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Nacra 5.0 diamond wires? #252878
09/30/12 05:18 PM
09/30/12 05:18 PM
Joined: Mar 2006
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Arizona
AzCat Offline OP
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I picked up an "83 N5.0 and it has diamond wires. I'm wondering if their stock. The top attachment is on the front of the mast and is a single point attachment. The spreader is a straight bar and looks to be in the correct position. The bottom attachment is single with a turnbuckle. The wire is slack to the point that I can squeeze them together about 20" above the turn buckle.
It seems to me that the mast will invert or bend backward under load. I guess that it may just bend on its small access w the slack diamonds.

Anyway, is this a stock diamond setup for the 5.0?

Also, I have a "76- 5.2 and the wires run from center top to a straight spreader, and to center at the. Ottom attachment with a bottle adjuster at the bottom


Auscat MKV 444 A class
NACRA I-20- 440/CATHATKA
-- Have You Seen This? --
Re: Nacra 5.0 diamond wires? [Re: AzCat] #252898
10/01/12 09:30 AM
10/01/12 09:30 AM
Joined: Aug 2003
Posts: 351
Santiago, Chile
Andinista Offline
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You probably have the wires for non straight spreaders that have the newer 5.0s. If so, it might a be better idea to change the spreaders instead of the wires.
Porbably this one. Not adjustable though:
http://www.ebay.com/itm/Prindle-Nac...Gear&hash=item2321013011&vxp=mtr

Re: Nacra 5.0 diamond wires? [Re: Andinista] #253082
10/03/12 06:51 PM
10/03/12 06:51 PM
Joined: Mar 2006
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Arizona
AzCat Offline OP
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Did the original 5.0 have wires? this looks like a factory setup bu i cant see how it would help shape the mast in a positive way. seems like the straight spreader would bend forward and collapse. I dont really like the idea of having a great big hole drilled in the mast. If I take the current spreader out it will leave the hole un supported. Gives me the creeps.


Auscat MKV 444 A class
NACRA I-20- 440/CATHATKA
Re: Nacra 5.0 diamond wires? [Re: AzCat] #253104
10/04/12 08:37 AM
10/04/12 08:37 AM
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Houston
carlbohannon Offline
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The 5.0 was factory equipped with diamond wires. The spreaders were adjustable. The factory recommended ~1.5-1.75 rear rake. I do not know what spreaders are on your boat but I would not sail with them.

I think the 5.0 used the 5.2 extrusion, which is pretty flexible. A good starting point for the 5.0 would be 1.75 aft rake with 200-300 lbs tension. This is something close to how they set the boat when it was new, beyond that it is up to you.

The NACRA Manuals are available for download:

http://nacrasailing.com/index.php?option=com_phocadownload&view=category&id=1:manuals&Itemid=91

Try the Vintage

Good Luck

Re: Nacra 5.0 diamond wires? [Re: AzCat] #253107
10/04/12 08:54 AM
10/04/12 08:54 AM
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Santiago, Chile
Andinista Offline
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Older ones did have a straight spreader, I've seen a couple.
I would be more concerned about water coming through that hole when capsized. Unless you really care about fine tuning this old boat. I don't see how the spreader would bend forward and collapse. You still have the cunningham to bend the mast. But even without that, I don't see how the mast or the straight spreader would bend forward

Re: Nacra 5.0 diamond wires? [Re: AzCat] #253109
10/04/12 09:01 AM
10/04/12 09:01 AM
Joined: Aug 2003
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Santiago, Chile
Andinista Offline
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Said otherwise, those spreaders only add rigidity in the soft axis of the mast. They don't help bending it. I don't think it's such a big deal for that boat.
This one has sailed for years:
[Linked Image]
[Linked Image]

Attached Files
n5 1.JPG (142 downloads)
n5 2.JPG (139 downloads)
Re: Nacra 5.0 diamond wires? [Re: AzCat] #253115
10/04/12 09:49 AM
10/04/12 09:49 AM
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Santiago, Chile
Andinista Offline
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I read your first post again and I think your concern is about the attachment points being in the front of the mast, therefore bending it the opposite way. I'd say that with this straight spreader you need less tension than with adjustable ones, because you are not using the diamong wires to pre-bend the mast. The pictures above are from a friend's 5.0, I checked other pictures and it seems they are also attached in the front.

