CNC Plans not Included

Discussion in 'Multihulls' started by jorgepease, Sep 19, 2016.

  1. UpOnStands
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    UpOnStands Senior Member

    reinforced my dislike of reverse bows on "small" hulls. What is wrong here with all the spray? The stems are too thick?
    edit: oops 46 foot is not that small
    South African boatbuilder sells world’s lightest catamaran - IBI News http://www.ibinews.com/news/south-african-boatbuilder-sells-worlds-lightest-catamaran-4444

    check port bow at 9:13 mark
     
    Last edited: May 10, 2017
  2. jorgepease
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    jorgepease Senior Member

    This is too long of a post but ...

    I don't like the look of that Schionning much either, It's also devoid of enjoyable spaces. If my only motivation is to go somewhere fast then I will take a plane.

    As for the design spiral, that is a very general rule, it can't apply across the board because all I did was put a 50 foot boat on 60 foot hulls. if I shrink this boat to 50' all I eliminate is 10 feet of empty hull and 5' of bridgedeck and roof which is relatively little weight and now the boat is longer and leaner which compensates to some extent, the need for a taller mast.

    Design has to be considered in the spiral. If all you have is a main mast beam and a transom beam then those two beams have to compensate for all the loads put on the hulls making them extra heavy. If you spread that out over several beams, including adding some structural strength with the roof, then the beams can be lighter and the boat will probably be stronger. It will still be heavier but not drastically heavier.

    As for the unstayed mast, I should have plenty of bury if you count the roof which can be incorporated into the structure. From everything I have read, if the boat is new construction it can be engineered without any tradeoffs as compared to a stayed mast and actually the benefits seem to weigh in favor of unstayed.

    Unstayed masts make sense on this boat because you can sail at 95% potential on all points without fiddling with the sails, I can't see my sails so that makes sense. It's a long lean and light boat so I get an easy to sail boat that also performs pretty well and on the downwind where most of my sailing will be, it will excel. I am thinking the aero rig type but unstayed whichever one is best. I have read a whole lot of threads of people who have them and nothing bad so far.

    I checked out Rod Denney's engineer - etamax Etamax Engineering - Composite Materials Engineers http://www.etamax.com.au/ and I think they would be very suitable for this boat. I am shying away from the well known designers that feel it's their duty to make you feel stupid.

    Getting very close to having cash in hand and starting the process so will contact them soon.
    60_rev8.jpg
     
  3. groper
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    groper Senior Member

    Your learning what all catamaran designers have been learning for decades... This is why the majority of the designs on the market are the way they are! Where your going to end up is yep about where they are. Essentially youll only be customizing the layout and styling but its going to be essentially the same structurally as all bridgedeck cats.
    Your styling so far looks alot like something Kurt Hughes - not including the bridgdeck structure. Have you looked at his designs?

    Whats your budget for this Jorge? Do you have a budget?

    Also, at some point before getting too carried away with the layout - you should do a weight analysis and find the CoG inc all your fitout items and equipment. This is quite time consuming as there is HEAPS of stuff you need to include.
    You should be able to assign densities and thicknesses to all your surfaces in your software. Use it to find the CoG of the boat structure in your analysis and remember to make concessions for extra laminates, windows and doors etc etc...
     
  4. jorgepease
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    jorgepease Senior Member

    Yes I see why they do things the way they do however there is quite a bit of freedom beyond just layout - Higher Bridgedecks, Leaner Hulls, Minimum Fitout Solar Roof.

    Honestly I don't think Open BD Cats, like what you want, are suitable for Ocean Crossings. Sure you can do it but it's not going to be pleasant and I will arrive at near the same time you do because most of the time, seas aren't going to permit you going 25 knots so it really boils down to what you will use the boat for. Check out that video you posted, you're going to get tired of being soaked :) ... I want comfortable performance and independence from fossil fuels.


    450K , I can go another 100K if need be, but going to shoot for 350K. With an unstayed mast I think that will be possible as it knocks off a huge amount of costs on the rigging and labor to rig. Materials for shell are a fraction of this cost, fit out, including appliances I can pay out of my wallet. The solar roof is high but I am confident I can get the price of the solar panels way below $800 per panel and my system can come in more around the 80-90K mark. Mold is not going to be as costly as you say, most of it is direct to female.

    Heck no! I'm not as smart as you on that stuff Groper!!! Let the engineer do it, why in the world would I do that. I expect them to design a boat which looks like my drawings with lean hulls and high bridgedeck. How they arrive at the final product is their business unless it complicates my work flow, otherwise I keep my mouth shut and build what they draw.

    BUT providing the engineers with a 3D mockup is going to be helpful because in less than an hour they will be able to scan through the model picking out all the issues before coming up with ideas for best approach. As you say, it's pretty standard but if a pic is worth a thousand words a 3D pic is worth a million. Much better than me, who doesn't even know the proper terminology to try and explain.

    Check out my cockpit, pretty luxurious no? It's just a cushion on top of the interior ceiling and it's at regular sitting height with no cut up spaces inside. Looks like something Gunboat would have!!!!! 60_rev9.jpg

    Also, I have a few very wealthy friends. One family is going, all 24 of them to Croatia next year to charter a couple of cats for a week. I had dinner with him last night and he is excited about possibly owning one, of course I sold him on mine. Today I got an email from another friend who I sent the pic too and he replied he would like to be involved. Money is not my main concern but because my uncle complains about how the boat industry all of a sudden became very expensive, I want to try to build cats which are of very good value. Not cheap, just the best bang for the buck.
     
