DIY fairing boards

Discussion in 'Fiberglass and Composite Boat Building' started by Scuff, Jul 30, 2020.

  1. Scuff
    Joined: Nov 2016
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    Location: Richmond VA

    Scuff Junior Member

    I've made two sanding boards and a board to spread fairing compound. I used a batten down the middle on two of them to try to get them to lay fair to the hull. I posted pictures. I think the two with the battens work pretty good. The fairing compound board is .025" spring steel and the sander is 6 mm ply.
    Anyone else want to share theirs?
     

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  2. Heimfried
    Joined: Apr 2015
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    Location: Berlin, Germany

    Heimfried Senior Member

    I attached two handles on my board, so I can apply more pressure when sanding. The plywood board is lined with a firm foam rubber sole (ca. 2 mm thick, blue in the pic). It works well, but I had to change the sandpaper fixing clips shown in the pic, because its grip was not firm enough. Instead I use now a piece of a small steel u-profile with screws.
    k001.jpg k003.jpg
     
  3. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    I am using flexisander, but disappointed in the abranet mesh. I modified the sandpaper and use about 10 sheets of festool papers.

    This gave me the idea that anything can be made into sanding boards with velcro.

    I use the inside of pvc pipe; like 1" for doing radiuses. Cut about in thirds.
     
  4. Scuff
    Joined: Nov 2016
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    Location: Richmond VA

    Scuff Junior Member

    Heimfried, where are you sourcing the thin foam from? I think that would be worth trying to see if it improves my results.

    Fallguy, the flexisander video was how I came up with using the spring steel for applying the fairing compound. Are you using the air operated version?

    Thank you both!
     
  5. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    My go to board's are foam coring for fairing and soft foam from a toss down kneeling pad for smoothing. I like the thickness so I can grab them anywhere along the board.
     

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  6. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    no air, but the festool papers are kicking abranet's arse on cutting power
     
  7. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    Here's one of my favourite fairing tools..
    Jeff.
    upload_2020-8-2_12-22-50.png
     
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  8. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Works well on wood.
    Less so on composites
     
  9. fallguy
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    fallguy Senior Member

    try that on glass for an hour
     
  10. waikikin
    Joined: Jan 2006
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    Location: Australia

    waikikin Senior Member

    Haja,
    I try to leave the reinforcing fibre there to do it's job & do the fairing in the fairing compound. Ifn I'm gunna chop some glass down it's Zec discs and the soft pad to finish, just part of the arsenal. Sometimes I wish someone would steal all my sanders so I don't need to be doing that:)
    Jeff.
     
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  11. Heimfried
    Joined: Apr 2015
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    Location: Berlin, Germany

    Heimfried Senior Member

    Sorry, no source that could help you. It was kind of packing material when my marine plywood delivery came. It was laid under the plywood batch to prevent it from slipping. That's all I know.
     

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  12. sailhand
    Joined: Jan 2017
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    Location: australia

    sailhand Junior Member

    I use a guide coat for everything, if your not using a guide coat its going to take a lot longer and be more expensive than it otherwise would be. You must also really like sanding if you dont use a guide coat and by some gumboots so you can paddle around in all that bog dust/money thats laying on the floor under your job.

    The next step after your first bog is a jack plane for the ridges and lumps. A block plane then for finer work. Planes are great because they cut fast and no dust at all just fine shavings. You can get rounded and curved hull shapes pretty fair running the plane on different axis to suit the shape usually +- 45. By now at least half my guide coat is gone so I'm about halfway there and not a hint of dust. Next comes my helicopter blade on a big sander polisher, you must keep it moving in figure eight type movements as I do with pretty much all my sanding tools to avoid digging any hollows in your work.

    Now I am 90% there and its time to fill the hollows which are easily visible as they are grey from the guide coat and contrast really well with white bog, the white bits are almost perfectly fair by now. I fill slightly proud with a good quality plasterers broad knife, usually 6 inch, unless I have a really large area and then I use a trowel. I use one edge of the broad knife hard on the fair/white part of the hull and slightly raise the other side a millimetre or two over the middle of the hollow to get a slightly proud patch. Now possibly a touch with the block plane and then a quick helicopter or longboard on the patches.

