Fitting a Yanmar and Aquadrive

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Installing the stern tube and modifying the skeg :

An extension piece can be moulded from epoxy and glass cloth, formed around a Styrofoam core. Styrofoam is easy to shape with a saw and glasspaper. Polyfilla (or similar) can be used for filling and smoothing if you have trouble getting a smooth finish.

This skeg was formed with 2 layers of bi-directional woven glass cloth and SP106 Epoxy Resin. It's really worth investing in all the protective gear such as rubber gloves and epoxy hand cleaner before you start. A wooden or plastic spatula is a good tool for laying up - it helps in forcing the resin into the cloth and ensuring it is completely saturated.

skeg layup

Fig 1 (above): The foam core and glass cloth cut to size, ready to start laying up. I found the paint brush fairly useless for this, as it failed to force the resin into the weave of the cloth, so I used the mixing spatula instead. It's important to make certain that the cloth is totally saturated with resin.

Materials

Fig 2 (above): Cling film (or polythene sheet) is useful to protect anything you don't want to stick epoxy to. SP Systems resin and hardener was used, with biaxial glass cloth. Ordinary chopped strand mat can't be used with epoxy as it contains a styrene binder that epoxy can't dissolve.

trial fit

Fig 3 (above): A trial fit of the extension piece. If you make it the correct thickness it should just wedge into place on the leading edge of the existing skeg. An angle grinder with an abrasive disc (40 or 60 grit) has been used to clean up the area which will be bonded - but the final fitting won't be done until the stern tube is in place. When that time comes the gel coat will be sanded off to give a good bond to the the underlying GRP of the hull and skeg. The red lines are markers in the woven glass cloth which show the direction of weave. For maximum strength the layers of glass need to be laid at different angles.

hole for stern tube

Fig 4 (above): The worst bit - drilling the hole for the stern tube. Measure thrice, check twice and cut once. I cut the hole by chain-drilling with a 5mm drill and cleaning up with a coarse half-round file. The hole has to be elliptical in shape because of the angle of the tube. I used a marker pen to draw the angle of the tube (as seen on the leading edge of the skeg). When I cut into the skeg itself I found it was hollow. Luckily, there was just enough room for me to slide the stern tube through the skeg (I had to smooth a few lumps down with a coarse file to help it fit).

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