Jib Boom

by **Capt. Flak** » Tue Sep 16, 2003 5:43 pm

I have seen some very innovative designs in jib booms on full size boats and I think I can duplicate them on my 12. Basically the forestay would be fixed on the centerline of the fordeck like a full sized boat. the clue would be attached to the end of a boom mounted at a fixed point on the deck some distance aft of the forestay.

I know that the boom would require a vang or some means of adjusting its position to get the correct sail shape. I have seen some pictures of this design in New Zealand. Without getting into too much explanation of my idea, I would like to know if anyone has seen this in the past, or experimented with it.

I want to know if it has been done here and why we don't see it being done. Obviously it is more complicated, but I think it would allow for higher pointing angles and better sail shape when reaching and running.

Joe Walter #24

by **s vernon** » Wed Sep 17, 2003 10:41 am

Joe,

I worked on it for about a year. My best system had a cf tube in the hull and a cf arrow shaft attached hard to an al arrow shaft jib boom. Acceleration was very good. Leech control was the downfall. I had a vang and could pull the aft end of the boom down - even bend it a little for leech control. The big problem was that just a tiny bit of play or bending below the vang connection at the front end gives a large amount of play at the aft end of the boom. I had about 1/2 inch of play at the back and that was not good. My system worked better in light wind. In a breeze the aft end of the boom would rise, freeing up the jib leech and killing the power in the jib. So I had bending of the fitting below the vang too. Again not good.

Another problem is that it is extremely cumbersome and windage unfriendly to make any kind of fwd counterweight for offwind jib out. You really have to rely on a twitcher. The big thing is that the entire weight of the jib boom has to be swung out by the wind and as we know the jib boom rises as it swings out. So the wind has to do the work of raising the jib boom - no offset to help you like on a std jib rig. It is just so much more pleasant to see the jib boom flop over where IT wants to be downwind in even the slightest breeze.

I am sure it is possible to overcome the obstacles, but not possible for me (without a machine shop). Like I said, even the tiniest amount of play - the New Zealand fitting might have a tiny bit of play or maybe not - at the front end screws it up. Tightening down on the vang does not eliminate the play.

You have to make sure that the elimination of play does not cause binding in the boom rotation. Maybe Stainless Steel (ala Microsail) would do the job, but I am through playing with it.

I could email images if you are interested in my designs. To you to Chris if you are interested.

Scott

by **Capt. Flak** » Wed Sep 17, 2003 2:00 pm

Thanks for the input Scott,

My idea is based on a design I saw on the Alerion 28 (full size) It has an aluminium boom with an elbow bend into a socket that is unter the deck. This socket is both the pivot point and the vang.

I would need to machine the socket fitting and that is my first draw back. The other idea I have around the counter balance issue is to use a small servo with a push pull double arm attached to bungy cords. I would use a toggle switch on the TX to simply switch from starboard to port and back. The bungy would always pull the boom out and the sheet line would pull in.

Again, this makes for a rather complicated set up. And it probably is not worth it. But then again, if I could get it to work, I might just be sailing past everyone.

But, But, and more Buts, after 30 years of guys tinkering with this class, they are still using the same method.

I will keep thinking about it and maybe nothing else.

thanks

Joe Walter #24

by **kahle67** » Thu Sep 18, 2003 4:04 pm

Joe,

AC boats use this method occasionally. If it works with their sail area, I'm sure it will with the 12. Can't find my Quarterly issue when they were the featured class but there were pictures and limited info about it. Guess you would have to contact the builders personally and pick their brain.

Reichard

by **philair** » Mon Sep 22, 2003 11:05 am

Dick Garnache (rgarnache@cfl.rr.com)made such an arrangement for his Victoria. I'd suggest you email him for more info & perhaps a picture. His arrangement works extremely well but I don't think it adds anything to the performance. If you like to tinker, go for it.

Phil Ehlinger

by **yachtie** » Sat Sep 27, 2003 5:52 pm

One of our older boats (1986) has this setup working very successfully her in NEW ZEALAND! The sails don't look the best offwind but they somehow work. The efefct downwind is LOTS of shape - similar to a gennaker and in heavier airs there is better boat control. Just yesterday I took some photos of this and will post next week.
Incidentally this boat is a regular winner on the water.

[8D]

by **yachtie** » Tue Sep 30, 2003 4:17 am

Sorry folks [:(] - just tried to add photos and then read FAQ page which says they are not possible here for security reasons.
If anyone would like copies of these photos I have taken of jib boom arrangement please email me at ec12nz@paradise.net.nz and they will be sent in an acceptable file size of around 50kb each.

[:o)]

by **Doug Wotring** » Tue Sep 30, 2003 11:55 am

feel free to post them in the phot section of http://groups.yahoo.com/group/WRMYC

by **PaulP** » Tue Sep 30, 2003 10:47 pm

Joe,
New Zealand runs a class called the J100. Take a look at this page, it shows their radial jib fitting.

http://homepages.caverock.net.nz/~stbal ... b%20detail

Paul Proefrock

by **IanHB** » Thu Oct 02, 2003 2:45 am

I have posted on the WRMYC site NZ album two photos of a jib club made by PJ wiles in UK
that I have been using for the past few years. A work of art with stainless bearings etc.
I have gone back to the standard setup so it is surplus if anyone wants it.
Special price US$40 plus postage. Or make me an offer I can`t refuse. [8D]

[;)]

nerds of the wold untie

by **Doug Wotring** » Thu Oct 02, 2003 9:15 am

HI Ian, I am going to move your jib club fitting photos to a for sale album

Doug WRMYC

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