Hello from Florida with a Carter 35 lifting keel. Is this a good idea?

  • 01 Oct 2018 17:04
    Reply # 6700948 on 6700744
    Anonymous wrote:

    Andrew, one possible quick method is to use chapter 3 and 4 of 'The cambered Panel Junk Rig, to find a suitable sail design for your boat. From the range of master sailplans it should be possible to take one and expand it for your needs.

    Arne

    Thanks Arne, I was looking at some of the examples given. I suppose I am being a little nervous as I am assuming the sail and mast are a little bit more critical in position and size due to being a single instead of multiple sailplan.

     I'm going to come up with a rough plan this week and see what you guy's think. 

    It really is a good feeling knowing that there are people with real experience to ask. 

    Regards Andy 

  • 01 Oct 2018 15:23
    Reply # 6700744 on 6690867
    Anonymous member (Administrator)

    Andrew, one possible quick method is to use chapter 3 and 4 of 'The cambered Panel Junk Rig, to find a suitable sail design for your boat. From the range of master sailplans it should be possible to take one and expand it for your needs.

    Arne

  • 01 Oct 2018 01:17
    Reply # 6699960 on 6690867

    There really should be a 4th drawback to the junk rig... MATH  and then you want to throw electrical MATH at me!!!!!!!!... . I left school a loooong time ago.

    Sigh........

    Thanks for the idea it certainly seems to solve the problem very simply.

    I'm shooting for around 550sq ft which just by eyeballing it for now seems to be the largest reasonable size...Going to do some real numbers and drawing this week. 

    Regards Andy 

  • 29 Sep 2018 11:18
    Reply # 6698007 on 6690867
    Anonymous member (Administrator)

    Enter the electric halyard winch...

    There is one factor, which I think has pushed the size limit for a single sail upwards, and that is the electric capstan. These need not be of the hi-range electric genoa-winches, but can be simpler electric capstans meant for hauling up the anchor. They are surprisingly affordable, and surely much cheaper than splitting the sail area into two sails.

    The biggest single-sail JR I know about is the 80sqm rig of Peregrine (JRA NL 48). They added an electric winch after 2-3 years, and just kept the manual winch as back-up.

    I bought an electric winch handle for my 48sqm sail of my Johanna, after 8 years ‘in manual’, and I now frequently use that handle on the 35sqm sail of my Ingeborg.

    I find that the energy consumption needed to raise the sail is quite low, so will not drain a battery. The internal battery in my Winchrite appears to last ‘for ever’. I just topped up the battery once this summer, just to be on the safe side.

    A little theory:
    The energy needed to hoist 50kg 10 m up is...

    E = force [N] x distance[m] = (50 x 9.81)[N] x 10[m]
    = 4905Joule = 4905Ws

    If we assume that we lose 50% in friction, the energy needed is roughly 10.000Ws

    If that winch is to bring that weight up within 100seconds, the motors’s power must be

    P = 10000Ws : 100s = 100 W

    In a 12Volt system , the current flowing through the winch motor would be

    Current = 100W : 12V = 8.33A

    The current consumption is the current x time
    = 8.33A x 100s = 833As

    Since our 12V batteries are rated in Amp-hours, the current consumption needed to raise 50 kg 10 metres (with 50% loss) is.

    Current consumption[Ah] = 833[As] : 3600 = 0.23Ah
    ( = 0.23 x 12 = 2.8Wh).

    That is a little less than it takes to have a 3W lightbulb on for one hour.

    Conclusion: Electric halyard winches are definitely not ‘battery hogs’.

    Arne


    Last modified: 29 Sep 2018 18:31 | Anonymous member (Administrator)
  • 28 Sep 2018 09:06
    Reply # 6696468 on 6690867

    I'd forgotten - the final passages that I made in Tystie, from Canada to New Zealand, were made with the moderately high AR sail that I salvaged from the failed attempt to make a wingsail. The batten length was 5.15m and the luff length was nearly 10m. The mast finally ended up at 14.5m/47.5ft, after extending it, so there's not much excess length to be trimmed off a 50ft flagpole. This turned out to be quite manageable, but one of the reasons that I finally converted back to ketch rig in NZ was that it was a bit too far forward in the boat, so there was a tendency towards lee helm. The general concept was OK, though, and the experience lead me towards the shape of my current sail. I wouldn't want to scale it up to 550 - 600 sq ft directly, as there are only five sheeted points, but with the addition of one or two more battens, I think it would suit Bohemia.

    Last modified: 28 Sep 2018 18:56 | Anonymous member
  • 28 Sep 2018 00:46
    Reply # 6696051 on 6690867

    Thanks for the information, your real life experiences really help give some insight you just cannot get out of a book. Thanks for the link , it looks like a few people have used them for mast's so that solves one of my biggest issues.

