SkyMaster MB339 Build Thread
#53
RE: SkyMaster MB339 Build Thread
F18, a friend of mine arranged them for me(I'm from Europe), I guess in the States they have them too, if not I'll send You a set, just PM me.
I went on with the systems , focusing on the pneumatics. Gear was mounted, no big deal although some work on the bearers had to be done (not enough clearance). The gear operates now as advertised, I have to figure out however to limit the downspeed (it slams down). Already installed a FESTO flow limiter in the wasted air line, but basically You can optimise the speed in only ONE direction...
I included some pics of the engine bay taken from behind. The QD conn's reach some 2cm into the fuse, and the tubing has to bend downward quite steeply, tight fit, but I got it working. Festo line will knick here, I use UP line for these purposes.
Test fitted the tanks, intake air duct and engine bottom duct, all seem to fit OK.
Oh, I elected the engine bay as service bay, I am working on getting it accessible for all systems, so I made small formers to take up the air refill conn's plus press indicators and the other side houses the Weatronic socket. I will make side panels for bat recharging etc. Did not want to have the cockpit area for all of this, too complex to open it every time.
Still lotsa work to be done....
I went on with the systems , focusing on the pneumatics. Gear was mounted, no big deal although some work on the bearers had to be done (not enough clearance). The gear operates now as advertised, I have to figure out however to limit the downspeed (it slams down). Already installed a FESTO flow limiter in the wasted air line, but basically You can optimise the speed in only ONE direction...
I included some pics of the engine bay taken from behind. The QD conn's reach some 2cm into the fuse, and the tubing has to bend downward quite steeply, tight fit, but I got it working. Festo line will knick here, I use UP line for these purposes.
Test fitted the tanks, intake air duct and engine bottom duct, all seem to fit OK.
Oh, I elected the engine bay as service bay, I am working on getting it accessible for all systems, so I made small formers to take up the air refill conn's plus press indicators and the other side houses the Weatronic socket. I will make side panels for bat recharging etc. Did not want to have the cockpit area for all of this, too complex to open it every time.
Still lotsa work to be done....
#54
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RE: SkyMaster MB339 Build Thread
Anton, do you have some better pictures of the spring loaded nose gear doors and how you setup the mechanism for closing them when the strut retracts???
#55
RE: SkyMaster MB339 Build Thread
Ian,
There are several ways to operate the gear/door mechanism, that determines also the way the small doors open.
Each system has its pre- and cons. I chose a system based on 2 X (jettronics) electric valves, one for the doors, one for the gear.
For the 2 small nose doors I used a BVM mechanical pneumatic switch. That is, the nose strut operates a switch that can open or close a pneumatic valve.
Setup is that both small doors get OPEN pressure from the GEAR system when selected gear DOWN. They open then simultaneously with the (nose) gear.
Same for doors CLOSE, it will get get pressure from the gear UP line, however, the pressure cannot reach the doors yet, as it is blocked by the switch.
As soon as the nose strut is almost retracted, it contacts the switch and lets pressure go to the doors.
Sounds simple, but got me a while off the street to figure it all out!'
Btw my friend Leo who builds another MB went up the route with mechanical valves, he uses the UP4/UP2 combo.
Together with Leo we drew the setup in a worddoc, here is a scan, I don't know if it will readable, I could not upload a worddoc. If needed I can send it by email.
There are several ways to operate the gear/door mechanism, that determines also the way the small doors open.
Each system has its pre- and cons. I chose a system based on 2 X (jettronics) electric valves, one for the doors, one for the gear.
For the 2 small nose doors I used a BVM mechanical pneumatic switch. That is, the nose strut operates a switch that can open or close a pneumatic valve.
Setup is that both small doors get OPEN pressure from the GEAR system when selected gear DOWN. They open then simultaneously with the (nose) gear.
Same for doors CLOSE, it will get get pressure from the gear UP line, however, the pressure cannot reach the doors yet, as it is blocked by the switch.
As soon as the nose strut is almost retracted, it contacts the switch and lets pressure go to the doors.
Sounds simple, but got me a while off the street to figure it all out!'
Btw my friend Leo who builds another MB went up the route with mechanical valves, he uses the UP4/UP2 combo.
Together with Leo we drew the setup in a worddoc, here is a scan, I don't know if it will readable, I could not upload a worddoc. If needed I can send it by email.
#56
RE: SkyMaster MB339 Build Thread
I made a few pics of the nosegear actuated switch, one is with the nosegear down, one half way and one fully retracted, thereby compressing the lever. I used the backside of the steering servo with a small block to actuate it. For the switch itself I made a bracket that supports it.
Also hooked up another file of the scan sideways, hopefully it will be better.
Also hooked up another file of the scan sideways, hopefully it will be better.
