Affordable seaworthy cruiser

Discussion in 'Boat Design' started by goodwilltoall, Jul 31, 2010.

  1. Sailor Alan
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    Sailor Alan Senior Member

    I noticed the same sag, and though the builder must be used to a better solid foundation.

    As i understand it, his 'walls' or cabin sides were built, house like, on top of a house floor like bridge deck. Possibly little or no deflection noticed untill the hull's were waterborne.

    Altogether a sad and public disservice to the sailing community.
     
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  2. Rurudyne
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    Rurudyne Senior Member

    Or FC keel(s) bolted onto a sailboat.

    Actually, if you could pull it off with FC it would be a real "wahoo!" type thing. Of course the literally underlaying problem is any unfairness in the armature which is going to want to make itself known.

    Still ... maybe thinner rolls of mylar on some roll dispenser like they use for wrapping pallets?
     
  3. Rurudyne
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    Rurudyne Senior Member

    Not sure the artificial reef community is happy either.
     
  4. Pericles
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    Pericles Senior Member

    Rurudyne,

    The Mylar needs to be the thickness it is, so that it forces the epoxy to fair itself. It bends in only one direction, so compound curves can't be accommodated. Trial & error, but not expensive in comparison with sanding discs & time. It's way cheaper than granite.

    For a keel, you make a mould in two halves & line it with Mylar. Make a stiff concrete mix using one of the powder plasticisers, that reduce water & minimise shrinkage.

    https://www.google.co.uk/webhp?sour...est water saving plasticiser powder in mortar

    Load one half of the mould with the mix, insert the reinforcing armature & hull attachments, add more concrete to roughly the volume & shape to place on the second half of the mould.

    Secure the two moulds tightly together with straps & stand upright. Vibrate the mould using an orbital sand w/o sandpaper to eliminate air bubbles & top up mould as necessary. Wait three days (curb your impatience) & open the mould. At this point it's worked, (or it hasn't). This is not a viable process for large vessels, because concrete is ***king heavy.

    I mention a transom, only because it could be a work of art.

    http://static1.squarespace.com/stat...24c45/1410765651382/IMG_0501.JPG?format=1000w
     
  5. Rurudyne
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    Rurudyne Senior Member

    Very nice countertop. Use the right admixtures and it could be as water resistant as Roman concrete.

    Btw, couldn't you make a thin decorative plate to attach to a transom?

    Oh, an while we're talking boat building techniques tell me what you think of this: back in the day, before anti-fouling paint, one of the ways they tried to cope with marine hitchhikers was a sheathing of thin wood that could be replaced periodically. It wasn't as expensive as copper sheet, wasn't as good, but left one laughing all the way to the bank just the same because it really wasn't as expensive as copper.

    These days there is a fairly light material that is extremely impervious to water or chemicals but physically weak: HDPE. This stuff isn't immune to fouling but marine growth seems to have difficulty getting a really good grip so they say you can just scrape stuff off. Moreover, it probably has far better water imperviousness than epoxies. It can be "food safe" (no toxins into the ocean).

    So why not sheath a boat's bottom with the stuff, to a judicious distance above the waterline, just thick enough over the real hull to deal with ordinary abrasion and withstand numerable cleanings? It wouldn't be providing any structural strength ... just a smooth skin.
     
  6. Pericles
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    Pericles Senior Member

    This wood would be easier, as an overlay. Sealed with many layers of epoxy & varnish.

    https://www.google.co.uk/search?q=m...niv&sa=X&ei=SxsNVcO3GJXtaqKfgLgD&ved=0CE8QsAQ

    This is apt. http://www.basicallybespokedoors.co.uk/images/marquetry.jpg

    Epoxies are used to repair osmosis blisters in glass fibre boats. Epoxy composite boats are sufficiently water resistant to outlive most of us. Engineered woods with formulated resins yields a hull that is lighter, stronger and more durable than traditionally built glass fibre boats. To this there are the advantages in noise reduction, and insulation from the elements.

    https://www.youtube.com/watch?v=lHKTDJu9MPw&t=14

    Nothing lasts forever. New epoxy formulations are constantly being developed. Early Gougeon boats are still going strong.

    http://www.seattlepi.com/default/article/Airbus-to-use-composites-1192234.php

    https://entropyresins.com/products/
     
  7. goodwilltoall
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    goodwilltoall Senior Member

    Greetings,

    Just had a long reply erased so will post this first.
     
  8. goodwilltoall
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    goodwilltoall Senior Member

    Re: NZ Boi commenting no ballast.

    Plan to use it for trim as well as stability. Jubilee being a power boat with a low SA and having kept weight aloft low, somewhere in the range of 10-20% ballast ratio should suffice depending on overall weight after build.

    Will use concrete because of its preserving qualities as well as the strength it adds and there is plenty of area in the keel to accommodate. I believe the concrete should not be sealed as it draws any moisture against the bottom and sides towards the top where it then evaporates.

    About 10 years ago at my house I had to add a door at an 8" concrete block wall and needed some type of rough framing to hang the door frame on. After cutting and demo I took 2x8's and screwed about 20 screws on the backsides then plumbed/braced them against the jambs and poured a concrete slush from the top, after it set I removed the braces and to this day it hold very well. So will use this technique inside the keel (with plenty of screws at all sides) making sure to go only so deep so as not to penetrate through the keel.
     
