RE: SkyMaster MB339 Build Thread
 

Classic!

RE: SkyMaster MB339 Build Thread
 

Bringing this thread back to life....

This is where i am now....

I have the wings completed, all servos hooked up, electrical Q/D is completed and tested.

The pnuematic system in the wings is connected and tested. Doors and Gear are working perfectly and the wings are plug and play.

Iam back to the nose again. Ihave all 3 doors hinged and now I am working on installing the ram for the large nose door as well as looking to convert the rear doors to a mechanical setup.

Iwill post some pictures soon....


Whats going on with the other 339's out there?

RE: SkyMaster MB339 Build Thread
 

What a coincidence!
Did not look at this thread since the last post, but a few hours ago I picked it up again, was trying to find some info.
.
Am busy now with repairs due to my bounced landing, took two months to find time and courage to start it. I was basically looking for ideas to convert the small nose gear doors to mechanical actuation.
Getting them out by spring action is not the problem, but finding a way to close them...I ran out of ideas so am reconnecting the rams. However I had to find new attach points to the airframe for them, which I am doing right now.

Had to beef up the F2 former, as well as the nose gear supports. In hindsight, the F2 does not support the nose gear support very much, in case of backward forces of the nosegear. At least I would recommend to fill up the centre lightening hole, here the former just snapped in two. Some extra weight is no problem here, just less lead needed then!
The problem is caused by the fact that due to the long nose gear structure, the support consists of two halves which are not very strongly connected together.
By doubling former F2 and putting an extra 5mm plywood layer on top af the nosegear support, I hope to have it all beefier. (but things still break at the weakest points....)

The reason that I am doubling the nose gear supports is that they consist of two layers, glued together. But one side was badly glued, causing it to split completely.

Outside damage is limited to a small area behind the nose wheel recess, and all in the grey part, so a touch up involves only one colour.
One wing gear support was slightly cracked, which was easily repaired. The other wing...looks like more work....

Smoke pump which malfunctioned was replaced for free by Jetcat, good service! Am relocating that one as well.

Currently using only one channel for ailerons (Weatronic) but am switching to 2 channels so I can have crow airbrakes on top of the normal airbrake.

Another MB flyer from Germany reported also on the bouncing tendency. I guess I will do the next flights on grass first, I guess grass does not trigger bounces that quick as concrete...

Anyhow, it would be nicer if the nosegear would have more of a shock absorber characteristic, iso a spring like it does now.

RE: SkyMaster MB339 Build Thread
 

Here you have some footage of a skymaster MB339, shot 2weeks ago :-)

[youtube]http://www.youtube.com/watch?v=wNe3zTeaAEM[/youtube]

RE: SkyMaster MB339 Build Thread
 

Guys, if you're bouncing the Mb339, you're landing too fast.....the fact that the gear has lots of travel and "helps" it back into the air is secondary to the real issue.....slow it down more and it will stop the bouncing.....tail low is the key....I had a rule when flying mine...if I came over the approach end of the runway in a level attitude,I went around then.....forcing it on the runway will start the pogo stick syndrome...

RE: SkyMaster MB339 Build Thread
 

Hi MB Pilots,

I´m the guy with second bouncing MB. The problem was that I had to much oil in the damper.
So the landing gear was to hard. Now it works, but the plane has less space to the ground.
I also have a problem with a leaking seal inside the damper - still try to get a new one.

Second problem is with the pneumatic system. I find out that the connecters coming with the kit
somtimes leak. So I have to replace them.

Nevertheless it is by far the best flying jet I had up to now.

Greetings

Christian

RE: SkyMaster MB339 Build Thread
 

OK, made some progress yesterday. My big focus was the nose doors....

Itoo have decided to go mechanical actuation for the rear nose doors....I think Ihave a solution and once Iget it 100% I will post pictures.

RE: SkyMaster MB339 Build Thread
 

Dave, hurry up and get it done....I cant wait to fly it....oops, I mean see it in the blue and gray camo....http://www.rcuniverse.com/forum/js/f...sn/biggrin.gif
Ryan</p>

RE: SkyMaster MB339 Build Thread
 

OK, made some forward progress this weekend. Ifinally got the nose gear doors worked out. The large door is pneumatically operated and works perfectly, the smaller nose doors are set up to work mechanically. The doors are set to open via spring action and they are closed with a cable system that works off the nose strut. The strut retracts and pulls the cables and closes the doors, simple! Only took a week to figure out!!!!

