Boat Functional Testing (Test Design)

There is always the risk of a test weakening something, leading to a failure during normal operation where it might otherwise have continued working had you not performed the test.

For example, the James Webb Space Telescope underwent severe vibration testing which subjected it to levels of vibration it is expected to experience during launch. There were anomalous readings that were subsequently traced to inadequate tie-downs on various parts of the mirror assembly. These have been corrected and now NASA is going to test it again, but what if it now won't survive the actual launch where it might otherwise have? It is a risk they have to take. Same with your boat. It's a tightrope act.

Just remember, whether it's a new boat and especially a used one... a boat is just a hole in the water where you put your money

if you haven't watched any "big fix alaska" I'd recommend it.

These guys really do the dirty work of getting and keeping things running.

It's not so much about a checklist as it is inspiration that when something goes wrong.. It can be fixed.

There do some work on boats like yours I'm sure.

Anybody who twists a wrench is likely to take something away from this show.

If you're still in dry dock, I'm assuming you are, then I wouldn't test anything until I get it in the water...Then I would run some tests, on everything....then start off with a few short runs, and back to the dock for checkup...

As staying on the hard is quite expensive, my boat went back to the water a couple of months ago, where i continued working on her.

So far I have made some runs and repaired (actually adjusted) parts that did not work properly just because the boat has been a long time on the dock causing seals to leak, etc.

I did some mayor repairs on the engines (open and closed) cooling systems: so far they did work great... but for how long should I operate engines to be positive the new exchangers are ok?

Well running it in open water for a couple of hours should reveal any immediate problems, but you need to be aware of maintenance procedures that need to be followed, as well as different water conditions that you can be expected to encounter....the water temperature changes, and sometimes you have seaweed and jellyfish and other organisms and debris that can interfere with the operation of your cooling systems, you should be aware of this and vigilant during operation....I would check with other owner operators in the area for any problems that they have encountered that may be location specific to your area....It's always a good idea to go out with experienced captains to observe their methodology and get tips on safe boating practices and preparation, as well as navigation, way point methods, known hazards in the area, filing requirements and communication protocols....

But first do all this with someone else's boat until you get the hang of it.

Thanks for your comments! I had something similar in mind, and therefore will certainly follow the procedure you sketched.

This may be of use.

I actually made a major repair over the last 3 years to my boat (an extended "half life" repair, so to say), including complete electrical rewiring, replacing mechanical for electronic morse controls, diesel tank cleaning, new engine filters (all) replacement of diesel injectors and pumps, new rudders, balancing of screws and shafts, water pumps, heat exchangers.... etc. after which I have sailed some hours on it having had no incident.... but that was not an actual sea trial.

When you say "full throttle" do you actually mean 100% power of both engines???? My question may sound stupid but these electronic morses have been set to an 80% of the max rev´s achieved by the engines: should I consider this figure as an 100% or have the RPM´s unblocked for the test?

Yes Doc,

FULL throttle. Sea trials are to discover faults BEFORE you put to sea working the vessel in its day-to-day mode.

To be able to ride-out, run before[outrun?] bad weather and heavy water requires the vessel to be able to perform at it's maximum for extended periods so as to save lives, as well as the ship.

Simple really.

Cheers,

Stu.

R&ddoc,

Stewey is (w) right. 100% throttle. You want to take off limits like thay for sea trials.

Of course, building up slowly to those maximums can shield you from potentially large time and money expenditures for repair. No need to start your testing at 100% right out of the gate.

Better to do all the necessary observations for excessive vibration and abnormal heat starting from low rpms and working slowly toward higher. If excessive vibration or excessive heat is noticed at some point, best to go remedy that before testing at higher rpm.

WOT as specified by rpms and duration in your manuals should not be exceeded. This is likely less than what you have said is 100% power. Engine failure, and prop cavitation can cause damage to both. Since you have a trawler, exceeding hull speed will be futile to performance.

What sort of weed you smokin' bro.

What do you understand is the term "hull speed"? What factors govern it?

If engine failure occurs the machine was not good enough from the start.

If propeller 'cavitation' occurs, there is a serious design fault in the vessel, and perhaps the choice of screw is suspect too.

Trawlers are routinely operated at 100% of their rated power. They haul nets and tackle up huge water as a given.

Hull speed on a displacement vessel is determined by the length at the water line. It is determined by 1.34 times the square of the LWL. Wikipedia has a good article on this. Once that speed is exceeded, excess power is required. Prop cavitation can cause small cracks and imperfections to become failures. I have seen this a few times.

Engine failure from over revving is not a design failure since you are exceeding design specs.

