Reply
 
Thread Tools Search this Thread Display Modes
 
Old 08-29-2018, 09:36 PM   #1
Veteran Member
 
schrater's Avatar
 
City: Vancouver, WA
Country: USA
Vessel Name: Matilda
Vessel Model: Ponderosa (CHB) 35' Sundeck
Join Date: Sep 2016
Posts: 76
Stringer debate

A common check during surveys of older boats is whether there are dead or “wet” spots in the fiberglass stringers. Tapping on them can indicate if rot has entered. This can be a major repair job and can often knock down the asking price of the boat quite a bit.

But is this really a big concern? Are there many real-world examples of stringers giving way? I have heard credible sources say that the strength of a fiberglass stringer comes from its box design and that it would be just as strong if it was hollow. The wood interior was only there to help form its initial shape and structure.

Is the wet stringer test more than just superstition?
__________________
Advertisement

schrater is offline   Reply With Quote
Old 08-29-2018, 10:17 PM   #2
Guru
 
HopCar's Avatar
 
City: Miami Florida
Vessel Name: Possum
Vessel Model: Ellis 28
Join Date: Aug 2011
Posts: 4,127
I know of boats with foam filled stringers that get their strength from the thick glass on it. My guess is that if the builder put wood in it, he’s counting on the wood for most of the strength. The glass is just there to keep it dry.
__________________

__________________
Parks Masterson
HopCar is offline   Reply With Quote
Old 08-30-2018, 02:04 AM   #3
Senior Member
 
kapnd's Avatar
 
City: hawaii
Country: usa
Vessel Name: #31
Vessel Model: ex-Navy MUB 50 fish/cruise
Join Date: Aug 2013
Posts: 487
The original calculations that the boat was built on most certainly factored in the wood as a substantial portion of the stringer’s strength.
For the stringer to remain “just as strong” after the wood rots, it would need to be very heavily glassed indeed, as the long flat sides without the benefit of being bonded to the core will be pretty flimsy, the taller they are, the weaker.
A stronger “stand alone” shape would more resemble an I, C (channel), hat, or inverted U shape.
__________________
You can lead a horse to water,
But you can't make him ski...
kapnd is offline   Reply With Quote
Old 08-30-2018, 05:26 AM   #4
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 18,667
You just fon't know unless you talk to the manufacturer/designer.

I have seen where the eood mattered, and where it didnt.

If I had to guess, on larger boats, say over 30 the eood was structural and under 30 it wadnt structural or ultimately it didnt matter.

But thats a gross generalization and I wouldnt bet the ranch on it.

My dock neighbor on a 32 older Pacemaker found 2 large cracks in his stringers this year, he chose to fix snd not even drop thd boat in the water.
psneeld is offline   Reply With Quote
Old 08-30-2018, 05:58 AM   #5
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in Crisfield, MD
Country: USA
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 6,706
My Cherubini has both foam core and wood core stringers. The engine bed stringers are wood cored, fiberglassed in, and then a heavy steel plate is bolted through the plate and fiberglass into the wood. I have no doubt that even though the fiberglass is thick, the wood is structural strength in those 2 stringers. The foam cored stringers obviously achieve all their strength from the fiberglass.

Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
O C Diver is offline   Reply With Quote
Old 08-30-2018, 06:08 AM   #6
Senior Member
 
Westiculo's Avatar
 
City: Boston
Country: US
Vessel Name: Rose Mary
Vessel Model: 42 Grand Banks Motoryacht - 1985
Join Date: Feb 2017
Posts: 199
Agreed with everyone - depends on the make of the boat. I only have experience with two. In my grand banks, the stringers are foam filled so all strength is from the glass. In a Marine Trader I looked at, much of the strength was from the wood, and it was all but rotted out. The hull was totally compromised.
Westiculo is offline   Reply With Quote
Old 08-30-2018, 07:52 AM   #7
Senior Member
 
Datenight's Avatar
 
City: Noank, CT
Country: USA
Vessel Name: Datenight
Join Date: Jan 2008
Posts: 490
I never trusted the stringers on the old boat a Sunkyung Marine 37' sedan. After about 12 years of ownership I cut out the old stringers and fabricated new. The old were glass over plywood forms. The glass was good but tapping on them indicated the wood was gone.

