West marine and probably most marine equipment suppliers carry a grounding plate which is used for exactly what you want.
Capping a through hull
- Thread starter Brian D
- Start date
I like his idea myself
. Get a plate of the size and material that will work and run a bolt of similar metal thought the hull a little ways down the waterline. One small hole, easy to seal on both sides (not much water pressure a little ways down the hull).
If it later needs to be removed just washer both sides of the hull on the bolt and you should be good to go or you could even glass the hole shut.
Way cheaper and easier and probably will work better than putting in a thru-hull you don't need,
Sumner
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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
Tom, no you are not missing anything. However, when dealing with RF, one wants as much surface area in the water as possible. Dynaplates use 6x18x.5 to create 100sqft for RF grounding. RF generates a high current and the bigger the surface area the better the dispersion of that current. Like a vertical antenna on land, the more ground plane counterpoise you have be better your signal. This also holds true for HF antennas at sea. So a bolt will work, but the bigger the surface area the better.
Back to the OP, I am wondering if a PVC cap would work? There should be no pressure except sea level on the cap. Granted it has no electrical properties. Just wondering out loud. I should stick to Bronze.
Added - Here is an analogy. The wetted surface area of an RF ground is as the keel is to the sails as is the wetted surface of the hull is to the boats theoretical speed.
Back to the OP, I am wondering if a PVC cap would work? There should be no pressure except sea level on the cap. Granted it has no electrical properties. Just wondering out loud. I should stick to Bronze.
Added - Here is an analogy. The wetted surface area of an RF ground is as the keel is to the sails as is the wetted surface of the hull is to the boats theoretical speed.
The bolt or maybe two could hold a plate of whatever size surface you felt you needed and it would be easy to change to a larger or smaller plate if needed,
Sumner
============================================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...http://purplesagetradingpost.com/sumner/endeavour-main/endeavour-index.html
Mac Trips to Utah, Idaho, Canada, Florida, Bahamas
I could see a bolt with a large fender washer coming from inside the hull to the outside with another fender washer and nut on the outside. Then size the length so that the plate would go on the bolt and against another fender washer on the nut with another fender washer on the other side and with a final nut to hold the plate to the bolt shank. Inside there would be a tab you could connect to between the bolt head and the nut on that side.
If the plate was very long I'd use two bolts near the fore and aft ends of the plate. Since the plate would be about 3/8's of an inch off the hull you would have the benefit of the sea water on both sides of it, maybe less area needed?
Sumner
=======================================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...http://purplesagetradingpost.com/sumner/endeavour-main/endeavour-index.html
Mac Trips to Utah, Idaho, Canada, Florida, Bahamas
Yes.
If I got the idea right, then you are going to install a thru hull bronze piece with as large area of an exposed surface like...
then CAP the thru hull with a PVC cap to prevent water flow.
PVC would be great and if you want to give added protection, fill the cap with 4200, not 5200. Then it is useable in the future.
Once that is done and sealed, you will connect your RF ground to that new Bronze thru hull on dry side to give you a better RF signal. Whew, that was a mouthful.
Jim...
PS: dit dah dit ... dit dah dit
Brian, you could get one of the compression pipe plugs. But if it was me I'd trade the hardware in for stainless instead of the supplied zinc plated.
Fred Villiard
K3VKY
Fred Villiard
K3VKY
I strongly suggest you go to THE most knowledgeable voice about radios & grounds: Gordon West<.>
Brian, why don't you just use a KISS-SSB ground plane? That way you wouldn't have to put another hole in the bottom of the boat.
http://www.kiss-ssb.com/
http://www.kiss-ssb.com/
I am Never facetious!
I would use a PVC cap with the right thread match and no Teflon® tape needed.
When I finally "got" what you wanted, I had to repeat it to assure, my YES answer was right.
I thought my Morse code "PS:" would have confirmed that.
If you decide on that scupper, let me know if it worked.
Jim...
PS: Trivia... the only word in the English language that contains all the vowels in right order is...
FACETIOUS.
I had a classic copper grounding foil attached to a keel bolt. It rotted in several places over the years and the foil was a PITA whenever I had to work around it. I replaced it with a KISS. I don't know why you would need a water ground.
Think you hams need to pull out your copy of Radio basics. The RF counterpoise is about as large as you could possably need when operating above 8 kHZ (ie it is big enough). It is called the ocean. The problem is how do you tap into it without much loss in signal strength. So you are looking for a "wire" to connecte the ground at the antenna base/coax shield to the water. If you are mounting stuff to the stern rail think braided cable running from the antenna base to the water surface. also thing of mounting the antenna base down low or you will have a impedaince different from the antenna's stated impedance. The ground/centerpoise wire acts like a short section of dipole before it gets to the water. This gets much more dramatic when you run copper foil all around the boat and HOPE it connects capacitively to the water on the outside.
Also the RF stays very close to the water surface so "attaching the RF ground to the keel" is not nearly as effective as droping a wire through the water's surface.
Tried this with my smoking 5 watt yat 819. Actually used a 8 gage wire and a clip to my uninsulated backstay. reception was great and I could be heard on 20 meters in Europe with no problem.
I personnaly believe that the proponents of copper foil all install HF radios and need the work. Kinda hard to make a living if all you do is connect the antenna to a big bolt and drop it in the water.
Also the RF stays very close to the water surface so "attaching the RF ground to the keel" is not nearly as effective as droping a wire through the water's surface.
Tried this with my smoking 5 watt yat 819. Actually used a 8 gage wire and a clip to my uninsulated backstay. reception was great and I could be heard on 20 meters in Europe with no problem.
I personnaly believe that the proponents of copper foil all install HF radios and need the work. Kinda hard to make a living if all you do is connect the antenna to a big bolt and drop it in the water.
Bill, nice explanation, and I wish it was really that simple. However, a boat is not a home station where one can get away with just about anything. For a temporary installation on a boat that might work. However, for more permanent installation one has to worry about creepy RF getting into everything, and all the other electronics and luxuries making noise that the receiver can pickup.
Here at home I have a 36' piece of wire running from my eave to a tree with a 25' wire dropped to the ground. No physical contact with the ground. Works great (with a 9:1 UnUn Balun). Auto tuner lets me work all bands except 160/80. It tunes 80 but there is not enough counterpoise for it to be useful.
This is why making a permanent installation on a boat require more umph, if I may. LOL
Here at home I have a 36' piece of wire running from my eave to a tree with a 25' wire dropped to the ground. No physical contact with the ground. Works great (with a 9:1 UnUn Balun). Auto tuner lets me work all bands except 160/80. It tunes 80 but there is not enough counterpoise for it to be useful.
This is why making a permanent installation on a boat require more umph, if I may. LOL
Along with:I am Never facetious!
PS: Trivia... the only word in the English language that contains all the vowels in right order is...
FACETIOUS.
abstemious
abstemiously
abstentious
aerious
annelidous
arsenious (my favorite, as a chemist)
caesious
facetiously
fracedinous
As the Admiral looked over ABSTEMIOUSLY at me, as I begin to mix my 4th martini, my ARSENIOUS mind thought FACETIOUSLY about a rude gesture, but thinking wisely I became ABSTENTIOUS wondering my supper would be ANNELDIOS.
I stand corrected to..
Facetiously (sometimes Y) as the non archaic word in Websters with all the vowels.