JetLegend L39 Refurbishment
08-25-2014, 02:40 AM
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JetLegend L39 Refurbishment
I recently acquired a JetLegend L39 in real need of some TLC. As well as being generally in need of some tidying up, the model had a smoke oil fire which caused some damage to the rear fuselage. I therefore intend to carry out a full refurbishment of this model to make her beautiful again and turn her from this...
into this...
I'm not entirely convinced that anyone will be interested in such a 'build' thread, but for my part I would certainly appreciate any feedback/advice from the many fellow modellers out there who are greatly more experienced than I at this sort of thing. I'm always keen to learn from the real experts.
Just to say up front, I can't promise to post progress in real time as I'm not quite organised enough to manage that, but I've made a good start and will post chunks as and when I can.
Thanks
Mark
into this...
I'm not entirely convinced that anyone will be interested in such a 'build' thread, but for my part I would certainly appreciate any feedback/advice from the many fellow modellers out there who are greatly more experienced than I at this sort of thing. I'm always keen to learn from the real experts.
Just to say up front, I can't promise to post progress in real time as I'm not quite organised enough to manage that, but I've made a good start and will post chunks as and when I can.
Thanks
Mark
08-25-2014, 03:06 AM
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OK, so I said I'd made a start so here goes. First step was to total strip the model to a bare airframe, removing all servos, valves, wires and tubes, etc. I could then get on with the messy job of stripping off the old paint.
Imagine my surprise to find that lurking underneath the black/grey camo scheme was an original factory scheme in blue! The original scheme was painted in the mould so I will leave that and paint over it. Some of the fire damage to the side of the rear fuselage can be seen in the picture above and the damage underneath can be seen in this one below:
Next I marked out the damaged areas of fuselage which would have to be removed. The heat from the fire has caused distortion of the fibreglass as well as de-lamination of the gel coat in some areas which initially looked OK. As can be seen, despite keeping as much good fuselage as possible the areas to be removed are quite large!
No going back now.... This is what a jet looks like when you attack it with a cutting wheel!
Next...time to make a mould for the repair.
Imagine my surprise to find that lurking underneath the black/grey camo scheme was an original factory scheme in blue! The original scheme was painted in the mould so I will leave that and paint over it. Some of the fire damage to the side of the rear fuselage can be seen in the picture above and the damage underneath can be seen in this one below:
Next I marked out the damaged areas of fuselage which would have to be removed. The heat from the fire has caused distortion of the fibreglass as well as de-lamination of the gel coat in some areas which initially looked OK. As can be seen, despite keeping as much good fuselage as possible the areas to be removed are quite large!
No going back now.... This is what a jet looks like when you attack it with a cutting wheel!
Next...time to make a mould for the repair.
08-25-2014, 06:56 AM
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This is a nice thread, as I have one of those in the Slovakian paint
which I would like to refurbish. The only big problem I have is the second bulkhead
which is broken. I'm trying to get one. That's the one that holds the front gear.
But this is going to be interesting.
hmarmaizmd717
which I would like to refurbish. The only big problem I have is the second bulkhead
which is broken. I'm trying to get one. That's the one that holds the front gear.
But this is going to be interesting.
hmarmaizmd717
08-26-2014, 01:32 PM
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Here are some pictures of the first stage of the repair to the fire damaged fuselage.
Before the permanent fibreglass repair can be done a mould needs to me made which will be placed over the hole. In order to create a surface from which this mould can be formed I created a temporary 'repair'. The hole was first covered from the back with thin sheet balsa.
The balsa was then coated with a layer of fine filler up to the level of the fuselage surface.
The filler was wet sanded until the desired shape was achieved. It is important to achieve as close to perfect a finish as possible as the mould will reproduce any imperfections.
The damaged area which was removed incorporated a couple of panel line features. To incorporate these in the mould they must be created in the temporary surface. The lines were laid out with chart tape...
....and then the filled surface was sprayed with a couple of coats of high build primer.
The primer was then wet sanded until the chart tape just became visible. The tape was then removed to leave the embedded panel lines. The surface is now ready to lay up the mould.
I used PVA release agent for this job as I don't need a mirror finish to the mould and PVA is easy to apply and provides a reliable release. This picture shows the surface after it has been treated with the release agent.
