If you want to smooth the existing fillets, you're already doing what needs to be done. It does take forever and it does suck.

You can trade time for fillet thickness and weight by applying a "cosmetic" epoxy/woodflour fillet on top of the existing rough ones. When you get the cosmetic layer on, let it firm up a few minutes and brush it with a chip brush dipped in unthickened epoxy. This will smooth out the new epoxy and when it cures you'll have a smooth surface.

If you're painting instead of varnishing, you can make the cosmetic fillet from epoxy thickened with phenolic microballoons. This is much lighter than epoxy/woodflour, but looks like hell under varnish. It really works well painted, though. Also, microballoons are very easy to sand.

Here's a boat that had horrible thick rough fillets the got the microballoon cosmetic fillet treatment.

I wouldn't try the heat gun, though. The heat will make the epoxy soft and gooey, not liquid. It won't reflow and smooth out.

Good luck,

Laszlo

Thanks! I see that CLC sells rounded rasps that could help smooth before adding a thin layer of expoxy and a little sawdust mix over top.  Some of the chunks in the thick epoxy beads I have now take forever to sand. Do you think they would be useful?

I'm at a point on my Waterlust where I'm confronting this issue myself.

Years ago I was gifted a Foredom tool, basically a motorized tool-holder on the end of a flexible cable. Hand piece takes different collets for different tool shank diameters so your range of tools is wide. The 1/2" OD drum sanders work well with 60-grit sanding bands, and for really coarse work there are steel or carbide burrs that will eat hardened epoxy in no time. A usefull add-on is a speed control however as at full speed these burrs can catch you off-guard in an instant, wreck havoc on much softer okoume or your flesh!

(I'll try & capture a short video this weekend showing how effective these tools are at this challenge, post a link here.)

I've seen various-sized Dremel tools that work similarly over the years and these may offer some hand sanding relief too, at a lower price-point than the Foredom line of tools.

Smoothing fillets is really best done at the 'plastic' phase of set-up. Using your glove-clad fingers dipped in denatured alcohol makes short work of those potential rough spots while they're still soft enough to smooth out but not so soft that you run risk of making things worse than they'd have been otherwise. 

I'm thinking maybe pieces of clear vinyl tube of suitable diameter, wetted with alcohol (or spraying alcohol on soft fillets first) might be useful for smoothing fillets instead of by fingers. Will be trying this soon myself... stay tuned!

   Thanks. Unfortunately I'm past the initial stage so everything is hardened. Once I can get the fillets somwhat smoothed I'll plann on adding a light coat of epoxy and filler and smoothing in with Alcohol as you suggest. That should also help with the edges of the rough fillets where they meet the plywood scraping and sanding there with a thick edge (say 1/16 inch as many are now) tends to damage the plywood if not very careful as I have found from experience.

Kenneth:

By "rounded rasps" do you mean these?

https://www.clcboats.com/shop/products/boat-building-supplies-epoxy-fiberglass-plywood/riffler-rasp-set.html

I have a set.  Wonderful little tools, which, carefully wielded, could help you with your issue.

.....Michael

Dremel tool grinder then larger fillets over the top.  For example, my tack welds had a 3/4" radius, then final, smooth fillets had 1" radius.

���You can get spherical rasp bits for your drill or Dremel that might be good for the first pass knocking down the rough stuff. I have one about 1 inch diameter so good for half inch radius fillets.

Bigger challenge is acquiring skills to avoid having to do much of anything mechanical to get those rough spots taken down. Buncha tools out there to do grinding with if you like collecting hardware!

From my Very Limited Experience with epoxy so far, it's grand stuff that lets you manipulate it while in that 'plastic' stage before it really begins to kick. As in other endeavors, timing is EVERYTHING.

With mechanical approaches, I'm finding there are some places it's nearly impossible to get a powered tool into at the right angle, even with the dentist-drill-like Foredom I'm using on the 'tack' fillets I put in a few days ago. Those rasps might be effective there if'n I had a set. Better to avoid the problem than deal with the issue time and again!

Seasons Greetings everyone! Enjoy your Holidays however you choose to!

