RVM

I have not seen a build thread for the CG Super Chipmunk so I thought I'd start one with my build. It seems to me that it has always been a very popular sport kit so hopefully lots of people can benefit from this.

I built this kit for the first time in 1992, if I remember correctly. I say built, but by "built" I mean mostly built. I finished most of the plane except for the vertical stab fairings, final assembly, covering (I covered the wing only) and equipment installation. I was about 12 or 13 and lost interest and my father sold all of my R/C equipment when he noticed it just sat around and did nothing.

Well, I've gotten back into the hobby and am about to finish my BTE Flyin' King. I was an excellent pilot as a kid (or I think so hehe), so I figure while I'm relearning how to fly on my FK I could start building my Chippy. I won't be in any hurry to finish the plane so if this thread drags on from weeks into months don't be surprised.

My primary goal with this thread is to post my build as I go and to hopefully provide lots of information for future builders of this kit. Of course I am also hoping to receive lots of input and suggestions because I do plan on modifying this plane quite a bit.

My goal with this kit is simple: best performance and reliability possible. To this end, here are my current plans for the kit, based on some input in another thread and research I have done. ANY and ALL critiques and recommendations are not only welcome, but desired!

Preliminary thoughts:
Inverted Saito .91 for the powerplant with a Slimline pitts
JR 9303 for the TX. I was thinking about using JR811 digital servos but was thinking I might be able to use mini servos and save some weight and power drain.
I'm not sure whether I'll use NiCd or NiMH. LiPo and LiOn were not recommended for this application, though I've yet to really see why.
I'm not sure what linkages I'd like to use. Maybe some DuBro ball links, though I'm not sure which. Any better recommendations here?
Pull-pull on the rudder, though not sure which pull-pull set up to use. DuBro again?
I'm going to round out the bottom of the fuselage a bit. My idea was to put some balsa triangle stock on the inner bottom edges and sand everything to a nice rounded shape. My biggest concern was strength. Would I need to reinforce the balsa?
I was going to add about an inch to the length of the rudder.
I don't remember if the elevator will clear the rudder or if the throw is limited by the rudder. I'll find out in the next couple of days.
Replace landing gear blocks with hardwood. Not sure what I'll replace the gear itself with though.
Fiberglass cowl and wheel pants from Fiberglass Specialities.
Replace the bottom ABS wing fairing with a built-up balsa fairing.
Add a Sig Epoxolite fairing on the top of the wing.
2" carbon fiber spinner, or aluminum if I am doing well on weight
Any and all possible lightening to the structure without sacrificing strength. I remember there being an awful lot of areas in my first kit that I thought were overdone, so I'm guessing that hasn't changed.

I would like to keep the AUW to 7lbs or less.

Anyway, that's the list of stuff off the top of my head.



Alright, let's get started!


I received the kit from Tower Hobbies (I wish Horizon had a larger selection... but it's hard to beat some of the great coupons Tower has) Wednesday afternoon. I came home from work on my lunch break to make sure nothing was damaged. The kit box, along with a few other items I'd ordered for my FK, were packaged in a significantly larger box with a good number of airbags for protection. The outside box sustained some damage but the kit box was in perfect shape.



I seem to remember the box from the 90s being white and a bit smaller, though I could be badly mistaken. The paper label with the kit details seems to be precisely the same.

Upon opening the box you can see that the packing is quite good. All the parts are laser cut now too. I remember them being die-cut and I absolutely hated that. The burning doesn't seem bad at all either. Some very light sanding with 600 grit sandpaper should be more than sufficient to get the carbon off.



I don't have any pictures of the parts yet as I haven't yet taken any out of the box. When I go through and sort everything I will post more pictures.

That's it for now; I'll post more tomorrow!

nickj

CG Chipmunk threads do well here. The plane seems to be a favorite of everyone who's ever owned one. It's definitely one of mine. Looking forward to the build, and remember that the secret to a good build thread is pictures. Lots of pictures.

ptmac3

My Feedback: (3)

I had a Chipmunk too. What a great plane. Maybe I'll build another in the not to distant future. I see you've got your inspector checking out the contents. I hope everything was to her/his satisfaction. Good luck with the Chipmunk RVM!

burgh_guy61

My Feedback: (11)

RVM, I look forward to this as i have looked at this kit a few times just never built one. I did have a chippy when i flew control line ohh about 3 decades ago..lol. Just had to comment, it is amazing as soon as you open a box the "inspector" shows up. I know mine just loves the big boxes.

Stripes

My Feedback: (19)

If you could post your photos here with the Universe they will show as thumbnails which is better for all those of us on dialup. A lot of high resolution photos coming from a third source takes forever to load.

