Marissa stops by for a visit

Graham Byrnes entered Woodenboats design contest for a fuel efficient 25 hp powerboat. He won with his design for Marissa. Graham took Marissa to this years Woodenboat Show at Mystic Connecticut. After the boat show Graham and his daughter Beth had a few days before they had to be in Brooklyn, Maine to teach two weeks of boat building courses.

Graham and his crew had burned the midnight oil to get Marissa ready in time for the boat show. There were a few details that had to be attended to before Marissa could be launched.

I drove Graham into Galilee and he bought some bolts and fuel line at Rhode Island Engine Company.

 Then he and Beth went to work.

Soon we were off to the boat ramp.

Cruising past the fishing fleet we headed for the breachway and the open water of the Harbor of Refuge.

Graham could hardly wait to open the throttle and see how Marissa will run. This is her maiden voyage.

Pretty smooth wake as we skim across the water.

Sally is sharing some local knowledge with Graham while Beth enjoys the ride.

After touring around for awhile we anchored Marissa on some sand flats and dug for quahaugs. We all enjoyed gathering the hard shell clams for our chowder. It was a late supper and a good day on the water.

Making an offering

All that framework is there to hold the 6mm plywood that forms the bunk tops and seat tops.

As you can see in the photo there is a lot of curvature in the hull up front. All that curvature makes fitting the bunks tops a bit of a challenge.

Making the tops out of as few pieces as possible keeps them light and strong. Meeting the hull on two or more sides is very tricky because if you have to do a little trimming you can end up making the panel too small.

To get around this problem I made a template out of a couple of pieces of scrap ply. That way I could individually fit each side until it was just right. Than I secured the two halves together.

Here I am laying out the pattern on my good plywood.

The result was a very nice fit.

I tried using cardboard to make a pattern and it works alright. The cardboard is a little compressible though so you do not get as accurate a fit as with the more rigid plywood.

 If the bunk or the seat top meets the the boat on only one side or on two adjacent sides you have it a little easier. You can get a rough fit and than use a block of wood and the side of the boat to scribe a line on the plywood. Plane down to the line and you should have a nice fit.

  Once you have the piece shaped to your satisfaction you can "offer it up" to the boat.

 

My boat has never accepted my offering the first time around. Sometimes after many attempts I just say that will have to do.

Joinery

The interior of an EC22 has a fair number of small parts that form a framework which functions to stiffen the hull and support the horizontal surfaces like bunks, seats and decks.

Most of these framing members are pretty light. Like 3/4 inch by 1 inch. Or under the bunks 5/8 by 1.

The framework is so light that you have to take care that the joints are as strong as possible without unduly weakening the framework.

 

 This is some of the framework that supports the bunks. I give each piece two coats of epoxy before I glue it in place. Epoxy loves to drip and run. Coating the pieces after they were installed could get ugly.

This is a butt joint. Simple to make, doesn't weaken either piece of wood, strong in compression, but weak in tension and in shear.

This is a mortise. Much stronger in shear, but you have to take a chunk out of one piece. It is not real easy to make the mortise.

I am not sure what this joint is called. I will call it a diagonal. I had not been aware of this method of joining wood until working on Skorpa.
At first I did not like the looks of it because it seems like the pieces could just slip apart under pressure.
Epoxy is pretty strong though and if it has some plywood on top to keep the joint from spreading than the diagonal is quite strong. Good in compression, tension and shear. Minimal weakening of the adjoining pieces and not too difficult to make.

I mark out the lines usually for 45 degrees. Saw cuts outline the sides and help control the depth.
A sharp chisel takes out the wood.

There are several variations on the basic diagonal.

These pieces will support the bridge deck on either side of the centerboard trunk.

Here we are under the port bunk. 4mm (1/8 inch) plywood webbing ties the hull stringer to the bunk framework. I use Mikes router to round off the underside of the framework.

View of the starboard bunk from above.

It is taking a long time for me to finish this boat. Yes I am having to learn as I go. I am trying to work carefully and do quality work. I also have a lot of other responsibilities to attend to.

Cockpit interior

What a strange word.

Cock Pit.

A depression in which roosters fight.

The location of many battles.

An open area near the stern of a vessel below the level of the deck from where the vessel may be steered.

I covered the floor of the cockpit with a layer of 2 ounce fiberglass cloth. This cloth is so light it does not add much strength. I have read that it adds significant resistance to abrasion without much additional weight, so I thought I would give it a try.


When the epoxy saturates the cloth it turns clear as glass.

