Wonwings diary-Building from plans-Building with Blue Foam-Part 8
Mention of blue foam log construction has prompted a few enquiries from you,so before we proceed any further lets just discuss this useful process,there are times when complex shapes are time consuming to produce in traditional wooden keel,former,planked construction,with the advent of remarkable building insulation foams this has brought with it a material that needs to be explored and experimented with by the model builder,its good points are that it offers light weight throughout, coupled with the ability to be under shaped in tricky areas,ie engine intakes and area ruling on modern jet types,the modeller instantly becomes a sculptor overnight in his own right and the shape process spurs you on to get the model completed.Basically we use builders blue insulation foam,check in your yellow pages and sort out your local dealer,go along and take a ripsaw with you,you will need to rip through the panels before they go into your car ! do not put them onto your roof rack otherwise you will loose them,the panels are huge so need cutting down into manageable panels,best place to store them out of the way is in the roof of your garage.
The very first job is to make a side view template of the fuselage, in the case of the model aircraft here,boats and cars receive similar treatment,make this from coloured sugar paper or similar coloured card,the reason for this is that it forms the constant centre datum of your 'log' whatever carving you do the centreline will always be present,glue the pieces together with Aliphaetic resin glue,you can also use PVA but this will take longer to set as air drying is difficult and slow between the tight laminations,you can use balsa dowels if you wish,but this is not necessary,a black marker pen is used to mark any important areas,add plenty of datums,even pieces of wood can be tacked into place to guide your eventual carving.Do all cutting outside as this stuff gets everywhere clinging to everything in your workshop,wear old clothes and nothing that attracts too much static,a boiler suit is fine,prepare yourself for a big sweepup later and a blue lawn ! having said this the work and mess is worth the effort,a quick water spray settles the debris we just have to live with the inconvenience,wear goggles to protect your eyes from flying debris.
The next process is to shape the log using the cross sections provided on your plan,have plenty of photographs to hand also so you know exactly what needs taking off,the best tools are as follows- a bread knife,surform woodworkers tool,a clean new wire brush,sharp long knife blades such as the Stanley 2901 series,a keyhole saw and a sharp razor saw,lets explain each tool and its use;the bread kife will hack through large areas of the block,the surform is your best friend and will happily rip through the largest of chunks of foam,the wire brush is uncanny,by striking the foam or stroking it you will quickly realise its potential,the carve up process is very theraputic as the shape takes place before you,the long knife blade will enable you to get into the corners such as the intakes,the keyhole saw will deal with internal area removal,simply push the blade straight into the foam and draw back and forth,the razor saw makes nice clean cuts on the final clean up.
Use the roughest carborundum paper to achieve the shape after major cutting with wire brush/saw/knife,the trick is to go from left to right with the sanding block and cut the top off the beads of foam,a bit difficult to explain but you will soon get the idea in actual use,note from the picture below that any formers,spars or inserts are simply slid into place at this stage,do not glue anything yet ! they will just serve to get everything in line,speking of which can you still see the edge of that coloured paper ? clever eh ! you will never loose that crucial datum point.
So we now have in front of us a well shaped lump of blue foam,note how light it is ? but wait a minute we have not even started to remove the surplus weight,tomorrow I will explain how to finish the log properly and get the most from blue foam consruction,see you here.
