Is heavier better when it comes to boats?

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Jerbro

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OK, so if you've got an aeroplane, lighter is better, right? Is there any advantage to having a heavy boat? Does it handle rough seas better? Is it only an advantage if the extra weight is in the build quality? Is extra weight a disadvantage in planing boats?

I'm interested because of the weight difference between a Portofino 400 (12.5T) and Princess V40 (8.5T) - 4.0 tonnes difference!!! I know the portofino build is thicker, but is 12.5 tonnes taking off and landing better or worse than 8.5 tonnes doing the same?

<hr width=100% size=1>Jerbro
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Click here for <A target="_blank" HREF=http://www.btinternet.com/~jerbro> My ex-boat pics</A>
 
Heavy =Slow boat . light =Fast boat .my fairline did 16 knots in summer and 24 knots in winter.when it was emty.

<hr width=100% size=1>rich :-)) <A target="_blank" HREF=http://www.jersey-harbours.com>http://www.jersey-harbours.com</A>
 
Firstly, always take manufacturers figures with a large pinch of salt because weight tends to be estimated during the design stage and the actual weight may be very different
I know that the RNLI believe that, all things being equal, a heavier boat is a better sea boat than a lighter one but, with pleasure boats, all things are not equal. Obviously, for stability, you want the CoG as low as possible so a lot of weight high up, say in a flybridge boat, is not helpful. Then, fore/aft weight distribution is also important. A bow heavy boat may dig into waves and be dangerous in a following sea, an aft heavy boat may struggle to get onto the plane.
Ref. your specific question, Portofino 400 v V40, I really dont know that the P400 has a 'thicker' lay up (how do you know this?). I do know that the P400 is a beamier boat and that may account for some weight difference. It certainly seems to be bigger inside if I remember correctly
Actually, this may be one exception that disproves the rule. The V40/42 is well known as being a good sea boat with good speed - it just seems to be one of those hulls that works. On the other hand, I've heard that the P400 can struggle to get on the plane with the smaller engine options and is generally not one of Sunseeker's finest but thats just what I've heard, I have no personal experience so its best asking somebody who has

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Id guess somewhere in here is a discussion of old versus new, as everyone knows old boats were brilliant and lasted forever, and all these new manufacturers are making lightweight boats that will fall to pieces in no time etc etc etc. I m sure we must have some engineers on the forum, but i d imagine that with modern fibreglass techniques,computer assisted designs, manufacturers are now able to build boats with greater weight efficiency than in days gone past. Guess that makes them cheaper and they can use smaller,cheaper engines to achieve similar performance. There is probably much more care in all the fixtures and fittings to ensure the final weight is kept down. Dont think you can simplify and say the heavier one will be stronger, although the common acceptance is that the crew will fall to pieces before the boat,whether old or new(boat that is!)

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Racing hull: The lighter the better as long as it doesn't fall apart before the end of the race

Planing hull: The heavier it is, the more power and fuel required or it goes slower.

Displacement hull: Weight doesn't matter much, it's the length which primarily dictates the speed. Generally, heavy boats are considered more seaworthy.

Semi-displacement: Somwhere between Planing and Displacement

Extremely heavy boat: Sinks.


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Are you comparing the displacement or the dry weight, these are not the same thing. The Sunseeker has deeper vee hull so there is more of it in the water, hence it displaces more water in tonnes. This doesn't mean it weighs more just that the V40 has a flatter hull so has less displacement but more bouyancy.
I think manufacturers always quote displacement because this will remain fairly constant regardless of load, however dry weight will vary enormously with equipment etc..
However heavier (dry weight) boats though should handle better because they can't be thrown around as much, but will ultimately be slower.

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Uffa Fox once said,'Weight is only of use on a steamroller', although to be fair he was talking about planing sailing dinghies at the time.

Pretty much what the others said; If you want to plane, weight is expensive 'cos you need a bigger engine, a stronger hull to attach it to and more fuel.

cheers,
david

<hr width=100% size=1>This candidate works well when cornered and watched like a rat in a trap.
 
Re:Excuse me but.....

<<deeper vee hull so there is more of it in the water, hence it displaces more water in tonnes>>

I don't think that was the way Archimedes explained it to me..........

Surely the shape of the hull is irrelevant to how much weight of water it displaces. The displacement weight in the water is the actual weight of the water it displaces which equals its actual weight (unless it sinks). The dry weight depends on exactly what you specify is on board when you weigh it.

Anthony

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"as long as it doesn't fall apart before the end of the race" - that'd be a refference to yours and mine then Scott?

<hr width=100% size=1>Sod the Healey - I think I'll buy an E-Type.
 
"as long as it doesn't fall apart before the end of the race" - that'd be a reference to yours and mine then Scott?

<hr width=100% size=1>Sod the Healey - I think I'll buy an E-Type.
 
ah but, but ...

