Bill Garrod's Arbalest Evolution Build

Well I've made a good start on my new Arbalest Evolution and have progressed the fuse as far as I can before needing to build the wings and stab. This model will be very similar to my current Arbalest- same wings, all moving stab and taller rudder. 

Before starting I always set up a spreadsheet showing the predicted weight at every build step. When each step is completed I update the sheet so that I always have an up to date estimate of the completed weight. Yes I know I am obsessive about weight!!! Have set a pretty challenging target under 4500 grams with an 1185 gram power battery pack. Under budget so far. The other thing I am doing this time is logging my build time just to see how long it really takes. 

The fuse is built using three vacuuming steps. This is not the way the professionals do it but I am still fairly low down on the learning curve and it does seem to work OK. The first vacuum is to shape the balsa, the second is the 1.5 oz cloth/ balsa layup and the third is the inner 1.5 oz cloth layup. I used red resin tinter on the last step and found it easier to see the dry spots. Actually saved about 15 grams of resin a side on this layup. A lot of the excess resin is drawn by the vacuum into the felt breather cloth. This typically removes about 35% of the resin applied. The fuse side moulds are bolted together and joined with a strip of glass cloth. The carbon fibre reinforcement for the under carriage mount and the motor mount are done in the last layup.  Once the fuse is out of the mould it's just a case of doing the internals. Made two different U/C mounts - one was 16 grams lighter than the other. No prizes for guessing which one I used! Carbon balsa laminate for the plate and carbon Nomex honeycomb for the formers. The whole structure is "glassed in " with some more carbon cloth. The mount is pretty low to allow a shorter(therefore lighter) undercarriage. Moulded the carbon undercarriage myself to get the length I wanted. The motor mount for the Plettenberg Advance is very simple - F3A Unlimited aluminium front and rear mount supported on four ply blocks and 4 4-40 bolts. Made the rudder servo mount from carbon Nomex honeycomb and the cooling duct for the Spin 99 speed controller from 1.5 and 3 mm Depron. The air outlet ducts are glass cloth moulded around a drinking glass.

The foam for the wings, stab, rudder and cannaliser is already cut so will be starting on them next. Couldn't get the lightest foam I have been using so the wings will be maybe 10-15 grams each heavier than I would like. So far I have put in 62 hours of build time and am quite happy with progress.

Bill Garrod.

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Arbalest Evolution Pictures December 2014