Rowing friendly lateen JR conversion for cartop sailing dinghy?

  • 13 Nov 2022 23:59
    Reply # 12987862 on 12987387

     I have to suggest one think only, contact Arnie, once you choose to use his method. He will have all the answers on all your questions. He had great experience and knowledge. Good luck!

    That is a great suggestion. I am now more convinced that I can make an Arne-style rig work on this boat. I was reviewing prices for aluminum tubing, and experienced some despair, but turning to PJR, I think that I will plan on ash battens which can be sourced very economically here and I have the tools already to make them from the raw lumber.

    The last thing that I want to try is thinking through how I will rig the mast and the sail bundle into the boat. In my imagination, I can position the sail bundle with batten parrels opening over the mast partner and halyards and lazy jacks fed to the top of the mast and then raise the mast through the batten parrels and down into the partner to the step. To be more sure of that, I might try another mock-up just to see where all the strings go.


    -Neil

    Last modified: 13 Nov 2022 23:59 | Anonymous member
  • 13 Nov 2022 08:28
    Reply # 12987387 on 12986547
    Anonymous wrote:

    IAnonymous wrote:.

    That is likely you only choice for keeping your mast at least close to where it is now.

    I would also read through the thread for the dingy contest where a three panel (maybe four?) JR with battens that could be stowed up against the mast for rowing. This seems to tick the most boxes for your need. The sail is reefed as normal for the bottom panels, then when there is only the top triangle panel left, the boom and battens can be lifted up against the side of the mast and tied in place. To remove from the boat, leave this bundle tied as is and remove the mast, sail and all in one piece. This is a very quick description lacking most useful details to actually make such a sail.

    I did some sketching and it looks like you are right on. The CE for the existing rig is 40 inches behind the mast. I don’t think that I can move the mast step very far from there. In a low-balance rig like Arnie’s, there is 10% balance, so roughly 40% of the chord is between the mast and the CE (which Arne says is over the midpoint of the chord. Since the 40 inches is fixed, that means the chord must be 100 inches.

    But on a high-balance sail like Slieve’s, 30% of the chord is ahead of the mast, so the section between the mast and the CE IS 20% of the chord (all approximate, but I think close enough?) which implies that the full chord of the sail would have to be 200 inches or more than 16 feet on a 16 foot boat.

    So, let’s go with Arnes sail plans. Picking an area of 100 square feet gives the aspect ratio of 1.8 (the chord is fixed, if you want more area, you go higher). I sketched it and built a mock-up, with string and hot glue. It looks reasonable enough.

    I was wondering about using fewer panels to simplify construction and reduce weight. Do we have good rules for fabric weight and batten dimensions for sails around 10 square meters? Most of the cruising sails that I see around JRA are quite a lot bigger, so I’m not sure how to scale down batten sizes, especially as I’d prefer to use timber rather than alloy for cost and scrounge-ability.

    -Neil

    Hi Neil,

     I have to suggest one think only, contact Arnie, once you choose to use his method. He will have all the answers on all your questions. He had great experience and knowledge. Good luck!

    -Tzvetomir

    Last modified: 13 Nov 2022 08:30 | Anonymous member
  • 12 Nov 2022 03:58
    Reply # 12986547 on 12984217

    IAnonymous wrote:.

    That is likely you only choice for keeping your mast at least close to where it is now.

    I would also read through the thread for the dingy contest where a three panel (maybe four?) JR with battens that could be stowed up against the mast for rowing. This seems to tick the most boxes for your need. The sail is reefed as normal for the bottom panels, then when there is only the top triangle panel left, the boom and battens can be lifted up against the side of the mast and tied in place. To remove from the boat, leave this bundle tied as is and remove the mast, sail and all in one piece. This is a very quick description lacking most useful details to actually make such a sail.

    I did some sketching and it looks like you are right on. The CE for the existing rig is 40 inches behind the mast. I don’t think that I can move the mast step very far from there. In a low-balance rig like Arnie’s, there is 10% balance, so roughly 40% of the chord is between the mast and the CE (which Arne says is over the midpoint of the chord. Since the 40 inches is fixed, that means the chord must be 100 inches.

    But on a high-balance sail like Slieve’s, 30% of the chord is ahead of the mast, so the section between the mast and the CE IS 20% of the chord (all approximate, but I think close enough?) which implies that the full chord of the sail would have to be 200 inches or more than 16 feet on a 16 foot boat.

    So, let’s go with Arnes sail plans. Picking an area of 100 square feet gives the aspect ratio of 1.8 (the chord is fixed, if you want more area, you go higher). I sketched it and built a mock-up, with string and hot glue. It looks reasonable enough.

    I was wondering about using fewer panels to simplify construction and reduce weight. Do we have good rules for fabric weight and batten dimensions for sails around 10 square meters? Most of the cruising sails that I see around JRA are quite a lot bigger, so I’m not sure how to scale down batten sizes, especially as I’d prefer to use timber rather than alloy for cost and scrounge-ability.

