Association Forum - bronze, stainless, brass, bolts for thruhull

Assn Members Area · Join

Home.

Association Forum

Ships Store

Cruising

Racing

Technical Tips

Photo Gallery - New

Boat Search - Updated

Manuals & Brochures

Swap Meet

Links

Officer Flag Line & Staff

Bylaws & Constitution

Members Area

Join the Association

Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.

Association Forum

Username:	Password:
Save Password
Forgot your Password?

All Forums

Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

bronze, stainless, brass, bolts for thruhull

New Topic

Topic Locked

Printer Friendly

Author

Topic

Deric
Captain

Member Avatar

USA
408 Posts

Initially Posted - 04/14/2008 : 20:07:05

Hello Folks,

I haven't been online here for the past two weeks because I have been working on getting my sailboat ready for splash.

I am in the midst of replacing my thruhull and realized that the Groco flanged base is made of bronze, and that it is best to use bronze bolts: don't mix metals is what I heard.

I visited several hardware stores, West Marine, and a place that specializes in fasteners. Well, wouldn't you know, that the cheapest part of this project has, once again, stymied my progress.

Where does one acquire the proper metal bolts?

My goal is to fasten three bolt/screws - - counter sunk - - through the hull and into the flanged base, secured with nuts.

What have others used for bolts?

Some have suggested using stainless steel with sealant between the bolts and the flange, others suggested brass bolts.

I merely need three 2.5 inch bronze bolts 3/8 thick. One wouldn't think acquiring these would be a difficult task.

Heh, it's the little stuff that makes life interesting.

Other than the bolts, I have been stripping the bottom paint, installing a second battery, glassing a few places.

Hope everyone is doing well in their boat preparation.

Thanks
Deric

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

Members Avatar

USA
4479 Posts

Response Posted - 04/14/2008 : 20:21:27

Here you go Deric: http://www.boltdepot.com/product.aspx?cc=6& cs=7& cm=5& cd=57

Edited by - on

Dave Bristle
Master Marine Consultant

Members Avatar

Djibouti
10005 Posts

Response Posted - 04/14/2008 : 21:43:08

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Deric
 ...My goal is to fasten three bolt/screws - - counter sunk - - through the hull and into the flanged base, secured with nuts... I merely need three 2.5 inch bronze bolts 3/8 thick.<hr height="1" noshade id="quote"></blockquote id="quote">For a "permanent" installation, I'd push for silicon-bronze. Anything else, even with sealers, is semi-permanent at best. (Brass is primarily decorative, and not great for heavy-duty fastening under the waterline.)

By "countersunk", I assume you mean flathead machine screws... WM shows 5/16 x 2.5" in the catalog (no 3/8" in flatheads)--they might have them in the store here by the piece. Have you checked a Home Depot or Lowes?

Edited by - on

Dave5041
Former Mainsheet Editor

Members Avatar

USA
3758 Posts

Response Posted - 04/14/2008 : 23:15:28

Some WM stores have pretty good selections of bronze screws and bolts. Are you sure about the size? Three 3/8" bronze bolts could be used to lift a Cat 25. Heavily loaded blocks an deck are attached with smaller hardware. But do stay with silicon bronze, it is better than stainless under water. An online search should find suppliers, and check Good Old Boat's web site for links - I know at least one supplier advertises with them. But keep in mind that bronze is not cheap.

Edited by - on

Deric
Captain

Members Avatar

USA
408 Posts

Response Posted - 04/15/2008 : 19:25:12

Update:

I spoke with BoltDepot and ordered the silicon bronze bolts. I ordered the 5/16 size flat head machine bolts with washers and nuts. I should receive the hardware before Friday; I can work on the weekend putting it together.

Indeed bronze in not cheap, but I have balanced my priorities: my car takes second place after my boat.

This is a great online community. I learn much from this group.

Thank you,
Deric

Edited by - on

Deric
Captain

Members Avatar

USA
408 Posts

Response Posted - 04/16/2008 : 21:11:29

One more question to throw out regarding this thread.

I was talking with a fellow sailor about the silicon bronze bolts. His question to me was, "what is the silicon part of the bolt, is it coated in silicon?"

Anyone know the answer?

