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Old 12-08-2008, 09:35   #61
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Gludy, Are you sure you have made the right decision, it seems to me that you cant get the Fastcat out of your mind, is this 'Buyers Remorse' - maybe you misread the instruments on the StFrancis and now you are doubting your own mind.
Isn't it about time you let your tirade against Gideon drop and we should get back to the topic of this thread ie 'SAVING WEIGHT'. - please
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Old 12-08-2008, 09:41   #62
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OK - I do not wish to offend and will let the matter drop.

I still do not understand how such lightness cannot translate into speed but that will have to remain a mystery to me.
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Old 12-08-2008, 09:47   #63
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High Noon!

I sorta like Gideon's invitation to race. I'll crew on either boat and pay my way to the racing grounds.

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Old 12-08-2008, 09:48   #64
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Originally Posted by Gludy View Post
OK - I do not wish to offend and will let the matter drop.

I still do not understand how such lightness cannot translate into speed but that will have to remain a mystery to me.
Two years ago I purchased my Dolphin cat and I can assure you that after I put all the stuff on it i.e. washer, solar, houshold items, tools, spares, kayak, more sails, clothes, books, fishing gear, electronics etc etc. IT GOT SLOWER, WITHOUT A DOUBT. You should believe that weight matters.

Once you are out sailing your new cat the speed of a FastCat will no longer matter.
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Old 12-08-2008, 09:57   #65
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Gludy,

I'll disagree with that last one. A lighter boat will be faster, its just a question of how much. (Unless you take the lead out of a lead mine mono hull for weight savings... )

On identical boats: The same sail area, wind speed, and surface/form drag... removing weight makes a faster accelerating boat. Thats just physics. Less mass, less work to do... same power available, it does the same work in less time. Gets there faster.

Changing boats, changes sail area, surface and form drag, and the location of the weight. All those fractions and ratios of displacement to sail area, beam to waterline length... have changed. Apples and oranges.

The wrench in the gears? On paper, weight reduction only works for acceleration. Once you reach a speed where power and drag are equal, and you are nether accelerating nor decelerating (Yeah Physics Nerds... Negative acceleration. ) Weight is largely irrelevant... unless you want to get in a viscious cycle of removing weight, to lower suface drag, to go a little faster. Problem? Lowering displacement on the same size vessel, reduces water drag... and raises air drag.

What I don't know, is if its a 1 knot difference, or a 1/100th of a knot on a normal boat vs an ultra-light boat. However, at 8 knots a 10% increase in speed is only .8 knots. That doesn't sound like a lot... but a 20 mph increase (10% of 200 mph) on a motorcycle, or sports car shows its self a little faster. Nevertheless, in both cases, you get where you are going 10% faster.

Zach

P.S. Yeah, I spend entirely to much time pondering how to make things faster and lighter. Its a curse... but I can pick up my bike with one finger. If I wanted to go fast, I'd take a car or airplane not a boat or bicycle... But the desire to go FASTER with either will drive one to the brink of insanity.

P.P.S. It really pissed me off when I got passed by a Stilleto 32, that was hauling the main up, on the way out of the channel. Thats just sick and twisted right there, I want one.
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Old 12-08-2008, 10:02   #66
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Two years ago I purchased my Dolphin cat and I can assure you that after I put all the stuff on it i.e. washer, solar, houshold items, tools, spares, kayak, more sails, clothes, books, fishing gear, electronics etc etc. IT GOT SLOWER, WITHOUT A DOUBT. You should believe that weight matters.
Once you are out sailing your new cat the speed of a FastCat will no longer matter."

I have not stated anywhere that weight does not matter - I fully accept that it does matter.However my current position is that its not as simple as reduce weight by 10 per cent equals increase in speed by 7 per cent.

The speed of the FastCat only interested me in as much as the figures I have seen on its performance to date do not make sense to me. I would have expected a much faster boat.

Gideon says ... and I am sticking to the subject ... that the FastCat is about 15 per cent faster than the SF50 but the SF50 is twice its weight!!!! Gideon also states that a ten per cent speed reduction equates to a 7 per cent increase in speed .... the two statement appear to clash.

I am more than happy with my decision and my main focus is not on learning enough to spec the boat properly. In doing that I am trying to understand more about sailing and that means understanding all the basic relationships - weight and speed being one of them.

