Wednesday, December 29, 2010

Romjulen ruller videre

Veien til fullendt bedring er lengre og tyngre enn jeg først fikk inntrykk av. Jeg var forberedt på dette, siden bedringen etter en smell alltid går fortest i begynnelsen. Jeg hadde allikevel på mitt optimistiske vis innbilt meg at jeg skulle være tilbake på beina før nyttår, men nå ser jeg at det ikke blir slik.

Ellen og Lisette dro ut sammen i dag og tok en titt. Situasjonen i Oscilia er fortsatt stabil, og det virker som om det gjennomgående holder seg over frysepunktet under dørken. I Nemi har vannstanden holdt seg noenlunde jevn siden jeg dro, men etter at mildværet nå har meldt sin ankomst, har vannet steget en tomme. Jeg får vel i det minste ta en titt til før nyttårsaften, dersom det ikke fryser grundig på igjen.

Livet på land er som vanlig særs behagelig. Jeg har nå sittet og sett et par episoder av The Real Heroes of Telemark, mens Ellen har jobbet med et maleri av Nemi. Jeg tvilte et øyeblikk da hun tilbød seg å gjøre det. Har du noensinne måttet skyte bikkja di fordi du simpelt hen har vært ute av stand til å ta vare på den? Har du i tillegg lagt en plan for å gjøre det selv? Og ville du så ønsket deg et maleri på veggen for å minne deg på historien for all og evig framtid?

Etter å ha vurdert det en stund, har jeg kommet fram til at jeg ikke kan gjemme meg for konsekvensene av mine valg, spesielt ikke etter at prisen er betalt. Det hadde vært å redusere verdien på læringsopplevelsen, og det er jo tross alt det eneste jeg sitter igjen med.

Nå er det middag, på beste sorts juleskinke. Jeg skriver igjen når det dukker opp noe mer båtstoff, men det har det jo vært tynt med i det siste.

Tuesday, December 28, 2010

Here are some pics from our time on Oscilia up untill now.
Just a little something to watch while we are waiting for Henning to be operative again!



Nimo in the mast


Nimo is anxiuos to get on land and is sniffing in the air




Captain and me, the wife :)



Henning is trying a new water sport.




Nice and new paint after a week of work.





Working guys.



Fireguard.




Our man on welding. A real quelt.
Pretty boat, ay?




Nice afternoons on deck, with food on the
barbeque, a good book in hand and a nice
little companion.
We barbequed on the afterdeck a lot this summer
From a trip to Bile.
And here is our captain, we are waiting for you, get well!

























Saturday, December 25, 2010

How bad can it really be?

There's a question which has been asked a countless number of times, in many variations. Someone may ask "I'm looking to buy Boat X, but I don't feel ready for such a big boat without a thruster. How much do I need to budget to get one installed?" Someone else might say "I'm trying to choose between boats X and Y. Boat X is superior in almost every respect, but I really like that Boat Y has two engines, especially with regards to maneuverability. What's your advice?" I know this situation very well, because it appeared to me when I bought Nemi a few years ago. I asked the question in it's purest form: "How bad can it really be to maneuver a large single-shaft boat with no thrusters anywhere?"

As I soon discovered, there are as many ways of answering this question as there are of asking it, and the answers I got varied wildly. The most optimistic (people selling such boats) told me I wouldn't feel a thing, while the most pessimistic (people proud of ther new, huge 30-footer) told me in no uncertain terms that such activities were best left to grizzled old men with a lifetime of experience. In the end I listened to the poorly repressed optimist in my heart, and went for it. It has been an immensely valuable learning experience, maybe even enough so to justify the rather sad story Nemi has turned into.

You probably know most of the clichés by now, especially if you found this through Google. They're slow to react. They punish you severly for small mistakes. You must learn to think ahead. Yada yada. I'll cut all of that crap, and instead concentrate on the stuff I found out after I actually started using Nemi, which is hopefully the same stuff you haven't aready been told.

The first thing I learned is something I might have known on a subconscious level for years, but never thought enough about: When maneuvering at close quarters, it is more important to know what the boat cannot do, than what it can. If you figure that out, you can steer clear of any situation requiring an impossible maneuver to resolve. However, while this may be a simple concept, the details of the matter are rather complex. Most boaters of any experience will know that getting into a corner is a bad thing, but there is more to it than that. Initially I was highly skeptical about the boat's capacity to turn in confined spaces, and left myself a huge margin in every situation.