#57
RE: SkyMaster MB339 Build Thread
Just started working on the fuel system.
I wonder how others do the clunk lenght inside the saddle tank. If I let it go all the way to the farthest corner, it will easily bend back so it reaches the front side, and it might get stuck there...
I use Tygon for the inside tubing and a felt clunk.
During tryfit I found out the intake duct is about one cm misplaced, off centre, that is. Therefore the right saddle tank could only be fitted with some force, resulting in a good visible bulge on the side of the fuse. Therefore I removed part of the intake duct to create some more space, will restore it with some glasscloth as soon as the tank mountings dried.
I wonder how others do the clunk lenght inside the saddle tank. If I let it go all the way to the farthest corner, it will easily bend back so it reaches the front side, and it might get stuck there...
I use Tygon for the inside tubing and a felt clunk.
During tryfit I found out the intake duct is about one cm misplaced, off centre, that is. Therefore the right saddle tank could only be fitted with some force, resulting in a good visible bulge on the side of the fuse. Therefore I removed part of the intake duct to create some more space, will restore it with some glasscloth as soon as the tank mountings dried.
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RE: SkyMaster MB339 Build Thread
Rich, I was going to do it that way but I am going for a more simplistic route. I know I could use a button valve and cylinders, which they actually gave me, but the cylinders dont have the proper stroke and geometry. I could get new cylinders and just keep going but I am going for something simple and easy to maintain. Anton had some pictures earlier in this thread of a mechanically operated device to move the doors but I cannot figure out exactly how he did it.
AHhhh, I see how he did it now, he did use cylinders on the doors, he just didnt use a button valve, he used a typical retract valve and then actuated it with the strut, hmmmm
AHhhh, I see how he did it now, he did use cylinders on the doors, he just didnt use a button valve, he used a typical retract valve and then actuated it with the strut, hmmmm
#59
RE: SkyMaster MB339 Build Thread
Ian,
Now that I figured out which air source to use for the OPEN and CLOSE position of the small doors, setting up the system as I did does not involve a lot of work, just making a bracket for the air switch is most of the work and it works flawlessly. Btw, the air switch is even not very expensive: BVM #5753 $27.50
When installing it, just be sure NOT to contact the backside of the servo yet, make the final adjustment by means of the small wooden block which is glued to the servo.
Now that I figured out which air source to use for the OPEN and CLOSE position of the small doors, setting up the system as I did does not involve a lot of work, just making a bracket for the air switch is most of the work and it works flawlessly. Btw, the air switch is even not very expensive: BVM #5753 $27.50
When installing it, just be sure NOT to contact the backside of the servo yet, make the final adjustment by means of the small wooden block which is glued to the servo.
#60
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RE: SkyMaster MB339 Build Thread
Rich, which size and stroke cylinder did you use for the small doors? The ones that came with the kit dont seem to be fitting anyhwere close to what I need. I figure I need a 7/8th inch stroke cylinder.
#61
RE: SkyMaster MB339 Build Thread
Ian (still awake ? )
Yes I forgot to mention. I have installed the Ultra Precision UP 19008 cylinders instead of the original ones. They have a stroke of 19mm.
As usual the normal fiddling to do for finding a place to attach them. I chose the hard way and put them on backside of the bulkhead, so inside the compartment where the nosegear is attached.
( In my mind modellers will also be good gynaecologists.. )
Yes I forgot to mention. I have installed the Ultra Precision UP 19008 cylinders instead of the original ones. They have a stroke of 19mm.
As usual the normal fiddling to do for finding a place to attach them. I chose the hard way and put them on backside of the bulkhead, so inside the compartment where the nosegear is attached.
( In my mind modellers will also be good gynaecologists.. )
#63
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RE: SkyMaster MB339 Build Thread
ORIGINAL: richbran
Just started working on the fuel system.
I wonder how others do the clunk lenght inside the saddle tank. If I let it go all the way to the farthest corner, it will easily bend back so it reaches the front side, and it might get stuck there...
I use Tygon for the inside tubing and a felt clunk.
Just started working on the fuel system.
I wonder how others do the clunk lenght inside the saddle tank. If I let it go all the way to the farthest corner, it will easily bend back so it reaches the front side, and it might get stuck there...
I use Tygon for the inside tubing and a felt clunk.
#64
RE: SkyMaster MB339 Build Thread
Edgar, tks! Good tip, I will try it.
Here my last updates, tanks are fitted with a bracket as earlier in this thread. Had to ream out the holes where the tank fittings stick through. Both to the inboard and top side.
Top tank fitting was too tight, had to file back the flanges of the fuse and engine bay cover.
Plus pic of the bottom of engine bay where pneumatic tubes run and electrics from the wing, YES, I like VELCRO tape!
