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Decommissioning through hulls?

3K views 19 replies 15 participants last post by  Watercolor 
#1 ·
I am strategically planning for my upcoming haulout...

Now that I have a composting toilet and it is here to stay, I have several through hulls that I don't need anymore. Is there a way to decommission them without major fiberglass surgery? I also may want to use them again one day for a water maker.

What about putting a threaded bronze plug into a seacock and leaving the seacock closed? Is my surveyor going to have a heart attack? Is there a better way?

Something like this in the closed position?



Plus this:



MedSailor
 
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#2 ·
As long as the threads on both are NPT and the seacock is sound I think that would be OK. It does leave an option open... However if it's truly never to be used again I think removal and some glasswork is the way to go.
 
#6 ·
Fixing a small thru hull isn't surgery, it's more of a band aid. Tape the bottom off with duct tape, and pour in thickened epoxy until the hole is full. Let cure, then remove tape.

If you ever need to reinstall it, just drill back thru the epoxy plug.
I am not a fiberglass wizard but I would be VERY skeptical about this advice. I would not want to have a plug of epoxy at the bottom of the boat, held by its rim with questionable adhesive properties.

It is not rocket science and does not take long to appropriately bevel the hole and put in the required layers of fiberglass.
 
#7 ·
Med,

In your case, ie you want to add a water maker, I would leave the thru hole there, and plug as you have shown. This way you have it available when the time comes.
For the ones you do not need, or if the current thru hole is not in the correct place, a proper patch would be appropriate. Not sure I would totally agree with stumbles simple approach. I believe as mentioned, there are BETTER ways to fill the hole in a more permanent way!

Marty
 
#8 ·
Mast,

The adhesive strength of epoxy to cured fiberglass is higher than the tear strength of the original glass. The reason to bevel glass repairs is because a plug makes a hard spot in the hull that doesn't flex with the rest of the hull. For large repairs its absolutely required, but for <1" hole, just poured epoxy is fine.
 
#9 ·
I don't buy it.

First, adhesive strength varies a lot with the quality of the substrate (roughness, presence of contaminants). I would have serious doubts about a situation where you just slap some duct tape under the hole as you proposed.

Second, epoxy is reasonably strong in compression but has low tensile strength. It is only the combination of resin and glass that is strong (just like reinforced concrete; cement putty by itself is very weak). Even if you have perfect adhesion at the rim, an impact will easily shatter not-reinforced epoxy which is quite brittle.

Third, why do you assume a <1" hole? Head seacocks are typically 1 1/2" nominal which means over 2" real, meaning the hole has an area of over 4sq in. This is consistent with the picture of the seacock shown in the original posting.
 
#10 ·
The proper way to do this.

Duct tape & plastic over thru hull hole inside the boat. Grind back the hull on an angle, 4+" around the thru hull. Cut fiberglass mat in circles, each one a little smaller than the next. Start w/ the largest & keep pilling on the smaller patches in sequence. Once you're at the desired thickness, slap the fairing compound on.

Do this glass work all in one shot. Once dry, sand & fair out again, apply barrier, bottom paint.

Works best w/ 2 people, you gotta move pretty quick to complete the 1st step in one hot
 
#13 ·
The proper way to do this.

Duct tape & plastic over thru hull hole inside the boat. Grind back the hull on an angle, 4+" around the thru hull. Cut fiberglass mat in circles, each one a little smaller than the next. Start w/ the largest & keep pilling on the smaller patches in sequence. Once you're at the desired thickness, slap the fairing compound on.
Most mat is not compatible with epoxy. Biaxial roving is a good choice as would be heavier fiberglass cloth. As posted by others the epoxy only plug is not a very good method. The proper method is shown below. Note that the largest patch is put on first. This eliminates the chance of sanding through it during finishing weakening the repair.
 

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#11 ·
They don't call them "best practices" for nothing -- I don't think Stumble's solution would qualify.

Med -- I think your plug idea will work fine. Good joint compound on the threads, and then close the seacock and remove the handle. You'll still want to exercise it periodically, so keep the handle available.
 
#12 ·
I think I would plug it as you are thinking but leave the valve open after it is plugged and exercise it open and shut occasionally. If left shut the downstream side will likely fill with water due to seat leakage and there is a slight possibility of overpressure with temp changes or damage due to freezing. The properly installed plug (tape or pipe dope on the threads) will not leak inboard and is plenty strong - likely stronger than the hull.
 
#14 ·
My wife and I have done a lot of fiberglass hull repairs on our boats. It's not rocket science. There are a lot of good books on the subject that can take you through the process step by step, follow them closely, but don't be anal about it. Don't be impatient (let the layers cure). Don't skimp (especially on the hole size preparation). And above all recognize that you can rectify a mistake.

Having said all that, I'd say your in good shape leaving the seacocks in place, giving them a good greasing before closing and plugging them. It wouldn't hurt to even exercise them on occasion.

The only reason I'd leave them in is potential resale. No matter how good some people feel about composting toilets, others don't have the same warm and fuzzy felling about them. If you're looking to sell the boat later on the ability to convert back, if the new owner so chooses, is a selling point.
 
#15 ·
I'm thinking of pulling my old through hull transducer, and going the fiberglass & epoxy route. I replaced the old Signet depth sounder and 1¼" transducer with a Garmin fishfinder. I mounted the new transducer inside the hull on a bed of silicone glue. Works great!

Can anyone think of any reason why I might want to leave the 1¼" hole?
 
#17 ·
I was given advice that is a blend of the above. Grind/bevel the hole. Duct tape the outside. Mix up some Fiber Hair and fill from inside. Cover inside and out with fiberglass cloth. Makes a nice, strong sandwich.

I've done this a handful of times over the years with god results.
 
#18 ·
The term Best Practices comes into play

BEST - Hull ground outside and inside, glass replaced on both sides
GOOD - Hull ground on inside, glass replaced
MARGINAL - Epoxy in hole.

Since the epoxy is a different density and flexibility than the surrounding glass, the edges will be under greater stress and will want to shear or tear. Will it happen? I don't know. This method would probably work fine, but I'd stay with time proven methods if you go far offshore. Pick up a book by Don Casey. Easy read, step-by-step. Even a Geico advertising icon could do it.
 
#19 ·
For the record I'm not considering the epoxy in the through-hull idea. I don't see the advantage over the pipe plug.

I'm leaning towards the pipe plug and leaving the through hulls in place for 2 reasons. First I might use them again. Second, I think my first real fiberglass job shouldn't be on the under-side of my hull.

Perhaps at the next haul-out, or the one after, I'll have a better idea of which ones I want to keep and I may have a few "above the waterline" fiberglass projects already completed.

MedSailor
 
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