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Thread: Sailing/rowing/motor sailing dinghy decisions.

  1. #1
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    Default Sailing/rowing/motor sailing dinghy decisions.

    Hi all,

    I am in the process of designing a 12 ft dinghy for sailing, rowing, or for use with a small outboard motor. As for how it will get used mostly, I would say 50% sail and 50% motor (fishing), with occasional rowing thrown in.

    OK. So as I said, I have started the design, and here is a list of some of the criteria and why I've chosen that route. The design isn't set in stone, so please make suggestions if you see areas that could be improved in some way.

    12' length chosen for storage reasons
    5' beam chosen for stability
    Stitch and Tape construction. with 4 panels forming a simple V-hull.

    Here is my current 3d view and lines drawing of the hull from the FreeShip program.

    3D hull view.png
    12 ft dinghy linesplan.jpg

    So I realize this isn't going to be a super efficient hull, but I'm ok with that. I want something stable in all modes, easy to build, and with as much room as practical. That said, any suggestions on how to change/improve, either from a ergonomic, efficiency, or other point of view?

    So once the hull shape is finalized, I'll solid model the whole boat in CAD, but I need to decide what kind of sail plan to go with. I have basically considered most sail type as possibilities as shown in the picture below. I personally only have sailing experience with the Cat rigs, Bermuda sloops, and lanteen rigs. I'm not considering a lanteen rig, primarily because I don't like the looks of them even though they have some good benefits. That said, I need to weigh this for myself, but I would like to hear opinions regarding the different rig types concerning ease of setup, ease of use, efficiency, etc. I'm kind of stuck between familiarity (cat and bermuda sloop), simplicity (lugs, sprit, cat rigs), and what I consider the best looking (Gaff rig sloop). The finished product will be a trailer sailer for sure, so ease of setup is important. Some of the other considerations is that several of my concepts could likely use unstayed mast. I would likely use either a used aluminum mast or just use a round aluminum tube section. The later appeals because it would be easy to do a 2-piece mast with s splice. Anyway, any comments/suggestions are welcome.

    Thanks,

    John Brannen

    12 ft dinghy Sail concepts.jpg

  2. #2
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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    That hollow section in the bow just above the waterline is unlikely to plank in sheet material, i would fair that little section in with the aft part, so it could all be done with one length of ply.
    Simplicity and ease of a balanced lug is hard to get away from, having used it these past few years, i would not go back to sprit. I like gunter rig for keeping spars short, but adds the "complication" of setting up 3 stays! Always nice if you have crew to give them a jib sheet to play with.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    I agree with skaraborgcraft.

    if you want to make it from stitch and glue ply, you need to seriously consider conical or cylindrical projection for the bottom panels otherwise it may be impossible to get the sheet material to conform to the shape. If you have calculated the usual figures (waterplane area, displacement, LCB etc.) then relying on the designed shape to predict the eventual craft may cause problems.

    At the very least, model it from stiff cardboard or thin ply to see what is feasible with sheet material and if the shape comes out to something that you want.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Another vote for a lug rig for quick set-up and simple handling, also easy reefing (which the spritsail doesn't do). If you think a boomless sail might be an advantage, you might consider a standing lug (no boom to hit unwary passengers).

    I haven't found any rig to come anywhere close to a lugsail for simplicity and easy set-up.

    Tom
    You don't have to be prepared as long as you're willing to suffer the consequences.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by skaraborgcraft View Post
    That hollow section in the bow just above the waterline is unlikely to plank in sheet material, i would fair that little section in with the aft part, so it could all be done with one length of ply.
    Simplicity and ease of a balanced lug is hard to get away from, having used it these past few years, i would not go back to sprit. I like gunter rig for keeping spars short, but adds the "complication" of setting up 3 stays! Always nice if you have crew to give them a jib sheet to play with.
    Quote Originally Posted by Phil_B View Post
    I agree with skaraborgcraft.

    if you want to make it from stitch and glue ply, you need to seriously consider conical or cylindrical projection for the bottom panels otherwise it may be impossible to get the sheet material to conform to the shape. If you have calculated the usual figures (waterplane area, displacement, LCB etc.) then relying on the designed shape to predict the eventual craft may cause problems.

