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Old 14-05-2022, 00:19   #1
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Filler options for fairing inside the hull

Hi all,

I’m looking for ideas on fairing the inside of a fibreglass hull with an encapsulated keel, mainly around the centreline.

I’m building water tanks below the cabin sole, and I’d like the bottom of the tanks to be as smooth and even as possible. Therefore, I’d like to fill the shallow trench that runs along the centreline of the hull. I’ve installed PVC pipes as extended limber holes below the tanks, but I have a trench that is about 200 mm wide and 40 mm deep (9 inches x 1.5 inches for those not loving the metric system) running the whole length of the cabin. The trench bottom is pretty irregular from when they glassed over the encapsulated iron ballast keel. Also, the pipes are either side of the trench and they need fairing into the hull. Plan is to put a layer of vinylester fibreglass over the whole lot once it is nicely faired.

I tried spray foam for the pipes and it was not a success. I thought maybe two-part poured foam might be a little better, but frankly, I’ve got myself into all kinds of a mess with it in the past.

Any recommendations for filling the trench? Maybe something as simple as sand and cement?

Matt
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Old 14-05-2022, 00:30   #2
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Re: Filler options for fairing inside the hull

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Originally Posted by GILow View Post
Hi all,

I’m looking for ideas on fairing the inside of a fibreglass hull with an encapsulated keel, mainly around the centreline.

I’m building water tanks below the cabin sole, and I’d like the bottom of the tanks to be as smooth and even as possible. Therefore, I’d like to fill the shallow trench that runs along the centreline of the hull. I’ve installed PVC pipes as extended limber holes below the tanks, but I have a trench that is about 200 mm wide and 40 mm deep (9 inches x 1.5 inches for those not loving the metric system) running the whole length of the cabin. The trench bottom is pretty irregular from when they glassed over the encapsulated iron ballast keel. Also, the pipes are either side of the trench and they need fairing into the hull. Plan is to put a layer of vinylester fibreglass over the whole lot once it is nicely faired.

I tried spray foam for the pipes and it was not a success. I thought maybe two-part poured foam might be a little better, but frankly, I’ve got myself into all kinds of a mess with it in the past.

Any recommendations for filling the trench? Maybe something as simple as sand and cement?

Matt
Matt, are you wanting to smooth the irregular base while still having a "trench"down the centerline, or are you wanting to fill it to the top of the pipes allowing a single smooth surface across the entire base?
Bob.
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Old 14-05-2022, 00:58   #3
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Re: Filler options for fairing inside the hull

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Matt, are you wanting to smooth the irregular base while still having a "trench"down the centerline, or are you wanting to fill it to the top of the pipes allowing a single smooth surface across the entire base?

Bob.


Happy with either.
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Old 14-05-2022, 01:00   #4
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Re: Filler options for fairing inside the hull

Just got talked out of sand and cement by a fellow yachtie.
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Old 14-05-2022, 01:09   #5
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Re: Filler options for fairing inside the hull

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Just got talked out of sand and cement by a fellow yachtie.
Sage advice

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Happy with either.
If leaving a trench down the middle I think I would use some bog made from the vinylester resin and microballoons, use it for fairing and filleting and on either side of the pipes I would try the two part foam. I know it can be messy but it is relatively easy to shape after the event and the glass will go over the top easily. The center trench will give you a low point for the pickup to the pump.
Party on.
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Old 14-05-2022, 01:20   #6
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Re: Filler options for fairing inside the hull

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Sage advice







If leaving a trench down the middle I think I would use some bog made from the vinylester resin and microballoons, use it for fairing and filleting and on either side of the pipes I would try the two part foam. I know it can be messy but it is relatively easy to shape after the event and the glass will go over the top easily. The center trench will give you a low point for the pickup to the pump.

Party on.

I just know I’m going to end up stuck to my bilge.
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Old 14-05-2022, 01:22   #7
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Re: Filler options for fairing inside the hull

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I just know I’m going to end up stuck to my bilge.
Ahh, not if you embrace moderation.
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Old 14-05-2022, 01:40   #8
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Filler options for fairing inside the hull

I just remembered using wood shavings and epoxy for a similar job. Problem is, I don’t have any wood shavings. Might be time to pull out the planer.

Edit: of course I’d have to use vinylester, not epoxy, but it might work.
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Old 14-05-2022, 01:43   #9
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Re: Filler options for fairing inside the hull

Matt

I'd use polyester (or vinylester)/talcum powder mix to even out the irregularities.

Be careful though that the resins/curing procedure produces a tank suitable for potable water. (Can be hard in the bilge of a yacht)


"Certainly, fiberglass water tanks are made using resins, but these are manufactured using resins that are perfectly matched for storing a specific liquid material. This means that yes, there are certain fiberglass water tanks that would be unsafe for storing potable drinking water. However, there are other, specially designed fiberglass water tanks that are perfectly safe and compliant with the" Australian Standard AS4020.

I've coated the internal of my tanks with a Crommelin Water Based Bitumen paint.



https://www.crommelin.com.au/wp-cont...erproofing.pdf
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Old 14-05-2022, 01:51   #10
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Re: Filler options for fairing inside the hull

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Matt


I'd use polyester (or vinylester)/talcum powder mix to even out the irregularities.

What kind of volume ratio do you get from talc and resin? Does it double, triple the volume? Trying to get a feel for how much resin this would consume.
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Old 14-05-2022, 02:00   #11
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Re: Filler options for fairing inside the hull

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What kind of volume ratio do you get from talc and resin? Does it double, triple the volume? Trying to get a feel for how much resin this would consume.

I buy my resin in 20L drums. I bought two the other day to seal the lead ballast and they cost $500 (and the way the $A is going it will shortly cost a fair bit more).
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Old 14-05-2022, 02:23   #12
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Re: Filler options for fairing inside the hull

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What kind of volume ratio do you get from talc and resin? Does it double, triple the volume? Trying to get a feel for how much resin this would consume.

I mix my resin/talc in a 2L ice-cream container so that probably uses half a .5 to .7 liter of resin. (of course that's a guess). But that should smooth out quite a large area surely?
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Old 14-05-2022, 02:37   #13
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Re: Filler options for fairing inside the hull

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I mix my resin/talc in a 2L ice-cream container so that probably uses half a .5 to .7 liter of resin. (of course that's a guess). But that should smooth out quite a large area surely?


So are you saying you get 2 litres of volume of paste from the 0.5 to 0.7 litres of resin?
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Old 14-05-2022, 02:53   #14
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Re: Filler options for fairing inside the hull

Just remembered another trick I was told about… chop up some CSM with scissors into a sort of fluffy mess. Mix with resin.
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Old 14-05-2022, 03:07   #15
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Re: Filler options for fairing inside the hull

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Just remembered another trick I was told about… chop up some CSM with scissors into a sort of fluffy mess. Mix with resin.
That will guarantee that you glue yourself to the bilge.

I would just make bog with resin and microballoons (Q-cells) in batches as big as I could manage and smedge it in there until the pipes were buried. The filler usually about doubles the volume of resin, depending on how thick you want it.
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