RVM

Sure I'll see if I can get that set up. Where would I start looking? Does RCU have a dedicated server for photos or something?




That is the Chief Inspector. You didn't see the Associate Inspector or the two security officers.


I forgot to mention I will also be going with dual aileron servos and possibly mounting the rudder and elevator servos toward the rear of the plane if balance allows.

If my allergies will let up I'll pull everything out of the box tonight and get more pictures. I am exhausted from work so do not think I'll be working on either my FK or my Chippy tonight. If I weren't so busy at work this week I could have had the FK in the air by Sunday too.

I was browsing through the Tower website and didn't find as many pull-pull systems as I expected. How do you guys think this one will work?

ptmac3

My Feedback: (3)

Do you really need one that heavy? It uses 4-40 hardware. Seems like you might be adding additional weight you don't need with that setup. I could be wrong, but I believe that is for giant scale aircraft. Take at look at these too: http://www.shopatron.com/product/pro...161.5186.0.0.0 http://www.centralhobbies.com/contro...ll/tet2204.htm

TexasAirBoss

My Feedback: (22)

I honestly believed I could bring mine in at 6 1/2 lbs. I was wrong. 7lbs. If I had left of the fiberglass wheel pants off and used standard 5/32 wire for the gear, I do believe I could have shaved another 5 oz off the final weight. But what happens is this: The plane starts really lookng good. So you think, Gee, it would be a shame to have such a nice plane and not put the pants on it. And then I realized I had already drilled the gear holes for 3/16, so I used the stock gear. Many people complain about the landing gear on this kit, they say the blocks eventually give way. I think its because the wire is too large. I build alot of 60 size birds, and I have never seen a kit call for 3/16 wire before. I think its too large to flex and absorb the landing shock. I believe the entire shock is transmitted to the blocks . Well, so far, they seem OK, but I did use triangle all around them. And I did hit a 6 inch ant hill with the right main sometime in the first 20 flights.
My incedence was way off. I have slowly raised the trailing edge of the wing. It almost at the correct angle now.
My elevator is a bit sloppier than I would like. I used a double ball bearing servo, but it still has some slop in the output shaft that is transmitted all the way to the elevator. The servo arm doesn't rotate any slop, it moves forward and aft slightly. It would be less noticable if I had moved the control horn on my elevator further away from the elevator's leading edge.
I don't consider my Chipmunk to be a very tight plane. Its not a sloppy pig either, just not the pattern like plane I hear others claim to have.
The thing I do really like about it is this : its honest. You can pull as hard as you like and no snap roll. And it recovers instantly from just about anything at all. You can fly this plane right on the deck, never get higher than 80 feet and just have a ball right there in front of yourself. I fly mostly at an idle with just some power on the up legs. When I power fly, then the elevator seems sloppy, the trim seems to hunt. ( could be that 20 year old Cirrus radio). I'm still trying to fix that.
As with any Goldberg kit, you will find the kit is almost impossible to screw up. But on the other hand, its also almost impossible to make it perfect. The parts just fit so good and no better. And those square edges on the belly just kill the looks.
This kit builds like a beginners kit. And in its day, it was a pretty good performer. But now, I would have to say its a little dated. The constuction is a tad heavy for a 60 aerobat. The performance is tame by todays standards, ( but I like it).
All the ARF guys ask if its an ARF. They seem disappointed that its not.

Stripes

My Feedback: (19)

When you click on the "Post Reply" button and get a text box for your message you will see a small line just below the text box that says, " Click here to upload images and files! "

RVM

hah! Sounds good. I see it now. I'll do that and save the high res for pictures that need lots of detail or something.

Thanks!

RVM

Hmm yeah the 4-40 might be a bit heavy. The 2-56 seems like it might be a better bet.


Any suggestions for the control linkages for the rudder and elevator? Sullivan Gold N Rods maybe? With dual servos for the ailerons I was just thinking a pair of 2-56 rods stuffed into some Robart ball horns might work great. I may use those horns on all the surfaces. Anyone have any experience with them?

ptmac3

My Feedback: (3)

2-56 rods on each aileron servo should be just fine. The smaller pull-pull setup for the rudder is the most responsive and lightest control system for the rudder there is. Gold N Rods are OK, but they have a tendency to change length quite a bit with changes in temperature/seasons. For simple sport flying I like the Sullivan S511 steel rod. You just have to remember to bow them slightly during installation. That takes all the slop out of the control rod. They have little change in length with the weather. One or two clicks of trim. For the absolute lightest control rod you would want to go with something like the kit recommends. A simple pushrod does not touch the fuselage and has no resistance whatsoever. Half it's weight is supported by the servo, the other half by the control horn. You won't find anything else lighter or that moves with less friction. Check out [link=http://www.centralhobbies.com/control_linkage/pushrod2.htm]these babies.[/link]

nickj

That is a gorgeous photo, PilotFighter. Looks like you could just climb in and take off.

