GTM Eagle 6-8 cell stepped mono surface drive race boat

Eagle Build Instructions

The Eagle is a stepped mono that is suitable for running from 6-8 cells. The Eagle was designed primarily for competeing in the mono1 class, and whilst it is a relatively cheap hull it is extremely competitive in this class.

Before we start, please note that some glues and paints will cause ABS to harden and crack, please only use the recommended materials. Please also note that Ultra violet can cause damage to the ABS so store your model away from direct sunlight. Weight is your enemy - build light and strong.

The Hull

First roughly trim the hull and deck so that they both have a 5mm lip all the way around. DO NOT TRY AND CUT ALL THE WAY THROUGH EXPERIENCE SHOWS THAT THE CUT WILL WANDER. Gently score the plastic with a sharp knife until you have cut half way through - then break the excess away by flexing the plastic along this line. Trim the deck out in a similar manner. Release the hatch inner moulding by cutting it parallel to the surface of the parent sheet DO NOT CUT ALONG THE MOULDED IN LINE. You can use a layer of masking tape on top of the plastic - this sometimes helps to stop the knife blade slipping. Trim the waste out of the centre of the hatch cover and sand away sharp edges.

CARE a slip here will destroy your hull. Carefully cut along the outline mark on the deck top to free the hatch. Glue the hatch inner moulding inside the deck - the marked line matches the cut line on the deck.

The Eagle mould has been produced with a lip on the running surfaces. The first thing to do is rough up the mould on the inside of these lips and fill with epoxy - we suggest stability express but any other epoxy will do just as well. You can also use a filler such as micro balloons with it. When the filler is dry - scrape the blips off flush with the running surface. We use a bare blade from a Stanley Knife for this.

The top of the step is thin 9from the moulding process and although we have never had a failure you may wish to reinforce this area as well. Bear in mind that you need to build light!!

Next re-inforce the inside of the transom with light-ply. Put the ply on the outside of the hull and draw round it. Cut it 1 mm in from the lines and round over for a good fit, epoxy in place.

You can now glue the hull together or wait until all the hardware is in place. Use any recognised ABS glue for this. EG pipe weld, Liquid Poly etc - if in doubt try it on a scrap first. Be careful these glues melt the surface of the ABS - we do not want it to melt the whole boat.

Hardware

The drive will exit the hull from the centre of the transom drill a small central hole and open up to fit. With either flex or straight drive the aim is to get the bottom of the prop boss on a line between the peaks of the step and the transom - (See drawing).

Our straight drives come with a foot on them - this can be discarded to get the motor lower on the boat. You can use light-ply with a hole in it that will fit over the nose of the motor mount instead. With other motors build a suitable mount from Lightply. Remember to allow room for any water cooling that you fit and do not block air holes. The motor goes immediately forward of the step.

Once satisfied with the position fix everything in place. The rudder assy goes on the RHS of the boat (Looking forwards).

Radio and Electrics

The cells go down the left of the motor and shaft. Radio at the rear. Speed controller at the front RHS. Servo mountings can be made from light-ply and glued in place - make sure that the rudder drive shaft does not bind.

For racing in the UK and Europe, you need a safety loop on a non removable part of the upper hull/deck of the boat. This is simply a re-moveable plug in positive motor battery lead outside the boat. We use a 4mm gold plug pair with the female glued through the hull, and the male on a cable loop. The loop may be mounted on the transom but must be well clear of the propeller. If the radio uses its own battery - that must have a similar (but smaller) safety loop.

The C of G is marked on the drawing - you may have to move this slightly for best performance, and it will vary dependent on whether you use a flex or staright shaft (due to the lift effects). Moving the C of G by a few mm can have a significant effect. If you use a flex drive you can offset the motor to the right to allow the whole battery pack to be installed on the left.