Millable Wood Filler?

[KCStudly]

What should I use for a wood filler that can be routed to shape after cured?

My build is a hybrid foamie. I laminated curved wooden rails that will glue into the top edges of the side walls in the galley area. The rails were made up from 10 plys of 2x ripped to between 0.15 and 0.2 something thick glued and clamped over a custom jig form.

Unfortunately, despite my best efforts to secure the slats with the edges all forced flat so that they would all be flush (resulting in a part that would be 1-1/2 inch thick to match my wall foam thickness) they did not cooperate. This resulted in a staggering of the slats with highs and lows on each side and a slightly thicker than planned overall width. I can plane (or sand) them back to the 1-1/2 inch, but there will still be tracks of low areas following the arc.

I'm not so worried about the inside surfaces as they only need to be flat and will be covered by the inner wall skins (5 mm marine ply). However, the outer surfaces need to be flat so that the canvas and glue covering looks smooth and even.

The problem, and reason for reaching out for help, is that I also need to route the recess for my hatch seal into the upper outside corner of these pieces. My gut is to use a millable filler to make the outside smooth first, then route the seal groove as I would have done if the part had come out perfectly. (In hindsight I could have used wider slats and planned on planing them to final thickness after gluing, but the temptation to use readily available 2x lumber was too easy to succumb to.)

What ever I use for a filler will need to accept glue or paint so that the canvas can be adhered.

1. My first thought was body filler, but I don't know if it can be milled/routered; don't really feel like doing a test if someone with experience can say they have had success or failure doing this.

2. My second thought was to mix saw dust and TB2. That should be pliable enough to mill, but could be gummy (I have no experience here).

3. Then there is wood filler, but I don't think it is intended for this and don't think it would have the integrity to hold an edge.

4. My next thought was to plane them to the proper thickness, then mill the rabbet for the seal, and then fill any remaining areas that did not get routed away. It could be that the seal rabbet is shallow enough that the outer slats form the edge, and only the inner slats where the worst of the misalignment occurs need to be filled. (Will need to look into the specifics in more detail.)

Here are some links to the parts of my build where I built the rails - It jumps around a bit back and forth to other things and some OT stuff, but I tried to link to the areas that show the rails being made. Unfortunately you can't see the uneven edges of the slats in the photos, but they are there and enough that they will telegraph through the canvas.

Ripping Slats (skip past the trailer pics and OT dance show pics to get to the slat ripping)

Start of Jig Construction (skip past trailer paint touch up pics)

Finishing Jig and First Rail Glue Up

First Rail Out of Mold

Second Rail Glue Up.

[aggie79]

KC -

My first thought would be to plane the lamination rather than trying to fill. I think the glue in the low areas would make it difficult for any type of filler to bond. You probably need to plane down to "all wood". If you're concerned about the overall thickness being less than 1-1/2", perhaps you could plane down to 1-3/8" and then add a perpindicular layer or facing of 1/8" plywood. Then you could rout the channel.

Take care,
Tom

[Larry C]

KC,
I agree with Tom, cut the rabbit first and fill afterwards. I had the same problem with my lamination's. I knocked down the worst ones with a block plane, then I ran them through a thickness planer which worked very well. What still needed filling, I did with epoxy thickened with wood flour. Also, I use Durhams putty for filling voids which works well too, but the thickened epoxy would be better for milling.

[tonyj]

I second epoxy and wood flour. You'll be disappointed if you try doing it with TB2. Just make sure the epoxy/flour mix is fully cured--my experience that 24-48 hrs is sufficient.

[KCStudly]

Thank you all for the replies.

Tom (Aggie79), milling it all flat and then shimming it back out with a piece of ply had occurred to me, but I had struggled a little with the decision to do the laminations in the first place, and after making the commitment to laminations, resorting to cutting plywood profiles after all the other work just seems too much like admitting defeat.

Okay, now you will all truly see what a novice wood worker I am when I ask if wood flour is just generic saw dust that I harvest off of the table saw, etc. or does it need to be fine like sanding dust?

I have a bunch of relatively uniform sawdust that I collected from ripping the slats,

but it is not the fine consistency of sanding dust or general purpose wheat flour (you know, the white stuff used for baking cookies). More like grits or flax seed.

If a fine flour consistency is best, is it a purchased product or homemade? If homemade, what is the best method to produce and collect?

My guess is that what I have here in the bags will do just ducky, but while I have your attention I might as well ask the experts.

Epoxy has two votes and TB2 has one opposed. Gentlemen, thank you for sharing your experience.

[Larry C]

Wood flour is a manufactured product. It is very fine. If you have a Random orbit or palm sander with a dust bag, the dust collected in that bag is almost the same. Don't use sawdust, it's too coarse and will just make a lumpy mess. Save your sawdust to mix with paraffin wax to make a great fire starter.
Actually wheat flour can be used as a thixotropic agent to thicken epoxy. There are many other thickeners available for epoxy. I mentioned wood flour for you application because it will make a smooth and strong filler. However, don't expect the nice tan color of wood flour or the dust in your sander bag to stay that color when you mix it with epoxy. It will turn dark brown unless you control the color with other additives. Also, it will be difficult to sand, so put it only where needed or you will have a lot of extra work.
If you don't need the structural strength of the epoxy/wood flour mix, consider Durhams putty, it works pretty good too.

[KCStudly]

Thanks for the input Larry. I looked up the Durham's "Rock Hard" putty and it had some precautions against using it for thinner coatings. Sounds like it is intened more towards hole filling.

I will look for the wood flour on the next trip to the hdwr store and I think I still have some epoxy from another project.

Thanks again.

[Larry C]

Thanks for the input Larry. I looked up the Durham's "Rock Hard" putty and it had some precautions against using it for thinner coatings. Sounds like it is intened more towards hole filling.

I will look for the wood flour on the next trip to the hdwr store and I think I still have some epoxy from another project.

Thanks again.

I think the precautions about thin coatings is referring to large flat smooth surfaces. I have used it for years to fill cracks, dings, dents,and voids. I am using it on my build to fill the voids between inner framing and foam in my sandwich walls. I have found it sticks to foam even better than it sticks to wood. I have some spots on foam that are spread out micro thin,and I can't get them to pop off. I think it is a great product for many applications. It would be especially useful for "fairing and filling" foam on a Foamie before final covering. However, it's not in the same league as epoxy for structural applications.

$.02

[KCStudly]

Excellent first hand experience! Can't beat that kind of feedback. This forum is the best.

Sounds like it might be a better alternative to the light weight spackle in many uses, especially for filling gaps.

Thanks again.