Finishing Problems, Need Help

Discussion in 'Wooden Boat Building and Restoration' started by nbehlman, Sep 3, 2017.

  1. nbehlman
    Joined: Aug 2011
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    nbehlman Junior Member

    I am in the process of finishing my mahogany runabout. My plan was to use stain, epoxy and poly in that order. The stain went on fine and I put a layer of epoxy on. I went to sand with 320 grit and I sanded right through the epoxy and the stain (see picture, it looks awful). I tried putting stain over the bare spots, but it won't take. What do I do now? Is there any way to repair this or do I just sand it all down and start over. Even if I start over, I'm not sure what I would do differently other than just leaving out the stain. For reference I'm using west systems epoxy and Behlen solar-lux stain. Any advice is appreciated.
     

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  2. Mr Efficiency
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    Mr Efficiency Senior Member

    It looks like you are going to pay for the "sin" of sanding back into the wood. Was that specified, the epoxy coat ?
     
  3. nbehlman
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    nbehlman Junior Member

    Not sure what you mean by "specified." It was my idea.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    I doubt you needed epoxy, it has poor UV resistance, and under a clear coat of PU, should have been omitted I'd say. You hate to have to sand that off, it simply won't sand evenly either, what with the wood and the epoxy not having the same hardness. How much of the boat has been sanded ? Stuff-ups with clear finishes are very difficult to rectify, unfortunately. And this one made more difficult by the stain.
     
  5. PAR
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    PAR Yacht Designer/Builder

    I agree about not needing epoxy, though is an ongoing argument in the industry. My defense is the epoxy just adds to the maintenance chores on a brightly finished surface, so its use needs to be qualified somehow. All brightly finished surfaces need special attention, care and upkeep. This means you'll have to repair and redo the finish periodically. This is why I don't recommend epoxy, as you'll have to repair it too, unless there's a need, such as a sheathing or to physically toughen the surface of softwoods, etc.

    This is also why I don't recommend polyester finishes either, you have to repair them, which is much more difficult with this particularly coating. Varnish is a pain to apply well, but is easily repaired and touched up. Yeah, it takes forever to dry and doesn't last as long as polyurethane, but you have to be quite skilled to repair and touchup polyurethane, compairtivly.

    As to what's next, well I think you know. The epoxy has sealed the pores of the wood, so you have to knock down below this point, which may be tough inside those seams. I usually like to kill two birds with the same stone and tint the raw wood epoxy sealing coat. This gets the color on and seals the pores in one shot. I've had to do what you're about to cry over and it sucks. I'd recommend a light enough sanding to remove most of the color, followed with a healthy, yet carefully scrape job. If you scrape the surface, the blade will shear the cellular structure of the wood, which makes for a far superior surface then the fuzzy strands left behind by a sander. A scraped surface also takes finish much better too. I feel your pain man and it looks like a fine job you've done so far. The finishes are always the part that makes grown men cry hard.
     
  6. nbehlman
    Joined: Aug 2011
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    nbehlman Junior Member

    I'm in the process of sanding the boat back down. I'm concerned that the stain won't cover uniformly due to some invisible spots of epoxy. Let's say I stain it again and go straight to polyurethane. Won't I have the same problem where I'm in danger of sanding though the poly and the stain again? I am considering forgoing the stain entirely at this point. I don't have any confidence I'll get perfect results on the second try.
     
  7. jorgepease
    Joined: Feb 2012
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    jorgepease Senior Member

    Don't sand so hard once you get the poly on. You are just getting rid of the nibs and scuffing it up to get ready for the next coat. Barely put any pressure and don't hold the machine on any single area for long. You can even do it by hand very lightly, though Im surprised you went through the epoxy that easy with 320.
     
  8. PAR
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    PAR Yacht Designer/Builder

    Do yourself a big favor and read up on finishing wood bright. There's lots of texts on the subject, including my site. It's all about process and procedure (prep), more than the products.

    Yes, it's possible to have some goo remaining in the pores of the wood after sanding, which is why I suggested a good scrape afterward. Pour water or thinner onto the surfaces, so you can find still sealed areas, before committing to a finish. With bright finishes it's 90% prep, 10% actual brush in hand time. You need to be "sure" and there are ways to check this, before splashing on the goo or clear stuff.
     
  9. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    As you have just found out wood stains art extremely difficult to repair. PAR is correct that strait varnish is the easiest to maintain and touch up.
    My advice will rub so against the grain, but has stood the test of my twenty plus years of furniture making experience.
    Don't try to change the color of wood with stain: stain is useful to eaven out the natural color of wood. Scrapping is best if done properly. Sanding with grit finer than 150 usually clogs the wood"s poors with damaged but still partially attached fibers. Slightly thin first coat of varnish. Apply when wood is cooling not heating to avoid bubbles. Immediately Gelcoat with unthinned varnish. Sand with 220. Three back to back coats of unthinned varnish. Wait a week for everything to dry completely. Sand and repeat three coats. Wait, sand and one final coat.
    Sand and one or two coats annually. Sell boat in yen years when everything must be removed back to raw wood.
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    I guess it depends on how his first coat raises parts of the grain. If getting it level for the next coat can only be achieved by cutting back to the wood again, in parts, it presents a problem if the colour of the substrate has changed, by the cut exposing unstained material. I'd have more likely just used one-pack very lightly tinted to get a shade you like, rather than the stain. But the surface roughness that develops in parts after the initial coat, no doubt varies with timber species, and coating.
     
