FAI and BMFA rules stipulate a minimum surface loading for models in F5J competitions: 12g/dm2 (12 grams per square decimetre – 3.93 oz / sq ft in old money). Some models (especially 2m and smaller) may need ballasting to comply.
Some 2m RES examples:
So, for example, the Viruta (first row above) has an FAI area of 38.7dm2. Minimum weight for F5J: 464.4g (38.7×12). Model in the table weighs 393g unballasted. So it would need a minimum of 71.4g ballast for F5J. Obviously, be careful with any lightly-built model that it will be OK with the extra weight).
More examples needed
When you do the sums for your own model, please send details to whitstable.nick@outlook.com for inclusion on this page. (Especially useful to build a list of minimum weights for popular commercially-available models.)
The small print
- FAI area for calculation of surface loading is wing + tail areas. (That’s vertically-projected areas – important in the case of v-tails).
- This page is about F5J, not other classes.
- Minimum surface loading applies to larger models too – but less likely to be an issue since big models mostly have a higher surface loading than small models. (Pilots of ~3m models should also do the sums. There are now extra-light ‘FAI’ 4m models close to the limit but manufacturers generally make sure they comply.)
- This page is just listing information supplied to us, as a guide – SFTC/BMFA are not warranting its accuracy.