Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 04-09-2012, 19:14   #1
Registered User
 
sharpey's Avatar

Join Date: Aug 2011
Location: Singapore
Boat: Moody 376
Posts: 135
Hull Sagging on the Stands? Pics Enclosed

Hey folks,

This next "challenge" has started to weigh on my mind a little...

Since removing a substantial amount of the hull below the waterline (blistering) and then removing the mast (new rigging on the way), and finally removing the cabin sole to start cleaning the bilge... I've noticed some cracks in the support members nearest the mast compression post.





You can see the hull & cradle here...




The thing is, I need to have the hull re-glassed, and I'm worried that if it has sagged then when it goes back in the water and wants to sit back into it's natural shape, the new glass on the hull will perhaps prevent this, or cause yet more cracks in the new glass!

The tricky part is, I'm not sure if these cracks are new or not, they do look to have dirt in them you see. Also worthy of mention is a crack in the hull above the front edge of the keel (not pictured yet) which may have resulted from a previous impact (this crack was spotted soon after we came out of the water, and definitely doesn't look new)...

Any thoughts?

There are loads of ribs built into the hull, it does seem very solidly constucted. Boat is 37' and weighs around 16,000lbs.

I was thinking about putting the mast back up (one I've checked the base of the compression post) and tightening up the new rig... the armchair thinking here being that it might help to reduce the sag?

Cheers,

James
__________________

__________________
sharpey is offline   Reply With Quote
Old 04-09-2012, 19:19   #2
Registered User
 
sharpey's Avatar

Join Date: Aug 2011
Location: Singapore
Boat: Moody 376
Posts: 135
Re: Hull sagging on the stands? Pics enclosed

Again, this is all on the assumption that the hull is sagging a bit... and that the cracks are not the result of said previous impact....

Mind you, there is about a 1cm gap between the top of the companionway stairs and where they are supposed to screw in... and I can't remember if it was this way when she was in the water (that was back in March!)
__________________

__________________
sharpey is offline   Reply With Quote
Old 04-09-2012, 19:27   #3
Moderator
 
sailorchic34's Avatar

Cruisers Forum Supporter

Join Date: Feb 2011
Location: SF Bay Area
Boat: Islander 34
Posts: 4,815
Re: Hull sagging on the stands? Pics enclosed

To me zooming in, it looks like the cracks are in the tabbing holding the block for the compression post to the hull. The block is cracked too and needs to be replaced. Don't think the hull would be sagging
__________________
sailorchic34 is offline   Reply With Quote
Old 04-09-2012, 19:39   #4
Moderator Emeritus
 
Ex-Calif's Avatar

Cruisers Forum Supporter

Join Date: May 2007
Location: Singapore
Boat: Maxi 77 - Relax Lah!
Posts: 11,514
Images: 4
Re: Hull Sagging on the Stands? Pics Enclosed

Damn - That's not good.

My observation based on how your cradle is set up is that the boat is sitting on the keel. The pads are only supporting laterally so you got 16,000# sitting on the fin.

This would tend to push the keel up and if anything the "sides" sag. I know you've removed a fair amount of bottom material and wonder if this has anything to do with it.
__________________
Relax Lah! is For Sale <--- Click
Click--> Custom CF Google Search or CF Rules
You're gonna need a bigger boat... - Martin Brody
Ex-Calif is offline   Reply With Quote
Old 04-09-2012, 19:44   #5
Moderator Emeritus
 
Ex-Calif's Avatar

Cruisers Forum Supporter

Join Date: May 2007
Location: Singapore
Boat: Maxi 77 - Relax Lah!
Posts: 11,514
Images: 4
Re: Hull Sagging on the Stands? Pics Enclosed

Taking another look -

Put feeler gauges in the cracks
Jack the forward and stern supports to relieve weight on the keel
If the cracks close up the feeler gauges will bind and the hull is flexing
While jacked up lower the pads and get them underneath the hull to take some weight off the keel

You'll want to weigh this idea against the potential of further damage caused by jerking the hull around.

Then determine next steps.
__________________
Relax Lah! is For Sale <--- Click
Click--> Custom CF Google Search or CF Rules
You're gonna need a bigger boat... - Martin Brody
Ex-Calif is offline   Reply With Quote
Old 04-09-2012, 20:01   #6
Registered User

Join Date: Dec 2008
Location: ontario canada
Boat: grampian 26
Posts: 1,743
Re: Hull Sagging on the Stands? Pics Enclosed

Check those other cross beams for cracks. The boat may have been bumped hard on the keel. Check the keel over for any evidence of a hard grounding.
__________________
perchance is offline   Reply With Quote
Old 04-09-2012, 20:03   #7
Registered User

Join Date: Dec 2008
Location: ontario canada
Boat: grampian 26
Posts: 1,743
Re: Hull Sagging on the Stands? Pics Enclosed

Quote:
Originally Posted by Ex-Calif View Post
Damn - That's not good.