    Then its high build and guide coat number two and torture board time. I like plain 12mm mdf as its a particle board and less likely to warp from grain in real timber. Our local hardware in aussie, bunnings, will slice it into 110mm wide strips for free and you are good to go. I use cheap lightweight gyprock/dry wall plastic sanders and simply glue one each end of the board for handles, lightweight and simple. I use various length boards and smaller ones have only one handle. I check my boards with a metal rule to make sure the are straight and then velcro. I always store them flat on a flat bench or on the job to keep them straight.

    The art of a nice fairing board for me is a rock hard straight surface with the thinnest velcro I can get, like the thin velcro on most sanding pads. I want to cut the highs and leave the valleys. I find any sort of soft rubber padding allows the paper to be pushed into the valleys and you really dont acheive much except make the bog thinner everywhere. You cut the lows as well as the highs so your just moving the ripples closer to the hull. You create a lot more expensive hard earned dust to paddle around in but achieve little else. I just want to cut the high parts down so straight and hard boards for me work the quickest by far. Its really minimal torture boarding and you know as soon as the guide coat is gone move on, its fair. I like the figure 8 type movements and progress in one direction, say bow to stern, and cover the panel vertically by moving the figure eights up and down. I will also do a light 45+- to make sure. Time for primer and another guide coat. I use a black quick drying paint misted over the job or commercially available black powder type guide coats which are basically ready to go immediately after application. A quick long board and the guide coats gone, just scratches and small marks which really stand out as they are dark from the guide coat. I use a product that panel beaters use called glazing putty, nothing to do with windows, that I get from panel and paint supply shops. Get the right colour putty to suit your top coat. I used highbuild thickened with qcell until I became allergic to it. The guide coat tells you when your finished, otherwise your guessing. The experienced guys might get away without it but Ive yet to see anybody acheive fair hulls faster without using a guide coat.

    A final note, if you are fairing and you hit glass then stop immediately, and move on. That is a hill that you shouldnt cut down its the structure of your boat. You need to build the rest up not cut the glass down. A good indication that you have the minimum amount of bog on your job is that you just touch the glass in one or two places. If you keep sanding after that you are just making hollows, wasting sandpaper and bog, not to mention shoulder muscles and lungs. Put enough bog on to cover the job and then start fairing, if you hit glass stop sanding and move on. It just means you will have more dark hollows full of guide coat to fill. If you dont hit glass anywhere then youve probably got a bit too much bog.

    I generally build fair, that means not too much bog and torture board. Fairing battens are your best friend and will save you heaps of work later in the job. I forgot to mention my fairing batten that I use for fairing. When I am at the jack plane stage I have a nice aluminum extrusion 25x25mm box section with sharp edges , not rounded, and it bends in a nice fair consistent curve. I have various lengths that I use up to around 3.6 metres for hulls. These are great to just press up on the job and spot your big highs and lows. You can then jack plane these down in minutes dust free, and your half way there. Old sail battens do a reasonable job as well, aluminium flat bar works for tighter radius hulls.

    Good luck, stick to the rules and dont chase out hollows when your sanding and you will get there a lot quicker with a lot less work.
    Cheers
     
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  13. sailhand
    Joined: Jan 2017
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    Location: australia

    sailhand Junior Member

  14. Barry
    Joined: Mar 2002
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    Barry Senior Member


    the easy way
    And there are many air or electric powered flex sanders for doing curves. The second vid shows a guy doing a boat

    have to like the vacuum
     

  15. Scuff
    Joined: Nov 2016
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    Location: Richmond VA

    Scuff Junior Member

    Sailhand I second the use of a guidecoat it has worked for me too.

    My sanding boards still don't match the curve of the hull like the spring steel bog board does. I'm going to try some foam like Heimfried. My first hull is faired putting on the seal coats now. I did 7 or 8 fairing/guide coat sanding cycles before I thought it looked ok. Definitely going to focus on fairness of the mold for the next two.
     

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