How does one find the weight of a ferro yacht ?????

[bandita]

We have a 36ft 11ft 6in by 5ft 6in ferro yacht believed to be a Hartley Tahitian. Its waterline length is 32ftish.
We are planning to have it transported from an inland yard to a coastal one for launching.
Its hull shape is hourglass and has a hollow keel and the skin is around threequarters of an inch thick.
Others have told us between 12 and 21 tons but the crane operators prefer us to be a lot more accurate.
I know 1 cubic yard = a ton of water and lxbxd = area. Nothing is straight.
The closest I have got to was around 16tons. Im more focusing on other boat owners who may have similar sized boats and know their weight....
Any ideas?????

 

[Aeolus]

Don't know if this will help but a tube with a diameter of 11'6" (3.5 m) and 36' (11m) long has a surface area of approximately 121 sqm. If the boat is half of that tube (cut lengthwise), then its surface area would be 60sqm. If the thickness is .75" (approx 2cm), then the volume of concrete would be approx 1.2 cubic metres, at say 2400 Kg per cubic metre = 2900 kg. This ignores the fact that some of that thickness is presumably reinforcement material which might be a bit heavier than concrete.

Now, the boat isn't a tube and I've completely ignored the keel. However, this number suggests that if it is just the bare hull, it is unlikely to be anywhere near 12 tons, let alone 21.

I don't know what a typical 11m yacht would weigh but my 9m GRP yacht weighs about 4 tons fully loaded (incl engine, rig, water, fuel, batteries......)

Best if someone else checks my maths and logic (but on this forum, of course someone will).

 

[bandita]

Thanks for the info. Just found an article The boat they laughed at Max Liberson May 2012 Yatching Monthly. He has a tatty 38ft 14ft 5ft 6in with a smaller keel and the article states that is 16 tons. Our goal is to get it below 15 tons for the lift off crane.
The keel is substantial and I have to include the decks and cockpit.



I think there is a pic???

 

[LittleSister]

I think you won't be able to estimate to the accuracy/confidence the crane driver would want - it depends so much on how it's built, and what it has in it (including ballast, fitting out and kit). I think you may have to weigh it, either by having it lifted with something with an adequate margin of capacity, or jack it up on a couple of gauges or load cells.

A friend built a Hartley designed ferro boat (38' 6" South Seas IIRC) years ago, and it was way over the 'design' weight (still sailed far and wide and had loads of fun, though). I have a vague recollection of 13 1/2 tons or 15 tons (or both!) being mentioned.

 

[pvb]

We have a 36ft 11ft 6in by 5ft 6in ferro yacht believed to be a Hartley Tahitian. Its waterline length is 32ftish.

I can't believe that your boat weighs anything like 16 tons! I'd guess 9-10 tons. There's a 38 ft Hartley Tahitian for sale which says it's 11 tons, see http://ads.boatboss.com/842_Bangkok/31419_Beautiful_38_Sloop_Hartley_Tahitian_lowered_in_price.html

 

[FWB]

A number of ways of guessing this.
Info below from various sources..Classic Boat 134 p77, a Forumite , Internet

Area of immersed mid section x LWL x prismatic coefficient [Cp] Metric units try Cp of .52

LWL /100 cubed xDisplacement Length Ratio. Try DLR of say 360 LWL in feet

LWL x beam x draft x 18 use feet result in pounds divide by 2240 for tons

No info for 1st suggestion
2nd gives about 12 tons
3rd. gives about 14 tons assuming WL beam is 10ft ?

Guesses used for Cp and DLR

3rd example works well for my long keeled gaffer which is 8.5 tons
LWL 26, beam at WL 8 average draft 5 approx figures.


Looking at the picture you posted, the keel seems narrow so maybe not so heavy as in above examples.
All guesstimates anyway !

 

[fluffc]

Has the ballast been put in yet? It would be usual to transport without ballast, and put the ballast into the hollow keel afterwards.

Don't skimp on the crane. Yes, it should be about 16tons - tallies with other ferro boats of a similar size. Very much advise that you overestimate the crane requirements and get one that is rated at over 25tons, noting that the capcaity decreases with how far from the vertical the jib arm is.

Also, and make sure it is one with a measuring facility so you can get a true reading of the hull weight.

 

[fluffc]

My ferro bawley, balasted, of 32' LWL , 13' Beam and 4'6" draft weighed 10½ tons - so I can quite believe a 28 foot boat weighing 16. I'd be worried about a 38ft weighing 11 tons..

 

[bandita]

Cheers everyone. I had mydoubts about it being 21 tons. Thats what the boatyard told me although they wernt there when it arrived about twenty years ago.
It is built really well for a change. It has a dark dense slate gray colour and kills discs and drillbits. Our plan is to have it water ready with all tanks empty and everything movable off. Just to be sure. As long as it is under 15 tons then i am happy. P S The big chunks of wood on the stern were the first things to go!!

 

[malpasman]

Hi

Just a few points to consider,

The transport of a yacht this size will not be a DIY job.

