YachtForums.Com - View Single Post - Fuel Consumption....everyone please weigh in....

artwork · 10-08-2007, 11:06 AM

Chriswufgator

WHEW _ This took time to digest. Chris, you really put some time and thought into that response. I have to begin by saying I agree with some of what you say. And my disagreements stem from your not being familiar with my project. I visit this Roamer site regularly to get aluminum info. And having spent, well let’s just say ‘a long time’, on the water, I enjoy listening to the Q&A on the site. Technically my boat was (is) a Roamer 58. We am building a boat to retire aboard, and plan to travel extensively, conceivable 1,000 -2,000 engine hours a year. This makes both fuel consumption and mechanical maintenance a significant issue.

Let’s start with where we agree. The theory that it requires a given HP to produce a given speed – we agree. Up to the 'Hull Speed' that figure is somewhere between 2 and 5 HP/ ton. The variable being the efficiency of the hull design; narrow vs. wide is more relevant than round vs. hard chine. So whether you deliver that HP using 700 HP @ 21% or 200 HP at 80% makes no difference to the boat. And I agree with you that the Roamer hull is not particularly efficient, based on my 17-foot beam. We are in agreement.
Above that ‘hull speed’, consumption rises exponentially until you get ‘on plane’, but it never comes back down to displacement consumption rates. I have personal issues about whether the 58 foot Roamers ever really ‘planed’ with the 320HP DD’s. * alloyd2sea – chime in here –please. But this is beyond the scope of our discussion.

I also agree whole-heartedly that diesel engines with the new common rail fuel systems are much improved. The fuel consumption curve is better through the entire RPM range. But that 'curve' did not disappear. They are still less efficient at low RPM, and their maintenance through the life of the engine increases if they are used this way. Everything I have read (I’m not a diesel mechanic or engineer) says “Don’t run a diesel for long periods below 75-80% of its power rating”.

I also agree that at resale time, potential buyers looking for a Roamer will not want an anemic pussy-cat. So we have to ask: “When is a Roamer no longer a Roamer”? Your advice was based on a presumption that my 58 is still as it was pictured in the brochures. It is not. I found this boat, about 15 years after it had suffered a salon fire, which destroyed the roof. The interim owners fabricated a plywood menagerie that would have banished them from the Roamer Club. Since we purchased the boat, we removed everything; let me repeat EVERYTHING, down to an aluminum hull. I mean I could take 80 of my closest friends out fishing, BRING YOUR OWN OAR! A 58-foot open row boat. Now you see where I'm at? – this boat will never be a “Roamer” again.

I’d like to continue this discussion, but am short on time.

I uploaded a pic for this location but lost it in cyberspace. Sorry

NOTE TO MGMNT _ Please do not banish me from the site.

I still like Roamers and respect the ones that are intact.

10-08-2007, 11:06 AM	#8
artwork Registered User Join Date: Feb 2006 Location: Lake Huron Posts: 24	new Diesels and how big is enough? Chriswufgator WHEW _ This took time to digest. Chris, you really put some time and thought into that response. I have to begin by saying I agree with some of what you say. And my disagreements stem from your not being familiar with my project. I visit this Roamer site regularly to get aluminum info. And having spent, well let’s just say ‘a long time’, on the water, I enjoy listening to the Q&A on the site. Technically my boat was (is) a Roamer 58. We am building a boat to retire aboard, and plan to travel extensively, conceivable 1,000 -2,000 engine hours a year. This makes both fuel consumption and mechanical maintenance a significant issue. Let’s start with where we agree. The theory that it requires a given HP to produce a given speed – we agree. Up to the 'Hull Speed' that figure is somewhere between 2 and 5 HP/ ton. The variable being the efficiency of the hull design; narrow vs. wide is more relevant than round vs. hard chine. So whether you deliver that HP using 700 HP @ 21% or 200 HP at 80% makes no difference to the boat. And I agree with you that the Roamer hull is not particularly efficient, based on my 17-foot beam. We are in agreement. Above that ‘hull speed’, consumption rises exponentially until you get ‘on plane’, but it never comes back down to displacement consumption rates. I have personal issues about whether the 58 foot Roamers ever really ‘planed’ with the 320HP DD’s. * alloyd2sea – chime in here –please. But this is beyond the scope of our discussion. I also agree whole-heartedly that diesel engines with the new common rail fuel systems are much improved. The fuel consumption curve is better through the entire RPM range. But that 'curve' did not disappear. They are still less efficient at low RPM, and their maintenance through the life of the engine increases if they are used this way. Everything I have read (I’m not a diesel mechanic or engineer) says “Don’t run a diesel for long periods below 75-80% of its power rating”. I also agree that at resale time, potential buyers looking for a Roamer will not want an anemic pussy-cat. So we have to ask: “When is a Roamer no longer a Roamer”? Your advice was based on a presumption that my 58 is still as it was pictured in the brochures. It is not. I found this boat, about 15 years after it had suffered a salon fire, which destroyed the roof. The interim owners fabricated a plywood menagerie that would have banished them from the Roamer Club. Since we purchased the boat, we removed everything; let me repeat EVERYTHING, down to an aluminum hull. I mean I could take 80 of my closest friends out fishing, BRING YOUR OWN OAR! A 58-foot open row boat. Now you see where I'm at? – this boat will never be a “Roamer” again. I’d like to continue this discussion, but am short on time. I uploaded a pic for this location but lost it in cyberspace. Sorry NOTE TO MGMNT _ Please do not banish me from the site. I still like Roamers and respect the ones that are intact.