Cockpit Coaming Rebuild

[John Stone]

Nice job. If I tried to replicate this project the forestry police would arrest me for mis-treating wood products and confiscate my carpentry tools.

Ha! I doubt that. Knowing how meticulous you are I suspect you would do a first class job.

[John Stone]

I helped a friend of mine build a tapering jig a few months ago for his shop. I borrowed it this past week to cut the bevels for the return blocks. The jig made it easy and so much simpler than other ways I have done it in the past.

I want the geometry to be correct but I don't want the fit surgically tight. I need a little room for bedding compound between the return block and the cabin top.

In the bottom picture the return block is just dropped into place to check for fit. I'll glue the return block to the coaming with resorcinol this weekend once I have the ogee cut on the aft end. I'll radius the return block outside corner for a softer appearance and because a curved edge holds varnish better than a sharp corner. The half-dado on the return block protects and covers the vulnerable coaming endgrain. The top ref of the coaming will be covered with a bare teak cap-rail as before.

[John Stone]

With the return blocks out of the way it was time to work on the aft end of the coamings.

I liked the original ogee shape so I decided to incorporate the design on the new coaming. Because the aft end of the new coamings are about 1.25" taller I could not simply trace the design from the old coamings. I drew out some designs and fussed with them a bit. I drew the design on 1/4" ploy then cut it with a jig saw. I sanded and filed the curves till I was satisfied.

I used the same pattern on the aft end of the coaming and cut it wide wide with the jig saw. Next I clamped the pattern on the coming and used a router with a guide bearing to get a smooth cut exact to the pattern.

One of the improvements to the new coaming is to carry the bare teak cap down the ogee. By extended the bare teak cap as such I would have a nice varnish break and the cap would protect coaming when lines occasionally get snagged there.

I used the pattern to trace the design on a 5/4 piece off teak off-cut. I cut the design out with a band saw them smoothed them to test fit on the coamings.

Satisfied, I applied packing tape to the coaming then wet out the surface of the teak ogee that marries with the coaming with thin epoxy. Then I applied thickened epoxy and pressed the ogee into place and left them over night. In the morning I removed the ogee and peeled off the packing tape. This resulted in a near perfect fit without any gaps.

Next I trimmed the ogee down with the band saw to make them about 5/8" tick to more or less match the bare teak cap on the coaming. I used a 3/8" round over router bit to radius the edge. The fit is pretty good. I'll file and sand them to a profile that matches the tail end of the teak cap when I install them.

[John Stone]

Eventually the new teak will grey to match the cap rail.

[Jim Walsh]

Very nice. Sure beats making a steam box and a bending jig.

[John Stone]

Thanks Jim. I steam built our new tiller and that was enough for me. This was pretty simple, though there is a lot of end grain. I do worry a little it will crack eventually. But we will deal with that if and when it happens. In the mean time....I'm looking forward to getting back out there.

[John Stone]

I always thought it exceedingly difficult to sand and varnish the forward inside part of the coaming tucked forward of the aft end of the cabin top. I normally varnish 3x a year so I have been thinking about how to make it easier for a long time. For awhile I thought about painting the recalcitrant area white. But, I came up with what may be a better idea. I'll cover the hard to access area with silicon bronze plate shaped to fit.

I wanted to use 1/16" thick bronze plate but I did not have enough in my bronze stash and no small pieces were available at Atlas Metal. They did, however, have a small off-cut of 1/8" thick so that's what I am using. The side plate will be fit inside a dadoed slot. I'll leave a small amount proud to serve as a cut line for varnish. The end plate fits right on the return block. I'll bed them both with polysulfide or dolphinite and secure them with 3/4" bronze oval head screws.

[John Stone]

I marked the area to be cut and carefully free handed it with a mortising router bit in my small laminate router. Then I spent a while with a bullnose plane and some files till I achieved a fit I was looking for--clean edges and a slightly loose fit so there is room for bedding compound.

