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Old Jun 21, 2011, 09:37 AM
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Dick L.'s Avatar
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Crash -
The boom stays pretty much relative to its postion to the mast. Moving the grommet and location to different screw eyes changes the "fulcrum" of the upwards pull of the forestay and the down pull of the jib leach. Photo was taken from slightly aft of 90 degree angle to boat so there is a little optical illusion, although the mast in forward step and boom at rear screw eye mounting does result in jib boom intereference with mast.

Please keep in mind, the RG65 class allows a variety of rigs and sail sizes (no minimum, only maximum) so this will accomodate small area/foot jibs for higher winds. Smaller jib requires mast forward to balance the CE of sails. If only a smaller jib, the boat would have a lot of weather helm. The jib shown happens to be from the "A" rig. Since the Nirvana is a one design class, there is no "class" option for changing sial area size that I am aware of - not to say for fun sailing the foredeck couldn't be modified.

Photo showing mast/jib relationship was taken during maiden sail - and in pretty light winds. There is enough room for jib to self tack, but the mainseet post to the main was still too tall and hit the main boom. It has since been shortened for clearance. Also, I prefer bow-up if wondering, since any wind will have tendency to pull bow down, and further gusts will drive bow down further.

NOW - back to the Nirvana discussion.
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Old Jun 21, 2011, 01:43 PM
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Originally Posted by Dick L. View Post
Crash -
The boom stays pretty much relative to its postion to the mast. Moving the grommet and location to different screw eyes changes the "fulcrum" of the upwards pull of the forestay and the down pull of the jib leach.
Ok...bear in mind I don't have my boat here to look at...but if I use the stock set up and only move the gromlet...let's say 1 inch forward, isn't that in effect going to move the entire jib aft 1 inch closer to the mast?

And that is what I need to do to get more lift out of the bow? Do I understand this correctly?
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Old Jun 21, 2011, 02:06 PM
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If the boom to deck height stays the same, but you slide the grommet forward, then "yes" the jib leech and boom will be closer to the mast.

As for added "lift" - I'm not sure as you have actually shifted your CE of the sails aft a percentage of that 1 inch difference. Using the first RG photo - "IF" you could loosen the deck to jib boom (white) line, to allow the boom to rise on a downhill run, you might find a bit more lift as the jib would have more "belly" in the sail and act like a "poor-mans" spinnaker. Basically using the jib-to-deck line and the jib sheet line to control how high the boom would rise. How to control that deck attachment line is the question - unless it was connected to another servo/winch.

I'm not familiar with the space you have below decks, but theory is to sheet out the main and jib, and at the same time allow the boom to rise, thinking that the jib might gain some upward lift instead of straight forward. Personally, if winds are that strong, you wold have less tendency to pitchpole if you "reach and gybe" downwind keeping wind off the rear quarter - at worst you might round-up to weather before stuffing the bow. Gotta keep the rudder in the water for steering - reach off in puffs and head back down in steady air might be a solution.

Cheers.
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Old Jun 21, 2011, 02:17 PM
Boomer1
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Crash
I think an inch would be extreme - I like the way Dennis achieves the adjustment - it gives you a way to make small incremental adjustments or larger without drilling any holes.

I suppose once you found the right placements for varying conditions you could install a jib rail. Again, using the sliding grommet is very easy to set up.

A friend of mine has a Yamaha RTW like mine, and purchased a set of Dennis's custom sails for it, but when he first installed them, the boat didn't handle correctly - I assumed because of the sails being so much more efficient than the stock sails. They changed the dynamics of the boat. Dennis suggested he move the jib connection from it's original location to a point further back - which of course changed the geometry. The gap between the mast and sail changed - My friend played around with it until he found the "happy spot" - and it was better.

I am not crazy about the material most of these sailmakes use to make paneled sails with. To me it is very fragile and can crease very easily. I like custom made sails made out of ripstop fabric better. They are more durable and work almost as well. (one man's opinion)

Dennis made another set for my friend out of a material very much like the factory sails (ripstop) and they worked perfectly - The original material failed for some reason and Dennis was great about it, and replaced them. Good guy!

When the time comes, I will have Dennis make a set of those for my Yamaha and for my Nirvana too. I must be weird because I like the factory Nirvana sails.
I am quite sure they are bullet proof - John feels his custom sails make a big differenc on his boat, so I'd like to see what they'd do for Nirvana - They look terrific.

That's my story and I'm sticken to it!
Boomer

Oh, great looking boat Dick!
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Old Jun 21, 2011, 02:41 PM
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Thought I'd do some decoding - Not coming from sailing background, the lingo is sometimes is unclear, so I look up the terms to learn. I think these are correct -Dick or anyone that knows, can correct me if I am off the mark.

These are terms Dick used in his post below:
jib leech = distance of outside edge of a jib sail to the mast.

reach = sailing on a tack with the wind roughly abeam, all sailing points between running and close-hauled.

abeam = directly to the side of the boat.

close- hauled = sailing close to the wind with sails pulled in.

gybing or jibing = changing direction with the wind aft; to change from one tack to another by turning the stern through the wind; can be spelled either way.

round up to weather = turing into the wind (weather = windward, opposite of leeward.)

Boomer
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Old Jun 21, 2011, 03:06 PM
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Originally Posted by Boomer1 View Post
Thought I'd do some decoding - Not coming from sailing background, the lingo is sometimes is unclear, so I look up the terms to learn. I think these are correct -Dick or anyone that knows, can correct me if I am off the mark.

