YELLOW AT-6 TEXAN BUILD THREAD (Full Version)

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samparfitt -> YELLOW AT-6 TEXAN BUILD THREAD (12/19/2007 11:32:31 PM)

introduction:

It's gettin' to be that time of year: building time and to start thinking about Spring!
I've decided to start building the AT-6 first.
I want to start this plane since it's simpler to build than the Yellow's P-40 and P-38: no inner doors and no retractable tail wheel.
I read the instructions and she will build similar to the P-40 & P-38: ie, sheeted wings, horizontal stab, FG fuse and lots of FG parts.

pic 1-6:
The full size plans are included: one of the fuse and one of the wing/tail feathers.
An instruction booklet is also included.
The plans are full size also for building the rudder and elevator with the provided pre-cut balsa.

pic 7/8:
The wing is three piece.
The outer wings presheeted and the inner FG wing will stay attached to the fuse so only each aileron wire will needed to be connected out at the field.
Two or three air tanks will be put in the wing along with the air valve for the main retracts.
No retractable tail wheel so everything can stay in the wing.

pic 9:
The fuse looks pretty clean and I didn't see any pin holes (but there's always a few to fill in after putting on the primer).

pic 10:
Lots of wood and FG parts for the rudder and elevator plus the cockpit tubs and a nice FG canopy frame.

pic 11:
Nice FG gear doors.

pic 12:
Plans say a G-62 would work but I'm using a 3W-75 (especially since I already had it!).
Also a 40 oz tank and Yellow's spinner.
Plan to also add smoke (gotta' have smoke in an AT-6!).




samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/19/2007 11:34:13 PM)

introduction (cont);

pic 1:
A very heavy cast dummy radial from Ziroli.
This plane will need nose weight anyway (another good reason to use a bigger engine!).

pic 2:
A Bob Dively AT-6 cockpit kit, a nice FG removable antenna and a nice FG cowl with mounting bracket so mounting will be internal with no bolts showing on the outside.
A roll of Ziroli 1 oz FG cloth.

pic 3:
Robart main retracts and non-retractable tail wheel plus all the servos needed.

pic 4:
Pre-sheeted horizontal stab.

Stats is 101" WS.
Says should weigh about 27 lbs.
I'm guessing closer to low 30's.



samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/20/2007 5:15:34 PM)

RETRACTS:

pic 1:
I used Robarts instead of Yellows retracts so I needed to modify the retract mount.
The pencil line is all the material that needs removing.
I already had the Robarts from a previous Ziroli AT-6 (balsa heaven!) but I would recommend the Yellows to save on all the work.
The mount needed to be wider and, initially, I was going to remove an equal amount from both sides.
Fortunately, I check the angle of the strut and all the material needs to be removed from the back mount.
The bottom of the rib also had to have some material removed.

pic 2:
Here's after all the material has been removed and the blind nuts are being installed.
I center punched the holes, pilot drilled a 1/16" hole and used a final 11/64" bit to drill the final hole for the bolts.
I used great planes (GPMQ3028) 6-32 X 1/2" socket head screws and Dubro (607) 6-32 blind nuts.
As you can see, round holes had to be made along the front of the FG so the socket head screws could be put in.

pic 3:
More material had to be removed from the back of the mount to allow the strut to close.
I had to cut all the way through this part of the mount but I don't think it'll weaken the mount.
The force is fore and aft and the mount is all very heavy duty 13 ply 7/16" thick ply.
There is room above the mount to epoxy some ply to bridge that open spot.

pic 4/5:
up/down position.

pic 6:
tools needed to modify the retract mounts.



vik -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/20/2007 7:34:32 PM)

Hi Sam

I have YA texan in workshop as well
Just need to finish YT Emil and will be on this big one too
I have ZDZ80 for it [:D]

Will look carefully on your build
Regards
Vik



samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/20/2007 11:34:57 PM)

Post pictures when you have time.