Currently I cannot accept the figures that started this thread and no evidence has been put forward in support of those figures.I am about to give up trying and will in future maybe just learn to ignore such discrepancies
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Old 12-08-2008, 10:06   #67
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Zach
I never at anytime stated that weight does not matter - I have stated the opposite - that it does matter.

I have stated that the relationship is not simple and that I currently do not understand it but that does not mean it does not matter - basic physics states that it does.
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Old 12-08-2008, 10:09   #68
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Gludy: you are coming accross as vengefully affronted and unreasonable. A hundred years ago someone selling a yacht at this level of the market was entitled to say no to a prospective client for any reason whatsoever, possibly even because he doesn't want a continuing relationship with him. A client responding as you have would have been dismissed as no more than a spurned lover*: "He is not acting as a gentleman should". In this era of political correctness people start web sites to vent their indignation, and perhaps don't realize how poorly their actions are perceived by readers. Please consider how you appear to us, give up justifying yourself, and enjoy your St Francis!

*"Hell hath no fury like a woman scorned!"

I think we should also be fair to Gludy, HE said NO THANKS to the Fastcat after he tested it. Gideons response was after Gludy proclaimed his choice of another design publicly.


So Gludy was not the scorned party here.

It seems to me that Gludy feels that he has been fed so many discrepant "facts" that he had to react to the continued dicrepancies and wild claims of speed, that he did not see.

cheers

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Old 12-08-2008, 10:16   #69
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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.
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Old 12-08-2008, 10:21   #70
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Quote:
Originally Posted by Gludy View Post
OK - I do not wish to offend and will let the matter drop.

I still do not understand how such lightness cannot translate into speed but that will have to remain a mystery to me.
You haven't offended me in the least. Your questions are good ones, not unreasonable, and deserve a response. Some people on this list seem to feel it is acceptable to exaggerate, but not OK for anyone to question the exaggeration, under the pretense of not making waves and getting along.

I do think part of the answer is what many of have stated time and again. Under normal circumstances; it is generally, more logical, cheaper, and easier to extend the water line. It is becoming more obvious, that going to absurd efforts to save weight in a smaller boat to improve performance, may make sense in a race boat, but does not necessarily make sense in a cruising boat. That is not to say you should not make every effort to keep a cat light by using good construction materials and methods, but if you can get close to the same performance and improve load carrying by simply extending the water line for less money; doesn't that make the more economic/performance sense in buying a cruising cat. We are not under the same dimensional and handicapping constraints that race boats are.

I 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.

If I am wrong here Gideon, or anyone else, please jump in and correct me.
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Old 12-08-2008, 10:23   #71
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Just for the record, I was offered hull 13 out of the 19 sold so you are correct I was not scorned.

My interest in this thread is in trying to understand the mix of purported facts and figures. I have a scientific training and frankly could not care less who is right - my interest is what is right. I have even defended Gideon on this forum when he was in the right and others were providing misinformation.

I just found it difficult to sit back with figures being banded about that even now still contradict themselves.

I am told that a 10 per cent weight reduction equals a 7 per cent increase in speed and also that a boat weighing 50% the weight of the other is only 15 per cent faster ......... !!!

Whilst I am a novice to sailing I think I do learn fast and I have to truly understand what I am being told. I cannot just accept anything without properly digesting it and balancing it against the facts I know to date etc.
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Old 12-08-2008, 10:25   #72
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Quote:
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Zach
I never at anytime stated that weight does not matter - I have stated the opposite - that it does matter.

I have stated that the relationship is not simple and that I currently do not understand it but that does not mean it does not matter - basic physics states that it does.
Wait till BigCat chimes in with his knowledge of formulas and math.

You may be a little confused rught now.............just wait!!

http://www.cruisersforum.com/forums/...gcat-6844.html
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Old 12-08-2008, 10:32   #73
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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.
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Old 12-08-2008, 10:51   #74
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Weigth matters

Was I faster than BigCat?

Hello boys, read this (never mind gramma or spelling),

The equation is on page 11. If you have 10 % less weight in your cat, she will have approx 3 % better performance.
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File Type: pdf How to dimension a sailing catamaran.pdf (87.6 KB, 56 views)
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Old 12-08-2008, 10:53   #75
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So where does the 7 per cent come from?

Yes you get the prize ... you beat BigCat!!!
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