  9. Pericles
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    Pericles Senior Member

    20% is twice as much as 10%, so does that mean you have not calculated the weight of ballast required? Too much & you could deep six the vessel at launch & too little will mean floating at a tilt.

    The Pounds Per Inch Immersion PPI usually increases as the hull sinks into the water as the LWL area also increases due to the shape of the hull above water. Think of a dory with wide flared sides. The more it is loaded the more stable it becomes as the PPI increases. However, with a maximum beam of eleven feet & plumb sides, the PPI on your confabulation remains the same number. Ted Brewer explains it all extremely well. See what he write about comfort ratio.

    http://www.tedbrewer.com/yachtdesign.html
     
  10. goodwilltoall
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    goodwilltoall Senior Member

    Greetings,

    BOA is 8'-4", BWL is 7'-10". There is flare at all sections. LWL is 49'-0" so 1317 PPI means Waterplane Area is .64 and yes it will be higher the deeper it goes.

    Without ballast it will float high so plan on having removable ballast during launch and then adjusting accordingly. The fine transom section was designed because as this being a first build it gives leeway if even perhaps its a little heavier build than expected.

    Not possible to be "deep six" even with 20% ratio. I am shooting for being at lines as drawn with partial loads. I always planned to have ballast added and say 10% would be the minimum to get there.
     
  11. Pericles
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    Pericles Senior Member

    There are 6 inches difference between the beam at the sheer & at the beam at the water line. That's just 3 inches per side & to all intents & purposes, your sides are pretty plumb. The vessel is even narrower than I supposed, so I've been looking at the wrong drawing.

    Something to consider; the 20 footer Lumber Yard Skiff by Walter Baron has a beam on the water line both at the transom & midships of 6 feet & the beam at the sheer is 7 feet 6 inches. Its form makes it a very stable boat. T

    http://www.sailfeed.com/2013/03/modern-sailboat-design-form-stability/
     
  12. Milehog
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    Milehog Clever Quip

    I haven't visited this post in some time therefore I've missed much of it, don't intend to go back in order to catch up and won't make any friends with the following opinion.
    What is the prismatic coefficient of this vessel? It looks like a real puke fest in any kind of a sea. You may want to install the furniture on the hull sides rather than the sole, that would make them more usable under way.
    GWTA, I like slim boats and wish you well but have you really considered the magnitude of ordeal life on this boat will be?
     
  13. goodwilltoall
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    goodwilltoall Senior Member

    Greetings,

    Just saying but something I think most of you miss is the flat bottom and full box keel should tremendously help in regards to anti rolling plus even though the wetted area is very high and will work against the efficiency (correct me if I'm wrong on this) it should help as well to keep boat attached to water.

    Milehog, plan to make the seat n table shown convertible to a long bench seat/berth.

    Real reason for posting today is I just found a design by Dave Gerr called Seapiper 34. It also has a flat bottom, same draft, almost same beam, box keel, similar fuel/water capacities. I'm really glad to see this fine looking design and will study it since he incorporated a lot of things I plan to use.

    http://www.seapiper.com/
     
  14. Pericles
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    Pericles Senior Member

    What flat bottom are you looking at? The Sandpiper 34 has a V shaped bow with a warped bottom that flattens moving aft. It carries its hull volume along its length from a full bow to a ostensibly flat transom. It has a draft of 30 inches. The beam is 8 feet 6 inches & length is 34 feet. You've drawn a double ender with a 9 inches draft, 7 feet 10 inches beam at the water line & 49 feet in length. There is a very apt phrase; "Comparisons are odious".

    Why not send your sketch to Dave Gerr & ask his opinion?
     

  15. goodwilltoall
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    goodwilltoall Senior Member

    Gerr doesn't have time to look at my design.

    To correct a few things. The hull is 9" but the box keel carries a substantial part of the displacement and overall draft will be 34-36", on SeaPiper it is 34". There is flare fwd on both but SeaPiper has more. From pic the aft section seems to flatten and reason I think it has little deadrise overall is because of Gerr using the minimum 4-1 L-B ratio which sharpies require. It actually reminds a of Bolger's engine powered boat "Tahiti".

    I would also guess to say that SeaPiper BWL is very close to 7-10". Airdraft for Jubilee 8.50' vs. 8.25' but less structure overall plus a bit lower hull. Fwd freeboard is 5.25' for SeaPiper vs. 4.75' for Jubilee however, Seapipers deck level is around 4.50'. Ballast is 16% about right in the middle of what was assumed for Jubilee. Prismatic .51 vs .67. but three factors offset this, 1.)I the longer hull can be finer in measurements 2.) hull speeds of VL 1.0 vs. 2.0 for Seapiper requiring the lower ratio 3.) lower CP. because of double ended hull and as a result is more balanced for better seakeeping/handling also allowing better water flow.

    I'll have to see in actual use how these comparisons hold up. Probably the biggest concern I would have is the fine fwd sections stuffing the bow before rising.

    Peace.
     
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