    -Neil

    2 files
  • 10 Nov 2022 00:03
    Reply # 12984217 on 12984096
    Anonymous wrote:

    1. A split-junk rig with running topping lifts. That should let me row while the sail bundle sits over my head, maybe even reefing up for the first reef? My concerns are around rigging time and complexity for the topping lifts, halyard, and yard hauling parrel. I also don’t have a good sense of how large and heavy the sail bundle will be to pack up.

    Looking at the rig you are using, this would require moving your mast aft to keep the CE in place (well I guess you could move your centre board forward...). Before jumping at that idea, take full consideration of where you will stow your supercargo (Family).

    2. A barrel-cambered junk rig, otherwise similar to the previous choice. I have a hard time as a JR beginner keeping track of just how many lines the Arne-style sail is going to have for me to handle in a small boat. I think that the Ah-Sup sheeting system as described in the newsletter should allow a single mainsheet in hand while still allowing anti-twist adjustment.

    That is likely you only choice for keeping your mast at least close to where it is now.

    I would also read through the thread for the dingy contest where a three panel (maybe four?) JR with battens that could be stowed up against the mast for rowing. This seems to tick the most boxes for your need. The sail is reefed as normal for the bottom panels, then when there is only the top triangle panel left, the boom and battens can be lifted up against the side of the mast and tied in place. To remove from the boat, leave this bundle tied as is and remove the mast, sail and all in one piece. This is a very quick description lacking most useful details to actually make such a sail.


    3. An Aerojunk. I really like the simple sheeting system that runs down through the batten ends, and the single halyard. I think that with topping lifts, it should

    Stowage, complexity and cost. I agree that putting this on your roof would mean more disassembling to fit. I think it would take longer to build... but that is really a guess, someone who has built one would know better. Cost always depends on scrounging ability, considering your costs so far, you must be pretty good.


  • 09 Nov 2022 22:26
    Message # 12984096

    I finished my first ever boat build this summer, a 15.5 foot flat-bottom sailing dinghy named Hum. The existing sail as suggested by the designer is the 76 square foot (7.1 square meter) lateen rig from a Sunfish. We had two really fun family trips this fall and I learned lots about how the rig works with the boat. The good news is that everyone had fun and we got home safe and learned to sail on a reach and a run. The bad news is that we didn’t have as much luck sailing upwind and when we had to get back to the dock on time going upwind, we needed to drop the sail and row. The really awkward news is that the 14 foot long booms of the lateen sail can’t stow below the sheer because they hang over the stern and then it is very difficult to row efficiently. (See the second photo for an example launching from the dock.)

    This winter I would like to re-rig the boat for a better experience mixing rowing with sailing. I am in love with junk rigs and the JRA and would like to seriously consider how a junk rig could meet my needs. (Another option would be to buy or make from a kit a balanced lug sail like many sail-and-oar dinghies have these days.)


    Here are what I think my needs are:

    A. I need to be able to lower the sail and still be able to row efficiently.

    B. I need to be able to rig the boat from cartopped to sailing in a reasonable amount of time, say 30 minutes or less. (Yes, I cartop a 4.7m boat that weighs 50kg, see photo.)

    C. I need to be able to pack the sail alongside the hull on top of the car (see photo). Right now I roll the sail around the boom and mast and tie a chain sinnet around the bundle with the sheet and halyard.

    D. I need fairly simple running rigging as a beginning sailor in a small boat with lots of kids. This summer I managed a main sheet and a tiller in my two hands but just barely.

    E. I need to be able to afford the new sail and spars and mast. My budget for this is in the neighborhood of $300, which is around 60% of what the rest of the boat cost to build so far.


    I have done lots of JR reading including most of PJR, Arne and Slieve’s design notebooks and the last 25 issues of the Newsletter, especially the dinghy issue. Here are some of the possibilities I am considering:

    1. A split-junk rig with running topping lifts. That should let me row while the sail bundle sits over my head, maybe even reefing up for the first reef? My concerns are around rigging time and complexity for the topping lifts, halyard, and yard hauling parrel. I also don’t have a good sense of how large and heavy the sail bundle will be to pack up.

    2. A barrel-cambered junk rig, otherwise similar to the previous choice. I have a hard time as a JR beginner keeping track of just how many lines the Arne-style sail is going to have for me to handle in a small boat. I think that the Ah-Sup sheeting system as described in the newsletter should allow a single mainsheet in hand while still allowing anti-twist adjustment.

    3. An Aerojunk. I really like the simple sheeting system that runs down through the batten ends, and the single halyard. I think that with topping lifts, it should be possible to drop it and still row with the large bundle of framework battens above my head? I am concerned about being able to pack the sail bundle onto the top of the car and with the cost of aluminum tubing and other metal parts, I'm also worried about overall cost.

    Does anyone have any feedback on how to choose among these options for a small sail-and-oar dinghy? What would you choose from your much-vaster-than-mine experience? Would anyone want to speak in favor of the balanced lug and giving up on all the JR complexity in this particular situation?


    Thanks in advance for any tips and ideas you can share. And thanks already for all of the valuable materials that so many of you have produced and made available through the JRA.

    -Neil

    3 files
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