Painting the inside of airboxes

Discussion in 'Boatbuilding' started by hospadar, May 8, 2012.

  1. hospadar
    Joined: Apr 2011
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    hospadar Junior Member

    I'm building a boxy pd-racer-like scow thing with full length side airboxes. It's build from 1/4" underlayment ply which will be glassed over when it's all said and done. I'm wondering if I really need to bother painting the inside of the airboxes, or if I can just leave them unpainted on the inside.

    They'll be accessible from deck hatches, and the boat won't be living on the water, so it seems to me there won't really be a ton of opportunity for water to soak in and stay there.
     
  2. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    Paint over glass or just raw wood? They need to be sealed or they will rot due to condensation.
     
  3. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    If the whole inside of the boxes is lined with epoxy and glass, you can probably get away with just a coat of sealer on the bottom, and say 2" up the sides.

    You wont get away with just a coat of epoxy, without fg, as the epoxy will crack on its own, and allow water into through the cracks.
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Personally, I don't like to paint enclosed spaces, such as inside the planking, lockers, cabinets, etc. It's much easier to catch a problem if you can see the wood. Under paint you have to wait until the whole area is soft from rot, before you see anything.

    This said, lots of places in a boat need to be used and it's often difficult, to see what's at the bottom of a locker, if it's just varnished wood, so paint is a logical solution. White paint can make a dark looking locker, a place where you can actually see what's in it. The same is true of a bilge or under the V berth, etc.

    Many of these places are very difficult to paint after the boat is assembled, so if you elect to paint, do it during assembly. As to air boxes and floatation chambers. It's likely you'll never paint the inside of these again after assembly, so the coating should be especially tough. In places like this, I prefer to pigment the epoxy coatings. Again, I'll use white and this serves to brighten up the inside of these places nicely. The pigmented epoxy will last much longer then paint, assuming it's not going to see much UV. Truck bed liner would be a good choice inside these areas too, though texture and weight can be an issue.

    To directly answer your question, if you use a deck plate or other access lid, hatch or cover, you should consider some sort of UV protection, such as paint, clear coats, etc. This assumes you'll use these boxes as modest storage places too. If you don't and they'll be sealed up except when stored, then don't bother yourself and leave them epoxy coated.
     
  5. Collin
    Joined: Nov 2011
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    Collin Senior Member

    All my PDs have never had any problems with inside the airboxes. I left them in the water all the time--until the Luan delaminated.

    You do know if you epoxy coat the boat, you're going to be doubling the price, right? The epoxy is totally unneeded for a boat that's going to be stored dry. You'll just be adding work, time to build, weight. All for not much benefit.

    There's no reason to overbuild a PD with gallons of epoxy and glass. Nail it together and go sailing.

    If you're worried about the airboxes, I'd just throw some kilz primer in there and call it done. :D
     
  6. rwatson
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    rwatson Senior Member

    For the little bit extra that epoxy costs, it adds years to the boat, and lots more value for resale.

    You spend a long time putting these things together, over and above the material costs - its worth the extra effort.
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I don't think any reasonable argument can be made, for not encapsulating a taped seam boat. The whole concept relies on stable wood, which encapsulation brings to the table. Without it, you might as well use mild steel nails, bath tub caulk and house paint.

    As to the original poster's question, both sides of the debate can be argued with validation, in regard to painted enclosed spaces. Again, I like to know what's going on, so prefer to see the grain, but an unlit, enclosed space can be difficult to see into, so paint makes sense. I don't see the need on a buoyancy chamber, unless it's also used for storage. In this last vain, you can kill two birds with one stone by tinting the epoxy with pigment. It'll lighten the enclosed space, but you'll still see the wood grain, possably the best of both worlds.
     
  8. Collin
    Joined: Nov 2011
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    Collin Senior Member

    Resale? Are you familiar with what a PD is?

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    A puddle duck is a boat most people build in a couple of weeks for $100-$150 and sail for a season or two.

    There's no reason to prolong the life of it. if you keep it under cover, it'll probably last 10 years with no epoxy on it. I've built 5 or 6 of them.

    The bottom is flat and wide. The wear is evenly distributed over the bottom of the boat. So unless you drag it on rocks, bottom protection isn't necessary beyond an extra coat of paint once in a while.

    The exception is the chines. The chines is where all the wear ends up. You should either fiberglass the chines, or add runners.
     
  9. rwatson
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    rwatson Senior Member

    It doesn't matter what boat you build .... the cash price includes a lot of work even for small boats. You cant build a puddle duck for $150 - the ply, paint and sails alone would add up to more than that - I am talking new of course.

    For the little bit of extra work - you can prolong the life, resale value and ongoing maintenance ..

    ... there is no boat that doesn't get knocked around as you finally acknowledged.
     
  10. Collin
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    Collin Senior Member

    I have to fundamentally disagree with you. Puddle ducks are meant to be the roughest, quickest boats to build and sail. Glassing the whole boat is like dropping a corvette engine into a geo metro. Sure, the car will go fast and the engine will last a long time, but isn't it missing the point?

    Fiberglassing the hull doesn't even give you much advantage over a non glassed hull in real-world use. The bottom is so flat that the wear is very even-it isn't like you have to deal with a huge wear spot. The only worry is the chines that get obliterated. That can be solved with some cheap oak 1x2s glued there.

    You can build a boat for less than $100 and that's part of the fun. Finding some old house paint and some 2x4s to rip apart is where you save the money. They're so ugly and rough, people make fun of you for it.

    If you have $500+ to drop into a build, you can build a 12 foot boat people would actually want to be seen with.
     

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

    The PD and it's several variants are many things. Most are rough and ready things, but there are also many that are quite lavish, so it depends on what you want. I've seen a brigantine rigged duck, as well as those only a mother could love, so do as you like, but there's no doubt in the benefits of encapsulation and a sheathing for longevity and durability.
     
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