Fisher 30

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  • 01 Oct 2022 11:45
    Reply # 12938705 on 12929596
    Anonymous member (Administrator)

    On the 28th September, Graeme discusses how to shift the CE back and forth of the Johanna-style sail by increasing or reducing the aspect ratio. I have used the method a bit in my own designs, but this will not work for all, when the sail’s mast balance (Graeme calls it batten balance) can only be varied between 10-12 and 17% (one may stretch this gap by increasing the halyard span or moving the slingpoint closer to the middle of the yard.).
    The attached diagram shows the original “Johanna 70” master sail with the 70° yard and with AR=1.90, and then the Johanna 65, 60 and 55 models. The three other models are based on the original one, but with redesigned top sections.
    So now, when I find I need a sail with for instance 21% mast balance, I go to my stack of master sails, find the one with the right AR to get the desired area, and make a “Johanna 65” version of it.
    Maybe, during the winter, I will make a complete string of master sails with these new yard angles.

    As for the Johanna 55 model, I cannot recommend using it until experience has been gained with sails with this much mast balance.


    Last modified: 01 Oct 2022 17:13 | Anonymous member (Administrator)
  • 30 Sep 2022 23:12
    Reply # 12938368 on 12934743
    Anonymous wrote:

    Is the back stay necessary? Could it be done away with and the mast held up with a pair of side-stays on each each like on my Westerly22 who's deck-stepped mast has "stayed up" for nearly 60 years with out a back-stay? Plenty of room for a junk main on the existing mast, especially on a motor-sailer that isn't looking for racing performance. 

    The Westerly 22 has no spreaders while the fisher does. I do not know if that makes a difference. I would think in that case the aft shrouds should be 45 degrees back. The back stay's main purpose is to balance out the fore stay but the fore stay is only there for the jib. So if a jib is not being used anyway, the back stay may not be needed. 

    This of course, assumes the current mast position can be made to work. I think it could by varying the sizes of main and mizzen.

  • 28 Sep 2022 10:42
    Reply # 12934743 on 12929596

    Is the back stay necessary? Could it be done away with and the mast held up with a pair of side-stays on each each like on my Westerly22 who's deck-stepped mast has "stayed up" for nearly 60 years with out a back-stay? Plenty of room for a junk main on the existing mast, especially on a motor-sailer that isn't looking for racing performance. 

    1 file
  • 28 Sep 2022 06:11
    Reply # 12934600 on 12929596
    Anonymous member (Administrator)

    Len, yes if you do it that way, by keeping a constraint on sail area in addition to a constraint on batten balance, then you are right: the sail with a higher aspect ratio will have a centre of area which is closer to the mast centre line. You are correct in that case.

    I hadn’t thought of calculating it that way – in fact I was looking at Arne’s three model sail plans (AR 1.8, 2.05 and 2.25) in which for comparison all three sails have the same chord length and their centres of area all lie on approximately the same vertical line same - but, of course, they do not each have the same area.

    So, following your reasoning and keeping the sail area constant, let us scale down the AR 2.25 sail in Arne’s suite of sails, so that it has the same sail area as his AR 1.8 sail. The scale factor for that area transformation will be 35.31/46.46 which is about 0.76. Using the square root of that, for a linear scale factor, that taller sail will now have a chord of about 4.36. If both sails are now given the same batten balance (let us say 10% of chord) the centre of area of the AR1.8 sail will be 2m aft of the mast centre line, compared with the centre of area of the AR2.25 sail which will be 1.64m aft of the mast centre line. 

    So as a result of that drastic change of AR (from 1.8 to 2.25) we can in theory get about 36cm of “wriggle room” when it comes to mast placement – provided the batten balance is not more than 10%. As you have hinted yourself, this is not a very rational way to choose the aspect ratio of your sail, as a number other important factors are also involved.

    Furthermore, I think when you were discussing aspect ratio you were doing so in the context of a split rig. A split rig really makes no sense at all unless the batten balance is at least 30% or more, so while we are in the mood to do a little arithmetic, let us also consider the same question in relation to a batten balance of 33%, which is probably the optimum for a split rig. In that case, a change of aspect ratio from 1.8 to 2.25 would lead to the centre of area being 0.85m aft of the mast centre line in the first case, compared with 0.73m in the second case – a difference of 12cm in regard to Arne’s suite of model sails. This is not an exact business, and 12cm is surely within a reasonable margin of error, that is to say: negligible on a 30’ long-keel vessel.