Outer wings:

pic 1/2:
The inner side of the flap well has to be removed and sanded.
Before/after.

pic 3/4:
The outer side of the flap well has rounded corners that have to squared away.
Before/after

pic 5:
I put the 1/64" thick ply in the flap well and used a thin piece of brass to get a line parallel to the right edge of the flap well.
After cutting along the line, the ply will be snug against the side of the flap well.

pic 6:
The ply on the bottom and a 7/16" thick piece of balsa goes against the LE of the flap well.

pic 7:
ply and balsa epoxied into the flap well.
Lots of weights to keep the wing as well as the ply flat.

pic 8/9:
The aileron comes with two cuts into the wing.
We finish cutting along the front to remove the aileron and then finish removing the second cut (which is waste material).
Before/after.

pic 10:
A 7/16" thick piece of balsa is epoxied to the TE of the wing where the aileron goes plus a triangular piece of balsa is epoxied to the edge of the outer flap well.




samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/20/2007 11:38:09 PM)

Outer wings (cont).

pic 1/2:
A 1" thick piece of balsa is epoxied to the outer edge of the aileron.

pic 3:
The LE balsa is epoxied to the aileron and another 1/4" thick triangular piece of balsa is epoxied to the other end of the aileron.



samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/21/2007 4:40:09 PM)

Outer wings (cont)
Sanding the outer wings and ailerons is next.
I tape around all the areas that I will be sanding to prevent damage to the existing balsa sheeting.
Using power tools and even hand tools agressively can do a lot of damage quickly to areas that you don't want to sand.
(power tools allows you to make mistakes much more quickly!).
The LE and TE of the wings need sanding as well as around the flap wells.
Also, the LE of the ailerons need to be sanded to a half circle radius plus sanding all the end blocks that were previously added.

pic 1/2:
Using a radius bit on my table router, I can quickly remove the excess balsa off the LE of the ailerons.
This gives me the basic radius when I begin hand sanding.

pic 3:
A flush cutting saw (at HD) is also good at removing excess wood.
An assortment of paint sticks with different grades of sand paper glued to them make good sanding sticks.

pic 4/5:
Ridged at HD makes a nice oscillating sander that also comes with an oscillating belt sander.
Also good for quickly removing waste material.
Different hand orbital sanders are also good for this.

pic 6/7:
I manually used a long drill bit to put a hole down the ends of the outer wings to the aileron servo tray so I can, later, add navigation lights.
Some compressed air does a good job of removing all those little white balls from the hole and wing.

pic 8:
The LE sanding done.

pic 9:
Ailerons sanded as well as the flap well areas.

All this sanding kicks up a lot of dust.
I'm presently building the plane in the warm basement but go to the detached shop for any serious sanding to keep all that dust outside.
Some small planes (cutting type!) are also good for removing bulk material without creating any dust.



samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/21/2007 11:05:30 PM)

outer wings (cont)

pic 1:
Some 1/64" thick scrap ply epoxied to the end of the wings so the wing tips will be secure when they are epoxied on.
Holes put in the ply to match the wing tips.

pic 2:
Wing tips epoxied on (I used Zap-a-Dap).
Strung some radio shack #22 gauge flexible wire for the nav lights.

pic 3:
CA'ed the triangular stock to the TE of the wing where the ailerons are attached.

pic 4/5:
Flaps and ailerons re-sanded so everything fits in the wing.

pic 6:
I used some Evercoat Easy Sand (2 part mix) to smooth any problem areas before glassing.





samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/22/2007 2:23:06 AM)

outer wings (cont)
Tonight, I got one more thing done.

pic 1:
I used Robarts large (grey) hinges on the ailerons and small (black) hinges on the flaps.
The flaps are too thin for the larger hinges.
I made 'V' cuts so the hinge pin will be at the center of the radius of the ailerons LE.

pic 2:
Aileron dry fitted.

pic 3:
Flaps dry fitted.

pic 4:
Flap and aileron deployed.
Four hinges in each movable surface.



theradioflyer -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/22/2007 2:33:25 AM)

Very nice build thread, I'll be watching this one[8D]

Thanks and God Bless!

