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Nitro Models 90" P-38 (1/7 scale) with 3 piece wing and more

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Old 01-15-2008, 08:50 PM
  #1
ram3500-RCU
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Default Nitro Models 90" P-38 (1/7 scale) with 3 piece wing and more

Well, after having this plane a couple years, I am finally getting started on it. I have given this a lot of thought and after vacillating back and forth over nitro or electric, I'm going with what I am most familiar with on this one. I will be installing two new Moki 61s with Pitts mufflers. The three biggest mods will be, the three piece wing, and rounding the bottom of the booms, and the retracts. So far, the wing is cut apart outside the booms and the center sections are joined together (pictured). They will be permanently attached to the booms and holes will be cut through the sheeting to access the compartments below. She will stay on her gear for transport, the way it should be. The way Nitro has this set up is totally stupid.

Here is a list of some of the mods I intend for her.

-three piece wing with carbon fiber wing tubes for the outboard sections
-rounding off the bottom of the booms for a more scale look and to make more room for the wheels when retracted
-adding retracts with scale looking struts and gear doors
-adding cockpit detail to include a full body pilot with parachute and other gear, and interior detail
-adding the missing canon to the nose
-installing the counter balances to the elevator
-installing the turbo scoops on the sides of the booms just under the trailing edges
-adding some fairings to the center pod and wing attachment
-adding the cross bracing to the canopy
-possibly turning the flaps into the fowler type (not sure yet on this one)
-detailing the appearance with Grey paint on the bottom, weathering, panel detail, simulated lights, polished ovals on the nocells, etc

The plane is exceptionally light to start with, so I think I can get this done and still have a lighter wing loading than most of these bigger war birds have. I'm finally mentally into this project and hope to see it through for a maiden this spring. The wing tubes were holding me up. I had the tubes but couldn't find the sleeves anywhere. A friend made me a pair out of glass, and now I'm off the drawing board and on the building table.
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Old 01-15-2008, 10:44 PM
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Default RE: Nitro 90" (1/7 scale)P-38J Build with mods

I will be following your wing mod. Thats what I`m planning to do with mine.
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Old 01-15-2008, 11:16 PM
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Default RE: Nitro 90" (1/7 scale)P-38J Build with mods

I did the math on the tires and we need 5" mains and 3 7/8 " nose tires. I think I will cheat the mains down to 4 3/4" but that will still be a lot of tire to conceal. The booms aren't deep enough. I wish they had just rounded them to begin with. They did fine on the top. I don't see what the big deal was on the bottom.

Anyway. I get my sleeves and CF tubes back tomorrow, then I will set up the location. I'm leaning toward just behind the main spar. It will mean removing some of the rib material. I will take plenty of pictures.
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Old 01-16-2008, 05:05 PM
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Default RE: Nitro 90" (1/7 scale)P-38J Build with mods

Ok thats what I want to see. how you will place the wing tube in the wing.

Thanks
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Old 01-21-2008, 01:24 AM
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Default RE: Nitro 90" (1/7 scale)P-38J Build with mods

Made some more progress on the wing sections. Here are the fiberglass sleeves that a friend made for me. I chose 3/4" OD carbon fiber tubes and am laying it in just behind the main spar.

I made a fixture, out of a piece of brass I had on hand, to hold a step bit for reaching into the wings to drill out the ribs just behind the spar. I used CA to glue the bit in the end of the tube, then slid another piece of smaller diameter aluminum in the other end to keep the chuck from crushing it. Works great.

I tried a very sharp spade bit on the first hole, but it was too rough on the rib, as you can see. The step bit does a great job without cracking the ribs. A 13/16 hole saw would work also if you had an extension for it. I didn't have that tool on hand.

I am gluing the first sections in the outboard wings with Guerrilla glue and when dry, I will install the wing tubes, slide the inboard sleeves and the tubes into the center section, line it all up and then glue the center sleeves in place. I capped the inside end of the sleeves with balsa and CA to prevent any glue from getting in the end as I glued them in the wings. In the center, I went in as far as the back stop for the factory tube. In the outboard sections, I went three bays.

