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Old 04-11-2009, 06:22   #1
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Will Vinylester Do or Is it Epoxy All the Way ?

What’s the consensus these days?

Just for the fun of it!
Pretend you’re building your next boat and it’s your last, cost isn’t a factor, but you wanted a cat that is reasonable to single hand with the right systems, say a 50 ft cat

If you really had the choice

Will Vinyl ester do or is it epoxy all the way?
Would you build with carbon/epoxy where you could?
Is it mini keels or daggers one dagger or two?
Feel free to throw in some wish list items as well, go on dream a little!
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Old 04-11-2009, 07:16   #2
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If money is no issue, all fiberglass boats would be build with epoxy and painted with Awlgrip or another LPU paint.

But you must understand that the fibers used are more important than the resin. It's not just carbon vs kevlar vs fiberglass, it's also which type of fiberglass and the build-up of the different types in the laminate. When you use epoxy, you can't use fiberglass mat (the binder in the mat doesn't dissolve with epoxy resin like it does with polyester.... many say that it doesn't "wet out" well with epoxy but the problem is deeper) so there are different combinations of fibers for each resin.

I would go for fiberglass with substantial carbon reinforcements and epoxy resin.

Daggers improve performance and lower draft compared to mini-keels. They also create more work while sailing so for a cruiser it's a compromise.

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Old 04-11-2009, 07:52   #3
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Nice reply Nick that’s setting the standard high! thanks for jumping in!

Let’s roll with that.

Your building it yourself, call it fun, call it stupidity but its all part of the journey.

So carbon reinforcements below the water line? What about else where to save weight

What are your choice daggers or keels? If daggers how do you protect your props and rudders? Would a small carbon protection do the job?

I was at a marina the other day and just down the pen from Jessica Watson’s “Ella’s Pink Lady” , a cat had these funky looking bow protectors made from stainless, can’t help but think that carbon/Kevlar would be lighter and less of a wow factor.
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Old 04-11-2009, 09:21   #4
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I would put carbon fiber reinforcements at all high stress areas. Much of that is above waterline, think about where chainplates (they would be carbon fiber too) attach, cross supports between the hulls and their attachment points etc. etc. I would also have carbon mast and boom, steering wheels etc. Remember, you said price wasn't an issue ;-)

The whole under water deal with props and rudders is something I would first research how every existing 50' cat has done that. I like the idea of kick-up rudders on a cat but never saw that on a 50' one I think. Another option is to engineer a weak point in the rudder so that the lower part can break off while the upper part is protected by a small kevlar fin. (I would not hesitate to throw in some kevlar too when it makes sense).

My bows would be so strong that I would cut through containers with them. I would always add a 2nd full watertight bulkhead a couple of feet behind the first at the bow, making the whole thing like a sacrificial crash area.

I prefer mono-hulls but I like the looks of cats 50' and up. I would go for substantial freeboard, maybe a bit lower at the sterns but still a lot of bridge deck clearance from the sea. With smaller cats that doesn't look good.

cheers,
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Old 08-11-2009, 16:55   #5
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Epoxy all the way.
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Old 10-11-2009, 00:15   #6
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So obviously price is an issue (amongst others, health etc) does any one have a price comparison from any builders between all epoxy or all vinylester?
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Old 15-11-2009, 13:54   #7
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relative pricing varies thru time of course... but we were offered a $15k discount on a 50 ft build for switching from epoxy to vinylester in 2005.

on the topic of fibers, don't forget wood. using cedar + epoxy for the hull will save you enough to fund lots of carbon for bulkheads, beams, chainplates. we guestimate that we saved $30-50k by not having to build molds. independent testing showed that a glass-cedar-foam-cedar-glass sandwich was roughly 50% 'stronger' than glass-foam-glass at equivalent panel weight.
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Old 15-11-2009, 16:06   #8
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Oh I agree... wood-epoxy creates my favorite boats. The only problem is the abresion resistance required for a cruiser and that's where the fiberglass comes in. But we're talking one-off's here because mass production means molds and fiberglass (or other fibers) only.

If my Sundeer would be wood-epoxy, it would be twice as stiff and much faster and lighter.

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Old 15-11-2009, 16:15   #9
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Why not Aluminium.
I used to manufacture sailing yachts out of Vinylester Polyester fiberglass. You will get Osmosis eventually,particularly if you spend much time in warm water.
Epoxy is good but expensive.
I ended up chosing Aluminium.
I had a naval architect draw up the plans, we sent them to an Aluminium supplier, he cut out everything with a cnc router and each part was numbered. All the pieces arrived on a truck.

I used a professional aluminium boat builder.
After seeing them at work I really couldn't recommend DIY.
The boat, 40 ft was completed (shell only) in five weeks.
All up it was much cheaper than I expected.

You must work with a minimium of 4mm (3/8") sheet or the sheets buckle with the welding.

The resale value is also a consideration. Aluminium is well known and respected as a boat builing material, and being professionally built also helps.
You must use insulation in an Aluminium boat and Painting should also be done by somebody who understands painting aluminium boats.

There are quite a number of catamarans in Brisbane Australia bulit with Aluminium
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Old 24-11-2009, 00:38   #10
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Why not Aluminum

Hmmm well there are plenty of nice well built Aluminum vessels out there and I have been on quite a few, but I just find them to be noisy (and cold) but seriously that may just be some cognitive dissonance.
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Old 24-11-2009, 09:53   #11
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why not aluminum?

and while it is an incredibly strong, relatively light build material... the maintenance regimen is CRITICAL. when aluminum boat owners have electrolysis or other electrical gremlins, it's very serious business.
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Old 25-11-2009, 07:33   #12
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@lancelots: That's about money. A couple of inches of foam takes not only care of the problem but also make the sound-level and insulation far superior to any other building method.

@kiapa: Other than replacing the zincs in time, that is not maintenance!? Every serious aluminium boat has a meter with audible alarm to check & warn about a problem. That is a piece of gear checking it for you; compare that to checking for blisters for fiberglass or worms and stuff for wood or rust for steel. A good build takes advantages of the material as where bad builds make big mistakes. The Dashew Cruising Encyclopedia is a very good resource on the subject, an example: bad = drilling holes through the deck for bolting on stuff like genoa tracks or hatch-bases (like done for fiberglass); good = taking a piece of aluminium stock, drilling and tapping it for a track and welding that onto the deck, never penetrating the deck and introducing "sacrificial" material if ever a problem arises, or, for hatches, using cast aluminium bases and welding these to the deck, ending the issue with bedding compounds etc. You will recognize that these decisions are driven by the cost for implementation.

cheers,
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Old 25-11-2009, 08:39   #13
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nick, i think you might be oversimplifying things. aluminum is great bldg material, but taking care of it IS serious business. i've run across four beautiful aluminum boats while cruising, all run by very capable families. it's a small sample... but two of the four had undiagnosed problems that lead to dangerously 'think skins' in spots.

i'll take wood, plastic, with a can of epoxy on board any day of the week.
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Old 25-11-2009, 12:47   #14
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To me the ultimate would be a polyester boat, gelcoated. But there would have to be some (kevlar?) impact resistant patches in places where you can hit something, just in case I will ever hit one of the many things I saw passing me by (empty oil barrels, huge wood logs, etc).

My ultimate choice would be alu, but alu is more maintenance than plastic, so they say.

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Old 25-11-2009, 12:56   #15
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Unidirectionally reinforced cellular composite + Epoxy

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