How easy is it to handle a big single engined boat?

[Nautical]

Am I reading that correct ? 3.2 knots = 1.88 MPG,

the later figure seems impressive for a 75' boat until you note that is at only 3.2 knots, I doubt even the most ardent long distance cruising person would stick at 3 knots. Common thought is 7 knots is the optimum speed for very long distance cruising but on that boat is (at a guess) less than 1.0 MPG ? or have I got that back to front.

 

[mjf]

Am I reading that correct ? 3.2 knots = 1.88 MPG,

the later figure seems impressive for a 75' boat until you note that is at only 3.2 knots, I doubt even the most ardent long distance cruising person would stick at 3 knots. Common thought is 7 knots is the optimum speed for very long distance cruising but on that boat is (at a guess) less than 1.0 MPG ? or have I got that back to front.

I calc at the (agreed not cruising speed) 3.2knots she uses 0.41 gal per mile


So 8knots is 1.32mpg which is impressive for a huge boat - she big even by 75' standards.

 

[longjohnsilver]

I calc at the (agreed not cruising speed) 3.2knots she uses 0.41 gal per mile


So 8knots is 1.32mpg which is impressive for a huge boat - she big even by 75' standards.

Unless I'm mistaken, 8kts = 48 litres per hour = approx 10.5 gallons which equates to just under 0.8mpg.

 

[Neil_Y]

The Bandido 75 will very soon come as standard with Seatorques so you might see slightly better figures in the future.

 

[Nautical]

Ah yes indeed ! , thanks for stopping by at stand, I think I was in a meeting when you called (swaning off to Super Yacht Lounge on some yacht mag Editor's expense account )

 

[Deleted User YDKXO]

That's interesting, Trev and slightly surprising. You would think that a D boat which is optimised for efficient D cruising would be more efficient at D speeds than a SD boat. I guess it may have something to do with the fact that D boats are generally built heavier and carry more fuel/water?

 

[Nautical]

I don't think it is a weight issue, once you get X weight moving at displacement speed it takes a surprisingly small amount of power to keep it moving, it is when you start pushing toward the maximum hull speed that you start to really dig into the water and that takes power, lots of it and therefore lots of fuel. A SD hull can be pushed to to a higher speed for less power because of its hull design, having said that once you get past the 12 knot barrier it too starts to consume bigger numbers in fuel.

We look on SD not for its ability to reach dizzy speeds but because it is easier to push at a higher displacement cruising speed yet is a very sea worthy design for long periods of open water cruising. Almost all our owners cruise at around 10 -11 knots and only push on if there is a need.

A displacement hull is a great tool if you want to carry huge weights, like a fishing vessel that has to carry a 100 tons of catch, much of the weight can be carried lower down in the hull as opposed to a planing or even a hard chine SD which is what you want when loaded to the gunwales .

I guess a lot of the sea keeping reputation for D hulls comes from the fact that nearly all ocean going trawlers etc are D and have been around for, well since the begining really, but these days a good SD hull can be as good if not even better in many respects, they handle quicker, can generally speed up or down according to weather conditions and pretty much cut it alongside any D hull. However sea keeping is one thing, construction and design is another, historically D hulls were little constrained by weight so you build them like brick outhouses with steel hatches, watertight doors, massive layup, it didn't really affect the fuel burn at a 7-8 knt cruise whereas 20 extra tons on a planing hull made a big difference to its ability to plane or even stability. SD with all the new technology available in construction and lighter weight materials yet just as strong is a good compromise between the two.

As an aside our OR 80 comes in at around 100 tons fueled up (3000 gallons) so even with new tech etc it is still one heavy boat for 80', double the weight of say a Fairline Squadron 78.

 

[arthor]

As far as the maneuvering goes, I am rubbish at getting my Fjord 27 backwards into our berth. As I am paranoid about only having one engine anyway, I intend getting a hi thrust outboard as an aux and then using as a parking engine. Surely maneuvering at low speed has got to be easier with the directional thrust of an outboard???
I intend fabricating a swim platform with the outboard mount of to one side, set up remotely.
Sounds mad but has an element of feasibility to at least make it worth doing some drawing and serious thinking. Anyone else park up using an aux outboard??