RVM

Those CF rods look perfect! I think I'll order some of those. If they are set up for it and can be cut I may use them on the ailerons too. I may try this DEPS for the elevator. It uses 4-40 parts though. Then again I may just stick to the torque rod connecting the elevator halves. I don't remember how precise that was though.

This pushrod setup looks like it would be perfect for all control surfaces on the Chipmunk while saving a lot of weight.

ptmac3

My Feedback: (3)

When it comes to precision and weight saving you will be hard pressed to find something better than what the pattern guys use. I would suggest calling them to discuss with someone what you are doing before you actually lay down your cash. I'm sure you can find something there that will work though. Make sure you know the lengths (pretty close) of the rods you will need. Another package for the inspectors to check out, eh?

RVM

Saving weight via hardware is a big deal, no doubt. This kit is already overbuilt in some ways, and there is only so much lightening you can do with a dremel before you compromise structural strength. Lightweight everything else will have to be used. I think if I can build this plane right and get the right components I can keep the AUW to 6.5lbs.

I'll give them a call this week and see what they think would be best for my application. This isn't a huge plane by any means and they may have some better, even lighter options for this application.

How much torque do you think would be necessary? I was thinking about either using these JR mini servos or these JR micro servos. The mini is a bit faster, but it is a little bit heavier. Those numbers would be a bit better with a 6v rx pack. Either way would be under 5oz. for 5 servos, and I could probably use this JR sub-micro for the throttle for even less weight.

So much has changed in the past 15 years; I have a lot of catching up to do! [sm=drowning.gif]

RVM

The 3/16 already bends a great deal. Don't you think 5/32 would be even worse?

I wonder if there are any better and lighter gear applications for this plane...

By the way, awesome covering job! It's gorgeous!

Gringo Flyer

My Feedback: (18)

I found it a lot cheaper just to make my own pull pull. I went to walmart and bought teflon coated leader wire rated for about 40 lbs it comes in a kit with the crimper and crimps. Then just buy some threaded couplers and drill a small hole in them to thread your wire through. I then connected the threaded couplers to ball links. I did all of mine in 2 56.

The kit I bought cost about 8 dollars and I made 3 pull pull sets with it and still have plenty left over.

After I took that second picture I added heat shrink tubing to the threaded couplers and it gives a very neat appearance.

RVM

I will have to look into that. Seems like a great idea!

Are you running pull-pull on your elevator?

Gringo Flyer

My Feedback: (18)

Yes, I have 3 pull pulls. One on the rudder and then one for each elevator half.

RVM

Do you have any pictures of your elevator hook up? I'd like to see that.

RVM

More pictures.

I really think there is a lot of room for lightening. I figure holes in the ribs fore and aft of the main spar and shear webbing could save a few ounces. Holes all through the fuselage doublers could save a few more ounces. I'll go over the model and see but I think there is probably a good half-pound worth of weight to be saved just by sticking some holes in the plane.

RVM

I'm almost done with my FK, so I'm about to order the engine, servos, receiver, rx battery and wheels for my Chipmunk and I have run into a dilemma.

I was going to order the Saito 1.00, but then I realized that the newish 1.25 is a bored out and reworked 1.00. It weighs about 2 ounces more and delivers A LOT more power. Now, a 1.25 is going to seriously overpower the Chipmunk, of that there is no doubt. However, the 1.25 could prove useful in a lot more different planes than the 1.00, and later down the road might prove a better investment. What do you guys think? I could buy a 1.25 and have a versatile, lightweight engine that will work in other planes if I choose to decommission the Chippy, although it will be severely overpowered, or I could buy a 1.00 that may not work in as many models, but would be a perfect fit with the Chippy.

I have decided to use JR DS3421s for at least the ailerons (dual), and if I can afford it I'm going to put one each on the rudder and elevator.

Think a 1400mah NiCd or NiMH rx battery pack would be enough for a full day of flying (say, 1.5 hours before it needs a charge)? The lighter the better!

Anyone have a recommendation for super lightweight tires?

A fiberglass cowl from Fiberglass Specialities has already been ordered. I may get the wheelpants too but not sure about that yet.

nickj

I'm not a big fan of overpowering airplanes--takes a lot of the fun out of flying. In any case, I tend to buy the engine for the plane I'm putting it in, not some plane I might put it in later.

RVM

I'm thinking something along the same lines as well, but have not made up my mind yet. blargh!