Birdwatcher-2 Computer Modeling

Birdwatcher-2 Sailboat, designed by Phil Bolger

Various modeling tools are now available to add insight to boat performance. I have wanted to use these to do some calculations on the Birdwatcher-2. This page shows some images from the FREE!ship program, which allows 3-D model construction. I built the model with the intention of calculating resistance, stability and other parameters. To date, only the boat images are ready to leave my computer and wander the Internet, but I'm working on checking the performance data. Results will be posted here, one of these days!

Birdwatcher-2 with the designed sail plan.

The designed sail plan is a Solent Lug using a hefty yard to hold the top of the sail 27 feet over the water. The main is shown as 142 square feet on Bolger's plans, but some how it came out over 150 for me. The jib is 71 square feet. With this sailing rig, the boat is quite spirited!

Birdwatcher-2 with small main.

After the first season with the boat, I decided a second reef in the main would be very useful. The Solent Lug does not adapt well to this, so I decided to create a small main. The whole story about this sail is on the sailing experience page. The sail area is about 90 square feet. No yard is used, and a shorter boom was built. This sail can be used with the jib in lighter airs, but it does tend toward lee helm.

Birdwatcher-2 from port bow.

The model includes the forward hard cover. I normally leave this cover on, and have a cloth cover that goes over the rest of the slot.

Birdwatcher-2 from starboard stern.

One can spend much time adding detail to the model. Beyond some point, it does nothing useful! I show the outboard motor, but not the mounting board.

Birdwatcher-2 bottom side.

The offset centerboard can be seen. The model is great for visualizing this part of the boat. The portion of the boat that is below water is in light gray.

Birdwatcher-2 x-ray view from FREE!ship.

I just toss this in, as it is the side view from FREE!ship. As setup here it gives an X-ray view. Interesting, and possibly useful.

Back to Building Birdwatcher-2 main page

This was last revised 10 August2008. Bob Larkin, Corvallis, Oregon