Palindrox
Chris,
im not finding the pictures i have of my boat, but here’s pretty much what it had. i still have the rig.
http://www.duckflatwoodenboats.com/mainpages/gallery.php?KID=52
i need to get out with the gps and get some polars, especially after i get the rig fully tuned. it felt like i was tazking inside of 100 degrees though, and that was first few times out.
the old rig IS pretty close winded. never had the gps on it though. it’s one of my projects for the summer. ive got the GPS countour now, so there’ll be video with gps track on the web one of these days.
tom
All of the excellent design discussion lately got me interested in revisiting my Palindrox design.
The basic idea is the same; a cambered junk powered proa with the drive-from-inside-philosophy of a paradox. But this time with some more refinements and rethinking.
First off, it has an unstayed mast. There’s something about having an unstayed mast in a pacific proa that just bugs me. Proas wants to be tensegrity structures—and it makes such a lovely one. But with the junk rig, you don’t have the option to rig it fractionally. So the mast gets really tall if the stays are going to clear the top of the sail. That’s what my last Palindrox had—a really tall mast! And the longer that spar is, the more it needs to get stiffened up. You can’t put diamond wires on a junk rig. So maybe the unstayed mast is a good idea. I like the added simplicity. And it bending off in puffs might not be the end of the world. I’ve sailed a Wyliecat 30, and the tip of that mast moves A LOT! Its supposed to.
My new mast is 40” shorter. It still sits to windward, sandwiched between two beefy bulkheads that form the central structure of the boat. They get all spindly and truss like inside the pod to save weight. The carbon mast is 7” in diameter where it goes through the boat, and tapers down to about 4”.
I stretched the boat 2 feet to 26 feet. That’s still a lot less boat than Madness, but hopefully enough that the cabin is not too much of an eyesore. LWL:BWL is about 12:1. But she doesn’t look unduly lean.
Inside there will be little sling chairs that clip to the hull and accommodate two seating heights. A low one for hanging out inside—where two people can sit facing each other with a little table in between. And a high one that pops your head a few inches out of the hatch for driving. You drive with your steering arm “out the window” to windward. You can also drive from the cockpit if you’re feeling randy. I’m not sure about hatches yet. Maybe fabric ones that zip open and closed?
Let me know what you think.
Best,
Chris
Here are some more renders.
This cut away on the midline gives some idea about the accommodations.
Stop me before I render again…
In the last version, the hatches were only 26” wide, and i’d like for them to be about 30”. So I stretched the whole house out by a foot, and moved the akas apart by the same distance. Remember I’ve added two feet to length, so I feel like I can get away with it. I spent 4” on the hatch, and 2” on getting the windshield at a shallower angle.
Here is a comparison of the last Palindrox and the latest one. The pod moved down a couple of inches and it does make the greenhouse a little airier.
more refinements, and 240 sq feet of sail—10% more.
Wow, she is looking really cool! Superb rendering, is this Sketchup? (I have dabled, but am much of a virgin with any thing not AutoCAD in these matters.)
My similar thoughts due to be published when I find that spare moment: Being form the cold north, my version has minimal openings, opening only to the top - I could see a lot of spray getting below at any speed. Keeeping the cabin dry is the bane of an boat up north, and the smaller the more dificult.
Cheers
Mark
Thanks. Mark! These were done in solidworks and rendered in photoview 360.
If you choose a junk rig as a given, then it makes sense to stick with the unstayed mast in order to gain all the coolness the junk has to give. The minute you ad stays, you lose a lot. That being said, the proa is a natural tensegrity structure (as you point out) and you have to ask, why keep the junk? Why not an ordinary beach cat rig that will be more efficient and less expensive, both in materials and R&D?
I’m just playing the devil’s advocate here, because this is the kind of feed back loop I personally get into and it drives me nuts. Now you’re up to 26’ - the same size as Rozinante!
