Posts: 1866
Joined: 9/1/2002 From: West Chester, OH, USA Status: offline
Hey, being retired, I'm just enjoying my hobbies. After 38 years of work, I plan on having a good time. I told my kids: If you ever find me in a rocker, watching TV, just shoot me and put me out of my misery! Today is a very happy day for me: not because I turned 62 but because social security starts today...more planes: just what I need!
Rich10: I like to use a door as an analogy on how the internal linkage works. A door in your house is the aileron, the door hinges are attached to the jam. Drill a hole in the end of the door by the hinges and put a dowel in the hole. When you hold the dowel on the end and move the dowel one way, the door will go the opposite way: and vise versa. Your hand is the ball/socket on the end of the servo arm which is your arm. The yellow insert must be able to slide in the black tube since the distance varies from the hinges to the ball joint connection. The servo arm is at neutral when it is straight back facing the center of the aileron. Servo arm movement down moves the aileron up and vise versa. ----------------
Outer wings (cont) I forgot to glass the bottom of the wing so I had to take all the servos out, remove the flaps and ailerons and remove all those set screws in the hinge pockets so the finishing resin doesn't hose them up. I should have done the glassing earlier.
pic 1: I used Ziroli's 1.0 oz FG cloth that I believe still sells for a reasonable price of 10 yds for 24 bucks.
pic 2: Finishing resin applied.
pic 3: Tools used: Zap finishing resin, auto's yellow bondo applicator, lots of 2" square paper towels, dedicated scissors for FG cutting, alcohol (non-drinking! ). Oh yes, latex gloves and old cloths.
< Message edited by samparfitt -- 3/5/2008 2:39:15 PM >
Posts: 21
Joined: 6/26/2007 From: , CT, USA Status: offline
Thanks Sam for taking the time to explain that for me. Having hidden control rods is something I have wanted on my Z- P-51 that is being plated at Metalmorphous but didn’t see a way to do it that was'nt complicated. Your method looks great and I would like to do this on my plane. I have just 2 more questions if you don’t mind. Am I right to assume that the black plastic tube is bonded to the aileron and have you used this method on another plane with success, I have read that some planes with hidden linkage have had crashed due to flutter. Any input on this would be greatly appreciated.
Posts: 1866
Joined: 9/1/2002 From: West Chester, OH, USA Status: offline
Rich10. The black tubing is epoxied to the aileron. Flutter occurs when there's slop in the mechanical set up, hinges and/or linkages, or not enough power (torque): assuming the non-moving surface is not flexing. I also drilled and tapped the ball link screw to the servo arm to insure no slop (also less likely to vibrate loose). Whenever possible, always use ball/socket 4/40 set ups. Bend wires are OK on small planes but should never be used on IMAA legal warbirds. I don't like to use clevises either but I had to use a 4/40 clevis on the outer flaps due to space but I insured that there was no slop in the hole drilled and the clevis pin was snug in the hole. Also, flaps don't get used nearly as much as the other moving surfaces. Use high torque servos on the ailerons to prevent flutter. I'm using HS-645's with 133 oz at 6volts. Hinges should be like the robart's large pin hinges or the nice scale hinges made from wire and G-10 material that some modelers use. Safety and possible lost of thousands of dollars should always warrent the use of sturdy mechanical fasteners and high torque servos. I stole this idea from Gary Webb (gary9648) and he's been using this method longer than me so you can also email him. I like this method as it uses the existing servo well, it's simple, all parts needed are already in your parts box and you can always switch to the conventional external linkage very easily by putting a hard mount in the aileron while building the plane. I've added a few more comments/pictures below. ----------------
pic 1: I switched from a 3/4" servo arm to a 1 1/4" servo arm. The longer arm put the ball/socket right next to the end of the black tubing and resulted in about an extra 1/8" throw. Maximum throw will be obtained by having the ball socket as close as possible to the end of the black tubing. The arm movement was reduced from 100% to 50/54% so the end of the servo arm just touches the inside top/bottom wing sheeting.
pic 2: Also, to get maximum arm movement, use dubro's #861 versus #900 (heavy duty). #861 (right in the picture) has a narrower head so a little extra throw is possible. Both are 4/40 linkages.
pic 3: Also, do not use the spacer when attaching the socket to the end of the servo arm. There's not a lot of room in the servo well for the spacer and you don't need that kind of 'non-parallel' movement in relation to the servo arm.
pic 4/5/6: Servo mounting blocks screwed onto the servo 'L' angle brackets. Since the front mounting block is only 1/4" thick, I CA'ed some scrap blue plastic to the top of the 'L' angle bracket: This raised the head of the mounting screw so it won't go through the top of the wing sheeting. I could have cut the heads shorter but, thinking of the future, I don't want any mistakes of replacing the wrong screws and damaging the top of the wing. Again, I used all socket head screws to prevent any excess pressure on the wing sheeting when putting in the screws.
pic 7/8: Both servos epoxied in the servo well with everything attached, including turning on the transmitter/receiver, to insure everything is aligned and that the ailerons are at neutral. Also, insure your trim tab is at neutral.
