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Old 02-01-2009, 15:33   #1
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The ideal multihull

If I were to design something from scratch, I would put in some things I've never heard of anyone trying. Here's a starter list. Please feel free to add or comment upon it.

1) No underwater through hulls. Yes, it's radical, but I would want engines that could be raised and lowered from above the waterline. Electric, gasoline outboards, don't really care, but they go up and down above the waterline. Any water needing to come into the boat for dishes, or cooling or heads would go up through a blended in conduit on the inside of the hulls which extends below the water and then penetrate through the hull well above the waterline. Actually one foot above where the waterline would be should the largest watertight compartment be breached. The same would be true for depth and speed inducers, they would be included in small tubes inside the inner hull which go below the waterline but the wiring enters far above the waterline. This doesn't have to be ugly. The hull can be smooth and continuous with the conduits hidden inside the boat instead of outside, just as long at the through hull location is way above the waterline. Think of the headaches this eliminates. Where's that leak? Unless you breach the hull, there is no leak.

2) Watertight compartments. Every cabin you would need to step and through a bulkhead which is high enough to prevent water moving from that compartment to another compartment should that compartment breach. OK, so you step up, big deal. I'd rather have something slightly awkward to enter and know it's completely watertight compartment. I like to be reminded that I'm on a boat rather than trying to live the illusion that I'm in a condomium.

3) no metal below the waterline. Actually if there are retractible engines, then there really is no need for metal below the waterline. Let other boats worry about diving to check their zincs and saildrives.

4) Replaceable striker plate rubrails on the leading edges of the boat. Think of it. they put rubrails mainly to protect against scratches, but not collisions. How much sense does that make? I want normal rub rails too, but make them where they are needed, not just wanted. And make them robust, steel over hard vinyl for shock absorbing type things. False foam bows are nice, but they can't be as strong as steel rub rail and certainly not as easy to repair.

5) Have a dedicated retractible lightning rod extending straight down from the mast. Make sure it's a piece of metal that goes up and straight down from the tip of the mast through the center of the bridgedeck hull to the water. Why don't multihull manufacturers design for lightning strikes? Monohulls do.

6) Redundant field replaceable independent interchangeable units for things like nav lights, deck lights, instruments. Think tacktick instruments evolved to cover more things. Your nav lights with their own solar panels, light sensor and a wireless on and off controls. You loose a nav light, oh well, you grab another one, switch it to green, walk over to the bow and replace the broken one with a light that could be the white all around light, the red and green, or a deck light. All using the same housing but a moveable solar panel, different colored lenses and a movable plastic housing adapter that adjusts where and what angle it shines from. Also have ones that can be used inside, sitting on the rail ready to go. No wires going to anything. Loose the battery bank? Your lights and instruments still work. Oh, now you don't have to worry about wires coming back through leaky conduits. No wires going through the mast either (Tacktick instead).

7) of course all the usual (or what should be usual), accessible side panels so you can see every space of the boat.

8) Solar powered panels built in, sufficient to power everything in the boat. Use the deck space to have solar panels, or better some sort of solar film. Built it in from the start rather than having to clumsily stick it on afterwards.

9) Hatches facing out but not up. Design it so you can get sufficient ventilation and lighting from outward facing hatching and ports in the hulls. Protect from rain every dead light through a lip. Prevent leaks before they start. I've got several leaking hatches on our boat and well, I'm pissed. Maybe it's not rational, but maybe it can be done. I do like the idea though of a clean deck with nothing to leak and nothing to stub your toe on. Just seems a problem waiting to happen to put an opening window on a flat roof. Maybe permantly sealed deck prisms for light and opening hatches in the hulls. I think one of the most esthetically pleasing things is to look into the water between the hulls.

10) it's sort of stated elsewhere, but retractible engines. I want to be able to get the thing out of the water completely. I also want to be able to hoist it using the mainsheet out of the boat and dangle it like a Christmas tree ornament for repair at every possible angle.

That's it for the rant. Now I'll let the bigger winds blow.
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Old 02-01-2009, 17:52   #2
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I like to be reminded that I'm on a boat rather than trying to live the illusion that I'm in a condomium.

Good point.

3) no metal below the waterline.

I have long wondered why we have metal prop struts. Why not just make one up of fiberglass or carbonfiber and glass it to the hull? Eliminate a zinc and a potential leak point.


4) Replaceable striker plate rubrails on the leading edges of the boat.

The Edel H42's have a "bumper" on the leading edge of the hull, similar to what you describe.
http://www.aeroyacht.com/H42/Gallery.htm



Lots of good ideas Schoonerdog!

Mike
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Old 03-01-2009, 02:17   #3
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Hallo Schoonerdog
This is how I started in 2003 to think up a new design for the ideal multihull
The result is the ever improving FastCat 445 with
1. Retractable electric "Motogens"
2. 5 watertight compartments in each hull 3 on the forward bow and 2 in the rear of the boat with a total of 9000 liters volume
3. We have no metal parts under the water line besides the grounding plates and the retractable lightning conductor under the mast. ( standard on all FastCats )
4. bows that can take a hit but if damaged beyond repair they can be replaced and the trip can be continued even if not yet replaced. (Standard on all FastCats )
5. See number 3
6. Tack Tick is standard the idea of Led nav lights with separate solar panels is good but not very praticle and very costly ( switching each one individually will be hard especcially the tricolor on the top of the mast.
7. standard on all compartments
8. Unfortunately panels like this cannot be replaced if broken and the efficiency is very low , only 6 % compared with up to 22% for crystalline solar panels in other words we would have to cover over 3 times as much space for the flexible type. We install 215 Wp solar power standard in combination with one mast head mounted wind generator of 200 watt
9. we do both since there is a lot of demand for both the upward and sideways and I agree being able to see the dolphins between the hulls is fantastic.