If the yacht width is 11 foot or over, this will be an abnormal load as its over width for UK roads.

How do you propose to lift the structure? will you need a frame so that the strops will not collapse the hull at deck level?

What is the yard surface covered with? If tarmac or loose material, spread plates may have to be used for the outriggers.

How near can the low loader get to be loaded?

Any overhead cables to restrict the lifting height / capacity of the crane?

The lifting capacity of the crane decreases as the reach of the crane increases.

What is the distance to the unloading point and do they have a crane with the lifting capacity.

 

[CAPTAIN FANTASTIC]

Here is my working:

reinforced concrete: 2.8 tonnes per cubic metre; concrete thickness 0.05m
Hull: 12m x 0.05 x 2 (height of sides) x 2 sides = 2.4m3 x 2.8 = 6.72 tonnes; say 6.8 tonnes
Deck: 11.5m x 2m average beam x 0.05 = 1.15m3 x 2.8 = 3.2 tonnes
Total concrete: 6.8 + 3.2 = 10 tonnes

Keel: say 1/3 of yacht weight = 3.3 tonnes

Weight of: engine, mast, rigging, furniture, fittings, deck gear, water, diesel = say 3 tonnes

TOTAL: 10 + 3.3 + 3 = 16.3 tonnes; (assume + or - 10%)

 

[westernman]

The only way to know is to lift it.

The crane will have be able to measure the weight - and stop if it turns out to be too heavy before damaging anything.

However, you will probably have to pay for the lift - even if it never got off the ground. And if it is too heavy it does nothing to solve your problem.

 

[ghostlymoron]

Has the ballast been put in yet? It would be usual to transport without ballast, and put the ballast into the hollow keel afterwards.

Don't skimp on the crane. Yes, it should be about 16tons - tallies with other ferro boats of a similar size. Very much advise that you overestimate the crane requirements and get one that is rated at over 25tons, noting that the capcaity decreases with how far from the vertical the jib arm is.

Also, and make sure it is one with a measuring facility so you can get a true reading of the hull weight.[/ QUOTE]
A 25tonne crane will only lift 25t at 1m radius, 12t at 2m. So you'll need larger than you think.

 

[bandita]

A huge thanks toeveryone.... There is no ballast in the keel contains the water tanks are oval in shape from 5inches to 15inches to 4 at the skeg.
I think that the boat is around the 15 ton mark and it would be wise to empty the boat as much as possible. Any ballast in the vessel has been cast in and covered with epoxy. A small area 3ft square up forward and beneath the stern tube. The rest is hollow and empty. The crane at the leaving point is capable so I will take advice in hand and look for a place with a boat hoist or a substantial crane.
We still have a few months before the boat is in the water but I am starting to work out what needs finishing before, surveys, certificates etc.

You have been a great help!!!

 

[Norman_E]

I sincerely hope it is no more than about 12 tons, otherwise you are going to find that it sits very deep in the water. At the extreme of your estimates, 21 tons, I doubt it would have two feet of freeboard. Even at 16 tons it will sit pretty deep. Bear in mind that a Bavaria 36 is about the same size with an empty weight of about 7 metric tons but it has a flatter section hull and almost certainly a broader stern, thus putting more square area into the water. At 16 tons expect your boat's hull to sit about 2.5 times as deep in the water as the Bavaria.

 

[parbuckle]

If you havnt done it yet I would get in touch with the Hartley Ferro Cement Association in NZ ,they can be found on Google, no website but Email address and tel no.

Email photos to verify design and possibly put you in contact with another owner. Also there is a Ferro Cement boat owners association that may have some knowledge of

this design. Presumably the boat was built to a design as someone knew where to put the waterline I dont think they would have guessed it . Judging by ferro boat

pictures on the net their waterlines show that displacement is not wildly more than similar grp boats mainly because there is a lot less added ballast so it could be a

lot lighter than you think.

 

[lw395]

Ferro boats vary a lot.
Assuming you can tell where it floated, you could work out the volume of water displaced.
But if it's 11m by say 2m on the waterline, that would be something like 16 sqm, so every centimetre of immersion is about 160kg, so you would not need to know the waterline exactly to get within a tonne.
You would have to get a pretty good idea of the cross-section at a few stations.
I would be wanting to know 'it's definitely less than x', rather than a best estimate if you see what I mean!

 

[Gordonmc]

My boat is a John Samson, 36' over deck with a sparred length of 42'.
She was lifted in Liverpool and road-hauled to Ayrshire with no drama. The crane driver said the boat weighed in at 14.5 tons, this with the deisel tanks about half full and the water tanks empty. Masts were off.
I hope that helps.

 

[chrishelen]

I would tend to agree with an earlier post..get the crane to take the weight of the boat..if it is too heavy for the crane the alarm will go off..there should be a weight readout in the crane cab.still have to pay the man if it is too heavy.

 

[davidpbo]

If its too heavy for the crane, the crane can't lift so surely an accurate weight can't be obtained?