Articles
| Foam F14 | ||
Credit Crunch JetsWhere did this all begin? After watching Top Gun Ian always wanted a model F14. After flying in the 2007 Jet World Masters and owning a number of turbine models, we thought there must be a cheaper way to fly large jet models. The idea of building a large foam jet occurred to Ian and he discussed this with a couple of the other guys who agreed to help. Others thought it was a silly idea. So, the work began on the mark 1. We drew up a plan and cut this out and spray mounted the parts to cardboard to make some cutting templates. As this is a prototype the overall shape was less important than the flying abilities. The foam used was polystyrene from our local hardware stores, Islandbawn Stores. The sheets were 8ft by 4ft and one inch thick. Cutting began using a wood saw but we found a hacksaw was able to give us a cleaner cut. There was no hot wire cutting used on this model
We began with the nose section and glued the parts together with Copydex contact adhesive. Next came the engines and while these set the main wings were cut and shaped. We decided to go with all moving tail planes and not to use ailerons at all. This removed the need for two servos and helped to reduce weight.
We also decided to use a dolly rather than fit an undercarriage again to save weight. This had an onboard receiver to give us a steerable nose wheel. However, the takeoff run was so short this was not really necessary. Taxi looked good though.
To be safe the entire airframe was then covered in glass cloth and epoxy resin to add some strength. This was the most time consuming part of the build which was very fast up to this part. The mark 2 will be built from blue Styrofoam which is much stronger and sands smooth. This will not need glass clothed and will save both time and money. Two 8ft by 4ft sheets have already been bought form Charles Tennant and Co. for £19.78 inc VAT.
We decided to put an electric motor on the prototype and the test flight had a 13x8 ic propeller as we did not have time to get an electric one. The motor is 600 Watt with a 70 Amp speed controller. The battery is a 4900mah 5 cell Lipo with a 2400 NiMh battery fitted to power the radio. The servos for the elevons are JR 591s with the wing sweep driven of a old quarter scale Hitec servo. A lot of help and advice was provided by Robert from Mid Ulster Models, where the motor was sourced.
The model is 84 inches long with a wingspan of 86 inch. (Wings extended), and has a ready to fly weight of 10 lb.
Total cost Motor £30 Speed Controller £17.50 Servos 591 £9.99 each Hitec from previous project, forget the price. Battery £190 Radio battery £15 (ish) Receiver £49 Foam £8 Copydex £9 (only a very small amount was used, say £1) Epoxy resin £15 Glass cloth £35 Plywood £10 Dolly (optional at your own risk) Wheels £5 Reciever £49 Battery £10 Wood £10 Total cost including the dolly before paint £464.48 However, £190 of this is the battery that can be used in other models.
Now, the interesting part, the test flight. The take off run was short and she left the dolly with out drama. Two clicks of down trim and two clicks of right were required for hands off. After a few circuits the wings were sweep back with little change to the trim. The model was no different to fly in this configuration. The speed was very scale, changing to an electric prop will be the next test, with a larger motor a possibility, but not essential. The model was very stable in the air and still responsive to the controls at low speed. The landing was similar to any other smaller foam model with plenty of lift of the extended wings with the touchdown straight in line with us.
The prototype has proven to be successful and the mark 2 is already in production.
Those crazy enough to get involved; Ian Pilot, originator, builder and poor sod who paid for it all. Peter builder, build photographer, transmitter programmer, and also a believer from the start. John builder, glass cloth doctor. Stephen test flight photographer. David supplier of the credit card that put on the glass cloth. Chris non believer now converted. Stanley safety officer and crowd control Adam believer and future owner when painted. And special guest appearance by a founding club member who flew in from England for the occasion, Mr Jess Wright. More images including flight shots
Watch this space!
By Ian Robb and Peter Carson
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Langford Model Aviation 2010