I know I’m in the minority on the pod, but I think it’s overkill here. You are doing day trips and not sailing across oceans short-handed - do you really need it? Or in other words, WWBD? Please hold, channeling…. Bolger would allow just enough buoyancy to lee to make sure the boat will self-right from a 90 degree capsize, so that if push came to shove, the little craft would always self-right. The pod is great if it can serve a useful dual purpose (such as a bunk) but in this case I see it as a lot of trouble for little gain, and you’d always be tempted to store stuff in there, in the worst place it could possibly be from a self-righting aspect.
I love junks:
- Quick to reef = safety + always having the optimum sail area.
- Can be readily feathered.
- Good balance, so no need for the hassle of a jib.
- Can use simple to cut and cheap to buy sail cloth.
- A couple of stays to the windward ends of the beams does not get in the way of the sail.
- Can be made with good aerodynamic shape.
Mark
Michael:
Its true, the boat has been growing! Its a terrible cycle, but I needed to lengthen the house to get the hatches wide enough fore and aft to be comfortable. The previous (red) stayed version had part of the hatch overlapping the mast. Maybe this is a sign that the unstayed junk with the paradox inside steering can’t scale down to 24’.
I hear you about the pod. But I don’t want to ever get over 90 degrees! To me, the magic of the pod, as Sven explained, is that it puts the boat back on its feet while there is still some righting moment in the ama. I’m not crossing oceans, but if you’ve been out on the bay when its blowing 30+, it is no place to be knocked over in a proa! But you can definitely make the argument that the pod can go
Mark:
I’m attracted to the simplicity of the junk too. James Brett’s successful experiments do seem to show promise. I still don’t know how close winded it is compared to Russell’s rig, which by all accounts is pretty spectacular.
But if you take a look at the comparson of the red boat and the purple boat, you’ll see the extra mast height required to get the stays to clear the sail. Its a lot!
Thanks for your thoughts, guys!
chris
I am working on a sort of dyna rig that is actually just a symmetrical junk rig.You might be able to get it to work. Attached are a few plan form views which illustrate the concept. The sail could just as easily be made to go all around the yard and make a Clark y section soft wing sail. There would be extra weight and the luff parrel purchase would require some kind of mechanical advantage to ensure enough luff tension to maintain the leading edge shape between yards. To shunt one would only have to head up rather than fall off ,release the luff parrel , and then haul in the other, At least thats the idea.
I want to build two identical 1/12 scale proas and put a cambered junk on one, and a sloop on the other. If the junk is even in the running, especially to windward, then I’ll use the models to compare different sail cuts.
From a thread on the JRA page on racing junk-rigged boats:
I figured out that the junkrig of Marie G has a 9.3% handicap when going to windward, and a 4.2% handicap against a spinnaker-sailed boat running. Sailing without spinnaker gives Marie G an advantage of 4-5%, and in a reach even more. I find these numbers very interesting, and they support my vision that 90% of cruisers should be better off with a junkrig, period. It is now a long time to the next race, 2nd of December. That leaves me enough time to wonder whether a split junk rig would perform better…”
Summing up the season I would like to say that junk rig is highly adaptable to high performance yachts. I had doubts about converting my X-99, but I now have a very sail-able boat under me. She is so beautifully balanced, soothing, manoeuvrable, and whispering fast. Sailing her is truly rewarding.
Marie G carries a “quilted” junk sail, with camber sewn into each panel.
But if you take a look at the comparson of the red boat and the purple boat, you’ll see the extra mast height required to get the stays to clear the sail. Its a lot!
You drew the yard as being horizontal. If you incline the yard, there might not be any extra at all, while the peak of the sail could even be higher than the mast top.
Why do you draw the hatches as opening to windward? I expect the boat would be drier if they opened to lee.
Regards
Robert Biegler
http://www.junkrigassociation.org/Resources/Documents/Slieve’s Files/AYRS Catalyst 37.pdf
Sice reading this I’m even more enthuse about a junk. looks like the CE is VERY close to the mast meaning very little balance change as the rig rotates.
I need to find shop space and some time….
Tom