Bill Perkins
10-27-2002, 06:44 PM
I'm preparing to build Pete Cullers' 24 foot Fast Outboard ( 7 ft. beam ) , a Chesapeake style file bottom . The plans are in the mail from Mystic Seaport ( ? it's been a month ! ) but I know from John Burkes' book Pete Cullers' Boats ( page 103 ) that they're going to be sketchy . I've committed to the lease of a shop space starting Nov. First so hopefully the plans will arrive soon .
I intend to change the scantlings and use double diagonal planking on the bottom . I had thought to consult with Reul Parker , but he's headed South to go sailing , so I'm turning to the Designers and Constructors here for advice .I've read Ross's repost , but thought there might be fresh thoughts on this subject . The keel rabbets are definitely out .
Mr. Culler shows 1 1/2 in caulked cedar planking and I want to change this as my boat will live on a trailer . Some may council that it's best to build traditionally , buy water front property , and simply keep the boat in the water where it belongs , but that's not for me . I still want to plank the first layer traditional file bottom or herringbone tho , fan staving at bow , ect . 1 by 6 T&G clear Western Red Cedar is available at a large local yard and I'd thought to use that , with thicker ( and narrower ) lumber hewn and planed to shape in the bow . The lumber is rough sawn on one side which I'll plane off , leaving about 5/8ths in. In the finished interior there will be the minimum of painted nonskid floor boards that will stop at the side benches and the bottom planking , finished bright , will show on the perimeter .
Can this thickness and width of plank be held stable by 6 oz. glass on the interior and ,say , 5/8th in. marine fir ply on the exterior ? This is thicker than the typical lay up for a boat this size but the bottom bridges from the chine to the substantial 6 by 6 keel with no intermediate stringers ( I think I'll laminate the straight 22 foot keel out of 2 by 6 or 5/4 by 6 finnish fir unless I find the perfect timber). Also the flattish surfaces are inherently less stiff than more tightly curved shells . It seems to me that in this case I'm not trying to produce a uniform structural diaphragm , but rather that the keel , chine, and sides provide fore and aft stiffness and the bottom needs to be stiffer athwartship than fore and aft . Having no intermediate interior longitudinals makes the bilge drain and clean more easily and allows my floorboards to stay low , maximizing the exposure of the bright bottom and keeping wieghts low .
The bow would be worked with 2 layers of 5/16th ply over the shaped cedar I guess , or maybe I'd use resawn cedar plank . I have Parkers' The New Cold Molding to refer to for that detail . He's cold molded numerous boats with an initial layer of edge glued 3/4 in. 1 by 4 T&G pine , then 2 diagonal layers of ply . I know the cedars more stable than pine , and if the edges are glued the width of the stock seems irrelevant . Mr. Parkers' book lists some 2 layer layups , but they're double diagonal plywood .
To maintain athwartship stiffness I thought to lay the plywood strips at the same but opposing angle to the keel as the plank below , about 12 deg ( the face plys parallel with the length of the strips ). So , if the 2 layers crossed at an angle of about 24 to 30 degrees , would that be enough to prevent movement of the sawn cedar plank , or is a right angle crossing a necessity ? 45 deg.? Perhaps I could add a layer of glass before or instead of xynole on the bottom to further resist fore and aft dimension changes and stiffen the layup ? Mr. Culler shows an external longitudinal stringer added after the bottom's compleat but my hope is that the second diagonal layer , perhaps with a glass sheathing , will make this unnecessary. Can marine fir ply under cloth be trusted to stay smooth on the bottom and not check ?
The topsides I intend to build glued lapstrake . The originals were 5/8th sawn cedar lapstrake and I'm thinking of using 12 mm ply . The stations are drawn 3 ft. OC . Will 12 mm plank bend fairly over this distance ? Let's assume Occume . I'm thinking of lofting in a new set of stations about 2 ft. 4 in. OC., but if it's not necessary I won't . I'll be lofting the moulds from scratch anyway so this wouldn't be a huge amount of extra work . Anyone used the WEST " flocoat" technique , in which you pour on three coats at once over the ply sheets before cutting ( no cloth used ) ? Worth it for the outboard face , or just put the money into buying the best plywood ?
http://www.imagestation.com/picture/sraid37/p927f9b84424f553826eaa0e5af5bf458/fd1d98f2.jpg
This boat appeared in Launchings . Built by Hadden&Stevens of Small Point Maine . Anyone know if they're still about ? Several were built at Concordia as well . Perhaps the dimensions on the drawings have been taken off professional full scale lofting and I should just build the station moulds to them and not loft the long lines ( tho in this case these consist of only the sheer , the chine , and the straight keel )? I'd be stuck with the 3 ft. spaceing , but maybe my lofting would be a waste of time and material and possibly introduce an error that does not now exist ? I can take most of the mould bevels at chine and sheer off the scaled drawings .Or , were the published dimensions simply measured off the small scale drawing by Mr. Culler , with the assumption that full scale lofting would be done to fair them out ? I don't think the folks at Mystic would know , but maybe someone at Concordia or the builders above would ?