    Last edited: May 10, 2017
  5. jorgepease
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    jorgepease Senior Member

    Cutting the roof back was a good call, not only does it avoid being ripped off in the event a big wave crashes on the foredeck, it is way more proportional and I can add solar panels over dinghy if needed.
    RS1.jpg RS2.jpg
     
  6. groper
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    groper Senior Member

    here you go Jorge - check out this 59ft`er - found it coutesy Doug lord... great walkthroughs so you get a feel for the size. Your boat is about similar i reckon...
     
  7. rob denney
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    rob denney Senior Member

    Suggest you do it sooner rather than later. Etamax are flat out in both the design and build departments. Peter (Etamax boss) really knows his stuff, is easy to get on with, builds excellent products, but tends to over commit. Send the details to sales@etamax.com.au to organise a quote for the engineering and build of any of the components.

    Information required to design the mast: the loaded weight of the boat, the beam, height between bearings, boom height and sail plan.
    To design the support structure: the layout of the deck and bridgedeck.
    The 3d drawing may not be worth a million words, but it will make the job a lot easier.

    Unstayed masts make sense on all cruisers and some racers, but I would sacrifice some of your solar panels for hatches that allow you to see the sails. You won't spend all day looking at them, but when you do want to see them, it will be better than having to go outside.

    Unstayed masts suffer upwind partly because they are so wide, although modern cat masts with double diamonds and shrouds are as much, or more windage. There are a couple of solutions to this. You could make it a wing mast, which is more expensive, can be lighter and may (some have problems, others don't) cause the boat to sail around an anchorage and be harder to control in a marina when the wind hits the mast at the right angle on a windy day. OR, you can ensure the sail is on the lee side of the mast, which reduces the turbulence on the important side of the sail. Have a look at a leading edge inflatable kite surf kite to see an example. This can be done by rotating the mast, which is another chore each time you tack and puts high loads on the sail and track. What I have done on Bucket List is to lash the sail to the mast, saves a lot of weight and cost (tracks, cars and mast bearings) but is not as neat. So far, it sits tight against the mast on the lee side. The other part of the performance equation is the bend. This is a good thing in a squall, not so much in a race. An advantage of wing masts and sails on the lee side of the mast is that the mast can be wider, and hence stiffer in the top sections.

    As for cost, I agree an unstayed mast will be cheaper if the boat is designed for it. Carbon is less than $US 40 per kg bought in bulk. Tow about half as much. The mast on a multi with righting moment of 18 tonne metres (6 tonnes boat weight, 6m wide) weighs 120 kgs, of which about 60% is uni carbon. At $US40/kg (been a while since I made a bulk purchase, probably less now), this is $2,900. A stayed carbon mast would be maybe half the weight, plus fittings, spreaders, stays and their attachments on the boat, much of which will be custom made, all of which will have to be installed. And maintained.
     
  8. jorgepease
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    jorgepease Senior Member

    I've seen that video before, yep it's really similar ... No question it's big :) but very nice. It looks beamier than mine though and the hulls must be wider to get two single bunks side by side, hard to say with that wide angle lense. I didn't see one at the Miami Boat show, would have been nice to be able to get on and check it in person.


    Great information, thanks! I will contact him soon.
     
  9. jorgepease
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    jorgepease Senior Member

    I knew it was wider across ) ... I like this boat alot but it def is bigger hulls, wider across and has way more fitout than I have planned.
    Look at the draft with boards up 5.12 feet, damn, might as well stick a keep on there.

    Architect: Chantier Catana
    Manufactoring process: Carbon Twaron infused foam sandwich
    Overall length: 58.73 ft
    Water line length: 58.73 ft
    Beam: 31.14 ft
    Light displacement: 18.9 t
    Draft boards up: 5.12 ft
    Draft boards down: 12.3 ft
    Mast clearance: 86.84 ft
    Mast length: 79.94 ft
    Main sail area: 1302.43 sq ft
    Up wind sail area: 2185 sq ft
    Down wind sail area: 2604.87 sq ft
    Engines power: 2 x 110 hp
    Fresh water capacity: 211.34 us gal
    Fuel capacity: 211.34 us gal
    Structural warranty: 5 years
     
  10. groper
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    groper Senior Member

    Yep... did you notice it was motor sailing in the spoof video? Hahaha.... you can see the exhaust flume in one of the shots...
     
  11. jorgepease
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    jorgepease Senior Member

    I did notice that, shame on them. o_O
     
  12. jorgepease
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    jorgepease Senior Member

    Edited
    Idea for an unstated mast to help into the wind performance by a little, I'm sure it will be shot down but here goes ... What if unstayed masts had a cable that could be tensioned and untensioned to increase or decrease stiffness.

    The cable would run from base of mast up to an outrigger not too far up, where it's still stiff, and then to top of mast. If it's a rotating mast you could do it on at least 3 sides, though I don't fully understand the issue.

    Cranes have this feature to support the boom
     
    Last edited: May 13, 2017
  13. jorgepease
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    jorgepease Senior Member

    Wouldn't be this big, could this stiffen the mast enough to improve performance like a forestay or even just improve a bit. outrigger.jpg
     
  14. groper
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    groper Senior Member

    Lol- Yep but then you dont have an unstayed mast anymore do ya!
     

  15. UpOnStands
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    UpOnStands Senior Member

    Main sail might get in the way?
     
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