Last edited by Andinista; 10/04/12 09:50 AM.
Re: Nacra 5.0 diamond wires? [Re: Andinista] #253185
10/05/12 11:47 AM
10/05/12 11:47 AM
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Arizona
AzCat Offline OP
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As long as I know that it was a factory setup I guess I'll leave It as is for now, according to today's logic, it didn't seem right, and I'm sure it isn't right to induce the correct / wanted bend in the mast. The boat is pretty basic right now, I'll sail it simple for a while and see how it does. I'll be racing a P-16, P-18, 18ht, tiger, G-Cat 18 and 16ht this weekend, p-16 is the only boat that rates higher than the 5.0. No line honors for me this time. It ill kick butt on Portsmouth! Bring it on boys!


Auscat MKV 444 A class
NACRA I-20- 440/CATHATKA
Re: Nacra 5.0 diamond wires? [Re: AzCat] #253186
10/05/12 12:49 PM
10/05/12 12:49 PM
Joined: Jun 2001
Posts: 12,310
South Carolina
Jake Offline
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Originally Posted by azcat
As long as I know that it was a factory setup I guess I'll leave It as is for now, according to today's logic, it didn't seem right, and I'm sure it isn't right to induce the correct / wanted bend in the mast. The boat is pretty basic right now, I'll sail it simple for a while and see how it does. I'll be racing a P-16, P-18, 18ht, tiger, G-Cat 18 and 16ht this weekend, p-16 is the only boat that rates higher than the 5.0. No line honors for me this time. It ill kick butt on Portsmouth! Bring it on boys!


Practically every catamaran prior to 1985 had straight spreaders that stuck through a hole in the mast. The hot boats started introducing raked spreaders and masts with prebend setups...it didn't take long for the rest to follow suit. The straight spreader has been around a long time - there's nothing wrong with it structurally...it's just not quite as tunable.


Jake Kohl
Re: Nacra 5.0 diamond wires? [Re: Jake] #253229
10/07/12 09:53 PM
10/07/12 09:53 PM
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Arizona
AzCat Offline OP
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Is there any precident for removing the straight and adding a raked spreader? Or would it require a new mast?


Auscat MKV 444 A class
NACRA I-20- 440/CATHATKA
Re: Nacra 5.0 diamond wires? [Re: AzCat] #253239
10/08/12 06:26 AM
10/08/12 06:26 AM
Joined: Aug 2003
Posts: 351
Santiago, Chile
Andinista Offline
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I don't know, I'd do it. And IŽd try to seal the hole forever, with the right product, not sure what it is.

Re: Nacra 5.0 diamond wires? [Re: AzCat] #253246
10/08/12 09:05 AM
10/08/12 09:05 AM
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South Carolina
Jake Offline
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I'm sure it's been done, but raked spreaders put considerably more loading on the mast...and you've got a hole right where that load is highest. Where you might have run 10 or 30 lbs of diamond wire tension with the straight spreaders, you're probably looking at upwards of 500 lbs or more with the raked spreaders...I probably wouldn't mess with it.


Jake Kohl
Re: Nacra 5.0 diamond wires? [Re: AzCat] #253350
10/09/12 11:46 PM
10/09/12 11:46 PM
Joined: Mar 2006
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Arizona
AzCat Offline OP
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Yea Jake, I was leaning in that direction. That's a pretty big hole an I don't want to do anything that hasn't been done successfully by other brave souls, thanks all for your input.