Hull speed is a model that gives a rough estimate, but it isn't really exact. It isn'r actually used that much today.

Check out the 200m K1 record sprint for kayaking... 33 point something something seconds. K1 specifies LWL close to 17 feet.

Hull speed for 17ft LWL is about 5.5 knots.

200 meters in 33.333 seconds is over 11 knots.

There is a lot more to a hull than simply LWL....and the idea that exceeding hull speed will cause cavitation leading to small cracks and failure is far too specific an application of something not remembered clearly enough.

I can't find anyone specifying over reving the engines.

I have to agree, hull designs have changed drastically with geometry as well as material to make it irrelevant.

A lot has to do with America losing the 'America's Cup' to the Aussies,.. what 25-30 years ago.

Keep an eye, mate, out to the bow, see where the Kraken lies in wait.

If your boat sails up on hydrofoils, then hull speed is less of a nuisance.

Here is what awaits all those who go down to the sea.

Let me digress a little here.

When I was going to college, in my Physical Metallurgy class, our professor who was not only Irish Scottish, but Loved to play the bag pipes, dress in a kilt (for events of course) and extremely loved had a passion for sailing.

Very knowledgeable fellow, in the course he was teaching and sailing. If in one of the lectures was getting a little boring, which was rare, we as students would work a sailing question or problem into the lecture which in turn changed direction of the lecture, and for the rest of the lecture we'd be talking about sailing... whether it be the composite design, the hull surface texture,... the hydrofoil design of the Aussies... it was quite interesting... really, both in what we learned, and especially the professors enthusiasm at his students interests.

Which actually served me quite well when I worked later in the ship yards. Such as Chine design/placement as one example for the naval SOC for the Seals.

Very cool. All I get to work on is old boilers.

It was cool,... I'm doing Oxidizers and stacks now... its hard to spin that...

Good answer.

Diesel engines can't over-rev, unless the governor is faulty or they are in such bad condition that they consume their own lube oil as fuel and "run away".

Rarely do they run away under load. Of course. As long as someone hasn't "adjusted"

the flight revs, in the governor, the thing can be firewalled without load and not blow.

NB 'firewalled' is and old industry familiarity which equates to 'pedal-to-the-metal' in an automotive sense.

Cheers,

Stu.

If this is a new build or if you have added any significant rigging, you may want to tilt test with the final rigging in place to determine metacentric height and stability curves. A good marine engineer should be able to help with this. The end result is you know what roll limits and loading conditions you can have to avoid capsizing.

This has been a half life repair. No significative changes have been performed to the rigging.

Good to know.

Do I understand correctly then that the vessel is a recreational vessel and not a fishing vessel? The hull is a conventional displacement design and is not a modified or wave piercing bow bulb?

A reset of the apples and oranges is needed here perhaps.

i would be interested to hear what avenue you take and the results. Thank you.

Sea trials can be very productive if you follow your vessel's operating manual and the engine manufacturer's instructions as far as rpms and duration. This is especially true for wide open throttle. Also check the manuals for expected speed through the water at specified rpms.

Checking for leaks, loose fasteners, hose and belt problems can yield obvious results at operating temps. IR imagery can be useful if you know the equipment and what to look for.

The best investment however is to engage a good marine surveyor (NAMS or SAMS) who may also have an engine specialist look at the vessel. Ballpark $40/ft depending on location.

Did you re-christen the boat? If not, I suggest Boaty-McBoatface No.2

It can't be No.1 or without the number because the USN already has a ship named that.

If she were mine (and I am a total land-lubber), I would run her out at 100% (override the Morses.) at least 1/2 hour, maybe until you reach peak operating temperature if that is still a safe running temperature.

What would you do when running in a storm? You better have a finite plan already written, but better write that in your mind, since you won't have time to read.

Hi to all, and thanks for the valuable inputs!

I have been quite busy for some time, which prevented me from updating this post.

Some weeks ago I performed several test runs at different RPM´s with a mechanic on board, noticing that one of the engines started heating up after 15 min at full throttle, while the other one stayed within temp range.

The cause for this happened to be a defective water pump, which was replaced. As the coolant of both engines was "dirty" with iron oxide, we also drained both engines, and flushed them using a good quality cooling system cleaner.

We tested engines one more time, and everything runned smooth.

So far we already spent a couple of weekends with the family on board, having had no problems at all.

Have you familiarized the family with drills for various emergencies: fire, flooding, pirates, man over-board, collision?

Better to be familiar and never need it than....

Good question! Yes I have been working on that for a long time. Still do not feel confident on my wife´s skills to get me out of the water should I fall over board .... but well, we are still trying....