How did the GIS do up wind?  I don’t doubt that they fly off the wind—with tons of sail area and very little weight.  But my concern is that in the interest of a simpler rig (no jib to switch in shunts, no expensive mast track hardware, etc.) I’ll kill the upwind goose.  Scampi is a cruising boat, but it would be embarrassing if she did not have a nice turn of speed on all points.

Then there’s the matter of aspect ratio.  There’s lots of chatter on the GIS forum about problems with Romilly’s rig—why does it seem to have more issues with the wrong tack, why does Nigel prefer not to have a boom (which the BJ 17 does have).  I’m not sure I’ve seen a lug sail that was designed for as quick a boat as Scampi (hopefully!).  That’s why I threw in the full length battens and relatively small sectioned carbon mast.

I’m also wondering about having the CE of the sail behind the midline.  On my land proa, when the CE was well behind the midpoint fore and aft, it would sit there like a log. As you canted the mast forward, it would SHOOT off.  I’m hoping that I can control the CLR with the front dagger rudder to the point where she’ll sail in balance—on Palindrome, the CLR was fixed very near the midline fore and aft (I think).  On land sailers, the CLR is related to the weight distribution on the tires.

On that same subject; in theory (always a bad way to start a sentence), the front dagger rudder should be enough to get the boat to balance.  But Russell and others like the daggerboard in the ama for upwind work.  What’s going on there?

Thanks to everyone for your thoughts and support on this project.  I’m feeling like I might have to build this one.

Chris

Hey Skip,

A few quick numbers to share.  Keep in mind that what I’ve drawn is more of a styling exercise—its all a look and some best guesses.

Having said that, sunk to her chine (about 10” of draft) she’ll displace about 1300 pounds.  At that displacement the wetted surface is 7840 square inches.

I expect (total speculation) Scampi to weigh about 500 lb dry, with a light cruising payload of about 600 pounds. At that displacement she’ll have about 7220 square inches of wetted surface.

Those numbers are not including foils.  Each foil, fully dropped has an area of about 900 square inches.

But those numbers are based on a cartoon, of course…

Best,
Chris

Here are some shots of the disembodied underwater volume of scampi.

At 1100 pounds load, the waterline length is 277 inches and the waterline beam is 25.  That’s almost exactly 11:1 LWL:BWL.  That sounds about right for a cruising proa, no?  She’s drawing 9” at that displacement.

Luomanen - 24 January 2013 01:16 PM

Hey Skip,

A few quick numbers to share.  Keep in mind that what I’ve drawn is more of a styling exercise—its all a look and some best guesses.

Having said that, sunk to her chine (about 10” of draft) she’ll displace about 1300 pounds.  At that displacement the wetted surface is 7840 square inches.

I expect (total speculation) Scampi to weigh about 500 lb dry, with a light cruising payload of about 600 pounds. At that displacement she’ll have about 7220 square inches of wetted surface.

Those numbers are not including foils.  Each foil, fully dropped has an area of about 900 square inches.

But those numbers are based on a cartoon, of course…

Best,
Chris

Hmm that’s about 57 sq ft with one foil down which works out to 4+ square feet of sail for every square foot of wetted surface, hell I might not like you that much in a light breeze 😉

FWIW P52 weighed no more than 400# dry but was built light and cheap.

Thanks for the update, this project looks really promising

Skip

On that same subject; in theory (always a bad way to start a sentence), the front dagger rudder should be enough to get the boat to balance.  But Russell and others like the daggerboard in the ama for upwind work.  What’s going on there?

Too bad you weren’t at Proa Night, Russ and Paul went into considerably detail about rudders, placement fore and aft, how much immersion to balance, etc. But I can’t tell you about it. 😉

Russell said his boat balanced to ww with full aft rudder, and about a third fwd rudder down (I think).
The new 32 will balance with aft rudder down, fwd rudder full up. The rudders are a bit more in the bows that Jzerro.

I hate to mention it but you could mount a beach cat rig at first, use it as a bench mark. This would be so cheap and work so well that you might not get around to the lug.

Chris,
I think your hull shapes look great and the beam to length ratio seems good too. I really like this boat!
I think our editor has a good point about the rig. I was thinking to mention the same thing. Three wires, not much weight, and lots of power. Also the ability to carry light air sails.
Russell

If you like a Lug, why not go the whole hog and have a Junk rig (lug).  A junk can be made with a sail that works equally on both tacks.  a lug will need a strong downhaul on the luff and allround higher rig loads to hold a good sail shape.  The junk battens hold the shape with minumal rig loads.  Of course much easier to reef a junk.  Down side, more complicated and heavy.  If you have the beauty of sailing with constant winds, the basic Lug may be best, in my real world, a multihull reefs half a doesn times on a day sail.

