Sharpie skiff - Chapelle's rules

Discussion in 'Boat Design' started by YK GEO, Oct 23, 2009.

  1. YK GEO
    Joined: Oct 2009
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    Location: Marsh Lake

    YK GEO Junior Member

    I was asked to post photos of my rowboat that I built to Chapelle's rules for sharpies.

    Chapelle measured many sharpies when researching for his books, and the successful sharpie hulls tended to fall into similar proportions.

    I don't have a copy of the rules at present, but going by memory:

    - length to breadth 4:1 and higher. In general, the greater the length to breadth, the faster the boat.

    - bottom profile is straight as it goes down from the base of the stem to about 45 %, then smoothly arcs into an upward direction and sweeps up in a gently curve to the base of the stern. The straight section helps performance. My little boat surfs nicely down swells, riding on the forward section.

    - Boat trims with base of stem just touching the water, and base of transom well clear of water. Absolutely necessary to keep the transom from dragging.

    - Sides angle out approx 15 degrees of vertical, though this doesn't appear to be crucial. 15 degrees fives a nice sheerline with straight boards.

    - Depth of bottom (from waterline) at lowest point, relative to length, is greater for small boats, and less for large ones, but is around 1:30.

    This boat is about 15 ft long, and a bit over 3 ft wide on the bottom. For something I hammered together one afternoon about 12 years ago as a disposable boat for checking my fishnets, it's done well.

    Easy to build in plywood, lumber, or whatever is flat and smoothly bendable. I used shiplap lumber for the sides, and plywood sheathing for the bottom and transom, with galvanized nails, cause that's what was laying around my yard. I fixed it up this summer, and put glass tape on the chines and bottom butt joint for reinforcement, since the nails holding the bottom on were getting loose.

    The key to preventing rot in a wooden boat like this is to build it so any water will drain out when you flip it upside down. Standing water caught in nooks and crannies will rot it out quickly. Mine has been continually stored outside and is sound, though it's made of spruce lumber and sheathing.

    For rowing, a small skeg is okay. For sailing, a larger skeg is needed to control weather cocking. A small 40 - 50 sq ft sail, loose footed lug or sprit is handy, and you can just pop out the unstayed mast when done.

    Rows and paddles nicely, sails okay, and does about 7 mph with a one horsepower kicker.

    Mine weighs about 80 pounds. It's a bit big for cartopping, and I generally haul it in the back of my pickup.

    A good reference for sharpie hulls and all the variations is "The Sharpie Book".

    Cheers

    Geo
     

    Attached Files:

  2. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Your sharpie/flattie boat is dimensionally similar to my own. The design details are the result of lots of reading, experimenting, tinkering. Chine width 37" Flare 15 degrees mol. LOA 15'-6" Deepest part of underwater section about 45% aft of fwd perpendicular. Rocker 4" fwd, 4.25" aft. Design disp. 360#, Weight of hull, boards, rig; 135# This boat varies from Chapelles recipe in that the forward section of the bottom is gently curved downward and the aft section rises in a nearly straight line. Maximum chine beam is about 53% aft of fwd perp. Very modest SA of 59 ft. sq. in a sprit boomed sail. The boat rows well at at about 4 kn. It sails like a demon in a breeze of 10Kn or more. It can and does plane handily. Windward performance is good but not spectacular. It makes the best speed to windward when sailed at a heel angle of 12 to 14 degrees and at that angle it leaves very little wake. When the wind pipes up, I sit on the floor and never need to hike. This boat is not the best for any particular propulsion method but it does well enough, when sailing, that it is an annoyance to more sophisticated (expensive, complicted) boats of similar size. Sharpie types are a lot of boat for the money and building work that one might invest.

    How did you manage to get your boat so light? I used Okume, spruce, aluminum and anything else that was light, but still have more weight than you do.
     
  3. YK GEO
    Joined: Oct 2009
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    Location: Marsh Lake

    YK GEO Junior Member

    Sound like the boats are almost twins, which is understandable. Starting with well proven concepts and designs, we should end up about the same place.

    For how little money and time I put into mine, I've been rewarded many times over in pleasure and utility.

