A New Chapter - a new Marlow

[Gludy]

Today I ordered my new Marlow - I hope is the start of a very happy experience and turning of a new chapter as it were.

Demand is such that theyare just opening up a new production line for the hull size so with a fair wind I may get here about September 2008. I will know my slot in a few days.

Still have a few hurdles from the past to jump before the past is over but I am like a new kid with a new toy listing all the options and changes that we would like. We aim to spend a long time on this boat - almost a second home.

I know I am only one of a fair number of UK Marlow owners in the pipeline.

Anyway - just thought i would tell you all, who have been of such help over the last 18 monmths, that a new chapter has started.

 

[rickp]

Congrats Paul /forums/images/graemlins/smile.gif We will want to see LOTS of build photos as always.

Cheers,
Rick

 

[Gludy]

Marlow have their own VIp sort of hotel on the site where owners can go and watch their boats being built as well as tour the factory - so there will be lots of build piccies.

One of the things I am wrestling with is the third engine.
I have ordered Cat18s @1015hp each and the trolling option with them.

I plan to do a lot of distance work at about 9 knots - she takes 3500 USA gallons (I never want to think of that bill when I fill up after November 2008!!!).
It seems that 120hp of thrust will project her at just over 9 knots and I think the third engine is rated about 340 or 240 hp - so am I better off having the third engine for this low speed work at say 50% load or will the cats be OK given that this engine does have very good low speed performance?
I can change the spec a lot at present and this is one subject of about 100 I am currently tackling.
I will of course be getting info from the factory on it but that does not stop me doing my own investigation on almost everything.

 

[gandy]

Would the third engine drive the main propellers, or a third one?

 

[Gludy]

It drives it own prop - in the centre.
This means that unless the other props are locked they will impose extra drag but apparantly these 'engine pods' do push it along about 9 knots using about 120 hp.

It means that the main engines are not used at low revs for long periods - it may be better fuel consumption but I am not sure. Its also great as a get you home engine should others fail. However the third prop itself must impose drag in itself.

I know the Marlow in Scotland has a engine pod and has used a fethered prop for the third engine. That marlow is a much smaller Marlow so i cannot simply transfer all the lessons.

 

[MapisM]

For such kind of usage, I'd consider using A rating engines and forget the trolling option.

 

[Gludy]

Can you explain A rating engines please?

 

[Hurricane]

There must be a better way of handling an "undriven" prop.
In the past, I've run on one engine at a time but the forces imposed on the undriven engine are quite large.

How about variable pitch props?
Do these allow you to feather them?

This subject need some radical (as they put it these days "out of the box") thinking.
Ther must be a way of doint it - just think of the effeciency if you could run on the third engine without creating drag from the main props - and likewise the other way round.

 

[Gludy]

I totally agree but there is not that much out of the box thinking actually done on the subject.

Marlow say they fit the third engine to cope with long journeys through canals and Inter coastal waterways etc. Fuel is so cheap over there that the reason seems to be to spare the main engines long low running hours full stop.

I do not what it is about me but I keep asking questions that suppliers cannoit answer. I have the yacht control people coming back to me trying to get a proper answer to the radio engine control security question. On this subject of the third engine I do not know the answers but find that by questioning I learn.

I am not even sure what the trolling mode is on the CAT 18's yet.

One of the advantages of a long boat is the naturally high displacement speed for long journeys. I am even going to be tempted to cross the Atlantic in this boat - a feat that would be done without much thought by many brave souls but would require months of prep and thought before I ever did it. It is rated for that sort of work and has a lot of redundancy built in.

 

[jfm]

Many congrats Gludy. Hope all goes well

I think the third engine makes sense IF they can fit a sail-boat style feathered prop (can they?). Otherwise the drag from the unused prop when running fast on the main engines will be a pita. But if they can get the drag small, it would be good from engineering and noise standpoint to do long 9-knot passages on the small engine

I would think A-rated main engines will be way too heavy

Are you having it MCA coded? (just an idea... nowt to do with chartering...)

