| Alan,
Having built a couple of these in my lifetime, both the wooden and f/g version, the first advice before anything else is KEEP IT LIGHT. Anywhere you can put a lightening hole without it showing on the finished model, do it. Just a massive weight reducing exercise. Resin, rather than white metal fittings, it all helps in the long run.
As Bunk said, it is a rather difficult process to get them running really well and onto the plane. They were designed for ic engines which means that to run them on electric takes them into a different ball park. Ic engines gave you a very good power to weight ratio, so they went like stink from the start, but electric propulsion is only just now beginning to catch up with cheaper versions of brushless motors and their related battery packs and controllers.
Rather expensive at the moment.
To keep things light, I personally would go for racing packs rather than gel cells, and say graupner BB motors for the power and put up with the limited run times of about 10 to 15 mins. Get a couple of packs and a pondside charger and you should, if timed right be able to sail, and have a pondside chat while preparing for the next run.
Just to reiterate, if you want it to plane, you will have to get some decent power into it and keep the weight as low as possible.
John |