    So we are going to do this!!! there is about another month of removing the interior and deck preparation which will now be easier as I will not have to work on chain plate's and during that time I will get going to get busy designing the sail. 

    I think as you said a single sail is the only way to go with the boat we have and I am going to try to design a high A/R rig around 550 to 600sq ft. and mitigate some of the issues you described by using spectra/dyneema with low friction blocks. We were going to go with Colligo Marine's Dux standing rigging if we had stayed (no pun intended) with our pointy rig and have done quite a bit of research on synthetics so hopefully that will pay off here. That said I have no desire to stray to far from what has worked in the past.

    Thanks for your input and I suppose the next post's will be over in the technical forum.

    Regards Andy

  • 26 Sep 2018 08:01
    Reply # 6693279 on 6690867

    14,000 lbs fully laden seems much more realistic.

    For the mast for a high AR rig, I'd be looking for a flagpole or lighting pole with a butt diameter of 10in and a wall thickness of .25in or more - something like this.

    My experience with sails of this size was with lower AR sails. This meant that the battens were 22.5ft long, and necessarily of heavier section than for a 17ft batten. Weight to be hoisted becomes an issue, and my best solution was a 3:1 halyard combined with a 2 speed self tailing winch, 14:1 and 30:1 power ratios. I also used the same size of winch for the sheet, as loads were quite high, but for both halyard and sheet, the 30:1 ratio only came into play occasionally; the 14:1 ratio was enough for much of the time. Other than that, I found that the load in the YHP was high, with a high-peaked yard, and I was close to adding another little winch to make the final tensioning easier. The lower peak of my current sail decreases the loadings on the YHP and LHP, when compared with a high peaked yard, and this is the way that I would recommend going on any maximum size sail.

  • 26 Sep 2018 01:56
    Reply # 6692966 on 6690867

    Hi David,

    Yes she is a light boat around 10500 empty on the travel lift scale and 14000 or so ready to go. The interior is ply and fully glassed to the hull so we are being careful with how it is changed, the hull deck joint is also joined with glass and is totally watertight and strong.  I was figuring around 550 to 600 sq ft as the gulf coast generally has lighter winds and as you said at 2 to 1 aspect ratio a 17 by 35 would give me about 550 sq ft I was trying to figure out if I could get 600 sq ft but now the mast length is getting a little bit long. I suppose one of the bigger questions is aluminum or wood for the spar at this size.

    We were planning on converting the v berth into a work area so having the spar in the middle of it would not be to troublesome, I would build up a laminated ring frame which would be tied into the new interior so there would be plenty of support. This is a stiff hull with no creaking or funny noises even when pushing into wind and waves.

    Reading practical junk rig seems to suggest a practical limit around 500 sq ft so I am wondering what considerations need to be given with a sail this size.

    Regards Andy.  

  • 25 Sep 2018 08:11
    Reply # 6691263 on 6690867

    Hello Andy,

    Well, it's going to have to be a single mast, as the after mast of a ketch or schooner is going to be fighting for space with the keelbox, companionway and engine.

    Sailboatdata gives the displacement as 9300 lbs - can that be correct? It seems very light for a 35ft boat.

    The current rig is pretty lofty, so a moderately high AR junk rig of about 500 - 550 sq ft seems reasonable. That would give a batten length of about 17ft - again, reasonable. 

    So yes - a good idea, enabling you to move away from the pointy-top rig!!

  • 25 Sep 2018 01:48
    Message # 6690867

    Hello we are Andy and Monica and live in Sebring Florida, yes about as far away from the Atlantic or Gulf as you can get in Florida.

    We have owned "Bohemia" a Carter 35 Offshore built at Northshore Shipyard, Chichester UK.  for about two and a half years and recently hauled her and brought her to the house for a total refit. All of the mechanical s are in good working order but we do plan on changing the interior layout quite considerably. 

    I cannot remember how many years ago that I read  Annie's book 'Voyaging on a Small Income' but it has always been my inspiration to do this and the recent article in Good old boat was just another little poke in the ribs, and then reading many of the the threads on JRA just pushed us over the edge!

    So! now to the nitty gritty.... I think this will be good, the hull is slightly tender but stiffens up nicely with a 45% bal/disp ratio is easily driven and tracks quite well as the transom hung rudder and a deep forefoot really help with directional stability, she can still get to windward even with the keel three quarter raised.  I would really prefer to stay with a single sail for efficiency and simplicity and I am not to worried about weight aloft and can accommodate the structural needs with the interior reconstruction.  We were planning on redoing all the standing and running rigging as well as adding a code zero so Just using ballpark figures the cost of a new spar and one sail will probably come out about the same or maybe even slightly less.

    Thank you for all the effort put into JRA by everyone that contributes it really boggles the mind that the junk rig is not more popular.

    Regards Andy.


     

       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

                                                              Site contents © the Junk Rig Association and/or individual authors

Powered by Wild Apricot Membership Software