 

[Gludy]

yes the third prop can be feathered like a sailing prop.

The boat is MCA coded and many other codes:-
[ QUOTE ]
We submitted Rebel Yell and our entire lineups' design review to Lloyds Germanischer Classification Society and received CE certification by Lloyd's Register Quality Assurance for Category A (Ocean). Lloyds offers several categories of certification and each manufacturer can decide which category standards to build to. This category can be from D, Sheltered Waters to A, Ocean. We chose the toughest one offered, A, Ocean. In this testing and certification, many difficult hurdles must be cleared. They range from safety of crew and passengers in inclement weather to stability, unaided by mechanical devices. Hardware like propeller shafting, rudder shafting must be far larger than normally seen. Rebel Yell has 3.5” Aquamet HS22 shafting for 950 shaft horsepower. Typically, we see 2.5” shafting in similar applications, perhaps 2.75” in a far lesser alloy. 22HS signifies the best alloy (22) and then we add an even higher spec known as “HS” signifying “high strength”.

[/ QUOTE ]

Rebel Yell is the prototype 72 ELR Marlow. I have had a sea trail on her.

 

[andyball]

if you need the third engine to do 9knots, and that takes 120hp, don't waste money & space on a 250hp.

spec a motor that is economical at 120, say a lightly turbo'd smallish 4 cyl.


I would love to be surprised, but I can't see the cat 18's being anything like as economical as you'd hope at 9 knots - nothing near the efficiency of the third small one., but even for a 72, 9 may be a bit high for super-economy - depends on the lwl and hull characteristics of course.


But what is it you want? the even-more security of a get you home err 3rd engine? If so, decision made - get one, but no way you need 250hp as above.


Is it for the ability to troll or potter at below expected tickover speeds on woo, twin 1000's? If so, can likely be adeuqately dealt with via trolling options, whatever they are? could be a gbox valve thing allowing slow shaft speed; probably that combined with a 'slow' engine mode I'd imagine. in any event, you might think nice slow two-engine manoeuvring speeds for tricky berths rather handy? so praps the trolling options better than a dandy slow-speed third engine.

Or is it for economy? would the savings ever pay for a third lump? and do you care given the overall boat price?

or for heeeuuuuge range maybe? but do you need more than the twins at 9knots & whatever fuel tanks can provide?


Praps no third engine, 700's not 1000's and lots of spare cash for fuel & loveliness is a better deal?

 

[andyball]

re props tho - what do they fit?

a folding one ( maybe why they need so much power to get an effective 120hp? /forums/images/graemlins/smile.gif or a variable-pitch one ( more $$'s, but superb for getting max range/economy whatever the circs.

 

[peterg]

Caterpillar electronic trolling controller /forums/images/graemlins/wink.gif

 

[MapisM]

A rating engines are for unrestricted continuous usage. You'll find a summary here.
I only partially agree with jfm, 'course A rating engines are much heavier for a given power, but they can be reliably run at rated power for much longer.
And in practice, if you think about when you'll be going to use 2 thousands HP on that kind of boat, the answer is simple: never. Well, maybe just to give it a spin a few times each season, and maybe for less than 10' each time.
In any case, if you'd really want to use all that power for continuous operation, you just couldn't do that without putting at risk the engines.
The engines you're mentioning are in fact E-rated ("high performance").
...even before digging into details, you can imagine that between E and A there are steps in between...! /forums/images/graemlins/grin.gif
For such long range vessel, B rating is the rock bottom imho.
PS: it's surprising that the builder didn't mention that, btw.

 

[andyball]

according to cat's marine spec sheet wizard , you can Arate em, if drop rpm to 1800 & 454 bhp output.

the specs shown there actually suggest quite good ( yep I'm surprised a bit) efficiency at 600rpm ( assuming these are accurate ) & show an output of 97bhb @ 600 rpm


tho hmm wait, the A rated one shoves out way less power at 600rpm, so obviously something other than just an rpm reduction - less boost praps? so forget most of above - doh!


graphs for Erated C18 show prop-demand-data ( ooer) down to err 18bhp and just over a gall an hour each engine.


