Tarquin Trader

[Gludy]

Re: Am i going worng somewhere?

Mike
I think you have a point - in practice there are almost a contious range of hulls going from full displacement to full planing.

However there is in this case a huge difference in hull shape.

The extended keel option places the keel well below the props and the keel can take the weight. They fit legs to dry out... I had checked all that.



<hr width=100% size=1>Paul

 

[Deleted User YDKXO]

Re: Questions on your analysis gludy

I think Gludy is going through the process of self delusion that we all go through whereby we dream up apparently rational reasons to justify the entirely irrational desire to purchase a new boat. Gludy wants a new boat and he fancies a Trader. Nothing wrong with that

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[Newbroom]

Re: Am i going worng somewhere?

Yes of course the fuel consuption increases then. the point was that modern designs and engines gets the boat over the hump sooner and quicker than hull designs of only a few years ago.
Fitting stabilisers on a P60 would alter the charachteristics of the boat and I think the writer said it tongue in cheek. Like I said why compare a Volvo with a Ferrari. Would anybody normally consider fitting a tow bar for their caravan to the Ferrari.

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[Gludy]

Re: Am i going worng somewhere?

Yep, it was tongue in cheeck and a theoretical point in any event. I am doing a bit of leg pulling there.

The issue was whether hull design effect comfort or if comfort is just down to speed regardless of hull design.


<hr width=100% size=1>Paul

 

[Gludy]

Re: Questions on your analysis gludy

Only 99% right there ... I really am not sure of which one at present ... thats the problem.

<hr width=100% size=1>Paul

 

[Wiggo]

Re: Am i going worng somewhere?

well there's always the small matter of a 50% increase in displacement, and gyro controlled stabilisers, of course...

<hr width=100% size=1>Nihil curo de ista tua stulta superstitione.

 

[KevB]

Re: Questions on your analysis gludy

"many have a very flat fuel consumption and so consume as much at 18 knots as they do at 25 knots."

Stop fooling yourself, that statement is complete rubbish.

Here are fuel figures for a 42' sports boat with D6's.

Between 20 knots and 28 knots the consumption more than doubles.

REVS. KNOTS TRIM CONSUMPTION:

500 5 2 20lt/h
1000 7 3 30 lt/h
1500 8 5,5 28 lt/h
2000 12 6,5 48 lt/h
2500 20 7 70 lt/h
3000 28 4 150 lt/h
3500 35 3 155 lt/h
3650 36 3 160 lt/h


<hr width=100% size=1><A target="_blank" HREF=http://static.photobox.co.uk/public/images/45/99/10714599.s.jpg?ch=97&rr=16:00:39>Nirvana</A>

 

[tcm]

Re: Free knots

yep. I spoke to a delivery guy who started discussing the strategy of each 50 extra revs on a uk-med trip, (he suggested 1650 on ours btw). Made me realise how there are no free knots.

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[jfm]

ah but

But kev you are quoting gph figures. What matters in this context is mpg. The consumption curve is somewhat flattish, though not totally flat

On your data, if 20kts is Xmpg then 36 knots is 0.78mpg. (Which is an excellent excuse for blamming around imho)

Also 8 knots is precisely X mpg too, so that seems to suggest no point in displacement speeds. Hmmm

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[KevB]

Re: ah but

Oh no no. It's say consumption and that it's almost flat between given speeds. Where as in fact there is a huge difference in consumption between 18-25knots.

And as a % there is a huge difference in mpg between those speeds.

<hr width=100% size=1><A target="_blank" HREF=http://static.photobox.co.uk/public/images/45/99/10714599.s.jpg?ch=97&rr=16:00:39>Nirvana</A><P ID="edit"><FONT SIZE=-1>Edited by KevB on 24/11/2004 10:24 (server time).</FONT></P>

 

[Gludy]

Re: Questions on your analysis gludy

It very much depends on the boat. mI did not say all, just many and that is true.

However even using your own figures and working out consumption as litres per mile (real consumption)
There is very little difference on that boat between consumption at 12 knots and that at 20 knots.

At 12 knots you are using 4 litres per mile.
at 20 knots you are using 3.5 litres per mile .... at almost double the speed.

<hr width=100% size=1>Paul

 

[Gludy]

Re: ah but

The whole point that i was making has been proven by your figures and there are free knots tc, - you are applying too simplistic a view to it.
Its actually cheaper on your figures to travel at 20 knots than travel at 12 knots.

With many bigger boats, once over the hump the mpg can be very flat. However going above the cruising speed on a planing boat can cost a lot, so the flatness is only up to crusing speed, not to top speed.

I liked the fact that the very figures you provided show:-
1. Tcm and is free knots point is incorrect.
2. It proves the poor fuel consumption that you get from a planing boat when in displacement mode!!!

These were my very points and so I hope you now agree with them .. that is unless you wish to dispute the source of the figures ... yourself?

Do you now agree?


<hr width=100% size=1>Paul

 

[KevB]

Re: Questions on your analysis gludy

But surely that throws your hump theory out of the window. 12 knots is on the hump where as 20 is planing? Can't have it all ways.

