RE: SkyMaster MB339 Build Thread
 

Found it!
Comparatively easy I located the air leak (could hear it, it leaked massively), it proved to be the SMC air press indicator. The airline receptacle is bolted into the unit and prevented for leakage by a paper(?) washer. Under water You can see why my MB lost xxsure in a few minutes!
Replaced now by a (SM provided) Pisco Unit.

The light problems (Flugmodellbau) were as a result of me switching the receiver on with the light switch in ON. FIRST the receiver should be ON before the light system is operated.

OK, all clear for the next flights now!

RE: SkyMaster MB339 Build Thread
 

Caution!!!
I suddenly remembered from the maiden flights that during testing the MB on the ground, the rudder somewhat seemed to chafe when holding the tail under power. After the succesful flights I forgot about it.

Today I inspected again and this is what happens: simulating airload on the vertical tail during flight I pressed the tail a little backward and again the rudder almost jammed! Obviously I had made the space between the lower part of the rudder and fuse a little TOO tight. With a sanding block I removed about 1mm of the lower part of the rudder.
I would advise to check your planes and correct if necessary. If You are still completing the MB, be sure You have at least 1,5mm of space between rudder and fuse, when installing the rudder.
First pic is previous space, last is widened.

RE: SkyMaster MB339 Build Thread
 

My MB-339 was ready yesterday, but when we were ready for testing, we discovered that the Powerbox Royal wasn't working properly. Because of that, it was impossible to fly today.

Fortunately enough, I did have another Royal that I was going to use in another plane so today it was installed. Tomorrow we should be able to program it and after that, the only thing that is left is to balance the plane. After that.......... maiden flight. We'll see how it goes.

One thing I did notice, is that the rudder doesn't move much to the sides. With the current deflection, I don't think that the airplane will be able to hold a knife edge. I don't think it's a problem of lack of space between the rudder and fuse. I think we'll have t sand the sides of the tail so that the rudder could have more deflection.

RE: SkyMaster MB339 Build Thread
 

One thing I haven't been able to figure, is the location of one of the lights supplied in the light kit.

I have the installed on top of the rudder (red), in the tail (white), on the wings (red and green) and in the aft landing gear (white). I was wondering if the extra one goes somewhere in the belly of the plane....... Anybody knows ?

OK...... i did figure it out. It goes in the bottom. http://cdn-www.airliners.net/aviatio.../3/1427349.jpg

RE: SkyMaster MB339 Build Thread
 

Gonzalo,
Maybe You bought a "deluxe" version of the MB, I had to glue in the rudder myself and took care I had enough of movement. But this is a scale jet, not a 3D flyer, a knife edge would be nice for me but not necessary. High speed and large rudder deflections don't mix....
Anyway a great feat that You (and Flavio) have completed the MB in record time!
What do You mean by a white light on the aft gear?
Indeed the Beacon ligt (normally rotating but flashing is OK) should be on top of te vertical tail.
Navigation lights (3) are steady, the white in the aft tail, red on left, green on right. If You always mix up colours, starboard and port, left and right remember the word GRAS: Green Right at Starboard.
Gras(s) is green, easy to remember!

The large beam light should go on the nose gear.

The white strobe(flashing) lights are relative new in aviation, the first smaller airplanes were fitted with them maybe 35 years ago, it might be that the original MB hadn't even one and was modified later with one (indeed) in the belly, which is not a favourable place for them. Newer airplanes tipically have them on the wingtips, which provide a better view for airplanes approaching from the side.
I had to make my own lens cover, removed the red/brownish scale part of the belly and molded my own lens cover in the form of a long slender "canoe".
Indeed, airliners.net also provided me with lots of info.

What was wrong with the powerbox? I am using Emcotec throughout all of my models, super quality and service.

RE: SkyMaster MB339 Build Thread
 

Richard:

I bought the "PRO" version of the MB-339 which came with all the landing gear installed (they did a great job in the factory.....).

The large beacon light is already installed in the nose gear and I think I posted a picture earlier in this thread. The red beacon light is installed on the top of the vertical tail, the white one in the aft tail and the other two (red and green) in the wings.

Thanks for the tip of were to install the white light in the bottom of the plane.

I don't know what is wrong with the Powerbox. When we connected the radio, the Powerbox started acting up and the screen wasn't showing the correct voltage of the batteries. We'll see what the manufacturer has to say.....