    I forgot to mention seaworthiness which I'm sure you will agree with. In 2 ft chop, it just bobs along like a duck.

    I built it with a centre thwart and dagger board case, but kept tripping over the thing, so covered the hole in the bottom, and welded up an aluminum frame to hold the sides out. A wooden frame would have worked fine, but I wanted to practice aluminum welding. Same with the little skeg. So I guess it's a hybrid - downright ecofriendly before anyone thought of that idea!

    When I row it, I perch on a little stool and brace my feet on the side frames. Works well, and I can clear the centre area anytime I want.

    Geo
     
  4. kayaker50
    Joined: Aug 2009
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    Location: Raleigh, N.C.

    kayaker50 Junior Member

    Very nice!
    I built a stichnglue dory which I am very happy with except for stability. There's no way I'm going to stand up in my boat.
    How stable is your Sharpie?
    How did you build it- over a mould?
    How heavily do you normally load it- just one person, or lots of nets etc.?
    Thanks, Chip.
     
  5. YK GEO
    Joined: Oct 2009
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    Location: Marsh Lake

    YK GEO Junior Member

    Thanks, Kayaker

    I built it upside down over one middle mould, which was the centre frame extended and braced across the top. Attached the side boards together to the short side frames, filling the shiplaps with whatever goop was in my caulking gun, screwed the sides to the stem piece, screwed the sides to the centre mould/frame, and used ratchet cargo straps to bend the sides in at the stern until they fit the transom. Measured diagonals and fidgeted around til it looked symmetrical, then screwed the transom in place. Laid a level across the sides and used a hand plane to level the bottoms of the sides. Rough cut the plywood to shape and strapped it in place; nailed the plywood to the edge of the garboards, flipped the whole thing over and installed thwarts then sawed off the top of the centre mould. Trimmed off the bottom and slopped on some paint. All seams were filled with said goop before assembling. Took about 6 hours all told.

    Having said all that, I'd recommend using plywood everywhere, chine logs, and about three moulds fastened to a strongback.

    They ain't gonna write up my construction methods in Woodenboat, but I lean toward building fast, not pretty. My next little rowboat will be a gunning dory, plywood over longitudinal stringers, fastened with acrylic goop and 1.5 inch stainless staples from an air stapler, driven at opposing angles to make a wedge effect to resist strain. Probably a few stainless screws in crucial stress spots.

    I built one foam core fibreglass boat a long time ago, and that cured me of that approach. Stitch and glue looks fine - I just can't stand the thought of all that stickiness.

    Messabout - if you subtract your rig, oars, etc your boat is probably pretty close in weight.

    Usual load is one or two people, camping gear, hound dog - maybe 500 lb maximum. Once you load it down so the stem is immersed a bit it wants to bow steer, and if the transom immerses it's too slow.

    No problem with standing up in it, given a bit of common sense. I once built a small Banks dory, which taught me why they never built small Banks dories in the old days.

    These little plywood boats will twist and rack badly without corner reinforcements - small plywood triangles at the top in the bow and stern stiffens everything up nicely.

    Thanks for your interest and have a good day.

    Geo
     
  6. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    The similarity in our boats is remarkable. Both of us can be accused of practicing antiquarian technology. I mean who would build a stodgy old 3 board boat? We must have been ignoring conventional wisdom. Maybe so, buit I like Goldilocks, my little yellow flattie.

    I have built dozens of boats, some of 'em faster, some more comfortable, most of them avante garde types.....like Australis catamaran, non shunting proas, experimetal (disappointing) foil borne thingys, articulated wing masts, International 10 meter canoes and other madcap stuff. A fact of life is that taste in boats is likely to change as we get older. I ain't into trapezing any more but I do remember the thrill. These days I'm content to slide along peacefully and tranquily in an old fashioned boat.

    You are right that the Chappelle type flattie is more able than it would appear. Giant wakes left by Donzis and big power cruisers require some attention but the boat does not seem to mind. Just heel the boat a bit and it does not pound, twitch, or deliver surprises. The first experience with a big wake did make my butt pucker, I confess. I have cofidence in Goldie but to be reasonable, she will never visit the sea bouy at the outside entrance to Tampa Bay.

