Guillows Cub 303 r/c electric 2nd build

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Re: Guillows Cub 303 r/c electric 2nd build

Postby Bill Gaylord » Sun Feb 21, 2016 12:10 am

Yeah, the MPI retracts are on a 190 build. It actually came out a good bit lighter than my non retract version, so hopefully it will fly well.

For the Cub, I don't even bother with the wattmeter. Use a 10 gram outrunner on 2s with GWS 5030 or 5045 prop. If the model is really heavy, then I've found the motor will actually tolerate 3s with a 5030 prop. ESCs used with the combo on 3 cells are the Hobbywing Pentium sold under different names, and the Castle TBird 6. I believe the Exceed will also tolerate 3s, although it derates the BEC with any ESC and could be an issue with 4 sub-micro digital servos. I believe you will still have more power when downsized to a 4530 on 3s, versus the larger 5" prop on 2s. My C150 uses a 10 gram outrunner with 5030 on 3s. More than ample power so it's not flown full throttle, but if I remember correctly at it's weight, it struggled on 2s. For the 24" models, as long as they're under 4oz AUW, they should fly with a 5" prop on 2 cells, where the 4.5" prop works well when lighter. This 21" Sterling Fokker D8 I recently finished has a 4530 on 2 cells, although it may end up with a 5" prop, with the 100 gram AUW.
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Re: Guillows Cub 303 r/c electric 2nd build

Postby davidchoate » Sun Feb 21, 2016 8:45 am

I expected a lower pitch. I tried a 5040 1st 0n My Fairchild, but went up an inch to 6 and down in pitch to 2.75, and It has a noticible increase in pulling or thrust than the smaller high pitch. on a 250 Mah 2s. But like You said i found 4 Oz. or less the magic number on a 24" WS. And I always have a hard time with the micro .032 DuBro pushrods. Getting them just right to get rid of servo stall problems takes Me a while. I got some Sullivan (smallest) thin Gold N' Cable I may try next. Now that I do Pull-Pull on Rudder. Thanx for The info Bill.
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Re: Guillows Cub 303 r/c electric 2nd build

Postby davidchoate » Sun Feb 21, 2016 8:51 am

Oh, I can't wait til You try and Fly that Green Beauty. It looks like a handful. With that flat wing, and tiny Fin ! Make a Video for sure.
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Re: Guillows Cub 303 r/c electric 2nd build

Postby Bill Gaylord » Mon Feb 22, 2016 10:57 pm

One thing I'll keep recommending David is to get some .015" .020" and .025" wire for pushrods. I finished this model with an AUW of 101 grams, with the CG at about 26.5% chord. I'll try it there, not being too far aft, although I generally start a hair further forward. Had I used heavier .032" pushrods, I'd be adding nose ballast, as beyond 27% would be further than I care for. This one will have to go out flying soon, with a video. I figure I'll fly it first, before the Fokker D8 of approximately the same weight but smaller size. It will be interesting to see how the settings work also, with the flat bottom portion of the wing set at 0-0 with the stab, approximately 1.5 degrees of washout, about 2 degrees of downthrust, and a bit less than 2 degrees right thrust. I've read some Cub threads where that incidence setting has worked well, not having the typical ballooning I'm used to with greater positive incidence on these high wingers.

The model rolls very well, using the small hard plastic washers included in the Sterling models hardware packs. They were inserted on either side of each wheel, before epoxying on the aluminum tubing wheel retainers. The axle ends have nicks places on them, which strengthen the glue joints of the tubing retainers. The wheels have aluminum tubing axle inserts, to accommodate the axle wire, which is thinner than the wheel axle hole diameter. The tail feathers have the scale bracing cable, made using Guillows control line string. The end of the string is wiped with CA, which makes it more like a wire, making it easier to insert it through the holes in the tail feathers and fuse bottom.
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Re: Guillows Cub 303 r/c electric 2nd build

