Hello Stress Engineers

 Need some opinion.

On 8/25 we pulled our boat to prepare for the race inspected the hull and bottom - no issues.

On 9/19 a boat hit us straight on.  The force was mostly on the top side of boat, the bow pulpit was ripped off and the fiberglass broken on deck.   The carbon fiber spinnaker pole which sticks out a bit to starboard was snapped where it met the pulpit front leg.  When we pulled the boat, we noticed a cracks on front left and right side of hull near the boot stripe.   Any structural or stress Engineers out there who could explain to the insurance company why these cracks were produced?  They refuse to pay for repair.  So far I have not received $.01 for the insurance company of boat who hit us.  Thanks for the analysis.

Here is a quick video of impact:



Here are photos of the area where cracks were found:

A2.PNG
A1.PNG


 

See Level

Working to overcome my inner peace
I'm no engineer but you can see your whole bow flex aft in the collision, maybe it fractured at hinge point of the flex at the lower end hard pointed by the v shape.

 
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longy

Overlord of Anarchy
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San Diego
  Stepping thru the vid slowly - there is no contact down by the boot stripe. Both boats have flare in the bows, first contact was bow pulpits, then pulpit against H/S, then protruding pole, then it's obscured, but may have had hull to hull contact about 5-8" down from sheer on your boat. Your bow is by far the strongest part of your boat due to the angles as the hull pinches out.

   So very unlikely the crash was solely responsible for the cracks. Just how big were they before the grinder attach? And have they disappeared in the ground out saucers shown?

 

Rasputin22

Rasputin22
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Better to just take up drinking in the evening like the rest of NO. ADD was living up to its name, not paying attention! Good to see that expensive MacGregor escape the carnage.

 
  Stepping thru the vid slowly - there is no contact down by the boot stripe. Both boats have flare in the bows, first contact was bow pulpits, then pulpit against H/S, then protruding pole, then it's obscured, but may have had hull to hull contact about 5-8" down from sheer on your boat. Your bow is by far the strongest part of your boat due to the angles as the hull pinches out.

   So very unlikely the crash was solely responsible for the cracks. Just how big were they before the grinder attach? And have they disappeared in the ground out saucers shown?
Thank You, the very odd thing about these cracks is they were not in existence before the impact.  How could any impact cause cracks on both sides through the glass?  The glass pushed the gelcoat out.  If there was impact from an object the crack would have shown gelcoat pushed in not out.  The size of crack is only 6 inches on one side, 3 on the other.

 

longy

Overlord of Anarchy
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San Diego
   Sounds more like there was a bubble under the gel coat. The 'whole bow' is not flexing from that small impact.  What layers were visible as the cracks were ground out? Is there structural glass showing at the bottom of the saucers or is it still mat?

 
   Sounds more like there was a bubble under the gel coat. The 'whole bow' is not flexing from that small impact.  What layers were visible as the cracks were ground out? Is there structural glass showing at the bottom of the saucers or is it still mat?
No bubbles noted in gelcoat.  Cracks visible through paint , primer gelcoat and glass. 

 

crankcall

Super Anarchist
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I know nothing about engineering, but I race a lot and that green boat should be uninvited from the fleet till he spends some time in an Opti.  They have very square bows for bunting into things.

 

Steam Flyer

Sophisticated Yet Humble
44,302
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I'm no engineer but you can see your whole bow flex aft in the collision, maybe it fractured at hinge point of the flex at the lower end hard pointed by the v shape.
This is "spot on".  Thank You.  If you slow the video down you can see the spinnaker pole flex too around 42-44 seconds.
I did n't watch the video but check where the fwd bulkhead is set in. Not just a hinge point but will carry stress from impact point to another location.

FB- Doug

 

ctutmark

Super Anarchist
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is there any sort of bulkhead (anchor locker?)  up there? If so the force on the pulpit could have pushed the deck down, forcing the bulkhead down and it found a weak spot.  Purely a theory

 

longy

Overlord of Anarchy
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San Diego
frant said:
Whose side are you on. Even if there was a latent defect that has been hidden for 20 odd years that this prang has brought to the surface it is still part of collision damage and should be repaired and paid for by greenboat.
There's no question about that. The q is how did an area well removed from the point of impact get damaged. So far an interior bulkhead transferring the force down is the best hypothesis.

 
frant said:
Whose side are you on. Even if there was a latent defect that has been hidden for 20 odd years that this prang has brought to the surface it is still part of collision damage and should be repaired and paid for by greenboat.


There is a bulk head in this area.  I will measure tomorrow to see if the cracks align with the bulkhead above.  Great idea.
This isn't your typical old boat.  It was recently restored.

A4.jpg


 

Hitchhiker

Hoopy Frood
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Protest filed? Should go in the J's favour.

J-30 vs Wavelength 24? Should go in the J's favour.

RC work for start and recording of same? Should go in the J's favour.

Start winner? Should go in the MacGregors favour.

 

Al Paca

Super Anarchist
2,021
575
El Lay
Those cracks are from a wave hitting the front of the boat. Now I know that it's a chance in a million, but still, the front might very well fall off.

 

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