Next, a layer of gel coal was applied and left until it is just tacky.
Three layers of 160g cloth were then wet laid on top of the gel coat. This was then left to cure for 8 hours.
This is the finished mould. Before it was removed from the fuselage holes were drilled through to enable the mould to be precisely located.
Now that I have a mould the permanent repair can be carried out. Pictures of that to follow....
Before the permanent fibreglass repair can be done a mould needs to me made which will be placed over the hole. In order to create a surface from which this mould can be formed I created a temporary 'repair'. The hole was first covered from the back with thin sheet balsa.
The balsa was then coated with a layer of fine filler up to the level of the fuselage surface.
The filler was wet sanded until the desired shape was achieved. It is important to achieve as close to perfect a finish as possible as the mould will reproduce any imperfections.
The damaged area which was removed incorporated a couple of panel line features. To incorporate these in the mould they must be created in the temporary surface. The lines were laid out with chart tape...
....and then the filled surface was sprayed with a couple of coats of high build primer.
The primer was then wet sanded until the chart tape just became visible. The tape was then removed to leave the embedded panel lines. The surface is now ready to lay up the mould.
I used PVA release agent for this job as I don't need a mirror finish to the mould and PVA is easy to apply and provides a reliable release. This picture shows the surface after it has been treated with the release agent.
Next, a layer of gel coal was applied and left until it is just tacky.
Three layers of 160g cloth were then wet laid on top of the gel coat. This was then left to cure for 8 hours.
This is the finished mould. Before it was removed from the fuselage holes were drilled through to enable the mould to be precisely located.
Now that I have a mould the permanent repair can be carried out. Pictures of that to follow....
Last edited by Beachy1968; 08-26-2014 at 09:47 PM.
08-28-2014, 10:08 AM
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Hi FELIrc
I usually use paint stripper that is safe on GRP (it is intended for fibreglass boats), however the type of paint on this model would not come off with this. Luckily, however, I found that it came straight off when wiped with a rag soaked in cellulose paint thinners.
I usually use paint stripper that is safe on GRP (it is intended for fibreglass boats), however the type of paint on this model would not come off with this. Luckily, however, I found that it came straight off when wiped with a rag soaked in cellulose paint thinners.
08-28-2014, 10:31 AM
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This set of 8 pictures shows how I used the mould I made (see post 6) to carry out the final repair.
1) The temporary repair that was used to create the mould was removed. As it was only balsa with a very thin skim of filler it pushed out easily.
2) The mould was attached to the outside firstly using the locating holes drilled before it was first released. Further screws were used to ensure that the edges of the hole are pulled as tightly against the mould as possible.
3)This shows the gel coat added to the inside of the mould. After this became tacky one layer of 100g and one layer of 160g glass cloth were wet laid on top. As much excess resin as possible was removed to make the repair as light as possible.
4) After 8 hours the repair was fully cured and the mould was removed to reveal the finished result.
5) The panel lines have been moulded into the repair. All that was needed to finish was some light sanding around the edges where some resin had crept between the mould and the fuselage.
6) This shows the finished repair from the inside. The holes left from the screws were filled using a small dab of filler made from resin and microbaloons.
7) A very light coat of primer was applied to the finished repair to check for any surface imperfections such as pinholes.
8) The finished repair is as strong as the original structure and adds barely any extra weight. From the outside it will be totally invisible once the model is painted.
Next the larger hole underneath will be repaired in the same way i.e. a temporary repair is done so a mould can be made and then the mould is used to complete the final fibreglass repair. I'll post pictures of the larger hole repair tomorrow.
1) The temporary repair that was used to create the mould was removed. As it was only balsa with a very thin skim of filler it pushed out easily.
2) The mould was attached to the outside firstly using the locating holes drilled before it was first released. Further screws were used to ensure that the edges of the hole are pulled as tightly against the mould as possible.
3)This shows the gel coat added to the inside of the mould. After this became tacky one layer of 100g and one layer of 160g glass cloth were wet laid on top. As much excess resin as possible was removed to make the repair as light as possible.
4) After 8 hours the repair was fully cured and the mould was removed to reveal the finished result.