Note the high tech balsa blocks , they serve as bottom rests for the tanks.
When installing them finally I will put a dab of silicon kit on those, plus the side that almost contacts the fuse sides.
Here my last updates, tanks are fitted with a bracket as earlier in this thread. Had to ream out the holes where the tank fittings stick through. Both to the inboard and top side.
Top tank fitting was too tight, had to file back the flanges of the fuse and engine bay cover.
Plus pic of the bottom of engine bay where pneumatic tubes run and electrics from the wing, YES, I like VELCRO tape!
Note the high tech balsa blocks , they serve as bottom rests for the tanks.
When installing them finally I will put a dab of silicon kit on those, plus the side that almost contacts the fuse sides.
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RE: SkyMaster MB339 Build Thread
ORIGINAL: marc s
Guys not that it may be possible to use but this was the door system used on the one I built recently for a customer....
marc
Guys not that it may be possible to use but this was the door system used on the one I built recently for a customer....
marc
Thanks Marc for the idea. I had a spring setup to hold the doors but I could not find a way to actuate the doors via the strut in the up position. The servo tray is getting in the way so I decided to go the button valve and cylinder route.
#66
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RE: SkyMaster MB339 Build Thread
Hey Anton, can you or anyone else who has done so post some pics of the cockpit kit install? I am currently working on that and have already run into some problems and had to move some devices off to the side of the equipment tray as the cockpit tubs almost touch the tray.
#67
RE: SkyMaster MB339 Build Thread
Ian,
We ran into the same problem, part of the front equipment plate cannot be used for component placement as the bottom of the front cockpit almost touches it. In fact by gluing small strips of balsa on it, I use it as a bottom support for the cockpit pan itself.
BTW, I guess the pans can be installed in several ways.
The broad flanges on the pans look as if they have to be mounted in BETWEEN the cockpit hood and the fuselage, but that results in far from perfect fitting of the hood itself.
I trimmed down the flanges and now they slip UNDER the flanges of the fuse. This requires some jiggling but is OK to do once in a while, but will be a pain when have to be done for every flight,
so I elected to have regular access to all systems, like refuelling, charging and pumping air via the engine bay.
Here is a sced of the plates plus some pics of how I installed my systems. Sced is rotated to its side for better readability, after printing it.
We ran into the same problem, part of the front equipment plate cannot be used for component placement as the bottom of the front cockpit almost touches it. In fact by gluing small strips of balsa on it, I use it as a bottom support for the cockpit pan itself.
BTW, I guess the pans can be installed in several ways.
The broad flanges on the pans look as if they have to be mounted in BETWEEN the cockpit hood and the fuselage, but that results in far from perfect fitting of the hood itself.
I trimmed down the flanges and now they slip UNDER the flanges of the fuse. This requires some jiggling but is OK to do once in a while, but will be a pain when have to be done for every flight,
so I elected to have regular access to all systems, like refuelling, charging and pumping air via the engine bay.
Here is a sced of the plates plus some pics of how I installed my systems. Sced is rotated to its side for better readability, after printing it.
#68
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RE: SkyMaster MB339 Build Thread
Richard, do you have some shots of the cockpit pieces in place? It looks like the front dash has to be kept separate for install thus making the cockpit kit 3 pieces. I am getting ready to dump the whole thing because it is being such a PITA.
#69
RE: SkyMaster MB339 Build Thread
Ian,
The front dashboard slips into small slots from the front pan. The backside of the dash, (or in fact the side that is in front of the airplane....) has to be supported by a bracket or someting You have to glue into the fuse yourselves. My friend Leo already made this one, I did not get this far.
I will make you a picture to show how far I got until now.
I think the front dash is a liitle bit off scale, too large I guess, combined with the too small scale pilots the result is the poor guy flies IFR all the time, he is just staring at the panel, not overlooking it.
But indeed the cockpit inside will be 3 pieces, I don't mind, easier to install as a one piece.
BTW did You notice in my last pics the balsa T-bar on the middle plate, that also is a bottom support for the back cockpit pan.
The front dashboard slips into small slots from the front pan. The backside of the dash, (or in fact the side that is in front of the airplane....) has to be supported by a bracket or someting You have to glue into the fuse yourselves. My friend Leo already made this one, I did not get this far.
I will make you a picture to show how far I got until now.
I think the front dash is a liitle bit off scale, too large I guess, combined with the too small scale pilots the result is the poor guy flies IFR all the time, he is just staring at the panel, not overlooking it.
But indeed the cockpit inside will be 3 pieces, I don't mind, easier to install as a one piece.
BTW did You notice in my last pics the balsa T-bar on the middle plate, that also is a bottom support for the back cockpit pan.
