Another sharpie...

Discussion in 'Boat Design' started by micah719, May 4, 2013.

  1. micah719
    Joined: Jul 2012
    Posts: 30
    Likes: 7, Points: 0, Legacy Rep: 92
    Location: Somewhere in Germany

    micah719 Plotting Dreamer

    Another sharpie...

    LOA 28'6"
    LWL 28' (plumb bow)
    Beam WL 6'
    Beam Deck 6'6"
    Disp 5000lb
    Ballast 600lb internal
    Draft 1'10"
    Junk Schooner Rig, approx 570 sq ft

    2kW diesel genset, 4 x 8D AGM, 5kW E-motor, prop in tunnel

    Forepeak 3'
    Foremast stepped in double crash bulkead
    Fore V-berth 6'6"
    Galley 2'6" (standing headroom with hatch open)
    Pilothouse over engine bay 6'6"
    Head compartment 2'6" (standing headroom with hatch open for shower)
    Mainmast stepped in double bulkhead
    Aft V-berth 6'6" (standing headroom for yuloh)

    Deckhouse begins midway over fore v-berth, ends 4' fwd of transom
    Pilothouse midships (no cockpit, all sail line handling internal, same concept as Layden's Paradox)


    Any input?
     
  2. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 121, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    That is a lot of sail for such a narrow beam.
     
  3. Waterwitch
    Joined: Oct 2012
    Posts: 108
    Likes: 19, Points: 18, Legacy Rep: 20
    Location: North East USA

    Waterwitch Senior Member

    A drawing would help visualizing your design. Paradox is 14 ft long so I can see the compromise for not having a cockpit in that boat, although I feel sorry for the passenger
    crammed in the cabin while the helmsman steers with his head stuck out the hatch.
    With a 28 ft boat why are you still trying to sail the boat from such a cramped layout?
    I like being out in the cockpit myself as opposed to stuck down below or peering out a hatchway.
     
  4. philSweet
    Joined: May 2008
    Posts: 2,410
    Likes: 237, Points: 63, Legacy Rep: 1082
    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    Sounds pretty good, but you need to look carefully at the tunnel hull idea. The sharpie, particularly the file bottom variety, are remarkable low power craft, but you can loose that in a hurry if the tunnel isn't right. In all likelihood, you could find a way to swing a 12" prop, which is plenty. I wouldn't add a single square inch of surface area to try to swing a bigger one. You want to keep the cruise power around 1 to 1.25 hp/ton. A quick run with Godzilla yielded .75kW for 2.25MT at 2.65 m/s with 1.9m beam and a GMT of 1.1 m. Figure double that for an well faired build with windage and appendages.

    Can you post pictures or a sketch, particularly a midsection? I'd advise against the junk rig on a small sharpie. Just stick with the lug rig. The need is for automatic gust response (wind spilling) so you can maintain a high average power and keep the burdensome beast moving. A lug on a bendy round wooden mast does this in spades. The junk rig is a lot fussier in this respect and seems to work best where there is ample form stability, ie larger boats. A gaff rig like on Monroe's Egret would be my second choice.

    I think you could go longer than 28' if you wanted to. 33' LOD and everything else the same would probably work out a tad more efficient for your power and might look better as well. The boat would be slightly easier to drive at 5-6 knots and the same sail carrying ability, as best I can figure. I spent all of ten minutes looking at this, so it needs verifying. Nothing at all wrong with 28' if thats what you want.
     
  5. micah719
    Joined: Jul 2012
    Posts: 30
    Likes: 7, Points: 0, Legacy Rep: 92
    Location: Somewhere in Germany

    micah719 Plotting Dreamer

    Thanks for the responses!

    I've been thinking about it, and made a couple of changes.

    The deckhouse can go, since with a 5'6" freeboard at the bow and 5' midships gives plenty of room and righting moment, and declutters the deck. That gets me to 6' airdraft, and means I can fit in any of the UK midland canals, especially under bridges and into locks.

    The Chinese Lug on a sharpie....I've heard others say it would be a good match, but will look further into it. The beauty of it is that it is a rig that can be completely controlled from one location.

    The "Paradox" cockpit is ideal for European waters...if there's any way I can avoid prolonged sitting out in the crappy Euro weather, I'll take it. If the weather is fine enough for festering on deck, I can still do that with the P-cockpit, but those times will be rare. And with a cockpit length of 6'6", width about 5'8" and height of 4'6 (probably nearer 5'6" depending on the height of the genset under it), it won't be a cramped cockpit when buttoned up.

    The engine is unfortunately an essential for canal work. I'd be happy with a yuloh and sails, but in the interests of not getting in everyone's way the iron topsail is a must. I'd considered an outboard in a well, but gasoline and a big hole in the hull lost out to diesel inboard with fixed shaft. The tunnel is to maintain the shoal draft and hopefully gain a bit of efficiency. I decided to explore the hybrid because in this size it won't get astronomical in cost. Since this sharpie needs a fair bit of ballast, I thought battery lead a more useful thing than mere dead lead. Also, the e-motor is on tap immediately and with 4 x 8D batteries (or 8 x 4D) has enough grunt and endurance, and is silent...nice to not wake up the harbour or annoy the neighbours on the canals.