 

[jimmy_the_builder]

As far as the maneuvering goes, I am rubbish at getting my Fjord 27 backwards into our berth. As I am paranoid about only having one engine anyway, I intend getting a hi thrust outboard as an aux and then using as a parking engine. Surely maneuvering at low speed has got to be easier with the directional thrust of an outboard???
I intend fabricating a swim platform with the outboard mount of to one side, set up remotely.
Sounds mad but has an element of feasibility to at least make it worth doing some drawing and serious thinking. Anyone else park up using an aux outboard??

This is an old thread .... but if you're going to buy an outboard, with remotes, and build a swim platform - why not just spend your money on having a bowthruster installed instead? It'll solve your berthing probs, and add value to your boat (or at least make it more attractive at resale time). Adding a non-standard swim platform might have the opposite effect.

Cheers
Jimmy

 

[AndieMac]

As far as the maneuvering goes, I am rubbish at getting my Fjord 27 backwards into our berth. As I am paranoid about only having one engine anyway, I intend getting a hi thrust outboard as an aux and then using as a parking engine. Surely maneuvering at low speed has got to be easier with the directional thrust of an outboard???
I intend fabricating a swim platform with the outboard mount of to one side, set up remotely.
Sounds mad but has an element of feasibility to at least make it worth doing some drawing and serious thinking. Anyone else park up using an aux outboard??

How do you intend steer the aux. in close quarters?

You will still have the wandering bow to contend with on a windy/tide driven day, regardless of what you are doing to the stern.

Have you explored your boats transverse thrust ability, short bursts ahead and astern, providing the astern burst 'bounces' you in the right direction.

I am a firm believer in retro fitting custom goodies to the boat, but not sure about this option to improve berthing, the aux. outboard won't have the 'oomph' in anything but a day with benign conditions.

Good luck.

 

[arthor]

Interesting replies gents.

The main reason for the outboard would be as aux. Two further uses for it would be on the river sometimes and with the possible benefit as a parking engine. A high thrust engine with a big prop (25hp ish??) would move her along at displacement speed even when not in flat calm on a still day.
Regardles of whether the motor is on a bracket or bolted to the transom/swim platform, if it won't move a boat along then one can only ponder what size other single engine boats have as aux outboards??

 

[PaulGooch]

Hanging a 25hp motor on the back of a 27 footer is not going to be a good idea, way too heavy to be fitted to a bathing platform or an aux outboard bracket. Typical aux engine for a boat your size is more likely to be 6hp four stroke, although you'd get away with a slightly more powerful 2 stroke (if you can find a good reliable second hand one).

If you make a bathing platform up and fit a 25hp outboard to it, be sure to have a couple of people taking video of the maiden voyage. It'll make for some top notch YouTube entertainment

 

[moonraker 36]

ARTHOR.
you don't happen to keep your boat at stanilands do you?

 

[AndieMac]

It could depend on your area of operation, open sea, strong tides etc.. as to what may work as an aux.
My boat has a 15 hp, LS, (2 str.) on 23', good for 4.5 to 5.0 knots at cruise in flat water, with an anticipated range/run-time of at least 4, maybe 5 hours on 25 litres, running at a cruise.

I am sure a suitable stern platform could be constructed. From memory your vessel may have a 'canoe stern'? which will possibly add a bit more complexity to the concept. The stern/transom may need to be stiffened at the attachment points internally, given the intended weight to be carried, and the potential leverage the OB will have in pitching seas, even though it is a displacement vessel (?)

Whatever you use (SS and teak, alloy or GRP composite supported by SS uprights etc..) is going to need to be substantial and well engineered, and the associated costs I imagine will be high.
The additional overall length the platform and the fully raised/retracted OB will add to your boat for manoveuring and berthage, is another thought.

You often see comments about the irresponsible small mobo owners (runabouts etc.) heading off without an aux. motor, but not much about the mid-sized ageing single diesel?