    At the very least, model it from stiff cardboard or thin ply to see what is feasible with sheet material and if the shape comes out to something that you want.
    Thanks. I just went in and flattened that area out. Before I build the real deal I plan to do several mock ups. I'll start with posterboard doing a scale model of the boat, and work up to something like a sheet of cheap underlayment to mock up the first 3-4 feet of the bow before the real build.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    The lug sails are looking good. Since I have no first hand experience with most of these types of sails, I have been scouring the internet to try to learn. Since my first post yesterday I think the sprit is definitely out of the running. Looking at the others, I really like the simplicity of the lug, and the booless standing lug is appealing. As I sit here looking at the different sail types I drew out for the boat it occurred to me that mast position for the Cat rig and the standing lug are almost identical, and there isn't much difference between the mast position for the Bermuda sloop and the standing lug. I'm thinking if I'm smart in my design of the forward part of the boat, I could make an adjustable mast partner and step. Doing this I could start off with one sail type and later on try another if I want.

    I really am in love with the nostalgic look of the gaff rigged sloop with its bowsprit and all. I'd like to give that a try, but for a first sail type I think either a balanced or a standing lug or possibly a cat rig are going to be the order for the day.

    Still thinking though, so keep the comments coming.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by Anders Bjorklund View Post
    John, I'd suggest you look at a couple of plan sets offered by Graham Byrnes. He's an immensely respected established designer, yet his plans are dirt cheap - like $68. Amanda features a standing lug rig. Spindrift shows a conventional cat rig. I have sailed a 12' Spindrift and it handled beautifully.

    http://bandbyachtdesigns.com/sail/amanda/
    http://bandbyachtdesigns.com/spindrift/
    Thanks. Both of those look like great designs. I especially like how the spindrift can be made into a nesting 2-piece boat. Really neat.

    I realize there are many existing designs that are proven, fit my criteria, and have plans that are either low cost or even some that are free. Having said that I am committed to doing this boat all on my own from design to build to use. I won't go into all of the reasons except to say that it is the kind of thing I enjoy. All my life i have just dove into projects head first. Sometimes they come out great, sometimes not so much, but I have never regretted the adventure and that is how I am approaching this boat.

    Thanks for the suggestion though.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    So I have been doing some more work on my design. I've done a lot of reading and looking at other designs out there. I think the way I'm heading is as shown in the attached pictures. On advice from you guys I modified the lower part of the bow to make it more stitch and glue friendly. As for the sail plan, through many iterations, I came up with a 69 sq. ft. lug main with a 15 sq. ft. jib on a short bowsprit.

    I have come up with 2 arrangements that keeps the calculated sail CE within 2 inches of each other when running without a jib. It entails having one mast partner, but 2 mast steps. My idea is that if I want to run main only I can use a vertical un-stayed mast, and rig the sail as a balance lug sail. If I want to sail with the jib I use the other mast step which rakes the mast aft, add shrouds, and use the jib halyard as a forestay. Then I can rig the sail as a standing lug and the CE of these two setups is pretty much in the same spot.

    Some people may ask why the 2 rigs? Basically I just really like the looks of the gaff rigged sloops, but I don't think I want to go to all the trouble of that setup. Also, all the gaff-sloop rigs I drew up required a mast that wouldn't fit in the boat, which has become an additional criteria. The lug sail with the jib and bowsprit is a close enough to gaff-sloop look to satisfy me.

    I do have a couple questions.

    1. For a 12' S&G boat, is 1/4" plywood sufficient for the bottom of the hull? I'll be beaching this boat and some of the lakes I go to have somewhat rocky bottoms. I am contemplating 3/8" ply for the 2 bottom panels with 1/4" ply for the sides of the hull. I will be fiberglassing the outside of the hull and possibly the inside too.

    2. Does anyone see any glaring problems with either of the sail plans I have here?

    3. An additional idea I have for adjusting centerboard position since this is an unproven design is to make the CB slot longer both fore and aft of the "guessed at" CB position. The centerboard position could then be adjusted anywhere within the slot by installing blocking ahead and behind the CB in the slot. Any opinion on this idea?

    4. Anything else that I'm missing or overlooking

    I'm getting closer, but since it will probably be next spring before I can even start on this boat, because of other projects, I still have plenty of time to alter my plans if necessary. So, if you guys see any flaw in my plans please let me know.

    Thanks.

