petem
Well-Known Member
Seriously, with all that fuel the boat wouldn't get on the plane to achieve the planned 20 knots. Fuel economy would be shot to bits too.
Ocean crossing in a 25' cruiser
- Thread starter Gushter
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PCUK
Well-Known Member
What's the boats displacement Tpi. I reckon it would have very little freeboard - if any! Just plain daft.
Divemaster1
Well-Known Member
I'll ignore the thoughts about sensibility and treat this as a theoretical exercise...
With the additional weight of the fuel, you will not reach the speed you hope, so with the existing propellor, you will have an overloaded engine for the majority of the journey, so engine is un-likely to last the distance/time.
Changing the propellor and aiming for a hull speed is the right option...., but how long at approx 5 - 6 knots ?
This means you still have to carry extra fuel AND food (adding to the weight)... and you will need a watermaker, as you do not wish to carry the water needed!!!
Based upon the above, and the fact that you will damage the aft cabin etc., by building / removing tankage in the living areas of the boat..... You'd be better off putting the boat on a deck load and getting it across that way...
With the additional weight of the fuel, you will not reach the speed you hope, so with the existing propellor, you will have an overloaded engine for the majority of the journey, so engine is un-likely to last the distance/time.
Changing the propellor and aiming for a hull speed is the right option...., but how long at approx 5 - 6 knots ?
This means you still have to carry extra fuel AND food (adding to the weight)... and you will need a watermaker, as you do not wish to carry the water needed!!!
Based upon the above, and the fact that you will damage the aft cabin etc., by building / removing tankage in the living areas of the boat..... You'd be better off putting the boat on a deck load and getting it across that way...
Gushter
New Member
Thank you for the comments and the advice. By the way, this is not a troll. I like the idea to treat it as a theoretical exercise and let people decide for themselves if they want to take this "unreasonable" risk. Just a couple of comments though:
1. The idea here is to cross for a min amount of time. If crossing at hull speed then a sailboat is a much more reasonable choice and then the Pacific is a more interesting ocean (you end up somewhere nice). I have done Newport to Bermuda once in 47' foot racing boat and once in a 30' cruising sailboat. Both times the wind did not exceed F4 and it was pleasant except for the extra effort on the racing boat where we had to change the sails every 4-5 hours to eak out the max performance so we did not sleep much. So, if the weather is cooperating, I do not see the problem. If anything I see crew tiredness as a bigger problem. Given our objective to do it in less than 8-10 days, there is a much higher chance of getting a good weather window than crossing at hull speed in 25 days. The outboard motor will be a backup in case the main engine breaks down (in that case we would dump the excess fuel to balance the boat better). We are clearly going to have a watermaker.
2. I agree that may be a bigger boat will reduce the risks substantially, so I will look into relaxing that constraint. Something in the 35' range becomes a lot easier but then the fuel requirement multiplies.
3. We have taken into consideration the fuel distribution, the need to manage the tank volume, the freeboard and so on. All of this is manageable but I agree that if we hit bad weather in the first 3 days when the boat will be most overloaded, it will likely break into pieces. However, we believe that we would only launch if we have a solid favorable forecast. Any forum members that have overloaded their boats 30%-50% willing to share their experiences on how easy it is to maintain 15-20 knots in F4 to F5 conditions with the typical long period ocean waves?
Again thank you for the advice, very valuable and may dissuade us at the very least.
Gushter
1. The idea here is to cross for a min amount of time. If crossing at hull speed then a sailboat is a much more reasonable choice and then the Pacific is a more interesting ocean (you end up somewhere nice). I have done Newport to Bermuda once in 47' foot racing boat and once in a 30' cruising sailboat. Both times the wind did not exceed F4 and it was pleasant except for the extra effort on the racing boat where we had to change the sails every 4-5 hours to eak out the max performance so we did not sleep much. So, if the weather is cooperating, I do not see the problem. If anything I see crew tiredness as a bigger problem. Given our objective to do it in less than 8-10 days, there is a much higher chance of getting a good weather window than crossing at hull speed in 25 days. The outboard motor will be a backup in case the main engine breaks down (in that case we would dump the excess fuel to balance the boat better). We are clearly going to have a watermaker.
2. I agree that may be a bigger boat will reduce the risks substantially, so I will look into relaxing that constraint. Something in the 35' range becomes a lot easier but then the fuel requirement multiplies.
