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Scary Inverted mast #20173
06/02/03 07:54 PM
06/02/03 07:54 PM
Joined: Jul 2001
Posts: 1,246
Columbia South Carolina, USA
dave mosley Offline OP
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dave mosley  Offline OP
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Joined: Jul 2001
Posts: 1,246
Columbia South Carolina, USA
Have you ever seen a mast bend opposite of the spreaders?
I have, not too fun either. Hopefully you will have solutions for me.
I have only had this boat, a G-Force 21, for one month. Sailed it twice, both in races. The first time I sailed it the mast did everything correctly, so much so that I took the over-rotator arm off as it tangled on the Jib line every other tack. I never had problems with the mast over-rotating going to weather, or under rotating down wind. Now I only had 190 + 95 pounds on the wire, and it was blowing 15-22mph.
I took the rotator off before this weekends race.
When we were going to weather double trapped we noticed the jib flapping and the main twisting off in a very unusual way, and as gusts were hitting us, some as high as 20+ I cracked off the main. We looked up and to our horror the mast was over-rotated 180 degrees, and inverted opposite of the spreader configuration then bent back in the correct shape from the hounds up as we had a good bit of downhaul on.
I cant beleive, nor could my crew(Jake Kohl and Tommy Metts) that it did not snap in half. I have never seen any metal bend like that and come back straight. We rigged a rotation limiter and stayed off the wire, somewhat nursing the boat to the finish. It still didnt behave correctly when I cracked off the main sheet.
so what is the solution?
Tighter diamond wires?
Less rotation( I usually sail to weather with the rotator pointing at the shrouds)?

My understanding is this is the same extrusion as the NACRA 6.0- and 31.5 ft, one set of diamonds.

Any help will be greatly appreciated.

David Mosley
www.seacats.org


The men were amazed, and said, "What kind of a man is this, that even the winds and the sea obey Him?" Matthew 8:27





-- Have You Seen This? --
Re: Scary Inverted mast [Re: dave mosley] #20174
06/02/03 10:04 PM
06/02/03 10:04 PM
Joined: Nov 2001
Posts: 351
Dallas, Texas
thom Offline
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thom  Offline
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Posts: 351
Dallas, Texas
hello David- Theres several reasons for controlled mast rotation...you may have found one.

thom

Re: Scary Inverted mast [Re: dave mosley] #20175
06/03/03 08:02 AM
06/03/03 08:02 AM

A
Anonymous
Unregistered
Anonymous
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A


This also happened to my N6.0na. I have also heard of another 6.0 that had the problem. More spreader rake and more diamond tension are the only suggestions I have. After mine inverted, I straightened it, added some rake and tension, and have not had a problem since then.

Re: Scary Inverted mast [Re: dave mosley] #20176
06/03/03 08:48 AM
06/03/03 08:48 AM
Joined: Jul 2001
Posts: 397
Burlington, Vermont USA
K
Kevin Rose Offline
enthusiast
Kevin Rose  Offline
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K
Joined: Jul 2001
Posts: 397
Burlington, Vermont USA
Quote
. . . We looked up and to our horror the mast was over-rotated 180 degrees, . . .


David,

I'm trying to picture this. When you say "over-rotated 180 degrees", does that mean that the luff track was facing forward?

As for spreader rake and diamond tension, I've got my rake set to 1 3/4" and the diamond tension at 600 lbs, giving a pre-bend of 1 1/4 inches. (I run a bit less rake and pre-bend than others because I weigh in at 200 lbs and often have crew at 160 - 180 lbs.)

What does your pre-bend look like? (Should be greater than an inch, say 1 1/4 to 1 3/4, with spreaders raked to 1 3/4 to 2 inches.)


Kevin Rose N6.0na #215 Lake Champlain (New England's "west coast") Burlington, Vermont
Common Factor [Re: dave mosley] #20177
06/03/03 08:59 AM
06/03/03 08:59 AM
Joined: Jun 2001
Posts: 778
Houston
carlbohannon Offline
old hand
carlbohannon  Offline
old hand
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Posts: 778
Houston
Interesting

I have now heard of 4 cases, 3 6.0's and a G-Cat. The interesting part is they all use the same mast extrusion.

Has anyone heard of a case of mast inversion that does not use the 6.0 extrusion?

It could be it is the only extrusion thick and soft enough to survive.

kevin [Re: Kevin Rose] #20178
06/03/03 09:28 AM
06/03/03 09:28 AM
Joined: Jul 2001
Posts: 1,246
Columbia South Carolina, USA
dave mosley Offline OP
veteran
dave mosley  Offline OP
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Columbia South Carolina, USA
yes, the luff track was facing forward. Funny thing is we didnt break any battens.

David Mosley


The men were amazed, and said, "What kind of a man is this, that even the winds and the sea obey Him?" Matthew 8:27





Re: kevin [Re: dave mosley] #20179
06/03/03 10:40 AM
06/03/03 10:40 AM
Joined: Jul 2001
Posts: 397
Burlington, Vermont USA
K
Kevin Rose Offline
enthusiast
Kevin Rose  Offline
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K
Joined: Jul 2001
Posts: 397
Burlington, Vermont USA
Quote
yes, the luff track was facing forward. Funny thing is we didnt break any battens.

