The Steamboating Forum

here's what I bought

For the 2 + 2 x 2 double acting engine, with 125 PSI steam at about 400 RPM, I would expect about 2 shaft horsepower, at steam cutoff about 50%. The engine could produce about 3-4 horsepower with later cutoff and higher steam pressure, but 2 horsepower would be more efficient, and will drive a 17 to 19 foot centerboard type fiberglass sailboat at around 5.5 knots with your 21 inch pitch propeller. The FAQ section of this forum would let you examine other options.

The Javelin hull I converted originally used an electric motor, however the modifications to convert it to a propeller driven boat would work as well with steam power (indeed, I now have a rather large steam plant in this hull). The photo shows the PVC pipe encased with fiberglass cloth and automotive repair resin. The orientation of the PVC propeller tube is set according to where the engine/boiler will be located, and tilted about 10 to 15 degrees from horizontal is typical.

Sand or grind the original fiberglass hull where you want the new fiberglass / resin to bond properly. Wear a mask as the dust is nasty. Wear protective gloves when mixing and applying the new fiberglass / resin.

With the centerboard removed,the sailboat hull needs to have "bilge keels" added to provide proper steering stability. I used aluminium angles, 2 inches x 2 inches x 1/8 inch thick, each 8 feet long. The aluminum angles are bolted through the fiberglass hull, with suitable silicone caulking to seal the aluminum to the hull.

Inside the hull, on the previous photograph, notice the bolts that secure the bilge keels. These bolts will also secure two long wood engine/boiler bearers, and form the foundation for the interior floor. The sketch here is a cross section drawing of the hull, illustrating the fabrication:

One method of fabricating the bilge keels and wood engine bearer is to fabricate the bilge keel, secured with 1/4 inch diameter bolts about 3 inches long, ordinary nuts, and silicon caulking. Let this assembly cure over night. This is the condition in the first photo I posted here.

The wood engine bearers are fitted, and 1/2 inch diameter holes drilled to accept the bolts that protrude into the hull interior. These holes in the wood are a very loose fit for the bolts, which are about 1/4 inch diameter.

At this point, the holes in the wood bearers are filled with automotive repair "Body putty", with a generous coating of this stuff all along the bottom of the wood bearer. The wood bearer is then pressed over the bolts, and clamped down to the original hull, with the excess body putty squeezed out between the wood bearer and the fiberglass hull interior. This body putty is the same (or similar) chemical composition as the resin used to secure the propeller shaft tube, and permanently glues the assembly together.

Practice with the putty before doing the final work. It hardens in about 20 minutes, and has a working time of 5 to 10 minutes, so have everything ready, trial fitted, clamps ready, and do a rehearsal before starting the actual work.

The propeller shaft will exit the PVC tube for some distance, and requires a bearing just before the propeller is fitted. I made a bearing support from a piece of steel flat bar, and the actual bearing is a food service UHMW plastic material, fitted in a stainless steel spherical mount. When I made this the UHMW bearing, for a 1 inch diameter shaft cost about $20.

The mounting is shown in the attached drawing, secured similar to the engine bearers. This arrangement has functioned well for 17 years, running several years with electric motor drive, then with a 13 horsepower IC engine, and now finally with a new steam plant. A 14 x 17 propeller was fitted to my Javelin, and has endured several groundings. The clearance between the hull and propeller needs to be 10-15% of the propeller diameter.

So there you have it, $107 cost on ebay, converted to a propeller drive boat with well under 2 weeks spare time work, with two cans of Krylon spray paint, still excellent after 17 years.

Hi Ivan

Another thought for you brought about by an amble in the sun by the harbour yesterday. Look out for boat clubs with boat parks. You are very likely to find effectively abandoned sailing dinghy hulls that the Club might well be glad to be rid of for next to nothing. I saw yesterday what looked like a GP 14 disappearing under the brambles and bush but that might be too small for your plant.

Regards

Pete