BYYB Forums

I now know why I took a sabatical from building lol. All the bloody sanding!
I was wondering, I am still on the wood level, I am filling and sanding low spots and high spots trying to get the surface as smooth and level as possable, switching from woodflour to talc was a good thing it makes the sanding much easier, but still, the sanding is a biatch with all the burcitis and arthritis I have developed over these last years.

  So I was wondering would bondo (I know) its a bad thing on a boat but I was wondering, ???  under the glass, on the wood itself, would it still be risky? If so I will stay with epoxy and keep my heating pad warmed up.
But if it will work it may save me a few bottles of aleve (which does not work)

Also, Any other ideas woud be perfect as well, It is good to be back on the boat now going onto 3 weeks steady sanding and filling digging out screwes that were showing a bit redrilling and countersinking new ones.

I am only working on the deck so far, and only on the left side. when I made up my mind to start back. I was like, where do I start? So I just figured pick a spot (lol ).
So, I began at the front of the cabin and worked my way around cabin and deck all the way to the lazeret.

I plan on glasing the top first, as it would be easiest for me, Once I complete all the sanding.  I figure a roads only as good as it's base, So if the deck is smooth it will decrease the number of air bubbles in the glass "I'm guessing".

I also plan on cutting out my ports, and my lazeret hatches either this weekend or very soon.
I am going to make two of them like Keith did on whipoorwill, It makes it nice for access, and does make sense as in the plans the hatch is on the only support for the two deck pannels where they meet in the middle.

Brian:  I used phenolic microballoons mixed with resin for fairing.  Sands really easily, and gives a very smooth surface.  Much easier than silica or even wood flour.  West System makes some, as do others.  You might give them a try.


Dave

If you can get to the epoxy before it sets up all the way, a cut glass scraper will take it down real fast and smooth.  I got mine from my local hardware store which cut them from left over bits of glass for next to nothing.  Otherwise a cabinet makers scraper will do the same if you sharpen it all the time. 

I used a little bit of bondo on my weekender above the water line and under the glass.  Yeah, you will get lectured, but don't let it get you down. Right now I am re-doing the interior of my cabin, and I am using bondo over some of the little oopses I left in there.  Oh-oh I'm going to get it now.  I just figure that for those who don't know what arthritis feels like, forget em.

Anyway, if you can figure out a way to scrape instead of sanding it will save your joints.

Al

I used Bondo directly on the wood the way the Stevenson video shows.  Ten years later, haven't had a problem.

Bill

Bondo will work to a degree on well encapsulated surfaces, because it can't absorb moisture from the wood. If sealed from above with epoxy over coats, then you'll be fine (to a degree). The problem with Bondo or other polyester automotive fillers, is they don't stick well to wood, epoxy or even itself. They also absorb moisture, which causes it to swell and pop off.

With the average home builder, getting truly sealed and encapsulated surfaces, is often difficult. The usual issues are skimping on film thickness, thinking it's sealed, which lets in moisture, insufficient surface prep (these types of filler need a good mechanical bond) and most commonly, insufficient over coat film thickness protection, to really seal it down.

Once you learn how to make a real fairing mixture, sanding effort drops down significantly. Micro balloons, Q-cells, spheres, talc, etc. make very smooth, easy to sand fairing compounds. Use only enough silica to stiffen the mixture (a pinch or two) and wood flour isn't necessary at all, because it's not a structural application.

Lastly the fairing process is one of procedure, like many things in the build. With a good and established process, you can make a few passes up and down the hull, knowing it'll be fair when you're finished. Most spend absorbent amounts of time sanding unnecessarily. This is particularly true if you use the notched trowel method.

One more tip to easy elbow pain is to make a power "boogie board". Screw a long, thin piece of plywood (1/8" for curved surfaces, 1/4" for relatively flat) to the bottom of a palm sander or better yet a 1/3 sheet sander. It's best if this sander has a switch that changes the pad movement from isolating to in-line. Use the in-line setting and attach a piece of sand paper to the longer foot you've screwed on. Don't use a cushion, just straight plywood. Make a single pass, the length of the area you're working, in one direction, preferably at about a 30 - 45 degree angle to the boat's centerline. This leaves scratches in the surface, all in the same direction. Next come back, again the full length of the area at a 90 degree angle, to the first pass. You now have a cross hatch pattern of scratches and the high spots will be identified (they're scratched) and the lows will have no scratches, so you now know where to fill and where to concentrate knocking down further.

Knock the highs down and fill just the lows. Next do the up and back at the opposing angles thing again and see how well you filled or knocked down. This simple technique will keep you working in the areas you need to and not in areas you don't. With some practice you should be able to make three full length passes (the first ID's the lows and highs, the second fills and the third smooths) and have the job done.

DA's and palm sanders (without the boogie board extension) are no use and will make the fairing process worse, not better. Only a long board (boogie board) or an inline sander can fair a surface. The DA and palm sander are smoothing devices, not fairing.

Fairing is different then smoothing. Smoothing is something you feel with your hand, fairing is something you see with your eye. You can have a really smooth, but very un-fair surface. If you polish and wax a dent in a car door, it's really smooth, but not fair. You can also have a really fair surface that's not smooth. For example you can fair a surface with 40 grit paper, but the result isn't especially smooth.