I have made light ply end plates to cap the exposed ends. I plan to use 1/4 X 20 nylon wing bolts and blind nuts to secure the outer sections. These I will access through the gear doors for the retracts. My intension is for the wing to boom, and turbo cover to top, all to be permanent attachments. Everything will be accessed via the gear bay, including servos.
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Old 01-21-2008, 01:37 PM
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Default RE: Nitro 90" (1/7 scale)P-38J Build with mods

Never done this before (on an ARF), but so far, it seems to be going well. I now have the Port side outer panel tube and sleeves in place and glued up. I used Gorilla glue on the inboard section as well, since it worked so well on the other panels and it gives you plenty of time to get everybody lined up. An aluminum wing tube is stretch wrapped (this stays tight where as tape stretches and gets loose) in place to keep the panels straight. Tonight, the other side, then I can start to work on the end plates.
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Old 01-24-2008, 12:34 PM
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Default RE: Nitro 90" (1/7 scale)P-38J Build with mods

More progress on my wing separation. I made plates and plywood inserts (3/16 ply) for the 1/4-20 blind nuts in the outboard sections. These have been glued in place. I first taped around the wing with 2" blue tape. After the epoxy dried, I could sand this flush without damaging the covering. Then I remove the tape and you can see the results. The flap servo was relocated and ply backer added it the new location before the end cap was glued on. I will now drill a small hole for the servo leads and that just leaves the installation of anti-rotation pins. These will be CF rod (male) in the outboard panel, and an aluminum tube (female) in the root.
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Old 01-24-2008, 12:36 PM
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Default RE: Nitro 90" (1/7 scale)P-38J Build with mods

Couple more pictures of the process. As the boom is going to become a permanent part of the center section and add strength to the structure, I will cut the bottom skin away where the gear bay will be to access the new wing bolt (a metal 1/4-20) for the outer panel.
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Old 01-24-2008, 04:24 PM
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Default RE: Nitro 90" (1/7 scale)P-38J Build with mods

Good going,
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Old 01-30-2008, 11:20 PM
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Default RE: Nitro 90" (1/7 scale)P-38J Build with mods

Back to those booms. I gutted them of gear and servo mounting structures, and the OEM 2-56 push rod sleeves, and went to work on installing 'Precision Nyrod' tubes down the sides for tire clearance, and rounding the bottoms.

I am building in the gear doors and will cut them free after the sheeting is done. Double formers are where they will be cut out. They are within 1/2 " of being scale length. I made them long enough to mount the rudder and elevator servos just behind the tire, when retracted, if need be, for balance.

The wing cover may still need to be removable as I don't think I will be able to reach the wing bolt from the gear bay as I had hoped. If this is the case, I may just go back to mounting the servos up on top the wing and under this cover. Hook up and service would be easier anyway.
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Old 01-30-2008, 11:24 PM
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Default RE: Nitro 90" (1/7 scale)P-38J Build with mods

Here you can see the new sleeves (crossed at the back to avoid the sharp bend), some of the former work in the front and for the gear bay, the Robart main gear I selected with it's 1/2" 'Robo Strut', and some of the stringer work.
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Old 01-30-2008, 11:30 PM
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Default RE: Nitro 90" (1/7 scale)P-38J Build with mods

Some more former detail and more of the cut away for the tire to clear. A notch was made in the trailing edge of the wing as well to be pictured later.
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Old 01-31-2008, 11:13 AM
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Default RE: Nitro 90" P-38 (1/7 scale) with 3 piece wing and more

For some reason I thought the booms were glass. Wood is good for modifying. I might consider this at a later date.
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Old 01-31-2008, 12:10 PM
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Default RE: Nitro 90" P-38 (1/7 scale) with 3 piece wing and more


Quote:
ORIGINAL: Edwin

For some reason I thought the booms were glass. Wood is good for modifying. I might consider this at a later date.
Edwin
Yes, this is easier for me being it is wood, and lighter also. I'm shooting for a final weight of no more than 16lbs. A friend has a Yellow P-38 that is only 10" larger, yet weighs more than twice that. I think it will be nice to fly even with all the extra detail.
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Old 01-31-2008, 09:55 PM
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Default RE: Nitro 90" P-38 (1/7 scale) with 3 piece wing and more

Gary, how did you come up with your dimensions for the formers to round out the bottom? I think I will add this detail to mine as well and any info would be appriciated... Also would you mind takeing a picture of the longerons from rear forward so I can see the entire fuse bottom?