Having undertaken some maneuverability trials in open waters and learning more techniques for warping her around when there simply wasn't space to turn, I gradually gained the confidence to get into tighter spots. My experience with smaller single shafters was certainly a help, but there is a lot you won't learn if you don't have to. In other words, if it is at all possible to man-handle your craft when you need to, you will tend to allow the potential for such a need to develop. With Nemi weighing in at 35 metric tons, I didn't need telling that I must avoid those situations. Thus, there are a few widely discussed traits of such boats that I knew about on an intellectual level, but for which I had absolutely no feel.

Three of those traits come together to form an importan handling aspect: First, you must consider the direction of pull from your propeller. If it turns clockwise while under way, it will pull the stern to port when in reverse. Second, while the inertia of linear movement may seem disconcerting at first, it can be a great help in making tight turns. If you set the boat moving astern at half a knot, you can add quite a bit of power ahead before the movement reverses itself, and this helps inducing rotation. Third, the rotational inertia of a large boat can be considerable. This means that if you start a turn and let the boat sit dead in the water, it will keep turning for a while before it stops.

With the aid of the above, and considering that Nemi had a clockwise propeller and very little keel, I developed the following technique: Set the rudder 35 degrees to starboard, then alternate between forward and reverse at 30-50% rpm, so that the boat picks up 0.5-1 knot in either direction. Thus it is possible to make a full 360 degree turn inside a ~25m circle (roughly 1.5 times the boat length).

Having learned this, and having maneuvered alongside the dock on a spring a few times, I no longer felt intimidated by her, and this is when the joy of driving such a sluggish beast started sinking in. In Nemi, I can go alongside in a stiff offshore breeze, then peel and eat a banana before she starts moving away from the quay. Swell from passing boats no longer threatens to lift me onto the dock. And perhaps most importantly, as a friend of mine put it: "Wow, I just can't help getting a hard-on from controlling something this big!"



Nemi under way, with me on deck and the wife driving:

Friday, December 24, 2010

Julestemning

Roen har senket seg, og stemningen har begynt å falle på plass. Mamma har gitt meg en seng på loftet og en tynn sommerdyne. Etter snart å ha sovet i hus i en uke, er kroppen delvis aklimatisert, og jeg sliter ikke lenger med varmen. Jeg kunne blitt vant til dette.


Jeg skrev en liten artikkel om reparasjon av propellskader i Juni, men den ble aldri publisert, siden jeg ikke fant noen bilder av den ferdige jobben. Etter i dag å ha konstatert at de bildene ikke finnes på laptopen min, bestemte jeg meg for å publisere allikevel, så får jeg heller oppdatere med noen flere bilder etter at Oscilia går på slipp til sommeren.


Ellen har vært kjempesnill og sett til båtene mens jeg har ligget invalid. Hun dro ut igjen i dag, og det virker som om situasjonen er relativt stabil, på tross av et par ting som bekymrer meg. Det var en liten perle med is på innsiden av eksosgjennomføringen på styrbord side, og jeg tør ikke å avskrive muligheten for at det er resultatet av en frostskade i kanalen på utsiden. Den ligger slik til at den ikke kommer til å tine på en stund, så jeg trenger ikke å ligge våken og uroe meg, men nå må jeg være på ballen hvis mildværet kommer.


En annen, større bekymring er at kjølsvinet i Nemi nå er gjennomfrosset. Jeg vet alt for godt hvordan det pleier å gå når skiten tiner, så her har jeg fått servert et noe udefinert tidspress på rivningsjobben. Jeg har jo ingen store verdier lagret ombord, men de langsiktige konsekvensene hvis situasjonen skulle utvikle seg i feil retning er strengt prohibitive. Her må det taes tak!


Ellen tok noen bilder av båtene fra land, og det ser så hjemmekoselig ut! Tro det eller ei, jeg gleder meg til å kunne flytte tilbake. Bedringen i hofta går med stormskritt, og jeg sov natt til i dag helt uten å våkne av at jeg snudde meg. Hvis ting fortsetter i dette tempoet, er det ikke lenge til jeg er helt oppegående. Kanskje jeg til og med kan gjøre alvor av planen om å ta en natt eller to der ute i løpet av romjulen, selv om jeg må kline på plass Refleksen for at det skal bli levelig.

Freehanding the propeller with a grinder: Excellent!

