Δίχρονος η τετράχρονος κινητήρας

[mastrokostas]

Ανοίγω αυτό και μεταφέρω όλα τα post σχετικά με το θέμα ,για να συνεχίσετε εδώ την συζήτηση ,μιας και είναι πολύ ενδιαφέρουσα .

[drataurus]

Φιλε drataurus θα ηθελα αν εχεις τον χρονο ,να μου ελεγες τις διαφορες εσω-εξω βενζινης πετρελαιου ως αναφερεις .......<<Δεύτερος λόγος είναι τα έξοδα συντήρησης...καμία σχέση το ένα με το άλλο.>>
Επισης σε τι φθορες υποκειται το ποδι οταν τα καυσαερια περνουν απο μεσα του..........<<τροποποίησε και το σύστημα εξαγωγής καυσαερίων, ώστε αυτά να μην εξέρχονται μέσα από το πόδι, για να ελαχιστοποιήσει τις φθορές σε αυτό.>>
Σ'ευχαριστω

Δε θέλω να σε μπερδέψω...σίγουρα καλύτερα τα ξέρει ένας τεχνικός.Δεν είχα ποτέ έσω-εξω μηχανή, αλλά από συζητήσεις με φίλους ξέρω οτι η αναλογία των γενικών σερβις είναι 5 προς 1. Όπως και στους κινητήρες των αυτοκινήτων.Σε άλλες ώρες υπόκεινται τα σερβις της βενζινης, σε άλλες του πετρελαίου...και δεν αναφέρομαι μόνο στα λάδια που αλλάζουμε, διότι ασχέτως ωρών είναι υποχρεωτικό να αντικαθίσταται μία φορά το χρόνο.Επιπλέον μεγαλύτερη διάρκεια ζωής έχει η πετρελαιομηχανή, σε σχέση με την βενζινομηχανή, αλλά και μεγαλύτερη αξία μεταπώλησης, άσχετα με τη διαφορά της αρχικής αγοράς.

Όσο για τη μετατροπή του συστήματος εξαγωγής...αυτή έχει ως εξής: καταργείται η ροή των καυσαερίων μέσω του ποδιού και έτσι το πόδι απαλλάσεται από τις αυξημένες θερμοκρασίες, που προκαλούν επιπλέον φθορές στις φούσκες, τα μέταλλα κτλ, λειτουργώντας μόνο σαν μια συμβατική ρεβέρσα. Ο τρόπος έχει να κάνει με την παράκαμψη της εξαγωγής καυσαερίων του κινητήρα, τοποθετώντας ειδικά λάστιχα εξάτμισης(π.χ.της vetus), σιφώνια,εξαγωγή με βαλβίδα αντεπιστροφής. Αν έχει πέσει στα χέρια σου κατάλογος της Vetus, όπου τα παρουσιάζει σχηματικά, είναι πολύ εύκολο να το καταλάβεις πώς λειτουργεί...ακριβώς όπως στα σκάφη με άξονες.Αλλά και εκτός αυτού το έχω δει στην πραγματικότητα σε SEA-RAY sundancer 24αρι εδώ στο Βόλο.Και δουλεύει ά ψ ο γ α.

Τέλος για την 5η παρατήρηση του George, έχω ακούσει περί λεπτών αυλών στους κινητήρες της HONDA, με τα αποτελέσματα που ήδη αναφέρθηκαν.Επίσης δε συμφωνώ με την ιδέα του υπερσυμπιεστή...τα ατμοσφαιρικά μοτέρ έίναι αποδεδειγμένα πιο αξιόπιστα.

Ελπίζω να βοήθησα λίγο, αν και δεν είμαι ειδικός...απλά τη γνώμη μου εκφράζω...αν είμασταν σε chat, θα γινόταν πιο καλή κουβέντα.