Thanks
Deric

Edited by - on

britinusa
Web Editor

Members Avatar

USA
5404 Posts

Response Posted - 04/16/2008 : 21:18:49

<blockquote id="quote">quote:<hr height="1" noshade id="quote"> Alloy C873 is also known as a Silicon-Bronze (or sometimes Silicon-Brass). Because of it's low lead content silicon-bronze is often a replacement for leaded plumbing brasses. Silicon Bronze is considered to be ideal for the amateur foundry. It can be remelted numerous times without changing composition. It has excellent pouring characteristics and gives a good surface finish. It has poor machinability however (Index of 40). The main use of this material is in art sculpture and plaques. It can be readily joined by brazing with oxyacetylene. It is composed of approximately 95% Copper, 4% Silicon, and 1% Manganese. It's pouring temperature is 1850 F - 2150 F.<hr height="1" noshade id="quote"></blockquote id="quote">

from http://www.budgetcastingsupply.com/Metals.php

Paul

Edited by - on

Dave5041
Former Mainsheet Editor

Members Avatar

USA
3758 Posts

Response Posted - 04/16/2008 : 21:39:07

And many similar alloys. Minute changes result in some s-b's being stronger than stainless, increased malleability, harder, or softer, but the one thing nearly all of them have in common is greater resistance to corrosion than stainless, especially in oxygen depleted environments - underwater.

Edited by - on

Deric
Captain

Members Avatar

USA
408 Posts

Response Posted - 04/17/2008 : 20:14:22

Thanks for the clarification regarding Alloy C873 (Silicon-Brass).

The bolts arrived today from Boltdepot. They are the right bolts for my new thruhull job, which I shall be working on this weekend.

BTW - boltdepot was very quick to take my order and send the hardware. Great resource to have saved in my favorites for future jobs.

Edited by - on

noom
Deckhand

Members Avatar

1 Posts

Response Posted - 10/14/2009 : 11:17:11

Here is a source for silicon bronze ingots if raw materials are needed for custom parts http://www.cmxmetals.com/art-bronzes/

Edited by - on

skrenz
Captain

Members Avatar

USA
351 Posts

Response Posted - 10/16/2009 : 08:18:25

Bronze is definitely the way to go. Brass won't cause a dissimilar metals problem because it is close enough on the nobility scale not to matter, but it is not nearly as strong as bronze.

I always thought the obvious place was Jamestown Distributors - www.jamestowndistributors.com. They sell all sorts of fasteners including silicon bronze. They sell all sorts of other marine stuff too at sometimes reasonable prices. They are helpful on the phone and will even sell a single fastener if you request it. Their advertised price for a 5/16 x 2.5" flat head bronze machine screw was $1.74 each plus shipping. How does this compare to where you eventually got yours from Deric? I would like to know because I need to do the same job after haul out.

O.J. I think what he is referring to is the connection of the seacock to the hull. The thru-hull fitting, long threaded tube with flange on one end, then goes from the outside and screws into the base of the seacock. Many boats are built using only the flange nut on the thru-hull and then thread a ball valve onto the top of the thru-hull. That is not the best / safest way to do thru hull connections. Probably because the bolts that bolt the seacock to the hull provide needed stability to the whole assembly.

Edited by - on

Dave Bristle
Master Marine Consultant

Members Avatar

Djibouti
10005 Posts

Response Posted - 10/18/2009 : 09:50:31

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by skrenz
 O.J. I think what he is referring to is the connection of the seacock to the hull. The thru-hull fitting, long threaded tube with flange on one end, then goes from the outside and screws into the base of the seacock. Many boats are built using only the flange nut on the thru-hull and then thread a ball valve onto the top of the thru-hull. That is not the best / safest way to do thru hull connections. Probably because the bolts that bolt the seacock to the hull provide needed stability to the whole assembly.<hr height="1" noshade id="quote"></blockquote id="quote">Are you referring to screws going through from the outside of the hull to the seacock? I've never seen that done. I've seen seacocks with flanges bolted to a sole or bulkhead with a hose leading to the thru-hull, although never when the thru-hull is below the waterline. IMHO, a below-water thru-hull needs valve mounted directly on it--no lines to burst or clamps to give way. (EDIT:) The flange of a seacock should suffice for stability inside without any bolts through the hull. A proper backer (like starboard) for the flange provides even better stability.