    12 ft dinghy Linesplan 2.jpg12 ft dinghy Lug with Jib Model (1).jpg

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    6mm ply for the bottom is ok as long as you do not hit anything,tread lightly, and be carefull when launching and retrieving; I personally would use 9mm with a light cloth for abrasion resistance. Hard to quantify panel thickness without knowing how far your frames will be apart.

    Rig looks fine. Mirror dinghy had a 2 step set up so could be used with the single gunter or with a jib, nice to have the choice.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Wouldn't the jib get hung up on the yard with each tack on the standing lug/ jib dual sail set up?

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by skaraborgcraft View Post
    6mm ply for the bottom is ok as long as you do not hit anything,tread lightly, and be carefull when launching and retrieving; I personally would use 9mm with a light cloth for abrasion resistance. Hard to quantify panel thickness without knowing how far your frames will be apart.

    Rig looks fine. Mirror dinghy had a 2 step set up so could be used with the single gunter or with a jib, nice to have the choice.
    Thanks. I haven't totally figured out the internal structure of the boat yet except that it will for sure have a frame at 1 ft forward of the transom, and at the centerboard trunk. From there I haven't decided if I will put in more frames, or maybe do fore-aft frames at the edge of the side seats to create flotation chambers. I'm leaning toward the latter. The fore aft distance between the frames I will have is about 5-1/2 ft. I think I'll just go ahead and figure on having 3/8" ply for the bottom of the boat. Thanks again.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by jtdums View Post
    Wouldn't the jib get hung up on the yard with each tack on the standing lug/ jib dual sail set up?
    I had thought about that too which is why I initially hadn't considered a lug with a jib, but in my hunting around the internet for ideas it appears that a lug-jib combo isn't that uncommon. From the pictures of similar setups it appears the overlap I have drawn is about what others are running successfully, but who knows. I figure I'll make everything on the yard as smooth and snag free as possible and hope the jib blows past it without problem. If it doesn't, I can just cut jib moving the leech so that it can't snag. I'd lose a little sail area, but I could make up for it by pushing the tack out with a slightly longer bowsprit. Below is what that might look like. Maybe I'll just go ahead and plan on this to avoid problems.

    12 ft dinghy Lug with Jib Model 2.jpg

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    With regards to your 9mm ply bottom, frame or stringer spacings should not be more than around 28in apart if using sawn frames (bent frames are around 6in spacings). According to data in Gerrs book. I had a very wobbly 9mm bottom on a power boat that i added stringers to, it may have been ok had i left the rocker in the bottom, but as a flat panel, it lost a bit of stiffness.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by skaraborgcraft View Post
    With regards to your 9mm ply bottom, frame or stringer spacings should not be more than around 28in apart if using sawn frames (bent frames are around 6in spacings). According to data in Gerrs book. I had a very wobbly 9mm bottom on a power boat that i added stringers to, it may have been ok had i left the rocker in the bottom, but as a flat panel, it lost a bit of stiffness.
    Well isn't that convenient. If I measure the widest distance between the side seats it is 29 inches, but that is only at the widest spot. I think that should be fine, but I can also just make the seats on either side 1/2" wider and that would bring it to 28". Thanks.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    3. An additional idea I have for adjusting centerboard position since this is an unproven design is to make the CB slot longer both fore and aft of the "guessed at" CB position. The centerboard position could then be adjusted anywhere within the slot by installing blocking ahead and behind the CB in the slot. Any opinion on this idea?
    I did this as part of a somewhat experimental change to my Whisp, switching it to a lug yawl. The board case is longer than the board is wide. I cut a piece of minicell foam to make up the difference, so I can fit the board aft when using the mizzen, and forward when sailing with the main alone. The minicell works well, has the right density and provides just enough friction to stay put itself and keep the board down.

    Like others, I am inclined to advise building a proven design. But you seem to be doing all your homework, and if a 12 foot boat doesn't work, there's not much lost in time or money. So I encourage you to push onward.

    I wouldn't bother with a jib on such a small and simple boat. It's just not worth the trouble. If you want a quick and simple sail, check out the stock Optimist pram setup. If you want something traditional, then a balanced or standing lug will probably be most satisfying. Going loose footed is good for saving the occasional knock on the noggin, but you will pay for it downwind.
    -Dave

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by Woxbox View Post
    I did this as part of a somewhat experimental change to my Whisp, switching it to a lug yawl. The board case is longer than the board is wide. I cut a piece of minicell foam to make up the difference, so I can fit the board aft when using the mizzen, and forward when sailing with the main alone. The minicell works well, has the right density and provides just enough friction to stay put itself and keep the board down.