Postby davidchoate » Tue Feb 23, 2016 4:25 am

Looks good. I covered a larger model with the Parklite I got from Horizon, and it is much lighter than Monokote. It just had a very thick paper on the adhering side that deceived Me to think it was as thick as Monokote. Wish they would put the weight on the wrapper though. I called off My maiden flight of My Fairchild because that tissue I used that came in the kit is so bad. Bad in that it is si fragile The slightest pressure will cause a tear. I have learned the hard way to be patient. I have to re-cover it. I have no confidence in that covering. I would be better off had I used that tissue they use to stuff in new shoes ! It is in all the newer kits. Thank God I have a good stash of better stuff. I may even microlite it now that I got some practice using it. I know You're Cub will Fly fine, but this Fairchild, if it Flies, will be a huge step for Me. It will be My 1st entirely successful Guillows RC Conversion. I feel I have finally got the formula right, and was very careful in My set up. I can build any kit that tells Me what motor and prop to use. Where to place the servos, and battery and Fly it no problem, but Why I enjoy these RC conversions is I have to plan and figure out all that Myself, and in that way I learn not just how to Fly a Plane, but why it Flies.
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Re: Guillows Cub 303 r/c electric 2nd build

Postby Bill Gaylord » Sat Mar 26, 2016 5:58 pm

Fly with one hand, film with the other, so not the best video. The shaft mounted motor decided to come unglued a bit, although the model landed safely. Nothing a set screw won't fix, although a bit better prop balancing wouldn't hurt. This is the field the B25 will be flown at, when the grass grows taller. The flat wing bottom set level with the stab works well. I generally start out with a few clicks down elevator, as it's easier to pull up a bit and then trim, than to recover a steep climb-stall right after launch, which can easily happen with a bit of headwind. The results are good, in having a model that stays neutrally trimmed. For this model, it actually needed just a mere click of elevator up trim from level, which could probably be cured by removing the down thrust. The model is also balanced at probably a bit under 25% chord, which makes a very stable model. A bit further rearward CG would probably trim the elevator down perfectly level also, although I have no problem with the elevator trimmed upward less than 1/2 mm at it's trailing edge, which is barely even noticeable. The small amount or right prop thrust works well, with no rudder mixing used. Very maneuverable model.

Flight video: https://www.youtube.com/watch?v=-sdYRRa ... e=youtu.be
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Re: Guillows Cub 303 r/c electric 2nd build

Postby Bill Gaylord » Tue Aug 30, 2016 9:35 pm

Had this model out flying again today. It not only does nice loops, but I discovered that if you loop with a bit insufficient speed, it does some of the sharpest snap rolls I've ever seen. Did a number of them. Almost self recovering after diving a bit afterward, with no spin tendency whatsoever. Really good flying model.
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Re: Guillows Cub 303 r/c electric 2nd build

Postby davidchoate » Wed Aug 31, 2016 1:14 am

It looks pretty fast in the video. I have a Horizon Foam Cub Trainer with a 150 2500kv BL, a 5x2.75 prop and a 2s 280mah batt. the ws it 28" and AUW is 105g. Very similar to Yours, But A year or two ago too late. If I had been able to copy this setup sooner I may have been more successful. I had a similar foam Plane for learning to fly and the brushless motors make the difference. One thing I do not like is that they still use An ESC integrated into the receiver. Ares offers a similar setup, but with a seperate ESC. I will not spend $70 or more for a Spektrum Brick with ESC in the Board. I have Been able to keep A build of 24" ws down to 125g's now using the stuff now available. I tried a #03 build 3 yrs ago as well, and the weight was like the same as Your first. Over 300g. With a Parkzone Brushed motor. I look on RC Groups occasionally at the Guillows Convert threads, and the AUWeights some of these people boast I know are impossible, and they never show videos. That thing sounded like a fighter plane too ! I am busy on another project for a trainer to Fly at My RC Club, But have My 4 ch. faircild still on the bench, and My AUW is close to yours and I have the same setup, and so that video gave Me some confidence.
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Re: Guillows Cub 303 r/c electric 2nd build

Postby tictac » Tue Jan 24, 2017 8:48 pm

Bill Gaylord,
Thanks for the great photos and write-up. They are helping me a lot. I am currently attempting this #303 Cub kit and it is my very first balsa kit. I have completed the framework for the wings, tail and part of the fuselage. I will be incorporating some of your suggestions as I go. The problem I have right now is, the order in which to build the fuselage. Below is the order that I think may work, but I would like any input you could offer on this list...