That said: Lovely design and fantastic graphics.

Mark (from Scotland)

Too bad you weren’t at Proa Night, Russ and Paul went into considerably detail about rudders, placement fore and aft, how much immersion to balance, etc.

Now that’s just cruel!

There are tons of reasons to have a beach cat type of rig. It being proven, not only on Russel’s boats, but basically everything fast that doesn’t have a wing yet, counts for a lot.  And I can imagine it might be hard to stomach the performance lug after trying the beach cat rig.

I guess there’s part of me that wants more extreme simplicity.  I’ve sailed a Wylie Cat 30—and was hugely impressed, both by how well it sailed and how pleasant one sheet sailing is. The lugs and the junks are attempts to bring that simplicity to a proa.  The beach cat rig adds two sheets and their hardware, two sails, two halyards, a boom vang, mast with a sail track, etc. 

What powerful, simple, one sheet rigs are out there?  Irens’ carbon lug and cambered junks help to get the CE forward, because they are balanced.  I’d love to try a laser or wylie-cat type rig—but then the CE moves pretty far aft.  What else fits the bill?  Some kind of stayed or unstayed aero-riggish thing?  A stayed mast with a junk/jib, like skip is playing with?  What else?

Having said that, there’s no arguing with Russell’s point.

Three wires, not much weight, and lots of power. Also the ability to carry light air sails

.

So I looked at a Hobie 16ish rig on Scampi—a mast and boom to match a 24’ luff and a 9” foot.  When I put the stays out to the ends of the boat, the mast is only 13.5 inches windward of the stay attachment points.  When we move the stays 4’ back from the bows, that goes up to over 25”, but now the boom has to be 2’ shorter, and there’s more interference between the stays and the main.

Then again, I could move the mast step further to windward by moving the house over some, but that might cause some problems with the look.

Thanks for your thoughts and encouragement.

Chris

Wonder if anyone recorded the proa night presentation?

A couple of thoughts about the Hobie rig:
- the stays to the bows, which are a smaller distance behind the mast might be OK, since the only time this is an issue is when caught aback with the sheets eased. In that case, it might be enough to have a running backstay to each corner of the leepod, as long as you remember to tighten one of the backstays.
- you could use a rigid forestay with a ‘shock absorber’ to provide both forestay tension and hold the mast up if caught aback.
- you could mount a rigid gaff at the top of the mast and a sprit to lee of the leepod and mount a backstay between them that would stay clear of the sail. But I’m not sure what would happen if you burried the sprit and leepod into a wave at speed. You’d need stays for the sprit, and that might be too many wires (and also extra width in the marina berth).

One of the things that has come out of working with Paul on the 32’ proa is that not as much staying angle is needed on the leeward side to keep the mast up as I had thought. If compared to a modern monohull the angles I have been using are pretty conservative.
I think the angles you are talking about would work, but I’d like to see an end view.
The boom should be able to sheet to centerline, but the leech of the main will contact the main up pretty high, and with the twist of the sail, you should be able to sheet as tight as you want.
The boat would probably balance okay under main alone. I wonder if it would make more sense to use a rig from a bigger beach cat and only use head sails in light air. A tornado mast is 31 feet (I think), but it’s pretty easy to step solo.
Russell

Hey Russell,

I really like the idea of being able to sail main only.  Playing with headsails sounds really fun in light air.  But if it can be made to balance well under just the main alone, that could be amazing for a short handed little cruiser.  We know una rigs work—to windward and otherwise!  I love that the sail handling could pretty much all be done from the cockpit.  Walking around on that little deck in snotty weather sounds scary to me.

So I drew this version.  The square headed una rig has a rotating mast and a wishbone boom.  I want the sail to be really close to the top of the house, so there’s little room for a vang.  This seems like a nice application for a wishbone boom.

I drew it at 200sq ft. on a 30’ mast.  That gives an 1100lb displacement Scampi 3:1 sail area to wetted area, and a bruce number of 1.37.  Plenty for a cruiser!  Its more than an F20 cat’s main.  I revised the lug rig to be 200 square feet for comparison.  Its not even that much taller (though the mast is).

Are there other drawbacks to having the CE that far back?  With the rotating beach cat main, the CE ends up being about 46” behind the mast centerline.  My lug is not that much better, with the CE about 36” behind the mast.

Is getting balance on all points with main alone just a matter of putting the boards in the right place, and trimming them correctly for the point of sail?  Or are there other issues sailing under main alone? 

Thanks for your feedback!

Best,
Chris

here are the three views with the wishbone, rotating una rig..

inspiration

I’ve been in love with that inspiration for years (: