Mary Anne Design


[ Follow Ups ] [ Post Followup ] [ Previous # Next ] [ Start New Thread ] [ TarBoard ]

Posted by John on April 25, 2005 at 00:35:07 from 165.91.196.79 user Mcneacail.

The original design for the Norwegian Pram calls for 9 mm or 3/8 th inch planks. I started out the construction phase with 4 quarter planks. So I changed the design to have a 0.9 inch plank for the keel. A 4 quarter plank is really 0.9 inches or about 22 mm as measured by the vernier.

One can not build a boat with a vernier. This great little instrument allows me to determine the thickness of timber to 1/64th of an inch. I should have lashed out for the metric digital but it was more than I needed or wanted to pay. Compared to a ruler it is a pure pleasure to use. I mounted the vernier on the wall in a hanging pouch so I can get to it quickly. I bought the vernier after I planed down the bottom planks on a Dewalt home planer, and I wanted to be sure of the plank thickness.

James and I got the bottom planks down to 12 mm (0.5") in a long 5 hour session with the Dewalt home planner. So these bottom planks are about 3 mm thicker than the design calls for. I have been looking at the keel plank - now I am glad I put the keel in at 4 quarter so that I have a nice strong backbone for the boat - but I am concerned at the bending energy built up in the keel. I want the strong backbone for when I am teaching my daughter to sail - ie when she is rough with the boat and runs her aground. I know I ran aground when I was learning to sail.

I have seen a boat split longwise with a centerboard splitting the boat in two when it grounded on the lake edge. But I am concerned that the keel will spring the rest of the boat out of shape. I was also a bit worried about the copper rivets at 3 inches holding the 22 mm keel plank. It took two 12 mm bolts to spring the keel plank into position on the form.

So I have swapped the copper rivets for #8 bronze wood screws and an epoxy joint between the keel and the bottom plank. So now I have a 1 inch plank and will have two half inch planks to form the bottom - heavy but strong. I trust that my glulam operation for the bottom planks will not turn out to be in error.

I am much happier about this decision to change the design after seeing the thinness of the 3/8th plank on Friday. I am an old conservative engineer - but it is my boat so what the heck. This change in design also showed me how to build Swallow's keel when I finish this little boat and start to build the real project. The interesting feature of Saturday was putting in the plank.

Putting in the plank turned out to be an interesting exercise. I found out that the clamps held fine when the two planks were dry, but as soon as I introduced the epoxy between the planks I had a problem with the clamps not gripping and holding. The clamps I am using are wooden plywoood clamps recommended by the Boat Plan designer. These are cheap and good clamps, but I now know that I need help at the planking stage.

The planks are screwed together - I used 36 screws at 3 inch centers. The wood screws are soft and they are damaged if you use an electric screw driver - so I had to drive all the screws by hand. The soft screws need to be driven with a fair amount of end pressure or the head is damaged if the screw driver slips a bit. As a result of the driving I now have a nice blister on my right palm.

But is a nice pain and a lot of pleasure to be this far. Thanks for the advice it helps to know that I have a few friends - even though we never meet.

JMN


Follow Ups:



Post a Followup

Name:
Eel-Mail:

Existing subject (please edit appropriately) :

Comments:

Optional Link URL:
Link Title:
Optional Image URL:

post direct to TarBoard test post first

Before posting it is necessary to be a registered user.


[ Follow Ups ] [ Post Followup ] [ TarBoard ]

Courtesy of Environmental Science, Lancaster

space