David Thatcher's New Boat

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  • 12 Nov 2018 06:41
    Reply # 6899947 on 6876461
    Hey, David, it looks like you are making fantastic progress and you seem to have limitless energy.  Send some my way, will you?

    Good to hear that you are going to get some nice sailing with Footprints, too.  You sound to have a busy summer ahead of you :-D

  • 11 Nov 2018 07:05
    Reply # 6899025 on 6876461

    Slow but steady progress over the past two weekends. Last weekend I faired the framing ready for the plywood. There was a lot of material to come off the keel , especially in the forward parts of each hull. An electric plane was used to remove the bulk of the wood, but followed up with a good old Jack plane for final finishing. And of course the 4 inch angle grinder with coarse pad helped out a lot.

    This weekend I glued on two plywood panels. These are probably the biggest single gluing job in the whole construction - not helped by the fact I am using fast hardener in summer temperatures! I need to go shopping for more resin, and plywood. There is probably about 3 hours work in each hull panel. Measuring, cutting, sanding the inside surface, 2 coats of epoxy sealer, which then needs to be sanded down. Then the final gluing onto the frame operation.

    There will probably not be a lot of progress over the next couple of weeks as I am hauling 'Footprints' next Friday for a week of maintenance which includes removal of very old anti-fouling. Hopefully a week of full time work will see her back in the water the following week. Then back into boat building, but with at least one day of sailing fitted into each weekend. 

    Last modified: 11 Nov 2018 07:10 | Anonymous member
  • 01 Nov 2018 13:30
    Reply # 6883991 on 6876461

    Love the Wharram soft-wing,  though not sure if the battens are wise - they will snag on the stays if you let the sail go,  without battens only the gaff snags.  For a catamaran, I would go with a free standing mast for the ability to fully release the sail in a gust 

    Last modified: 01 Nov 2018 13:31 | Anonymous member
  • 01 Nov 2018 07:51
    Reply # 6883561 on 6883504
    David wrote:
    Having finished the boat he decided there was no reason why he could not build his own sails. So he made some very nice radial cut, full length batten soft wing sails. I sailed on the boat a few times and I seem to recall it went well to windward, despite the long shallow Wharram type skeg. I like the idea of this type of rig because it is low tech, and I could do a lot of it myself. food for thought. 
    I've not seen it done like this before, with full battens and two very deep reefs. It looks like a very appropriate solution for a small catamaran.
  • 01 Nov 2018 06:59
    Reply # 6883507 on 6883265
    Graham Cox wrote:

    PS:  I just bought the study plans for the Eco 7.5.  Need something a little bigger than the 6 for me to live on.  May never get to build it of course, but if someone offers me 10K for Arion (fully equipped down to the JSD)  I will have to look for a barn to rent!  I'll choose the gunter/gaff rig with the head of the sail in a sleeve for sure.  It may not be junky (and I love my junk rig) but it sure is funky!  If I do build it, it will be a "quick and dirty" build.  I'm too old, and have always been too impatient, to spend several years in the shed.

    Thanks for your comments. The 7.5 would have been a better boat for us size wise, but I would have never been able to get the 4.5 meter beam down our driveway. But the 6 meter length is a much more realistic size for someone building part time. I imagine the 7.5 meter would be at least half as much boat again to build. I am not building 'quick and dirty', but more'quick and appropriate'. The boat will not be a piece of polished furniture, but it will be well built, strong, and with an appropriate finish. I am finishing everything as I go to the sanded and epoxy sealed stage. This will save a lot of finishing time later on. There is an Eco 6 being built up in Cairns and I imagine the boat will be well suited to tropical coastal cruising.

    I chose the porch build location as it is the most level floor for setting up the hulls. When I begin assembling the boat I will need to move it into our big utility shed. The current location provides me with a lot of exercise because it is about 20 meters from my workshop, and on building days I am constantly going back and forth. In fact it seems that by the end of a building day a large percentage of my tools have relocated from the workshop to the boat, and then they all need to be put away again. I must have walked many kilometers already!

  • 01 Nov 2018 06:39
    Reply # 6883504 on 6882176
    David Tyler wrote:

    Have you considered the Wharram pattern of wing sail, with a wrap around sail and a short gaff, plus a furling headsail? Designed for catamarans, after all's said and done. I wouldn't enjoy reefing it, but otherwise, I think I'd favour it over the gunter or flat-top bermudan.

    I have been thinking about the Wharram type wing sail as a possible alternative. A few years ago a friend did a very nice job of building a Tki 38 Wharram with the schooner rig. He modified the design quite a lot and did some offshore sailing on the boat. Having finished the boat he decided there was no reason why he could not build his own sails. So he made some very nice radial cut, full length and also shorter batten soft wing sails. I sailed on the boat a few times and I seem to recall it went well to windward, despite the long shallow Wharram type skeg. I like the idea of this type of rig because it is low tech, and I could do a lot of it myself. food for thought. 
    Last modified: 01 Nov 2018 19:59 | Anonymous member
  • 31 Oct 2018 23:14
    Reply # 6883265 on 6876461

    PS:  I just bought the study plans for the Eco 7.5.  Need something a little bigger than the 6 for me to live on.  May never get to build it of course, but if someone offers me 10K for Arion (fully equipped down to the JSD)  I will have to look for a barn to rent!  I'll choose the gunter/gaff rig with the head of the sail in a sleeve for sure.  It may not be junky (and I love my junk rig) but it sure is funky!  If I do build it, it will be a "quick and dirty" build.  I'm too old, and have always been too impatient, to spend several years in the shed.