10. see number 1 but one step further we make 2 lids in the cockpit floor to be able to remove a plastic bag or replace an anode of these electric motors

Have a great new year

Gideon
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Old 03-01-2009, 05:58   #4
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replacing the huge battery banks with a couple of Lithium-ion batteries should give you plenty of juice and save 50 % in weight.

Koen
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Old 03-01-2009, 08:35   #5
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I've also long believed it is possible and desireable to have no thru-hulls. I actually came up with a solution that, so far, works fairly well. The previous owner installed just one bronze thru-hull, for the head, but I've plugged that and opted for a porta-potty. Aren't those (expensive) composting heads self-contained and a fair alternative?

My hi-thrust outboard does kick up free and clear from the water, and so there is almost no metal below the waterline. For bigger installations aren't those Sillette legs still available?

As for sea water intake to the galley, I've plumbed a retractable hose with a strainer on the end. In an effort to keep things simple, it is powered by a foot pump; but those who like to just turn a knob could use an electric pump.

It sounds like Gideon has addressed these issues pretty well.

Michael
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Old 04-01-2009, 02:09   #6
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Hallo Koen we actualy use Lithium Ion Batterys type U 24 made by Lithium Phosphate Energy Storage Solutions - | Electric Vehicle Battery - Li-Ion Batteries
12 for the propulsion side and 6 for the service side the total weight of these units is
278 kilo compared with over 800 kilo for AGM units and we have more energy available with the lithium units , they are much more expensive but an expected lifetime of 3000 cycles compared with 500 for AGM and if that is taken into account they are even cheaper.
The actual weight saving is around 72 %

Greetings and a happy new year with lots of sailing.
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Old 04-01-2009, 03:59   #7
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I go
1) no through hull fittings, including dagger boards and rudders
2) free standing rig so a downwind squall doesn't have to be a nightmare
3) No metal except for the electrics
4) Bruce number of near 2 for cruising with high righting moment and able to keep full sail up to 25 knots,
5) Less than 2 tonnes
6) at least 15m
7) High prismatic coefficient
Still a few points being sorted out but a Harryproa satisfies most of these at moderate cost as well as having quite a few other safety factors.
I'd like to join in that last message
Happy New Year and good sailing
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Old 04-01-2009, 04:09   #8
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No great big square lumps sticking out from the inside aft hulls so as to give the impression of huge amounts of internal space yet advertise the fact of slim hulls, as all this does is create bad slamming and an uncomfortable ride and looks ugly.
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Old 04-01-2009, 05:49   #9
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Now you are talking out of your nose , Ireaney , the proof of the pudding is in the eating and you never had any , you have never seen or sailed a FastCat.
It does not slam , not even the bridgedeck or the extended bunks.
Beauty is in the eye of the beholder and I love these extensions since they create lots of room and we hang the electric motors of them.

Have a great year and I hope you will find your cat some day !!!
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Old 04-01-2009, 06:28   #10
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Our Hull length to width ratio is : 12.5 on the waterline for the FastCat 445 and 1:14 for the new 555.
Most cruising cats have a water line width to length ratio of less than 1:10 and a few do not even come above 1:8
In the Netherlands we have a saying
The best captains or skippers are always on shore , does that have a familiar sound ? or is there a similar English saying ?
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Old 04-01-2009, 08:51   #11
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Now you are talking out of your nose , Ireaney , the proof of the pudding is in the eating and you never had any , you have never seen or sailed a FastCat.
It does not slam , not even the bridgedeck or the extended bunks.
Beauty is in the eye of the beholder and I love these extensions since they create lots of room and we hang the electric motors of them.

Have a great year and I hope you will find your cat some day !!!
Gideon, a bit touchy here aren't we, I didn't mention your boats there are several boats with these so called extensions, but while we are on the subject, what you are saying is contradictory to what I have heard from more than one person.
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Old 04-01-2009, 08:59   #12
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In the Netherlands we have a saying
The best captains or skippers are always on shore , does that have a familiar sound ? or is there a similar English saying ?
Yes, in England we say 'When we pay for a boat and it has a few expected teething faults, we hope that they are fixed within 1 month and not still unfixed 8 months on and increasing'. or 'Caveat Emptor'
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Old 04-01-2009, 08:59   #13
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I have sailed the FastCats well over 60000 NM and no bridge deck slamming or slamming of the extensions has occurred with exception of the odd wave.
it all has to do with weight.
a light weight cat follows the waves better.
I do not know of anybody that has sailed a FastCat and made that comment.

Greetings

Gideon
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Old 04-01-2009, 09:02   #14
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It is 5 months not 8 and we have had to make many changes on request of the owners like making the Bimini higher and many other items all changes cost time/
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Old 04-01-2009, 10:07   #15
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It is 5 months not 8 and we have had to make many changes on request of the owners like making the Bimini higher and many other items all changes cost time/
Gideon

I am not going to argue with you as you are always right, but I will just finally add that I HAVE SEEN THE LIGHT as many others have that I am in contact with, but unfortunately there still seem to be some poor gullible souls that will believe everything that salesmen tell them, but I know exactly where NOT to spend my money.

No more posts from me on this issue.
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