A short selection of tools out there:

sanding drum kit 

rotary flap-sanding disc

another drum kit

carbide burrs (rotary rasps)

... but they all need power to drive 'em.

Most well-stocked hardware stores ought to have several items that'd do this same task, certainly the big-box stores to say nothing of what you can find 'on-line'.

Ken,

Back in 2014, like many stitch-and-glue newbies, I didn't pay enough attention to the fairing and smoothing of fillets. I guess it's a lesson we need to learn by doing. Though it's not appropriate for all fillets, some of the larger ones are amenable to fairing with a little more epoxy and wood flour (or cell-o-fill) mix. It's a lot less labor than grinding or sanding,

Cheers,

Dick

Thanks for all the good advice and suggestions from all you builders out there!  Yes, I just did get a set of the hand rasps from CLC as mentioned above and tried them a bit last night. They really help. I also got a rasp drill head for my drill and it helps too.  I'll need something a bit longer to get up into the bow fillets a bit, so I'll look into the dremel.

All the initial fillets were done at CLC during a Wherry class this past September, and as we were working fast to get things done for the next step of assembly, we skipped on the critical step of smoothing with alcohol and since we were all newbies no one mentioned it.  I guess the instructor Geoff Kerr figured that it was more important to get it assembled by the end of class on Saturday morning, than helping us reduce the many hours of cleanup on the large fillets we would be doing afterwards at our homes as a result.  Since he has done this class many times (and built many, many boats) I'm sure he is aware of the extra effort left for us.  Well... I'll never do that again :)

I had the same problem.  It's much better to make them smooth to begin with, but after the fact, they still need to be cleaned up.  I tried all kinds of things.  I decided any kind of power tool was not worth the risk.  Sanding takes way too long, (and too much sand paper) and still risks damaging the surrounding wood.  I settled on scraping the filets smooth with homemade tools roughly the shape of the filets.  I ended up using the rounded end of a hack saw blade.  One or two blades held their "edge" long enough to clean up the whole boat.  It still took a long time, but every time I sail, I'm glad I did it.

Hooper

You would be surprised how much you can do with a heat gun and a scraper or a putty knief you grind down to the shape of you fillet.  

The other option is to use a band file.  That will make very quick work of it but even with very steady hands you will slip up so there will be some gouges that you will need to go back and repair.  For that reason I would not use a band file anywhere near something you plan to varnish.  

This Makita belt sander works great for that problem. It matches the most typical radius that you will want to use

I avoid power tools for this- belt sanders and rotary drums will usually do more collateral damage as they climb out of the fillet and onto adjacent wood. Maybe a little drum on a dremel for awkward corners, but otherwise, no.

My go-to solution for rough fillets or frayed glass fibers or anything that needs sharp edges made smooth, is a 60 grit sanding belt cut into 3 or 4" squares. The cloth backed sandpaper is stiff enough not to need any backing- I can just use my fingers and press into the corner. The belts are also tough enough not to let skewers through into my fingers, but the first pass over a rough patch of epoxy or glass should be done carefully! Those spikes are sharp!

Coarse sandpaper, or belts cut to sections, can be glued to shaped bits of wood if you need leverage and wish to spare yourself the blisters.

If you have some old files (or find some cheap at a garage sale) and a bench grinder you can easily make custom-shaped scrapers for almost any task like working down rough fillets.

  https://youtu.be/T5_ETXimUi4

A StewMac Ultimate Scraper can be a very effective way to scape and smooth the fillets, especially once you get the hang of it.  https://www.stewmac.com/Luthier_Tools/Types_of_Tools/Scrapers/StewMac_Ultimate_Scraper.html

Also works great on the more level, flat surfaces as well.  Think of it as an "epoxy eraser"!

   I built a skerry recently and launched her last October (2019). There are no shortcuts that are better than "biting the bullet" and hand sanding to get the proper smoothness and desired result for a beautiful finish. It is labor intensive, but yields better results. Take your time and do it right. The techniques mentioned above of smoothing fillets with denatured alcohol before they begin to cure reduces the need for sanding significantly.