I'm putting together a 10' beam Nacra 18 Sq Meter, and the traveller track is missing from my rear beam. This seemed a great opportunity to explore a curved track - so, what do I need, and can I buy it, or do I have to make it? Should it be to the radius of the boom length, or a bit tighter to induce twisting (or is it to continue to force rotation?) Or should I just get another straight track? I have a new Ogletree-drawn Ullman-cut squaretop with a 30' luff coming in a month or three, if that makes any difference. Anyway, any information is greatly appreciated.
I have seen the curved tracks on both harken’s site and on ronstan’s site. They both sell the cars that go on tracks as well as the end stops.
Matt
I know Harken will take your specs and create the track for you...but I recommend that you be sitting down when you get the quote!
Just make yourself a Drop Lever on your boom, it does the same thing as a Curved track and is considerably less expense. Plus, your knees will thank you later.
It will still let you have maximum travel on the mainsheet for downwind sailing and still keep the sheeting angle level and the main sheet vertical.
Would it be possible to get a description (preferably a picture) of such an arrangement?
BR
Patrik
I will try and draw one out later today and post a scan. I don't have a picture, but have seen it used mostly on 18sq's.
If anyone has a picture, post one.
Andrew,
I saw a number of 18 Squares in the late 80's that had curved travellers. These had a center of radius behind the mast, so the clew of the sail would be pulled toward the mast as you let out the traveller. This makes the sail fuller and more powerful. The ends of these travellers were higher than the center, inducing twist as the traveller is let out. These tracks were mounted to the top of the rear beam in the center and then a molded track support attached the ends of the track to the hulls. When properly designed, the mainsheet would be set at the start and then the traveller was the only adjustment made as the boat went upwind or downwind or anywhere inbetween. Nice for single-handed boats, however, the traveller is a bit of an obstacle when moving around the boat.
All the systems I saw were purchased from Harken.
P.S. - All the Nacra 18 Squares started as 11' beam. Why reduce it to 10'? I would have made mine 12' beam if I had to change it.
Hi Andrew,
why dincha write to either us or to Palin? Huh? Merry merry, incidentally...
I have a curved traveller, but I ain't givin' it up. Harken will make 'em for you. If you like, I can get measurements of the arc for ya, or other info about the track I've got.
For the drop lever boom, go to
http:/
This is Mike Coleman's site. Great resource for 18sq cats. Bookmark it, it's useful.
I met a fella at Birmingham recently. He had a Cat II sq rigged up with some interesting stuff, including a boom vang arrangement which is simpler than either the curved trav or the droplever boom.
Why aincha going to 31' mast while you at gettin' a new sail? Not that hard to add the foot to the head of the mast, and mine and Jay's are working out well. Fact, we prolly got some extra extrusion.
And, like the guy said, why 10' beam?
sea ya
tami
Without a jib, I don't think you want twist...
sea ya
tami
Here is picture of one at the back of the boom. The lower travel car on the boom moves freely. ![[Linked Image]](http://www.geocities.com/mec_coleman/my18square3.jpg)
Very cool idea. I wished I'd seen this before I got my curved travelor track installed.
Bill,
It was very popular with many of the 18sq's in the mid to late 80's as an Alt to the curved track. It sure beats having a track beat up your knees!! The 5.2 with the center bar was bad enough!!
CO
Is there any advantage to the curved (flat) track?
Assuming you have a horizontal boom and a free floating car on the boom?
A longer boom is the only penalty I can think of, and the weight of boom track and car.
Why aincha going to 31' mast while you at gettin' a new sail? Not that hard to add the foot to the head of the mast, and mine and Jay's are working out well. Fact, we prolly got some extra extrusion.
And, like the guy said, why 10' beam?
sea ya
tami
The mast is a Marstrom Tornado tapered extrusion, probably 1970s vintage, and measures right at 32'; the finished luff of the sail will be 30'.
Why 10'? I have the beams, and at just over 1/8 of a ton (260 lbs) dry weight, I've NEVER "needed" to trap upwind on my 11' Square. The 10' boat will lift a hull sooner, yet the squaretop will allow depowering (if/when it's needed). The drop lever traveler remains a viable option, tho the pics I've seen show it with a beam-mounted boom which angles up sharply. My boom is intended to be nearly horizontal, so I don't know how well it would work. More thoughts tomorrow, thanks y'all.
I used to think that too, till I started using leach telltales.
Eeew... I dunno... maybe you ought to have a conversation with Palin or Charlie about that. My rule of thumb about twist comes from Palin...
sea ya
tami
I'll wrack Charlie's brain as best I can, and probably interview Palin as well. Speaking of Palin, last I heard there was a very good chance that Jon Lindahl's personal LCD Square, pretty much identical to Palin's (or should that be vice versa?), was coming to Texas to stay.
...Bob Young was in process of purchasing the boat when he passed away.
Do please let me know what the boys have to say about twist in unirigs.
sea ya
tami
Hi Andrew,
The mast is a Marstrom Tornado tapered extrusion, probably 1970s vintage, and measures right at 32'; the finished luff of the sail will be 30'.
Great upgrade for a 18 sq.
This brings up some more questions:
Did you use the nacra or tornado rigging?
Or did you make up a complete new rigging?
Did you change anything on the tornado mast foot / nylon mast ball on beam?