3. We have taken into consideration the fuel distribution, the need to manage the tank volume, the freeboard and so on. All of this is manageable but I agree that if we hit bad weather in the first 3 days when the boat will be most overloaded, it will likely break into pieces. However, we believe that we would only launch if we have a solid favorable forecast. Any forum members that have overloaded their boats 30%-50% willing to share their experiences on how easy it is to maintain 15-20 knots in F4 to F5 conditions with the typical long period ocean waves?
Again thank you for the advice, very valuable and may dissuade us at the very least.
Gushter
Divemaster1
Well-Known Member
With a 30 - 50 % overload on a MOBO, you will not achieve 50% of Max design speed! even at WOT... and your engine will probably fail....
A diesel engine is designed to achieve x RPM at a certain % of load... that means at 2000 RPM, the engine will have X fuel in combustion chamber, creating a Y size "bang" and thus expected reciprocal force.... (downward force on piston).
if you at that certan % engine load do not achieve the 2000 RPM, the governor will still inject the ammount of fuel required for the load (X)... but the engine may not have the RPM to deliver the air required .... but if it does, the load on the engine parts, through bigger load/friction on conrod, driveshaft, disposal of heat from combustion (valves do not open frequently enough and water circulation is too low)etc., at a lower RPM than designed, will mean that the engine probably will overheat (at given RPM), loose lubrication properties of the oil etc and have a fatal failure...
IMHO if you want to do this, you will have to accept hull speed and no more, unless you have the ability to re-build engine mid-way...
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prv
Well-Known Member
At displacement speed it all starts to sound a lot like Half-Safe to me - the amphibious jeep in which a crazy Aussie and his wife crossed the Atlantic in the 50s. They had to make about half a dozen attempts before they actually got going properly and made the crossing - I think for the successful attempt they were towing a floating fuel tank behind them. Seem to remember something about them needing to take on extra fuel from a ship they happened to meet - presumably had they not been lucky enough to encounter it, they would have run out of fuel mid-ocean and died of dehydration and starvation...
Pete
Pete
Richard Shead
Slipped Anchor
Lets not forget some people have wind surfed across the Atlantic ...... Followed by a 200 foot support vessel. So it can be done.
rafiki_
Well-Known Member
Difficult to overload a windsurfer though Richard.
TimBennet
Well-Known Member
Both those statements can't be true.
Bertramdriver
Well-Known Member
It's an interesting thought though. I've often been asked the same question by my yottie friends during alcohol fuelled philosophical discussions. They know little of a mobo's limitations and as a German friend will be sailing his 28' sail boat across to Florida this winter, they wonder why my 47' couldn't do it.
I know of several non blue water mobo's who've made the trip across, usually with the extra fuel stored in bladders spread around the boat. But there is a commonalty in that they tend to be displacment, twin engined, over 35' and diesel.
Maybe MBY would organise a cruise in company this autumn?
I know of several non blue water mobo's who've made the trip across, usually with the extra fuel stored in bladders spread around the boat. But there is a commonalty in that they tend to be displacment, twin engined, over 35' and diesel.
Maybe MBY would organise a cruise in company this autumn?
sarabande
Well-Known Member
You will find that UK harbour masters and CG have a few powers which prevent unsafe boats from going to sea.
At the very least you will need to plan on the outboard having enough fuel to bring you home, so it needs to be diesel (and therefore large) or petrol (in which case you need to fill the remaining space int he boat with gasoline. I'd suggest you stick to alcohol-fuelled philosophical discussions, and stay away from sensible boating.
At the very least you will need to plan on the outboard having enough fuel to bring you home, so it needs to be diesel (and therefore large) or petrol (in which case you need to fill the remaining space int he boat with gasoline. I'd suggest you stick to alcohol-fuelled philosophical discussions, and stay away from sensible boating.
Portofino
Well-Known Member
Ok I,ll toss in 2 pennys worth
Assuming a " can do attitude "
10-12 days or shorter needs to be a planner ,but has to carry the fuel as well -look at this -note the narrow beam+ very deep V for sea keeping at arround 20-25 knots or what ever
http://www.yachtworld.com/core/list...nits=Feet&access=Public&listing_id=76712&url=
Hang on I have not finished -remove the petrols and fit a lowdown torquey diesel like the D6 ( none supercharged 310 variant) .
Ordinarily this would rocket to 40+ knots but you don,t want this -You need to re-gear/ reprop it so the massive torque curve hit a sweet spot at 20-25 knot -so it can lft up and plane with the extra wieght ( displacement of the fuel)
Down below loads of room to fit fuel bladders evenly distributed + food +water etc
Power/ torque of the " new" engines + fuel efficiency of the sterndrives ( correctly propped) in this hull
You might have a theorectical chance of blatting across arround 25 knots ish? In the time window you have set
Assuming a " can do attitude "
10-12 days or shorter needs to be a planner ,but has to carry the fuel as well -look at this -note the narrow beam+ very deep V for sea keeping at arround 20-25 knots or what ever
http://www.yachtworld.com/core/list...nits=Feet&access=Public&listing_id=76712&url=
Hang on I have not finished -remove the petrols and fit a lowdown torquey diesel like the D6 ( none supercharged 310 variant) .