  11. PAR
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    PAR Yacht Designer/Builder

    At this point I think he needs to fix what he's got, rather than what should have been done. I'd be inclined to sand, then scrape, then use a chemical stripper with a ScotchBrite pad to remove the stain and start over, maybe using oxalic acid to even things out. This is a fair bit of material removal, so work slowly and deliberately, so you only remove what you need to. A chemical stripper will help get down into those seams too. Use thinner to identify areas that might become blotchy and sand/scrape some more, to eliminate the problem spots. Once satisfied about the nature of the now (again) raw wood, seal it, then apply a stain if desired. Once the color is acceptable, it's time for clear coats. On boats, clear coats are divided into two segments; the bulking coats and the finish coats. The bulking coats simply apply film thickness, after an initial "tie" coat that is bonding to the substrate. This is usually thinned a bit.

    The next few coats (3 minimum) are to add film thickness, that can tolerate some smoothing and sanding. About 1/2 of this will be sanded away, while you flatten the surface from brush strokes or spray stipple. Again, more bulking coats, until you've filled the grain, sanding every few coats, to flatten it. Once you've smoothed and flattened the surface, the finish coats go down, with each being deliberately applied thin and "flowed" into place. This "flowing" thing is a feel you'll develop for applying varnish and very difficult to describe. Lightly sanding between each coat it insure tooth. Applying varnish and/or clear coats can be a bit of an art form, so read up and do some practice first. Manufactures will tell you only 3 coats are necessary, but this isn't protection, just a tease in the marine environment, which will not last a year, at least in my harsh subtropical climate. I consider the minimum 3 bulking coats and 3 finish coats, but this is just the remotest bare minimum. 9 - 12 coats is more usual and easier to "refine" the finish (sanding, buffing, polishing, etc.). When I do show boats, the coat count usually rises into the low to mid 20's, because you remove so much in the smoothing and flattening stages.

    Don't be scared or disappointed, we've all been there. Study up some and a little application practice, will help a lot in your next round. Consider this a dry run for your fantastic finish job. When it's gleaming next to a dock, with everyone wishing they could own a boat as magnificat as that, none of them will know how much time, you spent in the moaning chair crying in your beer.
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    Well, it is the first coat most likely to cause problems, as the OP can witness. I'd say if the sanding of the first coat is unavoidably going to expose some points of bare timber, then staining had better be deeply penetrating, or it will be spotty in appearance. The smart thing to do before working again on this, would be try plan B first on a sizeable piece of scrap material, of the kind the boat is built of, to see if there are no nasty surprises. Clear coats on timber in climates like where PAR lives ( just about identical here in Queensland) are for the birds, imo, no matter how good you do it, constant sun exposure causes greying and loss of "freshness" of the timber. But CT (Connecticut ?) and with only occasional use, and kept well undercover, probably not a real problem.
     
  13. nbehlman
    Joined: Aug 2011
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    nbehlman Junior Member

    I spent about 5 hours sanding with 80 grit and got the deck, transom and port side back down to wood. The worst part was definitely the aft rub rails. I still need to do the starboard side. I'll go around with some mineral spirits to see if I can find the spots that still need more sanding. After I get the boat finished, I plan to fill the gaps in the deck with Silkaflex 295 UV, so I'm not too concerned about having a little stain and epoxy down in the gaps. When I did the stain, I was surprised how dark it was. Much darker than the Chris Craft look I was going for. It was darker than my test piece, which was weird because I used a scrap piece of wood from one of the covering boards on the boat. I will either buy a different stain or just forgo it altogether. I'm leaning towards no stain at all. I'm a little traumatized from the whole experience. The epoxy went on with kind of a stippled texture, so I was trying to sand it enough to give the next layer something to grab onto. Clearly that was too much. Next time I'll just scuff the surface by hand.
     

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  14. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Yes. Light hand sanding is key until sufficient thickness is gained. Leaving raised grain stubble is preferable to damaging the stain. Why I don't recommend staining is that the focus changes into how to protect the stain instead of how to protect the wood.
     

  15. messabout
    Joined: Jan 2006
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    messabout Senior Member

    There seems to be a limited number of craftsmen who know what a proper scraper is. One of those evil things with a red handle, that you buy in the hardware store is not the tool for doing fine work.

    A good scraper consists of a thin piece of sheet metal, preferably spring stock or at least a metal with some temper. I'm not talking about the side of a tin can here. The scraper is sharpened by deliberately turning over the edge so that it forms a bur. The bur will be razor sharp and the scraper, with a little bit of practice, can shave a micro thin bit of wood. Luthiers and makers of fine furniture use these things. You can buy the scrapers from places like Grizzly and/or tool suppliers to the furniture building and re-finishing trades. Every boat builder needs an assortment of scrapers of that kind. Sure saves a lot of sandpaper and does the work faster on certain materials or finishes.
     
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