    Finally, the length...I've already had a couple of bouts of 2-foot-itis, and could go maybe one or two more, but want to keep it compact. I wish the UK had built the canals to be compatible with Bolger's AS29, but they weren't so considerate. Mooring fees go by length, but on a sharpie one gains room only by stretching. 28" is about the right compromise, give or take a couple of feet...

    There's a spot above the cockpit that is clear of sail and lines....I was thinking of a hinged arch there to hold the genset exhaust and the stove chimney, and swivel a couple of solar panels off it when the yellow thing in the sky is visible (as an Aussie in the Eu, the infrequency of this makes me cry). Masts and sail bundles can stow either side of the deckhouse when I'm passing under bridges. A bit of fiddling to get a decent collapsible setup with the hot pipes and wires etc....we'll see.

    Again, thanks for the input! Now to attack the junk rig vs sharpie conundrum....Occam, bring me the razor!
     
  6. micah719
    Joined: Jul 2012
    Posts: 30
    Likes: 7, Points: 0, Legacy Rep: 92
    Location: Somewhere in Germany

    micah719 Plotting Dreamer

    From http://www.oceannavigator.com/January-February-2003/Voyager-explains-junk-rig-choice/
    I think I'll stick with the junk-rig....if it turns out to be a stupid decision of mine I can always change it. Yes, it's a lot of area, but with the easy reefing of a junk sail I can carry more sail longer, and drop it fast when I want to. And all from the comfort of my warm, dry cockpit. I suppose I could do it tough like a salty old sea dog, shivering out in the weather. Maybe on those days where the masochism sub-routine is running....

    Where to run the lines? Probably through drained shafts as per Paradox, then around turning blocks in channels under the side decks. A stopper knot on the end so I don't lose the line...that could lead to an embarassment. I'll add some cleats so as to be able to sail from on deck when it's very nice weather. Every ten years or so...

    Single sheets or double? I like the idea of a double sheet at least on the main, for maneuvering in tight spots...sail the boat backwards by sheeting the sail out amidships.

    Wheel or tiller lines? Both, but the wheel would have to mount fore & aft. A bungy cord with a peg in the middle to slot into a hole on the wheel...lashed tiller.

    One major problem still to conquer....how to set up a proper bilge? Sometime a bit of water is going to come aboard, where is it going to go? I thought a small well in front of the hatch, fore & aft, covered with a grating and with a pump in the sump. The 50 miles of halyards can dangle down in there as well.
     
  7. philSweet
    Joined: May 2008
    Posts: 2,410
    Likes: 237, Points: 63, Legacy Rep: 1082
    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    I was thinking of a boat with about 10" of freeboard, so please ignore my rig comments. I was also thinking of a junk rig that set up like a lugsail. The flexible mast statement you quoted makes no sense to me. If the mast flexes a bit and the sheetlets are fixed, the upper part of the sail will flatten out. That is the opposite of what you want. And the battens will bend more, this also tends to power up the boat.

    You want the upper mast of a leg-o-mutton sail to bend more aft than the direction of the sail cloth it is tied to. This loosens the leach and allows twist. If the mast bends off in line with the sail, which is what you might expect to happen, the sail's twist is not increased by nearly as much in gust response.

    However, if this is a canal or river boat, the various troubles the junk rig has might be of little concern. On a river, the wind either is blowing right up stream or right down stream and almost never across the stream. So you have a very different set of conditions than on open water. You could probably use about 150 square feet of sail. You only need about 1.5 horsepower, and you're only sailing down wind on a river. The junk rig is decent downwind.

    You need to calculate all the weights and stability of this craft. A 28' sharpie should have an air draft not much over 2', and freeboard of less than a foot. They are small boats accomodation-wise. Not every boat with a flat bottom is a sharpie. Have you looked at the conventional rivercraft from your area from two centuries ago? They pretty much invented the high-sprit loose-foot four-sided sail for auxiliary power on rivers and light coasting work. They power/depower using braile lines. These might resonably be described as the exact oposite of a junk rig's sheetlets, which may be food for thought. The high sprit is adapted to estuaries by doing pretty much everything exactly opposite to the junk rig's approach.

    With 5' of freeboard, you may want to consider adding about four more tons of displacement in the form of ballast. That would put you up in the 5+ hp range for power though. An DLR of 300 would probably keep her stood up. But more beam would do it cheaper and better.
     

  8. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    I like the idea, but I wonder if it will have the stability at that width. Bolger's Jessie Cooper is 7.5" beam at 6000lb disp., and has quite a bit greater stability. The Junk rig is also heaver the other rigs might be.

    Where is the max draft figured from?

    F
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.