BLUFF RATTY 15 Jan 21 Musings and Materials

 15 Jan 21:

We had a 4x8 sheet of 1/4 inch marine grade ply and some 3/4 inch thick cypress in varied widths, so I thought we'd use that up first. We used several punt (flat-bottomed boat with a square-cut bow, designed for use in small rivers or other shallow water) plans to get an idea on what size pieces to cut, how long, how wide, how high. Our limiting factor on this BLUFF RATTY v1.0 Marine COnstruction Contract Design 1, Hull number 1 (MCC-101) is using only one sheet of 4x8 plywood. SUPER BLUFF RATTY (MCC-201), in design also, will use 2 sheets.  Marine grade plywood is nice, otherwise work with you local lumber store or cabinet shop to order the best grade plywood you can, with waterproof glue, higher grades are best, they have fewer voids in the plies, smoother and thicker veneer, and more internal plies. Pressure treated plywood might be considered as well. Southern Yellow Pine, white pine, douglas fir or spruce would work fine for the solid wood, white oak best, some woods will need more care and maintenance and some are easier to work with. Availability of materials will usually be the main issue.

Those are the basics for material selection, there are builder decisions to be made. A white pine boat with the cheapest grade plywood could have a very limited lifespan of one season unless it is pampered with excellent coatings and stored out of the weather. It will be inexpensive and fun to build. A white oak or cypress boat with high grade marine ply, excellent coatings and silicone bronze fasteners could be a family heirloom "100 Year Boat" with reasonable care and maintenance, and it will also be fun to build. Either way there is fun to be had building a boat that will easily carry an adult and a kid, or a couple of kids. Crew capacity and weight will be determined soon and posted here, we are shooting for 2-3 crew, 300-400 pounds total weight.

Insert Materials List here.

Insert Plans here.

Using numbers floating around in our head, we cut 8 inches off each side to become the 2 lower planks (garboard). Once this is done, Congratulations! You are building a boat.

The bottom is going to be one inch narrower on either side than the top (sheer), so we cut 2 inches off the length of one side of the bottom panel.

The lower planks have a rise of 5 1/2 inches starting 30 inches in, from each of each panel, so we made 2 marks on each side plank.

We cut out the 3/4 inch thick lumber next, to varied widths and lengths (see Materials List, once we develop it). One of the cuts is a 3/4" x 3/4" strip to make the chine, the strip that a side panel and bottom panel attach to. Today we used several #6 x 3/4 inch screws to temporarily attach the side panel to the chine out past the 30 inch mark, since we plan on screwing the sides in final construction, clamps could be used also. Then sprung the chine strip up 5 1/2 inches, measured to the top of the strip, to get the lower curve (rocker) of the bow and stern. Marked that rocker on the lower side of the chine strip, removed the chine and cut off the lower bit of panel with a jigsaw. You could cut 2 panels at the same time if desired. Save the lower cutoff(s) to mark the other end and for potential use later.

Next we cut the solid stock to varied widths and lengths per plan. These bits will make the bow, transom, seats, chine, upper plank (sheer plank), frames and other bits. If you ever thought about buying a portable table saw, now is the time :) 

Bow and transom.

Seats, bow and transom. Lower and upper planks. Bottom.

We work to Sharpie tolerances aka Galloping Horse Marine Construction. Some folks use sharp, sharp pencil. Measure twice, cut once. Cut a few extra pieces. We leave a tiny bit extra, and trim to fit during final construction. Keep a Moaning Chair handy to sit and ponder mess ups and future plans. Drink coffee.

Log of BLUFF RATTY.

Catboat Math 05 Apr 20

05 Apr 20:

There's the plan and then there's actually what happens. We have Chapelle's line drawing for a 17 foot diamond bottom catboat, and we planned to scale that plan down to 16 feet. Let's see that's .941176 smaller. So I did a bunch of measurements and scribbled all over a copy of the plans and headed out to the Carriage House to transfer those numbers onto a lofting on the Carriage House floor. But first I had to correct my highly calibrated blue tape baseline, and mark off 1 foot increments out to 16 feet. Then I used the square to find a perpendicular at each foot mark, took the steel tape to find the Feet-Inches-Eighths point, make a mark and put in a deck screw.

Somewhere along the way I remembered that I wanted to scale the beam of this boat down from 8'6" inside of plank to 8 feet outside of plank. I thought I could just reduce everything by 10 percent but instead discovered I needed to draw a new sheer line, and get those new measurements off of the new line. Fiddled with the fair curve and came up with a sheer that looks okay, pending Skipper's approval.

If Skipper is happy with it then we can pull new measurements off of the lofting at a few points to get the measurements we need for building molds and bulkheads.

Placed the rough keel batten down to start thinking about keel shape.

Log of MARGARET ROSE.