Scale Soaring UK

hi gents
still trying to electrify my 5 mtr ka8 , it weighs in at 10 kilos
i was going to put a motor in front as per ususal, but .. wen i built i put the led weights around the front so they are all built in , a nightmare to remove
has anyone got a plan of a pylon i cold mount on the top at the c of g ,it will need to be big enough to have a 14" prop on
am i being silly or would it work ?
thanks in advance
mick

Hi Mick,

I'd jump at the chance to remove lead from a model and replace it with something valuable - is it really such a big job to remove?

Another issue is that the high thrust line of a pylon-mounted power system creates a strong nose-over tendency - a real pain during the ground roll.

Sorry... not trying to be negative, but nose-mounted power systems have a lot going for them.

Rog

Mick, I must agree with Jolly Roger. The work involved getting the lead out will be small compared with all the complications of a pylon both in the building and flying. The pylon will be need to be both high (14" prop you say), and strong enough for a powerful motor required for the weight of the model.(10 Klo you say) Then you must account for a way off thrust line as Roger has said , to say nothing of the poor handling it will bring to the aircraft. 'An up n go' collapse's of coarse returning the good handling to the aircraft after the power run. No cut the nose off. Ter

Mick, if after all we advised you still want to go down the pylon route, check out the pylon that Euan has put on the classified adds yesterday. Ter.

I have done a lot of pylons for gliders in the past. A 14" prop negates any ground roll problems you may encounter, because the prop is unlikely to have sufficient ground clearance to begin with. So will you hand launch or ROG?
Hand Launch: go with a nose mounted motor, for all the reasons mentioned here.
ROG: Unless you can get the nose high enough you will be forced to use a very small prop, for a glider. Whilst this will work, it is pretty inefficient.
If you go for a pylon, ideally you need quite a lot of upthrust for the motor on condition to counteract the nose down pitching moment from the motor. The thrust line needs to go though the MAC line of the tailplane! I know, it looks ridiculous but trust me it is right. Of course you can compromise and use less upthrust and deal with it with elevator, but then you are adding trim drag. However, Take off will be dramatically easier with a lot of upthrust. The pylon ideally needs to be as aerodynamic as possible, and a pusher arrangment with a folding prop is best.
John