Scale RCM 1/3 Scale Champ Build

[TonyHallo]

Doing a little revamp on the Champ. Removed the fabric on the fuselage to replace the landing gear brackets. The brackets were just too long. See phot of full scale and model below. I bent the right side brackets last year when I stalled during landing. I had a dead stick this year when I decided to try to eliminate the mid range rich condition, bad move. At any rate I have the new brackets installed which moves the pivot point up about 3/4" and will make new landing gear struts that are a little lighter and closer to scale. I have the 4130 tubing on hand and ready to go.

The Champ doesn't have the benefit of the steel center that David's Cub has so the lift forces at the fuselage are transferred through the window posts. These are 3/8" spruce covered with 1/32" plywood on both the inside and out side. I found both front post cracked on the top where the post needs the root rib. I had cracked the bottom of these last on the stalled landing, I was able a mill grooves and epoxy in 1/8" music wire to repair. This has worked well and I am quite sure the upper joints were not cracked last year. To repair the upper connections I made up a drill jig and drilled though the top of the root rib into the posts with 12" long 1/8" drill bit. I threaded 1/8" steel rod with a 6-32 die and epoxied these into the holes.


is landing gear

 

[TonyHallo]

I weighted the fuselage before and after the covering was removed. The total weight of covering and paint was 1.32 pounds, hopefully I can improve here as well. Once the covering was removed you are left with the gummy Ekobond glue. During the build I found that an eraser could be used to remove glue from the fabric. I found an automotive pin strip remover to be an effect tool for removing the glue while not damaging the wood structure.
I also cleaned up the radio wiring with an eye on weight removal. I'm using three FrSky receivers along with a RB10. A FrSky R8PRO is receiver number 1 with a R4 redundant receiver, both of the these will be located above the front seat, Receiver 2 is a single R4 located halfway between the back seat and rudder. I had used Power Box servo wire to connect the receivers to the RB10 originally and the runs were rather long. This wire was replaced with 30 gauge silicon hook up wire from Amazon. This wire is the same gauge as R4 pigtail connector. I have the receivers hooked up for trio mode telemetry however both R4 will have the telemetry turned off since the RB10 does not work with it and will only recognize one receiver. I'm hoping that new firmware will be developed.
Along with the weight reduction theme, the 3/8" spruce vertical members on the fuselage were replaced with 3/8" balsa, this was done one at time with stiffeners screwed along side each member before removal. Some unnecessary wood was removed as well.
Once the new gear is completed I can recover the fuselage. Since Steward Systems is water based it cannot shipped in the winter months, I have the Ekobond on hand so I can cover the fuselage but will need to wait for spring for the top coats.

 

[Stevendavis]

Nice Work! I might have to install some music wire on my Cub as well, great idea.

 

[-Rick-]

Do you find it necessary to use three RX's? I have only ever used two and found I had a good connection.

 

[TonyHallo]

Well I in the past I used a single X8R with some type of Power Expander. The Champ was the first plane where I decided to use a redundant setup. The redundant setup allows for antenna diversity. I did have a few flight where the RSSI was critical when using a M+ receiver for the redundant receiver for the R8PRO, I have since switched it out to a R4 and it is much better. I had previously had the R8PRO mounted under the rear seat and I am thinking the aluminum frame had some effect on it's reception witch switched over to the redundant receiver, the M+ is not a full range receiver. I am now moving it above the front seat in the roof away from the metal. I have got low and critical RSSI alarms on all the FrSky radios that I have used, most of the time it is the same attitude and spot that I suspect it is due antenna position be it in the plane or transmitter, adding more antennas can't hurt. Even with the critical alarms I never lost control, it is nice to now when to turn back!

With the FrSky radio, to me it's like a hobby within the hobby and reasonably priced. R8PRO $39.10, R4 $27.40, RB10 $29.45, for $123.35 I have a double redundant setup. For $21.60 you get a RPM telemetry sensor with 2 temperature inputs, why not add it? My flying buddy uses Futaba R700SB receivers, $169.99 each.

And to summarize, it's more playing around rather than a necessity.

 

[-Rick-]

Well I in the past I used a single X8R with some type of Power Expander. The Champ was the first plane where I decided to use a redundant setup. The redundant setup allows for antenna diversity. I did have a few flight where the RSSI was critical when using a M+ receiver for the redundant receiver for the R8PRO, I have since switched it out to a R4 and it is much better. I had previously had the R8PRO mounted under the rear seat and I am thinking the aluminum frame had some effect on it's reception witch switched over to the redundant receiver, the M+ is not a full range receiver. I am now moving it above the front seat in the roof away from the metal. I have got low and critical RSSI alarms on all the FrSky radios that I have used, most of the time it is the same attitude and spot that I suspect it is due antenna position be it in the plane or transmitter, adding more antennas can't hurt. Even with the critical alarms I never lost control, it is nice to now when to turn back!

With the FrSky radio, to me it's like a hobby within the hobby and reasonably priced. R8PRO $39.10, R4 $27.40, RB10 $29.45, for $123.35 I have a double redundant setup. For $21.60 you get a RPM telemetry sensor with 2 temperature inputs, why not add it? My flying buddy uses Futaba R700SB receivers, $169.99 each.

And to summarize, it's more playing around rather than a necessity.

I agree with your logic. If you had issues with the RSSI I would add a third RX as well. I guess the type of planes I fly I do not have problems with metal and I also fly in a relatively quite environment with no local cell towers.
And yes, with the cost of the FrSky stuff it makes it easy to add exactly what you need (or want). I added a airspeed sensor to my last build just because it was cheap and easy to do. I was surprised at the results of the planes airspeed, a 70cc 3D plane, it never went over 60 mph. It was fun to learn!

 

[BalsaDust]

I have not tried running dual RX yet with my FrSky setup. Most of my RX's are the X4R and X6R with a single R8 Pro I just installed in my 65" Extreme Flight Turbo Duster. Only time I have seen issues with RSSI loss is when I'm setting up my planes. Seems if you keep your radio within 5-6' of the RX it has trouble maintaining. Never a complete loss where I can't move surfaces but quite a few RSSI Critical and RSSI lost alerts.

 

[TonyHallo]

Been working on the new gear struts when I get a chance in between my daughter's bathroom remodel and the holidays. The gear is 3/4" longer and I used .035" wall 4130 tube rather than the .065" wall on the original. Also working to minimize the size of steel parts to save weight. Used my square block ER32 collet holder to machine the flats and and the DRO radius function was used to round the strut ends. Will be utilizing the springs from the original struts as seemed to be just right.

 

[Stevendavis]

Looking at getting a collet set up for my lathe. Looking good so far Tony!

 

[TonyHallo]

I have a Morse 3 taper collet holder that I use, really need a face mounted collet holder so that material can pass thru the spindle.