Nitro Models 90" P-38 (1/7 scale) with 3 piece wing and more
06-13-2014, 07:08 PM
#1027
My Feedback: (24)
Hey guys, this is a dup post from the p-38 brotherhood thread. Hoping you guys could comment
Finished up the NP-38 tonight, and was hoping to fly it tomorrow but a CG shift when gear retracts is going to delay that. Relocated batteries so model balances a little aft with gear up. With gear down, it is 1.125" nose heavy. Wing chord is roughly 13.5" just outboard of booms, so an almost 1.25" shift with gear movement seems like a lot.
My thoughts are balance it slightly nose heavy with gear down for initial flights and start moving the CG back, trying gear up at a good altitude. I think it will fly great with gear up, but 1.125" fwd seems way to nose heavy for takeoff and landing. If I set it up for gear down, an 1"+ aft CG isn't a great prospect either. Thinking it is going to end up somewhere in the middle
Any advice, or experiences would be welcome
Finished up the NP-38 tonight, and was hoping to fly it tomorrow but a CG shift when gear retracts is going to delay that. Relocated batteries so model balances a little aft with gear up. With gear down, it is 1.125" nose heavy. Wing chord is roughly 13.5" just outboard of booms, so an almost 1.25" shift with gear movement seems like a lot.
My thoughts are balance it slightly nose heavy with gear down for initial flights and start moving the CG back, trying gear up at a good altitude. I think it will fly great with gear up, but 1.125" fwd seems way to nose heavy for takeoff and landing. If I set it up for gear down, an 1"+ aft CG isn't a great prospect either. Thinking it is going to end up somewhere in the middle
Any advice, or experiences would be welcome
06-13-2014, 11:17 PM
#1028
My Feedback: (13)
Hay 70 Ragtop,
That is a nice looking model...very nice looking. I can't wait to hear about the first flights of your P-38 and how quick she is.
The CG will shift aft a bit more then most models and if you look at the retracts...all move aft to retract. I've balanced mine with the model level with the gear retracted, so when its time to land, the model is a bit nose heavy. I just keep reminding myself to keep the speed up and fly it down to the runway, when you land. Some times, easier said then done...but the reality of flying this airframe. Speed will allow it to fly on one engine...and not to many P-38's survive a single engine landing. That's the nature of the beast...and such a beautiful one too. Your finish is a lot like mine and you have to admit, WWII Invasion Strips look really sweet on this model.
Soft Landings Always,
Bobby of Maui
That is a nice looking model...very nice looking. I can't wait to hear about the first flights of your P-38 and how quick she is.
The CG will shift aft a bit more then most models and if you look at the retracts...all move aft to retract. I've balanced mine with the model level with the gear retracted, so when its time to land, the model is a bit nose heavy. I just keep reminding myself to keep the speed up and fly it down to the runway, when you land. Some times, easier said then done...but the reality of flying this airframe. Speed will allow it to fly on one engine...and not to many P-38's survive a single engine landing. That's the nature of the beast...and such a beautiful one too. Your finish is a lot like mine and you have to admit, WWII Invasion Strips look really sweet on this model.
Soft Landings Always,
Bobby of Maui
06-14-2014, 05:39 AM
#1029
Good morning 70 Ragtop. First let me explain where I am coming from regarding the P-38. My first was in the distant past, a Royal and was powered by .61's, the next two I built up from Wing Manufacturing short kits specifically to compete in the old SWRA warbird pylon races here in the southwest. Both were powered by .46s and were successfully raced for several seasons. One was eventually lost but the other survives to this day. Both had rearward retracting units.
First I would like to suggest that unless an airplane is level when you balance it then you have not balanced it where you thought, in the case of slightly nose down you have balanced at some unknown point forward. You have just thrown the suggested balance point right out the window. Also the concept of balancing some specific measurement forward or aft is not balancing at all gear up or down.
