New project L-39
11-14-2008, 04:17 PM
#27
My Feedback: (5)
Join Date: Apr 2002
Location: Northamptonshire , UNITED KINGDOM
Posts: 4,994
Likes: 0
Received 18 Likes
on
17 Posts
RE: New project L-39
It certainly makes your euro look different Uwe! Thanks for sharing the photo with us and post one with it all finished!
I managed to spend a little time on the Albatros today. Nit as much as I would have liked as the kids needed some attention which turned out to be allot of fun anyway. Plus I had to build a foamy for indoor flying tomorrow night!
Anyway I started with the rudder.
Mine has no servo mount in my rudder which was a disappointment and this meant quite a long time was pent as the first mount that I made for a 8411 meant that the servo was sticking out below the base of the fin, which would mean cutting a hole in the face of the fin mount in the fuselage. In hindsight I should have just done that, but instead I chose to fit a smaller 9411 Jr servo on the rudder.
One of my hinge positions in the rudder was drilled out of line. Not too much of a problem as I needed to pen them up to clear the pivot of the hinge and allow enough movement.
To get the pinto point of the hinge on the centre of the radius of the rudder meant quite a bit of drilling into the rudder was required. I then had to open out a section either side of the hinge to allow some movement. Hopefully the photos will show what I am babbling on about.
I managed to spend a little time on the Albatros today. Nit as much as I would have liked as the kids needed some attention which turned out to be allot of fun anyway. Plus I had to build a foamy for indoor flying tomorrow night!
Anyway I started with the rudder.
Mine has no servo mount in my rudder which was a disappointment and this meant quite a long time was pent as the first mount that I made for a 8411 meant that the servo was sticking out below the base of the fin, which would mean cutting a hole in the face of the fin mount in the fuselage. In hindsight I should have just done that, but instead I chose to fit a smaller 9411 Jr servo on the rudder.
One of my hinge positions in the rudder was drilled out of line. Not too much of a problem as I needed to pen them up to clear the pivot of the hinge and allow enough movement.
To get the pinto point of the hinge on the centre of the radius of the rudder meant quite a bit of drilling into the rudder was required. I then had to open out a section either side of the hinge to allow some movement. Hopefully the photos will show what I am babbling on about.
11-14-2008, 04:27 PM
#29
My Feedback: (5)
Join Date: Apr 2002
Location: Northamptonshire , UNITED KINGDOM
Posts: 4,994
Likes: 0
Received 18 Likes
on
17 Posts
RE: New project L-39
Once I made sure once the hinges were in place the rudder could move freely I then glued the hinges into the rudder using 30 Min epoxy. When this was dry I used Hysol to glue the hinges into the fin. The reason for using hysol in this side is that I could build a pool of hysol inside the fin in front of the hinge post.
Before doing any of the hinge gluing I made sure the area around the pivot was well covered in Tri flow grease ( I hate sticky hinges )
While the glue was drying I taped the rudder to the fin and slid a thick piece of card between the rudder and fin at the top to ensure a slight distortion didnt cause binding of the two surfaces. Just to be sure I slid the fin ad rudder onto the fuselage to ensure it didnt bind here. Happily there was no need for any sanding and all worked well.
Before doing any of the hinge gluing I made sure the area around the pivot was well covered in Tri flow grease ( I hate sticky hinges )
While the glue was drying I taped the rudder to the fin and slid a thick piece of card between the rudder and fin at the top to ensure a slight distortion didnt cause binding of the two surfaces. Just to be sure I slid the fin ad rudder onto the fuselage to ensure it didnt bind here. Happily there was no need for any sanding and all worked well.
11-14-2008, 04:36 PM
#30
My Feedback: (5)
Join Date: Apr 2002
Location: Northamptonshire , UNITED KINGDOM
Posts: 4,994
Likes: 0
Received 18 Likes
on
17 Posts
RE: New project L-39
I marked where the servo horn would come through the fin skin and made a slot to clear the movement.
I then used 3 layers of 1/16th ply ( because thats all I had ) made a plate just over the size of the servo and screwed a pair of Tams Carbon servo L shaped mounts. About 1.5mm of the threads of the screws came through the bottom of this plate but this was soon flattened off on the sander. The 9411 was fixed in and then the plate was ready to hysol in place. I took a scuff board to the inside of the fin where this plate would attach to ensure a good bond.
Before gluing the servo plate in place I slotted the rudder for the servo horn. I used a 2mm drill to make the slot and filled the hole with Hysol. I really like the new carbon horns from skymaster as they have a really neat flange that tides up the fixing point of the horns.. Nice !
