30' plywood sharpie

[troy2000]

Originally Posted by PAR

You have to remember when Chapelle wrote about sharpies, he was talking about working craft, that often would have a ton or three of oysters or fish to bring home. The shapes used in these sharpies can't be taken for the shapes used in modern craft of similar model. The reason the "run" tucks up fairly quickly is to keep the stern clear when loaded, other wise it'll drag it's butt, which kills speed. Try not to read too much into the lines of these antique craft, without veering too far from what their primary purpose was, because they didn't.

One of the appeals of the classic working sharpie to me is that ability to take a load without dragging its butt. The one I build will probably be single-handed or sailed with one other person for crew a lot of the time, but I'm sure the cockpit will occasionally have a crowd in it, with people climbing in and out of the cabin.

Chapelle also talked about racing sharpies, and how they were built a little shallower and a little broader in the beam. It looks to me like those are the directions I'll head when I diverge from the classic working lines, without pushing beyond the normal bounds of the traditional hulls.

[PAR]

You'll be much happier if you design the boat for the primary use and live with some butt dragging when the crowd comes aboard. The "race" versions of the sharpie have fairly different lines, particularly aft. The run is straightened, the sides much less flare, displacement carried aft, etc.

[troy2000]

Originally Posted by PAR

You'll be much happier if you design the boat for the primary use and live with some butt dragging when the crowd comes aboard. The "race" versions of the sharpie have fairly different lines, particularly aft. The run is straightened, the sides much less flare, displacement carried aft, etc.

Since the classic working hull was designed to carry heavy loads and I'll rarely be doing that, is there any advantage in sticking closely to it instead of building something closer to a racing hull?

[PAR]

Nope, build the racer and let it be a dog when you have 5 aboard.

[troy2000]

Originally Posted by gonzo

Hey troy2000 if your enlargement doesn't work I can email you a copy of mine.

Looks like I shouldn't have been lumping the Boatbuilding book in with the American Small Sailing Craft book like I did, gonzo. At the time I was bellyaching, I had spent most of my time with my nose in the second one, and I'll stand by what I said about it being illegible. But the Boatbuilding book is printed on smoother, almost semi-gloss paper, and I can read its drawings in good light. I blew up the plans for the 30' cruising sharpie this evening for study purposes, and they turned out very nicely.

I haven't had a chance to try enlarging any drawings from the Sailing Craft book yet. I doubt they'll turn out nearly as well, but maybe I'll be pleasantly surprised.

[PAR]

When you enlarge plans with a photo copier or an industrial camera (not used much any more except on big stuff in the printing industry), you will run into an interesting issue called lens distortion. In fact, if the image (in the book) is taken from a set of plans, it was reduced in size with an industrial camera (enter the first generation of lens distortion), when you re-enlarge the image, you add more distortion to the lines drawing (or what ever). This is usually noticeable around the edges of the image where lines clearly no long are straight.

It's caused by the image perimeter passing through the edges of the camera lens at such an angle that "parallax" occurs. A quick way to tell is to place a straight edge on the LWL and see if it's straight all the way across or better is to see if the waterlines are all parallel (they will not be if it's an image from a book). This isn't a big issue on small changes in image size, just large ones. For example, lets say the original plans were 36" wide and it was reduced to 8.3% of it's original size (3" so it would fit in a book), the distortion would be substantial and all the curves suspect (a subtle but noticeable "fish eye lens" effect on the whole image). If you decided to reverse the situation and enlarge the book image to 36" again, this would be a 1,200% increase on the size found in the book.

If you attempted to build a class racer from a set of plans derived this way, the measuring committee wouldn't pass you, because of all the deviations in the shapes that will occur. Not to mention the lines drawing that looks so nice and fine in the book will now have lines a 1/4" thick.

[troy2000]

Originally Posted by PAR

When you enlarge plans with a photo copier or an industrial camera (not used much any more except on big stuff in the printing industry), you will run into an interesting issue called lens distortion. In fact, if the image (in the book) is taken from a set of plans, it was reduced in size with an industrial camera (enter the first generation of lens distortion), when you re-enlarge the image, you add more distortion to the lines drawing (or what ever). This is usually noticeable around the edges of the image where lines clearly no long are straight.

It's caused by the image perimeter passing through the edges of the camera lens at such an angle that "parallax" occurs. A quick way to tell is to place a straight edge on the LWL and see if it's straight all the way across or better is to see if the waterlines are all parallel (they will not be if it's an image from a book). This isn't a big issue on small changes in image size, just large ones. For example, lets say the original plans were 36" wide and it was reduced to 8.3% of it's original size (3" so it would fit in a book), the distortion would be substantial and all the curves suspect (a subtle but noticeable "fish eye lens" effect on the whole image). If you decided to reverse the situation and enlarge the book image to 36" again, this would be a 1,200% increase on the size found in the book.

If you attempted to build a class racer from a set of plans derived this way, the measuring committee wouldn't pass you, because of all the deviations in the shapes that will occur. Not to mention the lines drawing that looks so nice and fine in the book will now have lines a 1/4" thick.

That makes sense to me. But surprisingly enough, when I enlarged the plans for sharpies out of these books from five inches to over a foot, the long lines. were so straight I could split them with a metal straight edge, and stay in the lines from end to end.