RE: SkyMaster MB339 Build Thread
 

Gonzalo,
How much lead in the nose You've added?

RE: SkyMaster MB339 Build Thread
 

Richard:

We didn't balance the plane today. We were going to do it, but we found out that we had an air leak and we spend long time looking for it. The plane will be balanced during the week and as soon as I have the info, I will post it here.

We did run the turbine (Rhino) in order to check all the other systems and we found no problems. The turbine started immediately the first time and we taxied the plane to try the brakes. We also did a range check with good results.

I did noticed that the ventral fins are seating very near the floor and I don't know if this is because of the design or because the landing gears need some checking in order to make sure they have the correct height. Flavio will do that next week. He will also install the missing light.

RE: SkyMaster MB339 Build Thread
 

Richard:

They just told me that my MB-339 will require 950 grams of lead............. ouchh [sm=what_smile.gif]

RE: SkyMaster MB339 Build Thread
 

Yes Gonzalo, we spend quite some time with Flavio balancing for correct CG and that is what we will add to the nose. But do not worry, with all this new light items like Li-Ion batteries, electronics, valves, etc. we need to add more lead now than in the old NiCd times.
The powerbox was not working becasue of a problem with the airpower EV5SU valve. It seems that if you connect the retract lead to the powerbox and the brake lead to the receiver the powerbox does not like this. Connecting both leads to the reciever solve this problem.
By the way this new Airpower valve is awesome. Retracts work great )except ofr the leak) the secuencing is very easy to setup. Also the brake is excelent, real proportional breaking, very nice unit from airpower.
It was too bad we weren't able to do the maiden today, but after we find the leak up we go my friend...:D

Michel

RE: SkyMaster MB339 Build Thread
 

Richard:

What's the distance you have between the ventral fins and the ground ? Have you measured it ?

RE: SkyMaster MB339 Build Thread
 

That's not uncommon at all. I think the 339 I built required pretty close to that exact same amount. When you get that weight in the nose it should compress the strut a little more and that will raise the tail and get the ventrals a little higher. Don't worry about weight, the plane will fly awesome!![sm=thumbup.gif]

RE: SkyMaster MB339 Build Thread
 

Gonzalo,
Sorry, did not measure. The plane is on the attic now, would take long time to get it all setup and measure.
But there is IN BETWEEN the ventral fins a little stub, look closely at the airliners.net pics.
This is a tail bumper, tailstrike protector, dunno what the correct name would be.
I have set it up that this will contact the ground first, so the fins will not de damaged. This stub is included in the kit, but it is hollow, I filled it completely with epoxy to beef it up. I might change it for a plywood version, much lighter and easy to replace if damaged.
The distance You get will be very much dependent on nose gear pressure (should be low) and main gear pressure, which should be high. My MB stood a few weeks on its mains, I have the impression the tail got lower, maybe the air pressure decreases faster when the oleos are compressed, I have to recharge next time before I will fly. Due to circumstances my next flight possibilities will not be sooner as end of febr.

As indicated earlier, I have even more lead in the nose, close to 1.5 kgs, but this was no problem during the 2 flights. But of course it would be nicer if the tail would be lighter, let's say they build the tail 1 kg lighter (lighter fins, longer tailpipe so the engine can move forward) then some 1 kg lead could go. A 2 kg lighter plane would make quite a difference.
Since the last flights I removed 80 gram of nose weight.
I based this on the trim setting which required nose up trim during the whole flight, plus the fact that my son held 4 seconds of full elevator during the landing flare, and the plane never reached an excessive attitude.
Also the MB flew very stable, which indicates a bit less lead would do no harm.

RE: SkyMaster MB339 Build Thread
 

Guys,

I am at my Witt's end....for two weeks I have been trying to hinge the large nose door. I cant figure out how exactly to do it. I am at a total loss. The double compound curve of the door is kicking my butt.

I am begging, could one of you guys that have the door hinged post some detail pictures, please! My project is at a stand still until I get this completed.

Thank you in advance!


Ps...any measurements you could provide would be helpful too!

RE: SkyMaster MB339 Build Thread
 

F18.
Why don't U use the way I did it (posting nr 39) with those flat hinges? Works terrific.
Look at many tea and coffee pots that have all kind of complex lids. They all have external hingeing.
The negative visible impact of the hinges protruding is a small price for a well functioning door. You don't see it when looking at the model from above.