< Message edited by samparfitt -- 3/6/2008 6:40:29 PM >
Posts: 21
Joined: 6/26/2007 From: , CT, USA Status: offline
Thank you Sam, your videos confirmed how I thought they would operate. They look perfect and more than enough travel for a scale warbird. I look forward to see more of your work.
Posts: 1866
Joined: 9/1/2002 From: West Chester, OH, USA Status: offline
pic 1: I laid the Yellow P-38 outer wing over the Yellow AT-6 outer wing. About the same wing span but big difference in wing area. With two engines instead of one, this is one plane that will bite ya' if you don't keep ahead of it.
--------------- Outer wing (cont)
pic 2/3: Flaps, ailerons and all servos, plus covers, all back together again. One last test to make sure everything still works.
------------------ Engine (cont)
pic 4: Removing the screw that holds the butterfly to the shaft on the choke assembly, I used the edge of a cut off disk to gently grind away the knurled end so I could remove the choke arm with a center punch.
pic 5/6: The double linkage system was flexing on the long screw that holds the entire assembly together so I had to make an 'L' bracket that stabalizes the other end of the linkage to the fire wall. After putting the choke assembly back on the carb, I connected the double linkage system to the throttle and choke. Longer 2/56 rod was needed plus moving the choke set screw 180 degrees to the other side where there is also an existing tapped hole. This set screw movement was needed since the throttle/choke arms are very close to each other and the two set screws were interfering with each other. Nice that both throttle/choke arms have brass centers with white nylon covering them: brass has the unusual characteristic (as well as nylon) of resisting screws from becoming loose as is not the case with ferrous metals.
pic 7: top view of linkage.
pic 8: The throttle (top) and choke (bottom) connected to the sullivan gold-n-rod via dubros #860 2/56 ball/socket sets. The more difficult right side is done: I'll start on the left side, tomorrow morning.
< Message edited by samparfitt -- 3/7/2008 2:14:38 AM >
Posts: 1866
Joined: 9/1/2002 From: West Chester, OH, USA Status: offline
Tail feathers (cont)
pic 1: Need to get the nav lights set up before adding the vertical fins. Hole drilled in the nav lights of the vertical fins for the LED's. Three battery pack set up for LED's. Radio shack 22 gauge flexible wire twisted together, which will be the 'running' wires from the center wing and down each boom. Radio shack white LED's (276-320) and LED holders (276-079).
pic 2: Holes drilled in the top, back of each boom for the 'running' wires.
pic 3: 'Running' wires routed through the booms.
pic 4/5: Some old servo extension wire used as 'LED wire extensions' and soldered to each white LED. Some tweezers used as a 'heat sink' to protect the LED's. Shrink tubing to cover exposed wires.
pic 6/7: LED's 'wire extensions' wires soldered to the 'running' wires. The thinner extension wires used to give flexibility when inserting the LED's as the 'running' wire is too stiff. White LED's tested. (nav lights go on the outside of each vertical fin) The balsa main vertical fin supports all ready. --------------- Vertical fins.
pic 8: One part at a time is applied to insure all stays aligned. The bottom FG vertical fins are zap-a-dap'ed to the bottom of the booms. The booms have recessed areas for the fin so alignment is pretty easy. Some masking tape will hold the parts together until the glue dries.
Posts: 1866
Joined: 9/1/2002 From: West Chester, OH, USA Status: offline
Tail Feathers (cont)
pic 1: With the bottom vertical fin previously glued to the boom, we can next zap-a-dap only the bottom half of the balsa vertical fin support to the bottom vertical fin. The key to the correct placement was just having the cutout of the counter weight in the balsa align with the cutout of the counter weight in the bottom of the fin. I put lots of zap-a-dap on the inside of the bottom of the vertical fin but I thinly buttered the edges of the balsa vertical support using a popcicle stick. Since the vertical support is put in from the top, only a thin layer of glue can be on it to get it through the boom hole. Masking tape holds everything in place until dry.
pic 2/3: I dry fitted the top vertical fin to the boom to insure that the balsa counter weight cutout aligns correctly with the top vertical fin counter weight cutout.
pic 4: Rudders were finished up last summer which was explained in a previous post. The balsa vertical fin supports were also explained in a previous post from last summer.
< Message edited by samparfitt -- 3/8/2008 2:39:09 AM >
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RE: Yellow P-38 build thread - 
