Saving weight

[ldrhawke]

Originally Posted by schoonerdog

Ahhh, back to the topic of saving weight... I did find that there are several items on the boat that really contribute to weight, water (which you can reduce by carrying a water maker), fuel (which you really can't), the weight of the dingy and outboard, and the weight of the batteries. For me the weight of my solar panels was offset by allowing me to reduce our battery capacity in half as now I simply compensate for nighttime draw, not daylight. Our 700 watt worth of panels also can completely charge the batteries, not simply top them off.

One quick low cost tip is to buy a cheap scanner and scan all of your manuals, documents, photos, magazines, reference book chapters that you found particularly useful, cookbooks etc. that you would normally carry with you and store it on your laptop and a backup on DVD. Also a good low cost tip is gradually through the years keeping track of exactly which tools you need and which tools you don't (for instance with my yanmar engines I have only need a metric wrench set).

BTW, I would be extremely careful on putting a high amp alternator on your engine. Make sure your engine is capable of carrying that by checking with your documentation and the manufacturer.

I have to disagree to some extent on you can't reduce fuel load.

If you can reduce your daily electrical load by doing things like; improving refrig. insulation and using more efficient electrical equipment, ie, compressor,lighting, etc and then size the house battery bank to match the daily consumption; then size the solar cells/wind generator to match or come close to that demand, you will reduce or eliminate the need to run the engine.

Compare to needing to run the engines and hour a day and burn a couple of gallons of fuel daily, that can reduce fuel load hundreds of lbs; depending on time between fuel points.

Going to much higher alternator out put is very common. A single high out put or dual high out puts are a standard options on a Yanmar engine, and easy conversions on most others.
Yanmar Options

By going to a large AGM battery bank, that charge much more rapidly on both solar cells and directly from alternators, and increasing the alternator output three or four times, you can cut engine run time in half or more and save hundreds of lbs of fuel that would other wise need to be carried. Reason for a second alternator topic

Unless you over size the stock alternator and modify your charging system, you are probably only charging your batteries to 70 to 80% of their full storage capacity. Proper charging is like adding an additional battery to your existing bank.

[Zach]

Gludy,

We agree, I'd just like to have a discussion that draws the real weight weenies out of the wood work.

I just tried to say (I guess I failed...) that comparing two different designs, and sizes boats with weight as the only common denominator will not yield anything valuable. Weight alone leaves out the million other potential sources to find and design for speed.

Bigger boats are faster boats. They have the mass and stability to keep more sail up and have the water line length to use it. What they cannot do, is without a massive sail area to displacement ratio... ghost along in slow wind speeds. Average speeds, vs top speeds. Either more power, or less weight... or both!

Compare my Pearson Triton to an Olson 30 which has 20 more sqft of sail area. Or a Westsail 32 to Bill Lee's Merlin, which is 6,000 lbs heavier. Load in a two peoples worth of stores for cruising and call it even.

One is a similar size, one is a similar weight... Two are fast as hell, and two can be made fast(er) by reducing weight. Both are apples and oranges, but nevertheless are mono hulls. I wonder if this isn't a parallel (albeit slightly exaggerated) to the Fastcat/SF50 debate. What wind speed do you want to be fast, and how much fun do you want to have.

My personal interest in the matter? I have a 6 horse outboard on the back of what was a nearly 9,000lb boat. I've around 1500-2,000 pounds out of her with full tanks. (3-4 inch rise on the waterline, 570lbs per inch) and am continually looking for ways to lighten her up while empty. With high hopes that when I load in a few thousand pounds of gear, she still sits on her lines and will go hull speed on a sneeze.

Zach

[ldrhawke]

Originally Posted by Gludy

Idrhawke
All you post makes perfect sense to me - I would just like to comment on your statement
" may be off on these numbers, and if I am correct me. But, it appears your option in this discussion is to pay roughly 50% more for a short light FastCat compared to buying a big old heavy SF50 with more crusing amenities, and that comes close to performing just as well and is less sensitive to over power with changing wind conditions. "

I am really asking why there is little to no difference in speed and how this tallies with the opening post of this thread - that a 7 per cent speed increase results from saving 10 per cent in weight.I really cannot accept that life is that simple but them maybe I am an old sceptic

I was shocked by how well the other two boats I tested performed - none of it made sense to me and then I saw this thread opening with a simplistic statement that, as an engineer put me on guard plus go right against all I have witnessed hence I questioned.

