wonwinglo
SMF Supporter
- Joined
- Apr 18, 2004
- Messages
- 6,754
- Points
- 113
- First Name
- Barry
Most scale subjects have too small a tailplane to support our model replicas,so we have to enlarge the surface area to a sensible proportions if the model is to fly well,from past experience this is a trial and error cut and see situation to get the best results,even the full size designers struggle with tails witness the number of prototypes that receive changes during their test flying stages.
The next thing to consider is a lifting tail or flat stab ? lifting tails can prove useful or a problem to trim,what actually happens is the lifting tail will produce more lift than a standard flat plate design pushing the nose forward ( or lifting the tail end) as the surge of power is at its peak,my old Air Cadet replica has a wonderful flight path in this respect,you can see the tail markedly dropping as the power dies off and the nose raises for its landing,so for that model which has a long moment arm it proves very suitable as a built in automatic pilot.
However for most of our purposes and as a safeguard for the relative beginner a flat tailplane will be adequate,it is just something to keep in mind as a way of trimming out a difficult design and could prove useful to you one day so dont loose any sleep over this.
As regards the construction of the tail,as always and I know that I keep repeating this ! build it light as possible but reject any kit tails that are built up, from too many alternating grain curves that are multi cemented in a circle !! these are almost guaranteed to warp beyond anything resembling a flat tail surface,all that is needed in a wide trailing edge,a curved strip leading edge bridged with strips across,make sure that this is left on the board whilst the adhesive cures for 48 hours minimum before you un-pin it,otherwise it will start to twist.
However it is easy to build a new tail,even thin sheet ones with inserts of cross grain built in are adequate,best of all with these they can prove useful for determining th tail area we have spoken about.
I am a great believer in experimenting and these small cheap models prove good platforms to try out your design or building ideas,it is all a big learning curve,but what fun it is !
The next thing to consider is a lifting tail or flat stab ? lifting tails can prove useful or a problem to trim,what actually happens is the lifting tail will produce more lift than a standard flat plate design pushing the nose forward ( or lifting the tail end) as the surge of power is at its peak,my old Air Cadet replica has a wonderful flight path in this respect,you can see the tail markedly dropping as the power dies off and the nose raises for its landing,so for that model which has a long moment arm it proves very suitable as a built in automatic pilot.
However for most of our purposes and as a safeguard for the relative beginner a flat tailplane will be adequate,it is just something to keep in mind as a way of trimming out a difficult design and could prove useful to you one day so dont loose any sleep over this.
As regards the construction of the tail,as always and I know that I keep repeating this ! build it light as possible but reject any kit tails that are built up, from too many alternating grain curves that are multi cemented in a circle !! these are almost guaranteed to warp beyond anything resembling a flat tail surface,all that is needed in a wide trailing edge,a curved strip leading edge bridged with strips across,make sure that this is left on the board whilst the adhesive cures for 48 hours minimum before you un-pin it,otherwise it will start to twist.
However it is easy to build a new tail,even thin sheet ones with inserts of cross grain built in are adequate,best of all with these they can prove useful for determining th tail area we have spoken about.
I am a great believer in experimenting and these small cheap models prove good platforms to try out your design or building ideas,it is all a big learning curve,but what fun it is !