Happily this ws the only hinges on the model as the rest are all surface hinged
I then used 3 layers of 1/16th ply ( because thats all I had ) made a plate just over the size of the servo and screwed a pair of Tams Carbon servo L shaped mounts. About 1.5mm of the threads of the screws came through the bottom of this plate but this was soon flattened off on the sander. The 9411 was fixed in and then the plate was ready to hysol in place. I took a scuff board to the inside of the fin where this plate would attach to ensure a good bond.
Before gluing the servo plate in place I slotted the rudder for the servo horn. I used a 2mm drill to make the slot and filled the hole with Hysol. I really like the new carbon horns from skymaster as they have a really neat flange that tides up the fixing point of the horns.. Nice !
Happily this ws the only hinges on the model as the rest are all surface hinged
11-14-2008, 05:18 PM
#31
My Feedback: (5)
Join Date: Apr 2002
Location: Northamptonshire , UNITED KINGDOM
Posts: 4,994
Likes: 0
Received 18 Likes
on
17 Posts
RE: New project L-39
While the rudder and fin were drying it was time to pay attention the the stabs and elevators. As mentioned earlier these are pre hinged so it was just a case of fitting the servos and horns.
This in itself took a few hours because a) There were no servo mounts fitted ( Like the rudder ) and B) I didnt want to go with using the midi size servos as suggested. Its a personal thing when it comes to elevators. I just like as much servo power and precision as I can get and always feel better when I can bolt a 8411/ 8511 or 8711 to them. It was always going to be close when it came to the L-39 but a few measurements showed that a 8411 was a possibly... Just! Now this required a fair amount of grinding out inside each stab. I had to remove as much of the excess glue possible. Which as it turned out was quite allot. No one can excuse SM of being tight with the glue on this one. I then made two ply mounts ( Using one of the ply mounts SM provided) I then glued these to the rear spar and front spar wooden carrier inside each stab. There really was a minimal amount of space so these mounts were only just big enough to take the screws. But in the end it all worked out really well and the 8411's are a very snug fit.
It was then the same thing with the control horns. I was a little worried on these as the wooden spar in the front edge of the elevator is the only support for the control horns, SO I chose to open up the slot a little more and make a footing of hysol for each horn to seat.
You should also be able to see form my photos where I dremeled out the stab on the inside edge where the elevator was catching the composite surface when down elevator was applied. This not only allowed more movement but also made the entire movement soother.
This in itself took a few hours because a) There were no servo mounts fitted ( Like the rudder ) and B) I didnt want to go with using the midi size servos as suggested. Its a personal thing when it comes to elevators. I just like as much servo power and precision as I can get and always feel better when I can bolt a 8411/ 8511 or 8711 to them. It was always going to be close when it came to the L-39 but a few measurements showed that a 8411 was a possibly... Just! Now this required a fair amount of grinding out inside each stab. I had to remove as much of the excess glue possible. Which as it turned out was quite allot. No one can excuse SM of being tight with the glue on this one. I then made two ply mounts ( Using one of the ply mounts SM provided) I then glued these to the rear spar and front spar wooden carrier inside each stab. There really was a minimal amount of space so these mounts were only just big enough to take the screws. But in the end it all worked out really well and the 8411's are a very snug fit.
It was then the same thing with the control horns. I was a little worried on these as the wooden spar in the front edge of the elevator is the only support for the control horns, SO I chose to open up the slot a little more and make a footing of hysol for each horn to seat.
You should also be able to see form my photos where I dremeled out the stab on the inside edge where the elevator was catching the composite surface when down elevator was applied. This not only allowed more movement but also made the entire movement soother.
11-14-2008, 05:42 PM
#33
My Feedback: (12)
Join Date: Aug 2002
Location: Scottsdale, AZ
Posts: 4,462
Likes: 0
Received 0 Likes
on
0 Posts
RE: New project L-39
Looks good Ali, this was the same on the 339, same mounting style. I kind of like this method as the mount posts are easy to glue in and you dont have an ugly hatch on the bottom. Looks clean and functions well.
11-14-2008, 05:48 PM
#34
My Feedback: (5)
Join Date: Apr 2002
Location: Northamptonshire , UNITED KINGDOM
Posts: 4,994
Likes: 0
Received 18 Likes
on
17 Posts
RE: New project L-39
It was then onto the wings.
