<<One primary consideration of this design is that I be able to put it into a container. >>

  Yes, that's my assumption about what you're shooting for.  I like the cutout in the leeward hull to allow a wider cockpit.  It's a neat design.


<<The telescoping masts sound interesting, but I don't think any have yet been built, so I am hesitant to make a decision going that way>>

  That makes sense.  But two-part masts would be much less of a leap, and would be easy to engineer.  The only real limitation would be either finding a way to mate up the sail track, or alternately, going with a pocket luff.


<<. What about a dual ballestron rig, instead of dual mainsail only>>

  You'd likely have turbulence from the forward sails messing with flow over the aft sails.  The schooner una can work, but adding jibs could cause you to spend a lot of time pulling strings to get your sails set just right.


<<Can you be more specific on why you think I need to up the budget? >>

  Darn good question! 

  Basically, it's rare that a new design comes in under budget.  The factory in China may be able to build a Raps boat for $30,000, but that figure probably assumes that the boat is not a one-off design.  If yours is the only one of its kind, or the first one of its kind without any guarantee of additional boats, the cost will likely rise. It's better to overestimate, and then save the surplus (if it exists) than to do the opposite.

  My comment, though, was specifically aimed at beating the Maine Cat in light winds while carrying 2000 pounds, and without the benefit of a huge spinnaker.  If you're going to do things like move to telescopic masts and/or beams, lengthen the boat, add more beam, or more sails, that drives up the price.  You might not choose to do any of that, of course.

  Another option is a huge Outleader kite if you're broad reaching or going downwind.  That could add a serious amount of speed.

  But that's just one opinion.


<<For me, it seems to come down to the sail area and the righting moment determining the performance>>

  As well as the waterline length and wetted surface area. 

  You're already doing quite well on the waterline length, so the question is how you want to carry the extra weight.


<<To be honest, the cost is the truely exciting thing here for me. It means that I might actually be able to go from dreaming to sailing. >>

  Like I said, you've got a neat boat planned.  It already does the impossible (trailerable, containerable, cruisable, slip-able, seaworthy, fast, and less than $50,000), and it will probably outsail the Maine Cat most of the time.  The only question is what it would take to make it outsail the cat *all* the time.  I don't think you'd be crying much in that boat, regardless of what you to to improve performance.

       - Mike

 

Gardner Pomper wrote:

Hi,

Thanks for the reply. I should have referenced the other thread I started giving the drawings for the boat. They are in the files section of this group under "Gardner's Layouts".

One primary consideration of this design is that I be able to put it into a container. So, it will collapse to 12' for a slip, and to 7.5' for a container, with no more disassembly that sliding the crossbeams out.

From the calculations I ahve done (included on the front drawing), a 2' waterline beam on each hull should give me a design displacement of 4800 pounds, so I think I am within the design characteristics for the displacement. As for the weight, I have to admit that I am going on some calculations from otehr designs and from the figures from the harryproa site. I am also amazed by how light it is supposed to be.

The telescoping masts sound interesting, but I don't think any have yet been built, so I am hesitant to make a decision going that way. What about a dual ballestron rig, instead of dual mainsail only? Each of the schooner rigs I have seen in the harryproa designs leave off the jib, and I am unclear why that is.

Can you be more specific on why you think I need to up the budget? I am not disagreeing, I just want to hear the reasoning. It strikes me that it could be because my estimate boat weight is too light, but those calc seem to work. It could also be that my hulls are too fat, but I am running at a 20:1 length to beam ratio on the lw hull. In terms of increasing the hull length, I am already 10' longer than the maine cat and end up with 2500 lbs less weight, so I am not sure about that.

For me, it seems to come down to the sail area and the righting moment determining the performance, but I really am looking to learn something from the rest of the people in the group, so please come ahead with comments.

To be honest, the cost is the truely exciting thing here for me. It means that I might actually be able to go from dreaming to sailing. If it really will take an extra 50% to up the performance, then I will just sail slower and cry a little.

Thanks so much for the feedback. It is always helpful.

- Gardner

On Tue, Dec 9, 2008 at 1:42 PM, Mike Crawford <jmichael@gwi.net> wrote:

  That's a pretty big challenge.  Carry the same load as a boat that's twice as heavy, at one quarter the price, and still go faster.  Complicating this further is that you probably want to keep the feature where you can collapse down to a 12' beam for a slip (the Maine Cat 30 now has an 18' beam), and also be trailerable.

  It shouldn't be to hard to beat the Maine Cat when you're daysailing.  Your proa will have a nice weight advantage, as well as the flexible masts that will let you handle a wider wind range without reefing.

  Part of the problem is that you're increasing the boat's displacement by 50%.  That's a pretty substantial increase for a multihull.  It's hard for a 2000 boat to carry the same 2000 load at the same speed as a 4000 pound boat.

  You can probably do it, but not without giving up something, either your 12' slip beam or your 25% cost.

  I'd look at four things:

  - Telescoping or two-part masts for more sail area.

  - Telescoping or scissoring beams to give you a wider beam on the water while still allowing slip width.

  - Going up another ten feet in length.  This is really important for carrying loads on a light boat.

  There was some talk a while back about designing ends for the leeward hull that could slide on and off, or flip up, for transport.  But no one has yet had a reason to actually try to build such a craft.

  In any case, I'd estimate another $25,000 to beat that Maine Cat while carrying a full 2000 pound cruising load, bringing you up to 40% of its cost, and giving you a wicked fast racing machine when you're not loading down.  With some extra length, beam, and sail area, you should be able to carry that load much more gracefully.
 

       - Mike

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