Catamaran News

Classified Ads

Forums

Calendar

Contact Us

TheBeachcats.com Logo
Notifications
Clear all

Front Beam prebend

15 Posts
5 Users
0 Reactions
3,252 Views
Edward Hilliard
(@Edchris177)
Posts: 2531
Captain
Topic starter
 

I'm sure I read about pre loading the front beam,on a Nacra 5.7, by adjusting the DS bottom nut.
I know how to do it, by stretching a masons line along the bottom of the beam & measuring displacement at the DT, but how much do you bend it?
I can't find the photo, or am I hallucinating?

E C Hilliard

Nacra 5.7
Bombardier Invitation

 
Posted : May 4, 2010 2:18 pm
Philip
(@p-m)
Posts: 916
Chief
 

Ed,
No need for the masons line. Just hand tighten the nut with no bend and then add 3/8" to the threaded rod. So easy a cave man . . .

Philip

 
Posted : May 4, 2010 5:31 pm
Edward Hilliard
(@Edchris177)
Posts: 2531
Captain
Topic starter
 

Thanks Philip, I didn't know how critical that setting was, obviously it falls into the 'bout there category.

E C Hilliard

Nacra 5.7
Bombardier Invitation

 
Posted : May 5, 2010 2:11 am
David Bonin
(@Wolfman)
Posts: 1555
Master Chief
 

Note to everyone, don't try to tighten more than that!! I wasn't thinking and did that over the weekend, managed to strip the dolphin striker and the bolt. Then tried to undo it and really made a mess (should have left it where it was). Hey EC you happen to have another one of those kicking around... 🙂

Dave Bonin
1981 Nacra 5.2

 
Posted : May 16, 2010 2:10 pm
Philip
(@p-m)
Posts: 916
Chief
 

A load from the beam didn't cause the DS rod to strip. More likely the compression tube was corroded to the rod. If your boat has the original alum V bar, you might want to look carefully where the attachment bolts it to the beam for galvanic corrosion. Failure can happen here due to age and the results are catastrophic.

Philip

 
Posted : May 16, 2010 3:14 pm
David Bonin
(@Wolfman)
Posts: 1555
Master Chief
 

Nope, I stripped it by trying to put too much load on... it was a new rod that I was putting on. 🙂 I had just finished cutting the old rod off (that I bent last year) and was putting the new rod on when I screwed it up. Wish I could claim your reason, but I can't darn it all. $68 plus shipping mistake (yep, I'm a moron).

Now I have one on order from Murray's, hopefully it will get here before next weekend.

Now here's a stupid question, I jarred the compression sleeve loose so it's isn't lined up with the holes. Is there an easy way to realign it?

D.

Dave Bonin
1981 Nacra 5.2

 
Posted : May 16, 2010 3:51 pm
Philip
(@p-m)
Posts: 916
Chief
 

I just tape it to a stick, or batten. Done.

The stripping thing . . . weird. I can collapse/break a beam, break the rod, etc. by over-adjusting the nut. Something ain't right, bro.

Philip

 
Posted : May 16, 2010 4:21 pm
David Bonin
(@Wolfman)
Posts: 1555
Master Chief
 

Yeah, might have been a flaw in the threads or a bad batch of stainless. No idea. Suffice to say I'm going to pay more attention this time.

edited by: Wolfman, May 16, 2010 - 10:05 PM

Dave Bonin
1981 Nacra 5.2

 
Posted : May 16, 2010 5:05 pm
eragon
(@eragon)
Posts: 22
Lubber
 

any stainless bolts must have lube (nickel anti seize is best) before putting any tension on them or they will bind up and resist any adjustment - take note all sailers

 
Posted : May 16, 2010 9:34 pm
erice
(@erice)
Posts: 671
Chief
 

when i did the pre-bend on my 5.2 i worked it out to be about 5mm

about half the 3/8" that some have mentioned....

1982 nacra 5.2
2009 weta

 
Posted : May 17, 2010 1:08 am
David Bonin
(@Wolfman)
Posts: 1555
Master Chief
 

That would explain it! That's what I did wrong! Forgot to grease the damn thing, knew it was something simple.

Dave Bonin
1981 Nacra 5.2

 
Posted : May 17, 2010 3:34 am
David Bonin
(@Wolfman)
Posts: 1555
Master Chief
 

Thank goodness for Murrays Marine! 1 dolphinstriker rod and hardware, 1 day delivery from California to Winnipeg, Manitoba, Canada! Unbelievable! I will be striking dolphins all weekend now. 🙂

Dave Bonin
1981 Nacra 5.2

 
Posted : May 18, 2010 1:34 pm
Edward Hilliard
(@Edchris177)
Posts: 2531
Captain
Topic starter
 

Sorry Dave, I only made one of 'em. When I chnaged mine, I realized it would be way easier to push a stick through the tube, as I withdrew the rod, in order to prevent dropping it in the beam. I think it would be pretty easy to tape it to a stick, but you would need two people. Your arms are not long enough to manipulate the stick, & look to see if it is lined up.
I don't buy needing lube on the threads. We used a lot of SS bolts/fitting in a mill I worked at many years ago.(West Coast Vancouver Island salt environment)The mill wrights never used anything on them.
I was concerned the threads of one nut might have been compromised, so I replaced them when I changed my rod. As an experiment we double nutted the cut piece of rod, put it in a large vice, then tried to twist the old nut past some bent threads. Using a 5/8 box end wrench, almost 18" long, it took all the torque I could apply before the nut/rod stripped. The nut was actually hot from the friction. I think there was a bad thread on the rod, or some filings got caught in there, or the rod was not straight. Check for trueness by rolling the rod on a glass table top, it will "click" if it isn't true. You shouldn't be able to strip it without applying a good deal of force, that is a pretty heavy duty rod.

E C Hilliard

Nacra 5.7
Bombardier Invitation

 
Posted : May 18, 2010 2:56 pm
David Bonin
(@Wolfman)
Posts: 1555
Master Chief
 

No problems I'm sailing this weekend, that's what counts! I'll probably never know exactly what happened, but live and learn eh.

Dave Bonin
1981 Nacra 5.2

 
Posted : May 18, 2010 3:31 pm
eragon
(@eragon)
Posts: 22
Lubber
 

happy sailing wolfman great pic here

 
Posted : May 18, 2010 4:15 pm