These are terms Dick used in his post below:
jib leech = distance of outside edge of a jib sail to the mast.

reach = sailing on a tack with the wind roughly abeam, all sailing points between running and close-hauled.

abeam = directly to the side of the boat.

close- hauled = sailing close to the wind with sails pulled in.

gybing or jibing = changing direction with the wind aft; to change from one tack to another by turning the stern through the wind; can be spelled either way.

round up to weather = turing into the wind (weather = windward, opposite of leeward.)

Boomer

I think those are right Boomer...
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Old Jun 21, 2011, 03:14 PM
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Originally Posted by Dick L. View Post
If the boom to deck height stays the same, but you slide the grommet forward, then "yes" the jib leech and boom will be closer to the mast.

Ok...that's what I thought.

As for added "lift" - I'm not sure as you have actually shifted your CE of the sails aft a percentage of that 1 inch difference. Using the first RG photo - "IF" you could loosen the deck to jib boom (white) line, to allow the boom to rise on a downhill run, you might find a bit more lift as the jib would have more "belly" in the sail and act like a "poor-mans" spinnaker. Basically using the jib-to-deck line and the jib sheet line to control how high the boom would rise. How to control that deck attachment line is the question - unless it was connected to another servo/winch.

I'm still confused here...are you saying let the boom lift higher off the deck? Would that also mean leaving the fore stay looser so the sail can lift? And...does the jib need to go forward or aft? Which way to move the gromlet?

I'm not familiar with the space you have below decks, but theory is to sheet out the main and jib, and at the same time allow the boom to rise, thinking that the jib might gain some upward lift instead of straight forward. Personally, if winds are that strong, you wold have less tendency to pitchpole if you "reach and gybe" downwind keeping wind off the rear quarter - at worst you might round-up to weather before stuffing the bow. Gotta keep the rudder in the water for steering - reach off in puffs and head back down in steady air might be a solution.

We have no access below deck.

Cheers.
Maybe I just need to go home...
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Old Jun 21, 2011, 04:02 PM
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When the jib boom pivot location on the boom is moved , it changes the rate at which the jib swings in and out with sheet tension. So the jib or main boom sheet attachment locations may also need to be changed to keep the jib's movement synched with the mainsail's movement as desired. Stock Nirvana sheet-boom attachment locations are fixed, so they may also need to be changed to adjustable like in the super Nirvana pic.
For more on boom/sheet geometry go to
http://onemetre.net/Build/Sheeting/Sheeting.htm

Boomer, I actually read the Templus Catcus post in 2007 and put a rubber grommet on the Nirvana jib boom pivot like in the super Nirvana and RG65 pics. I never really noticed much difference when moving it around, but I wasn't trying to correct anything and probably wasn't a very good tester.
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Old Jun 21, 2011, 04:21 PM
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Originally Posted by jpatters View Post
When the jib boom pivot location on the boom is moved , it changes the rate at which the jib swings in and out with sheet tension. So the jib or main boom sheet attachment locations may also need to be changed to keep the jib's movement synched with the mainsail's movement as desired. Stock Nirvana sheet-boom attachment locations are fixed, so they may also need to be changed to adjustable like in the super Nirvana pic.
oh...oh...now it's getting more complicated....
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Old Jun 21, 2011, 05:39 PM
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Crash - a minor point/change. Leech is the trailing edge of a sail - can be jib or main.
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Old Jun 21, 2011, 08:02 PM
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How bout sail the boat...
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Old Jun 21, 2011, 08:22 PM
Boomer1
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Quote:
Originally Posted by jpatters View Post
When the jib boom pivot location on the boom is moved , it changes the rate at which the jib swings in and out with sheet tension. So the jib or main boom sheet attachment locations may also need to be changed to keep the jib's movement synched with the mainsail's movement as desired. Stock Nirvana sheet-boom attachment locations are fixed, so they may also need to be changed to adjustable like in the super Nirvana pic.
For more on boom/sheet geometry go to
http://onemetre.net/Build/Sheeting/Sheeting.htm

Boomer, I actually read the Templus Catcus post in 2007 and put a rubber grommet on the Nirvana jib boom pivot like in the super Nirvana and RG65 pics. I never really noticed much difference when moving it around, but I wasn't trying to correct anything and probably wasn't a very good tester.
JP
My sense is that the changes we are discussing would have more impact on a Nirvana with custom sails. The stock materials lend themselves more to long term durability than to being highly efficient. Granted they work fine, but not to the level custom sails do. I guess what I am suggesting is the Nirvana is not a high strung race boat that every tiny modification may eek out more speed.

I just like um! I have boats that are high tech, and love um, but something about the Nirvana keeps me interested.

Boomer
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Old Jun 22, 2011, 07:35 AM
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As you all know I'm still lookin for an "easy" solution to the submarine problem whilst staying within the rules. I was hoping this was it...but I dont want to start re-rigging the boat to test it out...a minor thing like a movable gromlet is one thing, but then you start adding other things on top of that....it is no longer a "easy" solution.

I agree what Chidago just posted....just sail it!
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Old Jun 22, 2011, 04:52 PM
Boomer1
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More good information for the Official Nirvana knowledge base.

The point being - we have learned more good things from yet another informative dialog. Adding this little feature to ones Nirvana or other fine RC Yacht, may or may not add a measurable difference, but it does give us yet another thing to add to our superior knowledge base that certainly will dazzle and amaze those less fortunate's that don't know to read this fine thread!

Add it or don't', go fancy, go simple that is each individual skipper's decision. I say, it is better to know than not too!

"Sail on Dudes, and be excellent to yourselves!

The Boomer has spoken!
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Old Jun 22, 2011, 08:00 PM
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I try and be "excellent" to myself everyday...
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