Multihull Weight Saving Stratagies

[thinwater]

Originally Posted by owly

I began some time back searching for the ideal catamaran for my purposes. That mostly solo worldwide voyaging with no actual "home base". It needs to be economical in every respect, both up front, and ongoing. I've set a 30' LOA parameter for a number of reasons including the fact that 30' / 9M is the typical cost break point where services and maintenance is concerned, as well as the desire to participate in events that have 30' as their upper end, and simply keeping things at a comfortable size to handle and to maintain.
Not looking for a condo cat.......... don't want one. As size increases, weight increases, rig size and cost increases, hardware and rigging and ground tackle all get bigger, heavier, and more expensive, larger engine(s) more fuel, etc..... It's a spiral toward infinity. For me 9M is the "sweet spot'. Except that payload is not sufficient.... and the last thing I want is an overloaded pig.
This has pushed me increasingly toward home building, as I can build light from foam sandwich, and I have determined a design I can build with hulls of greater displacement than the stock design without having to design it myself......... which is beyond my pay grade.
The best weight saving strategy out there is "build light". Built conventionally this boat with these hulls should come at around 4500 lbs empty weight or perhaps less, and give me over 8000 total weight to lwl. That's a payload of about 3500 lbs. These numbers are all a bit "loose". Built in sandwich carefully, and without a lot of "fancy work", I expect to be able to hit an empty weight of something under 3000 lbs. That extra 1500+ lbs payload will come at a considerable initial materials cost.... a few dollars a pound, but will pay dividends for the life of the boat. I currently estimate the cost penalty at about $5000, which I consider realistic. The dividends in addition to weight reduction over ply / epoxy include sound deadening and insulation. They also include having smooth interior hull sides with no stringers.... eliminating corners for crud, moisture and mildew to accumulate, making cleaning &c easier. It means that I can carry more spares and materials when traveling into remote areas, and have a more complete workshop, and be less dependent on shoreside services. Building also means that I will know the boat inside out.


H.W.

Although this is not literally the approach you have in mind, it WILL give you ideas.
https://amzn.to/2CF7JQH

[thinwater]

One of the simplest energy savers is to get up with the sun and go to bed when it sets. Not popular, though. I don't really understand why.

[VBsail]

I am always surprised what a bag of 4 self inflating PFDs weighs vs a bag of standard ones.

[Training Wheels]

I don’t think I mentioned this one. We don’t cook much, and when we do we grill. So, we took out our stove and oven and just put in a cooktop. Much lighter, and more storage.

[vorpal blade]

Originally Posted by Training Wheels

I don’t think I mentioned this one. We don’t cook much, and when we do we grill. So, we took out our stove and oven and just put in a cooktop. Much lighter, and more storage.

we have done a similar thing but have replaced everything with a decent BBQ that has a tight fitting hood. We can fit frypan and pots on the top when required, use the BBQ plate as usual and with the right size roasting dish make bread, cook whole roasts. Also have adapted some racks and used it to smoke fish too.

[clockwork orange]

Weight is cumulative, take care of the ounces and the pounds will take care of themselves. I have a Gemini cat and being a boatbuilder by trade find it necessary to correct the many structural deficiencies which of course means added weight so I am always on the lookout for things to remove to at least keep it at par. I don't mind a little extra weight in structure but can't tolerate wasted weight in "fluff" ie, things that are only for cosmetics. Fortunately there are many opportunities for weight reduction on my boat. An example would be the teak and holly sole on the bridge deck which is close to 100lbs and brings nothing to the table in my eyes as it is 1/2" ply dry screwed to the fiberglass bridge deck. It serves no purpose other than looks and by removing it altogether and replacing it with a 20lb option ( I hav'nt decided what yet) i save 70-80lbs.


Steve.

[Thumbs Up]

Another way that eliminating the galley can help is by causing the crew to lose weight.

[mikedefieslife]

Originally Posted by Thumbs Up

Another way that eliminating the galley can help is by causing the crew to lose weight.

Crew can be used as ballast though when you start flying a hull.

[Training Wheels]

Exactly!

[ATTACH]181899

[owly]

Originally Posted by Thumbs Up

Another way that eliminating the galley can help is by causing the crew to lose weight.

That one got to me ;-) ........... I've been doing intensive fasting for health and weight loss reasons.... I'm no more overweight than the typical American, but I'm tired of it!! Over the years I've watched weight creep up to 20+ pounds over where I want to be. I'm doing fasts of indeterminate length broken by a couple of days of "normal" eating. (keto). The first was 2 days, broken by circumstances where I didn't want to be rude. After two days I resumed for 4 days, broken when my body said "it's time to break your fast". Two days later I resumed, and I'm two days into the third. At the end of the last 4 day fast, I was approximately 10 pounds down (morning weight), or which half came back as soon as I started eating. I take nothing but water (and decaf coffee). I plan to continue this cycle until I hit the weight I am shooting for, then do alternate day fasting as a normal routine. I find fasting effortless. I never experience hunger except for brief periods.


If I can drop 20 pounds, that's 20 pounds off the payload. If I eat only every other day, that cuts half the food payload for me. Talking other people into doing that.... might be a bit of a challenge ;-)


H.W.

[dancor01]

Originally Posted by Training Wheels

Exactly!

[ATTACH]181899

That look like a Horstamn Tristar

[dancor01]

Originally Posted by Thumbs Up

Another way that eliminating the galley can help is by causing the crew to lose weight.

Another way ditch the inboard that weight 400+ And have the crew use oars.
They loose weight and stay fit.

[jdazey]

Originally Posted by dancor01

That look like a Horstamn Tristar

Hmmm....not like any Horstman I've ever seen, and I've seen a few including one derelict here in Shelter Bay, Panama.


Cheers,

[owly]

Originally Posted by jdazey

Hmmm....not like any Horstman I've ever seen, and I've seen a few including one derelict here in Shelter Bay, Panama.


Cheers,

I'd call it one of the larger Corsairs.... probably a 37.



H.W.

[44'cruisingcat]

Originally Posted by mikedefieslife

I mentioned either earlier in this thread or in another, that the lighter boats I've seen and been on, rock way more in swell than the heavier ones. Additionally, that that rocking quicker and more violent.

.

There's no reason for this to be true.

F=ma, so logic would suggest a lighter boat will accelerate quicker in response to a wave.

But a lighter boat will have slimmer hulls and less waterplane area, so less force will be imparted by the waves.