|Feb 07, 2012, 12:05 PM|
The wing is similar in construction to the T-45 / Hawk : basic balsa built-up D-tube design with balsa ribs and balsa spar. Occasionally there's some light plywood here and there.
That implies that the wing might need to be reinforced (or at least thoroughly checked) in the landing gear mount region.
The overall wing design would suggest lightweight setups less or equal to 8S in edf, and very marginal (and possibly dangerous) for a small turbine.
The linkage hardware is, as for the T-45, more like park-flier grade, but that can be fixed / improved.
Interior wing structure :
|Feb 09, 2012, 11:26 AM|
The L-39 seems to be a popular model. Here's a short comparison with other EDF / turbine models:
L-39 JTM ws=108cm weight rtf 10lbs $680
L-39 HET ws=112cm weight rtf 9lbs $350
L-39 CMP ws = 120cm weight rtf = 7-8lbs price $240
L-39 Savex ws = 122cm weight rtf = 8lbs price $755
L-39 Schreiner ws=127cm weight rtf=8lbs price $704
L-39 Airworld ws=138cm weight rtf=14lbs price $1550
L-39 Skymaster ws=175cm
L-39 JetLegend ws=188cm
L-39 Airworld ws=190cm
L-39 Flyeaglejet ws=205cm wt 37lbs
The above figures are approximate, based on what I could find on the net (esp. the weights rtf depend on setups).
I have seen the Savex, HET and JTM in person.
The Savex is superb and light, fully molded.
The HET seems good value but the oracovered wings looked really cheap. Overall I was not impressed, and HET quality is what it is.
The JTM (molded) wing was very well made but the model seemed a bit heavy. It flew well in spite of the weight. There's a video on youtube showing one having a wing delaminate in flight.
The CMP one should probably be compared to the Het one, and I think the CMP one looks quite a bit better, at least to me.
WeMoTec Minifan-sized (69mm) L-39 models have also been popular for a while (eg. K&A) and here's one (83cm ws) :
and the Sapac one (89cm ws) :
|Feb 09, 2012, 11:52 AM|
I computed the CG and ended up ahead of the CG mentioned in the instruction.
CMP's L-39 CG (90-95mm) is very close to the mains ! The CMP Hawk's instruction CG was completely off ...
My CG for the first flights will be conservatively at ca. 72mm
|Feb 09, 2012, 11:54 PM|
these are the Parkzone $4 T-28 pilots from my local hobbyshop. I repainted them.
I used them in the T-45 as well. You can always find better pilots that are heavier and cost more.
A Bientot, Herb
|Feb 11, 2012, 07:16 AM|
Joined Aug 2011
Thancks a lot HERB
this is the éléctric retract with trunnion and all the parts for repair !!! and the price OUA !!!
|Feb 11, 2012, 12:26 PM|
Yes , Nice I see he sells all sorts of spare parts.
Or here :
It is a very good thing to have replacements easiliy (and cheaply) available. I think most likely the metal trunnion will not break, the mechanism or some of the plastic will.
|Feb 21, 2012, 11:27 AM|
For installing the navigation lights I drilled a few holes in the wingtip tanks ... the gelcoat cracks and chips easily so one has to be careful.
I used a special type of clear epoxy I already had lying around for gluing in the led's ... I don't want them to get loose or fall off later.
|Feb 21, 2012, 11:29 AM|
I also installed the two aileron low profile lightweight digital servos (Blue Bird BMS 555 DMG).
The supplied aileron linkages & horns are the same parkflyer-grade ones used in the CMP T-45 / Hawk, which I won't use.
I'll be working on the wing for a while ...
|Feb 21, 2012, 02:20 PM|
The elevator and rudder servos are installed directly in the stabilizers, which is good
Makes for some very short and tight linkages.
A quality 9g servo will be fine for the elevators, more or less the same torque requirements apply here as for the CMP Hawk / T-45 :
For the rudder I might need something a bit stronger. Will have to see what I have lying around that might fit in the fin opening.
The servos shown below are actually quite reliable, I have a few and all have performed rather well.
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