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Old 24-01-2008, 04:47   #91
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Are you going to build in female moulds? If so they will need to be flawless - black will show up every tiny defect (as well as being hot as hell) If you're going to build over frames or male moulds, be prepared to spend a large portion of your life (or budget) sanding and fairing.

Have you spent any time in the tropics? Black is the absolute last colour I would choose. Unless you want to be able to do barbecues straight on the deck.
A black hull is very hot but a black deck would be unbearable. A black hull can easily reach 170 degree F and if you are using foam construction the extreme heat must be considered. Many foams can't take it and will delam.
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Old 24-01-2008, 04:55   #92
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Power - A deisel electric drive really starts to make sense when you look at efficiency. Latest technology outperforms mechanical systems and there are also benefits in prop revs.
Forget battery capacity other than a half hour at 5 knots. i.e. out of the marina. You'll need generators after that so install two, small as you can get in diesel, to do the domestics and top up after leaving the marina.
BUT you'll still need sufficient diesel and prop power to motor. The US boaters seem to motor for days at a time and that burns a lot of fuel that you have to carry, then add another three days reserve fuel. HEAVY. If it's a flat calm then a twenty horse genny will drive a slippy boat along way in a day. If there's too much wind you can recharge off the props but is it worth it? The number off days when you wont be driving as fast as you can are limited and you don't want extra drag if you beating into wind anyway. Ask a green boat!
Once you've got electrikery all the domestic kit becomes really cheap, very reliable and easy to replace.
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Old 24-01-2008, 07:41   #93
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First - he was totally committed to the rear set mast on the Prouts, and, by the way, Ron Underwood, ex MD at Prout and now at BroadBlue, has re-introduced that system for the BB385. Benefits are thoroughly explained elsewhere.
You may also want to look at Brian Eiland's site. He is a big fan of the mast-aft rig.

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Old 24-01-2008, 09:32   #94
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FHRussell. Very interesting. Difficult to fault his logic. Particularly suited to 55 footer where sheet loads get high, and circum where crew get tired.
Note the rear stays too, and perhaps this would also suit an A mast for lateral stability and a clean leading edge to the rear most (main) sail.
Minimum of rigging then, minimum interference from the mast. Why not prop the A from the front of the cabin and extend that to support the top of the main sail?
No fixed rigging at all then!
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Old 24-01-2008, 11:52   #95
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A black hull is very hot but a black deck would be unbearable. A black hull can easily reach 170 degree F and if you are using foam construction the extreme heat must be considered. Many foams can't take it and will delam.

This is my biggest worry. I really want to have the hulls and deck black. I want the Bridgedeck to be a dark red.

I'm after any advice that people can give. I know you can get different foams that are more resilliant to heat but i'm still worried that these would delaminate. My next worry is that you wouldn't be able to walk on the deck due to the temperature.

It's probably a dream that I will have to give up on and have the deck if not the whole boat a different colour.

I know that black requires the surface to be perfect or it will show any imperfections up. I'm prepared to do the sanding to ensure the surface is smooth, afterall this is going to be my home.

On the construction method I'm looking at doing something similar to the Farrier Vertical Foam Strip building method.
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Old 24-01-2008, 13:35   #96
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The design seems to be all compound curves. Be prepared to spend a FULL YEAR just on fairing and sanding. If you want to paint it black, then even longer. And that's only the exterior I'm talking about. The insides are even harder to get smooth. (You can hide a lot with liners, but they weigh a lot more than paint.)

A friend of mine started building a 40 foot cat over a year before me, using vertical foam strips in female frames, using resin infusion and vacuum bagging. Working full time for 3 years he now has two hulls, which he is still fairing. I aim to be launching in the next 4 - 6 months. And my boat is around half the volume again of his.

Joli, you're dead right about the black decks being unbearable - we had teak decks with black caulking on our old boat, and on a hot day you couldn't walk on deck barefoot. You could actually get first degree burns from the caulking.
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Old 25-01-2008, 04:55   #97
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Ok, I might have a solution to the colour issue. It will be the paint job will cost a fair bit of money but it will allow me to have the boat black, well when the surface temperature is below about 25degrees C.

Found on the internet a paint that changes temp when its warm. This will allow me to have the boat as black when the temp is low and then as it heats up the colour will change meaning that the sun won't be absorbed as much. I've got to check and ensure its suitable for use with boats, but as long as its used above the waterline i can't see what the issue would be. Only issue is cost, but i'm hoping to inly build one boat so why not spend the money as i'll only be doing it once.
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Old 25-01-2008, 05:31   #98
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Found on the internet a paint that changes temp when its warm.
In my limited experience, most things change temperature, when it's warm (vs cold)
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Old 25-01-2008, 05:46   #99
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Ok, I might have a solution to the colour issue. It will be the paint job will cost a fair bit of money but it will allow me to have the boat black, well when the surface temperature is below about 25degrees C.
Maybe paint a sample and do some testing? Measure the temp in the noon day sun. As CC44 said even caulking in a teak decks will become extremely hot, hot enough to burn. We re-painted the deck on one of our boats with a very light grey and it too became uncomfortable. Maybe 120 F?

Also, as CC44 said the amount of fairing you need may take a very big chunk of time, the concave curve is going to be most problematic to get fair. It will be very difficult to work any sander into the area and almost impossible to longboard. Molds are convex but are always pulled from a plug for this very reason. Plugs can be faired since they are convex.

