conditions are not perfect. I have done some comparisons of an experienced pendulum user vs. my inclinometer. In perfect conditions the results are just the same, but in rough ones a much better linearity was achieved with the inclinometer.

Pendulums are cheap, but requires more space and work, especially when you are required to have several of them. Which digital inclinometer are you using? How much did it cost?

Ad Hoc:

As I said, the accuracy is not 0,001, which is the resolution. Thus you can distinguish an angle difference of a 0,001 (e.g. putting a single A4 sheet under one end of a 5 m bar), but neither of the angles are 0,001 accurate.

For the actual on water measurement in good conditions you will get repeated measurements to +-0.01 degrees from each other. The conditions need to VERY bad in order not to achieve +-0,1 degrees. That would need rolling of several degrees and actually wind is much worse than waves, since wind can cause a shift in the average, especially for sailboats.

Joakim

[Ike]

To dampen roll is simple. We hung the weight on the end of the pendulum in a tray of oil. Any sudden motions were dampened and any free surface effect became obvious because the pendulum would start to move. Also the longer the pendulum the more accurate the reading. We didnt read angle. We calculated angle. by knowing the length of the pendulum and how far offset it is from zero you can calculate the degrees. Simple trigonometry.

When I said google it, I wasn't being sarcastic. There are many good sources on the internet. You have to decide if they are a waste of your time, not us.

[Guillermo]

Yes, of course an appropriate software is required. My inclinometer records the angle 10 times in a second for one minute (600 samples), draws a curve, calculates an average and error estimates for the average for each of the 9 measurements for the standard test.
I'd like to have a look at your clinometer, Joakim Majander. Is it available commercially? ORC?

Cheers.

[Ad Hoc]

I always use a pendulum with 4 vanes, and then locate the oldest dirtiest motor/engine oil i can find.

[Joakim]

I'd like to have a look at your clinometer, Joakim Majander. Is it available commercially? ORC?

Cheers.

I'm sorry, this was not intended to be an advertisement, but here we go.

Yes, I have sold some of them to be used for ORC measurents or for commercial use. Started as an electronics hobby, but I had to start a very small part time company in order to be able sell to companies.

Here is a short description of the ORC model: http://kotisivut.fonet.fi/~jmajande/JM_Sensors_ORC.pdf

There is another software version better suited for the standard 8 weight shift measurement. Also there is another model with a shorter and thinner cable (5 m) without the small plastic box. The current version of the software no longer works on W98.

You can download a demo version of the software including manuals from here: http://kotisivut.fonet.fi/~jmajande/RM_demo_current.zip

Just unzip somewhere and start JM-Sensors/lib/SHIPRM_d.exe. No installation is necessary. Included are two (one for SHIPRM and one for IMSRM) real measurements, which you can view.

Ad Hoc: Using old engine oil sounds disgusting to me! What you can see with a non-damped (10 Hz response) instrument drawing a curve is that you can easily find local plateaus that look good, but are not at the average. I think these are caused by the wind. So you should not consider a stable value for e.g. 10 seconds to always be an accurate one.

Joakim

[Ad Hoc]

Jaokom
Old engine oil is the best to use, it is very thick and 'sticky' as the guys would say to me...and with a vaned plumb bob, it is perfect. When i was based in one yard i used the same oil and bath for many years.

These basics become even more important later on, since many inclining expts i have done in recent years have been in remote parts of the world and not in ideal conditions.

[Joakim]

Jaokom
Old engine oil is the best to use, it is very thick and 'sticky' as the guys would say to me...and with a vaned plumb bob, it is perfect.

Certainly there are many less poisonous, smelly and staining fluids with similar dampening properties (density and viscosity).

How do you use that, when you travel? For a long pendulum you need quite a big amount of fluid.

Joakim

[Ad Hoc]

Joakim
"...Certainly there are many less poisonous, smelly and staining fluids with similar dampening properties (density and viscosity)..."
How many do you know that are readily available in remote shipyards, where even a replacement nut takes a day or 2, or a very along self drive to a big city and back?

For yards I travel to, I get the yard to make a nice wide tank for me...it is easy. If they can fabricate a boat, they can sure make a simple oil bath!

[Joakim]

For yards I travel to, I get the yard to make a nice wide tank for me...it is easy. If they can fabricate a boat, they can sure make a simple oil bath!

There's the difference. The measurements I have been involved with have been done in places where there is no used oil available unless it comes with the boat and the measurer has driven there with a car bringing all he needs with him.

You still need to clean and/or smell/get stained by your plumb bob or is that also from the yard.