Jay



DLEVETT -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/22/2007 3:22:29 AM)

Nice thread! I,m building a CMP AT-6 1/6th scale at the moment but would love to get a 1/5th Yellow kit in the future.
Keep up the good work.

thx Dave



samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/23/2007 12:53:08 AM)

Thanks for the complements.

Outer wings (cont).
All the linkages for movable surfaces are internal except the ailerons so I decided to also make those hidden.
The main facts are the servo arm will move 180 degrees from pointing full down to pointing full up.
At exactly 90 degree from full up the servo points directly back towards the ailerons (this is neutral).
When the servo arm moves up, the aileron will move the opposite way and vise versa.
Think of this the same way as a door in your house: drill a hole in the end by the hinges and put a dowel in the hole.
As you move the dowel one way, the door will move the opposite way.
We need the sullivan rod because the length will change from the ball socket on the servo arm to the aileron: this yellow rod will slide along the inside of the black tube.
I can't take credit for this since I stole the idea from my friend Gary Webb (we seldom have a completely new idea on our own!).

pic 1/2:
Parts needed.
HS-645 servo: 133 oz at 6v.
Sullivan #517 gold-n-rod.
The yellow rod is 2 3/4" long: the black tube is 3" long ( 1 1/8" sticking out the back of the aileron).
Dubro #861 4-40 swivel ball links.
Two 'L' servo mount brackets (available from Yellow or BVM, or make your own).
Two hard wood mounts: front ones thickness varies from 3/8" to 7/16" due to taper of wing and back one is 1/2" thick.

pic 3:
Hole made in TE of wing for the black tube to enter the wing.

pic 4:
All foam removed down to the top of the wing.
I used a sharp knife to outline the perimeter of the foam and then used a paint stick to remove the foam so to not damage the top wing sheeting.

pic 5:
Where the hard wood mounts will be epoxied to the top wing sheeting.

pic 6:
Servo, 'L' bracket, wood mounts, ball socket and yellow rod assembly.

pic 7/8:
Assembly in the servo well.
This is all below the servo cover.

pic 9/10:
Completed with the following throws:
Up: one aileron gets 7/8" throw and the other gets 3/4"
down: one aileron gets 5/8" and the other gets 1/2"
This is less than the recommended 1" throw in the manual but, in the past, I don't ever remember using what the manuals say!
These ailerons also have a lot of surface area.
I will also be putting a hardmount on the surface of the ailerons for future use, in case there are any problems with this.
This way, no future painting will needed to be done to the aileron: just mounting a control horn and putting a slit into the servo cover.







samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/23/2007 8:56:24 PM)

Outer wings connected to inner wing.
Each side gets two aluminum bars, each bar is sandwiched between two pieces of thick balsa.

pic 1:
Three round holes are ground out on the bottom of the inner wing so the hex head bolts can be tightened to hold the outer wings to the inner wing.
I drilled out access to all three holes on each bracket but only one is used.
I did this for future use in case I strip one of the threaded holes in the bracket.

pic 2:
An 1/8" ply is CA'ed to one end of the bar (side with holes).
The balsa has to be sanded to fit in the outer wing slots.

pic 3:
The ply is smaller than the slot so the outer wing can be adjusted to fit the inner wing.

pic 4:
Dry fit of finished parts.
I labeled all the parts to insure I don't get them put upside down or back wards.

pic 5:
I figure it's easier to cut the 1/64" ply that will fit on the inside of the outer wings before epoxying the aluminum bars in.

