MOLLY 24
(HOME) (SAIL BOAT DESIGNS) (PRICES)
MOLLY 24
25’ LOA
23’ 7" LWL
8’ 6" beam
3 foot draft
4145 pounds displacement
900 pounds of lead ballast
700 pounds of water ballast
INTRODUCTION:
OPTIONAL CAT BOAT RIG
The MOLLY 24 is a stitch and glue (S&G) design, with all surfaces built from 1/4" plywood. S&G panels are designed to contain NO compound curves. They can bend and twist, but only in one direction. The patterns for the six hull panels may look strange, but when their edges are "stitched" together, they bend and twist into the desired shape. While in the proper position, the panels are "glued" together, using filled epoxy adhesive. All exposed surfaces are glassed to eliminate dry rot and insure a stiff hull. Four full bulkheads are glassed into the hull for extra stiffness.
Ballast consists of 900 pounds of lead and 700 pounds of water. When the boat is launched, water floods the ballast compartment. When the boat is retrieved, the ballast runs out. No pumps, no valves, no problems! On the trailer, the boat weighs 3445 pounds.
OVERVIEW
MOLLY is built upside down, starting with the deck and cockpit. After fiberglassing the deck, four bulkheads (located at stations 24, 84, 180, and 228) glassed in place. Six plywood panels are stretched over the bulkheads to form the hull. Both the edges of the bulkheads and the edges of the hull panels are beveled to insure a good fit, and then the panels are attached to the bulkheads and stitched to each other along the seams. In areas of high curvature, closely spaced copper wires are used to close the joint. Other areas can be held with nylon wire ties. When all the panels are aligned, the joints are filled with epoxy fillets and sanded smooth. The forward two feet is formed with vertical wood strips, stapled to nose patterns attached to station 24.
After all the hull panels and keel are in place, the joints are sanded smooth, and the hull glassed with one layer of 20 oz. bi-axial cloth. The cloth should be cut to overlap each joint by 4-6 inches. The inside of the hull to deck joint is also glassed while the hull is upside down.
The boat is now turned right side up and the deck glassed. Inside, the top of the keel is glassed to the hull, and the lead ballast installed. Finally, the keel is fitted with a closure bulkhead (containing a vent fitting), and covered with the cabin sole. The hull is now structurally complete and ready for the cabin and interior arrangement. Several layouts are detailed in the drawings, however the builder is encouraged to modify the arrangement to suit any unique requirements.
The following prints are included in your plans. Go over them carefully and contact me if you have questions.
1. LINES
2. ARRANGEMENT
3. BULKHEAD DETAILS
4. HULL PANEL DETAILS
5. STRONG BACK AND DECK DETAILS
6. CABIN DETAILS
7. PROPULSION OPTIONS
8. BUILDING MANUAL
9. WEIGHT AND BALANCE SPREADSHEET
10. BILL OF MATERIALS SPREADSHEET
11. SAIL PLAN, SLOOP
12. RIG OPTIONS: gaff rigged cat boat
I want you to both enjoy this project and complete it successfully. Please don’t hesitate to contact me if you run into problems or have any questions. Sharing ideas with other builders is also beneficial. With your permission, I will forward, from time to time, comments and questions from other builders. Sort of an informal email based "users group". Now, let get started!
GETTING STARTED
The plans for building the MOLLY 24 should be carefully studied before any work is started. The LINES drawing is a good place to start. Identify the various sections, waterlines, and butts, and form a mental picture of what the hull looks like. It is essential that you understand the basics of Stitch and Glue construction and fiber glassing techniques. Many good books on these subjects, and I strongly recommend that you read several.