My observation based on how your cradle is set up is that the boat is sitting on the keel. The pads are only supporting laterally so you got 16,000# sitting on the fin.

This would tend to push the keel up and if anything the "sides" sag. I know you've removed a fair amount of bottom material and wonder if this has anything to do with it.
That's how they do it on this side of the pond.
__________________
perchance is offline   Reply With Quote
Old 04-09-2012, 20:10   #8
Registered User

Join Date: May 2008
Posts: 1,971
Re: Hull Sagging on the Stands? Pics Enclosed

How deep are those cracks? This could be just cosmetic crazing in the gel coat or paint on the inside of the bilge. Fiberglass isn't white. Try chipping some off and see if you can see any cracks in the glass underneath.
__________________
CarlF is offline   Reply With Quote
Old 04-09-2012, 20:22   #9
Registered User
 
Nemo55's Avatar

Join Date: Feb 2012
Location: Punta Banda, Ensenada. and Canada
Boat: 28Ft Piver Encore, Tri-Maran, Anchored in San Diego.
Posts: 728
Send a message via Skype™ to Nemo55
Re: Hull Sagging on the Stands? Pics Enclosed

I'd go with what Ex-Calif has suggested, thats an awfull lot of weight on that keel, especially if you have been removing material from the innards of the boat which may have been at least partially supportive in structure.
My first boat was jacked and held by five points plus the keel (a Cal 28) not just balanced like yours is.
Just my opinion, but i dont like the looks of your support system.
__________________
"The Truth Shall set you Free....But First it will Piss You Off"

http://nemo1955.blogspot.ca/
Nemo55 is offline   Reply With Quote
Old 05-09-2012, 04:53   #10
Registered User
 
sharpey's Avatar

Join Date: Aug 2011
Location: Singapore
Boat: Moody 376
Posts: 135
Re: Hull Sagging on the Stands? Pics Enclosed

Thanks all for taking the time to reply. I think the feelers gauge idea is worth a go. I'll have a chat with the folks up at the club about doing a bit of propping up.

I'm somewhat reassured by the fact that I've got rather a long and bulbous keel, rather than a thin deep fin. This should mean the load is a tad better supported (at least as far as my armchair logic goes on this).

I kind of get the theory that the hull is essentially flexing on its support ribs (due to the weight that is normally supported by the water being essentially unsupported at the moment). I can now also see how the kind of support I see other boats online that are on the hard having entails numerous supports all around (even if they do look rather flimsy)..to better support the weight of the hull.
__________________
sharpey is offline   Reply With Quote
Old 05-09-2012, 05:14   #11
Senior Cruiser
 
Blue Stocking's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: St. Georges, Bda
Boat: Rhodes Reliant 41ft
Posts: 4,117
Re: Hull Sagging on the Stands? Pics Enclosed

I'm surprised there are no bow and counter support jacks, especially with this diet program you are applying to the hull.
__________________
so many projects--so little time !!
Blue Stocking is offline   Reply With Quote
Old 05-09-2012, 05:19   #12
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,586
Images: 240
Re: Hull Sagging on the Stands? Pics Enclosed

The full weight of the boat should sit on the keel (even a fin), with the jack stands merely providing balance.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Old 05-09-2012, 05:26   #13
Registered User
 
sharpey's Avatar

Join Date: Aug 2011
Location: Singapore
Boat: Moody 376
Posts: 135
Re: Hull Sagging on the Stands? Pics Enclosed

There is a jack on the bow & one on the stern... Hard to see through the plastic sheeting.
__________________
sharpey is offline   Reply With Quote
Old 05-09-2012, 05:26   #14
Senior Cruiser
 
atoll's Avatar

Cruisers Forum Supporter

Join Date: Mar 2010
Location: gettin naughty on the beach in cornwall
Boat: 63 custom alloy sloop,macwester26,prout snowgoose 37 elite catamaran!
Posts: 9,312
Images: 75
Re: Hull Sagging on the Stands? Pics Enclosed

i would seriously think about lifting the boat and prop it up conventialy with chocks and wedges,this supports the hull,whilst the weight is taken on the keel.

the props are removed one at a time when relaminating,and replaced once the resin has cured.
__________________
my catamaran building project updates http://www.cruisersforum.com/forums/...36#post2502136
atoll is offline   Reply With Quote
Old 05-09-2012, 05:31   #15
Registered User
 
Jaxxiam's Avatar

Join Date: Feb 2011
Location: 35 46' 14" N 83 56' 50" W
Posts: 97
Re: Hull Sagging on the Stands? Pics Enclosed

My concern is how deep are the cracks.
The feeler gauge should tell a lot. I would be inclined to grind into the crack (only after the hull is supported) to find out if the athwartship stringer needs to be replaced, if it only a suface crack just reglass, sand and paint it. But that's just me.
__________________

__________________
Jaxxiam is offline   Reply With Quote
Reply

Tags
hull

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 01:17.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.