    Like others, I am inclined to advise building a proven design. But you seem to be doing all your homework, and if a 12 foot boat doesn't work, there's not much lost in time or money. So I encourage you to push onward.

    I wouldn't bother with a jib on such a small and simple boat. It's just not worth the trouble. If you want a quick and simple sail, check out the stock Optimist pram setup. If you want something traditional, then a balanced or standing lug will probably be most satisfying. Going loose footed is good for saving the occasional knock on the noggin, but you will pay for it downwind.
    Thanks. I'm glad to hear someone else has done the centerboard idea and it works. I'm going to incorporate it into my design. I may use it so as to not have to use different mast steps.

    As for existing designs, I just really enjoy doing this kind of stuff. I was initially going to build an Argie 15, but then decided that 12' was about the limit storage wise. At 12' my thought was along the same lines as you mention, that it won't be a ton of money that is invested.

    Since this is my first boat design, I am considering building a prototype out of lumber store plywood rather than the more expensive marine plywood and only fiber-glassing the seams and sealing with paint to prove the design. I'm also initially going to be making the sails out of tarp material. If I go this route, the initial costs should be real low. If everything works ok I would make design changes as necessary and build a better one out of better materials. Build 2 boats to get one?? Well as Forrest Gump would say, "stupid is as stupid does."

    Regarding the jib, the ONLY reason I'm including it on the boat is because I like the look.

    Thanks again.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by Woxbox View Post
    Going loose footed is good for saving the occasional knock on the noggin, but you will pay for it downwind.
    In a 12' boat that's not a racer, you won't pay much at all for going boomless. A fraction of a knot in real speed, probably. And much more convenient. The smaller the boat, the peskier a boom is.

    Tom
    You don't have to be prepared as long as you're willing to suffer the consequences.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    If you try a boomless sail, you have to look at the sheet lead position to get the proportion of leach to foot tension correct for your average conditions. That might lead to a shorter mainsail foot, or moving the mainsail forward, or lengthening the boat etc. It's done geometrically. The books say what the rough line should be. Look over Vivier's flat bottom, single chine Sorine.



    https://www.vivierboats.com/en/produ...sailing-skiff/
    Last edited by Edward Pearson; 10-31-2018 at 05:00 AM.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by Edward Pearson View Post
    If you try a boomless sail, you have to look at the sheet lead position to get the proportion of leach to foot tension correct for your average conditions. That might lead to a shorter mainsail foot, or moving the mainsail forward, or lengthening the boat etc. It's done geometrically. The books say what the rough line should be. Look over Vivier's flat bottom, single chine Sorine.
    I've been pondering the boomless option. As you pointed out, to use the boomless option I'd have to have a shorter foot which means either a smaller sail, or a taller sail. In order to get the sail area I would like (60-70 sq ft), reguires a taller sail and hence a taller mast. I would like to have the mast and spars fit inside the boat. With the shorter wider sail plans I've drawn, I can achieve that and still get the sail area I want but it negates the boomless option. From the looking I have done, it looks like the sheet angle for a boomless option is pretty close to a line drawn from the hoist point of the yard through the clew and to the deck. For my boat, would mean a mast about 2 ft longer and then it wouldn't fit in the boat. Still haven't totally discounted it though.

    As for the boomless standing lug in general, I have a couple questions. I see the picture you posted shows reef points on the sail, but doesn't that require a boom to reef? Also, what are the pros/cons to the boomless lug? I have read that downwind they suffer because there isn't anything to hold the clew out, but they have 2 obvious benefits in that they have no boom to clock occupants in the head, and they have less hardware, but is there more?

    Thanks again. The comments really spark my brain and are getting me narrowed in on things.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    I'm using a boomless standing lug on my Alaska. Reefing is dead simple--just roll the foot of the sail up and tie the reefing lines. You do want the sail to have a continuous reefing band rather than separate reef points so it can take the strain when reefed. Very simple reefing, actually simpler than with a boom.