Now let talk about that suggested balance point, it is just that a suggestion and I DO NOT TRUST nitro planes suggestions instead I prefer to make my own and for every warbird I have ever setup and or raced/sport flown 25% mac is what works for me. So how do I find that 25%, very easy and the method is called mid span averaging. Just measure the chord half way between the wing tip and the fuselage or central pod, divide this measurement out there by four and this is how far back from the leading edge out there at that half way point your target CG will be. All that is left to do is simply project this inward to the fuselage if you like for ease of balancing.
Bob Paris has it right, meaning I want that airplane to balance at that 25%mac in flight with the gear retracted and a want the cg to meve forward when extended for the landing.
John
Last edited by JohnBuckner; 06-14-2014 at 05:43 AM.
06-14-2014, 08:37 PM
#1030
My Feedback: (24)
Thanks Guys
The Nitro planes CG measurement in the manual is at 29% of MAC, which is not to bad. That was developed with no retracts though. The 1.25" shift in CG I am getting is about a 8% shift of MAC. Totally expected the shift when gear moves. I believe I'm getting such a large change as the plane is so light, and the gear is relatively heavy with long struts.
I think I am going to set it a 25% with gear down, try it to see how responsive the elevator is. From there, move it fwd as much as I can, and still like the way it lands. I like warbirds a little nose heavy, but you've got to be able to slow them down. If I balance it at 25%MAC with gear up, its going to balance around 17%MAC with gear down, that's pretty nose heavy. Thinking it will be pretty sluggish, and may simply run out of elevator authority before it slows down, which is hard on gear.
If I can get it a little nose heavy with gear down, say 23, or 24%MAC, or even if it ends up at 25%, that would be 31-33% gear up. At speed, that should be fine, I think most of my models are a little tail heavy anyways.
There was a conversation on the p-38 brotherhood about this very subject when one on the guys, with lots of P-38 experience, stated he balances his with gear down. Naturally I asked him why gear down, better to be nose heavy than tail. His answer was he wanted the model perfectly balanced when he got close to the ground. At speed, the cg being further aft isn't much of an issue
At the time, I wasn't completely sold, but after running the numbers on this model, makes perfect sense to me. Now just have to validate the theory, and fly it!
The Nitro planes CG measurement in the manual is at 29% of MAC, which is not to bad. That was developed with no retracts though. The 1.25" shift in CG I am getting is about a 8% shift of MAC. Totally expected the shift when gear moves. I believe I'm getting such a large change as the plane is so light, and the gear is relatively heavy with long struts.
I think I am going to set it a 25% with gear down, try it to see how responsive the elevator is. From there, move it fwd as much as I can, and still like the way it lands. I like warbirds a little nose heavy, but you've got to be able to slow them down. If I balance it at 25%MAC with gear up, its going to balance around 17%MAC with gear down, that's pretty nose heavy. Thinking it will be pretty sluggish, and may simply run out of elevator authority before it slows down, which is hard on gear.
If I can get it a little nose heavy with gear down, say 23, or 24%MAC, or even if it ends up at 25%, that would be 31-33% gear up. At speed, that should be fine, I think most of my models are a little tail heavy anyways.
There was a conversation on the p-38 brotherhood about this very subject when one on the guys, with lots of P-38 experience, stated he balances his with gear down. Naturally I asked him why gear down, better to be nose heavy than tail. His answer was he wanted the model perfectly balanced when he got close to the ground. At speed, the cg being further aft isn't much of an issue
At the time, I wasn't completely sold, but after running the numbers on this model, makes perfect sense to me. Now just have to validate the theory, and fly it!
Last edited by 70 ragtop; 06-14-2014 at 08:43 PM.
08-14-2014, 05:32 AM
#1031
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Location: fouquieres les bethune, FRANCE
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Help
Hi All
I have some problems to fix the doors hinges
I always have a space about 5 mm between the fuselage and the door.
How do you glue the hinges ?
have you some picture to explain me.
The hinges are Robart's hinges
thank's for your help )
!
Dominique
I have some problems to fix the doors hinges
I always have a space about 5 mm between the fuselage and the door.
