Revised 20-20B web page
17 July 2005
Model 20-20B
URL   hosted by as a tribute to Walt Murray

Please note that this site is being reactivated after about a year and
 there are many missing and revised files. I am trying to retain most of
the old 20-20 files but I need to cut much of the old pages to be able to
fit my allowed web space on my ISP server.  The new version is 20-20B


            Model 20-20B    June 05

            These drawings reflect the evolution of the basic 20-20 design with many
            changes to the detail parts and new features such as provision to swing the
            oar out of the water for protection around docks and reduce growth of
            marine plants and animals.

            I have had many requests for a complete set of drawings that could be used
            to build a model. I think this set will do that.
            The only decisions needed to be made by the builder are the choice of a mounting
             scheme and the length of the oar to fit his boat.
             Simple construction using readily available materials is the basic design goal.

            20-20B-4.jpg (27252 bytes)  Model 20-20B overall view
            The support frame is plywood and the vane mast support is UV resistant PVC
             ridged electrical conduit.

           20-20b-2.jpg (37068 bytes) Parts list page    20-20b-3.jpg (59260 bytes)            20-20b-5.jpg (49288 bytes)    

           20-20b-8.jpg (50253 bytes)      20-20b-9.jpg (47864 bytes)      20-20B-10.jpg (47921 bytes)    20-20b-6.jpg (61701 bytes)

           20-20b-7.jpg (41492 bytes)         20-20B-11.jpg (44064 bytes)  Prototype under construction
           shown mounted on a copper tubing frame mount on a
           simulated transom.

            Copper mount_12.jpg (14334 bytes)  A typical mounting frame. This one is of copper tubing

            Copper mount_1.jpg (23586 bytes)   Prototype mount for this presentation.

           CuTest-15 Nov03.jpg (96999 bytes)     This bit of copper pipe has been mounted in the tide
           line in South Florida for several years and shows no signs of structural
           damage other than the green oxide film.

           20-20B-12.jpg (48960 bytes)    20-20B-13.jpg (38154 bytes)    20-20B-15.jpg (60960 bytes)   20-20B-16.jpg (42092 bytes)

           20-20B-20.jpg (37084 bytes)  Showing oar rotated out of the water for safety
           around docks and to reduce build up of marine growth when
           not in use.

            20-20B-18.jpg (15358 bytes)  Showing how to laminate the shaft hangers from
            Three layers of plywood. The middle layer is cut away to make
             drilling for the support bolts easy. After the epoxy has hardened
              a drill will easily follow the cavity and result in well aligned parts.

           A version using PVC for the shaft and bearings proved to be a
            good way to build and is both easy to make and is quite strong.
            The assembly is a bit tricky at first look but by cutting the slot shown
            on the end caps and using at least 1-1/4 size pipe the crankshaft
            and other parts go together with enough clearance. The caps are
             cut to fit in the photos but need not be made so short.

             20-20B-23  Exploded hanger detail.jpg (37099 bytes)  The main pivot shaft is the gray PVC pipe and the hangers
             are the same ones in the previous photos that have been cut to fit the
             larger PVC pipe. The bolts go through the cut off fitting and the pipe but
             clear the control shaft. The slot in the end cap will allow it to make the turn
             at the bearing point.

             20-20B-25PVC shaft and hanger parts.jpg (24534 bytes)  Parts ready for assembly   20-20B-22  Exploded hanger detail.jpg (55285 bytes)

             20-20B-24 PVC shaft and hanger.jpg (28060 bytes) More detail                          20-20B-26_crankshaft assy-3.jpg (31898 bytes)    Assembly of crank shaft parts

             The crankshaft supports can be assembled after the shaft is pre bent by turning
             the PVC caps with their slots to slide past the 90 degree bends.
             The caps are cut to length and drill for a loose fit on the shaft. They are retained
             on the gray PVC pipes with a # 6 x 1/2 self tapping screw.



            Notes on building the parts---

            The first decision to be made in building or buying a self-steering device
            is how to mount it on your boat. This design provides for many options.
            A simple plywood platform fastened to the boat's transom or deck or
            metal pipes, extrusions or welding could be used . The copper frame
            I show is quite strong enough. I use type " L " copper fittings and pipe.
            Soldered with ordinary plumbing solder will work. A good water tight
            quality joint is certainly not needed. With the short lengths needed I
            find scrap or used material is a very good way to cut costs.

            The plywood shown is 3/4 inch . Use a good grade of pressure treated pine
            or use epoxy to laminate stock. The oar can be made that way with the
            lower part of the blade being only two layers of 1/4 ply. This can result in an oar
            that is as strong as the wooden props used on light aircraft.

            The bent up metal bar parts are formed from 1/4 x 1.0 extruded aluminum
            sold in building supply or hard  ware stores. This material is in the annealed state
            and can be held in a vise and bent with a large hammer. 

            The vane mast is PVC. Use rigid electrical conduit for added UV protection.

            The vane blade is a light weight 1/4 plywood lightly coated with epoxy resin.

             Details will be filled in as I go---  Please contact me if you need help now at

            data       17 June 2005