Skymaster L39 Elevator servo
 

What servos are you guys using?? Manual calls for a DS9301 but I cant find any specs on horizons site for that servo. Will 3421s work??

Mike

RE: Skymaster L39 Elevator servo
 

The reason you will never find it on horizon's site is because it is a Futaba servo. actually it is a discontinued servo which i believe was 100oz of torque.




Alan

RE: Skymaster L39 Elevator servo
 

I have just purchased this Jet.. I am considering this servo..

http://www.horizonhobby.com/Products...dID=JRPS3421SA

Cheers

RE: Skymaster L39 Elevator servo
 

Those are the servos I was looking at too...but I wasnt sure.

RE: Skymaster L39 Elevator servo
 

Hi

Im using hitec 5955 servos for the elevator and the flaps...they are 300 oz +....It also eliminates the use of y's and or match boxes!!

Tommy

RE: Skymaster L39 Elevator servo
 

Anyone else have an L39?? Im just not absolutely convinced that the 3421 is large enough. It calls for a 4KG servo...not sure exactly what the conversion is but the 3421 does 75oz.

RE: Skymaster L39 Elevator servo
 

Well, I found out that an 8611 will not fit in there...but an 8411 seems to go in alright although its snug.

RE: Skymaster L39 Elevator servo
 

To easily convert metric torque to standard....go to http://nmbtc.com/Calculators/converter.swf

Click Torque tab and click on Kg/cm in choose units row, enter Kg in "convert from" window. Click "calculate". Read oz/in.

Very accurate. I get 55.5 oz. required....not a lot of torque but according to the manufacturer, the 75 oz. of your 3421 should be adequate. I think they're using small servos to minimize tail weight. You decide whether overkill on the stab servos warrants lead in the nose,

W.

FWIW Alan, the JR DS9301 is the Japanese version of the western JR DS3421. They are identical servos.

RE: Skymaster L39 Elevator servo
 

Hello,
I have a SM L 39 with JR DS 9401 (or JR 9411 for the US) for the elevators which fits perfectly and has much more torque than JR 3421.Besides, I think JR 9301(plastic gear version of 9411) is bigger than JR 3421.

Best regards and merry Xmas.

RE: Skymaster L39 Elevator servo
 

Thanks for that info. I think I will go with the 9411.. Here is a pic of my new airframe.. It's big in person!

RE: Skymaster L39 Elevator servo
 

Thanks Woody!

I was coming up with a different number, I was doing KG/IN vice KG/CM on another converter...makes a huge difference. I happen to have one 3421 and one 9411. The 3421 fits MUCH better than the 9411 but the 9411 still fits fine and has so much more torque. Still undecided....

RE: Skymaster L39 Elevator servo
 

I decided to go with the 9411s, ordered one more about an hour ago. Did you guys make a servo tray and glue them in or did you mount them directly to the skin. I remember seeing a thread that mentioned to make a tray for the ailerons/flaps but not sure about the elevators.

RE: Skymaster L39 Elevator servo
 

Well, I went with the 9411 and installed the first one tonight. I did not like dropping the servo in through the end. Makes it difficult to align perpendicular to the elevator hinge line particularly because of the taper of the stab. Also its hard once you get it aligned to be sure it is glued in properly. So...I cut an access hatch. Its not square due to the channel the stab sits in is tapered along with the stab. Side to the right (inboard) is cut perpendicular to the hinge line so the servo arm will parallel that line and the outboard line is cut just outside of the rivet line. Glued the blocks in place, hatch fits great. Dark stuff around the edge is ink from the marker I used to mark the cutout lines...tried to clean them off but I couldnt get all the ink off. Oh well, the plane has a date with the paint booth.

Mike

RE: Skymaster L39 Elevator servo
 

Hi Mike,

Just a personal thought and advice.

I think you have weakened the stab quite a bit by cutting out the access hatch. The method used by others of installing the servos from the root access does work nicely.
Anyway, I would strongly suggest you building a balsa or ply box around the cutout to reinforce the opening.

Just my 0.02C

Thanks - Adil

RE: Skymaster L39 Elevator servo
 

Adil,

Thanks for your suggestions. Two of the sides are already lined with balsa. Behind that balsa...it is LOADED with what looks like aeropoxy to hold in tubes for the stab spars. Ill take your advice and complete the other two sides.

Mike

RE: Skymaster L39 Elevator servo
 

Hi Mike

I would definitely go with the 8411/9411. I had 5.6 kg(77 oz) in mine and they were a bit weak especially considering the volt drop in the long leads. I have just changed mine to 8411's. A little work is required to get them in. A real snug fit.

I did build trays for the aileron servos which I then glued in place. You will not get to all the servo screws anyway.

I have had one flight on mine and messed up the landing with an unsuspected wing drop just on landing.

Getting the wheels to fit into the wheel well is a real pain in the butt! Hopefully your kit is a new one where they have changed the flex plates. Do not pump the tires too much!!!!!!!!!!!!!

Flies beautifully.

Will be taking it out again this weekend.

RE: Skymaster L39 Elevator servo
 

Well I finally got around to working on the rudder tonight. This instruction manual is a little lacking, which I expected. It says that the rudder servo mounts are already installed...mine dont have any installed at all. Further, it says the pushrod is to be 90 degrees to the hinge line, which makes sense, but the photo in the manual CLEARLY is not even near 90 degrees. Anyone else missing the rudder servo mounts or do you have a pic of yours??

Mike

RE: Skymaster L39 Elevator servo
 

Mine also did not have the rudder mounts.