CNC Plans not Included

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

  1. jorgepease
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    jorgepease Senior Member

    Could hulls just be flat on top, no extra level like the SIG and FlyingFish have. I have about 6 foot 8 inches of headroom, more than needed starting about 2 foot up from bottom of hull. That could be reduced by a bit but let's say at highest point you have 6 foot 8 inches of windage. That doesn't sound like that much.

    I laid out the different levels trying to keep it as clean as possible. My goal is to be able to get into the beds from the sides and to have tender stow away under aft deck between the beams.

    The dashed lines are where I figure structural beams would be since there is no salon.

    Cockpit is 11 foot x 14 foot with over 3' of protection front and sides and aft deck is 11 foot x 8 foot and it's almost 2' below hull sides.

    I put a hydraulic helm in cockpit behind mast but it's tiller steer with one protected helm somewhere.

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    Last edited: Dec 20, 2016
  2. jorgepease
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    jorgepease Senior Member

    Actually correction to the deck size it's 13 x 18 and 13 x 14 or 22 feet x 13 feet. My office is 20 feet by 13 feet, man that is one spacious deck!!!
     
  3. groper
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    groper Senior Member

    Sorry for the late reply, been so hectic lately...

    I've never seen your idea of the raised rear deck with dingy underneath... not sure it would be all that practical like that- it can get dangerous under there in a sea if your under there and the dingy is heaving under the boat, you could end up getting squashed under there in bad weather trying to get in or out of the dingy?

    Looking at your cross section, it seems like you have drawn a rather low volume boat for its length. This is great for a performance boat but if you don't have significant living amenities on the bridgedeck then youll likely appreciate a bit more volume in the hulls. You'll likely need a center aisle with cupboard and bench space on both sides. The cupboards and benches can act as hull stiffneners. Try drawing it out with benches and kitchen tops and appliances ie, cross section of the galley- to see how much volume you need... it will likely end up around 4ft width at the waterline...
     
  4. jorgepease
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    jorgepease Senior Member

    I was thinking same thing but water line is 4'. Man is 6' tall by 2' wide and width of hull at eye level is 7'

    Galley cabinets have be to the flared side of the hull so 2 foot of counter does not interfere with walking area but as for fridge and freezer, they either have to be raised which is going to make things feel tight or they have to be located on wing deck of the owners hull where I have set aside for storage or beds etc ..

    I am going to draw the same section at the galley
     
  5. jorgepease
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    jorgepease Senior Member

    See what I mean, not too shabby and with 4' hulls at 55' length we get a pretty good performance number too. I would keep the outboard side open for lots of light and I think move fridge and freezer to wingdeck, I hate the squished in feeling.

    So why build the extra top?

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  6. jorgepease
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    jorgepease Senior Member

    AS for the dinghy, it's just a hope since I don't know where structural beams would be but ... if they can work as I wish, the raised areas are where all the major beams are. In the foredeck around mast, those beams are 42 inches high and about 24" high on the aft deck ... so the dinghy would be over 1 meter above the water line sandwiched in between the beams.

    Seems pretty protected to me but in and out in nasty weather would be not good. On the other hand, I would lower it in protected anchorages almost all the time. I think I would rather build to most of the time, in case of emergency (capsize a life raft might be better anyway but the dinghy would be on top and light enough to flip ))
     
  7. jorgepease
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    jorgepease Senior Member

    Optionally, if outboard hull was flared just 6" (doesn't have to be at right angle as shown) we get full size cabinets on both sides ... I think that might even allow for a compact fridge freezer.

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  8. groper
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    groper Senior Member

    Yep- this could work for a performance yacht. However you can see how it gets tight when you need to fit in the fridge and freezer etc. You can also see that the cupboard space is almost non existent near the bottom of each one. The inboard cavity will house all you conduits for water pipes and cables etc.

    Adding a knuckle to increase volume is a strategy that's been employed by numerous designers over the years. My fiends polycore cat has this feature but he also said it was an absolute nightmare to get it faired. The surfaces above and below have to be perfectly in the right planes of the knuckle line will look wavy. I would deliberately avoid any features like that anywhere on the boat for that reason as features like this are very labour intensive. I guess that has been my philosophy from the beginning- reduce or preferably eliminate anything that will cost you time...

