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Old 24-05-2014, 14:53   #76
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Re: SMG 50, its Like they were Reading my Mind

Why aren't there more catamarans with the A mast design. The performance speaks for itself and it's so much easier to use/ maintain.

I wouldn't be surprised if this boat turns out to be faster than the african cat 605 greenmotion i believe.
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Old 26-05-2014, 03:51   #77
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Re: SMG 50, its Like they were Reading my Mind

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Originally Posted by Defyant View Post
Why aren't there more catamarans with the A mast design. The performance speaks for itself and it's so much easier to use/ maintain.

I wouldn't be surprised if this boat turns out to be faster than the african cat 605 greenmotion i believe.
SMG50:
SA/D (main + jib): 25.1
Bruce Number: 1.26
Hull Speed 15.1 kts

Fastcat 605 (heavier version):
SA/D (main + jib): 37.6
Bruce Number: 1.54
Hull Speed 16.6 kts

SA/D and Bruce Number calculated here, hull speed calculated here.

It isn't really a fair comparison - the Fastcat is 3m longer at the waterline and has a mast 8m taller.
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Old 26-05-2014, 14:11   #78
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Re: SMG 50, its Like they were Reading my Mind

So the fastcat should perform better right? Anyway that didn't answer my question

Sent from my Nexus 4 using Cruisers Sailing Forum mobile app
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Old 03-06-2014, 18:09   #79
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Re: SMG 50, its Like they were Reading my Mind

FOR ANSWERS TO QUESTIONS POSTED HERE ABOUT A-FRAME RIGS, SEE:

DAMSL Catbird Suite

I'm way behind on my reading of this forum, but it seems that Deckofficer has aroused quite a bit of interest in the A-frame rig. To answer just a few of the questions I've read so far:

- Upwind performance is very good, even with a relatively small main. Sails on wires or luff spars are simply more efficient; and, overall rigging drag is less than on a conventional rig capable of carrying equivalent sail area, because when everything is added up (mast section size, wire size, amount of wire) there is simply less surface area, made possible because better geometry gives greater strength with less material, and also enables better rig tuning with less stress.

- Reaching and downwind performance are superior to a comparable conventional rig.

-The beam of a cat, combined with deployment of all sails on the windward side (as in my design but not in the SMG 50), enables innovative sheeting so that ideal sail shape can be maintained on all points of sail, NO BOOMS NEEDED.

- On my boat, Catbird Suite, everything (strength to weight, strength to cost, strength to drag) is better than in a conventional rig (with fully battened, big roach, monster main) by the same designer (the late Malcolm Tennant).

- The rig is stronger, with easier handling, and is safer overall.

Re that ancient false assumption that always pops up about anything relatively new but not yet popular: If the design is so good, why aren't there more of them? Answer: The vast majority of sailors are incredibly conservative, conformist souls, even the relatively few who have finally seen the light re multihulls vs. monohulls. Also currently affecting the particular boats discussed in this thread, the SMG 50s, as well as my boat, there is still a global depression in sales in this price range, for boats of all descriptions, and that depression has been persistent for the entire time that these boats have been on the market.
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Old 03-06-2014, 18:20   #80
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Re: SMG 50, its Like they were Reading my Mind

Thanks for the input High Tacker. You sound like a forward thinking guy and might even embrace a diesel-solar electric hybrid with an all electric galley. No propane, single DC gen-set and good amount of solar. No need for heavy AC gen-set if you have a large LiFePO4 house/propulsion bank and a large pure sine wave inverter.

Are we on the same wavelength?
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Old 03-06-2014, 18:37   #81
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Hi Deckofficer,

I'm certainly on your wavelength as that is exactly what we are considering for our FreeFlow 46 bluewater cruiser, for all the reasons I have previously written about.

Still working through the cost-benefit analysis and 10 year total cost of ownership of the Torqeedo Deep Blue 40HP shaft drives vs diesel Yanmars.
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Old 03-06-2014, 18:46   #82
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Re: SMG 50, its Like they were Reading my Mind

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Hi Deckofficer,

I'm certainly on your wavelength as that is exactly what we are considering for our FreeFlow 46 bluewater cruiser, for all the reasons I have previously written about.

Still working through the cost-benefit analysis and 10 year total cost of ownership of the Torqeedo Deep Blue 40HP shaft drives vs diesel Yanmars.
Got my interest!

Weight?

Your choice of the 40 hp Torqeedos vs the 80 hp has me wondering. Both require the same high voltage DC batteries and are the same weight.

Nice thing about electric motors, feed them twice the current at any given voltage and they will produce twice the power. Could be handy in certain short term challenging conditions.
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Old 03-06-2014, 19:00   #83
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Re: SMG 50, its Like they were Reading my Mind

Yes, deckofficer, we are pretty much on the same wavelength. I think you've had a look at my website:

DAMSL Catbird Suite

You'll see there that I have long been into electricity from wind and solar power, and I had planned at one stage for electric drive but decided to go with two diesels and ordinary direct drive because that's what all sailors are used to and I had run out of money to experiment with and really needed to sell the boat. You'll understand if you slog through my long-winded explanations of the experimentation I had already done. I don't think it could be put better than my then soon-to-be ex-wife's comment about the wind turbine project: "Why are you doing this? This is something the government should be doing. YOU don't have enough money!"