How do you glue the hinges ?
have you some picture to explain me.
The hinges are Robart's hinges
thank's for your help )
!
Dominique
08-14-2014, 12:20 PM
#1032
My Feedback: (24)
Hi Dom
It looks like you need to bias the hinge the other way. I believe the part that has the U shape needs to be closer to the edge of the door, and the half with the hinge pin needs to be further away from the edge of the door opening. I will try to get some pictures tonight, but if you cut a couple small pieces of balsa and try it with the hinge pin close to the edge, and then try it with hinge pin as far away from opening as you can, you will see the difference.
Want to try to mount hinge so skin/structure thickness is pretty close to the same on both sides. Finally, sometimes need to add shims, or even wedge shaped shims to get the right angle
It looks like you need to bias the hinge the other way. I believe the part that has the U shape needs to be closer to the edge of the door, and the half with the hinge pin needs to be further away from the edge of the door opening. I will try to get some pictures tonight, but if you cut a couple small pieces of balsa and try it with the hinge pin close to the edge, and then try it with hinge pin as far away from opening as you can, you will see the difference.
Want to try to mount hinge so skin/structure thickness is pretty close to the same on both sides. Finally, sometimes need to add shims, or even wedge shaped shims to get the right angle
08-19-2014, 02:01 PM
#1033
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Thank you for your explanations !
I succeed to mount the hinge.
I can continue !
One question more , do you know the thickness of the foam on the center boom ?
I succeed to mount the hinge.
I can continue !
One question more , do you know the thickness of the foam on the center boom ?
08-19-2014, 05:32 PM
#1035
Here is a picture but a poor one at that.
I measured the foam depth on my N P-38 and it looks like 1-1/4" at the mid section.
I had the same issues as you with the bay doors. What I did is mocked up several different wedges at various angles and inserted them on the boom side until I got the doors to close perfect.
Hope this helps.
Last edited by panhandler; 10-17-2014 at 06:53 PM.
09-24-2014, 04:23 PM
#1038
Member
Do you still have this to sell?
Well guys, Let's crank it up if you like
!!!! This is it!!!! I'm sure all you P-38 lovers will enjoy this. Here is what I have on the 'Nitro Planes 90" P-38 mod Kit'. You will receive these items.
-a complete manual for the mods including my set up and flying suggestions
-bottom boom formers including the ones for the main gear doors
-main gear door templates
-new root and outer wing panel ribs (light ply) including the inner ones (aviation ply) for the wing bolts
-new aviation ply main and nose gear mounts with supports
-new servo mounts (aviation ply) for the booms
-slide out air valve tray for the nose with servo mount (light ply)
-template for the nose gear door
-cross section full scale drawing of the new cowl shape
-template cross sections for the crew pod bottom
-parts for the wing cover frames
-a bill of materials for the balsa and hardware needed to complete the mods with as many suggested sources as I can give you
-a CD with many pictures of the processes and some shots of the finished plane for reference. Many are in this thread, but I have added more.
-my personal support throughout your upgrades
I'm thinking $79 for the kit. How does all that sound to you guys? Did I miss anything you think you will need? If so, please let me know and I will include it. I plan to put these together as they are ordered and would like a (1) week lead to ship. I'm ready to take orders and don't need any money till I'm ready to ship, at which time I can let the builder know a day or two in advance so as not to hold it up.
This plane is available again from NitroPlanes for $215, so maybe a few more can enjoy her now. IMO, these mods can easily turn this P-38 into one worth 4 or 5 times that, if not more.
If you have any suggestions on marketing to get the word out on this, please pass them along.
Please send me a PM with your orders, and any suggestions can be posted right here.
Thanks for all your encouragement through my build and now I hope I can give some back to see others enjoy this plane to the fullest, like I do.