Ohh figures, figures - get a third A rated engine for crossing oceans Paul, and C12's or 18's for blasting around.

 

[DAKA]

One way to eliminate the prop drag issue on all three props is to fit a two speed gear box to the third engine.

Speed gear 1 is for in the harbour at 9 knots where a bit of drag for a few miles is irrelevant.

speed gear 2 is for when you need to make that cil or just stay ahead of that nasty weather system ( ie........all the time) and an extra 240 hp will afford an extra 3 knots. /forums/images/graemlins/laugh.gif

Sorry I really have difficulty thinking how anyone could sit on a 20 knot boat and only cruise at 9 knots /forums/images/graemlins/confused.gif

Most Raggies leave their engines on when going further than 20 miles !

How often did you cruise under 10 knots on Ocean Heap, you would have to cover 60 000 miles at 9 knots to pay for the extra installation costs, couldnt you just fit an extra tank for long range, a bespoke flexible tank in the guest cabin ?

 

[Deleted User YDKXO]

Interesting conundrum. Does the 3rd engine have a completely separate fuel system in which case you have an additional redundancy in the drive system which might make it worth having the 3rd engine? IMHO, you should talk direct to Cat to see what they say about running the C18's for long periods at low rpm and whether they see their trolling option as something to be used for long or short periods

 

[Hurricane]

Daka

[ QUOTE ]
Sorry I really have difficulty thinking how anyone could sit on a 20 knot boat and only cruise at 9 knots

[/ QUOTE ]

Here's an example that happened to us.

Left St Malo on the last lock (06:00 from memory)
Needed fuel for a channel crossing.
Decided on Guernsey cos the fuel is cheap.
Have a look at the tides - you cant get onto the fuel berth until around midday so what was the point of rushing along at 20 knots just to get there and wait.
So we just "toddled" along at about 8 knots enjoying the cruise to arrive about half an hour before the tide let us onto the fuel berth.
Here's a good reason - dont you think?

Paul
I helped a guy with a Manhattan 64 to berth at our marina the other day.
After I had a chat with him - his boat was fitted with the Cat engines and trolling system you talk about. He said that they were great for close quarter manouvering. You know that sudden burst that you get when you put an engine into gear - the Cats make this much smoother by redusing the revs at slow speeds - he is a professional skipper and said that he liked this feature.
However, I dont think the trolling system will do much else for you - I dont think you would use it on the move - maybe others have experience.

Mike

 

[DAKA]

[ QUOTE ]
Daka

[ QUOTE ]
Sorry I really have difficulty thinking how anyone could sit on a 20 knot boat and only cruise at 9 knots

[/ QUOTE ]

Here's an example that happened to us.

Left St Malo on the last lock (06:00 from memory)
Needed fuel for a channel crossing.
Decided on Guernsey cos the fuel is cheap.
Have a look at the tides - you cant get onto the fuel berth until around midday so what was the point of rushing along at 20 knots just to get there and wait.
So we just "toddled" along at about 8 knots enjoying the cruise to arrive about half an hour before the tide let us onto the fuel berth.
Here's a good reason - dont you think?

.

Mike

[/ QUOTE ]

Now please understand I am not criticising but

You did that to save £200 of duty ( as it would have gone to the FRENCH very admirable) but a saving of £200 duty and £50 of economic cruising speed saving can not justify £35 000 - £50 000 spare engine/gear box/prop/service costs/installation costs/extra drag costs when main engines are in use).

Spending £5000 on an extended fuel tank makes better sense.

Pete

PS
I would have gone like the wind and made St Helier ( fuel outside cil), extra fuel used £15 and swmbo happy to come back next year /forums/images/graemlins/wink.gif