How to Tell if Foam is Wet or Okay???

Discussion in 'Fiberglass and Composite Boat Building' started by thill, May 10, 2012.

  1. thill
    Joined: Mar 2007
    Posts: 82
    Likes: 2, Points: 0, Legacy Rep: 26
    Location: Virginia, USA

    thill Junior Member

    I recently picked up a nice little center console that has a soft floor, but is in otherwise good condition. One thing I noticed is that the drain hole ALWAYS drips water, so I suspected wet foam under the floor.

    Today, I pulled up the back half of the decking to discover that the center of the boat, between the two stringers had no foam, but was FULL (15" deep) of water, and the drain hole was plugged with debris. I unclogged the hole, and water has been draining for about 20 minutes, and should finish as I type this.

    The cavities on the outside the stringers are filled with pour-in foam. Each block of foam is perhaps 24" wide, 12" deep and perhaps 10' long. It is quite solid on the surface, (no denting when walked on) and appears to be in good shape.

    1. How can I tell if the foam is saturated and needs to be removed, or if it's okay?
    2. Any idea of the cost of new pour-in foam, here in Virginia?
    3. It better to fill in with slices of that blue foam they sell in the building supply stores?

    Thanks in advance!

    -TH
     
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 488, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    You can pull the foam completely and just cover the bilge spaces again, or you can put some foam back in. An air filled cavity works slightly better then a foam filled cavity as buoyancy.

    In either case, it would be wise to provide a way for the bilge to drain out the transom hole. Most boats don't do this and they become waterlogged. This means weep hole at each athwart support, so the water can roll aft to a drain.

    Yes, the blue foam will work, but again it's not necessary. The manufactures are required to install it, but you don't.
     
  3. tunnels

    tunnels Previous Member

    no foam is best !!

    :?:If you make a air tight cavity make sure you have a exspansion hole or in the hot weather it will grow in size with the heat . or it possible to make a automatic drainer ! a plastic pipe going to the lowest point up through a hole and a foot higher than the chamber with a turn down at the end . As the air cools it will suck into the chamber as it reheats during the day the air will force any water from the lowest point of the chamber up the tube and out . Tube only has to be small 3/16 or so !! will always be empty and dri !!make sure the tube is sealed around at the top of the chamber !!. Let nature work for you 24/7 :)
     
  4. thill
    Joined: Mar 2007
    Posts: 82
    Likes: 2, Points: 0, Legacy Rep: 26
    Location: Virginia, USA

    thill Junior Member

    Par and Tunnels,
    Thanks for the replies! This boat has a pretty smart design. The stringers actually have a couple of glassed-in "arches" in the bottom so that all the water is released completely. Water spreads across the whole bottom of the boat evenly.

    I just went out to check, and the hull is completely dry inside, with only a couple of "puddles" on top of the foam to tell that the hull had been full of water. I pushed on the foam at the bottom, thinking water might squeeze out like a sponge, but it only felt damp, with no liquid squeezing out of that spot. That seems good!

    My big question is: So is there any good test to know if it's waterlogged? Should I look for seepage, or is the push test in various locations enough?

    This is a saltwater boat, and the Chesapeake Bay can get nasty at times, so for safety, I'd want some type of floatation. It's too open under there to realistically seal it up. Maybe a bunch of empty Clorox bottles or sealed milk jugs with fill-foam holding them in place? Something light, but that would hold air? Let me know what you think.

    Thanks.
    -TH
     
  5. thill
    Joined: Mar 2007
    Posts: 82
    Likes: 2, Points: 0, Legacy Rep: 26
    Location: Virginia, USA

    thill Junior Member

    "No foam is best"

    HMMMM... I have to think that one over. I like the empty bottle idea, with a little foam keeping them in place. They are very light, and even if the bilge is full, they will still hold air. Have any of you tried this method?

    -TH
     
  6. mydauphin
    Joined: Apr 2007
    Posts: 2,164
    Likes: 53, Points: 48, Legacy Rep: 575
    Location: Florida

    mydauphin Senior Member

    You can tell if foam has water by its weight. If the foam is not sealed and water gets into it it can stay humid and rot the wood around it. It can add many pounds of weight for no reason.

    I know this personally, foam between fiberglass and wood leads to rot. Make sure it is sealed, and that compartment can drain or ventilate.
     
