Bilge panels

I had some trouble with the aft bulkhead. After some messing around trying to make it work, I realized I'd made a mistake in the numbers. Once that was corrected, things started to move again.

The boat is now upside-down on the saw horses, getting the bilge panels fitted:

 

Below: the bilge panels roughed out, with 4-oz glass on their inward sides:

 I decided I'm going to follow the Gougeon brothers' advice and wash all epoxied surfaces before bonding to them. (pail of water at top of picture above)

To make the curve of the bow, I used my 5-foot aluminum straightedge:

But what I noticed was that that little tongue of plywood ahead of the bulkhead dipped down along with the ruler, so I clamped it with a piece of hardwood. The bilge panels won't be putting the same downward pull on that piece, so it needs to stay as it is.

Below: with a 2' long piece of hardwood straightening out that tongue of ply:

I put the bilge panel against the ruler and drew the curve onto it, then had to shift the clamps and ruler to the other side of the centre line in order to do the other panel.

I wanted to put both bilge panels on at the same time so I wouldn't be distorting the hull. Below, they're temporarily taped on:

Next will be to straighten out that bow seam a little, tidy up the joints here and there, then I might hot-glue tack a few spots. I'll put that duck tape on all of those seams, flip her over, and glass tape the insides of the seams.

Just as a point of interest, here's John's shop phone:

It has so much resin and gel coat on it, yet it still works!

Fun with foam

I decided that the temporary plywood forms were going to be too heavy to hang off the sides of the hull without distorting the side panels, so I made them out of 1" pink insulation foam instead.

I screwed the side panels onto the forms with drywall screws, which will come out before the outside of the hull gets glassed:

The two bulkheads need to be glassed before adding them to the assembly above. 

I decided to make my own hatch for the forward bulkhead. I noticed that the ⅜" foam with 4-oz cloth (in cured resin) on it can be curved by hand, as long as the cloth is on the outside, so I made the hatch cover with a lip:

 The sides had to be pressed in when gluing it up or they bowed out, so I made a form and lined it with plastic.

Below, the corners of the hatch cover still need to be rounded. Sandpaper works fine, but I needed a mask, which is at the shop, so will finish shaping it there:

Forward bulkhead with opening, hatch cover in background:

 How I did that: I first cut the opening in the bulkhead, then glassed one side of the bulkhead. Before the epoxy set up, I glued a rectangle of foam on top of that, trying to line it up well, as I had made the piece only ¼" or so larger on each side than the hole that it covered. After the epoxy set up, I cut the hole out of the added piece to the size of the opening, which left just a lip on top of the 4-oz glass. I did the same with the other side:

Above shows the forward face of that bulkhead, with the hatch cover on the after side of it.

The lip on both sides of the hatch opening make a frame that strengthens the bulkhead around the opening. I'll cover that frame with one or two layers of 4-oz cloth on the diagonal, with thickened epoxy in the tight corners. (The diagonal-weave cloth takes sharper corners without lifting off the work and leaving air underneath. It's also stronger, as the strands of both directions cross everywhere. And, it takes complex curves better.) The diagonal-cut cloth will wrap around the frame from one side of the bulkhead to the other.

You can see below that the hatch, although the opening is only 10½" wide and 7" high, takes up most of the area of the bulkhead. I just checked, and my tent and air mattress both fit through the opening. The sleeping bag doesn't, though, so it'll have to go in the after hatch, which will be about 12" by 14".

Working with foam, glass and resin

Polyester versus Epoxy

I first thought I was going to use polyester resin on my project. After all, it's in abundant supply in the 'glassing shop, is relatively inexpensive, and kicks off quickly, enabling a number of steps to be accomplished in quick succession.

John said the best way of using polyester resin is to cover the foam first with a "hot" sealing coat; meaning adding extra hardener to make it kick faster. The reasoning is that then there won't be any time for a reaction between the foam and any styrene in the resin. That's my understanding of it, anyway.

So I did that, using unwaxed resin, and when it was hard I put a piece of glass tape on, with an end sticking over the edge with which to pry it off. In that polyester resin test sample, the tape easily pulled off the first layer of resin, the sealing coat, before the tape tore:

For the epoxy test samples I just added glass tape to the foam and wetted it out with the resin. After a good cure, the G2 resin pulled off the foam, taking some of the foam with it, and the tape didn't tear. The West System epoxy wouldn't pull off the foam, tearing the tape instead. I must say, it wasn't a perfectly scientific test, as I hadn't left the same size of tab to pull on in the West sample. But the West sample test was more to check the new batch of resin & pumps, as I had already decided from the polyester/G2 testing to go with epoxy, for more certainty in the bonding.

Cutting the Glassed Foam

I started with a utility knife, then switched to my pocket knife to cut through the 4-oz cloth, finishing off with the utility knife to cut through the foam. This worked great as far as accuracy: I could cut exactly on the line. But it was hell on the hands, and took a long time.

John offered a jig-saw he'd modified to make a shallow cut, with a metal-cutting blade in it, which worked a treat. It was more difficult to cut exactly on the line, but was way faster and so much easier on the hands:

I put some styrofoam blocks under the work to lift it off the floor a bit. The blade extended ½" below the board I was cutting. Above, I'm getting out the second side plank.