    If you have a genset or diesel engine the only place you can put them in practice with a layout like this is under the main beds. This is a little far after from optimal- note sig puts them under the raised floor mid ship to keep the mass close to longitudinal center to reduce inertia for pitching motions. Under the bed makes maintenance a headache, and its noisy and hot for anyone sleeping on top of it.

    This volume and headroom is required in the middle of the boat and after only. That's why you could employ the coach house for this area and reduce volume forward or simply use a heavily sloped deck like grainger shows in the FF designs.

    Merry Xmas Jorge- I'll send you a post card from NZ over the festive season :D
     
  9. jorgepease
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    jorgepease Senior Member

    Okay, now I understand! Have a good trip and happy holidays!!!
     
  10. jorgepease
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    jorgepease Senior Member

    I wanted to see how much difference the coach roof makes so here are both versions together.

    Huge difference, now you have full size cabinets on both sides and walkway remains same width.

    Plus you get about 4' underneath for, in my case batteries, but could be a genset or other equipment. And the windage penalty doesn't seem so bad with that tilt.

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  11. groper
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    groper Senior Member

    Exactly!!!
     
  12. jorgepease
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    jorgepease Senior Member

    I decided to study the Flying Fish a little more and redo the layout. This is just me understanding the different levels and how I would like to see it laid out.

    hulls are still 4' at waterline and stretched to 60'

    I was able to keep most of the outside deck on one level. It's pretty massive at around 26' length and my dingy gets stored under but above the bottom of the bridge deck sandwiched between beams. This gives a nice uncluttered feel, I like that.

    I kept the bedrooms pretty small but check it out, bed completely accessible from the side and a really large chest of drawers built in to bulkhead doubles as seating or lounge area up top. Bedrooms will be under AC so wanted them small but look at all that floor space and headroom, it's not claustrophobic!

    In the galley there is a full 42" inches of floor space between cabinets ... That is about as big as what I have at home. I used a full size counter on one side and a smaller counter on the other but the cabinets are full 24" deep to hold fridge and freezer. This doesn't affect deck height on exterior.

    The owner's side has a single bed sized lounge in case of extra guests so 4 beds total if need be. I wouldn't go crazy with furniture, I like the minimalist approach, airy.

    I don't know how thick normal bridge decks are, I made mine able to hold about 16" beams with another inch on top and bottom, can't see that racking too easy and that gives plenty of room for the dinghy and other storage.

    Have to see what Grainger says of course but at least I have a better understanding of what fits and how. Happy 2017, let this be the year of huge change!!

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  13. groper
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    groper Senior Member

    Hi Jorge, hope the new year is going well for ya.

    Having sides like that creates many practical problems. Berthing in a marina or wharf, you can't get close to the edges for line handling, plus the overhang in a marina impedes the walkways on the pontoons etc. You often see smaller flares such as those on the Shuttleworth designs for example, but more than that is not very practical for numerous reasons I can't think of right this minute.

    Also the bridgedeck clearances looks low for a performance bluewater boat. You should have over 1m clearance in a 60ft boat, more like 1.2m.

    Also the bridgedeck floor as you show it continues too far forward. Performance boats don't have the floor much forward of the 50% loa. When you press them hard, the bows press down and the waves can start to slam the floor otherwise. It's the opposite with a power cat as the power makes them squat the rear end as opposed to pressing the front down on a sailboat...

    You really need to decide if you want a cruiser or performance boat because you can't really have both unless you accept considerable compromises both ways...
     
  14. jorgepease
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    jorgepease Senior Member

    I deleted the post after seeing the Shuttleworth designs, too curvy, don't like that look. Was trying to reduce wind area as Shuttleworth says that is where the drag is - http://www.shuttleworthdesign.com/Dogstar50-article.html

    The clearance was 37 inches so at 1.2 meters so it should be 42", ok, thanks for that info.

    Really liking the look of the Gunboat 68 - http://www.gunboat.com/series/gunboat-68/
    Getting too big at that point though.

    These are the architects on SIG and Gunboat - http://www.vplp.fr/realisation/no-limit/58.html
     

  15. jorgepease
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    jorgepease Senior Member

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