5) The panel lines have been moulded into the repair. All that was needed to finish was some light sanding around the edges where some resin had crept between the mould and the fuselage.
6) This shows the finished repair from the inside. The holes left from the screws were filled using a small dab of filler made from resin and microbaloons.
7) A very light coat of primer was applied to the finished repair to check for any surface imperfections such as pinholes.
8) The finished repair is as strong as the original structure and adds barely any extra weight. From the outside it will be totally invisible once the model is painted.
Next the larger hole underneath will be repaired in the same way i.e. a temporary repair is done so a mould can be made and then the mould is used to complete the final fibreglass repair. I'll post pictures of the larger hole repair tomorrow.
Last edited by Beachy1968; 08-28-2014 at 10:34 AM.
09-01-2014, 09:56 AM
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So here's the final set of pics showing the repair of the fire damage. This set shows the repair of the larger area on the bottom of the fuselage. The process was the same as previously shown so just a brief description for each picture...
1) Removal of the damaged fibreglass left a big hole!
2) The hole was blanked off with thin balsa tacked around the edges with CA glue.
3) Fuselage filled and wet sand to the level of the rest of the fuselage skin. This was much more tricky than the first hole as the fuselage has some double curvature here.
4) A few coats of high build primer to sort out any minor surface imperfections.
5) The primer is then sanded back to give the final finish for the mould. The underside has shallower panel lines running through the repair area so I decided to create these in the final paint rather than include them in the mould.
6) Mould release agent applied to the repair area.
7) A nice thick gel coat comes next.
8) The first layer of glass cloth is laid over the gel coat.
9) A total of 3 layers of 160g cloth was wet laid over the repair area to give a suitably stiff final mould.
10) This bit's fun. The mould has cured and has been removed and so the temporary surface repair can be broken out to make the hole again! Reminds me of eating an Easter egg!
11) The finished mould and the hole it will be used to repair.
12) View from the outside after the repair has been laid up from the inside.
13) View from the inside of the finished repair. As before one 100g layer and one 160g layer was used to give a total thickness similar to the original material.
14) The cured repair after the mould has been removed. Again, some minor sanding was required where resin has crept between the mould and the fuselage around the edges.
15) A very thin coat of primer shows up any minor imperfections which can then be rectified. The fire damage to the fuselage has now been fully repaired.
I shall be away for a couple of weeks now so there will be no more progress until I'm back, then I will start the paint....
1) Removal of the damaged fibreglass left a big hole!
2) The hole was blanked off with thin balsa tacked around the edges with CA glue.
3) Fuselage filled and wet sand to the level of the rest of the fuselage skin. This was much more tricky than the first hole as the fuselage has some double curvature here.
4) A few coats of high build primer to sort out any minor surface imperfections.
5) The primer is then sanded back to give the final finish for the mould. The underside has shallower panel lines running through the repair area so I decided to create these in the final paint rather than include them in the mould.
6) Mould release agent applied to the repair area.
7) A nice thick gel coat comes next.
8) The first layer of glass cloth is laid over the gel coat.
9) A total of 3 layers of 160g cloth was wet laid over the repair area to give a suitably stiff final mould.
10) This bit's fun. The mould has cured and has been removed and so the temporary surface repair can be broken out to make the hole again! Reminds me of eating an Easter egg!
11) The finished mould and the hole it will be used to repair.
12) View from the outside after the repair has been laid up from the inside.
13) View from the inside of the finished repair. As before one 100g layer and one 160g layer was used to give a total thickness similar to the original material.
14) The cured repair after the mould has been removed. Again, some minor sanding was required where resin has crept between the mould and the fuselage around the edges.
15) A very thin coat of primer shows up any minor imperfections which can then be rectified. The fire damage to the fuselage has now been fully repaired.
I shall be away for a couple of weeks now so there will be no more progress until I'm back, then I will start the paint....
Last edited by Beachy1968; 09-01-2014 at 09:59 AM.
11-27-2014, 01:40 AM
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First of all, sorry to anyone who was following this thread for the long gap since my last post. After coming back from my holiday I decided to start another related project - to build a proper spray room. I've been meaning to do this for a while to give me a cleaner and safer environment to paint in. So, after much toil, the dark, dusty, junk filled space that is supposed to be a garage has become this!
