Front Crossbar Collapse :: Catamaran Sailboats at TheBeachcats.com

Front Crossbar Collapse

leeboweffect

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Posted: Jun 30, 2017 - 04:15 PM

This is why you check your dolphin striker tension (Hobie 14, 16 etc.) and inspect for cracks and/or signs of metal fatigue on the bottom side of the front crossbar (where the post goes through) at least once a month. On the legacy Nacras also make certain to adjust the prebend between 1/4-3/8".

https://www.youtube.com/watch?v=ZMerznCoKdc&feature=youtu.be

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Hobie 16 (3 formerly)
MacGregor 25 (formerly)
Chrysler Dagger 14 (formerly)
NACRA 5.0 (currently)
High Point, NC
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tnell

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Posted: Jun 30, 2017 - 04:59 PM

I never knew about the pre-bend. The manual I have references tension (it says the DS shouldn't move more than 1/4 inch) but I didn't see anything about pre-bend on the beam. I will have to check mine. Where did you get this info from on the pre-bend? I'm not challenging it, just trying to learn from it.

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Tim
Collierville (Memphis), TN
Supercat 15--sold :(
Hobie monocat--given
Vanguard 15--traded for...
Nacra 4.5--sold
Nacra 5.7
Hobie 14–sold to make room for...
Supercat 17–sold
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leeboweffect

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Posted: Jun 30, 2017 - 05:41 PM

tnellWhere did you get this info from on the pre-bend? I'm not challenging it, just trying to learn from it.

I'm not sure that it's in the manuals. I learned about it on here and trading PM's with a guy who rebuilt a 5.5 Uni, sierracat? Then verified it from several others, edchris177, wolfman etc..

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Hobie 16 (3 formerly)
MacGregor 25 (formerly)
Chrysler Dagger 14 (formerly)
NACRA 5.0 (currently)
High Point, NC
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tnell

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Posted: Jun 30, 2017 - 05:55 PM

Well I'll still check mine. I need to replace the bolt anyway but I dont want to go through the hassle others have had with it being frozen. Next time my mast down I'm gonna see if I can get any movement on the bolt/sleeve. Then if it's free I'll replace it all in one shot. I guess if the DS "flex" is correct, then the prebend would also have to be corrrect since they're both dependent on the bolt pressure.

Edited by tnell on Jun 30, 2017 - 05:59 PM.

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Tim
Collierville (Memphis), TN
Supercat 15--sold :(
Hobie monocat--given
Vanguard 15--traded for...
Nacra 4.5--sold
Nacra 5.7
Hobie 14–sold to make room for...
Supercat 17–sold
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nohuhu

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Posts: 274
Posted: Jun 30, 2017 - 11:48 PM

Oh man- that's great! What DID we do before GoPros and YouTube?

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Prindle 18
96734
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martyr

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Posted: Jul 01, 2017 - 12:59 AM

Can someone please post a highlighted link to that video, I cannot cut and paste on my phone. Yeah, it's a problem.

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Marty
1984 Hobie 16 Redline Yellow Nationals, "Yellow Fever"
Opelika, Al / Lake Martin
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nacra55

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Posted: Jul 01, 2017 - 02:37 AM

https://www.youtube.com/w…znCoKdc&feature=youtu.be

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Ron
Nacra F18
Reservoir Sailing Assn.
Brandon, Mississippi
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MN3

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Posted: Jul 01, 2017 - 07:37 AM

Quotenspect for cracks and/or signs of metal fatigue on the bottom side of the front crossbar (where the post goes through)

from the video looks like the failure originated at the connection on the bow , you can see it wobbling pre beam failure
martyr

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Posted: Jul 01, 2017 - 09:41 AM

Thanks Ron. Geez, that looked really bad, the thing folded up like a piece of paper!!!

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Marty
1984 Hobie 16 Redline Yellow Nationals, "Yellow Fever"
Opelika, Al / Lake Martin
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nohuhu

Rank: Mate

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Posted: Jul 01, 2017 - 02:59 PM

MN3
Quotenspect for cracks and/or signs of metal fatigue on the bottom side of the front crossbar (where the post goes through)

from the video looks like the failure originated at the connection on the bow , you can see it wobbling pre beam failure
Good eye. I was about to mention the same thing.

The wobbling was there on the port bow on both tacks. As if some loose component was stretching that side constantly and led to a connection failure. There appeared to be plenty of prebend, so the folding may have been collateral damage. Wish the GoPro had been on the other bow...

