What does my boat weigh?

[--ice--]

Ensure any trailer you buy is fully adjustable, the balance of your boat & outboard maybe similar to others but remember the nose weight of trailer mustn't exceed 75kg, ideally between 50 and 75kg, you need to be able to adjust the position of the axle relative to the boat sitting on the chassis of the boat.

At the risk of going ot, I have used old caravan chassis to move boats, a shetland 535 and a Hurley Alacrity were both purchased recently on old caravan chassis.

 

[Leonidas]

I remind myself that this is the Practical boat owners' forum....

Quite right! what's wrong using a sping scale at the end of the hook of a hoist and lift the boat??

 

[Mirror Painter]

Thank you.

Thanks again for all the information - and a few laughs too.

One or two readers may think I was labouring the question but I know nothing about trailers and have never towed anything. Until this year I had never owned a boat and I want the trailer experience to be smoother, safer and less dramatic that the first time I took the boat out

Expect a further post once a suitable trailer is in my sights...

 

[Cap'n Creosote]

In the nineteen sixties, PBO published an article on how to weigh your boat with a car engine valve spring!

The principle as I recollect it, was to time the oscillations of a spring of known proportions.
The boat was brought end on to a jetty and attached by means of clamps and bits of wood to the jetty.
The spring was somehow fixed horizontally between these bits of wood so that it would expand and contract as the boat tried to move fore/aft.

In calm water/air, they said, if the boat is given a push it will oscillate at a frequency proportionally related to it's weight. And published a graph of times and weights and known valve springs.

I wonder if PBO still have that in their archives.

 

[Csail]

This thread is just silly.......fully fuel car and boat and take it to be weighed at local quarry.

 

[Greenheart]

Don't listen to Csail...obviously he's a cynic. The car-component was an interesting alternative thought. Plus, surely dragging one's boat to the weighbridge requires that you already know approximately what it weighs, for the trailer??

I can't help thinking that if you were to put a sling around the boat, still in the water, and rigged up a few scaffolding poles on the jetty beside it...and arranged a secure fulcrum...then, according to the length of the poles on the jetty side of the fulcrum...(which could be set up to be eg. ten times longer than their length overhanging the boat...

...then, if you hung two full 20-litre jerrycans on the jetty end, they'd lift exactly 400 kilos on the boat end...so, you'd keep adding known quantities of water until the boat lifted out...then multiply the litres of water by ten, for the weight in kilos. Eureka!

Yeah, I just read all of that back to myself... Best borrow a Huey helicopter and take the boat to the weigh-bridge...

 

[Lakesailor]

Much easier is to mark the waterline on the inside of the hull. Then fill the boat with water using 2 gallon buckets (or use a hose with a know GPM flow).
When the inside of the boat is full to the waterline mark you've made then you know how much water it displaced and can calculate the weight. The thickness of the grp reduces the true amount of water displaced, but that should hardly matter.
Ignore the outside water level now as this will be a lot higher with all that water inside.

 

[jimmcgee]

no no no you's are doing it all wrong!!!

get a set of these http://www.americanweigh.com/produc...ucts_id=244&osCsid=miu7js5fb0qlq48360lelpc9c0

set the boat on them at low tide , then when the tide is out you read the weight!

siiimmplessss

 

[Leonidas]

I can't help thinking that if you were to put a sling around the boat, still in the water, and rigged up a few scaffolding poles on the jetty beside it...and arranged a secure fulcrum...then, according to the length of the poles on the jetty side of the fulcrum...(which could be set up to be eg. ten times longer than their length overhanging the boat...

...then, if you hung two full 20-litre jerrycans on the jetty end, they'd lift exactly 400 kilos on the boat end...so, you'd keep adding known quantities of water until the boat lifted out...then multiply the litres of water by ten, for the weight in kilos. Eureka! .

Dos moi pou sto kai kino tin ghi !: Archimedes on the principle of levers

 

[Greenheart]

Damn it, I thought that was my idea!!

 

[Leonidas]

What about the volume occupied by the internal structure , double bottom, lockers or any buoyancy voids???

 

[Lakesailor]

Knock them out.

 

[oldharry]

This thread is just silly.......fully fuel car and boat and take it to be weighed at local quarry.

How? he hasnt got a trailer, and wants to know what size trailer to buy.

'Total train weight of loaded vehicle and trailer' is what plod would look at, and is specified by all car manufacturers. Exceed that at your peril as they will issue a 'stop' notice for an overloaded vehicle, and you then have all the expense of retrieving boat and trailer from wherever they stopped you. It has happened - but never to me in 40 years of towing boats, caravans and other things around, and never even been stopped or checked. Down here on the S coast local Plod entertain themselves regularly by stopping all caravans and towed boats and doing full roadworthiness and load checks. Its both surprising and rather alarming, the number the find with seriously dangerous faults as well as being overloaded. Same in France where Le Plod thoroughly enjoy stopping and hassling 'overloaded' GB registered cars as it is one of the few things they can get a succesful 'result' for instant (large) fines. (BiL was French Plod - now retired, and he delighted in telling me all about it before checking my heavily loaded car on a visit - s*d!)

 

[Jeepster]

I hope that you may be able to offer guidance on calculating the weight of my boat.

I ask because I am considering the purchase of a trailer. Said trailer is likely to be used twice per year for winter maintenance. That is, to transport the boat from river mooring to house driveway and back again.

The boat spec's are thought to be as follows:

Marina 16GT
LOA - 4.96m
Beam - 2.09m
Draft - 0.16m
Speed - 30knots with 50hp.

Plus there should be a picture of her at the top left of my post!


Thank you.

I realise this is an old thread, but anyone else wishing to know information about the Marina 16 GT, or any other Marina boat, can now find it on my Marina Boats Ltd page on facebook, along with the detailed history of the company: https://www.facebook.com/Marina-Boats-Ltd-170763240209124/
Regards
Alf Beharie

 

[ningcompoop]

398Kg! Ta-dah!

 

[KellysEye]

Bear in mind it's not just the weight of the boat but also what is in it. For example out steel boat weighed 12 tons and 15 tons fully loaded generator, water, diesel, food, tools etc. Obviously yours won't be anywhere close to that but do take it into account.

 

[Daydream believer]

Bear in mind it's not just the weight of the boat but also what is in it. For example our steel boat weighed 12 tons and 15 tons fully loaded generator, water, diesel, food, tools etc. Obviously yours won't be anywhere close to that but do take it into account.

Was that your calculation or did you get it from Brent Swain?

 

[fredrussell]

Apols, posted in error.

 

[Jeepster]

398Kg! Ta-dah!

Wrong!...It's 393.8kg for the empty boat, then on top of that you have to add the weight of everything else, such as seats, fuel tanks, fuel, outboard, controls, etc, etc...It will be a lot closer to 500kg by then!

 

[KellysEye]

>Was that your calculation or did you get it from Brent Swain?

The displacement was in the builders details, a Dutch company Tak Yachtbouw and the total displacement is measured when you are lifted out.