David Mosley


Wow,

I'm still struggling to visualize what it would take to cause such an orientation. Looking forward to hearing other's input.


Kevin Rose N6.0na #215 Lake Champlain (New England's "west coast") Burlington, Vermont
Re: kevin [Re: Kevin Rose] #20180
06/03/03 10:55 AM
06/03/03 10:55 AM
Joined: Sep 2002
Posts: 126
Northern Virginia
SoggyCheetoh Offline
member
SoggyCheetoh  Offline
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Posts: 126
Northern Virginia
It would seem like the rig tension would have to be pretty loose to allow the mast to rotate so far around.


Alec D.
Pirates of the Chesapeake www.teampiratesofthechesapeake.com
Nacra20 1057 - Crew
F16 Viper 152 - Uni
Re: kevin [Re: SoggyCheetoh] #20181
06/03/03 11:24 AM
06/03/03 11:24 AM
Joined: Jul 2001
Posts: 397
Burlington, Vermont USA
K
Kevin Rose Offline
enthusiast
Kevin Rose  Offline
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K
Joined: Jul 2001
Posts: 397
Burlington, Vermont USA
Quote
It would seem like the rig tension would have to be pretty loose to allow the mast to rotate so far around.


I agree. With my rig tensioned and without the sail up, the shrouds are pretty tight by the time I rotate the mast to 110.

You would also think that the forestay would be trying to prevent a 180 degree flip.

Seems like the mast would have to pop into an inverted position first (due to incorrect spreader/diamond setup). Then, could tension on the leech pull the mast around somehow?


Kevin Rose N6.0na #215 Lake Champlain (New England's "west coast") Burlington, Vermont
Re: kevin [Re: Kevin Rose] #20182
06/03/03 11:17 PM
06/03/03 11:17 PM
Joined: Jun 2001
Posts: 12,296
South Carolina
Jake Offline
Carpal Tunnel
Jake  Offline
Carpal Tunnel
Joined: Jun 2001
Posts: 12,296
South Carolina
I was on the boat and it was definitely startling to see the "S" shape the mast had presumed with two of us on the wire and one on the hull. The rig tension was not terribly tight and while the diamond wires were snug, there was not a whole lot of prebend when compared to my 6.0NA. Additional downhaul brought the mast closer to the 6.0 mast shape that I was used too. I think that the diamonds and the rig could use more tension to prevent that negative bend.


Jake Kohl
Jake [Re: Jake] #20183
06/04/03 06:06 AM
06/04/03 06:06 AM
Joined: Jul 2001
Posts: 1,246
Columbia South Carolina, USA
dave mosley Offline OP
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dave mosley  Offline OP
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Joined: Jul 2001
Posts: 1,246
Columbia South Carolina, USA
Thanks for your handy engineering that saved the day and still let us enjoy 3rd.

David


The men were amazed, and said, "What kind of a man is this, that even the winds and the sea obey Him?" Matthew 8:27





Re: Jake [Re: dave mosley] #20184
06/04/03 12:02 PM
06/04/03 12:02 PM
Joined: Jun 2001
Posts: 833
St. Louis, MO,
Mike Hill Offline
old hand
Mike Hill  Offline
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Posts: 833
St. Louis, MO,
I would sweep the spreaders back at least 2 1/2" and make sure the tension is 450lbs or greater.

Mike Hill
H20 #791


Mike Hill
N20 #1005
Re: Dave [Re: Mike Hill] #20185
06/04/03 05:35 PM
06/04/03 05:35 PM
Joined: Jun 2002
Posts: 1,658
Florida Suncoast, Dunedin Caus...
catman Offline
Pooh-Bah
catman  Offline
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Posts: 1,658
Florida Suncoast, Dunedin Caus...
Hi Dave, I met you on the beach when you were picking that beast up.

That mast is not the stock G21 mast as you know. It's my understanding that it is a mast from N6.0. The stock mast for that boat was 34'. So you should be able to tune it like a N6.0.

What I can't remember is if it had a boom or not. If it's boomless you might want to move the main sheet foward on the clew plate (if you can) resulting in a tighter foot. That might help the problem. Your gonna want to have the abilty to control rotation so you need to find the solution to the lines fouling.

Mike


Have Fun
Re: Dave [Re: catman] #20186
06/04/03 08:30 PM
06/04/03 08:30 PM
Joined: Jul 2001
Posts: 1,246
Columbia South Carolina, USA
dave mosley Offline OP
veteran
dave mosley  Offline OP
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Joined: Jul 2001
Posts: 1,246
Columbia South Carolina, USA
I cant imagine having more sail area on this boat. It is a bear to handle with the area it has now. It seems to fly a hull in no wind, and I really have a time keeping t down when the winds up. The rig now is boomless, and doesnt look like it has ever had a gooseneck attached.
I was told by Glen that Hans used the 6.0 mast extrusion because it was readily available and in order to get an extrusion custom made he would have to buy 4000 feet. Maybe a load od BS, but thats what he told me. I didnt get any riggin tips, and man I sure need them, so the 6.0 tips are going to be my gameplan for now.
The rotation arm was basically an over-rotator , mounted forward of the mast and cleated to both sides of the main beam. I am going to switch it to a limiter, facing it aft. Hopefully that will solve some of my problems.

