Free Flight Scale

I have just watched a video of Monz's Robber powered Shackleton flying at the Oxford MFC scale fest.

Although it is only about 40 seconds the flight is really good to watch, very stable and smooth. Fantastic job Monz well done.

Looking through YouTube there are some quite fantastic rubber powered F/F scale - how about a Donier Do IX(right number)?
Mike

G'day,
About to build f/f scale model of the Stewart Headwind.
Wondering if tail-plane areas are allowed to be increased for F.A.I. F/F Scale event.
If memory serves me (questionable!) from years ago a certain % increase was allowable
for tail surfaces, but can see no mention on current F.A.I. site.
The Headwind has about 15% tail-plane area, would this be sufficient for F/F if no increase permitted?
cheers from Australia.

Andy Sephton will tell you the answer to that one flight risk

flight-risk wrote: G'day,
About to build f/f scale model of the Stewart Headwind.
Wondering if tail-plane areas are allowed to be increased for F.A.I. F/F Scale event.
If memory serves me (questionable!) from years ago a certain % increase was allowable
for tail surfaces, but can see no mention on current F.A.I. site.
The Headwind has about 15% tail-plane area, would this be sufficient for F/F if no increase permitted?
cheers from Australia.

Hello flight-risk and welcome to the Forum. When you have a minute, an introduction post would be appreciated on the introduction thread so we all know who we're talking to. It also helps to know the level at which to respond... Either way, you should get a good welcome.

www.aeromodellers.co.uk/forum/thecafe/10...-yourself?start=1515

As for your question, the answer will depend on the competition you are building the model for. If you're not building for competition, then increase the tailplane size as you see fit.

I'm not aware of Australian Scale Rules, but in the UK, any increase in tail size is penalised. The FAI rules tend to mirror those of the UK, which can be found here:

bmfa.org/DesktopModules/Bring2mind/DMX/D...PortalId=0&TabId=219

A 15 % tail is not a major issue, provided you make the section symmetrical or downward lifting. Lifting tails work on duration models, but they reduce the efficiency of the tailplane on scale models as, for stability, they must lift downwards. If you do go for a 15% tailplane, you'll need a C of G further forward than normal. Say 10 - 12%.

Without any further info, that's all the advice I can give at the moment

Thanks Andy,
Yes will be for competition, will go with 15% symmetrical.
NOW for that intro page.......
cheers
gregj

You're welcome Greg.

Thinking about it, if you do go for a 15% tail, the forward C of G required will need a lot of decalage (longitudinal dihedral). The issue is then that the angles of the wing and tailplane look wrong when the model is statically judged. A change in wing angle may also effect the model's 'sit' in the air. So we make all the control surfaces moveable. This adds to the scale points statically and allows the elevator to be set up to trim the model for flight.

If you'd like a real time chat on this, hit the Live Chat button to the left of this window. I'll be there for the next hour or so.

Good luck with the model.

Would it not be possible to make the wing or tail incidence adjustable with wedges of predetermined size by testing . Slipped into place for flight and out for static judging . Just a thought

one tenor wrote: Would it not be possible to make the wing or tail incidence adjustable with wedges of predetermined size by testing . Slipped into place for flight and out for static judging . Just a thought

Yes, good idea.
Have been "re-honing" my free-flight skills (?) after many years away on sport type models
before having a go at f/f scale, and have used this method to get stable flight.
Should be able to use your idea of removable shims nicely in scale.
Just gotta remember to replace 'em before flying!!
Hope this reads ok, 0200hrs and just finished 12hr ambulance shift.
Cheers
gregj

One needs to be very careful with changing the configuration of the model between static and flight judging. Moving control surfaces is allowable, but changes of incidence of flying surfaces, unless an all flying surface, may be penalised by the flight judges.

I wondered about that too but I guess its a slippery slope from having changeable incidences to having scale static and enlarged flying tailplanes !!! which surely isn't right. I had assumed the static part was judging the aircraft that flies.

The scale prop is the obvious exception are there any others

OK.
Any changes made to main-plane incidence can be made "permanent".
Elevator will be hinged for minor alterations.
Will have down and side-thrust on engine.
Mainly trying for a good flyer on first attempt, fidelity to scale on later models.
Cheers.

Chris - the exceptions are in the Rules and Judges guides (I've posted links to those in other threads). I believe the only exceptions are, as you rightly say, the static prop and the pilot, who, if fitted, is not judged in static.

Good thinking Gregj, getting it to fly in front of the judges can be the hardest part and is best sorted early! The model you've chosen has a short nose. So, owing to the short moment involved, it'll need a lot more down and side thrust than would be thought normal. The trick will be to keep the prop driver in a correct scale position with the engine at a relatively large angle to the fuselage datum.