Here the cloth has been wetted out and stringers have been glued in place to stiffen the hull.

This is a view through bulkhead # 4. You can see a piece of scrap wood holding the stringer in place while the epoxy sets up.

Looking forward from the Lazarette.


The Mizzen mast sits right in the middle of the cockpit.

The Mizzen mast step must hold the base of the mizzen mast securely. This rig has no stays. The mast step and the mizzen mast thwart have to bear all the loads placed on the mast.

The mast step is laying beside its intended location. There is so much force on this part Graham thought it best to use mechanical fastners (screws) in addition to epoxy to make sure the mast step holds.
Wherever fastners penetrate the wood moisture can find a way into the wood.
I drilled oversize holes and filled them with epoxy. Then I redrilled the proper size hole for the fastner.

Undoubtedly overkill for a boat that will be dry sailed, but what can you do?

Centerboard Trunk

The centerboard trunk sits over a long narrow slot in the hull of the boat. The trunk must be water tight and strong enough to support the board. A lot of force can be applied to the extended board.


Someday I might get the board stuck in some mud. The wind and tide might try to twist the boat while the sticky mud tries to hold on.

So two layers of cloth on the inside and one on the outside of the trunk.

 Trimming the excess cloth.

The two by two looking piece of wood with the clamps is the king post.
The width of the king post determines the width of the trunk. Too wide and the board might rattle.
Too narrow and the board might jam.

 I did not glue the king posts until the very end so I could adjust their width.

 The carbon gets everywhere.

  The center board pivots on a bronze pin.I drilled out an oversize hole filled it with epoxy and then redrilled so the pin will rest in a epoxy bushing. The cap covers the hole so no water gets in.

All the screws get their own epoxy bushing.

The trunk gets a trial fit. The trunk is supported by two bulkheads. Here you can see the trunk protruding through bulkhead # 3 into the cabin.

Centerboard

Graham has redesigned the centerboard for EC22. He wanted to remove an annoying touch of lee helm. which became worse when the board was partially raised as when sailing close hauled in shallow water.

The new centerboard has a lead tip sized to make the board sink and stay on the bottom but kick up readily if an obstruction is encountered.

First task is to laminate a dozen or so boards to make a 61 inch by 16 inch blank. Laminating from a lot of small sticks is time consuming but allows you to select for good straight wood and control things like grain orientation. Hopefully this results in a centerboard that has little inclination to twist, bow, warp, crack or mess up.

There needs to be enough lead on the board to make it sink and stay down even when the boat is at speed.

 Graham suggested about 15 pounds of lead. Someone else used about 18 pounds for a similar board.

 I decided to try to calculate the weight of lead needed and the amount of the board that should be lead.

That is should the bottom 2 inches of the board be lead or bottom 4 inches or 6 inches?

I could figure this out empirically by taking the completed board out into the water and piling weights on it until it sank. Then add a few pounds for good measure.

Another way involves calculating the volume of water displaced by the board and using the density of the board and the density of water to arrive at the amount of lead needed.

I carefully measured and weighed my centerboard blank to determine a density or 0.017 lbs/cubic inch.

The density of water is 0.036lbs/cubic inch

The density of lead is 0.409lbs/cubic inch

The density of my Douglas Fir centerboard is about half of the density of water.

After the blank was glued up and smoothed I cut it to shape in two dimensions. Then I marked the edges in preparation for shaping the board in the third dimension.

Did I mention that some centerboards are flat, however a board with a air foil like shape is more efficient.

 

Heading North to escape the snow.

I have been looking forward to heading back to Rhode Island so I could get back to work on SKORPA.

Putting up firewood, felling saw logs, sawing lumber, erecting a fence all tasks that needed to be done. None of them made easier by the beautiful white stuff. A couple of weeks later than I had hoped we left Virginia and headed for my long silent boat shop.

Everything was just as I had left it. Not a thing had been done.All the work I had done last summer looked pretty solid. Nothing had sprung apart.


First order of business is to glue in the mid transom beam. It was already fitted just needed some creative clamping arrangement to hold it in place.

I need to put pressure on the beam running down the center inside of the transom, way too deep for any clamp I own to reach.

With some scrap lumber and my ordinary C clamps I have an arrangement that can put just the right amount of pressure just where I want it.

Here as the clamps are being removed you can see that the mid transom beam is laminated from two pieces and wraps nicely around the king post or whatever that big board going up the center of the transom is called.

High on the list of things to do is the centerboard and centerboard case.