Losing weight

Ruffles

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When the guys popped our old Moody 31 back in the other week they happened to mention that the lift was showing her as weighing a wopping 5.7 tonnes. According to Moody she came into this world at 4.53 tonnes. So apparently she's roughly 1.2 tonnes overweight.

I reckon water and fuel comes in around 200kg.
Inflatable 30kg
Life raft 30kg
Sails 50kg?
Large bag of life jackets etc 30kg
Ropes, sheets and fenders 50kg
There's really not much junk aboard. It all went home last year. Total for all the above, say half a tonne.

So where's the extra 3/4 ton or are these boat lifts very inaccurate? Could there be gold bullion concealed in the bilge somewhere?
 

Fr J Hackett

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Travel hoist weigh load cells are not that accurate, the boat will have adsorbed some water over the years, what about anchor and chain?
 

Ruffles

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[ QUOTE ]
Have you had to repaint the waterline since you bought her?

[/ QUOTE ]

No!

Forgot the anchor. Works out another 50kg. No way there's another 1/2 tonne there. I reckon the lift is way out.

Quick calculation suggests that 1/2 tonne would put the boat 2" lower and the water line is well below the boot top.

Bit disappointed though since I lightened the boat by scraping off three bucketfuls of antifoul over the winter.

AFscrapingBucket.JPG
 

michael_w

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Probably a combination of dodgy uncalibarated load cells on the boat mover and optimistic builders.

According to the brochure, mine weighs 6,593 kg. When weighed completely empty, except for a full tank of diesel; with a calibrated load cell on a single point hoist, she came out at 8,300 kg.
 

flaming

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Sounds about right to me.

Weighing boats is an important part of the handicapping process. To do this you have to strip it using the theory "if you turned the boat upside down and shook it, and it fell out, it must come off."

You would not believe the amount of stuff that this amounts to. On a race boat that we keep as empty as possible this was probably at least 200kg. Absolute pig of a job, at least 5 trolley loads plus all the stuff (sails etc) that hadn't gone back on yet. On a cruising boat with pots/pans, crockery, spare gas bottles, heaters, random spares etc it will be way more.

And then, even with the boat empty almost every boat is heavy. We're dry sailed, not antifouled, and we've actually taken bits off since the boat came out of the factory (furling gear, bow roller etc) and we were still nearly 100kg over "design weight".

A 20 year old boat(?) that's been kept in the water, antifouled, has sails on board, plus cruising "clobber".....

Not in the least suprised.
 

wotayottie

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how do they weigh boats for handicaps then?

incidentally we have a heritage pilot house in the club and that comes in at 10.5 tonnes or thereabouts every lift in / out with a crane and spreader frame.
 

flaming

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I'm not entirely sure, as I wasn't involved in the weighing, just the clearing of the boat, but as I understand it there are a few lifts that are certified by the RORC to do it, but even then it's a bit of a black art as the boat bounces in the slings in anything but an absolute calm, so the measurer has to take a best guess.... But we're only talking for the last few 10s of kilos, not 1/2 ton.
 

Pete7

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Rob, Gosport Boatyard weighed our M31 Mk2 in at 5100 kgs. Like you that's normal cruising mode so full tanks, dinghy, spare anchor + chain, gas and petrol. All spaces under fwd bunks full with sails, spaces under rear cabin berths full of spares + tools and second fridge. Wardrobe has vacuum cleaner and oil radiator. I have already done one ruthless session which found 90m of shore power cables in the bow /forums/images/graemlins/blush.gif there is more to come as SWMBO as stocked the cupboards with enough tins to feed a small army but we are slowly coming up on her marks.

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[ QUOTE ]
"....You would not believe the amount of stuff that this amounts to...."

[/ QUOTE ]

Once sailed with a serious racer who had lightweight twin-wall titanium coffee mugs on board. And he was so serious about the Fastnet Race that the two F18 'hired guns' he brought along had no oilies, and the food box was left ashore.... They were quite fast on the way out; they were a damn sight faster coming back!

Still, he won his class - and the series.

/forums/images/graemlins/wink.gif
 

bbg

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You also have to consider what that 4.53 tonnes meant in the first place. Did it include engine? Mast and rigging? Batteries? Deck gear? Running rigging?

You would be astounded at how much you would be able to take off a boat if you wanted to, and how much it would weigh. As Flaming says, it is a lot more than you think. Charts, books, additional electronic gear and associated wiring - they don't weigh much each, but if you have a few kilos here and there it all adds up.
 

flaming

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[ QUOTE ]
[ QUOTE ]
"....You would not believe the amount of stuff that this amounts to...."

[/ QUOTE ]

Once sailed with a serious racer who had lightweight twin-wall titanium coffee mugs on board. And he was so serious about the Fastnet Race that the two F18 'hired guns' he brought along had no oilies, and the food box was left ashore.... They were quite fast on the way out; they were a damn sight faster coming back!

Still, he won his class - and the series.

/forums/images/graemlins/wink.gif

[/ QUOTE ]

The most absurd weight saving thing I've ever come across on a racing boat is a carbon fibre ensign staff.
 

bbg

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[ QUOTE ]
The most absurd weight saving thing I've ever come across on a racing boat is a carbon fibre ensign staff.

[/ QUOTE ]
That is absurd. Why carry an ensign or a staff while racing? Leave them ashore!
 

flaming

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[ QUOTE ]
[ QUOTE ]
The most absurd weight saving thing I've ever come across on a racing boat is a carbon fibre ensign staff.

[/ QUOTE ]
That is absurd. Why carry an ensign or a staff while racing? Leave them ashore!

[/ QUOTE ]

Exactly!

It is a work of art though...
 

wotayottie

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[ QUOTE ]
[ QUOTE ]
The most absurd weight saving thing I've ever come across on a racing boat is a carbon fibre ensign staff.

[/ QUOTE ]
That is absurd. Why carry an ensign or a staff while racing? Leave them ashore!

[/ QUOTE ]

No (legal) choice if racing out of British waters - have to show an ensign. Suppose you could tie it onto the backstay.

All seems pointless when you could save muchj kore weight by putting the crew on a diet
 

sailduck

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[ QUOTE ]

No (legal) choice if racing out of British waters - have to show an ensign. Suppose you could tie it onto the backstay.


[/ QUOTE ]

Are you sure? Vendee, Volvo and Global Challenge races appear to race with class flags only - no ensign
 

Aeolus_IV

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Weighing for handicap involves the use of a single appropriately sized and certified (by RORC) load cell and a single point lift. The estimated weight of the boat (and lifting bear) has to be within the optimum working load for the cell (it's no good hanging a 1 ton boat off a 50 ton load cell). The additional gear used to hoist the boat (frame, strops, shackles etc) are weighed separately and this is deducted from the load cell weight. Et viola .... One weighed boat, not that complex at the end of the day.

Many of the hoists in marinas have two load cells attached to the lifting strops/mechanisms, but you cannot simply add these weight together to get the weight of the boat. It is true that they are likely to be inaccurate, and from the point of safety (they are there to avoid overloading the hoist) they are probably pessimistic about the actual weight. However, if the strops are not vertically supporting the boat then the true weight is not apparent as it is only a component of the vector force the strop is taking.

Jeff.
 
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