!!!! This is it!!!! I'm sure all you P-38 lovers will enjoy this. Here is what I have on the 'Nitro Planes 90" P-38 mod Kit'. You will receive these items.-a complete manual for the mods including my set up and flying suggestions
-bottom boom formers including the ones for the main gear doors
-main gear door templates
-new root and outer wing panel ribs (light ply) including the inner ones (aviation ply) for the wing bolts
-new aviation ply main and nose gear mounts with supports
-new servo mounts (aviation ply) for the booms
-slide out air valve tray for the nose with servo mount (light ply)
-template for the nose gear door
-cross section full scale drawing of the new cowl shape
-template cross sections for the crew pod bottom
-parts for the wing cover frames
-a bill of materials for the balsa and hardware needed to complete the mods with as many suggested sources as I can give you
-a CD with many pictures of the processes and some shots of the finished plane for reference. Many are in this thread, but I have added more.
-my personal support throughout your upgrades
I'm thinking $79 for the kit. How does all that sound to you guys? Did I miss anything you think you will need? If so, please let me know and I will include it. I plan to put these together as they are ordered and would like a (1) week lead to ship. I'm ready to take orders and don't need any money till I'm ready to ship, at which time I can let the builder know a day or two in advance so as not to hold it up.
This plane is available again from NitroPlanes for $215, so maybe a few more can enjoy her now. IMO, these mods can easily turn this P-38 into one worth 4 or 5 times that, if not more.
If you have any suggestions on marketing to get the word out on this, please pass them along.
Please send me a PM with your orders, and any suggestions can be posted right here.
Thanks for all your encouragement through my build and now I hope I can give some back to see others enjoy this plane to the fullest, like I do.
01-02-2016, 12:29 PM
#1039
My Feedback: (24)
I guys, I know this is a long shot. I had some sort of problem on the takeoff run this past summer. One side didn't come up on power for some reason, and I wrecked it. Lucky the left wing took the impact, and saved all the $$ stuff
Have to say, I miss this plane, and would like to fix it. Wondering if anyone has a wrecked carcass with a salvageable left wing they would part with, or even a kit?
Thanks
Have to say, I miss this plane, and would like to fix it. Wondering if anyone has a wrecked carcass with a salvageable left wing they would part with, or even a kit?
Thanks
01-02-2016, 12:56 PM
#1040
Join Date: Feb 2006
Location: IN
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Sorry to see that!
I know it wasn't the intent of your post, but if you decide to sell the wreckage let me know. I still haven't started building mine yet and could use retracts, etc. I hope to start work on mine within the next month or so.
I know it wasn't the intent of your post, but if you decide to sell the wreckage let me know. I still haven't started building mine yet and could use retracts, etc. I hope to start work on mine within the next month or so.
01-02-2016, 02:20 PM
#1041
I have some parts guys including a complete kit. Thought maybe someday Nitro Planes would re-release this plane being as popular as it once was, and how good that wing did. Maybe even incorporating some of the improvements we made like the three piece wing.
I was intending to build another one some day, but we are very busy for the foreseeable future.
I was intending to build another one some day, but we are very busy for the foreseeable future.
01-02-2016, 05:56 PM
#1042
My Feedback: (13)
Hay Ram3500,
If you ever decide to part it out...I need two turbo covers, one left and one right. I'm sorry to hear your P-38 had a hard landing and to this day...I've bet to maiden my bird.
I would love to do away with the fiberglass units I was sold by another modeler. The parts I bought seem to soften in the sun so I keep her indoors hanging up on the ceiling. I've the engines dialed in and she came out to 18 lbs. gross weight. The model built way tail heavy...but I did build in a removable stabilizer.
Happy New Year,
Bobby of Maui
If you ever decide to part it out...I need two turbo covers, one left and one right. I'm sorry to hear your P-38 had a hard landing and to this day...I've bet to maiden my bird.
I would love to do away with the fiberglass units I was sold by another modeler. The parts I bought seem to soften in the sun so I keep her indoors hanging up on the ceiling. I've the engines dialed in and she came out to 18 lbs. gross weight. The model built way tail heavy...but I did build in a removable stabilizer.
Happy New Year,
Bobby of Maui
