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.

Interior work

Sally and I are preparing to head home to Virginia. Skorpa is not ready to come with us yet. Here are a few photos to bring things up to date.




I placed some glass fiber to reinforce the forward section.



This is a view looking down into the forward section. Bulkhead number one has been filleted and taped.





Framing in the seats.






Here are a few shots just to show where we are. She is beginning to look like a boat!

Bulkheads

After running fillets and fiberglass tape on both chines it is time to install some bulkheads.

This is the aft bulkhead along with a nice assortment of my clamps.





Then I did bulkhead number 3 the lower cabin bulkhead.




In the lower cabin bulkhead you can see a slot on the left side. This slot will be enlarged later to accommodate the the center board trunk. The trickiest part of installing a bulkhead is getting the right shape to fit. The aft bulkheads have fairly straight lines so it is possible to take several measurements and come up with a close approximation of the required shape.


The forward bulkhead is a bit more complex. I used a different strategy.




I used a plumb bob to establish a line where the bulkhead will meet the hull.







Sally is checking out the pattern I have made. I installed a scrap piece of plywood in the location for bulkhead number 1. Then I stapled little scraps of plywood like fingers touching all the important points around the perimeter and some inbetween.









OK now what?







How did that cat cat up there without altering the precise position of any of my indicator strips?





I made a mark at the tip of each indicator strip, connected with some fair lines and cut out with a jig saw.

What do you do with a very large skiff?

Here are some photos taken just after the jig was removed.






I fitted some temporary thwarts to hold things together until some of the internal structure is installed












That is the stem sitting up there in the bow. I had some concern that something would spring loose when the jig was removed, but all the plywood acted like it had no intention of going anywhere.





What do you do with a very large skiff?


Why you fillet.

Pronounced fill it.





Thickened epoxy is placed in the chine and then shaped to a concave surface.














After the fillet sets up just a little, a layer of fiberglass tape is laid down. Then the glass cloth is saturated with unthickened epoxy.

Lets get her setting on her DWL

DWL is the design water line.

If a boat is sitting on a very still lake, the line around the boat that the surface of the water creates is right on the DWL. That is if the boat is loaded properly and everything went according to plan.




I wanted to do two things before I removed the building forms.



First is to level the boat fore and aft as well as side to side. It is easiest to do this before the jig is removed because the base of the jig lies in a straight line parallel to the DWL.



Sally is adjusting one of the straps that has the hull suspended so it can be leveled and a cradle fitted under.


Second is to build a cradle that will support the boat while I finish the interior.





This is the forward cradle. I wanted something to hug the hull and prevent the forward sections from spreading when the jig was removed.




This is a support for the hull about two feet forward of the transom.








My third support structure is a little less elaborate. Go figure.

Roll Roll Roll your Boat

My boat moves out to see the light of day.








The boat and jig together are pretty heavy.


I can not even lift one corner of the boat.


It feels like it is fastened to the ground.



I use pipes for rollers. Sally and Judy help me roll the boat out into the driveway.









Hoping for a soft landing.



Many thanks to my neighbors the Baldwins and the Ciolfis for their able assistance.


























Back to bed right side up.















Goodnight