[ΓΙΩΡΓΟΣ88888888]

Τελικα οπως αναφερετε και οι δυο φιλοι μου,ως προς τα tourbo γεναται μεγα ερωτημα αμφιβολιας(θελει η τουρμπινα αλλαγη καποια στιγμη?? τα τουρμπο ,φθειρονται -πεφτουν ,γρηγοροτερα απο τα ατμοσφαιρικα μοτερ??) διοτι οι νεες κατασκευες των εσω-εξω πετρελαιου οπως FNM νομιζω επισης YANMAR και MERCRUIZER παρουσιασαν απο περυσι μοτερ με μπλοκ κινητηρων αυτοκινητου μαριναρισμενα και μισου βαρους και κυβισμου και τιμης (ως καινουρια ) απο τα παλαιοτερα γνωστα μεχρι σημερα με τις ιδιες μεγαλες ιπποδυναμεις ομως φερουν τουρμπο για να επιτυχουν αυτα τα αποτελεσματα.!!
Υπαρχει καποιος να μας διαφωτισει??

[drataurus]

Κατά τη γνώμη μου το ατμοσφαιρικό μοτέρ έχει μεγαλύτερη διάρκεια ζωής, όπως επίσης και κάθε μοτέρ που δουλεύει σε χαμηλές στροφές, αλλά το τούρμπο αποδεδειγμένα δίνει αυξημένες αποδόσεις και όσο αφορά τους έσω κινητήρες (άσχετα αν έχουν άξονα ή πόδι) επιβάλλεται να φέρει turbo...τα φορτία που αναλαμβάνουν να κινήσουν είναι μεγάλα, δεδομένου οτι για παράδειγμα ενα σκάφος 40 ποδών ζυγίζει τουλάχιστον 8 τόνους.
Μοτέρ με μπλόκ κινητήρα αυτοκινήτου πρέπει να έχει βγάλει η cummins...(αν μπεις και στο youtube θα δεις βιντεάκια οπου ιδια ακριβώς μοτέρ φορούν και φορτηγάκια).Για την YANMAR κάπου έχω διαβάσει οτι στην ουσία είναι ΤΟΥΟΤΑ αλλά δεν είμαι σίγουρος.

http://www.youtube.com/watch?v=E-mJm97F_iM
http://www.youtube.com/watch?v=H9h7YPVRBnA

[NICK9696]

Hardware
Let us now turn to what makes a seaworthy RIB suitable for our extreme seas.

RIBs come in all shapes and sizes. Most are very good sea boats as we all know but some are very much better in bad sea states. A RIB that is designed with racing in mind, by implication has a long narrow hull with little buoyancy in the bow. Regrettably, these hulls will very soon stuff their noses in the troughs and come to grief. What is needed is a high-shearing bow with plenty of buoyancy and a 50% overhang of the tubes. Some RIBs have tubes that are so narrow, they are virtually ineffective in big seas and one wonders why they qualify as a true RIB. The 50% overhang rule ensures optimum upward pressure from the seas and makes for a vastly more stable boat. On the downside, this extra loading puts extra strain on the tube fastening system, which has to be very carefully and strongly constructed. We have all heard hair-raising tales of tubes parting company with their hulls. This can lead to catastrophic results, for it is the tube alone that makes for the outstanding safety and sea-keeping qualities. Well-designed RIBs should have an inboard gunwale or upstand, to act as a secondary line of defence should you loose your tubes or, more likely, if they become deflated for any reason. It also provides a much firmer foundation for the tubes anchoring system. Tubes should be of at least 600mm diameter to optimize their true potential, not only for buoyancy’s sake; any narrower, and you exponentially enhance the likelihood of persons falling overboard. It’s something to do with the height of the average knee and centres of gravity.

