Drying out foam in the laminate

[Sonosailor]

Cat Tales, a FP Tobago 35 is pedominately a fibreglass and PVC foam sandwich, especially below the waterline. The previous owner (charter company) installed a rubber bumper along the stern to protect the hull from other boats, dinghys and docks. They installed this with long SS screws that almost assuredly broke through to the PVC foam. The boat is sitting in the Virgins on the hard with the rubber removed and the screws out, and the holes spit out salt water from time to time.

Any tricks to removing more water and/or salt before we fill the holes?

I'm thinking using a vacuum cleaner and possibly pushing solvents in; or putting distilled water in and vacuuming it out to get the saltier bits out; or just getting as much as practical out, blocking and trapping the rest. If this is in a thread elsewhere, please point the way, as I could not find it.

Concrete ideas, strong opinions, two bit opinions all welcome.

[colemj]

Another FP35 owner (Irie) reported that the stern crash compartment was filled with floatation foam (I think on CF here, but you could also check their website). I bet this is what is holding water, and not foam coring. In fact, I doubt there is any core at all one the end of the stern where the bumper was installed because this area is most likely a hull/deck joint.

Mark

[ssanzone]

Lots and lots of heat from the inside (think salamander for multiple consecutive days) and Isopropyl Alcohol injected directly into the holes. I have used the cheap syringes sold at drug stores for giving babies medications.

Isopropyl Alcohol is the same active ingredient in all those 'swimmers ear' product and will, as well as anything dry out the trapped water.

It seems clear that you understand the importance of making sure the core is dry before filling the screw holes so I would explore any and every option / product to reduce the risk of filling a hole where water is still present.

gl.

-steve

[Stumble]

Any idea how bad the problem really is?

The real answer is to cut out the foam and replace it. Once foam starts absorbing water there just isn't a good way to get rid of it.

Second best is to try and pull a vaccume on it. A normal shop vac won't to anything, you need to pull a strong enough vaccume to reduce the boiling temp down to what can be achieved with heat lamps. This means close to the same level of vaccume you need for infusion, around 29in hg. This is a really strong vaccume, and needs to be maintained for days. Heating the area will help, and it helps to reduce the vaccume needed, but short of a drying kiln I don't know how to raise the temp of the entire boat enough.


Assuming there is real water penetration, this is a major issue and needs to be looked at by a professional. It isn't the type of thing that can be fixed with a shop-vac and a heat lamp.

[colemj]

The first thing you should do is check with Irie to see if my hypothesis is correct.

If it is, no amount of salamanders, isopropanol, vacuum or professionals is going to help. You will need to either remove the foam filling, or just dry the standing water out of it, seal it up and ignore it - it isn't structural.

Mark

[lifeofreilly57]

Isopropal alcohol works in the decks I've dried out and repaired, not sure how it works on foam, might be worth looking into. Most of my experience has been with balsa and ply cores.
Depending on how much water is in there it may take a fair amount of alcohol to help it evaporate, you've got to get enough to get a fair ratio with the water.
Heat from the inside helps on decks, not sure how well it would work on a stern section. It depends on how large the area of the holes is.
In some cases I've had to open up the holes and increase the number of holes to allow sufficient surface area to allow the resulting vapor to disperse, if your just talking small screw hoes it may not allow enough air circulation to dry it out. In a deck it's easy enough to do this from the underside of the deck and then re-glass. Is it possible in your case to add larger and more openings from the inside? It might be the way to go.
Then lots of dry heat over a long period of time.

[Boatyarddog]

Will the water compromise the foam? It's not wood or glue.
The glass around it would be okey.
It's a stiffener. But not susceptible to water damage, mainly weight of water.
I wouldn't think it's too much weight though.


Sent from my iPad SV Cloud Duster

[Boatyarddog]

I don't know much about foam compositions.


Sent from my iPad SV Cloud Duster

[UNCIVILIZED]

It sounds like you're seriously concerned about it, so a couple of different levels of steps to analyze (get a better picture of) the problem come to mind.

