Multihull Weight Saving Stratagies

[thinwater]

Let's not turn this into an anchoring thread. We'll come off like a bunch of monohull sailors.


How about kayaks for tenders? On my Corsair F-24 I switched from a hard kayak to a rigid inflatable, saving 20 pounds. It paddles quite well. I can also stuff it below if I like, though I seldom do. No cheap, but built like a good inflatable tender.

[Thumbs Up]

I have never had mine on a load cell but am sure that it would weigh in at least several tons less than comparable sized production cats. You can knock plywood hulls all you want (which you like to do on this forum except for the Searunner threads) but as an engineering material is up there with carbon fiber. Wood has some amazing properties, practically unlimited fatigue cycles, easily repairable, aesthetically pleasing being some of them. The sound of the waves crashing into wooden hulls is very different than plastic. I don't really have to worry much about weight because my cat weighs less to begin with. Not really a performance boat but less of a condo-maran than all these fancy high priced FPs, Lagoons, and Leopards that everyone is salivating over. So with the lighter plywood hulls and box beam superstructure you can go with a smaller rig which not only saves weight but is much safer. The weight of just one fiberglass access hatch on these condo-marans is like all of mine put together. Every sailboat is a compromise (comfort, safety, speed, cost) and there are tradeoffs. Sure there are high tech materials but out of the range a cruising sailors budget. Wood is the original high tech material. There are wood boats today that are in fine condition that are over 100 years old. Polyester resin wasn't even invented when they were built. There are threads here where all they can talk about is never buy a balsa cored hull, a plywood hull, anything other than an inch of solid glass below the waterline. And now we want to talk about weight saving strategies, maybe you need some of these:https://www.westmarine.com/buy/thetf...ilet--10286425

[thinwater]

Low friction rings. I'm changing to them everywhere I don't need to adjust under high load. They even work with polyester-covered line, as long as the deflection angle is not too great.

[4:1 bobstay tackle. Not adjusted under load.]

[StuM]

Originally Posted by Thumbs Up

And now we want to talk about weight saving strategies, maybe you need some of these:https://www.westmarine.com/buy/thetf...ilet--10286425

Ye gods! Over $13 thousand for a dunny?

[thinwater]

Originally Posted by StuM

Ye gods! Over $13 thousand for a dunny?

And after you fill the holding tank it ain't going to be that light. I'd think for that kind of scratch they would have addressed the entire system with some manner of magic and made it lighter.


And don't forget the matching bidet.

[owly]

Originally Posted by Thumbs Up

I have never had mine on a load cell but am sure that it would weigh in at least several tons less than comparable sized production cats. You can knock plywood hulls all you want (which you like to do on this forum except for the Searunner threads) but as an engineering material is up there with carbon fiber. Wood has some amazing properties, practically unlimited fatigue cycles, easily repairable, aesthetically pleasing being some of them. The sound of the waves crashing into wooden hulls is very different than plastic. I don't really have to worry much about weight because my cat weighs less to begin with. Not really a performance boat but less of a condo-maran than all these fancy high priced FPs, Lagoons, and Leopards that everyone is salivating over. So with the lighter plywood hulls and box beam superstructure you can go with a smaller rig which not only saves weight but is much safer. The weight of just one fiberglass access hatch on these condo-marans is like all of mine put together. Every sailboat is a compromise (comfort, safety, speed, cost) and there are tradeoffs. Sure there are high tech materials but out of the range a cruising sailors budget. Wood is the original high tech material. There are wood boats today that are in fine condition that are over 100 years old. Polyester resin wasn't even invented when they were built. There are threads here where all they can talk about is never buy a balsa cored hull, a plywood hull, anything other than an inch of solid glass below the waterline. And now we want to talk about weight saving strategies, maybe you need some of these:https://www.westmarine.com/buy/thetf...ilet--10286425

I for one strongly concur with your statements about wood. Plywood with glass and epoxy makes an amazing composite material.... with a space age class strength to weight ratio and other properties.



Cored structures gain great stiffness due to their thickness, and that requires a light weight core. There is value in this technique, but it need to be used intelligently. Balsa cores have a horrible reputation, and foam cores have a checkered one, mainly due to the construction techniques used where the foam is applied to a layup in a female mold, and expected to adhere by use of a bonding paste in a blind situation. The results are pretty due to the polished female mold surface, but they are questionable at best due to the technique.