Geert Lindemulder
nacra 18 sq sail # 306
New shrouds, Nacra-style (loooong) forestay bridle. I don't think the eggshell hulls would be happy with the stress of a short forestay bridle!
I don't know if it's original, but the half-socket on the mast base fits over the ball fine. It's not captive, but I'm tying off the mast base to the dolphin striker (JUST loosely enough) and haven't had a problem yet.
What's your hull number, out of curiosity? I have two sets; #189 and #12. The new sail and tall rig are going to go with #12. Where are you located, too?
The hull numbers are hidden by anti-slip material. According to the paperwork it is TRRE0115M81G. I bought it three years ago. The hulls are the old eggshell type. And yes i'am afraid to break it some day.
The boat was put together out of a lot of different nacra
18 sq parts the nacra dealer had lying around at that time. The mast and sail are from a 1995 18sq. I am running out of proper sails; an upgrade to tornado mast to be able to fit "standard" sails seems a nice way to go.
My sail location is the "randmeren" at the Netherlands.
What do you mean with "It's not captive,but I'm tying off the mast base to the dolphin striker (JUST loosely enough)"?
Did you sail with this mast with another sail yet?
Was the drop level boom ever used on other type cats? I only know it from Mike Colemans site, being used at 18sq.
Geert Lindemulder
nacra 18 sq sail # 306
Thanks! As for "proper" sails, I don't know, but my sail is being made new for me. I had contemplated trying to fit a Nacra 20 main, which is nominally 18 sq metres in area.
I have not sailed yet with this mast. However, my old Nacra 5.O had the non-captive early Nacra mast base system, with the open hemisphere and the small ball. For safety I'd always tie a short line from the mast base to the striker while stepping the mast. This T mast has a similar step, and likewise, I tied a small line to it to keep it from falling completely free if it slips off the step ball while it's being stepped. It has worked fine while rigging it, but I haven't sailed with this mast yet.
The scuttle is that Rennie in Port Arthur is seriously interested in the boat. Good news for you 18sq nuts as he gets out to quite a few regattas.
Chris.
Yes, Rennie and I talked about it quite a bit while we were tearing down our boats at Turkey Day - well, he was just TYING his down, but yeah... Tilt trailers are in the works both for my soon-to-be-yellow boat, and for soon-to-be-his yellow boat. Ian, Jon's son, had mentioned that he'd pitchpoled his dad's boat pretty violently over the summer, and had to redo the starboard hull, which is now about 4 lbs heavier than previously. He took advantage of the moment to repaint the previously-orange boat, too.
I have the drop lever boom on my boat and it works quite well! My question to all you sq.owners is could the size of the boom be reduced to save some weight. Mine looks to be a Prindle 19 section or a 5.2 section. i have seen many of the new cats,(some with much more sail area) using very small booms. With the drop lever I don't think we put that much for & aft stress on the tube. Hope you all chime in.This has been a good 18 sq discussion. (Very far and few between)
Ed
Nacra 18 SQ
If I understand how the drop lever works, then actualy while it puts little compressive force on the boom, it puts a lot of bending. The sail is secured fore or aft of the car the mainsheet block secures to, so the bending is produced by the offset between the two multiplied by the tension (acting perpendicular) So if the car is way in toward the mast (traveller centered?) and the main sheeted hard, then this would be the worst, and not unusual scenario. But when you are travelled out, the car would be typically further back and more directly under the sail securing point, but typically without spin you dont sheet hard then...
The irony is that the old deep rectangular section is good in bending (up/down), but could buckle the weak (narrow) way in compression from the crazy mainsheet angle typical on Nacra Squares with traveller centered. The round Prindle is light and symetrical so it is a good "column" for its weight for longitudinal loading, but not for bending in one plane.
The Duhh trick that the "A" cats use is to load the mainsheet directly to the sail "around" the boom with a ring. The boom only pulls the ring in and out (outhaul) and so can be set up for pure compressive loads, and no nasty bending.
I guess you could do something similar, but you may have to have an inhaul too, when you travel out, to control your foot tension (or lack of it). The benefit would be that you could keep a pure compressive load and a minimum section to the boom. We could really geeek out on this.
The last time I tried to race I got in irons buggering around with the mast rotator, and lost say 10 boat lengths. How often does mast rotation gain you ten boat lengths, even cumulatively? How much a 10 oz lighter boom? Do it for the gee wiz factor. I have two extra Rectangular booms if you want one. How about sawing circular holes out of the sides to save weight? You could saw a lot of big ones out at the mast and less toward the mainsheet ( drop lever) anchor point. Or you could taper the bottom wall in and tig weld it back. Look real trick.
Thanks David. I have a P-19 boom section boom, as well as one of the 1" wide, 4" deep flat sections, and additionally am on the prowl for a windsurf mast piece (per Charlie's suggestion, to copy the Jav2 18HT) so I guess I'll get to try all the options! Thanks for chiming in, and I'll keep y'all updated.
Andrew,
Some of the HT crowd went with a 2" round Forte section for booms. Forte sells a bare 11 ft 2" tube for $218. Its going to be plenty strong for your boom.
www.forterts.com Talk to Tony.
Your boom could probably hitch a ride on boats going south for the races in FL for Jan.
Bill