Joakim

[Ad Hoc]

Joakim
A shipyard, with no used oil anywhere....well, that's a first!

I have my own 4 vaned plum-bob which is easy to pack into a suitcase. I just need an oil bath that's it.

[Joakim]

Joakim
A shipyard, with no used oil anywhere....well, that's a first!

Not a shipyard. A small harbour or other place suitable for a measurement. Not where the boats are made typically here.

Joakim

[Guillermo]

Very interesting Joakim, thanks.
Results are the 8 measured angles, but the program doesn't seem to plot the inclining mass moments vs angles graph, does it? (See page 57 in http://www.nmsc.gov.au/documents/NSCV/PART6C.pdf)

We need that for quickly checking for problems during the inclining experiment.That would be a nice and important feature. Also the final calculation of the medium Pt-Stb value for the angle to be used at the stability calculations.

I'll PM you from the office.

Cheers.

[Joakim]

Very interesting Joakim, thanks.
Results are the 8 measured angles, but the program doesn't seem to plot the inclining mass moments vs angles graph, does it? (See page 57 in http://www.nmsc.gov.au/documents/NSCV/PART6C.pdf)

We need that for quickly checking for problems during the inclining experiment.That would be a nice and important feature. Also the final calculation of the medium Pt-Stb value for the angle to be used at the stability calculations.


Yes I know, but the users so far have not been asking for that and at least some of them are using non-standard methods (e.g. using ships own fuel or water tanks as weights), which makes it much more complicated to program and use. All of them already had Excel or some other methods, which needed just the angles.

Many commercial users use the ORC method, which transfers just one weight from one side to the other. For that the ORC version (IMSRM.exe) calculates RM and its error estimate.

Joakim

[Ike]

We sure as h... didn't use engine oil. I would have like to have seen that stuff in my engine though. It was really clean.

[ancient kayaker]

Home-made damped inclinometer: you will need a half-full jar of syrup, a school protractor, and a magnifying glass. The rest is kind of obvious ...

[Guillermo]

Interesting:
Google images around for "home made clinometer" and "tilt gauge clinometer"

Cheers.

[bremerjohn]

Certainly there are many less poisonous, smelly and staining fluids with similar dampening properties (density and viscosity).

How do you use that, when you travel? For a long pendulum you need quite a big amount of fluid.

Joakim

I've had good luck with laundry soap as a pendulum dampening fluid. A bit more friendly to the environment should it spill on an open deck, which is good if the test is being witnessed by a regulatory agency.

We also use small buckets for each pendulum, and simply move the bucket with each weight move, thus less fluid required. We use three pendulums per the US ASTM standard and average the readings.

The US Coast Guard will allow one of the three pendulums to be replaced with an inclinometer. But they still require the other two to be pendulums, for some of the reasons already described herein. Also, what happens if the battery dies in your inclinometer half-way through the test? The greatest advantage of pendulums is that they are simple.

John

[Ad Hoc]

bremerjohn

Laundry fluid...wow, never thought of that. I'll try it next time...assuming Class will allow it!...(don't see why they shouldn't).

[bremerjohn]

The only thing to be careful of is if you're doing it in winter and the temperature gets real low, the laundry soap can start to get a bit too heavy. Usually not a problem for me here in the Pacific Northwest with relatively mild temps, but I've had trouble in Alaska before.

[Ad Hoc]

b.john

i've been lucky enough to do my last few inc.expts in the tropics, so no problem there. mind you previous ones up in the north of scotland, in winter, noted!!

[bremerjohn]

Nothing like a fine day out of the office on a boat out in the sun - and getting paid for it!

Maybe we should start a new thread about things that happened during a past incline test. Might help to learn from the mistakes of others.

I think I'll do that.

John

[Ad Hoc]

b.john

that would be interesting to read!....one of the strangest 'things' to occur to me was about 15 years ago. Doing an inc.expt on a 40m cat, the surveyor didn't check or bother to witness anything I did, just left me to get on with it....why?..because he was just transferred from big ULCC type vessel to small craft. He didn't have a clue, or so he said.....an inc.expt is an inc.expt, whether 10m run about or 300m tanker.....one of the most incompetent surveyors I've ever come across...he shouldn't have been allowed to be a surveyor!

But getting down to my boxers and diving into to look under the hull, in the tropics, despite being odd, was wonderful, crystal clear lukewarm sea water...bliss!