THE GOUGEON BROTHERS ON BOAT CONSTRUCTION
PO box 908
Bay City, MI 48707
COLD MOLDED AND STRIP PLANKED WOOD BOAT BUILDING by Ian Nicolson
The Wooden Boat Store, PO box 78
Brooklin, Maine 04616
FIBERGLASS BOATBUILDING FOR AMATEURS by Ken Hankinson
Boatbuilder Books
PO Box 540638
Merritt Island, FL 32954 phone 321 459 1558
Don't be intimidated if the project appears too complex. The MOLLY 24 is designed especially for home construction, and is technically no more difficult than building an S&G kayak. If you’re still uncertain about your capability, consider a small project first, like building a dingy or canoe. The basic steps are all the same, and a small project will sharpen your building skills and develop self-confidence. During this time, you can also collect a lot of valuable information by visiting boat dealers, boat shows, and marinas. Ask questions, look for details that you may want to consider including in your own boat, and sketch up some possible seating arrangements. If you have web access, do a search on "stitch and glue" and visit the boat building news group.
Work slowly, and be careful about purchasing special items before the boat is complete. "Things" that look great in a marine hardware store may look differently in a small boat. If there is one good piece of advice in boat building it’s "KEEP IT SIMPLE".
The ideal building site for the MOLLY 24 is an enclosed workshop or garage about 12’ wide and 30’ long. The work area should be kept dry, but the boat can be built outside, using a plastic tarp for rain protection. Fiber glassing in direct sunlight is not advised, as the resin will "go off" very quickly. If you’re forced to work outside, set up a sunshade or do glass work VERY early in the mornings (but avoid dew).
Only a few power tools are needed for this type of project. You can get by with an electric drill, saber saw, and a 6" disc random orbital sander. An 8" disc sander, 4" belt sander, and an orbital palm sander are "nice to have" items, but not required. A portable skill saw is the best tool for cutting the panels out. A good set of common hand tools should include a level, 4' straight edge, 24" framing square, hand saw, assorted screw drivers and open end wrenches, 10-18" bar clamps, 10-4" c-clamps, a good set of sharp chisels, and a wood plane. Optional tools include a shop vacuum, air compressor, router, skill saw, and electric screwdriver.
The project requires around 24 sheets of ¼" plywood. Marine grades are not necessary, since the wood is completely incased in fiberglass. Fiberglass materials should be purchased in bulk in order to get the best price. Epoxy resins will give the best performance and are recommended for areas where bond strength is critical. For everywhere else, I recommend ISOTHALIC polyester laminating resin. It is tougher then the standard "ortho" resins, and more resistant to blistering. The suggested fiberglass schedule is one layer of 20 oz. bi-axial cloth, inside and out, with generous overlaps along the keel and turn of the bilge. Standard 24 oz. woven roving can be used instead, but it is not quite as strong as the stitched fabrics and more difficult to finish.
Bi-axial cloth is easy to wet out and drapes well around compound curves. You will also need 30 yards of 8" wide double bias tape, with a mat backing (if your using epoxy find a tape with no mat). The double bias tape is used to attach bulkheads and reinforce places like the hull to deck and transom to hull joints. Start with 5 gallons of epoxy, 15 gallons of laminating resin, and two gallons of finishing resin.
To recap, the basic steps in the building sequence are:
1. Build the strong back
2. Build the deck, cockpit, and glass it.
3. Position the four bulkheads on the deck and glass them in place
4. Build the keel
5. Cut out the hull panels from 23’ long scarfed panels
6. Install the first panel and glass it to the deck.
7. Install the second panel
8. Install the keel
9. Install the third set of panels
10. Glass the outside of the hull and turn it over.
11. Glass the deck and cockpit
12. Build the coaming
13. Build the cabin
14. Finish the interior
15. Install electrical, plumbing, propulsion, standing rigging, and running rigging
BUILDING THE STRONGBACK AND TABLE
Build the rectangular strong back from 2x8 stock, forming a 4 x 24 foot rectangle. These boards can be construction grade but should be straight with little twist. Stiffen the structure with 2x8 cross members on 4’ centers and put 18" wide plywood gussets at all the corners, top and bottom. Dry wall screws and white glue work well here. Be careful to square the strong back up by equalizing the diagonal measurements.