Backside Reinforcing

As I was lifting and moving the glassed-one-side foam around—especially the long & skinny side panels—I was ever conscious of the butt joint between the two panels, and made sure to keep them oriented so that when the glassed side was down, the ends were supported. I could just imagine them folding away at the joint. Now I'm ready to put some glass tape on that joint. I sanded a bit of a hollow first, with 20-grit, so that it wouldn't be as visible when the outside gets glassed:

Now I need to wait until Tuesday to get back in there and do some more damage! ;-)

Progress

The trimmed bottom panel. After end:

The idea is to wait until the panels are all together before glassing the outside of that joint.

Forward end:

The two ⅜" foam panels were laid on the shop floor, butted, and held in place by a screw at each outer corner. The first hunk of cloth I bought was cut too short. This is it, smoothed over the panels, before I took it back:

Thankfully, the error was corrected. Below is the new cloth, now with epoxy resin on it. I ran out of epoxy after I'd got just past the butt joint. I laid a smooth piece of metal on the joint, taped with packing tape to keep it from sticking, and weighted down somewhat to make sure the two pieces joined evenly as the resin cured. Note the smooth, shiny surface that the taped metal left:

The bottom part above was the first part I epoxied (yesterday), and I put too much resin on it. Today I used less (top part above) and it went on well, with a plastic spreader.

I cut the excess glass cloth off the edges of the part I did yesterday, which cured well in spite of the low temperature in the unheated space (probably between 6 and 9 degrees Celsius):

And started drawing on it!

The lines I drew above at the bottom were wrong. I hadn't measured the stations out correctly, so had to do it over.

The hull panels will be cut out of this material, and this side will be the inside, so I put four ounce cloth on it. The outside will get 6-oz cloth. I'm using West system 105 resin with 206 fast hardener.

Here's a screwy photo:

This is one of the screws that held the pieces in place while they were glassed. It's in a part of the panel that won't be used for the boat, and will be cut out to unscrew it from the floor. 

Decision: Composite

I found some foam, and it was a reasonable price, as was the delivery. Also some very reasonably-priced (for here) meranti marine ply, ¼".

"A sandwich construction of a core material faced on each side with a reinforcing glass/resin skin offers greater mechanical strength and stiffness, pound-for-pound, than any other structural option, regardless of the materials used."
-http://www.compositesworld.com/articles/wind-foam-sources-pet-san-pvc

I'll make the bottom and—since I intend to install a rudder—the transom, out of the ply. The rest of the hull will be foam/glass. The foam is PET: polyethylene terephthalate. I'm using 10mm (⅜" equivalent) for the hull, and 6mm (¼" equivalent) for the decks. The "composite" part of my post title is about using both plywood and foam. I want the plywood on the bottom as insurance against harsh groundings on sharp objects.

Here are the two bulkheads (green foam) and the temporary forms. I haven't cut the transom out yet. It would sit on top of the left stack:

Below: Laying out the bottom on the mahogany ply. That single sheet of ¼" ply was heavier than all four sheets of the foam, which of course won't all get used because of offcuts.

The bottom is over 8' long, so the after end gets a bit scabbed onto it:

I left the drawing of the final shape of the after end until after the whole length was there, to make sure the curves are fair between the two pieces. The after end is only 1" wide!

Building material, ama design

There doesn't seem to be an easy way to get the foam core that I wanted to build with. I would have to go to Vancouver, or have it shipped. The stuff is so expensive, the cost to get it here would just make it too much to be justified.

So I'm planning now to use marine grade mahogany ply. It will be heavier than the foam would have been, but at least a familiar medium to work with. I'll use lighter, thinner stuff for the decks, heavier stuff for the bottom and the amas. And even though it will be the best plywood one can buy, it will cost far less than the foam board. Hopefully I'll be able to manage the weight, using the noggin.

Speaking of amas, I made a life-size model of an ama out of cardboard, to test the concept. For the first one I made, the two sides were held together with tape. I didn't want to use my good Duck Tape on a model, so I cheaped out and used hockey tape. Well, the tape soon pulled away from the cardboard, so I decided to sew the pieces of cardboard together instead, wrapping each edge with tape to make sure the thread didn't pull through the cardboard.

I'm quite happy with how it turned out, and now it's hanging above my couch:

The painting that the model outrigger is sitting on shows a full moon rising over Cortes Island, as viewed from Rebecca Spit on Quadra Island. The last ferry of the day to Cortes is behind a tree. In the drawing on the right, the Toronto Island ferry captain is chewing out a hapless sailor.

Model

Since I found myself with two sets of plans, I decided to use the one I won't build (Toto) to make a model with, so I could get a hands-on as to the building sequence. Very simple, really. My only problem was that the white glue didn't stick the paper onto the balsa as well as it could have, so had to be removed in places, but not before I marked whatever station was going to be lost thereby.

Toto, the one I modeled below, has a bigger transom than Rio Grande, the one I will build. The top form in the top picture here is the transom, and you can see that the bottom plank is going to be 4" wide there, since the half-measure is 2". On the Rio Grande it's one inch wide, ½" half-measure, and the vertical side is a bit more than half the height of Toto's side, so she'll have a daintier bum: