Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 29-07-2011, 22:30   #1
Registered User

Join Date: Jul 2011
Location: Chesapeake Bay, Maryland
Boat: 45 Robert Sprau
Posts: 3
Thru Hulls on a Steel Boat

What would be the best material for below waterline thru hulls on a steel boat. Someone suggested Stainless Steel?? But I think maybe Maralon or Brass. Anyone faced this before? What would you use to isolate it?
Thanks
S/V Susana
__________________

__________________
SV Susana is offline   Reply With Quote
Old 29-07-2011, 22:43   #2
Moderator Emeritus
 
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: San Francisco Bay
Boat: research vessel
Posts: 10,150
Re: Thru Hulls on a Steel Boat

A welded on nipple that is either flanged or threaded on the end. A silicon bronze valve is then bolted to the flange or it is threaded on.

The reactivity is not enough to worry about.

I would not use a plastic seacock on a steel hull...it kinda defeats the purpose of having a durable hull.
__________________

__________________
David

Life begins where land ends.
David M is offline   Reply With Quote
Old 29-07-2011, 23:00   #3
CF Adviser
 
Pelagic's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Boat: Van Helleman Schooner 65ft StarGazer
Posts: 6,890
Re: Thru Hulls on a Steel Boat

All my Thru-Hulls and sea valves were converted to Forespar-Marlon about 15 years ago.

Last year when doing a major dry-dock and sandblast, I removed all and inspected. (they were like new)

As they are exercised regularly, they will not seize up on you or cause any electrolysis issues.

David, when you look at the specs on the material….much stronger and durable than plastic

I know renowned builders like Palmer-Johnson use them and they are approved by Class, even in the engine-room
__________________
Pelagic is offline   Reply With Quote
Old 29-07-2011, 23:17   #4
Registered User
 
roblanford's Avatar

Join Date: Apr 2007
Location: SoCal
Boat: kantola
Posts: 164
Re: Thru Hulls on a Steel Boat

A VERY good source of boat building information:

Welcome to the Metal Boat Society

As in everything boats there are many approaches to what you want to do.

I like the idea of marelon valves on a steel nipple. There are some drawbacks though. They're are not maintenance friendly unless you can get one with a grease nipple or figure our how to install one. If they get stuck the fiberglass reinforced nylon handle will most likely break off when trying to force it. Actuate them often to keep them loose.

The easiest way to attach a nipple is to cut a hole in the hull the same size as the od of the nipple and weld on both sides of the hull. Some people do that then put a doubling ring on the inside and then weld to the hull and the nipple.

I believe that Stainless steel below the waterline is unadvisble as some SS develops cracks underwater. Stainless should be kept in the open air. If you use a monel (or other dissimilar metal) nipple keep in mind galvanic action.

Another thing to think about is to minimize the number of through hulls below the waterline.

Hope this helps but as always get advice from experts.
__________________
Robert
roblanford is offline   Reply With Quote
Old 30-07-2011, 02:11   #5
Moderator
 
Boracay's Avatar

Cruisers Forum Supporter

Join Date: Feb 2004
Location: Pelican Bay, Great Sandy National Park
Boat: Steel Roberts Offshore 44
Posts: 5,175
Images: 18
Plastic fantastic...

I am slowly replacing my through hulls with plastic.

No more dissolving boat for me.
__________________
Rust never sleeps
Boracay Blog.
Boracay is offline   Reply With Quote
Old 30-07-2011, 10:24   #6
Moderator Emeritus
 
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: San Francisco Bay
Boat: research vessel
Posts: 10,150
Re: Thru Hulls on a Steel Boat

Quote:
Originally Posted by Pelagic View Post
All my Thru-Hulls and sea valves were converted to Forespar-Marlon about 15 years ago.

Last year when doing a major dry-dock and sandblast, I removed all and inspected. (they were like new)

As they are exercised regularly, they will not seize up on you or cause any electrolysis issues.

David, when you look at the specs on the material….much stronger and durable than plastic

I know renowned builders like Palmer-Johnson use them and they are approved by Class, even in the engine-room
The few years that I tried Marelon was horrible with seized up valves and two busted off handles. I see their only advantage as being inexpensive. I will never go back to using them.

I have been using stainless steel valves threaded onto aluminum pipe nipples on an aluminum hull for over 20 years now with results that are very satisfactory. Never has a stainless steel ball valve seized up on me nor has the metal handle busted off. The reactivity between stainless and aluminum if done correctly is not like many people imagine.
__________________
David

Life begins where land ends.
David M is offline   Reply With Quote
Old 30-07-2011, 10:35   #7
Registered User
 
SabreKai's Avatar

Join Date: Sep 2008
Location: Toronto, Canada on Lake Ontario
Boat: Roberts Offshore 38
Posts: 1,287
Images: 5
Re: Thru Hulls on a Steel Boat

I'm also looking at replacing my thruhulls. My boat has galvanized pipe welded to the skin, but when you look at them from the outside they are rusted up pretty badly. So, they will be coming out, and the brass Home Depot plumbing gate valves will be tossed.

I've decided to go with marelon, and at the same time shift the locations of all the thruhulls to readily accessible locations. As many have noted, they need to be exercised regularly to prevent seizure, and some of mine haven't been touched since installed 33 years ago. The most difficult ones to relocate will be the cockpit drains, as they are way back under the cockpit and to climb in there requires a trained snake with arms. I will be moving them up to the front of the cockpit so I can reach them via the normal engine access point. As a benefit, this will also prevent the water from shooting up 4 feet high every time I hit reverse.
__________________
SabreKai
SV Sabre Dance, Roberts Offshore 38
http://sabredancing.wordpress.com/
SabreKai is offline   Reply With Quote
Old 30-07-2011, 10:50   #8
Registered User
 
S/V Alchemy's Avatar

Join Date: May 2008
Location: Toronto
Boat: Custom 41' Steel Pilothouse Cutter
Posts: 4,576
Re: Thru Hulls on a Steel Boat

Quote:
Originally Posted by Pelagic View Post
All my Thru-Hulls and sea valves were converted to Forespar-Marlon about 15 years ago.

Last year when doing a major dry-dock and sandblast, I removed all and inspected. (they were like new)

As they are exercised regularly, they will not seize up on you or cause any electrolysis issues.

David, when you look at the specs on the material….much stronger and durable than plastic

I know renowned builders like Palmer-Johnson use them and they are approved by Class, even in the engine-room
So far, my Marelon thru-hulls are good, although I respect the question.

I think the larger question concerns reducing the number of holes in a steel hull to a minimum. I have port and starboard thruhulls below the waterline for the head sink drain and the galley sink respectively. Needless to say, it is a simple thing to shut them closed if needed. Of interest perhaps in the three-inch standpipe I have on the centerline, which can be cleared from above and has four T-offs, for engine cooling seawater, head water, A/C coolant and "spare", although this last one can be hooked optionally into the galley sink, and is a handy aid to winterizing the diesel on the hard after bunging the standpipe's terminus.

Anyway, I have heard of fewer Marelon failures than corroded bronze seacocks on steel boats, so I'll carry one spare of each, I suppose!
__________________
S/V Alchemy is offline   Reply With Quote
Old 30-07-2011, 10:54   #9
Registered User
 
S/V Alchemy's Avatar

Join Date: May 2008
Location: Toronto
Boat: Custom 41' Steel Pilothouse Cutter
Posts: 4,576
Re: Thru Hulls on a Steel Boat

Quote:
Originally Posted by SabreKai View Post
I'm also looking at replacing my thruhulls. My boat has galvanized pipe welded to the skin, but when you look at them from the outside they are rusted up pretty badly. So, they will be coming out, and the brass Home Depot plumbing gate valves will be tossed.

I've decided to go with marelon, and at the same time shift the locations of all the thruhulls to readily accessible locations. As many have noted, they need to be exercised regularly to prevent seizure, and some of mine haven't been touched since installed 33 years ago. The most difficult ones to relocate will be the cockpit drains, as they are way back under the cockpit and to climb in there requires a trained snake with arms. I will be moving them up to the front of the cockpit so I can reach them via the normal engine access point. As a benefit, this will also prevent the water from shooting up 4 feet high every time I hit reverse.
SK, you may wish to visit my boat and see how the footwell scuppers are angled aft to the transom instead of down to the hull. As I said in the previous post, if you can possibly reduce your "wet" thruhulls to two or fewer, you are improving the steel boat.
__________________
S/V Alchemy is offline   Reply With Quote
Old 30-07-2011, 17:03   #10
Registered User
 
stillbuilding's Avatar

Join Date: Jan 2008
Location: Hong Kong
Boat: Custom Freya 20m
Posts: 961
+1 for 316 or 2205 s/s.
Welded s/s flange with s/s valve.
Port and stbd intakes for engine cooling, another for all other functions and one outlet for whole boat -all four very accessible for manual checking.
Many survey standards require metal only in the engine space, also required to have dedicated engine intake. P and S inlets are my idea to reduce risk of blockage - been there, done that. Just one outlet to minimize sinking risk - seen that too.
__________________
stillbuilding is offline   Reply With Quote
Old 30-07-2011, 19:34   #11
Moderator
 
Boracay's Avatar

Cruisers Forum Supporter

Join Date: Feb 2004
Location: Pelican Bay, Great Sandy National Park
Boat: Steel Roberts Offshore 44
Posts: 5,175
Images: 18
TruDesign Ball Valves and Thru Hulls...

When Boracay came out last I put in 1 new though hull and replaced two others.

I used TruDesign stuff.





No worries so far, though its only been a few months.
__________________
Rust never sleeps
Boracay Blog.
Boracay is offline   Reply With Quote
Old 30-07-2011, 21:35   #12
Registered User

Join Date: Jul 2011
Location: Chesapeake Bay, Maryland
Boat: 45 Robert Sprau
Posts: 3
Re: Thru Hulls on a Steel Boat

Thanks all for sharing your experiences with Thru Hulls on a steel boat.
__________________
SV Susana is offline   Reply With Quote
Old 30-07-2011, 22:05   #13
Registered User

Join Date: Feb 2009
Posts: 1,321
Re: Thru Hulls on a Steel Boat

I use plain steel Saunders valves, a diaphragm valve. They are spigot mounted the conventional way. A threaded spigot of thick pipe is welded to a round flange then the flange is welded to the hull. Make sure before welding than the valve is facing in the right direction. The valve mechanism and the diaphragm are then removed and the valve body, flange and part of the hull are abrasive blasted and epoxy coated and become part of the hull. Kim makes an inferior copy of the Saunders. I had plastic valves cracking when installed on a spigot and only use them near the water line and carry wooden plugs.
__________________
chala is offline   Reply With Quote
Old 30-07-2011, 22:14   #14
CF Adviser
 
Pelagic's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Boat: Van Helleman Schooner 65ft StarGazer
Posts: 6,890
Re: Thru Hulls on a Steel Boat

Quote:
Originally Posted by SabreKai View Post
. As many have noted, they need to be exercised regularly to prevent seizure, and some of mine haven't been touched since installed 33 years ago.
David is correct, if Marlon is not exercised, they will seize up and the handle is the weak link.

When I bought SG… the holding tank discharge was low down (after the turn of the bilge) and totally inaccessible even for a midget.

In drydock, I had to remove the aircon unit and cabinet to reach it…. Totally seized! So we removed, welded hole shut and found another discharge solution that is accessible.

In drydock we coat the Marlon with lanolin and exercise all valves every 2 months
__________________
Pelagic is offline   Reply With Quote
Old 31-07-2011, 16:02   #15
Registered User
 
lorenzo b's Avatar

Join Date: May 2009
Location: Panama
Boat: Steel trawler 63' Eileen Farrell
Posts: 961
Re: Thru Hulls on a Steel Boat

On most workboats the throughhulls are welded black steel #40, if you use a threaded nipple make sure it's #80 so it will not warp from the welding. From there to brass if you need a valve on it. My transducer is brass threaded to a clean hole in the bottom.
Less is more.
__________________

__________________
lorenzo b is offline   Reply With Quote
Reply

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fiberglass vs Steel Hulls larryb Monohull Sailboats 24 21-08-2016 00:31
Steel Boats and Welding SaltyMonkey Monohull Sailboats 634 04-05-2013 02:54
Thinking of Buying a Sailing Catamaran ? Some Thoughts . . . papagena Multihull Sailboats 12 23-12-2011 11:21
For Sale: Steel Sail Boat blanche Classifieds Archive 5 16-08-2011 15:13



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 12:34.


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.