Sanding, Sanding, effing Sanding

Builder's Forum
1

Hi all,

I realize this topic has probably been covered a gazillion times in the forum, but I find the search feature a little lacking.  Sometimes I get better results from the builders forum by putting my search directly into Google.

But alas, I stray from the topic.
I am prepping my Annapolis Wherry for painting and varnish and resigned to the hours of sanding I am facing.  I understand I am trying to achieve a consistent uniform cloudy sheen on the epoxied surfaces.  However the challenge I lose more often than not is to do this without sanding into the wood or the glass.  And in the case of wood, then having to re-epoxy.  

I can usually get to the point of having most of the surface consistent with a few pin-prick type of depressions (picture 1).  But then going a little further puts me into the wood (picture 2).  
I also have a particularly hard time with the fillets, as mine are irregular and contain nooks and crannies which are hard to get the sanding pad into.  Using the scotch brite pads helps a little but not much (picture 3).
Quesitons:
1) does leaving a few pin-pricks cause a problem (say less than 1% of the surface area)

2) If I can eliminate the "glossy/shiny" spots, but it is not quite a uniform cloudy sheen, is that sufficient?

3) Any suggestions for handling fillets?

 

2

Well, there's always paint, which I believe is God's gift to falable boatwrights (or maybe boatwrongs) with which to graciously cover they're failings.  Some of us hold that, as far a boats are concerrned, as opposed to, say Martin guitars and Steinway pianos, varnish it a tool of the devil, straight from the workshops of hell, meant to enslave mankind by his own vanity to perpetual toil and disappointment.  <;-)

But, of course, "different ships, different long splices" as the old sailors' adage goes.  I'm sure Laszlo's excellent advice will get you closer to museum grade finish, if that's what you really want.

.....Michael

3

   Again, you get to go for the level of perfection in finish that you desire, but from your pictures things look about at the point where I'm satisfied and ready to move to varnish.  Varnish won't hide the filet imperfections you show, especially as sanding those areas is hard to accomplish and you can end up with "varnish on, varnish off" and still be sanding back to epoxy, but the filets don't look bad as is, and remember that when the entire surface is all gloss (or you can topcoat with satin varnish), they won't be so noticeable a looking at sanded v. unsanded areas.

And about the little "pinprick" areas: remember you have a number of coats of varnish to apply, and the varnish will tend to fill the pinpricks as you sand between coats, just a a slightly lower rate than epoxy coats, because each coat of varnish is thinner than each coat of epoxy. But the varnish is much easier to sand.

One hint if relying on varnish to do the final filling of the minor blemishes - try to rough up as much of the pinprick or depression (or any still-glossy area) as possible with a scotchbrite pad prior to each coat of varnish. The varnish coat (epoxy too, for that matter) tends to want to thin out over the gloss surface and stay thicker over the roughened surface, thus you get better results filling the pinpricks/glossy areas if you can knock off most of the gloss across the entire surface, pinpricks and lower areas included.

4

   MIxed up pictures 2 and 3 in original post, but you probably got the point.

5
  1. A few pinpricks won't sink your boat
  2. Lack of uniformity at that level is only a cosmetic issue. Whether you continue on to achieve it is up to you and the type of finish you want.
  3. Use dowels, scrap wood, pieces of foam, etc. and sandpaper and adhesives to make custom sanding tools that can get into the spaces over the fillets; or
  4. Apply a thin layer of whatever fillet mix you previously used over the existing fillets to fill in the depressions. Note that brushing uncured fillets with a brush dipped in unthickened epoxy will smooth them right out. Some builders use a gloved finger dipped in denatured alcohol but I'm paranoid about avoiding contamination.

When I'm finishing a boat I use lots of thin layers of epoxy instead of a few thicker ones. Fewer drips and more economical. I was using 3 ounces per coat of epoxy for an entire WD12 and applying it with a roller, tipping it with a foam brush.

Try applying only in the areas where you have the pinpricks and sanding only where you have applied new epoxy. Save the overall sanding for when all the pinpricks are gone. Put on a couple or 3 very thin coats between the sanding and sand lightly. Use a large sanding block so that it doesn't just slide into the depressions and deepen them.

And most importantly, use a really good quality sandpaper (not Home Depot or Lowes) that is sharp enough to cut the epoxy and will stand up to heat and pressure, Store the paper in airtight boxes, possibly with some dessicant if you live somewhere humid. Don't be afraid to change it much sooner than you would if sanding wood. As soon as it stops cutting, change it.

Good luck,

Laszlo

 

1 Like
6

   Thank you Laszlo!  I fee like you (and other regulars) have been answering my questions for the last 20 years.  I believe it is a large reason why CLC boats are popular and successful; the great support available on this forum.  Your contributions are greatly appreciated.

7

I too got tired of chasing perfection on my Petrel play, and at some point its time to get the boat on the water where it belongs. Your boat looks good at this point, so stand 6 feet back and see if you can really see problems. With a few imperfections left in a couple off places on the deck, and impatient to get paddling, I used a suggestion by Nick Schade and others to take the gloss off the final coat using a very fine scotch pad type abrasive. The slight imperfections and tiny dimples are nowhere as visible as they were under a perfect(?) gloss finish. This to my mind is better than using a satin varnish which will probably permanently leave a slightly cloudy finish. And if the imperfections start to bug me I can always console myself with the idea I will spend time next winter re-finishing the deck.  

8

As a neophyte I was also struggling a lot with fillet cleanup.  I eventually figured out for myself that strategic use of cabinet scrapers helped me get to a point I was satisfied with.  I may or may not be using the cabinet scrapers as they're intended to be used, but what I figured out for fillets was to use the various different curves to scrape across the fillets, as can be seen in this photo:

https://flic.kr/p/2qqNuVv

Here are the fillets after I reached the point where I was reasonably satisfied:

https://flic.kr/p/2qqNuVq

I started with the more curved scraper edges, then switched to scrapers with less of a curve as I progressed.

For me, scraping gave me finer control than sanding, and it's nice to have a break from the epoxy dust.

9

   If you want better looking fillets one option is to go over them with a microballons plus epoxy mixture.  Sand the fillets sufficiently to roughen them.  Then apply a thin (say 1/8" layer) of epoxy thickened with microballons (make a thick paste that holds its peaks)   The microballons will fill most of the defects in the fillets and are super easy to sand once they harden

1 Like
10

Getting good clean fillets is an art I am trying to learn. It's so much easier to do it well when laying them down than it is to sand them clean later.   

 Fillets:

  1. Make a filleting mixture rather than just using wood dust. I use the formula of  2:2:1 of West System 407:406:404 additives. The goal is to have a mix of good workability, appropriate viscosity and yield strength, and sandability if you have defects. There are other formulas  I am sure. I use pure wood dust only for fillets that will not be visible in the final product. YMMV
  2. use a filleting tool of appropriate radius. CLC sells a set but they are also easy to make. I mostly use a couple of different sizes of popsicle sticks.
  3. Use the filleting tool consistently to "plow" the fillet and leave the excess on the stick and with separated little mounds on each side of the fillet. If you have the mix of additives done right the fillet body will be smooth and will require no further work. Resist the urge to mess with it any more if at all possible. 
  4. carefully clean the two mounds off with clean up sticks sharpened to a chisel edge. The leave it alone to cure. 

I have found that doing it this way removes the need to smooth the body of the fillet with your finger, and eliminates most sanding. I learned this technique from Russell Brown's video series on mastering epoxy over on https://www.offcenterharbor.com/. Unfortunately, it's paywalled but for me it was totally worth the price of admission.

1 Like