- Is there any reason that you couldn't drill a series of 1/2" - 3/4" holes in various locations all in the general transom(s) area of the hulls? Both horizontal & vertical.
And as a wise man once said, do it with a cordless drill, so that you don't fry yourself if there happens to be a lot of water in there.

So obviously such holes will let you know if there's a quantity of standing water in there. But also, they may be viable locations to test with a moisture meter. Although on that I'm not certain, as I'm not a surveyor.

The holes can always be filled, faired & painted, once you're satisfied that the problem, if any, has been cured.

- Idea #2 is to hire a surveyor, & or talk to one by phone or online. In particular, one who deals with multis. Ones of your make & model if you can find one. Including contacting the manufacturer for recommendations (both on surveyors, AKA who to hire or talk to, & courses of action).

- Test various areas of the sterns with a moisture meter.

- Talk to folks who do non-destructive testing, & ask them whether they could determine the level of water ingress via audio gauging (kind of like ultra sound, but used to determine metal thickness & damage assessment on metal boats).
I mention it, as obviously the density of any cores or glass will be different than that of water, so it may work.

When talking to the same folks, ask if using thermal imaging equipment is an option for the same reasons as the above suggestion. I may be able to find a link for this somewhere, I'll look.
And odds are that they'll have some other ideas as well. The only question is is how pricey will they be?

- Get a set of the blueprints, & layup schedule for the area. They'll tell you loads about what materials are where. And also give you an idea where any quantities of water might pool, if there is any in there, in quantity.

- If you REALLY worried about water, like paranoid. Especially given the blueprints, you could peel/grind off the entire layer of exterior skin in that area, check for water, replace cores as necessary, & re-laminate, seal, fair & paint.

There are likely more options, though in reality, most likely a good series of test holes will tell you most of what you need to know. Knock on wood. And they're fairly easy to repair if naught shows up. Plus, if things are wet, but the core doesn't need replacing, they'll assist with the drying process.

For info on composites, there's the basics @ the WEST System site, & Epoxyworks magazine. Plus loads more online, & also via Professional Boatbuilder magazine.
Another site which comes to mind is Composites World. And you might try your luck posting on this over on BoatDesign.net There's a fair bit of educated knowledge over there.




FYI to the OP. I'd be REAL careful, and likely avoid putting solvents in there, because if there's foam cores (particularly structural ones) a lot of solvents will eat/melt the foam. And then you wind up with an even bigger problem.
I'm not referring to alcohol, just to be clear, it's relatively benign, knock on wood.

[olaf hart]

You could lift the boat up until it is vertical, and just let it drain out ......

[UNCIVILIZED]

Here's a link to another type of non-destructive testing. Can't say for certain if it'll work, but it can't hurt to call them & ask.
Shearography - NDT Measurement Systems | Shearography - NDT Systems for Flaw Detection in Composite Materials - Dantec Dynamics

[Thumbs Up]

Mark is right. The entire lower stern steps are filled with flotation foam which is now waterlogged. I recently did a repair on an fp 38, drilled some small holes in the bottom of the hull just aft of the rudder tube and water came pouring out then continued to drip for a week. You do have a foam core in the hull but it is solid glass on the centerline. The ladder on his port stern step had worn a hole where it bears on the nonskid. If this was my boat I would cut a very large hole (most of the top of the step) and get rid of the old heavy nasty waterlogged foam. Dry it out good. coat the inside of the cavity with epoxy, use thickened epoxy to glue the original piece back on and refinish the nonskid with grit and paint. I would leave the floatation foam out, It just adds more weight precisely where you don't want it.

[Terra Nova]

Originally Posted by Sonosailor

...FP Tobago 35 is pedominately a fibreglass and PVC foam sandwich, especially below the waterline...
The boat is sitting in the Virgins on the hard with the rubber removed and the screws out, and the holes spit out salt water from time to time.

Any tricks to removing more water and/or salt before we fill the holes?...

