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Van de Stadt 36 Seal - JR conversion

  • 19 Nov 2020 05:12
    Reply # 9374619 on 9338306

    Greetings Arne,

    In your various suggestions for a large sail sloop rig for Falkor you state “The biggest challenge is to build a tall and strong enough mast at a moderate weight and cost.”

    What would be the specs for a suitable mast in, for example, your most recent iteration of a 65.6 square metre sail?


  • 18 Nov 2020 15:30
    Reply # 9372907 on 9338306
    Anonymous member (Administrator)

    Good, Eero.
    Then I guess I would suggest one of the two last rigs I have presented.
    The light winds in the Bay of Finland during summer, speaks for the last one; the one with AR= 2.40 and SA= 65.6sqm.
    However, we don’t get younger as the years go by, and the shorter 13.4m mast is cheaper and easier to deal with than the one at 14.9m...

    As for performance; even the smallest JR will outperform the masthead Bermuda rig on the downwind leg. Close-hauled, I guess I would put my money on the BR, in light winds.

    The only ‘hard’ job when sailing with a JR, is hoisting the sail. On your boat, that can easily be overcome with an electric capstan. Some of these are meant for hauling up the anchor, and are not terribly expensive. Hoisting the sail from bottom to top will drain a 12V battery with less than an Ampère-hour.

    Anyway, rigging the boat with two sticks will cost a lot more  -  I would say, forget that.


    When organising the sheet, it is important to give them a good layout to make them easy to haul at by hand and via manual winches.

    Arne

    PS: I have sent the drawing in QCAD (.DXF format) to David, to let him suggest a rig. If others will have a go, and can handle that format, just let me know.

    PPS: In case the mast position I have suggested results in awkward access to the fore-peak, the mast may well be moved 10-15cm forward, and it can even be offset 10-15cm to one side, without suffering any handling problems.


    Last modified: 18 Nov 2020 23:21 | Anonymous member (Administrator)
  • 18 Nov 2020 14:36
    Reply # 9372814 on 9338306

    Arne, David, Graeme,

    Thanks for your comments and input. Very much appreciated!

    Arne, in the scale (0-100) I would say I am 45% sailor. Pure cruising. Focus is on safe, comfortable, and enjoyable sailing. The crew is 60 year-old couple, whose idea is to leave the regular work within say 2-3 years and the boat will be our liveaboard for maybe 6 months per year. Nowadays we sail the ‘normal’ summer holiday sailing i.e. daily trips along coasts of Gulf of Finland and Northern Baltic Sea. But once we get rid of the tight schedules, the trips will get longer but leisured. We can keep the boat abroad and no need to dock the boat for every winter. Perhaps not crossing oceans but exploring canals, rivers etc might be nice. For that purpose, a shorter mast(s) would be nice as they could be carried on deck if the overhang is not too much. For that reason, we have also considered if we should switch the boat to a smaller one with a smaller draught. But on the other hand, this is a nice and cozy liveaboard boat giving very safe and comfort ride at open sea.

    The present sail area is main 25.7, furling genoa 37.3 making 63m2 in total (hopefully I managed to measure them correctly). We have a few more sails, but in practice we keep those home. I would guess that a JR of the same size would be much more efficient downwind, as without a spinnaker/gennaker we loose a lot of effective area of the genoa. The present balance is quite good I would say based on the rudder angle. Difficult to say because the hydraulic steering gives almost none sense of the pressure. I am used to tiller, which I keep as my favorite way for steering.

    Eero     

     


  • 18 Nov 2020 11:42
    Reply # 9372402 on 9338306

    Good, Arne. I like the reasoning, and I like the end result.

    Except for the missing forward rake ...

  • 18 Nov 2020 11:00
    Reply # 9372358 on 9338306
    Anonymous member (Administrator)

    OK, I put the blame on the Corona half-shutdown and the never-ending rain here. Now I have sketched up yet another JR for that 11.0m/9.25 ton Seal.

    David Tyler’s notes below made me sober up a bit. I can see his point that handling a very big, single sail can be too hard as the size of the boat grows. Problem is that we people stay at the same size no matter if we are sailing a nutshell or a ship. This time I have kept the chord of the sail moderate (5.71m), and made the sail taller by simply adding a panel to the last sail I showed to you. This way the sail area goes up from 57.4 to 65.6sqm and the SA/displacement  now reaches 15.1. The AR goes up from 2.15 to 2.40.The mast position is un-changed.

    What I like with this is that we end up with a taller sail than the original, but still with a shorter mast. In addition, there is plenty of space for the (double, upper-lower) sheets. My hunch is that the boat will be at least as fast as with the original rig on all courses, and thanks to the moderately short chord of the sail, the downwind steering will be easy.

    The biggest challenge is to build a tall and strong enough mast at a moderate weight and cost.

    Cheers,
    Arne


    Last modified: 18 Nov 2020 12:51 | Anonymous member (Administrator)
  • 17 Nov 2020 21:04
    Reply # 9371005 on 9338306
    Anonymous member (Administrator)

    Eero,
    I realise that I jumped into drawing mode too early. Before presenting any sketches, I should have asked a few questions (I see now that you have hinted about it in your profile):

    • ·         Where on a scale from 0-100 do you regard yourself to be (0 = motorboatman, 100 = die-hard pure sailor)? How much do you focus on sailing itself?
    • ·         What waters will be your preferred to sail in for the next five years?
    • ·         How many people will you be on board, mostly?
    • ·         How big SA do you actually make use of today, with the original rig?
    • ·         How is the helm balance with the original rig?

    I will not argue for or against any rig or sail area until I learn more about your needs.

    However, just for fun, I have now added a ‘minimum rig’ of 57sqm (same mast position and CE). This would result in a SA/Disp.=13.2. See below.