Raise the strong back two feet off the ground, and level it. It’s a good idea to anchor the strongback with a few 4x4 posts set in concrete, or molly bolts into a concrete pad, or lag screws into a wooden floor. Whatever method you choose, be sure that the forms are rigid enough to withstand the forces required to bend and twist the panels in place. Arrange 25 eight foot long 2x4’s across the strong back on 12" centers and temporarily anchor them to the strongback with dry wall screws. The 2x4 surface will be used first as a giant table for scarfing and fiberglassing the deck and hull panels. It will then be used to build hull.
BUILDING THE HULL PANELS
The hull panels are built up from sheets of 4x8 plywood, using an 8-1 scarf joint and epoxy glue. The quickest way to do scarf joints is to stack up all the plywood, with each sheet off set by the scarf length, 2". Make sure the edges of the stack are flush, and then clamp the stack securely using several long drywall screws. Use a router, portable planer, belt sander, or disc sander to form the scarf. You can monitor the progress of the scarf surface by watching the contour lines that develop along the ply’s. Try and get these lines straight and the same distance apart.
When the joints are finished, glue them together into 23’ long panels using epoxy adhesive. The best procedure is to coat both surfaces with a thin layer of pure resin and let it soak in. Then coat both surfaces with thickened epoxy, line up the joint and edges, and staple through the joint in four places. Cover the joint with an 18" wide piece of plastic, then stack up the material for the next sheet, and repeat. When all the pieces are glued together, apply a light pressure to the joints to push out any extra epoxy. After the epoxy cures, clean up both sides of the bond line, and the edges, with a sander.
Stack the full panels in two matching pairs, and lock them together using 3 or 4 drywall screws. Check the panel dimensions to locate a centerline that will minimize plywood waste and mark it using a chalk line and straight edge. Draw lines, at 90 degrees across the centerline, every 24".
Next, check the drawings for each panel’s dimensions, and carefully mark the points on the vertical lines. When all the points are marked, use a flexible strip of wood to make a fair curve from the points, and mark the cutting lines. Then mark each panel’s number next to its forward edge. The hull panels are numbered from 1 to 3, starting at the shear, and the joints they form are named according to what panels they contain. For example, joint 1-2 is the first joint down from the shear.
Cut along the line using a skill saw, saber saw, or handsaw. With the panels still locked together, dress the edges into a fair curve and round them off with sandpaper. Then open the matched panels like a sandwitch, and cover the inside surface of each panel with one layer of 20 oz. Bi-axial roving.
I prefer to work one strip of cloth at a time, starting by lifting it up and laying down a heavy coat of resin directly on the plywood. Reposition the cloth and press it into the resin, then roll resin over the outside. Look for dry spots and air bubbles. Add resin to the dry spots and stipple the fabric to remove air and excess resin. Complete an entire panel before moving to the next panel. If you have help, let them search for dry spots and air bubbles. Don’t get carried away with squeezing out "extra" resin. Its better to end up a bit resin rich then to have starved areas.
Trim the fiberglass and round off the edges. A little helpful hint: Check the progress of the fiberglass as it cures. When it feels like rubber, it can be trimmed quickly with a sharp box knife. Wait to long and it will have to be trimmed with a grinder or saber saw.
Slide the finished pair of panels off the table, making sure they are marked correctly (number, port or starboard, bow, edge, etc). Repeat this process until all six hull panels are finished.
BUILDING THE DECK
Scarf the deck together, using waste from the hull panels as much as possible. Glass the deck with one layer of 20 oz. Bi-axial roving, overlapping the cloth by 4 – 6 inches. Trim and sand the edges, then slide it off the strongback.
Remove the 2x4’s from the top of the strongback, and build the sides up to the shear dimensions shown on the deck drawing. Replace the 2x4’s and fasten them to the sides with drywall screws. Replace the deck panel and align it with the strongback. Hold it in place with dry wall screws along the centerline and inside edges of the cabin and cockpit cutouts. Look for any unfair areas and adjust, if necessary, with shims and more screws. The deck needs a little camber, which is formed by lifting the edge of the deck and inserting a 1" thick shim, at each 2x4 support.