Not disputing the moral of the story though, and it doesn't spoil my enjoyment of that clip, one bit. Thanks Leebow.

Edited by nohuhu on Jul 01, 2017 - 11:01 AM.

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Prindle 18
96734
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Dogboy

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Posted: Jul 01, 2017 - 09:17 PM

That's pretty darn ugly.

I think those Hobie 15s are really intended for kids/youth and from the looks of the video, two full grown men were sailing the boat in strong conditions, so I suspect the thing was overloaded. You can see the front crossbar flexing/inverting in the video and the whole rig is leaning way over. That should have been an indication that something wasn't right. Not so sure that failure was caused by a loose dolphin striker. I think it was probably just too much weight on board for the amount of wind.

sm
martyr

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Posted: Jul 01, 2017 - 09:23 PM

The DS doesn't seem to even be attached on the port side, lots of shaking up and down.

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Marty
1984 Hobie 16 Redline Yellow Nationals, "Yellow Fever"
Opelika, Al / Lake Martin
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Dogboy

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Posted: Jul 02, 2017 - 07:25 AM

martyrThe DS doesn't seem to even be attached on the port side, lots of shaking up and down.

You're right! I originally viewed the video on a phone and couldn't see that. On a computer screen, it's clear that the dolphin striker rod on the port side isn't even attached. Still pretty scary to see that failure though. If one of the guys had gotten wrapped up in the tramp when the boat turned into a taco, he very easily could have been killed.

sm
leeboweffect

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Posted: Jul 02, 2017 - 10:35 AM

MN3from the video looks like the failure originated at the connection on the bow , you can see it wobbling pre beam failure

Yes, the dolphin striker is totally loose on the port side thus the dolphin striker jiggling and clank, clank, clank you hear in the video. With the dolphin striker this loose, the front crossbar is taking all the load. That's why I commented to check the dolphin striker tension monthly. On the Hobies with this type of dolphin striker (a round rod threaded at each end) it is tensioned with a nut on each end which assembles through holes in the corner castings. Note that in this photo the nut is missing.

As the Hobie 16's front crossbar has an arch prebent in to it there is really no need to tension the dolphin striker nuts such that you are further arching the crossbar, but they do need to be snugged up so that sitting on the trailer, mast down, there is no freedom of movement.

The crossbar taking all the load is the primary failure mode here. Had the dolphin striker been tensioned properly it could have been avoided.

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Hobie 16 (3 formerly)
MacGregor 25 (formerly)
Chrysler Dagger 14 (formerly)
NACRA 5.0 (currently)
High Point, NC
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martyr

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Posted: Jul 02, 2017 - 11:28 AM

Good info.

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Marty
1984 Hobie 16 Redline Yellow Nationals, "Yellow Fever"
Opelika, Al / Lake Martin
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Andinista

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Posted: Jul 03, 2017 - 11:14 AM

The beam actually breaks at 0:10 on the video, a crack appears and from that point the beam is shaped like the M of macdonalds..
Andinista

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Posted: Jul 03, 2017 - 11:14 AM

The beam actually breaks at 0:10 on the video, a crack appears and from that point the beam is shaped like the M of macdonalds..
Andinista

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Posted: Jul 03, 2017 - 11:32 AM

The dolphin striker is definitely loose at the port side and the cause of the incident. Maybe the nut got off while sailing, compare how low is the port end of the rod at 0:08 respect to the beginning of the video. Look at the connection of the rod and the post at 0:08, the rod is offset to the right.
MN3

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Posted: Jul 03, 2017 - 04:50 PM

QuoteI think those Hobie 15s are really intended for kids/youth and from the looks of the video, two full grown men were sailing the boat in strong conditions, so I suspect the thing was overloaded.

I thought that too but couldn't tell if they were adults or just big kids on my phone - clearly adult size

I am shocked to see the specs on this boat:
Crew: 3
Length: 4.95 m / 16' 4"
Beam: 2.26 m / 7' 5"
Capacity: 320 kg / 705 lbs
Weight: 155 kg / 342 lbs

QuoteStill pretty scary to see that failure though. If one of the guys had gotten wrapped up in the tramp when the boat turned into a taco, he very easily could have been killed.

+1

Quotein the video and the whole rig is leaning way over.

I saw that too - but thought it was the gopro fisheye lense
MN3

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Posted: Jul 04, 2017 - 01:34 PM

I am real glad this thread got me under my cat today:

my 5.5 is now in dry dock

Edited by MN3 on Jul 05, 2017 - 08:57 AM.