Edited by - Dave Bristle on 10/18/2009 10:43:44

skrenz
Captain

Members Avatar

USA
351 Posts

Response Posted - 10/19/2009 : 13:56:34

I think we are saying the same thing. Valve and thru-hull should be all part of same device. I was speaking only to what OJ was asking about.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Dave Bristle
(EDIT:) The flange of a seacock should suffice for stability inside without any bolts through the hull. A proper backer (like starboard) for the flange provides even better stability.
<hr height="1" noshade id="quote"></blockquote id="quote">

If this is the case, then Deric doesn't need any bolts at all. But I wonder why you think you shouldn't set it up this way by bolting through the hull with flat heads bolts to the seacock base flange.

Edited by - on

Dave Bristle
Master Marine Consultant

Members Avatar

Djibouti
10005 Posts

Response Posted - 10/19/2009 : 14:32:28

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by skrenz
 If this is the case, then Deric doesn't need any bolts at all. But I wonder why you think you shouldn't set it up this way by bolting through the hull with flat heads bolts to the seacock base flange.
<hr height="1" noshade id="quote"></blockquote id="quote">This is my observation/opinion only... but I believe the bolt holes (generally three) on the seacock flange (base) are for mounting the seacock inside the boat when it's used separate from a thru-hull. To me, when it's used as the inner collar to the thru-hull, adding the bolts through the hull very close to the larger hole for the thru-hull (1) adds opportunities for leaks, (2) increases chances for damage from corrosion, and/or (3) weakens the laminate somewhat around the thru-hull. Flat-head bolts by themselves are not a particularly good fastener against a fiberglass surface. The normal fastening would be the bolt heads against the seacock base with large washers and nuts against the fiberglass--not very attractive on the outside of the hull. The compression of the base against the inside of the hull (or better yet a backer) should create plenty of rigidity.

BTW, he did the job back in April--with the bolts--so this discussion is academic.

Edited by - Dave Bristle on 10/19/2009 14:39:22

skrenz
Captain

Members Avatar

USA
351 Posts

Response Posted - 10/19/2009 : 15:03:29

Dave,
I reference this set of instructions by Don Casey from This Old Boat:

http://www.boatus.com/boattech/Casey/07.htm

Note this part: "Position the seacock the way you want it and make sure you can turn the handle without scraping knuckles. If it has a drain plug, try to orient the plug on the low side of the valve. Once satisfied with the position, drill mounting holes through the hull from inside the boat, using the holes in the mounting flange as a drill guide. If the flange is not pre-drilled, drill three evenly spaced holes through the flange and the hull. From outside the hull, countersink the three holes."

This article also describes the same use of the screws through the hull. It also has a diagram of the difference between a seacock and a ball valve attached to the thru-hull.

http://www.diybob.com/diySeacock.htm

And this is the installation instructions from Groco:

http://www.groco.net/SVC-MAN-07/Sec4/PDF/IBV-FBV-TB.pdf

All of these indicate the use of the bolts through the hull and into the flange of the seacock.

Edited by - on

Dave Bristle
Master Marine Consultant

Members Avatar

Djibouti
10005 Posts

Response Posted - 10/19/2009 : 18:34:23

I bow to the experts. Personally, I'm not sure I'd do it that way, and I don't recall seeing bolt heads around a thru-hull on the outside of a hull. I would screw the thru-hull into the seacock until its flange was tight against the backer (with appropriate caulk) and possibly put some screws through the flange into the backer to prevent it from twisting loose. I really don't like all those holes and the screw heads alone countersunk into the fiberglass. But that's me--it's not Don Casey.

Edited by - on

OJ
Master Marine Consultant

Members Avatar

USA
4382 Posts

Response Posted - 10/21/2009 : 04:24:58

Deric,

It sure would be interesting to see your finished thru hull. It might clarify in a few minds (or just mine) exactly what this project involved. I'm always looking for a better way to do things!

Edited by - on

Topic

New Topic

Topic Locked

Printer Friendly

Jump To:

Association Forum

Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.