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Old 09-08-2008, 14:18   #1
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Saving weight

As you probably know by now I'm very much into weight saving.
I'm also able to help others that want to save weight so let me know.
Weight saving is in everything from the anchor chain in front to rigid inflatable in the rear and a rule of tumb idea is that when you lower the weight of your boat by 10 % performance goes up by 7 %.
Greetings
Gideon
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Old 09-08-2008, 14:54   #2
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I know…I just changed my girlfriend for a lighter model and I am on a serious diet!....
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Old 10-08-2008, 00:19   #3
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good thinking, not only do you save on weight but the cost factor also kicks in less weight less energy to burn and !! like a new broom they just work better lol lol lol
However on your schooner it will not make a noticeable difference but it will help.
greetings
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Old 10-08-2008, 00:38   #4
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Fast cat - I once owned a 26-foot tri which really made me start thinking about both space and weight. A few changes I made from my previous boat included changing from a chain to rope rode, and installing a composting toilet which cut holding tank space and weight.

I'm now going back to a smallish monohull, but still want to keep weight down and keep systems simple. I'd love to hear more about tricks you've learned. I know one thing I always struggled with was spare parts, which one might likely never need, but sure could come in handy if you did.

I'm thinking main, roller furling jib, storm jib, but no other sails on board.
I do prefer chain, so am thinking of going back that way despite the weight on a 30-foot monohull.
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Old 10-08-2008, 01:43   #5
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Weights a problem. My only home is my vessel and has been for almost 50 years. Everything I own is aboard it. I'd love to toss over a couple of hundred pounds... but the only thing aboard Wild Card which isn't pulling it's weight... is me!

Fatty, in Phuket, Thailand
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Old 10-08-2008, 01:44   #6
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Gideon, That is an interesting comment ie 10% weight saving 7% increase in performance, this I am assuming has more effect in lighter winds, am I right?
Also would this equation be true on a modern production cruising cat of say around 40ft where it's hull length to beam ratio is say about 1:8 to 1:10, weight around 7 tons, so having a medium wetted suface, what I am trying to say is that if you took a modern production cat ie Lagoon 410, Lavezzi 40 or Leopard 40, ripped off their spars, changed them to carbon fibre witrh fibre standing rigging, feathering props, good set of sails, plastic toilets, prodder with gennaker, no generator, no A/C, no watermaker etc, you would get a much better performance or would it be a waste of money?
I would welcome your comments.
Ian
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Old 10-08-2008, 02:01   #7
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Quote:
Originally Posted by ireaney View Post
Gideon, That is an interesting comment ie 10% weight saving 7% increase in performance, this I am assuming has more effect in lighter winds, am I right?
Also would this equation be true on a modern production cruising cat of say around 40ft where it's hull length to beam ratio is say about 1:8 to 1:10, weight around 7 tons, so having a medium wetted suface, what I am trying to say is that if you took a modern production cat ie Lagoon 410, Lavezzi 40 or Leopard 40, ripped off their spars, changed them to carbon fibre witrh fibre standing rigging, feathering props, good set of sails, plastic toilets, prodder with gennaker, no generator, no A/C, no watermaker etc, you would get a much better performance or would it be a waste of money?
I would welcome your comments.
Ian
Hallo Ireaney yes if (modern) production cats would save on weight you would get a much better performance, down wind because of windage you would gain up to 9 % in speed for each 10 % in weight saved while upwind your speed would increase with 6 to 7 % because of added windage. It would not be a waste of money
and it will ad to comfort to specially with a carbon rig reducing hobby horsing and the lower weight will also reduce the upwind digging into waves , she will go over waves instead of digging in so there will be less breaking action.
For these reasons we are still working on weight reduction on our FastCats
It is becoming harder but we still make improvements.
My aim of 5000 kilo for the FastCat 455 is in sight.
Greetings Gideon
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Old 10-08-2008, 02:02   #8
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Quote:
Originally Posted by nautical62 View Post
Fast cat - I once owned a 26-foot tri which really made me start thinking about both space and weight. A few changes I made from my previous boat included changing from a chain to rope rode, and installing a composting toilet which cut holding tank space and weight.

I'm now going back to a smallish monohull, but still want to keep weight down and keep systems simple. I'd love to hear more about tricks you've learned. I know one thing I always struggled with was spare parts, which one might likely never need, but sure could come in handy if you did.

I'm thinking main, roller furling jib, storm jib, but no other sails on board.
I do prefer chain, so am thinking of going back that way despite the weight on a 30-foot monohull.
just use 10 meters of chain followed by 40 meters of weighted line, much better also because of the stretch in the weighted line.
Greetings
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Old 10-08-2008, 02:53   #9
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Quote:
Originally Posted by fastcat435 View Post
Quote:
Hallo Ireaney yes if (modern) production cats would save on weight you would get a much better performance, down wind because of windage you would gain up to 9 % in speed for each 10 % in weight saved while upwind your speed would increase with 6 to 7 % because of added windage.
Gideon,
Do you have some calculations/ formulae to back these figures up?

I agree that lighter weight will give you a faster boat because:

a.) Less wetted surface means less friction.
b.) less wetted surface also means less wave making resistance.

Water based resistance grows roughly with the cube of speed.

Upwind, a higher boatspeed will mean higher AWS so more power available, but wind energy grows with the square of wind speed, and so does the drag from the wind.

So the numbers you quote will vary with:

Boat design - underwater hull shape will have a small influence on wetted surface area and wave making.

Windage will have a big influence. At a certain speed, windage becomes bigger than water based drag.

But reducing water based resisitance has a bigger influence, especially at around "hull speeds" and above.
Quote:
It would not be a waste of money
and it will ad to comfort to specially with a carbon rig reducing hobby horsing and the lower weight will also reduce the upwind digging into waves , she will go over waves instead of digging in so there will be less breaking action.
For these reasons we are still working on weight reduction on our FastCats
It is becoming harder but we still make improvements.
My aim of 5000 kilo for the FastCat 455 is in sight.
Greetings Gideon
With all your focus on performance, I don't understand why you don't go for a rotating wingmast. This will easily add 5 -10% more power to your rig, increase pointing ability etc. and decrease windage especially if you choose the optimal mast chord.


Cheers

Alan
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Old 10-08-2008, 03:34   #10
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Gideon and Alan, Thanks both for your comments which have been taken ob board.
Ian
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Old 10-08-2008, 07:51   #11
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Back in '92 when I was on the Rio Dulce I met a guy with a really sleek, custom built trimaran. He was a fanatic about weight aboard, but I thought he was a bit compulsive about it. There was almost NO furniture aboard. He (and his girlfriend) slept on the cabin sole in sleeping bags and seating was a couple of bean bag chairs. He removed all the covers on the books he had aboard and cut the handles off the toothbrushes, too.
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Old 10-08-2008, 08:04   #12
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Cut the handles off the toothbrushes !!???
Steve
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Old 10-08-2008, 08:46   #13
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It would not be a waste of money
and it will ad to comfort to specially with a carbon rig reducing hobby horsing
I don´t understund that!
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Old 10-08-2008, 09:11   #14
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Cut the handles off the toothbrushes !!???
Steve
Why tooth brushes why not share that saves even more
lollollol
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Old 10-08-2008, 09:46   #15
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Custom moulded carbon fiber or kevlar toilet bowls like the Volvo 70s use...
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