Once water gets between the skins and core, it can be distributed virtually throughout the hull by the panting that occurs while underway. This action can separate the skins from the core. A survey would have found this prior to purchase. The extent of damage can be assessed by a competent surveyor, NOW, while it is in dry-dock.

Imagine the outer skin as a simple bowl; imagine the inner skin as a smaller bowl. As water begins to fill the space between the 2 bowls, it begins collecting in the bottom of the large bowl, first, eventually rising up the bowl until it gets to the point where it had entered (not just to the waterline). To begin removing the water, remove the lowest seacock and thru-hull. If there is a hard-spot, drill through it (sideways) to drain the core.

If a lot of water comes out the thru-hull opening, you will need to penetrate (from inside) the inner skin, at the lowest point, to vacuum out the remaining water. It is unlikely you will ever remove all the water. The damage has been done.

[UNCIVILIZED]

Originally Posted by Terra Nova

Once water gets between the skins and core, it can be distributed virtually throughout the hull by the panting that occurs while underway. This action can separate the skins from the core. A survey would have found this prior to purchase. The extent of damage can be assessed by a competent surveyor, NOW, while it is in dry-dock.

Imagine the outer skin as a simple bowl; imagine the inner skin as a smaller bowl. As water begins to fill the space between the 2 bowls, it begins collecting in the bottom of the large bowl, first, eventually rising up the bowl until it gets to the point where it had entered (not just to the waterline). To begin removing the water, remove the lowest seacock and thru-hull. If there is a hard-spot, drill through it (sideways) to drain the core.

If a lot of water comes out the thru-hull opening, you will need to penetrate (from inside) the inner skin, at the lowest point, to vacuum out the remaining water. It is unlikely you will ever remove all the water. The damage has been done.

Terra Nova, firstly, what's causing this "panting", that's drawing the water further & further in between the skins & core to occur? As I'm under the impression that core to skin bonds are typically waterproof. Particularly so with foam to glass, where a lot of resins molecularly bond with the foam, as they do to the skins.

Also, do you have links to some articles with the technical backup on this? Because if what you're stating is true, then, essentially, every boat out there with a cored hull has this going on, to varying degrees (for no cored hull is fully 100% sealed). So such an idea is a more than disturbing thought. Particularly given that fact that, with core to skin failures, as you're suggesting, any hull of such a type is HUGELY weaker than one can imagine. Because the beam effect (by design) of cored construction is no longer at work/in effect under such circumstances.

I'd think that such would cause more than a small stir in the marine industry, let alone amongst sailors (power & sail). As when core failures typically occur (be it core shear, or a core to skin bond line failure), then it's common for hulls to flex significantly inwards, in any type of serious seaway or speed.
The most common & news making examples of this being in cored racing yachts, in particular, round the world racers (from the late 70's to date).

Also, how does this apply to hulls built with kerfed (on one or both sides) cores? As with them, there's then the factor of a resin line to skin bond, anywhere from every cm to every few inches. Typically most, or all of the way through the core. Is water which penetrates a hull breaking & or bypassing these bond (lines) as well?

Plus, given that fluids are non-compressible, I would think that enough water would be drawn in between the skins in some boats, to cause skin ruptures or worse. Particularly when boats with this phenomenon fell off of waves of any size. Literally blowing their hulls apart from the hydraulic pressure.

Then there's the question as to, if what you're saying is correct, what is the explanation for boats which have patches of their hull cores, literally dripping wet upon examination? And yet they can have other parts of, or even the majority of their cores, bone dry.
Often times, where it's obvious that some of those wet patches have been wet for years, if not longer. Something which I've personally seen plenty of.

I'm not at all saying that you're wrong, or telling tall tales, just trying to understand this all. That, & I'd think that if this occurring were the norm, then no boat manufacturers using cored construction would be able to stay in business, as they'd be rapidly overrun by warranty claims.

[Terra Nova]

Panting is caused by wave action.

The likelihood of failure is what prevents most prudent yachtsmen from choosing a cored hull. Links? Try Google.