Flats Boat Rebuild

Discussion in 'Fiberglass and Composite Boat Building' started by chads7376, Mar 17, 2016.

  1. chads7376
    Joined: Mar 2016
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    Location: Brazoria, TX

    chads7376 Junior Member

    Hello all,

    I am new to this forum and I'm posting in here to hopefully get some advice on my build. I posted in another forum with zero luck on advice.

    I bought this boat a year or so ago with the intentions of rebuilding it. Had I known it would be this labor intensive I'm not sure I would have tackled it but I'm in too deep now. So here it is... I'm just going to post some pics of what Iv'e done to this point and then throw a bunch of questions out there. Hopefully gain some sound advice from the folks that have done this stuff before.

    Before

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    All the next will my start to current.

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    [​IMG]

    What I found when I cut the deck out...

    [​IMG]

    [​IMG]

    This stringer held a bunch of saturated foam so i cut it out, removed the foam and reglassed it.

    [​IMG]

    [​IMG]

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  2. chads7376
    Joined: Mar 2016
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    Location: Brazoria, TX

    chads7376 Junior Member

    Continued

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

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    [​IMG]
     
  3. chads7376
    Joined: Mar 2016
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    Location: Brazoria, TX

    chads7376 Junior Member

    Here is how the boat is now...

    [​IMG]

    [​IMG]


    So I ran into a big issue I believe. When I'm walking on the boat while its upside down it feels like there's some "soft" spots if ya will. It's obviously too late to reinforce it from the inside since I already have the deck glassed back in.

    One of my questions is: can I put a layer or two of glass on just the bottom to make it a little more rigid? If so what type mat or cloth would you recommend? If I can do I need to sand all the way down to glass? I'm pretty close to me glass now as you can see in the pics. Mind you everything I have done to date has been with polyester resin based products.


    [​IMG]
     
  4. chads7376
    Joined: Mar 2016
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    Location: Brazoria, TX

    chads7376 Junior Member

    Next question: Is there a flexible easily sandable filler I can apply to the sides of the boat?

    There is a slight indention/crease down both sides from what I believe to be from the wet expanded foam pushing out on the lower sides of the boat. I have block/file sanded one side of the boat trying to smooth this out but it still has some low spots.

    I tried to capture the issue in a picture. Below you can see the crease just below the old pin stripes.

    [​IMG]
     
  5. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    Well it's a little to late to say you should have replaced the foam. Hopefully the chamber under the sole is watertight and will keep the boat afloat if it swamps. But to answer your question the hull is not meant to be walked on, but it really shouldn't be a problem. I wouldn't add any glass to it. It won't make it significantly stiffer. Actually the foam probably added some stiffness to the hull. On a flat bottom like that the longitudinal stringers inside the hull should provide plenty of stiffness. This rub strips on the bottom now are really just there to provide abrasion prevention. They really don't add much to the stiffness of the hull.

    What I would do is add a couple of strips of oak or some other hard durable wood to the bottom. Two would be enough. Plus they will make the boat run straighter (directional stability) and if you make them about 2 by 1. The 2 inch is the height not the width. You can encase them in fiberglass that extend about 2 or 3 inches either side of the strip. That will hold them to the hull and add a little more stiffness.

    But Frankly, if it were mine I would leave it alone. I don't think it's a problem.
     
  6. chads7376
    Joined: Mar 2016
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    Location: Brazoria, TX

    chads7376 Junior Member

    Thanks for the reply Ike. I really don't want to worry about it but my issue is its very soft compared to everything else on the bottom of the boat and it's right under where the saturated stringer was.
     
  7. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    The foam in that stringer was what gave it it's strength. that is a typical hat shaped stringer. The fiberglass is there basically to hold it to the boat and prevent damage to the foam. It does give it some strength but mostly it comes from the foam. Of course when then foam gets saturated it loses most of it's strength. So removing it was OK. The question is what did you replace it with. But as you said to late to do it now.

    Maybe some of the other folks here can make a few suggestions. PAR? Any ideas how can he stiffen up the bottom of this boat from the outside?
     
  8. chads7376
    Joined: Mar 2016
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    Location: Brazoria, TX

    chads7376 Junior Member

    I would agree about the foam, however the other stringer had no foam in it. The stringer that didn't have the foam feels solid. It seems like the water that was held in that foam for so long some how compromised the integrity of the fiberglass.
     
  9. chads7376
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    chads7376 Junior Member

    I didn't put any foam back in it. I didn't want the headache of wet foam later down the road if some water got in there again. I installed two drain plugs down there so I can check for water from time to time.

    I asked the "to foam or not to foam" question on another forum and was told by several that it shouldn't effect the structural support of the hull without it. So I chose to leave it out. I understand that there will be no flotation should the boat capsize. I'm not real concerned about that. I don't go anywhere deep enough that I couldn't recover it should that happen.
     
  10. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    Well I have given it some thought. If you really want to stiffen it up but keep it as flat as possible you could do the following. Get some 6 or 8 mm marine plywood (8 would really make it stiff but 6 would be almost as good. BS1088 is the best but since you are covering it up and it is rather expensive you may want go with a cheaper grade. If you can't get marine ask if they have MDO. It's used for signs in very wet conditions and is already coated with resin. If you can't get anything else a really good exterior grade will do but make sure it is the best exterior grade you can get and put a lot of coats of resin on it.

    You may have to scarf two pieces together to get it about the same length as the stringers inside. Sand the hull down to the fiberglass so you get a good bond between both the ply and the glass. Coat the plywood especially the edges with resin. Saturate the edges as much as you can because if any water gets in it will rot the wood. Run the piece from the transom forward between the transom cutout and the rub strip. From your photos that appears to be where the stringers are located.

    Then glass the wood to the bottom over where the stringer is or as close as you can. For balance do the same to the other side. Now it should be stiff enough to bounce a bowling ball off of it, but you will still have a flat straight running surface. It won't add a lot of weight either.
     
  11. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    You could use a hole saw and drill down from the deck or from down from the bottom of the hull (depending on if the boat is right side up or upside down) and then put some 2 part expanding foam in there, then patch up the holes.
     
  12. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    That would work (why didn't I think of that). Use two holes on either end and that would definitely make sure the stringers got filled. Then just glass over the holes.
     
  13. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    It would probably take more than 2 holes in that long, small diameter space. The liquid is thick and has a tendency to not run very far, as soon as it starts expanding it slows running, then stops and can then block itself. It will keep expanding and can force stuff apart or make it bulge.

    I would drill at least 3, probably 4, maybe 5 holes, and then go from the ends towards the middle or from 1 end towards the other in small batches, making sure expanding foam always has an escape route. You don't want it to become trapped and bulge out the weak bottom or rip the tabbed on stringer from the inside of the hull. If it's trapped and keeps expanding it also ends up denser and heavier than it's formulated for.
     

  14. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The best way to do this is spray it in. It's easier than it sounds. Mix the foam in a 5 gallon bucket and quickly install the lid. The lid should have a schrader valve, previously installed. Immediately pressurize the bucket. The foam doesn't need a lot of pressure and it'll come out of a hose bib (also previously installed) on the bucket bottom. Another way is to use a garden hose attached to the mixing bucket. Mix the polyurethane and let it flow through the hose, through a hole and gravity feed it (the hose) backwards, as the foam exits. The foam will stay fairly liquid in the hose and expand as it exits.

    Sam is correct, it need to expand naturally, which is why you feed the hose up to one end of the contained area and pull it back to the entry hole as it flows out. The entry hole needs to be pretty big to let out air or you can drill additional holes.
     
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