Use the tools and techniques that will produce the result you want. Long boards fair, hand shakers and DA's smooth.

Also:  Don't drive yourself crazy trying to get a surface as smooth and fair as a Bentley's front fender!  Fair it, paint it and sail it!

Dave

Well I suppose i am smothing it then, I have been filling and sanding the screwholes and other smaller bumps and imperfections on the deck and cabin structure.
i have done some small amount of fairing but nothing with a boogy board as of yet. i will use the process though once i get all the small holes fixed, the main trouble is i filled all the holes when constructing, I used woodflour thickened epoxy, so 90% of the holes are filled with that and the other 10 percent and everything since has been filled with talc thickened (which comes off fairly easy).
Sanding these little buggers, millions of them is a bloody nightmare lol.i wish i had thought less is more when I was doing the construction as some of the low spots are slathered in woodflour epoxy lol.
I just came in from sanding, taking some more aleve, and headed back out again.

I do screw holes in two steps. The first is a structural filler, which is hard to sand. I put this in the hole or divot and smash it down with a putty knife, then scrape it flush. It'll shrink a bit as it cures and then I fill it with an easily sanded fairing compound. Some over fill their holes and try to knock them down, but usually you just dig up more area around the raised portion, making maters worse. When I have these types of areas, I don't screw around with them, I just knock them down with a belt sander or 7" disk grinder. I'll mark it with a Sharpie, to note the low spot and wait until the fairing process begins.

Yes Very good advise! i do have a belt sander and a grinder this should work for the bad spots.
thank's paul.

I've found (over the years of creating mounds of sawdust) that once you fill the holes, gouges, joints and all the other nasties, that usinjg a belt sander createes more issures than it cures.  The actual working base of a belt sander is quite small, not much larger than a quarter sheet reciprocating sander.  And since there is no way to actually find the true tangent to the curved surfaces we're trying to fair, we create a more uneven surface most of the time.  Making up the long board using a palm sander as the vibrating tool allows the surface to be sanded over a longer areas and fairing to be accomplished in short order. 
I purchase rolls of sticky back sand paper in 3 and 4 inch widths.  I make my own long boards from 1/8" and 1/4" hardwood plywood, generally birch.    Why hardwood because the layers are more consistent than with softwood and there are far less voids in the hardwood plys.  I attach two knobs or a knob and a handle to either end of a 3 X 24" piece of 1/8" or to a 36"  or 42" piece of 1/4" by 4" wide ply.  If you want the power assist then attach the palm sander about 40% of the way back from the front Knob.  Placing it in the middle didn't give as consistent results as placing it at about 40%.  Make certain that the flat head bolts holding the sander to the board are flus or even a little recessed from the surface.  wrap the ends of the sandpaper up over the front and back edges of the board and tap the sand paper to the board with a flat block and a hammer to get it to stick consistently.  This is another reason for using hardwood rather than softwood.  Better contact and holding power to the board.
Using the long board as Paul suggested at 30 to 45 degree angle running lengthwise and then rotating it about 9 0 degrees off to the other direction will leave you with a nice series of crosshatch scratches with up to about 100 grit paper that are easily seen if yo hold a light to refloect off the surface.  You do not need to apply a lot of pressure, the idea is to identify the low spots and the high spots not to remove a lot of material.
Then mark the low areas by using a pencil to outline them.  Fill with a skim coat of epoxy/micro ballon mix into the low areas only, it won't take much most of the time.  Less is better than more.  After it cures repeat the same procedure with the same sandpaper grit.  I would be using 80 grit at this stage.  Then mark the new low spots with a different color pencil.  and again skim coat them only.  You should now have things pretty even as far as fairing.  Switch to 100 grit or even 120 grit and go over the entire surface again  and then carefully look for any low spots that remain and again skim coat them only. 
Go back over for the final fairing sanding and the surface should now be ready to apply primer/paint or stain/finish.    If you are going to glass over this surface then skip the last fairing/filling step because you will just be wasting time and effort most likely. 
After you glass, I would apply a filler coat of epoxy and micro ballons and begin the fairing process to bring it up to paint/finish level.  You should only require one or at most two steps to be ready for paint.
Most importantly is let the long board to the work, the more pressure you put on it, the less effective it will be.  Avoid power sanding with palm, random orbital sanders and even large pad sanders.  None of them will help make it fair, only worse but smoother.
I see people applying coat after coat of filler/epoxy or other material and then go to work sanding  about 95% of it off.  only to repeat it and end up sanding thru the fiberglass or into the fiberglass.  I've seen some pretty crudly put together boats that still only required minimal filling/fairing to look pretty darned good.  The devil is in the prep work and to avoid any sanding at all on any plywood surface until you get to the glassing stage.  Sanding up to that point will most often result in a lot more uneven surface and a lot more work trying to get it ready for glass.    Sanding off filled screw holes with a belt sander will leave the entire surface around the holes recessed and the rest of the plywood panel needing a lot more work to make it ready for glass or even going directly to paint.