Ordinarily this would rocket to 40+ knots but you don,t want this -You need to re-gear/ reprop it so the massive torque curve hit a sweet spot at 20-25 knot -so it can lft up and plane with the extra wieght ( displacement of the fuel)
Down below loads of room to fit fuel bladders evenly distributed + food +water etc
Power/ torque of the " new" engines + fuel efficiency of the sterndrives ( correctly propped) in this hull
You might have a theorectical chance of blatting across arround 25 knots ish? In the time window you have set
Bertramdriver
Well-Known Member
If you were better informed you would be aware that the crossing has been done already by non blue water mobo's and as for the CG's I think think the guys in the Azores have seen stranger things put sea. I can only assume that being a sensible boater yourself you must be right on these matters as I only spend four months a year afloat.
sarabande
Well-Known Member
I tell you what. Load the boat with steel ballast to the amount of diesel, water food, and supplies that you are intending to take. Have a look at the remaining freeboard, and then take the boat out in some rough stuff and see how she performs. If you come back you will have a good, pragmatic idea of the hull performance envelope, and the engine fuel consumption.
My main worry would still be getting back from halfway across under outboard power alone in displacement mode. The fuel requirements for that scenario are in dire need of detailed examination, which you seem unwilling to undertake.
My main worry would still be getting back from halfway across under outboard power alone in displacement mode. The fuel requirements for that scenario are in dire need of detailed examination, which you seem unwilling to undertake.
northwind
Well-Known Member
See if you could borrow this guys boat:
http://www.tohatsu.com/news/seiko.html
Edit: more here - http://seestjohn.com/st_john_life/tag/seiko-da-grindelwald/
He had a 170 gallon tank!
http://www.tohatsu.com/news/seiko.html
Edit: more here - http://seestjohn.com/st_john_life/tag/seiko-da-grindelwald/
He had a 170 gallon tank!
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sealines28
Well-Known Member
Plus you would not get insurance for this trip. I planned to take my 28 to the med, tried to get a few quotes, no one would do it for this size/type of boat, they thought I was going around, and not through France etc. They would then once they got the route I planned to take (through instead of around).
Bertramdriver
Well-Known Member
My main worry would still be getting back from halfway across under outboard power alone in displacement mode. The fuel requirements for that scenario are in dire need of detailed examination, which you seem unwilling to undertake.
Somewhere along the way I seem to have been given responsibility for this thread. How did this happen?
Somewhere along the way I seem to have been given responsibility for this thread. How did this happen?
sarabande
Well-Known Member
Post #1, in case you have forgotten 
"We are just talking about something we want to do and say we have done it"
It's the first time you have mentioned responsibility.
Try starting here to get an idea of what you have to do to plan a voyage.
https://www.gov.uk/owning-yacht-sail-boat-motorboat
"We are just talking about something we want to do and say we have done it"
It's the first time you have mentioned responsibility.
Try starting here to get an idea of what you have to do to plan a voyage.
https://www.gov.uk/owning-yacht-sail-boat-motorboat
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TQA
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Hmm driving a mobo, on the plane, at night, in mid Atlantic, this sounds like a really safe thing to do. NOT!
It gets a bit rough out there you know. Especially if you get reinforced trades blowing, 20 to 25 knots which is great if you have rags on sticks to steady things up, not so good in a mobo.
It gets a bit rough out there you know. Especially if you get reinforced trades blowing, 20 to 25 knots which is great if you have rags on sticks to steady things up, not so good in a mobo.
lenseman
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Welcome to the Forums.
It will not work diesel powered unless you intend to drift most of the way.
If you really are thinking of crossing the oceans, then throw away the diesel engine and gearbox, replace with a marine electric engine. Make up the weight of the removed diesel engine minus the electric engine using Leisure / Deep-cycle batteries.
Dispose of the diesel tanks, make weight using deep-cycle Leisure batteries to the weight of the tank(s) and diesel contents. Keep all weight low down
Fit solar panels and controller.
This is possibly the only way you will do it with the boat specified .
If you do not reply to this then I assume you have gone back to live under a bridge somewhere in Finland, Norway or Sweden?
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