Building classic Herreshoff pram

[Rees Midgley]

As my first real woodworking project, I am building a classic Herreshoff pram in the British Virgin Islands (tough, I know). The ten-foot boat with transoms in the bow and stern will be light, planked with Northern white cedar milled to be 1/4" thick. The curved planks (strakes) will be bent over a series of rounded station molds hanging from a suspended ladder and then riveted together every 1-1/2 inches. The ladder has to be straight to keep each mold hanging exactly as intended by the lofting.

That is my problem: how can one ensure that the ladder will stay straight? The boat plans, taken from a book by John Gardner, "Building Classic Small Craft," recommends use of two, straight, 12-foot 2x4s each on edge and separated exactly 24 inches outside edge to outside edge by 1x4 cleats attached below the 2x4s and spaced every 15 inches. The molds will hang from these cleats.

We have very limited choices for lumber. Other than importing, everything is construction grade, and treated to prevent termites. Moisture content is high. While it may dry some, with huge changes in season (dry to rainy -- all with high humidity and wind), the wood will change. I own two suitable 2x4s but worry that they will twist, cup and bend over time as moisture continues to equilibrate. Positioning 21" 2x4s between the long 2x4s might help to reduce lateral bend, but what about vertical? I could also work with treated 2x6s but they are heavy and later I will need to turn the boat over. Any suggestions?

http://homepage.mac.com/rmidgley/BuildingPlatform.JPG

[Paul Douglass]

Rees, I'm no expert on boat building, so I won't attempt to answer your question. You can probably get help here but (maybe you already know this) there is a great boat building forum, on building small boats. I don't know if I can post the address here, so do a search on "messing-about" and I'm sure you will find it. Just like here they are a great bunch of people and very willing to share their expertise.

[John Schreiber]

As I understand it, there's no problem with posting a link to another forum, so long it's not to a specific post in another forum.

I'm also no boat builder, but I'd like to be. I would suggest laminating together some lumber to make your own "2x4". Pay attention to the grain so that
they will generally pull in oposite directions when they try to bend and hopefully the outcome will be that they stay straight.

Best of luck. It's 11 degrees F here and we'll have 6" of snow by the end of the day.

[Dave Richards]

Rees, I would suggest that you give the folks on the WoodenBoat froum a try. There you find a huge number of folks who have lots of experience and besides, they'll be extremely interested. I can't post a link due to forum rules but you can easily find it through the WoodenBoat site.

Are you building the boat right side up? Commonly, small boats are built upside down with the ladder below. Then you can put in as many legs as you need. Over 12 feet I would think 4 pairs of legs would be plenty. If you can set the legs in the ground, do so. Then level the ladder on the legs. Another option would be to set the legs on concrete blocks. Diagonals will help to stiffen everything.

[Ben Grunow]

The word ladder brings to mind an aluminum ladder. Any old ladders around? You could screw a section across the 1 x 4s to keep the whole thing straight.

Other idea would be to use a ripping of LVL (laminated veneer lumber) beam commonly found at any lumber yard. They are glue and wood and cut easily and hold screws/nails better than real wood. Warpage would be minimal if both sides of the rippings were fresh cuts (cut off factory sides to allow air to get to both sides).

Hope this helps.

Ben