[ 10-27-2002, 08:08 PM: Message edited by: Bill Perkins ]
I intend to change the scantlings and use double diagonal planking on the bottom . I had thought to consult with Reul Parker , but he's headed South to go sailing , so I'm turning to the Designers and Constructors here for advice .I've read Ross's repost , but thought there might be fresh thoughts on this subject . The keel rabbets are definitely out .
Mr. Culler shows 1 1/2 in caulked cedar planking and I want to change this as my boat will live on a trailer . Some may council that it's best to build traditionally , buy water front property , and simply keep the boat in the water where it belongs , but that's not for me . I still want to plank the first layer traditional file bottom or herringbone tho , fan staving at bow , ect . 1 by 6 T&G clear Western Red Cedar is available at a large local yard and I'd thought to use that , with thicker ( and narrower ) lumber hewn and planed to shape in the bow . The lumber is rough sawn on one side which I'll plane off , leaving about 5/8ths in. In the finished interior there will be the minimum of painted nonskid floor boards that will stop at the side benches and the bottom planking , finished bright , will show on the perimeter .
Can this thickness and width of plank be held stable by 6 oz. glass on the interior and ,say , 5/8th in. marine fir ply on the exterior ? This is thicker than the typical lay up for a boat this size but the bottom bridges from the chine to the substantial 6 by 6 keel with no intermediate stringers ( I think I'll laminate the straight 22 foot keel out of 2 by 6 or 5/4 by 6 finnish fir unless I find the perfect timber). Also the flattish surfaces are inherently less stiff than more tightly curved shells . It seems to me that in this case I'm not trying to produce a uniform structural diaphragm , but rather that the keel , chine, and sides provide fore and aft stiffness and the bottom needs to be stiffer athwartship than fore and aft . Having no intermediate interior longitudinals makes the bilge drain and clean more easily and allows my floorboards to stay low , maximizing the exposure of the bright bottom and keeping wieghts low .
The bow would be worked with 2 layers of 5/16th ply over the shaped cedar I guess , or maybe I'd use resawn cedar plank . I have Parkers' The New Cold Molding to refer to for that detail . He's cold molded numerous boats with an initial layer of edge glued 3/4 in. 1 by 4 T&G pine , then 2 diagonal layers of ply . I know the cedars more stable than pine , and if the edges are glued the width of the stock seems irrelevant . Mr. Parkers' book lists some 2 layer layups , but they're double diagonal plywood .
To maintain athwartship stiffness I thought to lay the plywood strips at the same but opposing angle to the keel as the plank below , about 12 deg ( the face plys parallel with the length of the strips ). So , if the 2 layers crossed at an angle of about 24 to 30 degrees , would that be enough to prevent movement of the sawn cedar plank , or is a right angle crossing a necessity ? 45 deg.? Perhaps I could add a layer of glass before or instead of xynole on the bottom to further resist fore and aft dimension changes and stiffen the layup ? Mr. Culler shows an external longitudinal stringer added after the bottom's compleat but my hope is that the second diagonal layer , perhaps with a glass sheathing , will make this unnecessary. Can marine fir ply under cloth be trusted to stay smooth on the bottom and not check ?
The topsides I intend to build glued lapstrake . The originals were 5/8th sawn cedar lapstrake and I'm thinking of using 12 mm ply . The stations are drawn 3 ft. OC . Will 12 mm plank bend fairly over this distance ? Let's assume Occume . I'm thinking of lofting in a new set of stations about 2 ft. 4 in. OC., but if it's not necessary I won't . I'll be lofting the moulds from scratch anyway so this wouldn't be a huge amount of extra work . Anyone used the WEST " flocoat" technique , in which you pour on three coats at once over the ply sheets before cutting ( no cloth used ) ? Worth it for the outboard face , or just put the money into buying the best plywood ?
http://www.imagestation.com/picture/sraid37/p927f9b84424f553826eaa0e5af5bf458/fd1d98f2.jpg
This boat appeared in Launchings . Built by Hadden&Stevens of Small Point Maine . Anyone know if they're still about ? Several were built at Concordia as well . Perhaps the dimensions on the drawings have been taken off professional full scale lofting and I should just build the station moulds to them and not loft the long lines ( tho in this case these consist of only the sheer , the chine , and the straight keel )? I'd be stuck with the 3 ft. spaceing , but maybe my lofting would be a waste of time and material and possibly introduce an error that does not now exist ? I can take most of the mould bevels at chine and sheer off the scaled drawings .Or , were the published dimensions simply measured off the small scale drawing by Mr. Culler , with the assumption that full scale lofting would be done to fair them out ? I don't think the folks at Mystic would know , but maybe someone at Concordia or the builders above would ?
[ 10-27-2002, 08:08 PM: Message edited by: Bill Perkins ]