Woodworking 101 thread. Beginner needs help!

Discussion in 'Fiberglass and Composite Boat Building' started by CatBuilder, Aug 7, 2010.

  1. gww25
    Joined: Jul 2007
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    gww25 Junior Member

    plywood scarfing

    I don't mean to muddle the thread but from the pictures that certainly doesn't look like any marine ply I've been using. In fact it appears as if some of the laminations have extremely poor glue coverage. Perhaps that is the root of the problem you're having. Just my 2-cents.
     
  2. CatBuilder

    CatBuilder Previous Member

    Can you expand on this a little bit?

    What do you see that's wrong with the plywood? Again, I'm not yet a "wood guy", so I don't see where you are seeing the poor glue coverage. Can you help out with more details?

    I got it here:

    http://www.boulterplywood.com/MarinePlywood_4.htm

    It's their 3mm and it's made in Greece.
     
  3. tunnels

    tunnels Previous Member

    Stagger a few sheets together with the right amount of spacing at the ends and then Plane them at a 30 or 45 degree angle across with the planer pointing down so the blades wont tear the edges and finish them off with a 36 grit beltsander . Thin sheets just want to bend and walk everywhere by doing 5 or 6 steets at a time its just the last one you have to be carefull with and clamp a thicker piece of ply or wood to hold it !!.
    Logical??:confused:
     
  4. CatBuilder

    CatBuilder Previous Member

    One things I was definitely doing wrong was using the power planer at 0 degrees down the "slope" of the stack. I will try sanding these already fragile ones down to as good as they can get tomorrow (well, tonight... I am working at night). Once this set of 36 is done, I have hundreds more to do.

    I will try on a fresh set with the planer at 30-45 degrees to see if some of the problem was with the uneven surface the grinder left and my holding the planer at the wrong angle.

    I'm doing 36 sheets at a time, actually... :D

    (they are heavily clamped and not going anywhere)
     
  5. tunnels

    tunnels Previous Member

    Ok Use a belt sander with the belt pulling downwards And you woll need a straigh edge like a spirit level to see if its straight from top to bottom as you are sanding . Takes time but will work . ;)
    How do you intend to stick them together ???
    with what and how ??:confused:
     
  6. CatBuilder

    CatBuilder Previous Member

    Charly's Thread covers a lot of it:

    http://www.boatdesign.net/forums/boat-building/kurt-hughes-daycharter-36-a-31846.html

    So does this:

    http://www.multihulldesigns.com/pdf/cm/CYLINDER MOLD MULTIHULL CONSTRUCTION.htm

    Good call on the straight edge! :idea:

    It gets put together like this:

    [​IMG]
    Build the Mold

    [​IMG]
    Lay the Sheets Down With Epoxy

    [​IMG]
    Vacuum Bag Until Epoxy Sets Up

    [​IMG]
    Cut Your Half Hull Out Of Panel
     
  7. Boston

    Boston Previous Member

    you could make the jig out of ply but what it needs to be is straight and I'm not so sure ply would stay straight over that 4' length
    your not going to have to many worries if you use a piece of 1" plate
    granted having a shop cut out the jig might be a pain in the *** but its kinda fool proof after that
    its also mind bending heavy so you will likely be not moving it much other than to wedge it up and slip another piece of ply under it
    thing almost holds itself but we always clamped it
    never did much with ply though
    we made the same thing work for planking and used a more manageable size template and base plate but the concept is the same
    takes about five seconds to plow out a perfect scarf once your on a roll

    best of luck and keep up with the pictures

    B
     
  8. Charly
    Joined: Dec 2009
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    Charly Senior Member

    Catbuilder, I used a hitachi grinder and a makita belt sander. There is a definite learning curve and it is frustrating, but I wouldn't give up yet. The trick is to keep moving the grinder, only let the side of the wheel contact the ply on the down stroke side, and don't take it too far. Do the last bit with a belt sander. It won't be long before you are making perfect scarfs.

    If you have too many ripples, use some drywall screws to pull the sheets all together.

    My sander is a shortie, If I had a choice I would buy the longer one, the three inch wide... it is still light enough not to wear you out.
     
  9. Boston

    Boston Previous Member

    ya but the router and jig has no learning curve
    other than maybe how to not bust a nut lifting the thing out of the truck and into the shop
    its basically fool proof

    why does 3mm sound a lot like 1/8 inch to me
    thats some really thin ply
    scarf length should be ~8" maybe 10" depends but thats one long thin scarf mate
    no wonder your having difficulty with it
     
  10. alan white
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    alan white Senior Member

    This is a difficult subject to address. Woodworking, or any similar hand work, is only partially technique. Much of it is done by the hands and not the head, and training your hands, if you have a knack for it, takes years. so what do you do?
    To a certain extent, you can rely on technique and products alone. This means you let the tool do the job. Of course, scarfing requires either hand skills or a jig and the problem is, if you have trouble with using a Bosch planer (I have one, the $160.00 model), you will also be challenged in making an accurate jig. I would say, for me, using the planer to make an accurate scarf is easy as pie compared to building a jig or using a hand plane.
    The wavy wood has to be clamped tightly in any case.
    Other tools--- orbital? No way. Belt sander? Not the best choice. Router? Better, but it's the jig that's important. without an accurate router jig, forget it.
    That brings us to the butt joint with backer. No scarfing at all. Just accurate set up of the seperate panels, some epoxy, and a plywood cleat (same thickness) reinforcing the joint fron inside the hull. This method is all technique, no great hand skills. It works too, especially well where the panel won't be curved too much (the after topsides of a boat are often nearly straight so that's where to put the backer block joint).
    Phil Bolger, through Harold Payson's hands-on development of Bolger's designs, always specified butt joints with backers or glass tape inside and out and thousands of his boat designs have been built. They hold up, so why scarf?
    Think of a dovetailed drawe, and compare to one that's rabbeted and nailed. Each holds up well. One is more elegant, the other quick and dirty. the difference is really that almost anyone can rabbet and nail a drawer and it will hold up, but not everyone can dovetail a drawer and have it hold up.
     