    Summary: I think we both agree that the starting point is to have some idea of where the centre of area of the sail plan should probably lie. From there, the goal is to find a sail type which is centred there and, as far as possible, is in harmony with the requirements of the type of vessel, its internal layout, placement of berths, hatches, sheeting position etc. If there is a preferred place for the mast, then this will largely dictate batten balance of the sail, though in some cases a little bit of fine tuning with mast rake and (as you have rightly pointed out) aspect ratio might also make a small difference. If batten balance of more than 30% is dictated by the preferred mast position, then a split rig might be the answer but I would not venture to allow more balance than about 33% (35% if you want to be a pioneer) and in that case aspect ratio would not make a lot of difference in the quest for helm balance. I suppose it could be argued that every little bit helps, so your suggestion was good, and thanks for correcting me.

    The important point to keep in mind, in my opinion, is that the split rig may in some cases be the perfect answer (I am very pleased with mine) – but it is probably one of the least amenable to being used as a platform for experimentation and, of all rigs, offers the least amount of opportunity for adjustment later if things don’t quite work out in regard to helm balance.

    All this academic stuff is perhaps a little less crucial when it comes to the vessel which is the subject of this thread. The nice thing about this Fisher 30 is that it will have a good auxiliary engine – but more importantly in regard to this discussion, it has a long keel which ought to make it a little bit more tolerant to small variations in the position of the sail plan – and it presents the potential for a ketch rig which, as Arne has pointed out, allows the sheeting of the mizzen sail to contribute towards adjusting helm balance. Personally, I am very much in agreement with Len's sentiments, and would rather love to have a Fisher 30.

    Last modified: 28 Sep 2022 06:51 | Anonymous member (Administrator)
  • 28 Sep 2022 00:19
    Reply # 12934368 on 12934209
    Anonymous wrote:

    The aerodynamic balance of the sail (perhaps Arne's "batten balance" is a better term) is an entirely different matter to the helm balance of the vessel, which is what you will be seeking when you convert your Cal 29. Another point: by "CE" I presume you are referring to the geometric centre of area of the sail. When a sail is scaled vertically (to increase or decrease aspect ratio) the geometric centre does not move fore or aft.

    Well, lets draw out two sails, one with an AR 2 and one with an AR 1. The mast remains at 10% of the chord aft of the luff, The area remains the same. To be simple lets use 100 square units.

    In the case of an AR of 1, the sail is 10x10, the CA of the sail is 5 units back from the luff or 4 units back from the mast.

    In the case of an AR of 2 The sail is now 14.14 units high and has a chord of 7.07. Now the CA is 3.5 units aft of the luff or 2.8 units aft of the mast.

    So yes, the CA does move fore and aft with respect to the mast with a change in AR. Perhaps you meant that the CA needs to remain in the same place along the length of the waterline, which is true. However, In this case I was talking about using the AR to move the CA fore and aft while not moving the mast so as not causing more trouble to one's interior than needed. That is, assuming the mast can't move but the sails CA is not quite in the right place. A change in AR could correct that without moving the mast.

    Hopefully no one is contemplating an AR of 1  :)

  • 27 Sep 2022 22:15
    Reply # 12934209 on 12929596
    Anonymous member (Administrator)

    Len: "The jiblets could be moved fore and aft to affect the balance and see if some movement would help..." and also "Comments on why this would be really bad...

    The above is a really bad idea. The reason is that a properly designed split junk sail is already near to the limit of what is possible in terms of aerodynamic balance of the sail itself, and if you step over that limit the rig will become unsafe and not functional. Furthermore, if you go the other way and reduce the aerodynamic balance of the sail, then pretty quickly it becomes unnecessary and pointless to put a split in the sail.

    The aerodynamic balance of the sail (perhaps Arne's "batten balance" is a better term) is an entirely different matter to the helm balance of the vessel, which is what you will be seeking when you convert your Cal 29. Another point: by "CE" I presume you are referring to the geometric centre of area of the sail. When a sail is scaled vertically (to increase or decrease aspect ratio) the geometric centre does not move fore or aft.

    I believe that with a contiguous sail it can be possible to sling the sail a little fore or aft, and perhaps to alter the rake of the mast in order to gain a little flexibility with regard to mast position. However, one of the downsides of the split rig is that there is very little flexibility in that regard. I don't think tinkering with the geometry of the sail is a wise idea. 