Again 8411's used on aileron and flap. The aileron servo needed a 300mm extension lead. I then spent a while making up the aileron servo mounts using the plywood blocks provided and aluminum pre tapped l shapes servo mounts. When I removed the servo cover I noticed a strange ply tray which I had never seen before. There was no mention to this in the instructions. These only referred to the plywood mounts which were supposed to be glued to the top skin of the wing. Not my favorite system as it can flex and in worst cases the servo can come loose. It also means that a very long servo arm is needed to get the linkage out of the wing.
As it turns out these plywood trays that are pre fitted into each wing are actually servo carriers. The servos are now screwed to the l shape Alu mounts which are then screwed to these carriers. A quick and simple fixment which puts the servo just where it needs to be. Shame the elevator and rudder were not so well thought out, and a real shame it was not mentioned in the instructions.
Slight problem when it came to installing the servo. There were no holes cut into the servo boxes to allow the servo leads to exit. Not a big issue. I cut one into the rear corner of each box. This put the servo leads into a channel that ran straight to the wing root with ease.
I made sure I ran some thin Zap into the holes where the servo fixing screws were going. Standard practice really as it does toughen up the ply a hell of allot.
Flap servo was pretty straight forward. I made a slight opening in the servo mount to allow the servo cable to exit through the servo mount rib.
Control fixment was just like the elevator. Again I was worried about the footing for the horns, so I built it up with hysol. I made the cut out in the wing for the flap servo horns slightly oversize as on this control allot of the clevis will need to go back into the wing when the flaps are lowered so space was required.
Only other thing that I found needed a little attention was the the aileron shrouds. mine had a little bit of masking tape and glue on them which was causing a small amount of binding on the ailerons. It was a quick fix to clean them up and it made the aileron movement so much smoother.
Again 8411's used on aileron and flap. The aileron servo needed a 300mm extension lead. I then spent a while making up the aileron servo mounts using the plywood blocks provided and aluminum pre tapped l shapes servo mounts. When I removed the servo cover I noticed a strange ply tray which I had never seen before. There was no mention to this in the instructions. These only referred to the plywood mounts which were supposed to be glued to the top skin of the wing. Not my favorite system as it can flex and in worst cases the servo can come loose. It also means that a very long servo arm is needed to get the linkage out of the wing.
As it turns out these plywood trays that are pre fitted into each wing are actually servo carriers. The servos are now screwed to the l shape Alu mounts which are then screwed to these carriers. A quick and simple fixment which puts the servo just where it needs to be. Shame the elevator and rudder were not so well thought out, and a real shame it was not mentioned in the instructions.
Slight problem when it came to installing the servo. There were no holes cut into the servo boxes to allow the servo leads to exit. Not a big issue. I cut one into the rear corner of each box. This put the servo leads into a channel that ran straight to the wing root with ease.
I made sure I ran some thin Zap into the holes where the servo fixing screws were going. Standard practice really as it does toughen up the ply a hell of allot.
Flap servo was pretty straight forward. I made a slight opening in the servo mount to allow the servo cable to exit through the servo mount rib.
Control fixment was just like the elevator. Again I was worried about the footing for the horns, so I built it up with hysol. I made the cut out in the wing for the flap servo horns slightly oversize as on this control allot of the clevis will need to go back into the wing when the flaps are lowered so space was required.
Only other thing that I found needed a little attention was the the aileron shrouds. mine had a little bit of masking tape and glue on them which was causing a small amount of binding on the ailerons. It was a quick fix to clean them up and it made the aileron movement so much smoother.
11-16-2008, 07:00 PM
#35
RE: New project L-39
I see Ali is moving on this project just fine and since he's working on the stabs and wings I decided to work on the main landing gear and the fuel tanks today, here is some of the work I completed today, this is just a prelude to some massive work to be coming soon during the Thanks giving, X-mas and New years weekends ( off 4 days each weekend ) 
.
.
11-16-2008, 07:11 PM
#36
RE: New project L-39
Few more.