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RE: SkyMaster MB339 Build Thread
Ian
I installed my cockpit kit as follows. The front dash cover is glued in place using a lightply support to the front of the cover glued to the underside of the fuselage at the middle of the dash cover. The front cockpit is held in place with two small countersunk screws through the tub flange, (glue some ply to the underside of the fuselage flange to provide grip for the screws) and the rear cockpit tub is glued to the inside of the canopy frame to give access to the rear of the cockpit area where I have located all items which need regular service access. It only takes seconds to remove the two screws on the front tub if you need to. I would advise you to glue in the glazing to the front screen before fitting the front dash cover as this makes access to fit the screen easier. I also lowered the front equipment tray by 25mm to give enough clearance for the front tub. Be carefull when glueing in the main canopy glazing as I distorted the frame on mine and had to do some surgery to get a good final fit. I did not trust the hatch latch to retain such a big canopy and replaced it with a 3mm wire rod accessed through the rear hatch, this also improves the scale appearance.
Best regards
John
I installed my cockpit kit as follows. The front dash cover is glued in place using a lightply support to the front of the cover glued to the underside of the fuselage at the middle of the dash cover. The front cockpit is held in place with two small countersunk screws through the tub flange, (glue some ply to the underside of the fuselage flange to provide grip for the screws) and the rear cockpit tub is glued to the inside of the canopy frame to give access to the rear of the cockpit area where I have located all items which need regular service access. It only takes seconds to remove the two screws on the front tub if you need to. I would advise you to glue in the glazing to the front screen before fitting the front dash cover as this makes access to fit the screen easier. I also lowered the front equipment tray by 25mm to give enough clearance for the front tub. Be carefull when glueing in the main canopy glazing as I distorted the frame on mine and had to do some surgery to get a good final fit. I did not trust the hatch latch to retain such a big canopy and replaced it with a 3mm wire rod accessed through the rear hatch, this also improves the scale appearance.
Best regards
John
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RE: SkyMaster MB339 Build Thread
Thanks John and Richard. That was the way I was thinking of going. I just hate having to rearrange things when they were looking all nice and ready to go. Your right though Richard, the front dash is too large to be even close to scale as well ass the instrument panel. Oh well, I guess it is better than a huge hole staring down into the tray.
#72
RE: SkyMaster MB339 Build Thread
Did a few things today, finally completed my teststand for the engine and did some testruns. This is my first new type (P160) engine with fast accel. Holy moly!
Had an air leak though, had my FESTO ball shutoff valve at the refuelling side connected to that blue festo airline, obviously does not match very well, as it leaked fuel and air. After I changed it to the clear tubing that comes with the JC, all OK.
If You look clearly You will notice the old type NC engine battery. The Lipo is already built into the airframe...
Also started at the tailplanes. Here is how I did the servo mounting.
I used the alu brackets that comes with the kit, screwed them (with sunken head M3 screws) to a 3mm plywood plate and glued that onto the bottom of the stabiliser. The opening in the stab for the servo needs only little to be widened top and bottom side.
I already bought larger servo horns, but I see that that I need even longer ones.
Hmmm, my shopping list for JetPower next weekend is GROWING...
Had an air leak though, had my FESTO ball shutoff valve at the refuelling side connected to that blue festo airline, obviously does not match very well, as it leaked fuel and air. After I changed it to the clear tubing that comes with the JC, all OK.
If You look clearly You will notice the old type NC engine battery. The Lipo is already built into the airframe...
Also started at the tailplanes. Here is how I did the servo mounting.
I used the alu brackets that comes with the kit, screwed them (with sunken head M3 screws) to a 3mm plywood plate and glued that onto the bottom of the stabiliser. The opening in the stab for the servo needs only little to be widened top and bottom side.
I already bought larger servo horns, but I see that that I need even longer ones.
Hmmm, my shopping list for JetPower next weekend is GROWING...
#74
RE: SkyMaster MB339 Build Thread
Marc,
Neat solution, what in earth is that all You've built in? I don't recognize some parts at all.
I am going to use the side walls in the engine bay as well, in order to have all servicing accessible from there.
Good idea to paint the inside of the fuse, looks very pro.
Btw, I have defuelled the system after the testrun and a full fuel system holds around 5,5 litres, including the hopper.
Neat solution, what in earth is that all You've built in? I don't recognize some parts at all.
I am going to use the side walls in the engine bay as well, in order to have all servicing accessible from there.
Good idea to paint the inside of the fuse, looks very pro.
Btw, I have defuelled the system after the testrun and a full fuel system holds around 5,5 litres, including the hopper.
#75
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RE: SkyMaster MB339 Build Thread
I followed your thread Marc, it was great. I finished the install and we flew the 339 on Sunday. Flies great!!! Tracks almost like a pattern plane. I had to put 2 3/4 pounds in the nose though, yikes[:@]