Fillets Fillets Fillets!

Builder's Forum
1

So I finally got around to doing my first fillets on my Sassafras 12.

I feel like I did OK, but I don’t love the aesthetics:

https://imgur.com/a/DDeWpmc

I had a lot of trouble figuring out:

  • What depth & width to make the fillets;
  • How to work the mixture around the curves of the bulkheads; and
  • How to shape the fillets in general.

I ended up reworking them quite a bit while the fillet mixture was curing.

How do I know if they’re smooth enough for the interior fiberglassing?

Can I sand them down a bit?  And then try to layer on some more fillet mixture to try to even out the shape?

Any advice on fixing up messy fillets?

 

2

First, look in the Shop Tips section of the CLC website. Lot of good info, specifically:

05: Epoxy Work - The Gluing Part of Stitch & Glue Boatbuilding (video)

Pastry Bags for Epoxy Fillets

While CLC's methods have been successfully used by thousands of boatbuilders and will result in a very nice boat, over the years I've come up with variations that suit me better. I find that I can build lighter and cleaner with less sanding and the tools suit me better than pastry bags and wooden spatulas. When in doubt, do what the manual and CLC say to do, but if you feel adventurous try:

Building a Wood Duck 12 - Interior fillets & glass

In answer to your specific questions:

1. Yes, you can sand fillets but you really don't want to. It's a lot of hard work. If they've already cured, you're stuck with it, though. The time to smooth them is before they've cured. Painting them with a chip brush dipped in unthickened epoxy leaves them smooth as a baby's bottom.

2. Covering them with more fillet material to smooth them out is a done thing. It's known as a cosmetic fillet. The only downside is the added weight and expense.

3. Take a scrap piece of fiberglass and gently pull it across the fillet. If the glass snags the fillet is too rough and needs sanding. Ideally, the glass should be applied before the putty has cured, while it's still soft.

4. The rounded putty knife gives the fillet the correct curve and depth. As the angle between the wood pieces changes, the putty knife's height changes, causing the depth of the fillet to automatically adjust. For glassed fillets using up to 6 oz glass, the putty knife should have the same curvature as a nickel.

5. The flat putty knife is used to scrape the ridges from each side of the fillet. Some folks use blue tape to prevent the ridges from forming; put down tape on each side of the fillet, lay down the putty and pull up the tape to get rid of the excess.

Hope this helps,

Laszlo

 

3

   @laszlo - indeed, if i ever build another boat, it will not involve smoothing fillets!!  that should be a red warning page included in the manual.  there were a few times in the last weeks where i wanted to give up and trash the whole thing.  

4

Your post was a few days ago, so hopefully you haven't gone much further, but in my experience, those are going to need to be sanded a lot, and it's going to be painful to do it, so you're probably going to want to practice (screw two boards together to create a joint you can practices fillets).  Pick a tool that you're going to use to do them and practice using that.  You want the edges to be a smooth transition to the wood on both sides, and it shouldn't be chunky or rough in the middle.  I am saying this as someone who has spent hours and hours sanding messy fillets from the beginning which I can now do so much better after a bit of practice.  I did a few cosmetic fillets because it was less pain than sanding, and in certain cases that may be what you want to do.  Of course it's possible to sand everything down and make it nice, but it's really a lot of work vs making them smooth with a tool in the first place.

5

Now that Gramps added his response, I think those rasps are a great idea.  I ended up using 60 grit sandpaper wrapped around varying diameter dowels (or sockets from a wrench kit) to knock down the high spots.  The most difficult spots were in the corners, and if I were doing it again, besides being much more careful, I would definitely experiment with a ball rasp on either a power drill or a hand drill to clean up the corners, I spent hours there with my finger and sandpaper when there was probably a simpler way.   

6

   We found a set of riffler rasps to be handy for working down the ugly fillets.  Got a set from CLC, but I see they no longer sell these.  Amazon has 'em, or something similar:

https://www.amazon.com/SE-7408WFR-8-Piece-Heavy-Riffler/dp/B001110K6Q/ref=sr_1_1?crid=2TLTYXHSDGJNA&dib=eyJ2IjoiMSJ9.nCXHQdCh6CrLv_uEbJnGJeTt8k5cEOI8-uTU3xIlgqk3Snkb-jFbT7Mgf5ok6LDPOW62540vD3HWe4XIPoukAjDgLb79Usro-U8nzwEN4ncwJ8lBf2zfUf7_7_VaOgkjLO0ExYCkmnwUConGI7Zc_Un_eL0PAYW6_39vlfd8vRBRxQL0MTaGVOiyYLuU5UmypZkOXTvAfvCZxD8mVeNYqMgQAEgEjat450z9GHFUM-i47kBrNGSNZ8Fcq2p27-3oJcV-F0zvF6Mr3YGYSX3CCHTzZMuZO7-yaoiiRHSpkRk.JUcW_Jw9xLoef-b9ASOUnJk840pg8sjjUQFpnD4aEuc&dib_tag=se&keywords=riffler+rasp+set&qid=1729272413&sprefix=riffler+rasp+set%2Caps%2C183&sr=8-1

...and an internet search will turn up similar things from other sources.  It's still some hard work, but much faster than sanding.  Eventually, we learned to smooth things out better while the epoxy was still workable with denatured alcohol on gloved fingers.

7

 

8

Those rasps are nice. I bought a set when CLC still sold them. But keep in mind that they're sort of a one-use tool. Not that they aren't durable, but after the first boat you either learn your lesson and make neat smooth fillets by coating them with uthickened epoxy or denatured alcohol while they're soft or you give up and get out of the S&G boat hobby altogether. I have yet to hear of anyone suffering through smoothing fillets on one boat and then deciding to do it again a second time. I know I haven't had to use mine since 2008.

Laszlo

 

9

  If you decide to sand, consider a drum sander that fits into a drill.  Choose a diameter that matches the shape that you want the fillet to be. You can add a flexible extension to be able to get it flatter to the seams and wear a good glove on the guiding hand.  Takes some practice but it does work on lumpy bumpy fillets. You can tape on each side if you worry about the sander going off course. 

10

You do want to be careful about using power tools with little rotary ball rasps or grinder bits to deal with a gnarly epoxy fillet.  While I was the owner, project manager, and chief engineer of our Passagemaker build, I was more a boatwrong than a boatwright.  My younger son and his son, my most frequent helpers, were the real boatwrights.

Anyway, at one point I became frustrated with a particularly stubborn rough patch in a big fillet up near the bow transom, and I put a ball rasp in the drill and went to town with it, thinking, "You're mine now, you stubborn beastie!"  Well, of course, the tool got away from me at one point and made a divot in the adjoining plank, which I can still see, though it is mostly masked by the paint.  No serious harm done, but I was afterward forbidden to come within 10 feet of the work area with a live power tool in my hands by the boatwrights.  "Gramps, you are a genius, but you ain't got fingers...they are, in fact, spare thumbs!"

<;-)

11

   I use painters tape by t o outline filets

12

   I use painters tape by t o outline filets

13

   I use painters tape by t o outline filets