  • 31 Oct 2018 22:52
    Reply # 6883243 on 6876461

    Hi David.  I love your new cat project.  Funky design and for me the gunter rig looks fabulous, the perfect rig for this small light cat.  When the main is deeply reefed or furled, it becomes a very snug rig.  I have not yet been able to sell Arion (zero interest this side of the Tasman) but if I ever do, a small cat would be ideal for cruising the QLD coast.  I also love that you are building both hulls on your back porch!  Yesterday I was on a friend's Tennant designed Great Barrier Express catamaran, the so called Sports version, which is actually more of a cruiser, with a central cuddy and a double bunk in each hull.  There are quite a few of them in QLD, but outside my price range at 60-80K.  I've said many times there will be no more big boat projects for me, but a small, simple Kohler cat could tempt me.  I'll be watching your project with keen interest. 

  • 31 Oct 2018 10:23
    Reply # 6882176 on 6876461

    Clearly, a single mast needs to be well aft, or a pair of biplane masts need to be very low and light if well forward, with more latitude if they are further aft. All in all, it seems easiest to keep the stayed mast where it is designed to be. 

    Have you considered the Wharram pattern of wing sail, with a wrap around sail and a short gaff, plus a furling headsail? Designed for catamarans, after all's said and done. I wouldn't enjoy reefing it, but otherwise, I think I'd favour it over the gunter or flat-top bermudan.

  • 31 Oct 2018 04:49
    Reply # 6882005 on 6876461

    Good to see all the interest and comments about my new catamaran, and I have had some direct contact about this as well, thank you all. We can always be sure of some good robust discussion and comment on the JRA forum.

    I thought I should explain a little more the difficulties, or stumbling blocks, to fitting a junk rig. If I were to fit a junk rig to the boat it should be an improvement on the designed rig, be safe, be practical, and enhance the boat in looks, performance, and ease of handling.

    Leeway Resistance The mast is placed in its current position above a reinforced bulkhead which also helps to divide up the accommodation space. The current, (single) dagger-board will be placed in its current position for reason of CLR, and the CE of the rig. I suspect the real reason it is raked forward as it is will be to allow the dagger-board case to exit through the sloping aft cabin bulkhead which allows for raising and lowering of the board from the cockpit. It is also possible to fit asymmetric lee-boards to the boat, these are mounted on the inside of the hulls under the bridge deck. Theoretically these could easily be moved forward to move the CLR forward. But there are some down sides to these lee-boards which include a lot of structure to support them which means more weight. There will be a lifting and lowering mechanism of some sort, and when sailing only one board should be down at a time. So, not as simple as the dagger-board.

    It would also be possible to fit mini keels as is done on many cruising catamarans, and I have thought about this quite a lot because this would also allow for moving the CLR forward. But disadvantages are increased draft, extra weight, and mini keels on a catamaran can induce, or amplify the pitching motion which multihulls can be prone to because of all the extra buoyancy the mini keels introduce in the middle of the boat. Mini keels also reduce windward performance, and rob boat speed compared to a boat fitted with a good dagger-board, So once again the dagger-board is a better solution.

    Mast Position When first thinking about a junk rig placing the mast further forward adjacent to bulkhead 2 seemed to obvious thing to do. But then when I studied the plans a lot more, and now I can see the hull shapes in 3D I realise that there is not a lot of load carrying ability in the forward sections of the hulls, they are very fine, which is no bad thing for this design. But that means that the load carrying portion of the hulls is from midships aft, which will also be a reason why the current rig is placed where it is. So placing a junk rig forward on the boat will put a lot of weight where it should not be.

    Junk Rig Options I have had a couple of good suggestions regarding use of a split rig which which could solve the CE problem. But with one of these rigs, or a single junk sail of 20 square meters we end up with a lot of sail area up high, because of the quadrilateral sail shape. I am not so sure that a lot of sail area up high is that healthy on a potentially quite tippy coastal catamaran. Paul MaKay's Aero Junk rig would just about fit as a single mast rig, and I have not discounted this. But the wishbone battens add quite a level of complexity, and would this be more simple and easy to handle than the designed rig? I am thinking about an Aero Junk bi-plane rig with a mast in each hull in about the same fore and aft position of the current rig, or may be a little further forward. This could be made to work with each sail about 10 square meters. This would potentially allow the CE of the rig to be far enough forward and the masts may not interfere too much with the accommodation.  I would also want the rig to look good. So I am playing with this idea a little bit.

    Anyway the above has been my thought process. It is all a lot of fun and it is great to have such a project to get involved in and work ideas around.

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