  11. gww25
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    gww25 Junior Member

    Catbuilder,
    What I was saying based upon the closeup photographs is that it looks as it some of the interior ply laminations are starting to separate from the glue matrix so you're planing over exposed raw edges. Either that or you're planning in the wrong direction and lifting the feather edge of the thin laminates with the plane blade which is why it is chipping.
     
  12. hoytedow
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    hoytedow Carbon Based Life Form

    This will reduce tearout.
     

    Attached Files:

  13. waikikin
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    waikikin Senior Member

    glue line

    "I don't mean to muddle the thread but from the pictures that certainly doesn't look like any marine ply I've been using. In fact it appears as if some of the laminations have extremely poor glue coverage. Perhaps that is the root of the problem you're having. Just my 2-cents."


    Colour of the glue lines dosn't look right for type A bond that we get here in AUS, usually reddish black! The 1.5mm & 3mm are made to BS 6566 (Exterior).6566 which is determined by face veneer finish apparently. Not trying to freak you out 'cos I've followed your forum posts re ply but do your own boil tests, from memory the AUS standard used to be 48 hours, I've tested some ply here that was sold as type A bond that blew the glue line in 20 minutes. theres already some good advice here on the scarfing so I'll leave that. All the best from Jeff.
     
  14. ThomD
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    ThomD Senior Member

    Is this 1088, or doorskins?

    I did the same thing you are working on. You can use a grinder for it. The tool you want is an 8" or 7" sander polisher. This is the tool you see making sparks in a lot of video, except it is reduced to about 1500 rpm. The one I had was a Ryobii, but it probably isn't made any more. The little 4 inch grinders are way too difficult for this.

    The thing with any freehand shaping exercise is that you need to start out as you want to end up. Meaning you want straight lines, you have to start making straight lines or straight passes as you go. For the most part, as you get comfortable with the grinder, you need to watch the wood not the tool. You want those parallel grain lines to develop from the beginning. What would your body need to do to move smoothly, more leg action? What? There is no point in grinding a lot of bumps into the edges, and them hoping to straighten it all out at the end.

    You need to chuck the hard rubber pad it came with and get a level pad of foam, and use a 60 grit disc, or thereabout. Throw out the paper before it gets dull (you should get a lot of use out of it, but chuck it at the first sign of wear). The good versions of the disc and paper come from boat or auto shops, not home depot.

    You have to grind with the far side of the disc so it is moving over the edges in such a way that it can't catch the feathers. It has to be moving downhill.

    With thin ply you have little room for error. I use a hand plane for very fine work that will be edge to edge. But learning to sharpen and use a hand plane is a whole other major skillset. On CMs you have at least one layer of ply under the scarphed one, and there will be glass over that, some modest error is OK, but still it is mms. And the error doubles when you bring the joint together.

    For the CM I used the grinder, but for the thicker ply or individual sheets, I also made a circular saw jig that connected to my vac so the feathered edge would stick down as the circular saw cut it. This worked great. I put pics of this on Multihullforum.

    Also, always differentiate between practice and production. Apparently you don't know how to use these tools. Practice on something non-critical till you do know what you are doing. Maybe get a sheet of 3/4" multilayer ply and grind it, saw it straight, grind it saw it straight, until you can handle the task. Why jump right into it when you don't know what you are doing. Too much pressure. Remember, if you do ruin the edges, it is like 1" saw them straight and try again, after you get some practice. there is a reason why there are golf courses and practice ranges. :) T worst you will have to add a scarph at the end of the panel, not throw out 96 inches of wood, 94 will work also.

    Also, you don't need 15-1 for boat work, the ply usually isn't up to it anyway. You need 8-1. grind those edges back one inch only.

    The scarph is pretty much the hardest part. The CM part is easy, the rest is pretty easy.
     

  15. ThomD
    Joined: Mar 2009
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    ThomD Senior Member

    "Colour of the glue lines dosn't look right for type A bond that we get here in AUS, usually reddish black! The 1.5mm & 3mm are made to BS 6566 (Exterior).6566 which is determined by face veneer finish apparently. Not trying to freak you out 'cos I've followed your forum posts re ply but do your own boil tests, from memory the AUS standard used to be 48 hours, I've tested some ply here that was sold as type A bond that blew the glue line in 20 minutes. theres already some good advice here on the scarfing so I'll leave that. All the best from Jeff."

    They look like doorskins without the real glue. On the other hand, I have used those, and while disastrous delams can occur, they tend not to if the boat is properly finished and well protected. I would use 1088 these days though. Problem is newbies often don't know how to detail boats so they don't later fall apart, and by the time you know, it's probably from some bad stuff. My doorskins boil tested, 48 hours sounds like a long soak in Old Faithful though. Then later while talking over quality checks with John Marples on some other project, he said " oh well they should have the purple/black glue" I had read a lot of stuff about how to test skins, but nobody mentioned the obvious. I had seen lots of exterior and marine ply, and I didn't connect either. None of my doorskins had the dark glue!
     
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