Super Star - Graupner vs Seagull

[David Hayward]

I shall be grateful if anyone could advise me about the following? 

I have acquired a Graupner ARTF Super Star (1760 mm, 691/4" wingspan) complete with 26cc petrol engine.  I am now setting about putting it together .  The instructions state that it has been designed for use with standard servos and, in line with this,  the model review in the February 2006 edition of RCM&E refers to use of  'cheap Futaba 3004' servos - no need for £89 digital jobs' .   S3004s are a ball-raced version of a standard S3003 but with the same standard a torque rating of 3.2 kg/cm (4.8V) and speed of 0.23 sec/60deg.  The model was put through numerous aerobatics during the review includiong flat inverted spins and benders and is said to have performed very well with this set up.

I now find that Seagull has brought out its own version of the Super Star which seems virtually idential to the Graupner version (same wingspan) and is designed for similar engine sizes (1.60 2-stroke, 1.80 4-stroke). This model was reviewed in the recent RCM&E August 2008 magazine using Hitec 645MG high torque servos which have a torque rating of 7.7 kg/cm and associated speed of 0.24 sec/60deg and hence a torque rating some 2.4x higher than Futaba S3304s.  The review article for the Seagull Super Star states that one would be doing the model an injustice if fitting standard servos . Although the author of the article does qualify this by indicating that, of course, cost may be a factor, to my mind at least, this seems to throw up a difference in opinion relating to two pretty much identical models!?

So, as someone who is only just venturing into larger models with bigger engines and who has quite happily used standard servos on all  models to date, should I keep my S3004s for a future, less potential racey model and purchase higher torque ones for my Graupner Super Star?........or, should I just stick with standard (torque) servos as Graupner indicate in their instructions?

Bearing in mind that I don't wish to spend more money than necessary and end up with an unnecessarily over-designed model and yet wish, in due course, to have the confidence that I can throw my Super Star about the sky a bit without serious risk of mishaps, which option should I adopt?  

All comments would be much appreciated.

David 

  

[simon barr]

Hello David,

I don't know this model, but one option would be to install the JR 591's. These are 5 kg servos, and although a budget servo (around £10 each), I have used them successfully in a couple of larger models. I do think that 5 kg is the minimum you should be considering for a model of this size with a 26 cc motor up front....the more you pay, the better the servo.

Also remember that the further out from the centre of the servo you connect the push rods, the torque will be reduced.

[David Hayward]

Thanks Simon - comments noted.