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Fuel Consumption

Hockham Admiral

By Hockham Admiral
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littlesprite
littlesprite

I've largely tried to stay out of this but what the hell, in for a penny in for pound.   I see two different arguments here, one about speed and one about engine revs, I've never agreed with the spe

Hockham Admiral
Hockham Admiral

I guess I ought to have said that we are retired and so don't restrict ourselves to a set itinerary when we go out. So we're seldom in a hurry to get anywhere and in the long Summer days I like to be

donnygeoff
donnygeoff

i never monitor my fuel consumption either.... Clive tells me off for not using enough.... I just potter about, tootle up and down and always get some fuel deposit back for a meal on the way home.

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Guest

Guest

Posted
Posted

Is there an "Hours per gallon" measurer one can get? if so is it hideously expensive?

 

New marine electronics are being introduced all the time, so I may be out of date with my understanding, but when I bought that, the only type available was chartplotters with the accessory add on "fuel flow sensors".

 

At that time they only worked for petrol, because diesels have spill pipes that return fuel to the tank and would give a false reading.

 

The flow sensor add on was a Navman 2100 that was compatible with my Northstar 657 plotter. I was trying to google the price of it and I came across an interesting discussion on them on a US boating forum:

 

http://www.thehulltruth.com/boating-forum/21608-navman-2100-fuel-flow-meter.html

 

 

Strowager ,    can I have a link to your gadget as well.    I looked up a similar version at it was over £4,000.     Need to go and lie down if it that expensive.

 

I quite agree Hylander, I'd expect to get a boat for that much dosh.

 

My Navstar chartplotter/GPS/depthfinder was about £300 with the fuel sensor, but that was about 6 years ago, and I don't know what the latest equivalents are, but I would imagine around the same price, as this sort of thing gets slightly cheaper, like TVs, phones and computers.

 

Here's a link to my gear, described as "legacy" products now !  :)

 

http://www.navmanmarine.net/navman-chartplotters.html

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Guest

Posted
Posted

:party2:Ha ha  ......sorry folks but you are all getting it wrong ....switch off the techy stuff .....fill up when nearly empty ....slow down and chill ......and best of all Enjoy

 

 

Finny

 

 

I can appreciate both schools of thought on technology Finny.  :)

 

I like a few toys, but then so much other stuff comes along and I then retreat to the background myself.

 

I was the first in with computers, mobile phones, and GPS's, but the relentless evolution to get maximum consumer spending quickly gets me to saturation level.

 

Despite my veneer of high tec stuff, I'm still basically a muck and bullets man. :)

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Hi Strowager,

 

So you had a mobile brick as well, I still have mine somewhere a Phillips complete with a mag mount aerial. Our first computer was a BBC with a Torch dual floppy 5 1/4 inch drive, happy but slow computing times.  

 

Regards

Alan

 

 

Yes, I definitely have the tea shirt as well there Alan.

 

I had a Motorola "brick" back in the analogue days when the Voda line rental alone was £17 a month, and calls at 50p min.

 

I had a dedicated carphone as well, "cloned" onto the same number, and had to remember to never switch both on at the same time.

 

My PC evolution was  ZX81 - Spectrum - BBC - Amstrad PC - then PC clones.

 

At work I started off with CPM machines, an RM380Z, then a "Hinet" networked system. The hard disk in it was an 8" winchester, with the enormous capacity (then) of 20 Megabytes, (yes mBytes), and that alone cost £800, back in the 1980's.

 

Strange to think that you can now buy a 128 Gigabyte USB pen for about £30.  (Which has two thousand five hundred times as much storage capacity, and fits in a top pocket).....  :shock:

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ExUserGone

ExUserGone

Posted
Posted

 

Tha fact remains though, that "speed over ground" is directly proportional to how much damage a moving boat will inflict on a moored boat or stationary riverside structure.

Back on this old chesnut, yes I admit a slow collision will do less damage and injury than a fast collision will, but the boat thats moving at a speed that gives good control will not have the collision in the first place so reducing the damage and injury to zero, obviously enforcement is very hard to do in knots (if not almost impossible).