I wouldn't want to push my luck and keep copying copies, though. We have some forms around here that are copies of copies of copies, back for several years. The lines are thick and mangled, the printing waves across the pages like flags in a breeze, etc.

By the way, I did get around to trying to make larger copies of the drawings in American Small Sailing Craft, and it's as I figured: while the lines and construction details are easier to see, the words and numbers I couldn't read straight from the book are also illegible when blown up. The paper they printed the book on is just too coarse and soft, and the letters and numerals turned into blobs.

Ah well....I'm not trying to build directly from plans in the book anyway. I'm just studying them to get a feel for what the general parameters of the type are.

[frank smith]

I thought I would add this picture of a Akin sharpie. John Atkin knew the type very well, and here he has designed a cruising one . You could debate that it is more of a large skiff , but a sharpie is just that.



http://www.boat-links.com/Atkinco/Sail/Matty.html

[Earl Boebert]

Dealing with distorted plans is a way of life for those of us who seek to preserve and replicate old model yachts. Even when you get an old full-size plan there will be distortion owing to the uneven shrinkage lengthwise vs. vertically; on old blueprints this can be 5% or more.

The old-timer's trick, which works remarkably well, is to lay out the stated intervals for stations, waterlines, and buttocks on a fresh drawing. Then cut the distorted plan apart on these lines and glue the pieces down on the new grids. Fair the lines again, using plenty of diagonals, and you'll get about as close as possible to the designer's original intent; remembering that, especially with models, the "real" hull appears during fairing on the building board.

Cheers,

Earl

[troy2000]

Originally Posted by frank smith

I thought I would add this picture of a Akin sharpie. John Atkin knew the type very well, and here he has designed a cruising one . You could debate that it is more of a large skiff , but a sharpie is just that.



http://www.boat-links.com/Atkinco/Sail/Matty.html

Chapelle has a double-ended 30' cruising sharpie in his Boatbuilding book. Unlike Monroe's Egret or the working sharpies, both ends are roughly on the waterline at the chines.

It has practical, if somewhat spartan, accommodations for a cruiser. I'll be referring to it while I design mine. But I guarantee one thing: the head will not be a bucket at the forward end of the cabin between berths, open to the cabin.....I'll do a portable toilet that can be carried ashore and dumped, and provide a private cubicle to one side of the companionway.

Chapelle's cruiser sharpie also incorporates what he called a "Dutch galley." A kerosene stove and a sink are built into a portable box, with a couple of drawers under the sink. The part with the stove is metal lined and insulated, of course. When the galley is in use the lid folds up, and wings fold out to create counter space. The sink drain has a flexible hose that clips to the side of the box; you drop the end into a bucket and drain the sink after you're done with it. When not in use, the box gets stashed on a shelf.

It is tempting to think I might be able to come up with something similar that sets on a chart table when in use, and stashes out of the way the rest of the time....of course, mine would probably have a stainless-steel bar sink and a small propane stove.

If I have time at work tonight, I'll scan Chapelle's drawings and post them. They're the only detailed representations I've seen of a cruising sharpie from 'back in the day.'

[frank smith]

I have seen plans for for the Chapelles double ended sharpie , Brewers Mystic
is very similar . I like the look of Chapelles better . Not having the flair of egret , it will be faster and handle better, IMO . Very cool boat .
If I were going to do it I think I would add a shallow box keel to hold the ballast and move the center board out to the side a little .

[troy2000]

Originally Posted by frank smith

I have seen plans for for the Chapelles double ended sharpie , Brewers Mystic
is very similar . I like the look of Chapelles better . Not having the flair of egret , it will be faster and handle better, IMO . Very cool boat .
If I were going to do it I think I would add a shallow box keel to hold the ballast and move the center board out to the side a little .

I had temporarily forgotten about the Mystic Sharpie; I'll have to compare Woodenboat's study plan for it to Chapelle's double-ender tonight. But now that you've mentioned it, the one was probably the inspiration for the other.

[gonzo]

I owned a 34' version that Chapelle did. They are very fast off the wind, even planing. Upwind they are fair. I was very pleased with that boat.

[frank smith]

Originally Posted by gonzo

I owned a 34' version that Chapelle did. They are very fast off the wind, even planing. Upwind they are fair. I was very pleased with that boat.

Was that a double ended boat ? How was the rudder ? I have heard that the sharpie rudders were not really good . I understand that for a working sharpie ,getting the rudder out of the way was a good thing , and while working an oyster bed you could use it to swing the stern around over the bed ,perhaps using the center board to anchor the boat . I am sure that they would turn in there own length ,and that would be good working in the narrow inlets of Long Island Sound . But I wonder if a conventional stern hung rudder might be better for a yacht version of the sharpie . It would be nice if there was a way to have a spade rudder that could be raised and lowered . I suppose you could cut a slot for the rudder ,but then you loose that advantages of an under hung rudder.

[gonzo]

They are simple rudders that do the job. Every improvement to make the sharpie more modern has more drawbacks than advantages. The sharpie rudders can be lifted for shallow water and beaching. Also, they are under the hull so won't ventilate. Wide and shallow rudders can turn at higher angles without stalling too.