RE: SkyMaster MB339 Build Thread
 

F18:

I will try to take some pictures tonight.

RE: SkyMaster MB339 Build Thread
 

Hi David,
your MB339 is Skymaster or FeiBao?
I have a SimJet AES 3000 turbine (30 Lb. of thrust) and I would like to build a MB339 FeiBao but I have always feared that the turbine was small for such model.
Could you post some video of your model?
Thanks in advance.
Best regards

RE: SkyMaster MB339 Build Thread
 

OK guys, I have the door hinged. I went to speed world this last weekend and SkyMaster had a demo 339 there. I checked on how they did it and it is too simple. I just mounted the hinges on the fuze and glued them to the door...I had my doubts but it worked, perfect.

Now I am on to the cockpit install. The front glare shield / instrument panel is crap and I am building my own...I am going to see of Skymaster will make it right with a credit or something as what they shipped was not usable IMO.

Thanks for all the help thus far!

RE: SkyMaster MB339 Build Thread
 

My MB-339 finally flew yesterday....... [sm=shades_smile.gif]

After several last minute fixes (done with the help of Lillo - Acrored in this forum), Michel from www.jetsrc.com took the plane for its first flight and it was great. The takeoff was very smooth and it was incredible to see how the airplane needed little runway to be in the air. A couple of clicks for trimming, and the MB-339 was flying straight.

Landing was a little bit of a challenge at first, since you have to cut power way in advance. If you don't do it, the plane will keep its speed and it will float over the runway. We didn't have time to try the speed brake and I think we will do it on Saturday.

The only bad thing was that we didn't have enough light to keep flying the plane so I will have to wait until Saturday to try it.

It is a beautiful flying airplane and flies great at low speeds.

RE: SkyMaster MB339 Build Thread
 

Congrats Gonzalo!

My #1 concern on flying the 339 is running out of runway on landing, not that she lands fast but that she floats and I have a tendency to come across the fence hot!

OK...

Build update:

I got the nose door hinged, FINALLY! I went to speed world and eyeballed the SM demo 339 and kinda followed their lead.

I am working on the cockpit and I have the rear pit fitted to the canopy frame. The front C/P is in limbo, do I attach it to the canopy frame or have it stay as part of the main body....

Also, the front glare shield and panel were not to my liking so I am remaking them...see some pictures...

Gonzalo, could you snap me some pictures of how you did your cockpits? In the pictures it looks like they stay with the canopy.....

RE: SkyMaster MB339 Build Thread
 

The cockpit went through some serious modification. I will go to the club on Saturday and I will take some detailed pictures. You are right..... the cockpits were installed inside the canopy. In that way they are easier to put back.

Are you going to have the speed brake operating ? Maybe you will need it if you tend to have some fast approaches. I was beside Michel when he was bringing the plane to land and he was barely touching the throttle. It look like an IMAC plane when it was landing....

RE: SkyMaster MB339 Build Thread
 

This jet is awesome, it just glides in when landing. It is so easy to land, and it fly's like a dream, very scale and stable. Congrats Gonzalño on your jet, I am sure you will have many great flights.
I hope to get a video this weekend...:D

Michel

RE: SkyMaster MB339 Build Thread
 

Thanks Gonzalo!

I am going to use the Speed Brake....

RE: SkyMaster MB339 Build Thread
 

With the MB-339 that I flew, I mixed crow into the ailerons and mixed with full flap, this along with utilizing the speed brake made this bird a breeze to slow down. I know Jason is not using crow on the MB he was flying at Speedworld so it's not a mandatory need, but it does help a lot. Once you fly it a few times and feel what you need to do to slow it down, you can land that thing on a postage stamp if needed...it really does land very slow.

RE: SkyMaster MB339 Build Thread
 

Dave beat me to it....CROW is the answer....you guys think slowing down at sea level is tough....try it on a hot summer day in Denver when the density altitude is 9200' on a 600' runway....I mixed about 5/8 - 3/4" up aileron with full flaps.....I didnt have a speed brake. MUCH better at slowing down and aileron effectiveness is still very good woth the crow.....crow also effectively adds washout at the tips, further helping the stall......try it, you'll love it.....