Pretty design though.
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Old 25-01-2008, 05:50   #100
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I aim to be launching in the next 4 - 6 months. And my boat is around half the volume again of his.
Thats great, I'll bet you'll be ready to lay the sanders down for a bit after you complete the build. The repeat process of filling and fairing gets tiresome but your results look very nice.
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Old 26-01-2008, 03:57   #101
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Sorry. Meant to say paint changes colour with temp. Think it changes coulour at about 24 degrees C or 75 F.
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Old 26-01-2008, 04:01   #102
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Maybe paint a sample and do some testing? Measure the temp in the noon day sun. As CC44 said even caulking in a teak decks will become extremely hot, hot enough to burn. We re-painted the deck on one of our boats with a very light grey and it too became uncomfortable. Maybe 120 F?

Also, as CC44 said the amount of fairing you need may take a very big chunk of time, the concave curve is going to be most problematic to get fair. It will be very difficult to work any sander into the area and almost impossible to longboard. Molds are convex but are always pulled from a plug for this very reason. Plugs can be faired since they are convex.

Pretty design though.

I'm hoping to get a model made of the boat either through work or uni. I'm going to order some of the paint and use it on the model. Due to my location I'll have to place the model under a heat lamp or something and then take readings. Iknow it won't be fully representative but it should give me a good idea.
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Old 27-01-2008, 16:06   #103
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Hello Steven Prince,

I just read your thread. Very nice. I also thought the same about 2 years ago and have just recently "almost" completed my own design. How long have you been on the job of designing her and how steep was the learning curve? I have to tell you that the mathematics involved is incredible and I take my hat off to those that do it for a living.

Have you modeled your lines along the lines of the Shuttleworth 35 Tektron? He is an excellent and reputable designer. Those trademark lighbulb shapes just make sense. I used the concept in my design.

Check out the study plan. It isn't fully completed yet and I just scaled the design to 1:12 to make a model to study, but it will give you an idea. If I can be any help, let me know.

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Old 27-01-2008, 18:19   #104
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I too have not found the perfect boat but building one is not something I want to tackle. Based on my experience sailing and lounging on many boats this is what I would consider. Put enough sail on her to scare yourself but be able to reduce quickly, the Manta has a very slick reef system for the main and I would use a cutter rig with both headsails on furlers to facilitate reducing that area. That set up would be more involved than the camber spar/cont. jib sheet, all lines to the helm setup of the Manta but would increase your sail options. I fly a "manual" spinnaker and the initial setup is time consuming but I can probably douse it with the sock faster than you can furl it but involves getting out on deck.

Minimize electronics, batteries and Romex to save weight, I think most modern cruising cats have an excess amount of Romex running through them. Heavy and expensive. Install something more than idiot light for oil pressure/temp.

Have a cockpit similar to the Catanas but with a helm that is inside. Basically a walk thru to the steps but with the helm of a Manta. I consider being able to see all 4 corners from a protected helm a necessity; why there are helms out there with limited visibility is beyond me. If you are cruising with the wife a double helm seat is nice. I also like the hatch type door vs. the sliding door. Have your interior nav station line of sight from the helm (thru the door) if you need to communicate with your navigator and/or to minimize steps between the two.

If your hulls allow it, keep a small space around the beds (like the bigger Lagoons) to facilitate getting in and out. Work in a sleeping space above the hulls (for rough nights at anchor) and away from the engines for giving some one a place to sleep while underway.

My wife is a gourmet cook so I would not skimp on the cabinets or sink. Build square corners into your couch so you can lean up against a side with your feet up.

Thats all I can come up with for now but there's more.

Good luck, TV
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Old 28-01-2008, 04:01   #105
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Hello Steven Prince,

I just read your thread. Very nice. I also thought the same about 2 years ago and have just recently "almost" completed my own design. How long have you been on the job of designing her and how steep was the learning curve? I have to tell you that the mathematics involved is incredible and I take my hat off to those that do it for a living.

Have you modeled your lines along the lines of the Shuttleworth 35 Tektron? He is an excellent and reputable designer. Those trademark lighbulb shapes just make sense. I used the concept in my design.

Check out the study plan. It isn't fully completed yet and I just scaled the design to 1:12 to make a model to study, but it will give you an idea. If I can be any help, let me know.

J
Hi J.

I've been working on the current design for about 4 weeks, but I had been working on a different design before that but was not happy with the look. Before these boats I had been designing a 45ft monohull but I finally decided that I would look into a catamaran properly rather than just going of the magazine articles warning ppl away. Once I started looking into Cats I realised there many advantages and was sold.

I've read through part of your thread, haven't managed to read all of it yet. I have to admit that I haven't looked at the mathematics yet. I've mainly been trying to get a boat that I like the look of. The program I'm using to carry out the design allows for very easy manipulation. I believe that I currently need to move the Centre of Buoyancy slightly further forward by 300mm but I'll wait till I've finished the design so that I can apply the materials to the hull and check where the centre of gravity is in relation to the centre of buoyancy.

I've modelled my boat from a variety of designs but the biggest influence has been Darren Newton at Dazcats, particularily his D15R. I'm hoping to get in contact with him soon and see if he'll help with the design and eventual building of the boat.

I'm currently hoping to get a scale model made, although it'll be a lot smaller at 1:100. I hope to get a few made as the design progresses to show the different stages. The final model will be painted with the same paint as the main boat and will be used for carrying out test. The final model will be larger to show the details more clearly and to allow for some testing.

I was wondering what you have used to work out the hydrostatics.

Steven
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