Also made progress on the tail section. The stabs are rigged out and all wires are routed and laced in. Each servo lead is protected in its own fire protective sleeve in the hopes that the hot section will not melt the wires.

Finally, Istarted on laying out the air system....

Pictures tell the tale.....

RE: SkyMaster MB339 Build Thread
 

F18, what is the green insulation on your servo wires and is it mail order?  Nice install.....

RE: SkyMaster MB339 Build Thread
 

F-UAL, I m trying to get a manufacture for teh sleeving so I can share.....Igot mine from a buddy at the airport, he works in avionics...

Now, a question for you MB339 Builders...the Sub Fins, how did you attach them? Did you go with a permanate install or did you go with a method that allows them to be removed if required?

How did YOUdo it? http://www.rcuniverse.com/forum/js/f...eeth_smile.gif

RE: SkyMaster MB339 Build Thread
 

Super clean install Dave!  You've really done a great job on that thing!<div>
</div><div>Chad</div>

RE: SkyMaster MB339 Build Thread
 

F-18, my strakes were glued on when I got the plane....the tailcone will actually hit before the strakes do....mine never touched the ground.....I would say go ahead and Hysol those bad boys on....

here is a link to more heat wrap for wires....never used it, but I think I'm gonna order some....

<table cellspacing="0" cellpadding="0" border="0"> <tbody> <tr> <td valign="top"> <div>http://www.jcwhitney.com/autoparts/P...ULATING+sleeve</div> </td> </tr> </tbody></table>

RE: SkyMaster MB339 Build Thread
 

F18, I attached the strakes with silicone kit (transparent version). Good thing is that it can be removed with a sharp knife, But You have to put some masking tape along the strakes and on them selves, otherwise it will be messy.

Repairs are finished, some testing required and then we go again. Visual damage to the fuse skin at the underside will be repaired in due time, not visible from above.

I modded some structural parts:

Nose section: Put 6mm doublers on the nose gear plates, the original which consists of 2 doubled 3-4mm plates split as a result of the bounces. Badly glued I guess.
Together with a 5mm doubler on F2, they provide a much stronger base for the nose gear, plus glue joints are better now. The increased weight can be compensated by removing some lead.

Wing gear section: I found that when the gear leg is bent backwards, the gear plates do not withstand the resulting torsion. This stems from the fact that the two plates to which the gear is mounted, are insufficiently interconnected. The wing ribs to which the gear plates are glued, are cut back almost to the wing skin, in between the gear plates, thus provide no support.
Basically the support against torsion is provided only by the wing skins.
I Hysolled some 5mm plywood in the gear bay (actually to the top skin) and put small multiply blocks under both gear plates, see pics
It feels much more sturdy now, it can withstand more torsion now, before You see anything move there.

RE: SkyMaster MB339 Build Thread
 

Richard, do you have the Skymaster or the FB339?

Iam done with my wing build for the most part but will go back and make the additions you show if they are required...

Please Advise.

RE: SkyMaster MB339 Build Thread
 

F18, I agree, the thread has grown long.... but I have have referred many times to Skymaster, which indeed it comes from.

Maybe a new scan through the thread gives You ideas about changes.
Christian mentions marginal pneumatic parts, I used bar none of the supplied stuff, changed all in FESTO and the likes.
I would recommend the changes like I did to the gear mounts, both wing and nose gear supports and formers. It is a heavy bugger this one, the gear and mounts have to be able to handle a few bumps.

RE: SkyMaster MB339 Build Thread
 

Guys if you need protective sleeving for servo wire or air tube you can get it now on Als Hobbies web site, I sourced this stuff via a specialised heat resistant sleeving manufacturer, its fantastic for neat instals and protecting cable and air line runs.
Attached is a pic of the MB339 I worked on with the sleeving clearly visible - don't worry Al stocks it in black!

marcs

RE: SkyMaster MB339 Build Thread
 

Hi Richard,</p>

glad to read that your MB is ready for the next flights. </p>

That´s really funny, I did almost the same reinforcements of the wing and at the nose gear formers. I think especially in the wing they are necerssary and I did it on both sides.</p>

Two days ago I get the damaged sealing for my main gear damper  from Mr Li Kai - thanks for the good service, also to James.</p>

</p>

Greetings</p>

Christian</p>

</p>

</p>

</p>

RE: SkyMaster MB339 Build Thread
 

OK, made yet more progress, I can only wish I was as fast as some of you guys...

