Masking with packing tape or masking tape?

I see in the instructions and from several posts here that people are using packing tape for masking before applying thickened epoxy. I also have seen images of people's projects where it appears that they are using painter's masking tape.

My experience on other plywood (i.e., not Okume) is that packing tape can peel plywood grains (i.e., raising wood fibers from the surface and effectively gouging the wood). Also I have seen that painter's masking tape can allow bleeding on plywood because of the uneveness of the surface and also the lessened adhesiveness of that tape.

Can I hear from those with experience of masking off joints before sealing with thickened expoxy as to your satisfaction with the method you chose? Should I not worry and use either the little red packing tape dispenser or the roll of blue painter's masking tape?

I appreciate your comments. In fair disclosure I must admit that I have not been able to unpack and inspect my plywood because I bought while CLS had the Oct 31 sale, yet my garage is still overrun from a kitchem remodel that is in progress (and behind schedule - still more experience contributing to my "handle" on these threads).

Thank you.

What Could Go Wrong? (a practical variation of "What, me worry?"


11 replies:

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RE: Masking with packing tape or masking tape?

The BS1088 okoume has minimum peeling, compared with other wood I've used. Sapele peels quite a bit. Bleeding doesn't matter that much when masking the fillets. It's much more of an issue for paint.

If you're really worried about peeling, pre-coat the wood with a thin layer of epoxy a day or so before doing the seams. It's overkill, in my opinion, but it will definitely stop any peeling.

Even though it shows up often in the CLC construction photos, I find masking before applying the fillets to also be overkill. It uses up tape, it's a lot of labor, if you don't get it off fairly soon it leaves adhesive and it promotes thicker heavier seams. It also leaves a ridge on each side of the seam. I've found that I can consistently make thinner seams that are just as clean by using a rounded putty knife to smooth the material into the seam and a flat putty knife to clean up the edges.

So there's some choices for you: a) don't worry, just tape it;  b) pre-coat and tape it; or c) just do completely without the tape.

Have fun,




RE: Masking with packing tape or masking tape?

My experience is different from Laszlo.  I found that packing tape does lift the grain on okoume.  I used 2" masking tape because I had some left over from painting my living room.  It worked so well that I used it even in the ends of the boat.  There was no bleeding, no ridges and it protected the wood from the unavoidable drips you always get when spreading thickened epoxy.  On two occasions when I was using the freezer bag trick, the bag ruptured, leaving great gobs of epoxy on the tape. 

RE: Masking with packing tape or masking tape?

I'm only on my second boat and the first time around I never even heard of anyone tapping before applying the thickened epoxy.  This time around I did see some building photos before building this one but when working on the boat I just didn't see the point.  It is already thickened so it isn't going anywhere and with a firly stiff putty knife I just had to make one pass along each side when I was done applying and it think it looks just as good as anything else I've seen without the time wasted to tape everything.

RE: Masking with packing tape or masking tape?

I used blue painter's tape to mask before filleting. I didn't have any problem with it raising the grain. For masking fillets, you don't really need to smash the tape down with great vigor. Fillets are thick not as runny as paint. It might have taken as much as an hour to put on? Probably less than that, not sure. Not a big deal. Since I filled the little wire holes (extra 15 minutes?), and ran the fillets immediately after masking, the tape wasn't on there for more than an hour or so. It then came off as soon as the fillets were run. I ran the glass tape and painted the entire inside of the hull with epoxy. This all happened in one session, maybe 2 to 3 hours I'd guess. Running the tape and filling it, and painting the epoxy while the fillet is still wet takes out any ridges.

I can see a difference between the bottom and side panels that I taped and the bulkheads, that I overlooked. The taped areas are noticably cleaner, the fillet lines neater. Messing around with a bunch of epoxy is, well a little bit of a mess so the tape can help to control that mess a little. You could be very careful and probably do as good a job without tape but that would slow you down too. Is it worth it? Up to you. Since I am only building for myself, I'm not on the clock, I have no problem taking a a little extra time here and there. As long as I am having fun. If this was a job, and it was someone else's boat, well, that would be an entirely different kettle of fish!


Ogata (eric)

RE: Masking with packing tape or masking tape?