Okay, I'll be the first one to admit that the title of this post is misleading, if not outright erronous. Propeller blade geometry is an extremely complex area of expertise, and only a select few have the talent and experience to fully understand all of the aspects. I remember this clearly from my time wrenching Formula 2 boats. There are only a very few people in the country considered to have the necessary skill to carry out good repair, and even fewer who can carry out a meaningful adjustment. The pit area was teeming with stories about some failed adjustment that could never be corrected, carried out by the most skilled technicians in the business, which completely destroyed the properties of a match winning propeller. With that in mind, a layman like myself shouldn't even attempt to repair obvious damage, but leave this to an expert, lest I cause more harm than I remedy. However, this principle depends slightly on how bad the starting point is. If, for example, you are looking at a propeller with one blade broken clean off, chances are that you won't make matters worse by welding it back on, regardless of the accuracy of the operation. Of course, there is no guarantee that the end result will be good, or even acceptable, but it should at least be better than when you started. The screw on the Oscilia was such a case.

I first noticed this while undertaking maneuverability tests prior to signing the contract. I had brought a friend along as a deck hand, and he was lounging on the settee in the stern after we departed the harbor. After gently running the machinery up to temperature, I started adding rpm and pitch for a top speed test. My friend immediately came running up into the wheel house, screaming: "Stop! Stop! Something's come loose around the shaft!" As gently as I could over the ear-splitting din, I started explaining that it sounded like tip cavitation to me, but that it was by far the worst I'd ever heard. I was interrupted in the middle of this by loud crashing sounds from the stern. At this I backed off the pitch, and asked him to take the helm while I went back for a look-see. In the galley-cum-lounge I found numerous objects on the floor, including this laptop, and the objects still left on the counter and table were dancing around from the vibration.

After this, we established a safe maximum speed of 4.5 knots, and excitedly awaited the first pull-out so we could have a look at things. I suspected that heavy marine growth would prove to be a partial explanation, but the problem was much, much too bad for that to be all. Indeed, when we pulled her out the growth turned out to be horrendous, even worse than I had anticipated. The whole bottom was covered in ~5" of shells and barnacles, totalling an estimated ton (!). It took a friend of mine well over an hour to simply shovel it off the slipway after we had spent 12 man hours with the high pressure washer to get it off the boat. However, that was not the worst of it. As evidenced by the pictures, the propeller had been severely mangled in a lathe. The Tenfjord CP system had originally been mounted in a large MFV, according to information provided by the seller, and had to be adjusted to fit the Oscilia. As it turned out, the "adjustment" had been carried out by simply turning the complete assembly down to the required size, and installing it on the boat. This procedure resulted in two ugly "corners" being left on each blade, which proved to be perfect starting points for tip vortex cavitation.
The month between the first and the most recent pull-out was partially spent looking up the price of new propeller blades, which turned out to be prohibitively expensive. It also came as no surprise that having the existing blades professionally cut down fell way outside of my budget. Thus I decided to have a go myself, using nothing more advanced than a grinder and my general knowlege of what a propeller should look like. Even though the leading-edge radius should be considerably larger than that of the trailing edge, I chose to apply the same 15 cmd radius to both, as I had no way of knowing what would be correct in either case. I selected a suitable paper disc as a template, held it against the propeller blades and shaded the area to be cut with a permanent marker. I then went to work with the grinder, cutting away as much of the shaded area as practical within the confines of the propeller tunnel. Cutting brass with a grinder is especially nasty work, as it does not produce sparks, but rather warm metal chips which tend to bury themselves in the skin and produce oozing sores afterwards. For this reason I was grateful when the worst of the cutting was done, and I could get to work with a hand file to debur the edges and produce the final finish.

I'm reasonably happy with the looks of the end result. As mentioned, the radiuses cannot possibly be correct for the application, but they are by far preferrable to the pre-existing sharp corners. Also, the propeller tips are now about 1/4" thick, whereas a professionally finished job would have these thinned down to sharp edges. Given the necessary space to work, I would have attempted to fair the leading face into the pushing face, so as to leave the pushing face curvature as close to the factory finish as possible. However, I was afraid of ruining the edge curvature by working with the grinder inside the tunnel, and I had no access to faciliate meaningful material removal with the hand file, so I elected to do this later on the bench, if I cannot locate reasonably priced replacement blades.