pic 6/7/8/9:
I epoxied one outer wing at a time and did it on end so I could see that all sides are even and flush to each other.
I masked the inner wing so the epoxy wouldn't stick to it.
I then mixed up lots of epoxy and another batch with white micro-balls.
The clear epoxy was used to coat the inner surfaces of the outer wing pocket and all sides of the aluminum bar/ply and two balsa pieces.
I sandwiched the three pieces before putting it in the outer wing pocket.
I also put the white epoxy in the aluminum holes before putting the last balsa piece on the aluminum bar.
I then shoved the sandwiched bar into the outer wing pocket, wiped off the excess epoxy that flowed out and then also masked the end of the outer wing around the bar so no epoxy will run down to the inner wing.

pic 10/11/12:
I then tighted the hex bolts on the inner wing to hold the aluminum bars in place and then I checked all sides to make sure all sides are even and flush.





samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/23/2007 8:57:41 PM)

Here's the Sig micro-balls that I used:




samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/24/2007 2:50:07 PM)

Outer wings connected to the inner wing (cont)

pic 1/2/3/4:
Here's the other outer wing epoxied and set up to the inner wing.
I'm glad that I put double masking tape on: one set on the inner wing and one set on the outer wing. Even with this I had a few small drops go onto the inner wing on the first 'glue-up'. I used a razor saw along the divide between the two wings to break the bond.
There's little time to get everything set up before the epoxy (30 minute) starts to harden: especially when you consider putting epoxy in two pockets, both sides of six pieces of balsa and aluminum bar, filling in the bar holes with mico-balls, putting masking tape on, putting everything together, tightening the two hex nuts and checking alignment and flush fit!
In the dry fit, I put the center wing on a level surface and connect the outer wing to it to insure proper dihedral. The dry fit is stiff enough to hold the wings together so I can then put the wing on end and check for overall fit. I use this eye-ball check and then dismantle everything, label all parts for direction/orientation, and then start the re-assembly with the epoxy.
One thing I forgot to mention is that I had to sand the surfaces on the two outer balsa pieces so everything would fit into the outer wing pocket.
I also sanded a small bevel edge on the inside corners of all pieces to they would go into the pockets without 'catching' on the foam in the wing.

pic 5:
Putting the wing 'on end' always gives you a good perspective at how large the plane is!
With a 101" WS, I had to move the bottom of the wing out about 4' from the wall so it would sit upright.



samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/24/2007 9:22:30 PM)

Elevators

pic 1/2:
Here's all the parts for assembling the elevators.
Every thing is labeled and baged.
The balsa sheet is the template and the half ribs/etc are CA'ed to the balsa sheet.

pic 3:
Top side CA'ed.

pic 4:
Bottom side CA'ed.

pic 5:
Both sides completed.
Still lots of work to do with the end blocks and the control horn that comes in the kit.




samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/24/2007 9:24:40 PM)

It's Christmas Eve: Have a Merry Christmas.
May all your presents be large and oblong!

http://ecard.ashland.edu/index.php?ecardYear=2004adm



mobyal -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/25/2007 12:12:28 AM)

Sam --
Your usual great work on display again. I can't build to your lwevel, but do learn a lot bt following you along...
Merry Christmas to you and yours.
Al



Baldeagle -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/25/2007 2:15:52 AM)

Looks great Sam and a good Christmas to you and yours. Rich



samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/27/2007 11:01:20 PM)

outer wings (cont)

pic 1/2:
1/64" ply epoxied to inner rib of outer wings.
Sanded and ready for glassing.
The inner wing had holes in the rib so I put them on the 1/64" ply without thinking about it and they really aren't needed (save the aileron/nag lights wire hole).

----------
Dummy Radial:
pic 3:
Since I had to go to the cold shop to cut one inch square ply for the aileron/inner flap control horns, I also cut some 1/8" thick ply to re-inforce the cast dummy radial.

----------
outer wings (cont)

pic 4:
After cutting a recessed hole, I epoxied in some hard mounts in the ailerons as backup for the internal servo control mechanism.

