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| |  Re: Nacra 5.5 Dolphin striker failed
[Re: Jake]
#198968
12/14/09 02:19 PM 12/14/09 02:19 PM |
Joined: Jul 2001
Posts: 1,200
Vancouver, BC Tornado 
veteran
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veteran
Joined: Jul 2001
Posts: 1,200
Vancouver, BC | I stand corrected. We have always used aluminum on the earlier NACRA designs. I missed the details in the top photo. The new 20s and F 18s might be using stainless. I'm scratching my head:-)
My guess now is that salt water/corrosion and a loose rig/rod - fit through the main beam via the nuts for compression led to the bar failure. Now, what effect would a stainless bar have on the aluminum main beam other than add weight and electrolysis? Do not forget the four drilled holes for the spin strut.
One half inch of pre - bend in the main beam was good for us in the 5.5 SL "Golden Days." We kept the rig tight and the beer cold.
We even beat NACRA 6.0s on a good day - boat for boat (circa 1993).
Keep it Rollin' in 2010,
Bert I've just never seen an aluminum striker bar. Sure, there would be some additional electrolysis but not any more than with the striker post. The stainless has better fatigue resistance - particularly at bends. It would also tend to elongate at mounting holes more than shear like aluminum. All older Tornados had alu dolphin striker straps. The only failures I have heard of were due to owner mistakes (like snagging a marker bouy and dragging against the striker post, causing it the bbend/break...then failing the beam). Stainless first started appearing in mid-80's with the Marstrom boats. The Marstrom main beam was much heavier than older makes...partly due to the strap...but they also have heavier internal bulkheads.
Mike Dobbs
Tornado CAN 99 "Full Tilt"
| | | Re: Nacra 5.5 Dolphin striker failed
[Re: Tornado]
#198976
12/14/09 04:17 PM 12/14/09 04:17 PM |
Joined: Sep 2007
Posts: 757
japan erice
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Posts: 757
japan | "One half inch of pre - bend in the main beam was good for us in the 5.5 SL "Golden Days." We kept the rig tight and the beer cold."
wow!, half an inch is 12mm, think i used 5mm when i redid my 5.2 beam last year
12mm would put a huge load on that small area. esp. if it had corrosion pitting and then an extra large spin to deal with...
it looks like the hong kong guy had close to an inch? of prebend as he says the beam was cranked up until it was basically touching the ball. if that's the case i'd say it was WAY over tensioned and that led to cracking of the strap at the 1st bolt hole
eric e
1982 nacra 5.2 - 2158
2009 weta tri - 294
| | | Re: Nacra 5.5 Dolphin striker failed
[Re: erice]
#199047
12/16/09 02:58 AM 12/16/09 02:58 AM |
Joined: May 2009
Posts: 4
Hong Kong & Thailand rustyhelms OP
stranger
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OP
stranger
Joined: May 2009
Posts: 4
Hong Kong & Thailand | Perhaps the ball was almost touching striker rod lock nut...saying..yes,an inch. After fully rigged, v bar still short of tension that it suppose to be.
/Skuly
H.Tiger # 2019
N 5.5 sl spi #454
| | | Re: Nacra 5.5 Dolphin striker failed
[Re: rustyhelms]
#199070
12/16/09 05:58 PM 12/16/09 05:58 PM |
Joined: Sep 2007
Posts: 757
japan erice
old hand
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old hand
Joined: Sep 2007
Posts: 757
japan | how were you measuring the tension?
i think normally when tensioning the everything you start with the beam flat, the nut touching the base of the beam and a tight thread running along the bottom of the beam from 1 end to the other
this thread should be touching the beam all the way along if the beam is flat
the nut is then tightened up about 3 turns until the center of the beam has been pushed up about 5mm above thread
that's how i did it anyway
eric e
1982 nacra 5.2 - 2158
2009 weta tri - 294
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