Thanks..
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Old 02-01-2008, 12:04 AM
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Default RE: Nitro 90" P-38 (1/7 scale) with 3 piece wing and more

Here are some more pictures. I have patterns of all the formers and I think if I scan then into a PDF, I can email then to anyone that wants to try this. I will also put together a bill of materials for you guys. I'm sheeting tonight, so that is pretty complete now.

I have done a fare amount of scratch building over the years, so this is not that big a deal for me.

As far as the dimensions, it was a combination of going for enough depth to house a more scale tire ( 5 1/8" is 1/7 scale) and getting a more scale look to the bottom. As it turned out, they are very close to scale in hight and shape now except for the front. I cheated a little on that so the change to the cowls wouldn't be too drastic.

The gear doors will be within 1/2" of being scale in length, and the radiator scoops will now sit on the sides of the booms in a more scale position.

I'm going to use Robart aluminum offset gear door hinges.
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Old 02-01-2008, 12:11 AM
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Default RE: Nitro 90" P-38 (1/7 scale) with 3 piece wing and more

Here is a shot or the front. I'll have to take one from the rear looking forward.

I also thought, you will need the locations of the formers from the front back for a proper shape and gear bay location.

I'll try to take some time and put together a small instruction manual for this mod. Give me a couple days for that. I'll always be here to help anyone doing this to there Nitro model. It really turns this thing into something, and it is soooo light.
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Old 02-02-2008, 12:08 AM
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Default RE: Nitro 90" P-38 (1/7 scale) with 3 piece wing and more

Here is some sheeting progress. they are almost done with this phase. I'm working on the last of the sheeting on the front of one of the booms tonight.

I now have the gear bay cut into the port boom, and will make a pattern from it for the other one. Then I will cut the two doors apart and finish the internal structure prior to installing hinges.

I'm looking into Yellow Aircraft gear door actuators.
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Old 02-02-2008, 12:14 AM
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Default RE: Nitro 90" P-38 (1/7 scale) with 3 piece wing and more

More shots of the gear bay. Plenty of room to work in here. For the first time I wet the sheeting pieces and used Gorilla glue and then 6" stretch wrap to hold it in place. Wow, did this work well. No more pins and tape for me.
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Old 02-02-2008, 09:52 AM
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Default RE: Nitro 90" P-38 (1/7 scale) with 3 piece wing and more

Does that cling wrap plastic do a descent job of holding the sheeting on? I would have never thought it could do that very well.
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Old 02-02-2008, 10:29 AM
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Default RE: Nitro 90" P-38 (1/7 scale) with 3 piece wing and more

That is looking awsome Gary...
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Old 02-02-2008, 12:39 PM
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Default RE: Nitro 90" P-38 (1/7 scale) with 3 piece wing and more


Quote:
ORIGINAL: Edwin

Does that cling wrap plastic do a descent job of holding the sheeting on? I would have never thought it could do that very well.
Edwin
Better than anything I have ever tried. It stays tight and you can stretch it so it really puts even pressure on the whole thing and keeps it there. Removal is simply a slice with your exacto and it pops right off with no residue or paint pulling as with tape, and the glue doesn't stick to it.
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Old 02-02-2008, 03:14 PM
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Default RE: Nitro 90" P-38 (1/7 scale) with 3 piece wing and more


Quote:
ORIGINAL: Edwin

Does that cling wrap plastic do a descent job of holding the sheeting on? I would have never thought it could do that very well.
Edwin
One correction in perception. This is not 'cling wrap' like you would use for preserving food. This is 'stretch wrap' in a 6" roll and on a handle, used for binding things together in packaging. It comes in wider rolls, but the 6" is very manageable. It is strong and is made to be stretched for holding power. It can be found at Walmart among other places. I have used it for years for other things and always have some on hand. Thought I would just try it on this.
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Old 02-02-2008, 08:30 PM
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Default RE: Nitro 90" P-38 (1/7 scale) with 3 piece wing and more

Learned something new. Will remember this.
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Old 02-02-2008, 11:43 PM
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Default RE: Nitro 90" P-38 (1/7 scale) with 3 piece wing and more

Here is a picture of the kind of Stretch Wrap roll I used.
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