I may thin some epoxy with acetone and bush it in the dado slotted area as an added precaution to ward off any water that might get in there.

[Jim Walsh]

That little corner is a challenge. My dodger protects it pretty well but it’s always a difficult spot to sand and coat with your product of choice, as I do annually. The solution you have devised makes the lack of easy access a nonissue going forward. I have noticed other builders eliminated the gap by ensuring their end caps are large enough to fill the area between the deckhouse and the coaming.

[John Stone]

Jim, I agree. Eliminating the gaps by moving the return blocks aft along with a wider block is the best solution--just eliminate the entire recess. I wondered about it during the rebuild but did not have enough experience at the time. I was not sure how to angle the fasteners as the inside corner of the cabin top had to be dealt with which I now know how to do. Live and learn.

In the mean time, I drilled for two fasteners for each block. Then, I used the off-cuts of the angled return blocks to create a parallel surface so I could clamp them. To keep the blocks from sliding past one another I drill holes through the off cuts and hammered in some sharpened #8 nails driving the points through about 1/8". That way, when I clamped them the wedge block would not slide past the return block.

Next, I mixed up some Aerodux 185, a modernized resorcinol glue, superior to epoxy in strength and resistance to heat and water. I applied it with a glue spreader and ran the screws home and then added extra clamps ensuring even squeeze out.

Baring some unanticipated problem this is the hardest part of the coaming rebuild. There is still a lot of work left to do but it's coming along.

[John Stone]

After the resorcinol dried and I unclamped the coamings I took them back to the boat to test fit one more time.

Then I installed the wood plugs for the fasteners that secure the glued return blocks.

I radius's one side of the bottom inboard edge of the coamings. I radiused the outboard edge of the return blocks. Next, I used a laminate (trim) router with small cove bit and a guide bar to cut a caulking groove down the side of the coaming that fits against the molded fiberglass part of the cockpit.

I took measurements on the boat for the old bolt holes which I filled with thickened epoxy. I used a fostner bit to cut 1/2" holes down about 5/16" deep and then drilled the center with a 1/4" bit. Because African mahogany is on the soft side I am not going to secure these with flat head machine bolts because the wedge pulls deep intro he wood when tightened down. Instead, I am using pan head 1/4" fasteners with wood plugs covering. The pan head has better more even surface contact and is better I think for this project.

Finally, I sanded the coamings with 180 grit abrasives. All I need is to wipe down and apply the first coat of Epifanes high gloss varnish thinned 50 percent then a second coat about an hour later cut 10 percent. With the coamings protected by varnish I can take them to the boat and install them. That's where the 7-8 coats of varnish, sanding between every coat takes place.

When that's complete I'll reinstall the bare teak cap.

[John Stone]

First coat of varnished thinned 50 percent.

[Jim Walsh]

Is the caulking groove to eliminate the need for a bead of caulk where the side decks meet the coaming? I find that I have to grub out the caulk there about every two years and recaulk or suffer irritating small leaks onto the cockpit seats.
I could always remove my coamings and rebed them properly…but we all know that “ain’t” happening.

[John Stone]

Is the caulking groove to eliminate the need for a bead of caulk where the side decks meet the coaming? I find that I have to grub out the caulk there about every two years and recaulk or suffer irritating small leaks onto the cockpit seats.
I could always remove my coamings and rebed them properly…but we all know that “ain’t” happening.

Jim
The groove is set about a 1/4" below the deck. It's to ensure there is a good thick bead of caulk for a long lasting seal which won't be squeezed too then during compression and thus easily be broken over time. It's not right at the deck edge.

I was also unhappy with 3M 4000. We had that bad lot that liquified in some places and it was too aggressive an adhesive as well. So I'll use Boat Life polysulfide in mahogany color. I don't know how it will hold up over time, however, I used it to bed the winch bases with good results.

I'm interested to see if the caulking groove adds anything.

[Jim Walsh]

Maybe butyl in the groove? I use Boat Life teak colored polysulfide for the deck to coaming joint.