Kelly wants smoke in this bird, I see that there is plenty of room for that, I could put a 32 oz. tank in between the fuel cells or I could go with 2 16oz. Nelgene like the pictures show.......decisions, decisions
Kelly wants smoke in this bird, I see that there is plenty of room for that, I could put a 32 oz. tank in between the fuel cells or I could go with 2 16oz. Nelgene like the pictures show.......decisions, decisions
11-16-2008, 08:15 PM
#37
RE: New project L-39
I did mesure the capacity of the fuel tanks and combine I end up with 130oz, this equeals to 10.8 mim at full thrust, I say with start and taxi time we can get at lest 7 mim of normal flying with at least 2 go arounds and still endup with fuel in the tanks [8D]
11-17-2008, 03:21 PM
#39
Join Date: May 2006
Location: southampton, , UNITED KINGDOM
Posts: 123
Received 0 Likes
on
0 Posts
RE: New project L-39
Hi,
How strong are your springs on the main legs? Mine when fuelled and sat on the ground has the oleos fully compressed, this means it sits level. The problem is there is no spare travel at all!. Skymaster sent me some more springs but these are so strong you get no movement on the legs at all.
Also if you fit the cockpit kit it gets very tight with the fuel tank pipes hitting the rear of the back seat.
Ian.
How strong are your springs on the main legs? Mine when fuelled and sat on the ground has the oleos fully compressed, this means it sits level. The problem is there is no spare travel at all!. Skymaster sent me some more springs but these are so strong you get no movement on the legs at all.
Also if you fit the cockpit kit it gets very tight with the fuel tank pipes hitting the rear of the back seat.
Ian.
11-17-2008, 11:54 PM
#41
RE: New project L-39
Hello my Fellow L-39 Builders,
I am assembling a Skymaster L-39 as we type. I have read your post and have some of the same issues with my kit. Let’s see, no mounts in the vertical or horizontal stabs that the instructions clearly refer to, Instructions skipping steps, rudder hinge points not drilled in alignment, rudder height to long causing it to make contact with the fuselage when installed, in order to achieve proper control service throws I had to sand the wing area between inboard ailerons and aileron root, trim trailing edge of rudder, file elongated slots in leading edge of rudder, and do some trimming on the elevator/horz stab areas. I was also missing the lower fuselage floor between the second and third fuselage formers, and the tail pipe aft former has to large[img][/img] of an inside diameter allowing the tail pipe to move around, but with all of the above stated, I still like the airplane. I did increase all servo-mounting locations to accept Futaba 9156 digital servos. This includes the elevators, and I added Futaba aluminum servo arms. It took some time to figure out and fabricate the servo mounts, but it paned out. I to am aware of the landing gear travel issue. I plan on adding a length of wood dowel material to the struts until I achieve the proper stiffness and travel I desire. I was a little concerned about no hard wood being in the control service horn locations, so I cut the leading edges of the elevators and added some, but have not decided what to do with the flaps and ailerons yet. (Any Ideas Anyone) I have a JetCat 120 for this bird and am really looking forward to it’s maiden flight, which I hope is before the first of the year.
I have added some pics for you to look at.
Keep me posted on your progress,
WARBIRDRCER
I am assembling a Skymaster L-39 as we type. I have read your post and have some of the same issues with my kit. Let’s see, no mounts in the vertical or horizontal stabs that the instructions clearly refer to, Instructions skipping steps, rudder hinge points not drilled in alignment, rudder height to long causing it to make contact with the fuselage when installed, in order to achieve proper control service throws I had to sand the wing area between inboard ailerons and aileron root, trim trailing edge of rudder, file elongated slots in leading edge of rudder, and do some trimming on the elevator/horz stab areas. I was also missing the lower fuselage floor between the second and third fuselage formers, and the tail pipe aft former has to large[img][/img] of an inside diameter allowing the tail pipe to move around, but with all of the above stated, I still like the airplane. I did increase all servo-mounting locations to accept Futaba 9156 digital servos. This includes the elevators, and I added Futaba aluminum servo arms. It took some time to figure out and fabricate the servo mounts, but it paned out. I to am aware of the landing gear travel issue. I plan on adding a length of wood dowel material to the struts until I achieve the proper stiffness and travel I desire. I was a little concerned about no hard wood being in the control service horn locations, so I cut the leading edges of the elevators and added some, but have not decided what to do with the flaps and ailerons yet. (Any Ideas Anyone) I have a JetCat 120 for this bird and am really looking forward to it’s maiden flight, which I hope is before the first of the year.
I have added some pics for you to look at.
Keep me posted on your progress,
WARBIRDRCER
11-18-2008, 02:07 PM
#45
Join Date: May 2006
Location: southampton, , UNITED KINGDOM
Posts: 123
Received 0 Likes
on
0 Posts
RE: New project L-39
Warbirder,
My flap horns mounted through the balsa spar. This meant that with the slot cut you could put a good fillet of Hysol on the bottom ( top skin) and the spar and leave the horn standing in it to dry. I mounted all my horns this way with Hysol, no problems so far. The problem with putting a wood dowel in the spring is you want the total travel just slower!!! an oil damper would be the perfect solution.