1. Keels and formers are glued up (this part has been done so far)
2. Attach "H" cabin sides (to prevent distortion when doing stringers)
3. Attach all stringers except the ones on lower corners
4. Reinforce "J" gear struts with CF and attach to fuselage
5. bend landing gear and install
6. Glue on lower corner stringers, using basswood
7. Attach "L" reinforcements
8. Install tail servos and push rods (I'n not using ailerons)
9. Glue on all reinforcing pieces in upper cabin
10. Add firewall/motor mount

In particular, I'm unsure at which point the servos, push rods and landing gear are installed. Does my order of procedures look reasonable to you?
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Re: Guillows Cub 303 r/c electric 2nd build

Postby Bill Gaylord » Tue Jan 31, 2017 7:09 pm

Thanks for the comments. What you have looks good. One thing to note is that the servo mounts and locations were worked out and added, before installing the landing gear. I believe the servos were installed after the balsa strut legs were glued in place, but the servo mounting ears were already added to the fuse formers. You can see the tight clearance between the servo arms and the landing gear struts. The CF strut reinforcement worked well. I saw another build after mine, where the guy broke his gear. I had the gear break on an earlier build of this model, and was familiar with the weak area, which is why the CF spars were added to the struts. At the tip of the CF spars, there are nylon servo control horn ends with holes in them, which the LG axle wires run through. The nylon was scuffed with sandpaper, to glue well with epoxy. The nylon control horns were glued to the ends of the CF spars. The LG wire ends are bent and glued into holes in the fuse bottom, where the surrounding balsa was reinforced with thin CA. I had one attempted takeoff where the lot was far too bumpy. I should have aborted and was getting near the grass and lifted up too early. The model slammed down hard on the gear, with no damage. Definitely worth the effort to enhance the LG.

I've never actually itemized assembly steps, in terms of a list. When you fully plan out every detail, before starting a build, you've already have planned out the assembly order. I spend considerable more time planning conversions and scratch builds than I had in the past. Every subject is different, and there are numerous things that will get in the way or paint you in a corner, if not fully thought out. Currently I'm building a Bristol 72 racer with functional retracts. There are a number of critical assembly orders with this subject.
https://www.rcgroups.com/forums/showthr ... 0-scale%29
I probably have over 100 hours in planning, just getting started. It's a type of subject where everything really has to be worked out, before starting.

For the Cub, there were two critical things I ran into. First is the same with any micro, where you may want to mark off and drill the pushrod guide holes in the formers and mount the tail servos, before adding all the stringers. It can be difficult to get in there with a drill, once the stringers are in place. After doing a number of these I can usually mark off a straight path and hit them right on, and never use pushrod sleeving either. Sleeving adds unnecessary weight, where any length of unsupported pushrod can be supported by a small piece of something like a 1/16" x 1/8" strip of balsa glued across the fuse, with guide holes drilled in it. The second is that the upper cabin stringers have to be custom fitted, so that the wing panels mount straight and are not sweeping rearward of forward. With any conversion, plan out gear placement to avoid ballast. With these Guillow's and other similar high wingers, that's usually fairly easy, as they're all similar. It gets trickier when building subjects where you have nothing similar to use as a reference.
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Re: Guillows Cub 303 r/c electric 2nd build

Postby tictac » Tue Jan 31, 2017 9:49 pm

Thank you, Bill. The last few days I have been finding out exactly what you mentioned... plan as you go, well ahead of doing. I'm starting to understand the importance of mods also. Those other cautions you mentioned about reinforcing the LG and doing inside work before stringers make a lot of sense. I will plug away at it.
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