    (Incidentally, I should mention that the SJR proposition for the Fisher 30 was not done with any careful calculation but merely for discussion, as an option to consider if the aim were to make minimal changes to the layout of the vessel. The correct approach for SJR would be to calculate the geometric centre of the area of the proposed sail plan and compare it with the geometric centre of the area of the original designed rig - talking into account any known characteristics of the original design (ie whether the helm balances nicely, or if there tends to be excessive lee helm or weather helm) and from this, a decision is made regarding mast position. My gut feeling with putting a SJR mast on that current mast position is that it may be a smidgeon too far aft, but with that long keel you could probably get away with it. The mizzen sail  might be better reduced to a smaller "riding sail" and might be redundant a lot of the time. I think Arne's suggestion, utilising the existing mizzen sail as a working sail, might be the better solution.)

    Back to the Cal 29, Len wrote: I will start a thread when I actually own the boat and have gotten used to things the way they are (the main sail has only a year or two if I am gentle with it).   That is a really excellent suggestion. After a season of getting to know the boat, most of the need to speculate, as above,  or to experiment with sail geometry, will probably disappear. The answers will fall into place.

    (An afterthought: this is in no way to disparage the origami concept. This is of interest in its own right - but not as a platform for experimenting in the manner Len was proposing, I would suggest).

    Last modified: 27 Sep 2022 22:53 | Anonymous member (Administrator)
  • 27 Sep 2022 03:56
    Reply # 12933320 on 12929596

    Hmm, Arne's drawing confirms what I thought. If you want to use the v berth as a double you would end up with a pole in the middle of the V- berth. That is probably the best place for it with that style of sail. For many people the v-berth is just sail and other stowage anyway, in which case that may be the best solution.

    The SJR looks like the best possibility for keeping the mast where it is.

    I do not know if this next idea is a good idea or a very bad idea  :)

    I wonder if it is possible to keep the mast you have, rigging and all, and try out an SJR origami style (see JRA magazine issue 85) using tarp cut and sewn (glued?) as a trial. The bad side is that the rigging will be in the way and wear the sail quickly... but poly tarp will only last a year anyway. Tacking or gibing will mean lowering your sail under the back stay(s). This is _not_ a permanent solution. However, it would allow you to see if the balance will work. The jiblets could be moved fore and aft to affect the balance and see if some movement would help. This would require longer battens than needed. Also, the AR will move the CE fore and aft as well. A higher AR will move the CE forward and a lower AR will move the CE aft, though not as much as with a normal JR where the mast is only about 10% aft of the luff. Of course a higher and lower AR will affect other things as well (mast height for one).

    The idea would not be to try a full 5 or 7 panel sail but rather maybe 3 panels with a stiffer wind. In other words the trial would be a reefed version of your final sail, remember, there is a back stay in the way (though in your case the back stay might be higher going to the top of your mizzen mast). If you can get enough of your sail plan set up to test things as needed without hitting the back stay, even better.

    Comments on why this would be really bad... or ok, are more than academic to me as well because I am in the process of buying a Cal 29 I would like to try this with. I have a choice of three easy placements of the mast (yes I do need my full V-berth thank you). Where it is (best solution), two feet forward (might be a bit more) or two feet back (well lets say "up to" two feet back). That is in order of best to least desirable. That is, aft wall of the head, forward wall of the head or beside one of the settees (though "out of the way" it would make sitting at the table a pain. I will start a thread when I actually own the boat and have gotten used to things the way they are (the main sail has only a year or two if I am gentle with it).

    Finally, pilot house: yes!. As someone living in the PNW (Canada not the US), a pilot house means the difference between using your boat for the summer or the ability to use it spring and fall (most years there are only three seasons). That may be a motor sailor but it looks nicer than the average motor boat (troller, tug knockoff or trawler). Very pretty.

    Last modified: 27 Sep 2022 04:06 | Anonymous member
  • 26 Sep 2022 10:41
    Reply # 12932100 on 12929596
    Anonymous member (Administrator)

    Graeme, the maths around the SA/Disp. can be found here. I don’t like this ratio that much myself. The heavier the vessel, the less likely one is to reach a SA/Disp=20. However, on boats of similar displacement, that number can be useful for comparison.

    As for ‘quiet’ sail, I don’t mean the cambered sail is flapping in headwind, as it doesn’t do that (watch this short video clip of dropping a panel on my Ingeborg:

    What I meant was that the cambered panels will ‘plop’ quite loudly if the boat is rolling from side to side with the sail sheeted to the CL. Anyway, this is not good for the sailcloth in the long run.