[bremerjohn]

That's not an uncommon occurrence. In the states it depends somewhat on what type of vessel it is as to who will witness the test. If it is a passenger vessel for instance, then the Coast Guard will witness the test. They tend to cycle their marine safety inspectors through on a regular basis, which means you frequently get somebody who has done few if any tests before. If ABS is witnessing the test, however, they generally have people with pretty good experience, and most I've worked with will pitch in and help out during the test. Good folks.

I had a yacht customer once in Newport Beach, California with a modified Hatteras. I had to confirm the dimensions of the transom, and had no choice but to jump in the water to do it. He was shocked, but so impressed that a technical person he hired would jump in the water that he invited me out on the boat that summer.

[MikeJohns]

..Maybe we should start a new thread about things that happened during a past incline test. Might help to learn from the mistakes of others....

I always lose things from my shirt pockets leaning over the side...those essential bits of paper and your last good biro.

I use a chromed brass bubble clinometer that was made in 1908 by "T Cook and Sons" and has been in service ever since , after I broke the bubble vial the instrument repairer gave us a morel viscous fluid in the vial its much better than before (and unbreakable).

Pendulums damp better in water if the weight has some fins on it, i've even seen a sponge attached.

Ultrasonic distance gauges are usefull too for soundings.

[Guillermo]

....and simply move the bucket with each weight move....
How do you do that? How do you keep the reference to the zero position? :confused:

I would like to try the laundry fluid thing. Interesting. :)

Cheers.

[Guillermo]

Mike, I use bubble clinometers only for very small commercial fishing and recreational boats, as usually there is no way of hanging a long enough pendulum and also because for such boats the stability criteria we have requires the measurement of relatively big heeling angles with no high accuracy.

What are the type of boats do you use the clinometer for?

Cheers.

[MikeJohns]

I always used the clinometer along with the pendulums as a quick cross check at one station. Also for anything small or open where a plumb bob is impractical.

You can move a bucket around for damping fluid, but you have a separate scribe board for the measurement with your zero marked on it otherwise its a lot of water in a trough. I see you have our guidelines anyway :-)

cheers

[bremerjohn]

How do you do that? How do you keep the reference to the zero position? :

Cheers.

MikeJohns answered correctly. You have a sawhorse or other fixed board above your bucket, wide enough to handle the pendulum swing. Then the bucket only needs to be big enough to dampen the motions, and can be slid back and forth with each move. Marks are made on the board above it.

Our 3 pendulums are small, cross shaped steel ones we had custom made. I've never heard of the sponge technique. Interesting!

We've used recently one of those laser measuring devices when doing weights moves. We picked one up at the local hardware store for about $65. Comes in handy for other tasks like measuring fish holds etc.

We also use that write-in-the-rain paper for test notes, just in case they fall overboard.

John

[Joakim]

Also, what happens if the battery dies in your inclinometer half-way through the test? The greatest advantage of pendulums is that they are simple.


It is powered from the USB-cable. Of course your laptop could run out of batteries, if you don't have a power supply for it.

Joakim

[Guillermo]

...have a sawhorse or other fixed board above your bucket..
I see. But anyhow you need to carry some device to fix the board over the bucket. I designed and built an aluminium bucket with the board fixed on it, to be filled with seawater. If I remember to take a picture from it, I'll post it here.

I've found the laser measuring device very useful. If combined with a digital clinometer on a tripod it may also be used to measure hulls (sections). You get coordinates in polars and then load them into an spreadsheet to be changed to cartesian coordinates. I build one such a device and it works quite well, being inexpensive if compared with the 'cloud of points' machines.

Cheers.

[JV16]

Joakim,

For those boats that require the stability book to be approved by class society / flag, you would need your instrument to be approved by them. If you get it approved, it would be a very good start. BTB, how much does your inclinometer cost?
cheers

[Joakim]

My Inclinometer including software costs 1000 euros + delivery + local taxes/customs (see post #19).

I haven't yet checked other countries, but here in Finland no approval of the inclinometer is required. It is the responsibility of the measurer to use adequate tools. Here inclinometers can replace 2 out of 3 pendulums for the official measurements.

Can you tell me more details about the approval procedure in different countries?

Joakim

[Ad Hoc]

Joakim

As JV16 noted, if you are doing an inc.expt to Class/Flag all equipment must be calibrated and certified.

Are you performing inc.expt's which are not to Class?

€1000...wooahhh..makes a bucket of oil and string seem cheap...oh wait, it is!

[JV16]

Hi Joakim,
Price noted. I'm from Singapore and I used to work as a surveyor. Rather than approaching flag states, I think it will be easier if you approach class socities for type approval. You can approach one of them, get the approval and then try to get the approval from the others. Here only pendulums and U tubes are permitted for inclining tests.

Good luck