-----------
Center wing (cont)

pic 5:
Center flap hinges: same as with the outer flaps.
One inch square ply epoxied to a recessed hole cut on the inside of the flap.

pic 6:
A Robart 1 1/4" long control horn screwed to the center flap hard mount.

pic 7:
Holes cut in the FG center wing for the center flap control horn movement.

pic 8:
Center flap dry fitted to the center wing (top view).

pic 9:
Flap in the down position.

pic 10:
bottom view of center wing with flap dry fitted.
The control horn will not be seen from the bottom.
The two outer flaps will be connected to the inner flap via some tabs.




samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/29/2007 4:00:48 AM)

Center wing (cont)

pic 1:
Air valve/servo tray cut out from 1/8" thick ply from template on the plans.

--------------
FG fuse.

pic 2:
Cut out the elevator/rudder servo tray (dry fitted) from 1/4" thick ply from template on the plans.
I went with 1/4" over 1/8" to insure no flexing of the tray since there will be a total of about 420 oz torque applied from the three servos.

----------------
Tail feathers

pic 3:
Rudder pre-cut parts CA'ed together.
Also CA'ed the balsa hinge re-inforcement blocks in the rudder and elevators.



samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/30/2007 6:17:49 PM)

Center wing (cont)

pic 1:
Parts to hold the front of the wing to the fuse.
The metal dowel and dowel cover plates.

pic 2:
A fuzzy picture of the inside of the center rib.
The recess in the rib was pre-cut at the factory but a 1/2" hole needs to be drilled out of the FG LE.

pic 3:
I put the center wing on the fuse and marked the center where the dowel will go into the FG fuse and drill out a 1/2" hole.
Some sanding was necessary to get the dry fit of the center wing's dowel to slide into the fuses hole since the center wing goes into the fuse's wing saddle at a slight angle.

pic 4/5:
After putting the metal dowel in the center rib's slot, I epoxied one side with the cover plates and then the other side.

pic 6:
Front Dowel complete.

pic 7/8:
With the center wing put on the fuse, I marked the area where the flap's robart control horn needs room to move through the fuses mounting plate. I cut out about an inch by 1 1/2" opening for the control horn to move freely.

------------
FG fuse (cont)

pic 9:
I cut some triangular shaped servo tray mounts from hard maple.
I drilled holes in the back to help secure them to the FG fuse.
The servo tray will be screwed to these mounts.

------------
outer wings (cont)

pic 10/11:
1/64" thick ply supplied in the kit to line the aileron servo wells using epoxy.

------------
FG fuse:

pic 12:
Mixed up a large batch of epoxied and dumped it around the fire wall and the FG fuse to give it extra strength.
While the epoxy was still wet, I also used some heavy duty auto fiber glass and laid it into the wet epoxy.





ROGER RUSSELL -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/30/2007 7:45:06 PM)


Looking great.



samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/31/2007 12:48:32 AM)

Wing to fuse.

pic 1:
Re-inforcement plates to insure the front dowel doesn't move.
The large one came in the kit, the small one was cut from 1/8" ply.

pic 2:
The two plates epoxied into the 2nd former in the FG fuse.
I used some 1/2" round bar stock to align the hole while the epoxy dried.

pic 3:
Wing to fuse aligned and taped down with masking tape.

pic 4:
Checking dimensions from rear back of fuse (front of back wheel well hole) to outside corner of aileron: 55 15/16" to both sides.

pic 5:
Drilled a 1/16" pilot hole then enlarged with a 1/8" bit then drilled out for tapping with a 5/16X18 tap.

pic 6/7/8:
She's on her feet for the first time.
With that stubby nose, it easy to see this baby's going to need some lead up front!

pic 9/10/11:
A good tight fit between the fuse and center wing.

pic 12:
Joe the pilot trainer came by to check her out!



samparfitt -> RE: YELLOW AT-6 TEXAN BUILD THREAD (12/31/2007 12:52:32 AM)

Roger:
the dummy radial is from Ziroli.



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