Coaming, Hatches, and Bulkheads

Do Both Edges at Once
Glassing Parts Using One Piece of Cloth
Get ready to do the coaming and hatches well before you are going to install them–prepare the parts (saturation coats, glass) while you’re waiting for the resin to cure on the deck or hull. It may appear to you that these “small” parts will be a piece of cake, but in reality they require many curing steps to get all the edges treated with resin and then some faces glassed. You can wind up taking a week to do them when, with a little planning, you can get them all done in two days–that’s two days in parallel with the bigger glassing tasks on the hull and deck, so it’s not two additional days.

Anyway, pay attention to these items early on–find ways to support them while they are curing so that you can have more than one face/edge wet at a time. For example, the coaming spacers are resting on two plastic tool boxes and the flat parts are being glassed under one piece of cloth (you have to be careful to hold all the pieces flat or they will lift the cloth off adjacent pieces).

Mask Outside of the Spacers
Coaming: after the parts are prepared, meaning epoxied and trimmed to fit (I do the coaming in a non-standard way, meaning I depart from the kit instructions—I only glass the bottom of the coaming lip), I clamp the spacers to the deck and apply masking tape around the perimeter. This will keep the wood putty off the deck surface and will make for easy clean up once the spacers are epoxied on. Then the lip gets epoxied on, with the glassed side down. Then I glass the entire coaming assembly to the deck, using two (or sometimes three) pieces of cloth. You can see here I’ve draped the coaming with two pieces, with the inside pieces hanging straight down.

Multiple Pieces, Let the edges Hang Down

There are a couple tricks to glassing the whole coaming in this way. First, if you round the outside edge of the lip, you can actually epoxy the glass around the edge and up under the lip. To do this you need a method to force the glass around the curve and to hold it up against the under side, like a fat tube of foam wrapped in Saran Wrap. This works (see the pages on contructing the Tern), but it’s impossible to keep the glass on top of the lip flat–it wants to round up right at the edge, so it takes a lot of wetting out to prevent air bubbles there. Anyway, it is doable. For this boat I elected to just drape the glass and wet it out to the edge, then trim it off and sand smooth.

The Slits Aren’t Visible Once the Cloth is Wrapped Under
Second, to curl the glass up under the deck, you need to (1) round the visible edge of the deck so that the cloth will adhere (do this after the spacers are epoxied on and before you start draping the cloth) and (2) cut a few slits in the glass–wait until you’ve wet out the top and sides, then cut the slits as required only up to the underside of the the deck.

You’ll need 5-10 slits on each side, more where the coaming is curving the most, less along the sides. When you get to the slit cutting step, you can also trim the amount of cloth that you wrap up under the deck to about 1″. Note here that whether you do the partition modification or just have the normal hip brace, the cloth will overlap the top of the brace or partition. The amount of overlap is not critical, just trim the length to make it easy to wrap the cloth underneath. Come back in a couple hours and make sure the cloth is tight to the underside—use a squeegee to smooth the cloth, if needed. I like the idea of having glass coating the entire visible surface of the coaming—not needed for strength, I just like it.

Start with a Japanese Saw

Finish with a Saber Saw

Hatches or Coaming, It Takes a Zillion Clamps

Hatches: Mark the hatch outline according to the kit plans. I cut the deck using a Japanese flush cutting saw. This saw is very flexible and you can hold it in a slight curve with your other hand to match the cut line. Only cut deep enough to slice throug the glass on the underside of the deck to creat a slit about 1/2″ wide, which will require about 3″ of kerf on the top of the deck. You can use a hacksaw blade in the same way (the blade by itself, not in a hacksaw). I use a very fine saber saw blade to cut out the remainder of the hatch. Be careful that the foot of the saber saw doesn’t mar the dec surface and put a piece of tape in the middle of the hatch so you can hang on to it as you get near the end of the cut.

Once you have cut all the spacers and lips to fit, it takes a zillion clamps to do the install steps.


This is the Only Way to Work on Bulkheads


Bulkhead Gaps Need to be Filled

Bulkheads: When you work on the bulkheads, you really want your boat in a sling. This makes a very difficult task almost doable. I say that because mine never seem to fit precisely. I had to cut down the ones in the Tern and Coho, but in this boat they were somewhat smaller than the boat cross section, so there were substantial gaps all around. Nothing serious, but enough that some method of reinforcement was called for. As you can see from the photo, the gaps extend across more than one panel. If the panels are pushed inwards, I think it would collapse even two layers of fiberglass tape. The solution I used was to glass in one side of the bulkhead, let it cure, then squeegee in wood putty from the other side to fill the gaps. Then that side was also glassed in (with tape). This provides a very strong bridge from the hull to the bulkhead.

Wedge and Brace the Bulkhead in Place for Taping

Holding a loose bulkhead in position is a challenge. I use a series of taped in braces and wedges to lock the bulkhead in place. You don’t want to glass those in with the bulkhead, so you’ll have some gaps in the tape on the first side. Once the tape has cured, you can knock the temporary supports out and glass in those gaps, apply the putty from the other side, and then tape that over, too. Once you’re done, there are a lot snags and edges that need to be scraped or sanded smooth. You don’t want to ruin your dry bags that might be pushed up against a rough bulkhead.

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