I have completed one small job on the L39. The original model had an internal linkage for the rudder, which has been converted to a more conventional external control linkage. The only problem with this is that whoever made the modification decided to insert the servo from below and glue it in so that it could never be removed! Not the best long term solution, so I have created a servo hatch so that the servo can be accessed and removed if needed. I simply marked the required shape and cut a hole with a scalpel. I used fibreglass sheet to create an internal doubler. Just need to drill holes in the corners for the retaining screws.
The new paint shop will be put to the test today. Time to shoot some primer....
I have completed one small job on the L39. The original model had an internal linkage for the rudder, which has been converted to a more conventional external control linkage. The only problem with this is that whoever made the modification decided to insert the servo from below and glue it in so that it could never be removed! Not the best long term solution, so I have created a servo hatch so that the servo can be accessed and removed if needed. I simply marked the required shape and cut a hole with a scalpel. I used fibreglass sheet to create an internal doubler. Just need to drill holes in the corners for the retaining screws.
The new paint shop will be put to the test today. Time to shoot some primer....
Last edited by Beachy1968; 11-27-2014 at 01:56 AM.
11-27-2014, 10:47 AM
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OK, primer done. I have used white primer as this is the correct value shade for the base coat colours I will be using such as yellow, greys and white. Other than that its your usual 4:1 2K product, thinned down a bit as I don't need the high build properties and certainly don't want the resulting weight! Next, a lot of wet sanding.....:-(
12-03-2014, 08:06 AM
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Way above my skill level for sure, Great Job. To kind of pair things up, here is a Link to a Composite Wing repair that was done on an a BVM Electra. http://www.rcgroups.com/forums/showt...Electra&page=9 it starts on Post 1081
Turbulence
Turbulence
12-03-2014, 11:12 AM
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I'm glad this is of some interest to someone out there.
So, after a few busy days I finally got back into the workshop today. Got most of the wet sanding done - so boring! Although I moulded panel lines into the fibreglass repair on the fuselage side I decided that for the larger repair underneath it would be quicker to use the old primer over tape trick to create the panel lines. For those of you not familiar with this it involves laying out panel lines with very thin tape and then applying a coat of high build primer. When the primer is dry you sand the primer back until the tape is exposed and then peel the tape off. This then leaves panel lines in the form of grooves in the primer. I'm not a fan of this technique on a whole plane as it obviously requires quite a thick (and thus heavy) coat of primer, but for small areas like this it works very well. I used 1mm chart tape here, and will hit the area with another coat of primer tomorrow. The lines extend beyond the repaired area to ensure the existing lines are not filled by overspray. Bye for now.
So, after a few busy days I finally got back into the workshop today. Got most of the wet sanding done - so boring! Although I moulded panel lines into the fibreglass repair on the fuselage side I decided that for the larger repair underneath it would be quicker to use the old primer over tape trick to create the panel lines. For those of you not familiar with this it involves laying out panel lines with very thin tape and then applying a coat of high build primer. When the primer is dry you sand the primer back until the tape is exposed and then peel the tape off. This then leaves panel lines in the form of grooves in the primer. I'm not a fan of this technique on a whole plane as it obviously requires quite a thick (and thus heavy) coat of primer, but for small areas like this it works very well. I used 1mm chart tape here, and will hit the area with another coat of primer tomorrow. The lines extend beyond the repaired area to ensure the existing lines are not filled by overspray. Bye for now.
12-07-2014, 02:34 AM
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Quick update. I've given the repaired area another coat of primer in order to create the missing panel lines. When dry, the primer was then sanded back until the tape showed through. The tape was then carefully removed to leave the embedded lines. Because the moulded panel lines elsewhere on the model are quite shallow I then gave the area a further sand to reduced the depth a bit.
Nearly time to put the colour on!
Nearly time to put the colour on!
12-08-2014, 07:34 AM
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Dave, I've got a couple of days free this week so all being well I should be done for in time for CJ. Never been to Abingdon, so I'm looking forward to it.
Thanks for the kind words everyone. Hopefully I will have much more of interest to post by the end of the week.
Thanks for the kind words everyone. Hopefully I will have much more of interest to post by the end of the week.