It will save you time if you install the cockpit now. It should be glassed to the cut-out in the deck with double bias tape. Give the bottom of the cockpit a 1" slope for good drainage. The cut-out for the cabin should also be fitted with a 2" deep edge made from ¼" plywood. Glue the edge of the plywood to the bottom of the deck, just flush with the cut-out, round the edge, and glass in place with double bias tape.
BUILDING THE BULKHEADS
The MOLLY 24 hull is built over four bulkheads located at stations 24, 84, 180, and 228. The shapes are simple enough to lay out by hand, using the dimensions from the drawings. Build the forms from two layers of 1/4" plywood, 6" deep. Outline any doors or other openings, and then cover both sides with mahogany door skin. The bulkheads include an allowance for skin thickness.
Position the bulkheads on the deck and check their alignment using strings or a laser level aimed at water line zero and the centerline. NOTE: The stem has 2" of tumblehome. This places the front of the deck 2 inches aft of station zero. Be sure to allow for this when positioning the bulkheads. When they are aligned, glass them to the deck with double bias tape, both sides. Finally, take a 24 foot long 1x2 stringer, and lay it down at roughly the middle of the contact point each panel makes with the bulkheads. When it’s bent into position, mark the location on each bulkhead, and the transom, and notch it to fit the stringer. The bottom panel gets two stringers. Look for any flat spots and shim from the deck as needed. Glue the stringers to the bulkheads, but not to the transom. Hint: Dress off the inside edges of the stringers, since they will visible from the inside.
BUILDING THE HULL
The #1 panel(s) can now be fitted to the deck, transom, and bulkheads. Dry fit the panel and drill for screws every 12" along the stringer. Bond the panel to the deck, all bulkheads, stringers, and the transom with thickened epoxy using generous fillets. The inside of the hull to deck joint can now be glassed with 8" wide, double bias tape, and the second set of panels glued in place. At this point, the keel is positioned in the hull, aligned, and held at waterline -6. The remaining two hull panels are now fitted and bonded together. Attach the nose forms to bulkhead 24. Use vertical wood strips, ½" thick, to form the rounded nose. With the boat upside down, now is a good time to glass in a series of simple plywood deck knees, every 24 inches, and a pair of laminated deck beams forward of the cabin.
BUILDING THE KEEL
The keel is formed from 1/4" plywood, supported by two forms. Use a skill saw, set for a 1/8 deep cut, to score the inside surface of the sides. The cuts should be ½" apart for the first 6", then 1" apart for a foot, and 2" apart for another foot. Fill the saw cuts with thickened epoxy and press the side into the forms. Sand smooth and glass with one layer of bias ply cloth. Remove from the form, clean up the insides, and glass to the same schedule.
Cut out a pair of closure bulkheads, one for the top, one for the bottom, and bond the bottom one and both halves together. Use 3 layers of double bias tape along the leading edge, inside and out. Round off the trailing edge and cover with two layers of 7 oz. Cloth. Lay the keel down on the trailing edge and glass the joint from the inside with 3 layers of double bias tape. Fit three 24" long pieces of 1/2" plywood inside the keel, 24, 48, and 72 inches aft of the leading edge. Glass these with one layer of 7 oz. Cloth, then bond them in place with epoxy adhesive. The top edge should end up ¼" below the top of the keel, where it will help support the top closure bulkhead.
Drill two 1" diameter holes through the keel sides, 6" from the bottom, 36 inches aft of the leading edge, one on each side. Be sure to seal the holes with several coats of resin. Fit the upper closure bulkhead to the keel, allowing a clearance of 1/8" around the edge. Round the lower edge and cover the lower surface and edges with one layer of 7 oz. Cloth. Clean up the upper edge and glass the top surface. Install a 1" plastic through hull in the upper closure bulkhead, 12" forward of the trailing edge. Fit a ½" plastic hose fitting to the through hull, and extend the hose up to the deck level. No pumps or valves are needed to control the water ballast, the keel simple floods when the boat is launched and drains when it’s pulled out.