    Advantages: No head knocking. One less spar to build, one less spar to stow when the rig is down. No boom to drag in the waves when heeled. Sail twist automatically de-powers the sail when it's windy, kind of an automatic safety feature. No real way to adjust that (no outhaul with no boom).

    Disadvantages: You must get the geometry correct for sheeting, as Edward Pearson points out above. No doubt about it, that is crucial. My understanding for a boomless standing lug is, draw a line that runs through the throat (intersection of head and luff) to the clew, and continue that line. That's where you want to sheet to. Ideally that sheeting point will move a little forward for windward work to get the draft of the sail farther forward. In practice, I don't bother--that position works well enough for me to be happy.

    You can't really control the sail twist (which, as noted above, is also a good thing). Other than that, there are no other disadvantages for windward sailing. Once you get to a broad reach/run, you can't hold the sail out as far as you can with a boom. I have found that this doesn't matter nearly as much as I thought it would. It does encourage "tacking" downwind rather than running, which is a GOOD thing in my opinion.

    The reality is, except in light winds while sailing downwind, a boomless sail doesn't really have any disadvantages for a cruising sailor. The advantages of a boom are often overstated, unless you really want maximal control over sail shape, as racing sailors do.

    Others will present very intelligent arguments about why a boomed sail is better. Many ways to skin many cats.

    Tom
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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Well that makes sense on the reefing.

    I have been exploring the boomless option more and it is attractive. I'll draw up some sail options tonight I think to explore the possibility.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    I tried several different combinations to achieve my desires and be able to use a boomless standing lug main. Here is one attempt I had. To give credit, the main shape is scaled from a sail Todd Bradshaw designed for an Argie 15 builder. The main is about 64 sq ft and the jib adds about 15.5 sq ft. So this would get me the sail area I'm looking for and looks pretty good too.

    12 ft dinghy Lug with Jib boomless.jpg

    One problem with this arrangement is that in order to get the sheet point ahead of the transom, I had to lower the sail quite a bit. As drawn, the foot of the sail is a maximum of 18 in above the gunnel. The boom version has the bottom of the boom about 10" higher on average, but I can't get that kind of height with the boomless version. I will also have to decide how important it is to me to have a mast that fits in the boat because this one is almost 2 ft longer than the boat.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    It looks like you have the halyard attached to the yard about halfway down the spar. My understanding is that it should be attached more like 35-40% of the yard length (starting from the throat of the sail).

    From what I can see, your sheeting point as drawn would be right at/near the transom, probably as far outboard as you can get it. That is fine--probably the easiest way to deal with that is to mount a horn cleat on the gunwale at each side, and shift the sheet manually from side to side as you tack. That's pretty much what I do in my boat with a boomless standing lug.

    I would not let a mast too long to lie flat in the boat be a deal breaker--getting a good rig is more important. There are a lot of ways to deal with a mast not fitting all the way inside.

    Tom
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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    You are correct that the sheet point how I have it drawn would be right at the transom. My drawing for the boomless rig is scaled from the drawing below which Todd Bradshaw created for Andrew Stokes and his Argie 15. I didn't check the halyard attach to the yard but now that you mention it, it does look a bit far aft.

    argie 15 with lug sail.jpg

    Incidentally, in Andrew Stokes build log of his Argie with this sail on it, he sailed with the boomless lug initially and then later he at least tried a boom on it and his comment was that it sailed better on all points of sail with the boom added. He didn't provide any more detail than that simple comment.

    As far as the mast fitting into the boat, that isn't necessarily a hard requirement but is definitely preferred if I can accomplish it. One of those things where you need to weigh all the pros and cons together. Still pondering.

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    I have a Dyer 12.5 that is a Rhodes design.
    Originally built in cold molded ply.
    Dyer still makes this boat.
    Rows superbly for a bigger boat. sails great.
    Two position mast so cat boat or sloop at your option.

    Powers only so so due to rocker at stern allowing the bow to rise with added power. f59a79646ea3ea912698dd8f828be0b3.jpg
    Ric in Richmond

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by 109jb View Post
    Incidentally, in Andrew Stokes build log of his Argie with this sail on it, he sailed with the boomless lug initially and then later he at least tried a boom on it and his comment was that it sailed better on all points of sail with the boom added. He didn't provide any more detail than that simple comment.
    Interesting. I think consensus among those who know boomless sails is that a boomless sail with the correct sheeting point (typically far aft and far outboard) is not typically worse to windward than a sail with a boom. That has certainly been my experience.

