Dennis O'Connor is correct when he says that a cyliner moulded hull will cost a fraction of building a plug, taking a mould off a plug and then taking a glass hull out of the mould. But the point I would like to make is that; no body actually does that for a custom design. If you were building in timber you would possibly use the strip planking method and probably the split half technique. In this case you would only use CNC cut frames. You would not put stringers on them like is required for cylinder moulding. Like the cylinder moulding you would only use half frames and probably use female frames so the half shell would just lie inside the frames with very little requirement for fastenings. Of course you could use stressed ply [tortured ply] construction and then all that is needed is a deck jig.No mould at all! If you were building in foam and glass [you would not build in solid glass] then you could use strip plank foam in exactly the same way as described for the strip plank cedar composite technique. You could also put a few stringers on the female half frames and use virtually whole sheets of foam running from gunwhale to kelson if the distance was suitable. So all of these other methods of building a "one off" are probably going to cost around the same as the cylinder moulding and take a similar amount of time to build. And of course he is absolutely correct:- the hulls are only a fraction of the cost of the complete boat and are also probably the easiest part of the boat to build. So at the end of the day it probably doesn't make much difference which method, or material, you use for the hulls.There will be a lot more material, and considerably more time, involved in building the bulkheads and installing them. Regards, Malcolm Tennant. ARINA MA Malcolm Tennant Multihull Design Ltd PO Box 60513 Titirangi, Auckland 1007 NEW ZEALAND ph +64 9 817 1988 fax +64 9 817 6080 e-mail malcolm@tennantdesign.co.nz www.tennantdesign.co.nz www.catdesigners.com