Auscat MKV 444 A class
NACRA I-20- 440/CATHATKA
Re: Nacra 5.0 diamond wires? [Re: Jake] #253360
10/10/12 09:33 AM
10/10/12 09:33 AM
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Houston
carlbohannon Offline
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The purpose for swept or adjustable spreaders on 80's NACRA's was not pre-bend. The purpose was to stabilize the mast against inversion. The 5.2 extrusion is very flexible by any standards. To stabilize the mast the spreaders were swept aft 1.5 - 2 in and the wires the wires were set "tight". By the early 90's we were using 300-500 lbs on the 5.5 uni, which used the same extrusion.

30 year old memories are fuzzy but some type of swept spreaders was being used on NACRA's prior to 1985. The Hobie 18 had adjustable spreaders in 1977 and I remember a meeting at sailmaker where they talked about the importance of raking the spreaders aft in ~1982.

Re: Nacra 5.0 diamond wires? [Re: carlbohannon] #253362
10/10/12 11:43 AM
10/10/12 11:43 AM
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Santiago, Chile
Andinista Offline
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Originally Posted by carlbohannon
The purpose was to stabilize the mast against inversion

Please explain

Re: Nacra 5.0 diamond wires? [Re: Andinista] #253385
10/11/12 10:11 AM
10/11/12 10:11 AM
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Posts: 778
Houston
carlbohannon Offline
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In simple terms, mast inversion is when the mast bends forward instead of aft. When the mast is inverted, you no longer have the expected aft curve that matches the luff curve on your sail. When your mast is inverted, your sail shape is "not fast". This is normally, the worst you see.

When your mast is inverted, you can also get "S" shapes and even more complicated shapes. When the mast starts to move or oscillate in "S" shapes, that is very bad, your mast may fail.

Raking the spreaders aft, with tight diamond wires, puts a force on the mast that try's to bend it the way you want it to and (I am told) stiffens it against motion in other directions.

The problem is worse on the 5.5 uni or NACRA 18sq, which use the same extrusion but, the mast is longer and square top mains make it worse. I have seen 18 sq's rip the top of the sail out or break the mast. This normally happened, downwind in heavy puffy air.

Minor inversions happen on a lot boats and are not that bad. Big inversion or complex shapes that move are very bad. When the mast is oscillating, the wrong load in the wrong direction, cab break the mast.

Tapered, pre-bent masts are the next step. You make the mast easy to bend in the directions you want. at the same time you make it stronger down low and stiffer in directions you don't want it to bend.

Re: Nacra 5.0 diamond wires? [Re: AzCat] #253399
10/11/12 07:57 PM
10/11/12 07:57 PM
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Santiago, Chile
Andinista Offline
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Thanks!

Re: Nacra 5.0 diamond wires? [Re: Andinista] #253417
10/12/12 10:10 AM
10/12/12 10:10 AM
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Naples, FL
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does the Nacra 5.5sl have straight spreaders? I was thinking of picking one up for singlehanding and slapping a small spin on it...


Jay

Re: Nacra 5.0 diamond wires? [Re: waterbug_wpb] #253424
10/12/12 10:49 AM
10/12/12 10:49 AM
Joined: Oct 2005
Posts: 1,152
tampa, fl
K
ksurfer2 Offline
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tampa, fl
Originally Posted by waterbug_wpb
does the Nacra 5.5sl have straight spreaders? I was thinking of picking one up for singlehanding and slapping a small spin on it...


The ones I have seen had raked spreaders. One even had a carbon mast.


If your havin girl problems i feel bad for you son
I got 99 problems but my beautiful wife ain't one
Re: Nacra 5.0 diamond wires? [Re: waterbug_wpb] #253427
10/12/12 11:48 AM
10/12/12 11:48 AM
Joined: Jun 2001
Posts: 12,310
South Carolina
Jake Offline
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Originally Posted by waterbug_wpb
does the Nacra 5.5sl have straight spreaders? I was thinking of picking one up for singlehanding and slapping a small spin on it...


You're doing a lot of "thinking" lately. Feeling OK?


Jake Kohl
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