Anyways....I got the sub-fins installed but in such a way that would allow them to be removed if needed. I also got the bell-mouth permanently attached to the pipe with stainless hardware. Finally Imade all new equipment trays as the stock ones had holes cutouts that did not fit my requirments...

I do have one question for the group, if you look at the pictures posted of the pipe bell mouth right at the turbine exhaust you will see the green sleeving for the servo wires going back to the tail section....my question is do you think that these will be OK in regards to heat?

RE: SkyMaster MB339 Build Thread
 

F18,
In aviation there is a saying: If in doubt.......
The wiring will get its share of radiation heat from both the exhaust cone and because of the opening between the engine and pipe.
I would suggest to place a plate of plywood in front of the wiring and have that covered one the engine side with heat resistant material or paint. Put the plate on a toolclip(s) for easy removal.

Christian, good You have done the same, so You also think there is a construction mistake in the current design. The wing gears should be in a sturdy U-type of cross sectioned mounting, so as to divide stress to a large area and not to a relative small area causing the wing sheeting to warp.
I would strongly recommend SM to redesign the setup. It will add some weight to the all-up weight, but as said, the nose can handle some extra.

For current owners: test the sturdyness of You gear by pulling the wing gear legs backward. If You see torsion movements in that area, beef it up.

RE: SkyMaster MB339 Build Thread
 

Hello MB339 Fans!

OK, more (slight) progress is made...

Firstly, Imade a reflective heat barrier to protect the servo wires. See before and after pictures.

Ispent most of the day today installing the canopy glass....based on the way it turned out, new glass will be needed. I did not even notice the ripples as I was cutting and fitting it but once I got to the "its time to glue it" point but then it is unmistakeable....

More work on airlines and servo trays...Ithink I am the slowest builder on the planet!!!!

RE: SkyMaster MB339 Build Thread
 

More progress last night....

RE: SkyMaster MB339 Build Thread
 

Good news!
Re-maidened my MB again, after repairs and many other mods.
Pity approaching rain limited it to one flight and right at this moment I'm drying myself, MB and all other stuff.....

Plane flew again wonderful, my son Thomas flew 4 point rolls like on rails.
CG was balanced (with part fuel) to centre of main spar.
Ailerons UP with flaps down, combined with speedbrake give sufficient decelleration on final. A bit of down elevator blended in to compensate for pitch UP caused by speedbrake and ailerons UP proved to be right on the spot.(the speedbrake gives a peculiar whistle!)
Smoke trail great improvement (new JC pump, thicker stainless steel pipe in exhaust), but grey sky backdrop somewhat minimised the effect.
JetCat now to single channel, needed the extra channel for the ailerons (mixing with flaps).

New mods will gonna be:
possibility to change to other model setting, where ailerons do NOT go UP when selecting flaps: this is for T/O's off grass where flaps only is needed, or even DOWN ailerons are blended in.
CG more backwards by removing nose weight.

Here we go, another Cabernet Sauvignon-Shirah!

RE: SkyMaster MB339 Build Thread
 

More progress......

<span class="Apple-style-span" style="font-size: 13px; ">The main board is done with the exception of the on/off switch and the voltage monitor. The main and saddle tanks are complete. On the main tank I made the brass 90 you see hysol&rsquo;d in place&hellip;.do you think I am good to go there?</span><p class="MsoNormal"><font face="Arial" size="2"><span style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p></o:p></span></font></p><p class="MsoNormal"><font face="Arial" size="2"><span style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">All I have left is to install air tanks. Get and install QD&rsquo;s for the airlines to the main panel so it can be removed at will. Install the fuel pump, valves and lines. Install the speed brake valve and servo. Install batteries. Build a ECU battery cutoff/charge switch assembly. Install canopy glass. And a thousand things I have not thought of yet. </span></font><font face="Wingdings" size="2"><span style="FONT-SIZE: 10pt; FONT-FAMILY: Wingdings">J</span></font><font face="Arial" size="2"><span style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p></o:p></span></font></p><p class="MsoNormal"><font face="Arial" size="2"><span style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p></o:p></span></font></p><p class="MsoNormal"><font face="Arial" size="2"><span style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Question: Can I use a 3 cell A123 on the ECU (Rhino) and do I have to make changes to it for its use?
<o:p></o:p></span></font></p>

RE: SkyMaster MB339 Build Thread
 

F18,
Did You test fit the saddle tanks after You installed the wing air and electrical connections? It gets tight there....