On the subject of hull constructional materials, I don’t want to ruffle any feathers, but although GRP possesses many fine qualities, of which we are all fully aware, it is a material that takes very badly to crashing into rocks. We regularly strike rocks with our aluminium hulls while on test, with great force that would have taken out a GRP hull. On the face of it, GRP has immense strength comparable with steel and aluminium, but what the technical fact sheets do not tell you is what happens when the material crashes into rocks or any other hard object. The gelcoat smashes open with little effort, revealing the soft glass strands, which, in a millisecond, pick up on the rock in a snagging motion. An implosion of forces takes place, causing great damage, due to the inability of the material to slide over the object. As a result, the damage is nearly always very severe compared with aluminium, which has the great ability to slide over things. When comparing the two materials, I often say to people, “If I give you a hammer and two saucepans, one made of GRP, the other of aluminium, which would you hole the quickest?” It has to be GRP.

Sooner or later in extreme seas you will ship a vast amount of green water. When we build commercial RIBs for this environment we have a transom-less stern that evacuates water in seconds, or, at least, well before the next big wave comes along. Failing this, it is essential you have very large scuppers; so many RIBs have pathetic outlets with very high transoms, which would contain many tons of water and render the RIB in a highly dangerous state.

In certain calmer situations, you maybe able to anchor; it is no good having a strong anchor and loads of warp if the fastening point is not man enough to take the forces. Our criteria is that the Sampson post should be strong enough for a crane to lift the whole boat out of the water if necessary; this can also be very helpful as your RIB can be salvaged with a quick single-point lift. Hand holds should abound at every conceivable ergonomical point, the higher up the better in many cases.

Outboards
Most RIBs are powered by outboards and alas, as such, are disadvantaged in any large sea state. In general, most RIBs in big seas will be off the plane, and we then have a planing hull trying to be a displacement hull - not an ideal state of affairs. The LCG is all wrong unless you have weight up forward, which is usually impractical. With too much weight aft there is a real chance of you pitch-poling backwards in extreme conditions whilst powering into extreme seas against the wind. The other danger is the RIB slipping back down the back of a wave at a high angle and burying its transom and outboard into the sea; unless you have an inversion proofed model, the engine is very likely to be overwhelmed and stop. Conversely, going with the wind, the aft LCG leads to a lighter, more buoyant bow that is helpful in a broaching situation, but you must be aware of the shortened effective keel length, which makes for very sensitive steering on the face of a wave.

Inboards/outdrive
The LCG is further forward than with an outboard, so performance into the wind and seas is that much better; generally, the engine and electrics are afforded much better protection from flooding. Power trim and tilt is shared with outboards, but beware this hardware hitting rocks, snagging ropes or, worse, casualties in the water. Use power trim and tilt to advantage in extreme seas by keeping the bow down whilst going into the waves, so lessening the chance of pitch-poling, and in order to keep the bow up when running before, to lessen the chance of stuffing.

Inboards/waterjet
This is perhaps the finest mode of propulsion for these conditions; you do not have to worry about hitting things and the LCG is even further forward due to the longer transmission train. But the biggest benefit is the controllability when surfing down large waves, for without any appendage immersed in these unpredictable waters, control is far more predictable and precise. The helmsman can divert huge amounts of power from forward movement to both steering and reverse, via the bucket. He can also slow down prior to possible broaching, which is impossible with a gearbox. Another unique feature is that, when travelling into large waves and risking that awful free fall before crashing into the trough, with the potential for serious damage to both RIB and limb, there is a little trick you can employ to great effect. Just before you become airborne, drop the bucket to vertical, rev up, and the RIB will see-saw over the wave crest as the stern is lifted up by the jet flow, whilst the bow will dive gently into the trough. Remember also that you do not risk transmission breakage with a jet, due to over-speed whilst airborne, as you do with propellers.

Waterjets have sometimes got a bad name for cavitation from a standing start in aerated seas; this is invariably due to penny-pinching over the size of jet. Get a jet of sufficient diameter and the problem is over.

Finally, I must cast a warning. In spite of any perceived encouragement contained in this article to venture out in these extreme conditions, you should have also been left in no doubt of the possible, morbid consequences. Do not do it unless it’s completely unavoidable.