 

[moonraker 36]

Interesting replies gents.

The main reason for the outboard would be as aux. Two further uses for it would be on the river sometimes and with the possible benefit as a parking engine. A high thrust engine with a big prop (25hp ish??) would move her along at displacement speed even when not in flat calm on a still day.
Regardles of whether the motor is on a bracket or bolted to the transom/swim platform, if it won't move a boat along then one can only ponder what size other single engine boats have as aux outboards??

SURLY the outboard would be better fitted on the bow if you want to go backwards into your berth!!!
OR twin 8hp yammi 2strokes on the stern for manouvering ability!! this would give you tripple screw!!!
if you are at stanilands, i think you have spent too many hours in the yacht club!!!!!
get an aux.for a back up eng. and just practice the manouvering bit.

 

[arthor]

Nope. I am not at Stanilands. Don't even know where that is. As I said, the main reason for the outboard would be as an aux. The boat is not a canoe stern and is semi displacement. The aux will never push it along at more than displacement speed so I was really wondering what sort of power I would need. Andie mac - My displacement speed will be a bit higher than yours due to the extra length. I just want to make headway in an emergency. Even on the river, I don't fancy suddenly being without power. I don't think thats paranoid actully.
A 9.9 Merc bigfoot is light enough for the more robust cantilever, spring loaded brackets. Does anyone have any experience of them. Can the outboard be hooked up to remote steering and throttle and be left that way up or down? My thoughts with fabricating some sort of swim platform with an offset outboard mount would mean the possibility of a slightly larger outboard with power up and down. There is a 27' Viking next to us with a 15 hp honda in a transom hole and they get about ok. He will have an easier job than me getting into his berth with his directional thrust outboard on the back than I do. If a stern thruster is often just an electric motor, I am sure that it wouldn't need much to get the boat moving nice and slow into my berth with a bit more control than I have now.

 

[moonraker 36]

ok ARTHOR.
just a chap at the same marina as me was talking about doing the same thing as you.but not for the manouvering into the berth bit.
i use a 9.9 mariner on a 3m rib they are quite a powerful bit of kit,but i think weight wise not much lighter then a 15hp basicaly the same engine.so i would go for the 15hp should be more than enough to push the boat about.

 

[arthor]

Moonraker,

I am getting the impression that my last post may have come across as a bit stand offish. Many apologies if that is the case.
Just spotted your location and google mapped Staniland. I can see why with me being in Yorkshire it would be reasonable to think I may be at Staniland. I am at Boroughbridge.
I know all my musings and ideas for the boat may sound daft and I really ought to find another but I have got quite attached to her and reckon that with a bit of attention and modification she will be smack on for everything we need. Mainly river and estuary but with the occasional foray out to sea in fair weather.
I have always wanted to build my own (or at least fit out/restore) and I am wanting to see if I expend my energies on this one or get another when we feel brave enough to venture out into the salty stuff. By that time I will have lots of river and estuary under my belt and have done the relevant RYA courses for coastal.
I have asked a surveyor to come down and do a consult before I do anything.
As a matter of interest, what boat do you have? Have you gone "salty" in it?

regards

 

[coastwise]

NEIL - Y......

What was your connection with the William Mccan? Was it when Henry Irving was running her out of the Humber? My brother helped get her down from the Faroes when Henry first got her, & we both helped try to get her off Donna Nook without leaving too much of her keel behind after crew taken off by helio & towed off by Humber Lifeboat.

Paul

 

[AndieMac]

arthor

You will be able to steer the boat, while under aux. propulsion, with the main helm (running ahead only), providing the OB you purchase has a facility (Mercury call it the co-pilot lever) to hold the (OB) steering solid.

The throttle twist grip should also stay at the position at which you leave it.
By bolting on a good quality aux. spring loaded bracket directly to the 'conventional' transom will certainly make installation simple, but still requires a good amount of effort to lift back up, when dealing with the weight of a 9.9 or 15 hp.(leaning over at arkward angles).