Determining Level and use of wood flour for fillets

[Doug Cameron]

I have been kept out of the shop by a shoulder operation with the Core Sound 20 stitched up and ready for fillets. So I'm getting ahead of myself and reading and re-reading the plans and staring at the boat. I have a couple of questions:

1. How do you determine fore-aft level?

2. Develin writes that wood flour is the only proper thickener for fillets because the epoxy will fun out of a Cabosil mixture. Any input?

Thanks, and happy new year.

Doug

[Bud_Wilson]

Doug C I beleace Develin's is rite Bud

[Brad]

1. The page titled "Hull Interior Construction Plan" shows the DWL 30 1/8" below the top of the bow and 19 1/2" below the top of the transom. I subtracted the transom from the bow and put the bow 10 5/8" higher above the floor than the transom.

2. I used the 2/3 wood flour and 1/3 cabosil mix Devlin recommends. The cabosil in the mix seems to make a smoother fillet than wood flour only.

[PAR]

Fillers are many, but understanding their properties is key. Some materials add bulk, others thicken the epoxy and some products (like wood flour) do a bit of both. Wood flour is a fine fillet filler, especially on the reasonably easy radiuses of the Core Sound series. With experience you'll get a feel for the right amounts of material to put in a filler, based on the application, like vertical surfaces under high load or overhead surfaces that will need considerable fairing, etc. I use about a dozen different filler materials, depending on what I'm applying stick 'em to. Most mixes have more then one type of filler material in it. Using wood flour for your structural fillets is a good way to go, but be warned to fair them as best you can while still soft.

[Kidd]

Head the warning about fairing the wood flour fillets while they are soft. Trust me on this. :oops:

[Hirilonde]

I have only filetted and glassed the joints of 2 dinghies but I have glassed over soft/partially cured filets in both cases. I do a reasonably well shaped filet by using plastic spreaders (sometimes cut to shape with tin snips) and learning to stop shaping when it is fair. Too many passes trying to perfect minor flaws in the shape often ends with removing too much material. Small ridges don't seem to matter when you are going to wet the filet and surrounding area out for the tape with pure resin before is is firmly set anyway.

Glass tape over wet filets:

1. saves fairing after

2. saves having to remove blush

3. means a primary or chemical bond rather than a secondary mechanical one

It may not be practical in all cases, but I should do like avoiding sandpaper at any step I can

[Designer]

I like to mix wood flour and cabosil for structural fillets to match the color of the plywood if I am going to finish the inside of the boat bright. Straight cabosil comes out white which I don't care for, on my current project I am using 3 parts cabosil to 1 part maple wood flour for a good match.

I prefer to tape right over my wet fillets because it is quicker, also sanding is not then an issue.

[Charlie Jones]

You might be interested to know that the wood flour you purchase from the Gougeons already has a small percentage of cabosil in it to help make a smoother fillet.

I also do what Graham does- alter the proportions of wood flour/cabosil to get the color I need for bright finishes. Plus I save sanding dust from various woods- teak, mahogany, ash, etc, to add when I need a more suble color shift.

Plus I ALWAYS lay glass tape directly over wet fillets. WHY would you wait for the fillets to cure, then have to sand them to rid them of lumps? Laying the tape into the wet fillet lets you smooth the entire thing with your brush as you go. Has made sense to me for years and believe me I've run MILES of fillets.

If they are non structural and NOT being glassed, then once they set for a bit, I smooth them with a gloved finger wet with alcohol. You can eaasily get a glass smooth fillet like that that needs virtually NO sanding at all..

[Tom Lathrop]

All good advice above but I suspect you may have read Devlin wrong. I will need to check his book because that has never been my experience. I have had epoxy to run from compressed joints where mostly sawdust was used. This was a special case and not to be taken in a universal sense.

[Guest Oyster]

All good advice above but I suspect you may have read Devlin wrong. I will need to check his book because that has never been my experience. I have had epoxy to run from compressed joints where mostly sawdust was used. This was a special case and not to be taken in a universal sense.

Saw dust releases epoxy from its mixed filler more than any other filler on the market.