    I wonder if sometimes people see advantages to booms that don't really exist in practice.

    Tom
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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    While it might not matter to you, a jib gives the slot effect to the main sail, improving windward ability. In a fleet of 'classic' boats I found my gunter sloop could easily outpoint the assorted lug rigged boats. They may have been other factors, like foils (mine are to the designer's nicely shaped NACA ideas) But in general, a jib adds complexity, but improves performance.
    Set up time is minimal, the shrouds are attached to the boat and the rig is wrapped up with the mast. So, release the ties, put the foot into the step and hoist the whole lot with the jib halyard, cleat it off and pin the forestay. 'Bout ten minutes from arriving at the slip.
    A2

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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by WI-Tom View Post
    Interesting. I think consensus among those who know boomless sails is that a boomless sail with the correct sheeting point (typically far aft and far outboard) is not typically worse to windward than a sail with a boom. That has certainly been my experience.

    I wonder if sometimes people see advantages to booms that don't really exist in practice.

    Tom
    The Drascombe range mostly have boomless mains and also have a reputation for poor windward ability.

  29. #29
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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by WI-Tom View Post
    Interesting. I think consensus among those who know boomless sails is that a boomless sail with the correct sheeting point (typically far aft and far outboard) is not typically worse to windward than a sail with a boom. That has certainly been my experience.

    I wonder if sometimes people see advantages to booms that don't really exist in practice.

    Tom
    I asked him in his thread if he could expand on a few things, including whether the boom was just an experiment, or if he has switched to using the boom all the time. We'll see what he has to say.

  30. #30
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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by James River Rat View Post
    I have a Dyer 12.5 that is a Rhodes design.
    Originally built in cold molded ply.
    Dyer still makes this boat.
    Rows superbly for a bigger boat. sails great.
    Two position mast so cat boat or sloop at your option.
    Nice looking boat. Very similar idea and size to what I'm shooting for.

  31. #31
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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by James River Rat View Post
    I have a Dyer 12.5 that is a Rhodes design.
    Originally built in cold molded ply.
    Dyer still makes this boat.
    Rows superbly for a bigger boat. sails great.
    Two position mast so cat boat or sloop at your option.

    Powers only so so due to rocker at stern allowing the bow to rise with added power. f59a79646ea3ea912698dd8f828be0b3.jpg
    I don't sail, so look at Paul Gartside's lugsails for lugsail ideas; they are highly peaked. They do have a boom, but a crutch attached to the side of it so the boom locates on the mast without either a vang or preventer. Todd Bradshaw has described this feature as "underused". On some of his rowboats Paul Gartside also has boomless dipping lugs for offwind sailing; they are meant to be boomed out with an oar.

    About your hull:

    I like the boat in the picture above a lot and it gives you a clue as to how to design a chine boat with a chine that runs high in the bow and peters out before you get to the bitter end. There is a very similar boat called Martha's Tender, drawn at ~9' or 10' has been successfully lengthened to 12".

    To me this is a vast aesthetic improvement over that prominent chine low at the bow, but they say beauty is in the eye of the beerholder.

    Without even knowing about this Dyer 12.5 I've come up with a similar design (also using Freeship) to be built at 10' length in origami stitch and glue technique. So far a 1:8 scale model made from 1.5mm plywood has proven the concept, but the bow was a bit of a struggle. The full size panels out of 4mm Meranti plywood are lying scarfed up on my basement floor, not yet together. A 12' boat of similar proportion could probably be built out of 1/4" or 6mm ply, if not the 5 layer marine ply (stiff), then the "Home Depot" 3 layer ply, sheathed in fiberglass on both sides. I totally get Paul Gartside's ideas about saving tropical hardwoods, expecially for an experimental boat.

    Don't use underlayment to test the shape; I've got a cheap streak and worked with enough of that stuff to know that it rarely has the veneers approaching anything like equal thickness. This makes it bend quite differently from ply with more even veneer thickness.

    Just buy a couple sheets of 1/4" good one side fir or whatever, make sure it has waterproof glue, cut the front 8' of the boat, drill, zip tie it up. If the shape comes together take it apart, scarf on the last 4', make it your boat. If it doesn't work, go back to Freeship for a redesign.