If i get in the bath and submerge myself I displace some water, but that "volume" of water is not my weight, someone the exactly the same size as me but not as dense ( err i mean smaller boned ! ) will displace the same amount of water but weigh a different amount. Likewise if i float in the bath with bits of me above the waterline!, I still weigh the same but displace less. Hence a boat that displaces 12.5t is not neccesarliy 4t heavier than one that displaces 8t..it just displaces more.
Mind you I was quite sure about this earlier, but now my head hurts!

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no no no...

your weight (or more correctly mass) in kgs = the displacement in litres of your body (or a boat) because you partially float, the amount floating is a expression of the ratio between the density of water and the density of you(far be it for me to question your density...)

if you sank like a brick then you'd displace your volume, whether brick was clay or lead displacement would still be volume.

say you weight 80 kgs (I'm a fat bastard so about 105kgs) and you jumped into a giant measuring jug of water you'd see the level rise by 80 litres



<hr width=100% size=1>Sod the Healey - I think I'll buy an E-Type.
 
ref weight of boat.this is not always connected to lay up quality.The targa 37 has only got 1or 2 dinky little batteries to do everthing whereas other boats ie.mine, has 6 batteries to do more or less same job.

<hr width=100% size=1>If it aint broke fix it till it is.
 
As a firm believer that all new boats are heaps of tat with candy floss weight hulls and worse than Fablon cherrywood interiors.I would like to mention that when noticing than a stringer had cracked away from the hull in a nearly new sports boat built by a quality maker,the comment was made"Not to worry they all do that"
Buy an older boat.It will have better quality fitting out and thicker lay up on hull.You will even be able to go forward without stepping on those white seats maybe.Have a look at Yachtsurvey.com if you want to see the rubbish materials inflicted on buyers by so called engineers of advanced materials.Namely sandwich construction in hulls.Some boats need a warning label "Do not get wet"/forums/images/icons/laugh.gif

<hr width=100% size=1>If it aint broke fix it till it is.
 
Thanks Chris. I'm now informed and confused. Having tried to confirm the weights of the two different boats mentioned, I've found the following...

V40 - everything from 'dry weight' of 11 tonnes to 'weight' of 7400kg to 11500kg
P400 - everything from 'dry weight' of 9000kg to 'weight' of 12000kg

????

So, on balance, they're probably about the same weight!!

Thanks for all the info everyone.

<hr width=100% size=1>Jerbro
====
Click here for <A target="_blank" HREF=http://www.btinternet.com/~jerbro> My ex-boat pics</A>
 
Chris - you couldnt have been listening in your school Physics lessons. Go to the back of the class!

The weight of water displaced is equal to the weight of the boat. Thats why it floats. And the more load you put on the boats, the more it weighs and the more it displaces. Until it cant displace any more because its completely under water - when it sinks.

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Doh..puts on triangular hat..

yes I have slept on this and realise I was trying to rewrite the laws of physics, I bow my head in shame.
However in my defence I think you'll find that the "quoted" displacement is rarely an accurate figure for assessing a boats weight, my own trailable boats quoted displacement is 1.7t, but on a weighbridge after subtracting the trailer weight, and with half tanks and a small amount of junk on board it weighed 2.5t. Perhaps Sunseeker are just a bit more honest about their boats.

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Re: oldgit

aha,was sure someone would nibble the bait! I m confident there will have been plenty of older boats that were not quite so faultless too. I m not really on either side, merely suggesting that just because a boat is older and heavier does not mean it is better than a new lighter one. You only have to look at the provisos in all the reviews of older boats in MBM about stress cracks etc on older boats to see that they too have their problems....

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Re: Chris_d, me and the Nobel Prize

You prove your theories to the scientific community and we'll share the Nobel prize OK?

Talking about being in a bath is leading to some confusion
- if you or someone else of exactly the same size + shape ie volume as you but different weight (yeah but let's keep away from the density joke) is SITTING in the bath then ipso facto you/he/she (well perhaps not) are not displacing enough water to float so you are displacing your volume, which is not enough to make you float your head arms etc still being out of the water and some of your weight is on your bum
- if the bath is big enough ( <<Likewise if i float in the bath with bits of me above >> just how big IS your bath or how small are you?) then you must have a lower density than the water and the weight of the of the volume of water you displace will be exactly the same as your weight. Now your heavier body double will float a little lower in the water, their extra weight "forcing" more water to be displaced until they float at a lower level.
- If either of you sink you are denser than water, your volume will not displace enough weight of water and so you will sink.

Now, again, if I've got this wrong so did the old Greek and we'll be famous

hence my argument that the shape of the V hull makes no difference to the displacement weight

Come in BB you and I are on the same side here but I doubt if you would only displace 80Kg nor me !

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Re: Chris_d, me and the Nobel Prize

sense is beginning to prevail!

It's a good job many of the above aren't trying to calculate how much concrete ballast to put into their project live-aboard barge, or they'd be living in submarines!

It would have been timely to post my 'stones in Loch Ness' puzzle again now, but it would go straight to Alistair's head again. Anyway BB won that prize, so perhaps he must have 'phoned a friend' on that occasion!

<hr width=100% size=1><font color=blue> <A target="_blank" HREF=http://www.mboat.org>http://www.mboat.org</A></font color=blue>
 
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