Glued Decking with Beveled Edging Boards

I recently had a lapse of sanity and decided to install dressy glued planking on the seats of my Navigator. Here’s how it went.

Let’s take a look at doing all the fiddly fitting that’s needed if one is installing a laid-plank style deck. One can cheat and simply run the planks off the edge and then trim to fit, but I feel that looks sloppy. For me a proper laid deck – whether fastened or glued – needs edging boards. Those edging boards need to be fitted into every nook and cranny, and of course the places one can use a 45-degree angle are few and far between on a boat. Furthermore, I decided that all those edging boards needed to be beveled together rather than just butted up against each other. I don’t make it easy for myself.

I’d like to illustrate in particular how I went about fitting those bevels. Doing an article on this subject may seem like “well, duh!” but I had to think about it for a while because it was so obvious.

First of all, one needs a surface to work on. I have decided to go with the glued-decking route on the seats of my Navigator. The decks will be painted, as I didn’t want to add much weight, and will probably want non-skid on the decks in the future.

Here’s what we begin with: the underlayment. In my case this is 4 mm plywood glued and ring-nailed down. In the cases of the side and forward seats, this underlayment is the real waterproofing seal for the flotation chambers. (click thumbnails to enlarge)

Next, the edging boards are fitted. I made the edging boards and the decking from Ipe as an alternative to teak.

I have used a bunch of Ipe on this project, and it is extremely tough and durable. It is quite heavy as a downside, so I ripped and resawed my 1x4 planks to 1.5” wide by 5/16” thick decking strips. The edging boards wherever there is an overhang – like the cockpit footwell – I milled wider with a ¾” “grab” lip.

Next, find or make a big pile of spacers. The decking planks will all be set apart with 3/16” spacers for the seam compound to fill. This allows for movement of the wood and just looks good. And we want it to look good. I made all of mine from a chunk of solid white Teflon. They pop free of the seam compound effortlessly.

Fitting any of the edging planks goes like this:
First asses your area. Here we look at the finicky bit between frames at the aft end of the cockpit.

Looking Aft Looking Forward

Then, fit each edging board to the space individually before cutting any bevels. In the above “Looking Aft” picture you can see the aftmost edging board has been fitted around the transom doubler. The outboard end has not been beveled yet. Use those spacers when fitting the edging planks – use spacers to everything.

Fitting an edging board goes like this:

Measure the space – this is the only time I measure. I have figured out that with the spacers I have a little bit of “leeway” in the length of the board, but it’s better to be too long and trim it back to fit rather than too short. My board stretcher isn’t working right now.

Once your planks are both fitted, set them in place. Don’t forget the spacers!

Mark the points that they overlap – both inside and outside corners. I usually try to get the square points on the outside lining up, because they are hard to mark in spots like this. Whatever works.

Pull the planks back out and connect the dots. You now have a cut line if you were going to have a tight bevel. But we’re not, we have a spacer in there.

To get the cut line with a spacer, I just center a spacer on the line and trace it.

Now you have a second cut line. Cut to that.

Now all that’s left to do is drop the planks back in! After the edging is done, the internal planking is easy. I followed the same “trace” technique to get all the angled cuts.

Once All the planks are fitted, they can be glued down. I used Sikaflex 291. I calculated that I would need 6 tubes to glue the planking down and 2 tubes to do the seams. I was wrong. I needed 5 to glue them down and *9* for the seams. Be warned. Buying this stuff at the local yacht shop instead of online because you are desperate is NOT the way to save money.

Most glued decks use screws with washers to clamp the planks down – insert the screws in the seam gaps. With the 4mm underlayment I was not enthused with that idea, especially since there are some areas where the under deck can be seen, albeit with some contortions.

Therefore, I used lots of concrete paver bricks to clamp the planks in place. Gravity is my friend. The Sikaflex 291 gels pretty quickly – I didn’t use the Long Open Time formulation – so take care to apply glue to one plank at a time, set it in place, insert spacers, clamp, and only then move on.

After the glue has set, sand the planks to final smoothness. The Ipe can be splintery on very sharp corners, so I took ran sandpaper down every seam edge to round all the corners off slightly.

Now, it’s time to put in the seam compound. It’s Sikaflex 291, too. Black. Scary, black goop near the finished paint!

Mask everything. Mask the planks. Mask the edges. Mask every surface adjacent to a seam line. Mask your grandmother and your neighbor’s cat. Mask everything. I am not joking about this. If you think “I’ll be careful and not touch/nudge/look at that particular spot,” MASK IT.

This black goop has magical teleportation qualities. As soon as you open the tube it appears on the bathroom floor, the kitchen, and all over your radio. Trust me. Mask everything. Use a very sharp craft knife to trim all the gap-spanning bits of tape.

Now take a deep breath and pump all that black goop into the seams. Smooth it out nicely with a scraper. I found a cheap plastic scraper works well. So does an old credit card cut in half. Wear gloves and do not hesitate to change them frequently. Consider a powered caulk gun, I was wishing I had one. Don’t go more than 2 or 3 seams without stopping to smooth them out, because since the goop starts to gel off fairly soon, it gets very hard to make it smooth.

See why you need to mask everything?

Now, Masking removal. There are two ways to do this. One, do it *immediately*, before the goop gels. This is very stressful because one is panicking about getting wet tape smears on the paint, planks, etc.

Two, relax and let the goop set up for a day. Then come back and run a razor knife down the seams before pulling the tape. It takes more time, but that’s what I ended up doing. Mostly because there was no way I could get all the seam compound in, smoothed, and tape removed in 5 minutes. More like 5 hours to apply and smooth the goop.

Finally, give your planks a nice cleaning to take off the last of the sanding dust. Apply oil or finish if you’re going that route. I’m not, these are bare planks. The dark areas have had a swipe of cleaner but not the whole plank yet. (This is the area that taught me about Masking Everything, so I needed to clean up some goop spots). Ipe gets a very pretty dark reddish brown when you clean or oil it.

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