Ian.
My flap horns mounted through the balsa spar. This meant that with the slot cut you could put a good fillet of Hysol on the bottom ( top skin) and the spar and leave the horn standing in it to dry. I mounted all my horns this way with Hysol, no problems so far. The problem with putting a wood dowel in the spring is you want the total travel just slower!!! an oil damper would be the perfect solution.
Ian.
11-18-2008, 02:16 PM
#46
Senior Member
Join Date: May 2006
Location: elk grove,
CA
Posts: 489
Likes: 0
Received 0 Likes
on
0 Posts
RE: New project L-39
I think what hes is trying to do with the dowel is increase spring rate....by compressing spring with dowel the a/c weight wont completely bottom out trailing link gear...the air/oil strut would be great if you could find one to fit...than just pumpup to preload...maybe a unit from an r/c car???? k
11-18-2008, 03:00 PM
#47
My Feedback: (12)
Join Date: Aug 2002
Location: Scottsdale, AZ
Posts: 4,462
Likes: 0
Received 0 Likes
on
0 Posts
RE: New project L-39
ORIGINAL: jetting
Hi,
How strong are your springs on the main legs? Mine when fuelled and sat on the ground has the oleos fully compressed, this means it sits level. The problem is there is no spare travel at all!. Skymaster sent me some more springs but these are so strong you get no movement on the legs at all.
Also if you fit the cockpit kit it gets very tight with the fuel tank pipes hitting the rear of the back seat.
Ian.
Hi,
How strong are your springs on the main legs? Mine when fuelled and sat on the ground has the oleos fully compressed, this means it sits level. The problem is there is no spare travel at all!. Skymaster sent me some more springs but these are so strong you get no movement on the legs at all.
Also if you fit the cockpit kit it gets very tight with the fuel tank pipes hitting the rear of the back seat.
Ian.
Ian, the new landing gear is hydraulic so they should compress but upon touchdown will have a much better dampening effect than spring loaded. You could easily find stiffer springs if you like at the hardware store though.
11-19-2008, 12:40 AM
#49
RE: New project L-39
Thanks for the input everyone. Jetting, I am going to install my flap and aileron horns as you described. I guess with the Hysol fillet around the horn it is somewhat like a hardwood block. I am kind of old school when it comes to building, and as you all know we ran hardware through the surface to the horns. This new way of attaching horns kind of spooked me. I am currently mounting the turbine eletronic equipment, and I hope to have her ready for first runs soon. Did you guys go with the factory CG, or do you recommend something else? What about service throws, factory or not? I want this project to be a long term success so I am open for any help.
CARS II, How is your project coming?
JETTING, The landing shot looks good!!
Drdoom, Photos look good, but the one on the right looks like full scale to me. Is it yours?
Ali, Thanks for all of your detail. It will help me a lot to complete my wing construction.
Thanks,
WARBIRDRCER
CARS II, How is your project coming?
JETTING, The landing shot looks good!!
Drdoom, Photos look good, but the one on the right looks like full scale to me. Is it yours?
Ali, Thanks for all of your detail. It will help me a lot to complete my wing construction.
Thanks,
WARBIRDRCER
11-19-2008, 07:53 AM
#50
Join Date: May 2006
Location: southampton, , UNITED KINGDOM
Posts: 123
Received 0 Likes
on
0 Posts
RE: New project L-39
Warbirder,
I set mine up stock but my flaps are only as far as the gap cover allows. Not very clear but if i put the flaps any lower then they hit the trailing edge of the wing and jam. I will glue a piece of 1/4 sq spruce on the flap when I find time and this will keep the flap straight and allow more movement.
Thinwing,
If you increase the spring rate to much you find the plane sitting nosedown which makes takeoff interesting!! (tried that).
Ali,
How much are a set of new hydraulic legs only? I can swap the rest of the bits.
Ian.
I set mine up stock but my flaps are only as far as the gap cover allows. Not very clear but if i put the flaps any lower then they hit the trailing edge of the wing and jam. I will glue a piece of 1/4 sq spruce on the flap when I find time and this will keep the flap straight and allow more movement.
Thinwing,
If you increase the spring rate to much you find the plane sitting nosedown which makes takeoff interesting!! (tried that).
Ali,
How much are a set of new hydraulic legs only? I can swap the rest of the bits.
Ian.