Back on the gt.ouse I once had an EA patrol boat coming towards me with a radar gun shouting at me to slow down, I had to laugh at them as they must have clocked me at twice the speed.

Have also seen BA patrol boats mooring at reedham only to be spun straight round as they did it the wrong way for the tide.

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SPEEDTRIPLE

SPEEDTRIPLE

Posted
Posted

Personally, i think this will only lead to on the spot fines, and other such rubbish.

 

The police set a precedent with their gatso cameras (now no longer usable due to PROVED inacurracy readings), and the BA will only follow suit.

 

On the road, speed is always a constant on stationary tarmac which is what you`re travelling on, whereas the only constant on a river is tidal movement, which can also be affected by climate conditions. Therefore, you`ll never get an accurate reading. Add to that the operator being in a moving boat, and hey presto, lots of revinue for the BA to spend on yet more manufactured jobs for university students.

 

Keep speed cameras off the broads i say, and go back to having rangers do what they were originally there for, and that`s patrolling the rivers properly.

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Guest

Guest

Posted
Posted

We seem to have gone round in a circle with this thread.

 

The pertinent points remain.

 

The BA has to have a workable method to be able to prosecute blatant speeders or there will be an increase in boats going faster and  faster and getting away without being able to be prosecuted.

 

The only practical way to maximise BA Ranger's time in monitoring speed appears to be by the use of static radar guns.

 

Since toll payers are paying their wages, it's in all our interests for the task to be carried out as efficiently and effectively as possible.

 

If anyone can suggest a practical alternative method to radar guns for proving excessive speed that will stand up in court, I'm sure the BA would be very grateful to hear it.

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Guest

Guest

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Confused - Using your formula I get a max hull speed of 8:6  However I have seen more than that (using GPS) on flat calm waters at slack water :???:

 

The formula is for true displacement hulls only.

 

If you can get appreciably more speed than the theoretical maximum, then you may have a planing or semi-displacment hull design instead. They can exceed displacement speeds but with a huge wash till they accelerate through the transition stage and rise up over "the hump" and truly plane, at about 16 to 20 knots.

 

What make and model is your hull, and what horsepower is you engine ?

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Guest

Guest

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Posted

:dance Er of course it wasn't through horning !!

 

The GPS displays in mph

 

The make is a Jack Powles 40 (Aka Star Supreme class and/or Bourne 40 hull)

 

Engine is 50hp shaft drive with a 4 x blade prop

 

Assuming a watereline length of about 38ft, the 1.4 constant gives you a maximum displacement hull speed of 8.6 knots, as you had calculated. This is when your bow wave trough reaches the stern, and your boat starts to tilt backwards, trying to climb over it's own bow wave.

 

This  converts to 9.9 mph.

 

The 50 hp engine, well propped, is ample for that size of hull at displacement speed, so you could push further into the "transition" phase, but with a greatly increased wash and much reduced fuel economy.

 

How much faster than 9.9mph was showing on the GPS ?

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Guest

Guest

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Posted

Errr, I thought it was about throttle versus fuel consumption, Strow?   :naughty:  :naughty:  :naughty:

 

 

Quite true John.

 

What I meant was that it then widened into how to monitor one's speed, then went off at a tangent into a BA knocking session about radar guns (twice).

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JennyMorgan

JennyMorgan

Posted
Posted

I understand, from an authoritative source, that fixed notice penalties are NOT just around the corner. Apparently it's accepted that it would destroy the generally good relationship between the Rangers and the Rhond Dwellers. In this instance I tend to believe the horse's mouth on this one.

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Warp

Warp

Posted
Posted

Attached is a chart of hull speeds mapped to mph.

 

If you locate your waterline length on the bottom and scan up then green lines should roughly correspond to low wash and red ones to high wash.

 

Hull speed is not an absolute limit as canoes surfboards dinghies etc regularly prove. It just means that you are moving into a planning mode (loads of boats can exceed their hull speed even sailing boats).

HullSpeeds.pdf

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