There was also going to be a question about sea state and light boats and how that effects speed but we never got past the first hurdles of the topic.

Aren't you comparing tests of a FastCat 435/455 to a SF50? The waterline alone is an equalizer in performance.

[Zach]

Oh... and to get back on track:

Running with the battery bank size reduction:
Anyone put a battery bank under a sleeping berth? I'm a little curious about the health aspects, a little bit of hydrogen off gassing and all.

My settees double as berths, and are mighty close to the middle of the boat. See no reason to pack clothes and stuff down low on center, and a battery bank aft under the cockpit...

Also figuring that I won't try to heat the cockpit lockers, and keeping batteries warm seems to boost the available amperage. (Not sure if it works out for amp hours or just cranking amps though... shrug.)

[ldrhawke]

Originally Posted by Zach

Oh... and to get back on track:

Running with the battery bank size reduction:
Anyone put a battery bank under a sleeping berth? I'm a little curious about the health aspects, a little bit of hydrogen off gassing and all.

My settees double as berths, and are mighty close to the middle of the boat. See no reason to pack clothes and stuff down low on center, and a battery bank aft under the cockpit...

Also figuring that I won't try to heat the cockpit lockers, and keeping batteries warm seems to boost the available amperage. (Not sure if it works out for amp hours or just cranking amps though... shrug.)

Use AGM seal batteries and eliminate the hydrogen off gas issue.

[freetime]

Gludy and Fastcat435:

Tell us the true about the testsailing. How long was it, wish fastcat model was it, what was the weight of the boat, what kind of waves was it.
And Fastcat435, Don´t you have a boat that you can let multihullmag or simular magazine do a nice test. Or make a good video and show us how good the boat are. I have only seen the butterfly and the one settingsail2009 bought. Make a new homepage now when you have the new factory. And give us links to blogs from owner of fastcat like Luxury Cruising Catamarans: Antares Yachts have. We can see many of your nice ideas on this forum and that is very interesting.

[Joli]

Weight is a funny thing. A heavy boat can be a very fast boat is some conditions. A large heavy boat in light air can be extremely fast since they build wind and have the mass and stability to carry through. The design of racing multis is to take advantage of trade wind circumnavigations. Build it light and let it go. Sail deep and pull the apparent. Stay in the power band where the massive righting moment can be best used. Up and down you are limited to waterline.


Ted Hood's design philosphy:

http://tedhoodcustomyachts.com/asset...sophy_1-22.pdf

[Gludy]

I think there are many good points being raised here but what is becoming clearer is that the simplistic opening post on the thread cannot be right.

I agree that the WLL is critical so it seems absurd to me to spend large sums of money reducing weight as opposed to simply increasing size.

Does a very light cat accelerate quicker in a gust of wind ?( I think it does).

So does such a light cat also get stopped quicker by short sharp waves? In other words does not sea state become more critical in getting speed out of a light cat.

We were were creating our own wind in the heavy SF and in very light winds sailing at almost wind speed.

[Zach]

Joli, Excellent article!


Gludy,
To my limited understanding, that is correct. A lighter boat is slowed down by steep chop, whereas a heavier one is more apt to go through them.

The heavier boat goes through the waves, a lighter one goes over them. But in the small size we're talking about, it doesn't take a huge sea before both are wet and uncomfortable... (Grin)

Also has to do with flair and buoyancy in the bows, and can make a light boat wet... or a heavy boat dry.

However, I have yet to figure out why the ultralight Merlin, is half submarine...

[GordMay]

If a lighter boat generally moves faster (than an otherwise similar, but heavier boat), it has more speed to give up to head seas; and might be expected to remain as fast or faster over the average - even in "head to" conditions.
In any sea condition off the bows, she/it should definitely remain faster, overall.