[NICK9696]

PETROL OUTBOARD V DIESEL INBOARD Petrol 79p/litre (£3.61 per gal) Diesel 32p/litre (£1.46 per gal) 200hp outboard 12 gals/ 55 litres
per hour. 150 hours use
per year, Total Cost
£6,498 Diesel inboard 7.2 gals/33 litre
per hour. 150 hours use
per year, Total Cost
£6,498 Based on Garage Fuel Petrol 72.9p/litre (£3.33 per gal) Diesel 65.9p/litre (£3.01 per gal) 200hp outboard 12 gals/55 litres
per hour 150 hours use
per year Total Cost
£5,994 Diesel inboard 7.2 gals/33 litres
per hour 150 hours use
per year Total Cost
£5,994

REED’S REVENGE

Paul Reed tells of his struggle to find the boat of his dreams…until finally a Yamaha diesel powered Revenger 27 RIB ended the saga….
So you want a new boat . You have been out of the market for a few years. You keep on having these agonizing thoughts, you keep telling yourself that you don't really need a boat of your own, you have plenty of friends with boats and it is not as if you have missed out over the last few years by not owning one and it really is a lot cheaper to do your boating on someone else's craft!
But, eventually you start `just having a look' to keep your eye in and abreast of developments and new fangled ideas and anyway it gives you some great opportunities for debate in your favorite watering hole over the long cold and dingy winter months between the Guinness stand at Southampton Boat Show and the same at Earls Court.
This has been my dilemma for the last few years having been brought up around sailing boats and educated to the belief that rag and stick ruled and those smelly old stink boats should barely be tolerated. It was not until my verv late teens that I was in a position to buv my first speed boat, a 17' 6" Broom with a 110hp Johnson V4. The boat was reasonably new, but the engine was of 62 vintage and of enormous proportions. It got me on the water and gave me hours of endless fun and was not that thirsty as we spent most day trips being towed back remonstrating what a good old engine even if a little temperamental.
Next I was tempted by the glory of the racing world. Every day on my way to work I drove past this sleek looking hull sitting on a trailer in a front garden. Eventually curiosity got the better of me and I found myself at the front door inquiring if the said hull was for sale and if so what it was. It turned out to be an Avenger 21 complete with a Volvo straight six and wizzy outdrive with a two bladed prop and the owner telling me all about the boat's racing pedigree. A few inquiries later ending up at DB Marine in Cookham seemed to confirm the story, and I just had to own her. Following a full refit and engine rebuild to ensure reliability followed by a trip home from Cowes when the head gasket went and our only means of return to Poole under our own steam was to remove the offending spark plug, sit one crew member on the bow and home we came at about 15 knots with the bilge pump on overtime and the oil rapidly resembling Birds custard.
Time was up I thought, I'll have to buy a new boat, spend a bit more, and actually enjoy my boating. How little did I know that was just the start. Off I went in search of a brand new gleaming sports boat and I found my dream not far from home - a Chris Craft Stinger 202 fitted with a 4.3 LT Mercruiser. A stunning looking boat with triple command seating set up for Driver, Navigator and Throttle man. The purchase was completed from the importer on the Friday of the May Bank holiday weekend and we spent the weekend playing. By Sunday a few items required attention, not least the power trim pump base. This had broken loose and a friend volunteered his services to re-glass the affected areas.
Many rolls of kitchen towel later and with signs of further weeping water and a very concerned look on my face, I watched with horror as my new boat was lifted clear of the water and the cracks in the gel coat became apparent. I immediately requested Cox and Haswell to carry out a survey. They confirmed my worst fear - the boat had broken its back. The importer was contacted post haste and in all fairness was very professional and the matter was rapidly resolved.
