RE: catalina27-talk: Shroud connections to the hull

[windabout]

Absopositively agree Phil - if aint' broke don't break it

--
Dave - artfully dodging
C27 #5212
Windabout
Cape Cod
http://dpbcc.home.comcast.net

 -------------- Original message ----------------------
From: "Phil Agur" <[EMAIL PROTECTED]>
> If we could find a way to tension a wire up near its breaking strength to
> validate it and its terminals were still good you wouldn't want to be any
> where near it. 
> 
>  
> 
> While the full test load a 34' long 3/16" cable would elongate 3.7 inches,
> and if it were to fail would recoil like a razor sharp rubber band slicing
> anything in its path. Add any deflection in the hull (think of it acting
> like a fiberglass bow) and the wire end would be traveling like a bullet if
> it failed.
> 
>  
> 
> I think this one of those situations where the cost of any means of
> non-destructive testing would exceed the replacement cost of the item being
> tested.
> 
>  
> 
> Phil Agur                    s/v Wing Tip
> 
> Commodore,             Call Sign WCW3485
> 
> IC27/270A                   MMSI 366901790 
> 
>  <http://www.catalina27.org> www.catalina27.org      Vessel Doc# 1039809
> 
> -----Original Message-----
> From: catalina27-talk@memberclicks.com
> [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED]
> Sent: Friday, June 16, 2006 6:04 AM
> To: catalina27-talk@memberclicks.com
> Subject: Re: catalina27-talk: Shroud connections to the hull
> 
>  
> 
> Well, Bob, the rigging tension gauges (like the LOOS gauges, for example)
> measure deflection under an exact load--but the load is very much reduced
> from what the rigging might see in a 35 kt wind, and is a mere fraction of
> the ultimate wire strength.  The LOOS gauge is normally used to ensure that
> your standing rigging is tensioned at 10-15% of its breaking strength, and
> it does that by applying a small sideways force and measures the miniscule
> amount that the rigging bends under that force.  This is an indirect way of
> measuring tension...
> 
>  
> 
> Considering that 3/16" SS rope is rated at breaking strengths in the 4000
> lb. range (depends on the construction of the strands), it would be really
> hard to give our shrouds a full-scale test.  (Hang a pickup truck from our
> forestays?  It might get grease on the furled jib... )  Besides, producing
> that much stress on a shroud would only add to the fatigue factor--and as
> Phil pointed out, fatigue can't be observed visually.  There was an anecdote
> in To Engineer Is Human about a pilot flying loops in a small plane that
> wasn't built to fly loops.  He thought because he'd done it before and
> survived that he could continue to do it.  Well, aluminum work-hardens, and
> fatigue builds up when the metal is stressed, making it more and more
> brittle and weak... and eventually, a wing broke off.  Eventually, too, our
> shrouds may fail.
> 
>  
> 
> I have my boat on the hard in my driveway, and the mast and rigging are all
> in separate places about the yard and garage.  I had the opportunity to do a
> VERY thorough rigging check, even though the surveyor had given us a clean
> bill.  I was surprised to find two corroded inner stay fittings and one
> mainstay wire that had a tiny, neat wrap of electrical tape, under the end
> of the spreader cap.  Removing the tape revealed 5 of my 19 strands of
> stainless were broken clean through, and half of the rest look granular and
> crystalline under my microscope.  Also, my backstay has a nicopress sleeve
> installed about ten feet up from the stern fitting, and I'm guessing that
> there is a fracture hidden below that, as well.  I'm biting the bullet and
> replacing all my standing rigging <sigh>.
> 
>  
> 
> Oh--for what it's worth on lifelines: I saw a study (should have kept a
> copy!) done by the Coast Guard or Navy or someone else with authority that
> demonstrated how poorly our lifelines protect us.  It's not the 'leaning
> against the rail' that breaks them--it's the 200 lb. man falling across the
> deck and hitting them suddenly that can produce about 2000 lb. of impact
> force.  Fortunately, I weigh only 184 pounds <grin>.  And I'm making my own
> replacement stanchions and pushpit from 11 ga stainless (.120" thick walls),
> just to help out...
> 
>  
> 
> David Shaddock
> 
> 1977 C27 #3495 Pixie, in Rockford, IL 
> 
> ----- Original Message -----
> From: [EMAIL PROTECTED]
> Date: Thursday, June 15, 2006 20:58
> Subject: Re: catalina27-talk: Shroud connections to the hull
> To: catalina27-talk@memberclicks.com
> 
> > Here's my question: Are sailboats designed to withstand certain 
> > levels of  
> > wind or shroud strength?  
> >  
> > If so, they all one needs to do is create those loads - 
> > statically or  
> > dynamically, to be assured that your boat is "safe" or 
> > not.  We have shroud  tension 
> > gages. Why not use one, while placing the shroud under the 
> > test  load?
> >  
> >  - - - 
> >  
> > I recently had a survey done on my Catalina. The way that the 
> > surveyor  
> > determined that the lifelines were good was to put an impulse 
> > load on the  
> > lifelines with his body and watching the stanchion to deck 
> > connection. Simple,  but 
> > effective.
> >  
> > Bob
> > 
> 
> 

