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Diagonals in lofting
Hi All,
I'm considering building my own boat from a set of plans. It's nothing major, just a 28' round-bottomed cutter. I know, build a dingy first to sharpen my skills, then build the big one. Problem is, life's getting on and, with the reaper peeking at me from over the next hill, I'd like to get out and do some sailing before he sits down with me. I would try to buy one, but it would seem the rest of the world has never heard of a beamy 24-30 foot wooden cutter with a transom hung rudder and a full keel using lead as ballast. So here I am. I do understand most of the lines used in lofting with the exception of the diagonal. What exactly is the diagonal supposed to show me? While I'm at it I might as well ask about frames. The plans call for steam bent frames because it is supposedly faster, cheaper and takes up less room than sawn frames. I have a few problems with this. 1) Where is one supposed to get the clear wood for the frames, 2] Bending a frame to an arch isn't much of a problem but how do you bend it to match the curve laid out by the intersection of the water lines and buttocks (i.e. the angle described gets more acute the closer to the bow at the sheer but will be flatter on the same frame close to the keel. This can be done on a sawn frame by changing the angle of the bandsaw table as you cut the frame). Thanks for any help, Frank |
#2
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Diagonals in lofting
"Hollywood" wrote in message
... Hi Hollywood. Indeed an abitious plan wihout any previous experience. Your questions show you need to learn some basics. Do yourself a favour and buy the "Boatbuilding Manual from Robert Steward. It can be found on Amazon: http://www.amazon.com/exec/obidos/tg...76967?v=glance It explains all your questions you just asked and more. It is worth the investment. Good luck, Meindert |
#3
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Diagonals in lofting
On Tue, 29 Jun 2004 08:04:37 +0200, "Meindert Sprang" wrote:
"Hollywood" wrote in message .. . Hi Hollywood. Indeed an abitious plan wihout any previous experience. Your questions show you need to learn some basics. Do yourself a favour and buy the "Boatbuilding Manual from Robert Steward. It can be found on Amazon: http://www.amazon.com/exec/obidos/tg...76967?v=glance It explains all your questions you just asked and more. It is worth the investment. Good luck, Meindert Thanks Meindert. I do have experience in carpentry and furniture making (hence wanting a wooden boat instead of fiberglass) and a fair amount in dingy and small craft sailing (up to 30') but somehow I've never put the two together. Thanks again, Frank |
#4
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Diagonals in lofting
"Hollywood" wrote in message
... Thanks Meindert. I do have experience in carpentry and furniture making (hence wanting a wooden boat instead of fiberglass) and a fair amount in dingy and small craft sailing (up to 30') but somehow I've never put the two together. That's a nice approach. The only thing to get rid of now is being used to fairly straight lines and right-angled corners.. :-) Meindert |
#5
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Diagonals in lofting
Hollywood ) writes:
... 2] Bending a frame to an arch isn't much of a problem but how do you bend it to match the curve laid out by the intersection of the water lines and buttocks (i.e. the angle described gets more acute the closer to the bow at the sheer but will be flatter on the same frame close to the keel. This can be done on a sawn frame by changing the angle of the bandsaw table as you cut the frame). Thanks for any help, Frank you get two burly boatbuilders with a big wooden mallet and bend the frame in the hull. note that in bend frames the grain runs along the frame, end grain exposed only at top and bottom ends. in sawn frames end grain is exposed the length of the frame. be sure to seal end grain well. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
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Diagonals in lofting
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#7
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Diagonals in lofting
Hollywood wrote:
Hi All, I'm considering building my own boat from a set of plans. It's nothing major, just a 28' round-bottomed cutter. Yeah, that's nothing major. sarcasm off Sounds like a great project. What design? I know, build a dingy first to sharpen my skills, then build the big one. Problem is, life's getting on and, with the reaper peeking at me from over the next hill, I'd like to get out and do some sailing before he sits down with me. In that case, you should buy a boat rather than build one... since this is heresy for this newsgroup, how about building something smaller & simpler that will get you on the wate sooner? I would try to buy one, but it would seem the rest of the world has never heard of a beamy 24-30 foot wooden cutter with a transom hung rudder and a full keel using lead as ballast. So here I am. Really? Where have you been looking? There are plenty such boats all around. I do understand most of the lines used in lofting with the exception of the diagonal. What exactly is the diagonal supposed to show me? The diagonal is supposed to show that the body plan is "fair" ie a smooth continuous surface, hopefully capable of having planks laid along it without humps, shoulders, or needing to steam the planks to the rigidity of week old spaghetti. While I'm at it I might as well ask about frames. The plans call for steam bent frames because it is supposedly faster, cheaper and takes up less room than sawn frames. I have a few problems with this. 1) Where is one supposed to get the clear wood for the frames, From a lumber supplier that has boatbuilding wood. 2] Bending a frame to an arch isn't much of a problem but how do you bend it to match the curve laid out by the intersection of the water lines and buttocks Bend the frame tight against the inside of a set of ribbands. You need to sit down by the fireside with a copy of Howard Chappelle's book 'Manual of Wooden Boat Construction.' He covers it all in detail, yet clearly. Be sure to read the part about needing a Moaning Chair Fresh Breezes- Doug King |