I'm looking at foam core construction ONLY because of design parameters that make it impossible to achieve the desired payload per length using plywood. Built using infusion or vacuum bagged with the glass applied directly to the foam, the bond is not in question. 1500 lbs saved in structural weight = 1500 pounds additional payload = a smaller boat to do the same job..... still more than large enough in terms of space. Sandwich construction = higher cost, but smaller boat = lower cost, both initially and on an ongoing basis, easily balancing out the higher cost of construction. Construction is a one time cost..... maintenance is forever. Every time one applies paint, top or bottom, replaces rigging, winches, hardware, engines, buys fuel, pays dockage fees, etc.



H.W.

[Thumbs Up]

Owly, I have read through a lot of your posts and see you were or are considering building in ply/epoxy and looking at payload as a design criteria. I think that you should take a look at my boat which is the Australian Hitchhiker (John Hitch) design. The hulls have a lot of flare. In the photo below, I have a total of forty people on board! In the third photo there are seventeen people on board. https://www.sailboatlistings.com/view/56689

[owly]

Originally Posted by Thumbs Up

Owly, I have read through a lot of your posts and see you were or are considering building in ply/epoxy and looking at payload as a design criteria. I think that you should take a look at my boat which is the Australian Hitchhiker (John Hitch) design. The hulls have a lot of flare. In the photo below, I have a total of forty people on board! In the third photo there are seventeen people on board. https://www.sailboatlistings.com/view/56689

Thanks.... a beautiful boat, and an excellent value, but far larger than what I am looking for. I'm looking at the 30' range, and have even considered Bernd Kohlers KD860, which is only 28. His layout unfortunately doesn't meet my criteria in several ways. Unlike most folks, I'm not stuck on the bigger is better school of thought. I expect to be single handing a large percentage of the time, and so do not need vast amounts of space. For me smaller is better, and 30' is the "sweet spot" except for payload. I'd much rather buy than build, but get what I actually want seems to require that I build ;-(
Ironically, much of what folks regard as "features", to me are liabilities. My target is a small light fairly minimalist boat. Payload is critically important to me for reasons other than carrying a lot of people and their gear and toys, or having comfort and convenience features. On a 30 footer it's difficult to achieve what to me is an adequate payload, but it is possible

H.W.

[Thumbs Up]

OK, thanks for looking. Hopefully I will be looking at a smaller boat soon too... As far as the design of the hulls you might want to look at some Australian sites and include the word hitchhiker in your searches because they are well known "down" there and much smaller ones were built.(John Hitch must have been like the Jim Brown of Australia, most were backyard built but mine is from an unknown boatyard in SA) I questioned why they chose this design (it was built in the late nineties) when more modern hull shapes were already the norm and cylinder cold molding plans were becoming available but it does have some merits. The defining feature of most Hitchhikers was twin furling headsails with a forestay to each bow. (mine is cutter rigged). The hitchhiker hull shapes are dead simple and sort of origami-like. They leave very little wake and with the wide flaring hulls, for each additional inch they are submerged gain increasingly more buoyancy. You do know that Pete Hill's cat is for sale? (Voyaging on a small income), it is 33' but based on the kd860https://yachthub.com/list/yachts-for.../custom/215147

[Training Wheels]

Here’s one I don’t think has been mentioned, I changed all my thru-hulls from bronze to Tru design plastic. All 4 of them!

[Training Wheels]

Oh, and I also got rid of most of my blocks and went to low friction rings.

[Training Wheels]

Did I mention we use backpacking type cookware and silverware?[ATTACH]176842
Full time cruising.

[Training Wheels]

No paper charts. Redundancy with chart plotter, iPad, and laptop.

[mikereed100]

Originally Posted by StuM

Ye gods! Over $13 thousand for a dunny?

And it still weighs more than a Lavac Popular electric at less than $800

[mikereed100]

Originally Posted by thinwater

Low friction rings. I'm changing to them everywhere I don't need to adjust under high load. They even work with polyester-covered line, as long as the deflection angle is not too great.

[4:1 bobstay tackle. Not adjusted under load.]

Nice setup. I would steal your idea, but can't see how you managed to put 2 eye splices in that short bit?