--- Begin Message ---

If we could find a way to tension a wire up near its breaking strength to validate it and its terminals were still good you wouldn’t want to be any where near it.   While the full test load a 34’ long 3/16” cable would elongate 3.7 inches, and if it were to fail would recoil like a razor sharp rubber band slicing anything in its path. Add any deflection in the hull (think of it acting like a fiberglass bow) and the wire end would be traveling like a bullet if it failed.   I think this one of those situations where the cost of any means of non-destructive testing would exceed the replacement cost of the item being tested.   Phil Agur                    s/v Wing Tip Commodore,             Call Sign WCW3485 IC27/270A                   MMSI 366901790 www.catalina27.org      Vessel Doc# 1039809 -----Original Message----- From: catalina27-talk@memberclicks.com [mailto:catalina27-talk@memberclicks.com] On Behalf Of [EMAIL PROTECTED] Sent: Friday, June 16, 2006 6:04 AM To: catalina27-talk@memberclicks.com Subject: Re: catalina27-talk: Shroud connections to the hull   Well, Bob, the rigging tension gauges (like the LOOS gauges, for example) measure deflection under an exact load--but the load is very much reduced from what the rigging might see in a 35 kt wind, and is a mere fraction of the ultimate wire strength.  The LOOS gauge is normally used to ensure that your standing rigging is tensioned at 10-15% of its breaking strength, and it does that by applying a small sideways force and measures the miniscule amount that the rigging bends under that force.  This is an indirect way of measuring tension...   Considering that 3/16" SS rope is rated at breaking strengths in the 4000 lb. range (depends on the construction of the strands), it would be really hard to give our shrouds a full-scale test.  (Hang a pickup truck from our forestays?  It might get grease on the furled jib... )  Besides, producing that much stress on a shroud would only add to the fatigue factor--and as Phil pointed out, fatigue can't be observed visually.  There was an anecdote in To Engineer Is Human about a pilot flying loops in a small plane that wasn't built to fly loops.  He thought because he'd done it before and survived that he could continue to do it.  Well, aluminum work-hardens, and fatigue builds up when the metal is stressed, making it more and more brittle and weak... and eventually, a wing broke off.  Eventually, too, our shrouds may fail.   I have my boat on the hard in my driveway, and the mast and rigging are all in separate places about the yard and garage.  I had the opportunity to do a VERY thorough rigging check, even though the surveyor had given us a clean bill.  I was surprised to find two corroded inner stay fittings and one mainstay wire that had a tiny, neat wrap of electrical tape, under the end of the spreader cap.  Removing the tape revealed 5 of my 19 strands of stainless were broken clean through, and half of the rest look granular and crystalline under my microscope.  Also, my backstay has a nicopress sleeve installed about ten feet up from the stern fitting, and I'm guessing that there is a fracture hidden below that, as well.  I'm biting the bullet and replacing all my standing rigging <sigh>.   Oh--for what it's worth on lifelines: I saw a study (should have kept a copy!) done by the Coast Guard or Navy or someone else with authority that demonstrated how poorly our lifelines protect us.  It's not the 'leaning against the rail' that breaks them--it's the 200 lb. man falling across the deck and hitting them suddenly that can produce about 2000 lb. of impact force.  Fortunately, I weigh only 184 pounds <grin>.  And I'm making my own replacement stanchions and pushpit from 11 ga stainless (.120" thick walls), just to help out...   David Shaddock 1977 C27 #3495 Pixie, in Rockford, IL  ----- Original Message ----- From: [EMAIL PROTECTED] Date: Thursday, June 15, 2006 20:58 Subject: Re: catalina27-talk: Shroud connections to the hull To: catalina27-talk@memberclicks.com > Here's my question: Are sailboats designed to withstand certain > levels of  > wind or shroud strength?  >   > If so, they all one needs to do is create those loads - > statically or  > dynamically, to be assured that your boat is "safe" or > not.  We have shroud  tension > gages. Why not use one, while placing the shroud under the > test  load? >   >  - - - >   > I recently had a survey done on my Catalina. The way that the > surveyor  > determined that the lifelines were good was to put an impulse > load on the  > lifelines with his body and watching the stanchion to deck > connection. Simple,  but > effective. >   > Bob >

--- End Message ---