After our time on the slipway was up, I cruised out towards our mooring location, excitedly waiting for the engine to reach operating temperature so that I could evaluate the results. I was expecting a significant reduction in propeller noise and vibration, but no significant performance increase. However, once I set the engine to my previous safe cruise setting of 1000 rpm and added four dashes of pitch (on the instrument - I don't know what that equates to in hard numbers), the speed quickly shot up to 6.5 knots, with about the same amount of vibration as earlier. When I decreased rpm by 200 and pitch with one dash, I reached the previous cruising speed of 5.5 knots with nearly no vibration at all. I find this absolutely astounding. I aproached this project with the intent of attaining a small performance increase through minimal effort, knowing that the starting point was so bad that almost anything I did would have a positive effect. The significant performance gains are hugely motivating for me, and I can hardly wait for the 12th of July when I get pulled out again.
There's still plenty to work with, as the vibrations are still worse than any other boat I've tested, though no longer by a factor of two. I will try to apply a larger leading edge radius (maybe 30-40 cm?), and se if I cand find some way of thinning or applying a small radius to the outer edges. Also, I'm increasingly sure that the venturi needs to go. I love the idea of having a competent ice breaker, but at what price? I still haven't made any fuel economy calculations - look forward to an article on fitting a flow meter to the day tank pump - but I suspect that the Oscilia consumes about the same amount per nautical mile as some 100-footers moving at the same speed. I just love the potential for improvement!

Thursday, December 23, 2010

Nå er julekvelden rett rundt hjørnet, kanten what ever...jul skal det bli okkesom! Jeg har hatt Henning på besøk i to netter. Han har sett på meg og mor løpe rundt som to alver på speed eller no. Har hatt to sene kvelder og lilleaften blir nok ikke noe bedre., men gleder meg til å pynte juletreet og mammas brunsaus til kalkunen, tror jeg kunne drukket flere liter ut av en mugge.

Det blir jo ikke så mye jul i Oscilia, vi hadde tenkt til å tilbringe litt kvalitetstid der ute i romjulen (for weee, jeg har fri HELE romjulen), men nå blir det kanskje verre. Hadde til og med kjøpt julepynt jeg skulle ha der :( Om Henning blir bedre skal han vel ut å prøve å få snekra opp en slags varmekilde. Så vi får se hva som skjer.
Nimo er også hos mor, men det fungerer ikke så veldig bra med tanke på at hun har en pus (POPS) som er en av de mest skremte, men samtidig så dominerende katt som jeg har vært borti. Begge sitter ofte på hver sin side av en dør og lukter på hverandre under dørsprekken. En løsning på problemet fant jeg i dag da, min far har sagt ok til å være kattehotell i julen, til Henning kan ta han med ut på skuta igjen. Han savner å fly ute :(
Henning skal være hos sin mor lillekvelden og juleaften, slik det har vært hvert år, gleder meg til å ha jul i eget hus. og tilbringe den mer sammen med min kjæreste. Ikke misforstå, familien er helt ok den altså :P

Så, GOD JUL alle sammen og all lykke for det nye året. Vær forsiktig med rakettene, de sprenger vet du!

Tuesday, December 21, 2010

Ting går så meget bedre nå

Lisette har jo oppdatert dere på hva som skjedde i går, så jeg skal spare meg fra å beskrive det med for mange malende ord. Jeg vil allikevel poengtere en sak, til fordel for de av dere som kanskje befinner dere i samme sitausjon en gang: Å plutselig oppdage at aggregatet pumper båten full av giftgass fra brente ledninger mens du ikke har mulighet til å bevege deg effektivt, kan være en skremmende opplevelse.

Nå gikk det jo bra, og brått befinner jeg meg hjemme hos Mamma og Ellen Lillesøster. Det er bare deilig :-) De gjorde en kjempeinnsats for å få transportert meg fra båten, og nå gjør de sitt beste for å legge livet til rette for meg. Jeg har for det meste tilbragt dagen i horisontal stilling, og blitt servert alt fra frokost og kaffe via gløgg og julekaker til rein kos!

Her hos mor er det varmt, lyst, og oseaner av plass... ikke helt slik jeg er vant med. For mange er vel ikke dette livet så langt unna normalen, men det kjennes fremmed, på en særdeles behagelig måte. Jeg assosierer til mitt ukelange besøk hos Grand Hyatt i Muscat, som står for seg selv ved siden av alt jeg har opplevd, uten hensiktsmessige referanserammer for å forholde seg til den typen luksus.

Hoften min blir hurtig bedre. I dag oppdaget jeg til min store glede at jeg kan halte rundt på et flatt gulv uten å bruke krykken. Jeg har feiret min nyvunne mobilitet ved å vandre planløst rundt, og fikse halvparten av de tingene selv som Ellen tilbyr seg å ordne for meg. Det er helt spesielt tilfredsstillende å lage en kopp kaffe, hvis det var umulig dagen i forveien. Jeg elsker det!