martno1fan

Hi ok so you want to lengthen the boat and fibrglass the outside ?,easy enough balsa on the inside to lengthen and join the two parts together then you could use abs to fill the gap,then a little filler ,next you need to decide wether your leaving in the abs or removing after.If leaving simply scuff up the outer then use slow epoxy and some thin cloth lay alayer let it fully set,once this sets you can build up the layers using some thicker cloth say 200g cloth maybe 2-3 layers one at a time,use an old credit card to remove exess resin between layers.Reason im saying do it in seperate layers is to keep the heat down during curing so as not to melt the abs.I cannt say it wont melt the abs as ive never tried it,it is a possibility.If alls good when your done you will have some serrious wet sanding to do to get the running surface nice and smooth,another reason to use the credit card to get rid of exess resin before hand.You will also need to seal the balsa inside when done with epoxy resin.
Mart