    The CE of my junk sail is sitting closely to the combined CE of the mainsail plus jib of the Bermuda rig. I therefore reckon that the load on the rudder will be determined by how hard one sheets in the mizzen. It may well be an idea to make a new mizzen as a flat triangle, suitable for riding at anchor etc.

    I would no doubt add an endplate to both the upper and lower end of the rudder. Combined with the benefits of the mizzen, I think the boat should steer all right.


  • 25 Sep 2022 23:14
    Reply # 12931709 on 12929596
    Anonymous member (Administrator)

    Arne, could you run through those numbers again and explain the SA-displ. ratio? According to Sailboat data the Fisher 30m displaces 6.6 tonne. I am not clear about how to do this calculation.

    (I have never quite understood this ratio either - I wonder why SA-wetted surface is not considered more important).

    Another advantage of flat sail for motor-sailer (as I have been informed) is the ability to motor in alternating light and calm conditions with the sail just sheeted in tight. I don't think "quietness" is an issue (with the engine running anyway) but I presume what Arne means by this is that the sail is "quiet" ie not flapping as would be the case with a cambered sail. This is a good point.

    However I am inclined to agree with Arne, a boat with a keel like this should sail well enough and more important is the incentive to sail rather than just motor all the time, as so often fully powered sail boats seem to do these days. In that case a moderate-heavy displacement boat with a full keel needs a sail which gives as much drive as possible - at least for coastal sailing anyway.

    When I first saw this post, with Aaron's questioning of the mizzen sail, and his focus on the current mast position, I thought along different lines, and did wonder if a high balance junk sail on the current mast position might work. The SJR sail shown here is also well-proven. Just for the sake of discussion: the mizzen sail  might be reduced to something of more yawlish proportions. This keeps the main mast about the same height and in its current position - and with over all about the same sail area as current.  There is probably room there for a slightly taller mast and a bit more sail area. (And might lead to some head-scratching regarding the sheeting arrangement, but not impossible). 

    I have always rather liked the looks of this boat as a cruiser for living aboard - though I have never seen one "in the flesh" here in New Zealand (I believe there is one). After 10 years commercial fishing I can say that a wheel house is a most wonderful accoutrement and I dearly wish I could have one again. That little working-boat-style steadying sail aft is always an asset, and looks the part, too, though it may remain furled much of the time.

    However if this boat were mine, and the accommodation layout were suitable, I would go for Arne's suggestion and get that extra bit of sail area. With extra sail area I would worry a little about that rudder - I think Arne has nailed it though, by retaining the full two-masted rig.

    Last modified: 27 Sep 2022 22:58 | Anonymous member (Administrator)
  • 25 Sep 2022 11:47
    Reply # 12931359 on 12929596
    Anonymous member (Administrator)

    Hm, I struggle with this one.
    The Fisher 30, with its very low SA/Disp. ratio (around 8.7) is more like an 80% motor-vessel with an aux. rig. I have seen a few of such boats motoring around, but hardly ever with any sail set. However, the Fisher 30 has a decent keel and plenty of ballast, so should be able to carry a much larger rig than the original. A quick, preliminary study tells me that one could fit a JR mainsail with the mast at the aft end of the foredeck. This could end up at 40-42sqm without a too tall mast. By keeping the mizzen un-changed, the total SA should reach about 47sqm (instead of about 30qm) and thus move the SA-disp. up to 13.6, which is decent for a motor-sailer.

    Annie mentions that she would prefer a flat sail here.  To me, that depends on how and where one intends to use the boat. If one will be working a lot in light winds and old sea swell, the flat sail will be a lot quieter than a cambered-panel sail. The downside is that this smallish and flat sail will struggle with moving that heavy vessel in anything below wind force 5.

    If that Fisher 30 were mine, I would add quite some camber, at least 10%. This sail would outclass the flat one in the close- to broad reach zone (about 160-180 of the 360° circle). I am not talking about racing: I am talking about saving fuel and engine hours. The price to pay with the baggy panels is, as said, the noise if the vessel is rolling in light winds. In those conditions, I would just lower the sail.

    The shown sail is actually a slightly scaled-up version of a sail in use.


    ..and here is the original 35sqm sail at work on Ketil Greve's boat...

    Last modified: 25 Sep 2022 11:51 | Anonymous member (Administrator)
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