    As for rudder incorporated in the CLR or not, I generally avoid that, in particular with sloop rigs. I try to end up with about neutral helm when close-hauled in light winds, and keep the rudder ‘as a spare’ for controlling the boat on a beam-to-broad reach in rising winds.

    Arne


    Last modified: 17 Nov 2020 21:13 | Anonymous member (Administrator)
  • 17 Nov 2020 09:44
    Reply # 9369642 on 9338306

    Eero,

    As you may know, on a similar sized boat, Tystie, I went from 1 mast to 2 masts to 1 mast to 2 masts, over 15 years and 85,00 miles. After all that experience, I would venture to say that there isn't a single right answer, only a compromise that kind of works for you. I think that 55 sqm is as big as I would want to go in a single sail, unless that sail is either of maximum AR or is a SJR. Then up to 65 sqm becomes reasonable to handle, but really, the 80 sqm of Peregrine is way over the top for an offshore cruising boat, though it might be fun on short passages.

    So, if you go for a single sail, I would make it with as high an AR as the the boat will stand, and I think I see in your sketch 3 that you think the same. With that single sail, maybe you could put some forward rake on the mast, as was done on Fantail with the aim of not ruining the bed. 

    I like Graeme's suggestion of a SJR as well, but I think for this boat the sail should be of high AR, and would need 7 or 8 sheeted points, with upper and lower sheets. These are not nearly so bad to handle as port and starboard sheets on a schooner rig.

    I don't see a better form of schooner rig than the one that you've drawn. The sheeting looks tight for single sheets, but not completely impossible.

    On balance, I think I'd go for the single high AR sail in sketch 3 set on a mast with about 3˚ of forward rake, which should put it clear of the L shaped seat and water tank, leaving only the table to be rebuilt. On a practical, pragmatic level, the battens for this sail seem to be 6 metres long, which is sensible in terms of available materials and in manageability when rigging and repairing the sail.

    Last modified: 17 Nov 2020 10:52 | Anonymous member
  • 16 Nov 2020 21:31
    Reply # 9368674 on 9338306
    Anonymous member (Administrator)

    There is another possibility if you want a sloop rig with the mast a little further aft, and that is to consider a SJR, which typically has higher balance.

    Here is one of Slieve's SJR sails superimposed over Arne's Johanna sail, with the geomtric centre lines of the two sails in the same position.

    As you can see, this puts the mast centre line somewhat further aft.

    In the current "Featured Boat" you can read that Pete H. put an aerojunk rig on Blossom to solve an accommodation problem in much the same way.

    When placing a SJR sail plan, people have found that the geometric centre line of the SJR (near enough to a vertical line through the mid point of the boom) can coincide with the geometric centre line (through the so-called "centre of effort") of the original bermudan rig. This makes use of an assumption that the original bermudan rig is in the right place with regard to under water profile, rudder etc.

    The above drawing will be pretty close to that).


    I am not sure if this helps. Also not sure if a single sail as large as that is a practical proposition !) but if you want a sloop, it is another possibility to consider.

    In the current "Featured Boat" you can read that Pete H. put an aerojunk rig on Blossom to solve an accommodation problem in much the same way.
    Last modified: 17 Nov 2020 01:23 | Anonymous member (Administrator)
  • 16 Nov 2020 19:14
    Reply # 9368348 on 9338306

    Arne,

    first: sorry for this long radio silence. My work has kept me busy and I wanted to do my homework and try to find suitable places for the mast(s)

    Yes, you are right, it seems to be very difficult to fit the mast for a sloop version so that the lead is ok, but also not standing in the middle of my beloved bed. That is pity, I started to get fond of the sloop version because of its simpleness. Modifying the cabin layout leads to a major project which I try to avoid.

    The schooner version seems a bit easier with the masts, but there seems to be very little space between the sails leading to double sheets and that sounds like a mess. I want to go for simpleness and not to make complicated solutions. Therefore, the sloop version seems so tempting.

    When locating the CLR should I include the rudder? In this boat, with a big rudder it makes a difference as can be seen in the attached sketch. It bothers me that lead of the current version is more forward than the recommendation.

    Eero

    PS. I tried to upload a DXF version also, but the format seems not to be supported for upload.


    1 file
  • 02 Nov 2020 13:15
    Reply # 9340029 on 9338306
    Anonymous member (Administrator)

    Eero,

    just a quick note.

    Sail area:
    It was Sailboat Data which suggested about 79sqm, probably with Genoa 1 set. I would say that 63sqm puts your boat low in the motor-sailer class.
    I suggest you have a closer look at Peregrine in this rally report from 2010. She does well with that rig. http://goo.gl/KIOwkH

    The challenge is to build a strong enough mast, which does not add more than 2.5-3.0% weight to the boat. The sail may look big, but it can easily be reefed, so is much less fuss than a big Genoa, or a 2-masted JR..

    Mast position.
    It is difficult to avoid having a mast in the shown position. There  are two views on this around. One either simply cannot have a mast there, ore one decides to live with them, as I have done.

    Balance.
    After you showed the CE of the Bermuda rig, I have had another go and moved the sail further forward on the mast, without moving that. To get the halyard right, that is, just a little aft of the mast, I have lowered the yard from my ‘normal’ angle of 70°, down to 65°. This lets the sail sit with about 21% balance with respect to the mast.

    Cheers,
    Arne

    PS:
    My QCAD program cannot find the centre of area of any polygon, so now I have printed out the sail and found its CE ( or COA) the old-fashioned way. It turns out that it only sits a few millimetres forward of the middle of the boom, so that can be used when finding the lead.

    Last modified: 03 Nov 2020 18:16 | Anonymous member (Administrator)
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