FINISHING THE HULL
The outside of the hull is then smoothed and each joint rounded to a radius of 1-2 inches. Grind the deck flush with the hull panel, fill any holes, then cover with one layer of 20 oz. Bi-axial roving, cut for a 4"overlap at each joint. The hull should now be checked for fairness, and any low spots filled. Be careful to only sand filler, not the glass. Remove the dry wall screws holding the deck to the strongback, and break the boat loose. Turn it rightside up, and support it with a cradle or boat trailer. Don’t put a lot of weight on the keel until the floors have been glassed in place.
Clean up the deck surface and round off the hull to deck joint to a ½" radius. Cover the deck with one layer of 20 oz. Bi-axial roving, carried over the hull to deck joint and down the hull four inches. Add a layer of double bias tape, 8 inches wide, around the entire shear. Inside the boat, cover each hull panel joint with one layer of 8" wide double bias tape. Radius the edges and glass the cockpit to the deck. Glass over the inside hull to keel joint with 2 layers of double bias tape. The cabin sole can now be cut out and dry fitted. Be sure to cut a hole in it for the vent fitting, then put it aside.
FINISHING THE KEEL
Check out the local scrap metal sources and accumulate 900 pounds of lead. Tire companys are a good source for old wheel weights. Large pieces can be cut to fit with a band saw or skill saw. Pack the pieces together as close as possible, fill any gaps with lead shot (around 100 pounds will be needed), and flood the lead with resin. Catalize the resin with half the usual amount, so that it does not go off to fast. Cover the lead with a layer of 20 oz. Bi-axial roving. Make sure the flood holes are clear and that there is clearance under the spar for water to move freely, then install the upper closure bulkhead. Use plenty of adhesive, round off the outside edges, and cover with two layers of 7 oz. Glass, running it over the edge and down two inches onto the keel sides.
Install partial ribs (called "floors"), three on each side of the keel. These support the keel and transfer some of the load into the cabin sole. Put epoxy adhesive at all contact points the sole makes, especially on the top of the keel. Position the sole and weight it down for a close fit. Glass the edges to the hull with double bias tape.
DETAILS, COAMING-CABIN-COCKPIT
The coaming forms the sides of the cabin and outlines the cockpit. Its built from ¼" plywood, glassed on the outside, with inside saw kerfs every inch in areas with lots of curvature. In the cockpit, a second coaming is set inside the first, forming a comfortable back rest and a flat spot for winches and cleats. The cabin overhead is defined with temporary forms, and built from ¼ x 1 wood strips. The outside is faired and glassed, then the overhead is removed, turned upside down, and fiber glassed inside. Then it is put back in place and glassed to the coaming.
FINISHING DETAILS
The cabin details can now be firmed up, along with the electrical, water, fuel, and engine systems. Keep it simple, but don’t neglect the appearance. In my experience, it’s ALWAYS worth the extra time and money to include details that make your boat stand out above the crowd. Often just a little teak trim and a few bronze parts make all the difference.
Rig options: Cat boat or sloop, gaff or marconie
Power options: 1GM10 diesel, sail drive or conventional. 10 HP outboard (the Yamaha 10 four stroke, with a larger, slow turning prop is a good place to start).
The trailer will most likely have to be custom fitted. Make sure that a pair of bunks are set vertical, to keep the boat from sliding sideways.
Most boat projects are never really finished. There are always improvements to make and changes to evaluate. The important thing is to have fun with the boat – make it just the way YOU want it, and "enjoy".
MATERIAL SUPPLIERS
JAMESTOWN DISTRIBUTORS
(800) 423 0030
(Excellent single source for boat building supplies including screws, resin, fiberglass, and tools)
FAERING DESIGN, Inc.
Rt. 1, Box 223-W
Suttons Bay, MI 49682
(616) 271 6729
(Copper boat nails and traditional hardware)
FIBERGLASS COATINGS INC.
PO #60457
St. Petersburg, FL 33784
(800) 272 7890 or (813) 327 8117
(Epoxy and polyester resins, fillers, clothe)
Black seam compound: SIS 440, 941 756 0600, teakdecking@prodigy.net
HATCHES: from FISH-ON (1-877-2fishon); 11 x 15,and 13 x 23 hatches
More Hatches: www.cobra.com (16x10 and 23x13)