One last thought about whether to mask or not. Masking requires a little more setup time. But the advantage is that running clean, thin fillets is very fast when the fillets are masked. Speed is an advantage when you have bunch of epoxy to get down. Filleting is also one of the messier jobs, the stuff gets on your gloves, on all of your spatulas, trowels and other tools. Little bits drop off here and there. It's easy enough to do without masking, but if you want the job to look neat, I think you'll end up spending enough time fiddling with the squeeze-out, cleaning up the spots etc. that the difference in time invested may not be as great as you might think. On the other hand, if you don't care about neat, how important is it really? Just slap it on there, that will definitely be faster.


Ogata (eric)

RE: Masking with packing tape or masking tape?

As far as my knowledge and experience is concern I always used to mask off the joints before sealing with thickened expoxy with packing tape as if in future if we feel to remove the tape its quiet easy to remove the tape than to remove the expoxy. Plus if I talk about the quality if the tape then I always used to prefer it either from eBay or from That's what I think what you guss feel about this??

RE: Masking with packing tape or masking tape?

  A note about blue masking tape: I used the premium version sold in Home Depot on epoxy coated pieces to mark centerlines with a pencil. After removing the tape and wiping well with denatured alcohol I put another coat of epoxy onto the parts. Wherever there was tape the epoxy just beaded up and refused to flow out.  Whatever they use for adhesive cannot be fully removed with alcohol as I tried again on another piece, this time scrubbing with a wetted cotton towel with the same beading of the epoxy.

RE: Masking with packing tape or masking tape?

Any thoughts about this idea that I found from nemochad on another CLC builders-blog thread? If I read it right, I may need a separate spreader, cut for each different seam angle, but that should be easy and cheap enough. Or maybe even use a few of the yellow plastic squeegees, cut to the appropriate angle and fillet radius.

If it works, it could eliminate both the tape and the after-spread clean up with a putty knife.  Or for a really neat job, could be used along with tape.

"...and better than tongue depressors, is a putty spreader with one side clipped to about a 60 degree angle, and the acute corner rounded to your desired fillet radius. Transfer your non-sag fillet mixture to a cardboard square pallet, and trowel it on, then drag the acute angle along your fillet, leaning the spreader forward and bracing it with your fingers so that the 60 degree sides scrape the plywood clean and push the material toward the center of the fillet.  On the spreader's obtuse corner, you can cut a bigger radius for the flatter joins, and use it the same way."

RE: Masking with packing tape or masking tape?

I've had mixed results with both types of tape, which suggests that it depends a lot on the particular brand of tape and the piece of okume to which it is applied.

My solution is to get the masking tape off as quickly as possible, and remove it very, very slowly. This is kind of hard to explain, so I'll jump straight to an example--if you have a horizontal piece of tape on a wall, the most effective way to remove it is to lift the loose end straight up (or down) in the same plane as the wall. This maximizes the peeling forces on the adhesive and minimizes the stress on the tape. Did I mention going slowly? The harder you pull, the more likely you are to leave adhesive behind.

I've had good luck with 3M-edge lock and no-name plastic packing tape (the high quality stuff is acutally too sticky).

RE: Masking with packing tape or masking tape?

OK, call me Dilbert, but I am having very good luck using post-it full adhesive tape on a roll.  Sticks well, no apparent residue, comes off really easy once I lift an edge with the exacto knife.  Just over $6 on amazon for 400 inches.  I used it for marking spots on the boat that need further attention, marking out the edges for beveling, and marking the alignment of the hull and deck so I get it the same with each wrap.  And of course, for leaving myself notes...

I haven't used it yet for the fillet, but I will try and report back.


RE: Masking with packing tape or masking tape?

When I built (well, still building) my CLC 17, I used packing tape to tape off all of the scarf joints before joining the full length panels - that I would heartily recommend.  The joints came out looking very clean, LOTS of epoxy was squeezed out (first time doing it - I used too much, but better too much than too little!), and it was super easy to squeeze out.

The packing tape did raise the grain slightly when I pulled it off yes, but you're going to sand the entire hull anyway, so what's the big deal?  Now, after the boat is assembled, sanded, and fiberglassed, you certainly can't tell that the grain was raised.  I'm left with just really nice neat joints.

I also taped off the fillets on the inside, and while I guess I'm glad I did this (I guess), my fillets still wound up looking messy.  Having now filleted a boat, I don't know if I'd tape off the fillets again - taking extra care to clean up the fillets, probably with just my fingers, while they're still wet is going to result in the best joints.  At least with fillets, I'm with Laszlo on this one.

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