Building the AsTec Micro Shovel Nose Hydroplane
The AsTec Shovel Nose is a semi scale unlimited hydro for 400 or 480 motors and 6 or 7 cells. Small brushless 20 or 24 series can be used as can Lipo power.
We recommend that you use Liquid poly for plastic to plastic joints and epoxy for wood to plastic joints. When using epoxy be sure to rough the surface with sandpaper to provide a key
We recommend that you use Halfords acrylic paints. Use of a thin undercoat after sanding with 220 grit wet or dry gives the best result. NB: Plastics are prone to long term damage when in contact with some chemicals. This is generally exhibited by the plastic becoming brittle with time. We therefore strongly recommend that you follow our recommendations.
Start by trimming round the top and bottom halves of the hull. On the bottom so that there is an approximate 5mm lip all the way round the edge.
Identify the access hatch in the hull top and cut it out, this is best done by light scores with a knife. I extended the hatch area on mine to give greater access - don't go too far forward or the hull will be liable to twist.
Line the inside of the hull top round the access hatch with 5mm wide plastic strip to provide a location for the hatch.
Decide where the turn fin will be located (inside, outside or rear of the right hand sponson (from the rear!!) Double the area with two layers of 2mm light-ply or similar on the inside of the sponson..
Use light-ply or similar to double the transom. Place the light-ply on the outside of the transom and draw round it. Cut it slightly smaller shamfer the edges to fit the hull. Glue inside the transom.
Sheet the bottom of the transom with 40 thou (1mm) plastic. Draw round the sponson directly on to the plastic and cut out. There should be about 0.5 mm overhang on the sides and the rear.
If you wish the rear of the transom can be improved by lining outside with plastic, filling the gap and sanding smooth. In all cases the idea is to get sharp clean edges to shuck the water off.
Determine your layout by dry fitting the motor cells and radio gear etc. - Move it around until you get a good arrangement that puts the centre of gravity as close to the rear edge of the sponsons as possible and as central as possible. The tail of the propeller should ideally trail the transom by 25-35 mm and the bottom of the propeller boss should be at the same level as the bottom of the sponsons. This effectively sets the motor position! This model has only been tested with a flex drive and we feel that this is the only suitable solution. You should set the drive with about 3-5 degrees of down angle. An Octura P431 (plastic) is a good starting point as a prop. The motor will require water cooling.
Please feel free to discus any problems you may encounter with us.