Thanks,
David


The men were amazed, and said, "What kind of a man is this, that even the winds and the sea obey Him?" Matthew 8:27





Re: Dave [Re: dave mosley] #20187
06/04/03 11:08 PM
06/04/03 11:08 PM
Joined: Jun 2002
Posts: 1,658
Florida Suncoast, Dunedin Caus...
catman Offline
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catman  Offline
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Posts: 1,658
Florida Suncoast, Dunedin Caus...
Dave, a couple guys around here run that foward arm. They have a shock cord running from about where the diamonds attach on the mast out to the furler. This preventer for the jib sheet seems to work. If you haven't you might want to try it first.

I was just rereading your orig. post. Remember you set your rotator by sheeting in your sail while going to weather and looking at the lee side of the sail-mast junction adjust the rotator so the air flows smoothly into the sail. Depending on the sail you might find the spot to rotate to a little more or less then the shroud.

Have Fun,
Mike

Last edited by catman; 06/04/03 11:31 PM.

Have Fun
Re: rotators [Re: dave mosley] #20188
06/05/03 11:16 AM
06/05/03 11:16 AM
Joined: Jul 2001
Posts: 390
samevans Offline
enthusiast
samevans  Offline
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Posts: 390
Hi Dave,
RE: rotation limiter.
You could try the system that is on the Hobie 20.
It does not connect to the boom, so it will work on a boomless boat.
The line runs from the arm, through a grommet in the tramp and cleats on the hulls.
It is easy for the crew to adjust without moving to the center of the boat.
Even the Tigers and Foxes are switching to it.

RE: postive rotator
Many people like the forward bar and cleats, but I had it on my 18sq and felt it was problematic.
I prefer the bungee cord type, like on my 17. It works with the rear facing bar.
It is automatic and it always holds the mast steady instead of allowing it to flog around in light air chop.

Are you going to the Charleston regatta?
There will be many different variations of roatators on the different boats.

Re: rotators [Re: samevans] #20189
06/05/03 12:42 PM
06/05/03 12:42 PM
Joined: Jul 2001
Posts: 2,844
42.904444 N; 88.008586 W
Todd_Sails Offline
Carpal Tunnel
Todd_Sails  Offline
Carpal Tunnel
Joined: Jul 2001
Posts: 2,844
42.904444 N; 88.008586 W
AS I have previously posted, my inverted N6.0 mast, is still working with manual bending back, then increased spreaker rake and increased wire tension.

Dave,

Do you use a jib sheet jam preventer?

Todd


F-18 Infusion
#626- SOLD it!

'Long Live the Legend of Chris Kyle'
Re: rotators [Re: Todd_Sails] #20190
06/05/03 04:44 PM
06/05/03 04:44 PM
Joined: Jul 2001
Posts: 1,246
Columbia South Carolina, USA
dave mosley Offline OP
veteran
dave mosley  Offline OP
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Joined: Jul 2001
Posts: 1,246
Columbia South Carolina, USA
Hi Todd,
I have always used a simple bungee system for jam prevention, but didnt really have time to work on the boat or find the correct settings. This is my plan.
prebend to 2 inches-400#s +/- tension on the Loos Gauge
Tighten my rig tremendously(As Sam can vouch it was pretty loose)
Jam prevention bungee
Mast rotator limiter(it will obviously rotate 180 degrees, so positive rotation is not a factor)
Replace all worn pins, rings, crappy rigging

Thanks for all the input!!
David Mosley


The men were amazed, and said, "What kind of a man is this, that even the winds and the sea obey Him?" Matthew 8:27





Re: Scary Inverted mast [Re: dave mosley] #20191
06/09/03 01:47 PM
06/09/03 01:47 PM
Joined: Apr 2002
Posts: 591
Bradenton, FL
Sycho15 Offline
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Sycho15  Offline
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Joined: Apr 2002
Posts: 591
Bradenton, FL
Dave, you got a G-Force 21? You lucky bastad. I'm sorry, but I lost your mailing address and forgot to get it again to mail you all that G-Cat literature. There's a brochure on G-Force 21s, too. By any chance do you have the 11' wide Grand Prix model? Those have to be my all-time favorite boat. There's a guy just south of me with one of those and a mast supposedly taller than a Tornado's rig


G-Cat 5.7M #583 (sail # currently 100) in Bradenton, FL Hobie 14T
Re: Scary Inverted mast [Re: Sycho15] #20192
06/09/03 02:06 PM
06/09/03 02:06 PM
Joined: Jun 2001
Posts: 12,296
South Carolina
Jake Offline
Carpal Tunnel
Jake  Offline
Carpal Tunnel
Joined: Jun 2001
Posts: 12,296
South Carolina
That 8.5' wide G-Force has a hard enough time tacking with those deep V hulls! I can't image trying to tack an 11' wide version. However, it's fast in a straight line and with PLENTY of room on board.


Jake Kohl
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