UK F3F flyer Adrian Bedford talks about a joint project to design a new F3F racer.
MS: What is the background to this project ?
AB: Both Alex [McMeekin] and I have designed and built a fair few models. My background in composites goes back about 8 years. I have done numerous Yachts, lost foam fuzes, carbon undercarts and Kevlar bits and bobs and other experiments. For the last couple of years I have been producing the Apache and Agressor fuselages for Soar Ahead Sailplanes down here in Sussex. How many people do you know who have used up in excess of 150 sq. metres of 200gsm glass cloth and over 2 gallons of epoxy, purely on fuzes!
Alex has more experience with wings than I do, and is also starting doing some fuselage moulding, neither of us have done a moulded wing as yet. Both of us carve our own plugs from a pattern makers wood known as "Jelutong".
MS: What processes are involved in getting to the mould stage?
AB: First we produced a virtual models on a computer. The models were done using AutoCAD to create the fuselage profiles, wing sections etc and then 3d-modelled in a program called Rhinoceros (http://www.rhino3d.com). Plotting out the fuselage profile full-size led to the plug being made very quickly. The data is 100% accurate to within .0001mm. From the solid models it is possible to go straight to CNC machining of moulds/prototype wings etc.
The 3D models shown here are only at a rough stage, the pylon area needs work and the tip dihedral needs to be added. At the moment they are just so that we can see exactly how it will look, on the computer it is possible to rotate it around and see it from any angle.
MS: How are you organising the work between yourself and Alex?
AB: So far Alex has come up with the planform and run it through the triple taper computer program, he has optimised the layout to give the best lift distribution and stall behaviour. I have done the design of the fuz and tail and the solid modelling. We have had the fuz plug turned and will I am sure get together to make the moulds for that some day soon. We will be trying to split the work as fairly as possible.
MS: Do you have any particular design goals as regards construction, e.g. speed of prototyping, ease of manufacture etc.?
AB: The main goal for me is to have most of it done before I go back to university in October (Final year, no building!) It would be nice to see the first one by then. If this is realistic or not is another matter!
MS: Have you decided whether to go straight to the final product or will you make a "cooking" version out of foam first?
AB: Haven't really thought about this. As we are doing the fuselage first it would be fairly easy (sensible!) to do a foam wing and see how it goes, before committing to making wing moulds.