Capping a through hull

[Brian D]

I am thinking of adding a bronze/brass through hull. However, I have no intentions of using it except as a means of an Radio Frequency (RF) ground to seawater. Don't want to use a Dynaplate.

So how would I cap the through hull? Can I just go to Home Depot or Lowes and get a brass cap that is big enough? Or will I need to seek other means?

Thanks

 

[woodster]

Don't use brass ever get bronze. Brass will desolve in a short time and may sink your boat. You could scuff the inside of the through hull and fill it with west system thickened epoxy I say west because it will not shrink on the pour up like polyester will then do an inet search for bronze pipe caps (marine) and cap it off

 

[Bill Roosa]

If you trust the bronze plumbing then trust the cap too. You don't need to fill it with epoxy.

 

[kito]

This doesn't help but I am surprised that Groco or Buck Algonquin doesn't offer a blank through hull fitting. I sure can use one.....

 

[Brian D]

OK, will stick to bronze. I thought about filling, but also thought a cap was readily available.

 

[THECUSCUS]

Most caps will be NPT thread (tapered) and thru hulls are NPS thread (straight). Try to find a NPS cap. I'd hate to see the cap split or come loose and sink your boat. If all you want is a way to ground to water, use a really big bronze bolt. It will have more mass than a thru hull and will actually fill the entire hole you drill in your hull. May be difficult to find such a large diameter bronze bolt though.

 

[Brian D]

Actually thinking of using a scoop strainer. It has more surface area than a mushroom thru hull. I will have to check on what type of threads it has. I didn't really think of the threads. Silly me. Thanks for bringing that up.

 

[SailormanDan]

I capped my overboard discharge from my head (I'm in a NDZ) and was able to get a short section of bronze tubing and a bronze cap for it. I had to order it since I couldn't find it locally. Make sure it's bronze, I had a brass one and then read on here about the regs not allowing it because of electrolysis or dissimilar metals.
If you have a bronze throughhull already, could you attach to that? Or would that be an electrical hazard (risk of shock)?

 

[Brian D]

I don't think I have any bronze thru hulls. At least I have never looked as this is a new project for me. However, if I do they are amidships and my antenna coupler will be aft. So I want to keep the RF ground as short as possible.

I do see a lot of SS caps and Brass caps, but few bronze caps. Will have to keep looking. Thanks for the electrolysis update. Was wondering if that was going to be an issue.

 

[JamesG161]

I am thinking of adding a bronze/brass through hull. However, I have no intentions of using it except as a means of an Radio Frequency (RF) ground to seawater.

I see you have a HAM call sign, KF6BL. I was thinking about renewing my General License.
May I ask what is your power output in Watts?
Why do I ask?
If I guess right, you are using the ocean as an antenna "ground plane" thus inducing a AC/RF current when you transmit. It may be so minor, that it would have little effect on your zinc anode.
Why not use the same ground as your Transmitter's negative power lead? Not it's wire, but a bond system ground or galvanic ground?
Jim...

PS: Past WD4IWB.

 

[JamesG161]

Don't use brass ever get bronze. Brass will desolve in a short time

What is dissolving the Brass and not the Bronze?
Jim...

 

[DougM]

It would cost you more, but if you cannot locate a bronze cap, why not just put a ball valve on the thru hull and leave it closed? I understand that a cap is more logical.
What is the reason for not wanting to use a dynaplate?

 

[Brian D]

Jim, keep that license active. The RF is an AC component and although it normally gets into the DC system, it is best to have it's own means of reflecting the radio waves. The radio is already grounded by the negative battery line. So is the tuner. But I want to keep the AC off the DC as much as possible. I am using Gordon West's recommendation of not going with 100 sqft of copper and just using sea water. However, I also plan on having either 25' or counterpoise or getting the KISS SSB counterpoise. So I should have all avenues for an AC component available. His document. Basically I am looking at using 4" copper strap @ 3mil (.003") as a ground between the tuner's ground post and the through hull.

Doug, I guess it is more temptation than anything else. Don't want someone down below opening a valve that has no hose connected to it. LOL. As for the Dynaplate, I think the connection is the weakest point being just a single small screw. I much prefer the idea of clamping the ground strap directly to the through hull than via a single screw.

 

[Ken Cross]

Jim, keep that license active. The RF is an AC component and although it normally gets into the DC system, it is best to have it's own means of reflecting the radio waves. The radio is already grounded by the negative battery line. So is the tuner. But I want to keep the AC off the DC as much as possible. I am using Gordon West's recommendation of not going with 100 sqft of copper and just using sea water. However, I also plan on having either 25' or counterpoise or getting the KISS SSB counterpoise. So I should have all avenues for an AC component available. His document. Basically I am looking at using 4" copper strap @ 3mil (.003") as a ground between the tuner's ground post and the through hull.

Doug, I guess it is more temptation than anything else. Don't want someone down below opening a valve that has no hose connected to it. LOL. As for the Dynaplate, I think the connection is the weakest point being just a single small screw. I much prefer the idea of clamping the ground strap directly to the through hull than via a single screw.

Several things:

Are you sure the through Hull will have enough surface area for you? You may need to experiment a bit to be sure by hanging something over the side. I'm assuming a fairly large power output. but it will also effect receiver sensitivity.

If you use a valve, remove the handle so it doesn't accidentally get opened and also cap it off if you can.
Ken
I

 

[JamesG161]

Jim, keep that license active.

I need to re-test. So I need to study up for marine SSB.
At least on my boat I would think I could use the lightening protection system ground, without the thru hull.

Actually thinking of using a scoop strainer.

I have one of those on my engine and genset sea water intake already.

I am not wanting to hi-jack the post, but I would suggest doing what "His Document" did.
TEST!

Before making another hole in you boat.
Jim...

PS: I tried taking the General test on QRZ.com and I need a lot of studying.

 

[fruitbat]

I just did this. New thru hull with an inline ball valve. I used a bronze threaded plug on the other side and removed the handle with the valve in the closed position. Finished it off with a wooden bung attached by a lanyard of monel wire. If I someday decide to use the thru hull I can install the hose fittings while the boat is in the water. A cap does not allow you this flexibility.

 

[Sumner]

....Doug, I guess it is more temptation than anything else. Don't want someone down below opening a valve that has no hose connected to it. LOL. ...

I'll bet they would close it real quick . If worried put a short piece of hose on the fitting then plug the end of the hose if you can't find the right cap.

If you go with the thru-hull I documented changing all of the ones on the Endeavour here...

http://purplesagetradingpost.com/sumner/endeavour-plumbing/plumbing-index.html

...pretty much followed all of Maine Sail's advice and he has that on his web site....

http://www.pbase.com/mainecruising/replacing_thruhulls

Sumner
==========================================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...
Mac Trips to Utah, Idaho, Canada, Florida, Bahamas [/QUOTE]

 

[Brian D]

Thanks Sumner.

I believe the Strainer has more surface area than a mushroom. Although a dynaplate would provide more than a strainer. Either way, I believe the strainer to be the better choice. But yes, a test of the strainer overboard would be prudent before drilling new holes in the boat.

 

[wing15601]

JamesG161, it is the zinc component that corrodes when using brass. fittings. Brass is generally copper and zinc while bronze is generally
copper and tin.

 

[Tom G P-21]

Am I missing something? If you just want electrical contact with water why not use a bolt instead of a thru hole? Wouldn't stainless steel work for this application.