  7. DCockey
    Joined: Oct 2009
    Posts: 5,008
    Likes: 500, Points: 113, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    An idea not based on experience so take it for what it's worth: Take a "core sample" of the foam by driving a thin but stiff wall metal tube into it with the end of the tube sharpened, or bore a hole into it using a wood auger in a brace (not an electric drill so you have better control) and examine the chips.
     
  8. thill
    Joined: Mar 2007
    Posts: 82
    Likes: 2, Points: 0, Legacy Rep: 26
    Location: Virginia, USA

    thill Junior Member

    THAT is my problem... I can't tell if it's sealed or not. If I crush down on an edge (that had been underwater for quite some time, at least) I don't get any water squeezing out. But it DOES seem "humid" or "damp". At least it did an hour after draining the water off. I guess I need to check again later today.

    But it's sounding like I should remove the pour-in foam either way, to prevent future rot. Then I need to find another way to add floatation.

    Is there anyone who contests this idea, or is this the course of wisdom?

    Thanks!

    -TH
     
  9. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,301
    Likes: 996, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Some bum advice being bandied around here, plenty of people have gone down into Davy Jones' locker thinking air cavities are as good as bouyancy foam. They certainly are not.
     
  10. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 488, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Ridiculous, compartmentalization is precisely what keeps all but the smallest of boats afloat. Yep, foam can displace water in a breached compartment, but it also means the compartment is useless for anything else. Only the smallest of craft use foam and if the compartments are well sized, no problems if you go looking for icebergs in the north Atlantic. The average pleasure boat holing is a rock or log at speed. You have a localized crack or hole and a few cubic feet of compartment fills. This isn't much more then bringing along an extra cooler full of beer. So, how much foam do you think is employed in a Nimitz class and where would the aircraft and fuel live if you tried?
     
  11. mydauphin
    Joined: Apr 2007
    Posts: 2,164
    Likes: 53, Points: 48, Legacy Rep: 575
    Location: Florida

    mydauphin Senior Member

    After years of removing foaming from around gas tanks (that leads to their corrosion), causing fires(the cheap stuff burns like gasoline), water logged boats, and rotten wood (fiberglass gets damaged by being soaked all the time), I think it is better of not using it at all.

    I would use air pockets, multiple compartments and the correct amount and sized bilge pumps, proper deck drainage. Most small boats go down because of being overturned, or crashes because of pilot errors, not because they got mysteriously swamped.
     
  12. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,301
    Likes: 996, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Hulls are not unknown to split and admit water to more than one air tight chamber, thereby often upsetting the boat because the chambers are commonly along the sides of the hull. I take the view that the boat has to be wholly stable, and able to make headway if it's hull is breached, failing that being practicable, you need a self-inflating liferaft to accommodate all aboard. Anything else is roulette.
     
  13. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 488, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    You can't prepare for every eventuality, though some have tried. The discussion here is a full plane powerboat, in which case the foam in question will reside below the sole, likely compartmentalized in the stringers and sole support system. If you run over rocks at speed (or what ever), slitting open the boat half her length, breaching several compartments, expecting to:

    is simply impracticable, nor an eventuality that has a significantly high enough percentage, to consider it's implementation, in all but the smallest of boats. You just lose way too much internal volume to make a marketable product.
     
  14. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 148, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    Push the probes of a multimeter in the foam and read the resistance. Any other value than infinite tells you the foam is wet.
     

  15. richg99
    Joined: Sep 2009
    Posts: 4
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Houston, TX

    richg99 New Member

    I don't know much about foam vs "sealed air", but I sure like the idea of the capped bottles held by a small quantity of sticky foam. Seems to be a good mid-ground.

    The under deck areas in question are not "storage areas" normally, anyway. Rich
     
Loading...
Similar Threads
  1. rwatson
    Replies:
    8
    Views:
    3,191
  2. blackhawk999999
    Replies:
    6
    Views:
    1,040
  3. CBTerry
    Replies:
    13
    Views:
    1,589
  4. midcap
    Replies:
    6
    Views:
    2,648
  5. tunnels
    Replies:
    24
    Views:
    5,203
  6. tunnels
    Replies:
    13
    Views:
    11,646
  7. H180DSC
    Replies:
    1
    Views:
    1,404
  8. Jaco
    Replies:
    6
    Views:
    217
  9. Mark C. Schreiter
    Replies:
    24
    Views:
    727
  10. Midday Gun
    Replies:
    10
    Views:
    365
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.