[Nordic cat]

I went to the Multihull Dynamics site that has data on more than 800 cats and tris, and looked up the data for the Fastcat 435. (Multihull Dynamics, Inc. - Home) You need to join as a member or buy the data, but I have found it to be a very useful site to compare data and expected performance figures for different boats. Prices are very reasonable compared to the time you can save.

I hope they don't mind me publishing a couple of numbers

They did a comparison on the Fastcat compared to the average of all the other likesize cats in their database (what they call the base line I think).

It turns out that the Fastcat is on average only around 6% faster than than the average 42-43 foot cat!!! N.B. This is based on a boat weight of 5 tons, and a sail area of 126.7 m2. Fastcats now only have 118 m2 of sail area, so the speed advantage is probably only around 4% faster I would think.

The Fastcat also has a smaller beam, so it has to reef earlier, it also has less bridgedeck clearance.

Compared to a Schionning 1320, the Fastcat is slower and less stable ( nearly 1 meter less waterline beam, and about 30cms narrower than the average cat)


My take on this is that the Fastcat kept light is a faster than average cat, but not by much, and nowhere near a star performer as we have been led to believe, and as Gludy has found out first hand.

As stated above, waterline length is a key factor.

The Multihull Dynamics site also has figure for the St. Francis 48, but I didn't look at them.


As Terho also concludes, weight savings taken to the extreme gives you very little bang for a lot of bucks.

Cheers

Alan

[ldrhawke]

WEIGHT SAVINGS

When all is said and done, the key to weight savings has little to do with epoxy/carbon fiber, kevlar construction and hull design; to keep the hull from setting a foot deeper in the water and from turning the boat into a slug. It is all in your ability to say NO!

NO to yourself when you pick up the 200 lb automotive tool box that only has a half dozen tools in it that you will ever use. NO to yourself when you order the boat with a 400 liter fuel tanks when you could get by with a 100. NO to yourself when you add 200 lbs in up sizing the engines. NO to yourself as your loading a 6 month supply of beer and liquor onboard. NO to yourself as you loading 100 lbs winter clothes aboard for a sail in the islands. NO to your wife who insists on having a half dozen evening dresses and as many pairs of high heels for spending that imaginary evening at the island Governor's Mansion.

And especially,NO to you wife who insists she won't go unless the boat has AC, Dishwasher, Microwave, washer and dryer, compactor, large freezer, large screen TV, and 6KW generator to run them.

Of course on the other hand............... after diving all day, that cold glass of beer, that tender steak for dinner, with a cold glass of good wine after, hot shower, clean clothes, having warm dry sheets on the bed, a comfortable nights sleep on that hot humid night; and a smile on her face may be worth giving up a few percent of boat speed even for the most avid sailor.

[Gludy]

"And especially,NO to you wife who insists she won't go unless the boat has AC, Dishwasher, Microwave, washer and dryer, compactor, large freezer, large screen TV, and 6KW generator to run them."

First of all that list is modest and just how can you sat No to the other half who probably has a veto on even having a boat?

That is probably the most difficult question I will ever ask on this forum

Also it can be pointed out that she is only tiny and there are no other people on board thereby saving the weight of ten people and their baggage.

Also in my case she has witnessed a slow light cat and a fast heavy cat so just how can I explain that when all the evidence is against me?

On this subject I am not a novice!!!

[Gludy]

I did actually try saying those "No's" to SWMBO tonight and her response was she agreed straight away!!! She said she had no need for dishwashers and washing machines because she has ME!!!!! She did say to stock up on the Marigold gloves as I will be using them a lot!!!

[tyrntlzrdking]

Gludy,

Congrats on the new Saint Francis 50! Wish I was rich.
I have been following this thread on and off since its begining.
It seems to me that many posts have been deleted.
Did you not say in an earlier post that Fastcat had told you that he was the European distributor for Saint Francis boats?
Is this true? Did he tell you this? Is he?
Maybe I misunderstood.

Jeff