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Diagonals in lofting
On Tue, 29 Jun 2004 11:24:47 -0400, DSK wrote:
Hollywood wrote: Hi All, I'm considering building my own boat from a set of plans. It's nothing major, just a 28' round-bottomed cutter. Yeah, that's nothing major. sarcasm off Sounds like a great project. What design? Really? I didn't think a 28 footer was that bad. The one I'm looking at is a Mark Smaalder's design called a Wynfall. I know, build a dingy first to sharpen my skills, then build the big one. Problem is, life's getting on and, with the reaper peeking at me from over the next hill, I'd like to get out and do some sailing before he sits down with me. In that case, you should buy a boat rather than build one... since this is heresy for this newsgroup, how about building something smaller & simpler that will get you on the wate sooner? I've been think about that too but I'm in a kind of dilemma on that. I have a great functioning 8' Walker Bay that's almost indestructible, so I don't need a dingy. I would like something that I could stay on board for a period of time (possibly 3-8 weeks or more at a time) without feeling too overly crowded. That kind of eliminates a day sailer. Glen L Marine has a 22' Amigo but there are only stock plans and after talking with them, they made it quite clear that the plans are printed in stone, no changes, no modifications. I found Mark's page and though he does have a smaller version available, I do like the lines and the construction method of the Wynfall better. I would try to buy one, but it would seem the rest of the world has never heard of a beamy 24-30 foot wooden cutter with a transom hung rudder and a full keel using lead as ballast. So here I am. Really? Where have you been looking? There are plenty such boats all around. I'm in the Great Lakes area of Canada. You can buy tupperware by the ton here but wooden boats seem to be in very short supply. I've tried some boating sites (including Good Old Boat which does have some nice possibilities) and tried to find online newspapers for the Canadian east and west coasts as well as Florida, but finding a boat in the classifieds is just a little daunting. If you have any sites, I would appreciate them. I do understand most of the lines used in lofting with the exception of the diagonal. What exactly is the diagonal supposed to show me? The diagonal is supposed to show that the body plan is "fair" ie a smooth continuous surface, hopefully capable of having planks laid along it without humps, shoulders, or needing to steam the planks to the rigidity of week old spaghetti. Now how does it show that? Is the diagonal at 90 degrees to the frame at that point? I guess that's what is confusing me. The buttocks are parallel to a line along the length of the keel and the water lines are parallel to a plane at the base of the keel and perpendicular to it, but what is the source of the diagonal? At what point does it show me a fair hull? Both the buttocks and water lines show some sort of profile where you could pick up points for the frames to lay down on the lofting floor but the diagonals don't seem to show more than a point at a specific spot. If this sounds confused, it because I am. While I'm at it I might as well ask about frames. The plans call for steam bent frames because it is supposedly faster, cheaper and takes up less room than sawn frames. I have a few problems with this. 1) Where is one supposed to get the clear wood for the frames, From a lumber supplier that has boatbuilding wood. There's Noah's in Toronto but it seems to thin out fast after that. 2] Bending a frame to an arch isn't much of a problem but how do you bend it to match the curve laid out by the intersection of the water lines and buttocks Bend the frame tight against the inside of a set of ribbands. ?!? Shows you where I'm at. I was under the impression that the frames were bent on molds, then placed inside the ribbands. You need to sit down by the fireside with a copy of Howard Chappelle's book 'Manual of Wooden Boat Construction.' He covers it all in detail, yet clearly. Be sure to read the part about needing a Moaning Chair Actually, I must be denser than lead because I have been reading Chappelle as well as Larry Pardey (now that's the kind of boat I'm talking about) and while they both talk a lot about diagonals, they don't really explain where they are getting the information to lay it down or where the staring points are. Fresh Breezes- Doug King Thanks Doug |
#9
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Diagonals in lofting
Hollywood wrote:
Really? I didn't think a 28 footer was that bad. Well, I didn't say it was *bad* it's not a practical approach to getting sailing. If the goal is to build a nice boat, then a 28 footer is likely to be more economical and attainable than a bigger one, sure. Building a 28 footer from scratch is likely to take less time & money than say restoring an old 10-Meter starting with just a battered hull... The one I'm looking at is a Mark Smaalder's design called a Wynfall. Not familiar with it... any links? You can buy tupperware by the ton here but wooden boats seem to be in very short supply. heh heh heh think about the reasons for that. It ain't that wooden boats are beeing carefully hoarded by the Secret Elitist Sailor's Bund. I was going to suggest that if you really wanted an old-fashioned boat, that there are a fair number of early fiberglass models that would suit you and provide an outlet for plenty of labor... and you could go sailing in the meantime. Say a Cape Dory or Allied, or an older (pre-1970) Pearson or Islander. ... finding a boat in the classifieds is just a little daunting. It's no picnic finding one in the real world, either. The internet is a tremendous aid in sorting out the chaff. I happen to like Yachtworld and Boats.com which both have good screening search functions. You can select only boats in a give area, of a given material (aluminum, wood, fiberglass, ferrocement, whatever you fancy) and of a given vintage. If the pickings are too slim you can always widen your search. A problem is that the type of boat you are looking for is the type that is least likely to be listed on the internet (although it is freakin' 2004, almost *everything* in the world for sale is listed on the internet!) so calling around to brokers and boatyards may yield some prospects. I happen to enjoy driving to boatyards and poking around the back lots, my wife indulges me a lot but oddly enough her enthusiasm wanes after a bit. We found our current boat on the internet. The diagonal is supposed to show that the body plan is "fair" ie a smooth continuous surface, hopefully capable of having planks laid along it without humps, shoulders, or needing to steam the planks to the rigidity of week old spaghetti. Now how does it show that? Is the diagonal at 90 degrees to the frame at that point? Not necessarily. Some are. I guess that's what is confusing me. The buttocks are parallel to a line along the length of the keel and the water lines are parallel to a plane at the base of the keel and perpendicular to it, but what is the source of the diagonal? At what point does it show me a fair hull? It's not at a point, it's along a line... or more accurately, it is the plane intersection with the hull along a non-normal axis. ANd this is exactly what you need to know if you're going to try & lay planks along the thing. It may be easiest to consider an already built hull. Let's take a long springy batten and lay it along the hull... we'll hypothesize some extra long arms and extra hands to do this, keeping the batten in contact with the hull at all points... We can lay the batten parallel to the waterline at any place from garboard to keel, and the ends of the batten will poke out past the stem & transom. We can lay it parallel to the centerline, so that the ends poke out above the gun'l, this would be the buttocks. Now let's hold the batten at a skewed angle, somewhere between the axis of buttocks & waterlines. We are using an already existing hull, so of course it lays along smoothly. **BUT** if you are considering a hull that is nothing but lines on paper, you don't know that yet! It is quite possible to draw a set of hull lines, frames & waterlines & buttocks, that look great in these three axis but form ungainly humps or hollows, or even discontinuous, along a skewed axis... and this will make it very difficult to plank. A smart designer will lay out a set of diagonals to avoid this, and the smart boatbuilder lofts these diagonals as a check on his mold stations. I just finished lofting a 9 1/2 footer, and did two diagonals. It was a PITA... but I did tweak the lines a little bit and it'll be better & prettier because of that. Bend the frame tight against the inside of a set of ribbands. ?!? Shows you where I'm at. I was under the impression that the frames were bent on molds, then placed inside the ribbands. You could do it that way, but usually there are more frames than mold stations. Setting up the molds, then laying on ribbands, then bending in the frames, allows more frames than stations. Also putting the frames on the molds would create an offset from the hull plan to the hull skin.... most designers draw what they want the hull to look like, not the shape of the inside of the frames. Designs intended for wood construction often provide for "to the inside of the plank" which of course would be on the outside of the frames. Actually, I must be denser than lead because I have been reading Chappelle as well as Larry Pardey (now that's the kind of boat I'm talking about) and while they both talk a lot about diagonals, they don't really explain where they are getting the information to lay it down or where the staring points are Hmm, I don't have a copy of Chappelle handy right now but IIRC he covers diagonals about as well as anybody ever has. The starting points are given along the base line for the hull lines plan. The diagonals are dimensioned in the table of offsets and laid down with the rest of the lines. FWIW there are a number of Lyle Hess designs similar to Seraffyn and Taleisin that were built as production boats. They are usually pretty expensive unless in very crappy condition. Fresh Breezes- Doug King |
#10
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Diagonals in lofting
In that size range, unless you have very unusual requirements such as very high performance,
icebreaking or heartstopping beauty, you can buy a sound boat for less than it would cost you to build it. For example, this Pearson Triton on Ebay. Such a boat will afford opportunity for cabinetry improvements. Hollywood wrote: Hi All, I'm considering building my own boat from a set of plans. It's nothing major, just a 28' round-bottomed cutter. I know, build a dingy first to sharpen my skills, then build the big one. Problem is, life's getting on and, with the reaper peeking at me from over the next hill, I'd like to get out and do some sailing before he sits down with me. I would try to buy one, but it would seem the rest of the world has never heard of a beamy 24-30 foot wooden cutter with a transom hung rudder and a full keel using lead as ballast. So here I am. I do understand most of the lines used in lofting with the exception of the diagonal. What exactly is the diagonal supposed to show me? While I'm at it I might as well ask about frames. The plans call for steam bent frames because it is supposedly faster, cheaper and takes up less room than sawn frames. I have a few problems with this. 1) Where is one supposed to get the clear wood for the frames, 2] Bending a frame to an arch isn't much of a problem but how do you bend it to match the curve laid out by the intersection of the water lines and buttocks (i.e. the angle described gets more acute the closer to the bow at the sheer but will be flatter on the same frame close to the keel. This can be done on a sawn frame by changing the angle of the bandsaw table as you cut the frame). Thanks for any help, Frank |
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