    In that style of hull here is plenty of curvature in the bottom panel, both rocker and twist, and is should be plenty stiff. If this forum is to be trusted, the glass inside and out will confer better abrasion and impact resistance than one layer on the outside alone.

    Some high density plastic wear strips on the bottom wouldn't go astray if you are planning on dragging it on the ground. So far I've used that stuff only on dog sled runners but it will go on any boat I build for use in the real world, they call this island The Rock for a reason.

  32. #32
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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Quote Originally Posted by Andrew2 View Post
    The Drascombe range mostly have boomless mains and also have a reputation for poor windward ability.
    Tortoises have four legs and also have a reputation for poor land speed ability.

    Tom
    You don't have to be prepared as long as you're willing to suffer the consequences.

    www.tompamperin.com

  33. #33
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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    Booomless sails work perfectly to windward, provided you have sweated the sheet lead position, rigging, sail cut etc. Just look at a jib/ genoa: it's doing most of the work to windward. Correctly set, you will have the perfect blend of foot and leach tension/ twist. Additionally you don't have the weight or turbulence of the boom. Nor flattening of the bottom of a laced on sail. A standard mainsheet is a compromise position for the sake of simplicity: upwind you are getting disproportionate leach tension as you sheet in. You should also be able to extend the sail down a bit if your looking for area, as there isn't a boom to hit you. I would consider stays on the mast - that allows a lighter mast, and enables a taught sail. If you want to get to windward, you want a taught luff - as a mast bends the luff looses tension.

    Fundamentally ultimate power to windward is a function of luff length and that's the compromise if you don't sail a stayed bermudan sloop rig, and take benefits from another rig. Since a boomless mainsail like on Ilur is a fit and forget item, you could argue that you may as well make it out of reinforced shaped mylar rather than 'adjustable' dacron, it's just the asethetic doesn't match!

    An alternative approach on a boomless sail is to have a squared off clew with a clew board with three diagonal positions for the sheet attachement. That gives you three different sheet angles up for low, medium and high wind speeds: to alter the foot to leach tension proportion. The self tacking jibs on high performance dinghies do this. It's simple, cheap and easy for the days wind.

    Two sails are more efficient than one, and a jib is especially efficient to windward for its area, but for a simple boat and simple solo pleasures (not to mention less cost) I'd favour a single mainsail, at 12ft. A mast that ends up a bit longer than the boat makes a good cover ridge pole, but if it must fit in and be boomless, also look at a sprit rig: it's got the shortest spars for an area. If you must have a jib, sheeting an unstayed sprit in simultaneously tensions the forestay for upwind work, which is clever. I wouldn't worry about reefing - just don't over canvas it and at 12ft your body weight adds alot of weight on the rail. A simple small boat will likely only be used in ideal weather conditions. One reef would be more than enough.

    If you do use an engine, make sure you have a long tiller extension to fit it, as you will need to get your weight well forward to compensate for the aft engine. On that score the top of your transom at the engine mount will be defined by your engines immersed leg requirement - you will need to find out your shaft length/ look in the manual at the design stage, and consider engine trim angle. You would only need a light low power unit.

    Your optimum 12ft'er for sail, row and motor might be something like an Oughtred Gulliemot with the brailing single standing boomless lug fishermans sail option - it would be straight forward from a plank kit. I know you want to design your own boat single chiner, just sayin! It's nicer to own and easier to resell a beautiful thing.



    Also be aware that if you're not physically size limited to 12ft, a 15ft boat requires no more scarfs per plank in construction from 8ft sheets.
    Last edited by Edward Pearson; 11-02-2018 at 05:48 AM.

  34. #34
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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    The loose footed sprit main on my old snipa, was well positioned for going upwind, in that the beam of the boat aft was rather narrow, but that meant the sheeting angle was wrong for off wind work. After trying a balanced lug rig (with boom) on the same mast, i never went back. Not suggesting its perfect, but good all-rounder.

  35. #35
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    Nov 2009
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    Default Re: Sailing/rowing/motor sailing dinghy decisions.

    With a boomed sprit there is a simple emergency reef where you remove the sprit and it top of the sail flops over in the lee. Boomless sprits with brailing lines are wonderful when it comes to putting sail away quickly without shifting weight forward. Of course, the main benefit of a sprit would be shorter spars. I think you'll probably be very happy if you go with the lug for all the reasons mentioned.

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