    I built the boat inverted over five moulds with ribbands at the chines and sheer. Construction was as easy as it gets. I did gild the lilly with some of the details. An elegant three piece, bookend breasthook with bright finish, The small side decks keep her from twisting and they are finished bright too. I hate varnish but the devil sometimes make us use it. The hull is finished with Imron over a light FRP outer skin. I built all the hardware from aluminum and anodized it. All except two Harken turning blocks. One for the sheet and one for the snotter. I reckon all that was unnecessary but the pleasure is in the building and fussing over things that probably do not matter. Three cheers for simple boats!

    Where on earth is Marsh Lake??
     
  7. YK GEO
    Joined: Oct 2009
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    Location: Marsh Lake

    YK GEO Junior Member

    I guess antiques practice antiquarianism??

    I did build one boat in a more highly finished style, but couldn't take the angst when it touched bottom, and was inconsolable when it was stolen. Building a pretty boat leads to acute onset of new car syndrome. It's incurable, so now I stay away from fine finishes - had to attend varnishers' anonymous for a while.

    Marsh Lake is in south central Yukon. Greatest outdoor playground going.

    Snow just started, so my little green boat is settling under its winter blanket.

    Cheers,

    Geo
     
  8. kayaker50
    Joined: Aug 2009
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    Location: Raleigh, N.C.

    kayaker50 Junior Member

    Messabout, any photos? I'd love to see them. You guys have me thinnking of building a 20 ft sharpie next. Chip.
     

  9. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Geo; I admire your sense of humor as well as the wisdom of being practical with the finish of our toys. New car syndrome is apt. In defense of my sense of practicality, I swear that I have used exterior latex paint on the interior of numerous boats. Given sufficient cure time, that stuff is near bulletproof. Not shiny, not ostentatious, but very durable, anti glare, and cheap.

    Whoooeee! Marsh Lake is far away. Looking at the Atlas, I do not see Marsh Lake but I do notice a place with a scary name, called Destruction Bay. Your location, Yukon, reminds me of some of my boyhood poetry. Particularly a parody of Tales Of the Yukon in which Dangerous Dan McGrew was a principal character. Those impolite verses are not printable here.

    Kayaker50; If I ever learn to post photos, attachments, and such I will do so. Sharpie types are very easy to build and performance is gratifying but not spectacular.

    One of my most memorable, educational, and satisfying sailing experiences was in Florida Bay off the west side of the keys. I chartered a Bolger Black Skimmer for a few days of pottering around in the treacherously shallow expanse of water there. The Skimmer was built inside out. That is to say that all the longitudinasl members are on the outside where they can create turbulence but keep the interior of the boat absolutely clean. The stringers also protected the bottom from grounding damage. The Skimmer was yawl rigged with sprit boomed sails. As a confirmed racing sailor accustomed to sophisticated and complex boats, I thought, at first, that this beast was unforgiveable. More counterintuitive features was a forepeak partioned off from the rest of the boat and having hundreds of small holes drilled into the bottom. It was a flooded compartment that did not actually flood very much because the forefoot was slightly above the waterline. There was a similar arrangement aft under the little well where the 6 Hp outboard lived. Unthinkable at first impression, but so practical that I was ashamed of my initial derision. The flooded forepeak housed the anchor and rode. Slightly awash the muddy anchor was cleaned in a matter of a few minutes sailing. The sides of the boat were more than waist high at that location. A perfect place to take a shower from the the black plastic water bag hanging from the mast. The compartment drained itself. Too clever. The boat used lee boards attached only by a short length of rope. The Skimmer did everything I asked it to do, it was much faster than I had imagined, it could sail, not just float, in 12 inches of water. It also endured a vicious line squall under reduced sail and never behaved badly. I was hooked on simple boats thereafter and had profound respect for that outrageously crazy Bolger dude. He designed some odd stuff that worked brilliantly.

    If you want to explore sharpie lore, I recommend The Sharpie Book by Reul Parker. A lot of good stuff in that book. For another odd but marvelous Bolger box, take a look at his Birdwatcher.
     
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