That was a close one and I started to wander if boats and I were the correct mixture! However not easily deterred I purchased a new Johnson 225hp outboard and went in search of a 21ft sports hull to hang it on. I chose a new Boss with a deep V hull and much promise. Six weeks later engine fitted and boat due for delivery, the manufacturer requests permission to demonstrate my boat to a prospective customer on the way to deliver it to me. My new boat never arrived and they would not return my calls so into the car I climb for a hasty drive to Surrey. When I get there, my boat is sitting on the trailer with signs of the forward bulkhead having got a bit too cozy with the outside of the hull. A very swift conversation and a few mutterings resulted in a very swift termination of that relationship, but I now had a brand new Johnson 225 sitting in my garage. Very economical you know!
What next, I am driving through Bournemouth and attached to the back of a Range Rover is a new 22ft sports hull I don't recognize. So, following and frantically flashing my lights the driver is persuaded to stop. A Marline Mirage I am informed, on its way back from the East Coast boat show to its home in Exeter. Cards are exchanged and an invitation to Torquay for the race weekend to try the boat is gratefully accepted. An order is placed ... "what a lovely bunch of people, what a great design," I thought, "we are going to be very happy together." What a shame they didn't know how to put a boat together. I think the boat ended its life in Gibraltar doing the cigarette run. She was certainly fast enough.
That was it, time to give up, it must be me. I successfully stayed away from boat ownership until early in 1996 my curiosity starting to get the better of me. I had noted with interest the emergence of RIBs and started to look around BWM, Humber, Ocean, and many others. I was still not convinced and left the idea for another year. The one essential ingredient to this purchase was the people building the boats. Following my previous experiences, I wanted a proven hull and an established manufacturer who valued their reputation. The short list ended up between Scorpion and Revenger. This was no reflection on the other manufacturers, I just felt these two boats had the qualities and styling that best suited my personal requirements and they were built in the South of England. So how to make the final decision... both very good boats ... both professional companies. In the end, it came down to personal preference. I chose the Revenger 27.
Now the hardest bit - what choice of engine? Oh what torment! Either Mercury or Yamaha single 225hp or twin Mercury XR2's. One 2.5 Efi Offshore or what would happen if we build the boat with a Yamaha 420 Sti diesel. Good power to weight ratio, 240hp. Lots of torque and very good fuel economy. Oh, what a choice. My first recommendation is to talk to Dave Crawford Marine at Lymington...ask a question get a straight answer and a very competitive price.
Looking at the running costs, there was only one choice. I estimated that if I could afford it I would use the boat for about 150 hours a year. Based on that, the figures were very persuasive.
OK, so the diesel engined boat is going to cost about a third more to build, but with intended use and the higher resale value it became a very conclusive argument.
So the boat was ordered with the Yamaha 420 Sti. I would like to say everything went smoothly, but that would not be entirely true. When boats are being built to your specification problems can occur. I would recommend any prospective purchaser to spend a great deal of time checking and detailing the specification. Get it down in writing.
My thanks have to go to Rick and Ian at Midas Marine who masterminded the whole plan on behalf of Revenger Boat Company, a truly professional team of people who built me a first class boat that has exceeded every expectation in terms of performance and reliability. Last, but not least my thanks go to marine photographer Gordon McMath, without his help from start to finish I doubt the project would have seen completion. In summary, the Revenger 27 is everything it sets out to be. A superb hull, seaworthy, fast and stable. The Yamaha engine and drive is very able and an economical piece of engineering. We are still fine tuning, but currently the boat is clocking 49 Knots. At the time of writing, we recently completed our first channel crossing to Guernsey in the company of other BIBOA members using only £24 worth of diesel!

[ΓΙΩΡΓΟΣ88888888]

Πολυ κατατοπιστικα τα βιντεακια της yanmar και cummins,βεβαια η πρωτη δειχνει πιο κομψη και πιο αθορυβη και η τιμη της ηταν καλη για πετρελαιο το καλοκαιρι .Καινουρια η 220 ιπποι κοστιζε γυρω στις 14000 χωρις τον φπα.,αλλα αν θυμαμαι καλα ειχε αρκετη απωλεια ως την προπελα,εφθαναν κοντα στους 200 πισω.
Ειδομεν......