Removed the generator and fuel tanks. One of the tanks needed repair which I covered here a while ago. With the way clear I laid the sawsall on it's side and cut out the stringers and tank supports. Then ground everything clean. As I lifted out the old supports the rotted wood fell out.

I made new out of plywood saturating each layer before it was screwed and glued together. The stringers were bonded in place then glassed. The solid wood is way overkill but I made then the same thickness as the original hollow units. I am sure I could have made them half the thickness and still have been plenty strong.

Rob
Attached Thumbnails
Click image for larger version

Name:	Laz.jpg
Views:	117
Size:	115.7 KB
ID:	80296   Click image for larger version

Name:	Stringers Removed 2008 006.jpg
Views:	60
Size:	146.8 KB
ID:	80297   Click image for larger version

Name:	Fabricating Stringers 2008 013.jpg
Views:	57
Size:	185.7 KB
ID:	80298   Click image for larger version

Name:	Old Stringers.jpg
Views:	56
Size:	200.4 KB
ID:	80299  
__________________
North Pacific 39
Datenight is offline   Reply With Quote
Old 08-30-2018, 07:56 AM   #8
Senior Member
 
Datenight's Avatar
 
City: Noank, CT
Country: USA
Vessel Name: Datenight
Join Date: Jan 2008
Posts: 490
Maybe I should have posted on the Rot Porn thread!

Rob
__________________
North Pacific 39
Datenight is offline   Reply With Quote
Old 08-30-2018, 08:30 AM   #9
Senior Member
 
City: Tampa, FL
Country: USA
Join Date: Nov 2013
Posts: 400
Of course, everyone is giving you theory, while what you asked for were real-world examples. So, yes, I've seen a boat where the stringers gave way. It was first noticed as a vibration that kept getting worse and worse. Inspection revealed that the engine was crooked. Both stringers had rot. One bad enough that it was no longer supporting the engine mount adequately.


So, again, yes, they can give way if the rot gets bad enough.
denverd0n is offline   Reply With Quote
Old 08-30-2018, 10:04 AM   #10
Guru
 
foggysail's Avatar
 
City: Ashland, MA
Country: United States
Vessel Model: 1990 Silverton 40 aftcabin
Join Date: Jul 2016
Posts: 983
Quote:
Originally Posted by Datenight View Post
I never trusted the stringers on the old boat a Sunkyung Marine 37' sedan. After about 12 years of ownership I cut out the old stringers and fabricated new. The old were glass over plywood forms. The glass was good but tapping on them indicated the wood was gone.

Removed the generator and fuel tanks. One of the tanks needed repair which I covered here a while ago. With the way clear I laid the sawsall on it's side and cut out the stringers and tank supports. Then ground everything clean. As I lifted out the old supports the rotted wood fell out.

I made new out of plywood saturating each layer before it was screwed and glued together. The stringers were bonded in place then glassed. The solid wood is way overkill but I made then the same thickness as the original hollow units. I am sure I could have made them half the thickness and still have been plenty strong.

Rob
STRONG!!!! WOW, about 3” thick? Your pictures indicate you did a fine job repairing your boat!!!
foggysail is offline   Reply With Quote
Old 08-31-2018, 08:38 PM   #11
Senior Member
 
Datenight's Avatar
 
City: Noank, CT
Country: USA
Vessel Name: Datenight
Join Date: Jan 2008
Posts: 490
Quote:
Originally Posted by foggysail View Post
STRONG!!!! WOW, about 3” thick? Your pictures indicate you did a fine job repairing your boat!!!
Yes, four layers of 3/4" plywood.

Rob
__________________

__________________
North Pacific 39
Datenight is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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





All times are GMT -5. The time now is 09:02 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012