And in your words "There is very little difference "
<hr width=100% size=1><A target="_blank" HREF=http://static.photobox.co.uk/public/images/45/99/10714599.s.jpg?ch=97&rr=16:00:39>Nirvana</A>

 

[Gludy]

Re: Questions on your analysis gludy

No - please read this thread.

I claimed that a planing boat just before the hump was inefficient on fuel and it actually uses less once past the hump.
Your figures prove that.

I claimed that many boats have very flat fuel consumption figures once past the hump - your figures prove that.

I have now added that if you take a planing boat that last bit over its natural cruising speed limit, then you pay heavilty for it in fuel ...
your figures also show that.

Your figures laso prove tcm,wrong - he jumped at your figures without looking into them claiming there were no free knots but your figures showed that there were free knots ...

Do you accept the above as factual or not?


<hr width=100% size=1>Paul

 

[Gludy]

Fleming 55 Fuel Consumption Figures

I have just established:-
At 8 knots 4.88 mpg ( 2 engines, even less on one engine, probably 8mpg)
At 15.5 knots 0.6mpg


So the crossover point on the Fleming with my Squadron is about 15.5 knots.

If I bought a Fleming I could travel up to speeds of 15.5 knots all day and use no more fuel than I use on my Squadron planing at 25knots.

This figure tallies with the bigger trader that crosses over at about 18 knots.

Of course the longer the boat the higher this cross over speed.

<hr width=100% size=1>Paul

 

[tcm]

Re: yes yes, i agree

silly me! Those daft buggers going down to the med at 10 knots to save fuel must be just stupid, after all. perhaps their fuel guages were all wrong. And likewise the royal navy limiting its ships to 12knots on exercise to conserve fuel - that's stupid as well. It's amazing what you can learn here innit?

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[jfm]

I\'m comnfused now

Gludy you say "If I bought a Fleming I could travel up to speeds of 15.5 knots all day and use no more fuel than I use on my Squadron planing at 25knots."

Is that supposed to be good?

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[kimhollamby]

We\'ve had several on cruises in company...

...over the years, loads of 41+2s, a couple of 44s and a 47.

I get the impression that most owners of these models sooner or later settle down to quite modest cruising speeds, no higher than mid-teens -- and often they rumble along like a veritable cruise liner at 10 knots or so -- with so much deck space you literally can promenade in flatter water and go for a stroll, in wetter weather you are generally better off downstairs because all that beamy accommodation gives a broad bow and a splashy ride.

Aft cabin format and voluminous hull does mean that crew have some mountaineering to do, although I expect the latest versions with the stairs on the back are a lot easier provided no tender in the way and provided that the bathing platform runs well out to the edge (not seen one of these in action). If you are used to an aft cockpit this will be quite a change.

I know I keep pecking away at this one on your threads but I genuinely don't think you buy a semi-displacement hull for fuel efficiency -- but I do agree you buy it because it generally works okay at whatever throttle settings you make from displacement to high teens. 20-knots plus and some are definitely better than others.

In terms of build, I've personally never heard of one sinking and they generally seem fairly robust. Stainless steel work on the early ones particularly was not great -- a trait shared with many Taiwanese builds of the period. But whichever way you look at it you get a hell of a lot of boat for the money and the entertaining space is, as highlighted elsewhere on this forum, virtually unmatched length for length anywhere else. From memory you can also get all around the engines even on a 61-series equipped 41+2, which I personally like. Biggest bonus probably, compared to most boats of Taiwanese origin, is that these have been going long enough that they have a recognised market value.

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[burgundyben]

Re: Fleming 55 Fuel Consumption Figures

what a complete load of arse, 4.88 mpg, christ alive,

4.887657 I think you'll find you bloody anal retentive

wind? waves? tide?

its a bloody great stink pot mobo specifically built for mindless enjoyment and decadent drunken blamming about....

not a comfort/economy save the bloody trees campaign

(deep breath and relax)

<hr width=100% size=1>My house is for sale, 2 beds, Hamble.

 

[KevB]

Re: Questions on your analysis gludy

"Do you accept the above as factual or not?

Er, no. Not really. Everything is in context., or out of it in your case

Firstly: on the hump topic you said...

"Secondly you cannot say go at 13 knots, just before the hump without having major fule consumption

Then you said "There is very little difference on that boat between consumption at 12 knots and that at 20 knots."

So which is it?

Secondly: you say "I claimed that many boats have very flat fuel consumption figures once past the hump - your figures prove that.

No they dont. They show that in the area of where most planing boats are used 20-28knots, fuel consumption doubles. You only pick the bits that make your argument. I'd guess the difference in the trtaders consumption between 18 and 24.6 knots was flatter than before it?

Thirdly : you say "I have now added that if you take a planing boat that last bit over its natural cruising speed limit, then you pay heavilty for it in fuel ...
your figures also show that."

Yes the figures prove that but what's your point? Isn't that the same if not MUCH worse with a semi displacement?

Oh, and points two and three contradict themselves.




<hr width=100% size=1><A target="_blank" HREF=http://static.photobox.co.uk/public/images/45/99/10714599.s.jpg?ch=97&rr=16:00:39>Nirvana</A><P ID="edit"><FONT SIZE=-1>Edited by KevB on 24/11/2004 11:19 (server time).</FONT></P>