But I allowed, in the modified design, for electric motors to be added later, along with more solar panels, a smaller wind turbine, and more batteries. The boat has some of what you like, substantial battery capacity, inverters, a mostly electric galley, but I do like a gas cooker, and I already have a 15kva AC diesel generator which by itself could drive the boat, or air conditioning if you want. The two main motors are 80hp Isuzu diesels and electric motors can be added behind them. So, what the hell, buy my boat, and you'll have back up for your back up, on top of having two boats in one, and a lot more boat and more and better sail power than the SMG 50. By the way, that forward cockpit looks nice in pretty pictures taken on an extraordinarily nice day in the Med, but I'll stick with my big and very sheltered aft cockpit, spray free and there ain't no mast in front obstructing the view neither, and nary a boom to bash me or carry away the rigging. Accidental jibe? So what?
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Old 03-06-2014, 19:03   #84
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Re: SMG 50, its Like they were Reading my Mind

On the same page with you also, love the idea of all electric cat. Few questions, why Torqueedo and not one of the "as" reliable/less costly electric options for propulsion? Also, I've wondered if having a separate bank for each motor would be reasonable. Less the fuel and diesel engines, there would be plenty of room in each hull for this. Would it complicate the system or provide a safety/redundancy? I love all the info you experienced guys contribute to this forum

I really like the FF46 also! Nice choice
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Old 03-06-2014, 19:07   #85
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Re: SMG 50, its Like they were Reading my Mind

Deckofficer;

I've read all your posts on electric propulsion, so we are definitely on the same thought process on this topic.

The boat will cruise at about 10 tonnes (22,000 lb.) with all manner of cruising gear, SCUBA compressor, Washing machine (for the Admiral), aluminium RIB & 15 HP 2 stroke Yammie, etc etc. The hulls are very slippery (12.5:1) and weight is carried centrally. Our figures show that twin 40HP is more than enough given the torque characteristics of electric propulsion to move the boat in adverse conditions such as tidal flow from lagoons, rivers, big winds etc. We have no desire to waterski using the 80HP Torqeedo's and would rather save the amps. It would be fun though to drag race a Gunboat sometime, wouldn't it?

But I am very much on the learning curve, so would really like to engage with you on details. Can take it to email if you want to, so we don't bore everyone to death with electric propulsion musings which just attract the "it won't/can't/ mustn't work" crowd here on CF.
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Old 03-06-2014, 19:12   #86
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Re: SMG 50, its Like they were Reading my Mind

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Deckofficer;

I've read all your posts on electric propulsion, so we are definitely on the same thought process on this topic.


But I am very much on the learning curve, so would really like to engage with you on details. Can take it to email if you want to, so we don't bore everyone to death with electric propulsion musings which just attract the "it won't/can't/ mustn't work" crowd here on CF.
I would be very interested in following a thread on your ideas for electric FF46. Promise I won't be bored
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Old 03-06-2014, 19:37   #87
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Re: SMG 50, its Like they were Reading my Mind

Hi Blue Skye,

Sorry, I didn't see your post until after I sent my last one.

The reasons for Torqeedo are many. I have been researching this for over a year (call it a hobby if you want, my Admiral calls it an obsession, but let's not go there Also I have been in contact with their technical people & executive who are awesome in their breadth of knowledge in this field, and vision for what they are trying to do. Innovation counts with me, as long as it has a healthy dose of robust reliability in the mix. This is new ground, as everyone acknowledges, but not exactly as bleeding edge as some would have you believe.

So hear are some of my thought summaries on why Torqeedo:

1 Industrial electric motors vs consumer level design and engineering. There is a world of difference in reliability between the two types. Industrial electric motors can run 24x7x365. Think electric generation plants. In our application on cruising sailboats that is overkill, but it is still meaningful when you want to keep your liveaboard boat for 10 years plus and not be bogged down in maintenance costs, let alone lack of technical expertise to service yourself...

2 Motor efficiency. It is really important that the maximum efficiency is achieved to get useable long distance steaming from your LiFePO4 bank.

3 Torqeedo have built in diagnostics so it will tell you where there is a chafed wire, or loose connection etc. If you are not an electrical engineer, which I am most definitely NOT, then I need to be able to diagnose problems if I'm in Nukafalovatapukakki lagoon in the middle of the Pacific somewhere.

4 Related to above is warranty. I will not say too much here on public forum, but let's just say Torqeedo know as a cruiser you are in the middle of nowhere and any problem is serious. They are committed and will stand behind their gear. They have demonstrated that to my satisfaction

5 There is a pipeline of really good things coming....and they have a total systems approach that is related to the point above. Have a think about that. What is involved in a total electric propulsion system? Yep, take energy in (by various means), store it, then use it.

So at this point they are ticking boxes, but it is a very active field so I'm open to anything.
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Old 03-06-2014, 20:56   #88
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Re: SMG 50, its Like they were Reading my Mind

I'm the OP of this thread and I never care it a thread drifts, but if you want, there is a thread on electric propulsion for catamarans here. Electric Propulsion on Catamarans
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Old 03-06-2014, 22:50   #89
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Re: SMG 50, its Like they were Reading my Mind

OOPS quite right, sorry for the drift.
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Old 03-06-2014, 23:00   #90
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Re: SMG 50, its Like they were Reading my Mind

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OOPS quite right, sorry for the drift.
Like I said, I never care if my thread drifts, its cool.
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