Balancing Hobbico Superstar 40 questions. - RC Groups
Shop our Airplanes Products Drone Products Sales
Thread Tools
Aug 14, 2012, 06:47 AM
Registered User
jsf135pal1's Avatar
Discussion

Balancing Hobbico Superstar 40 questions.


Hello all. I am wrapping up the ARF build on the subject trainer and when I go to balance it it is extremely tail heavy. Before I balanced I did my little checklist.
1. Battery and receiver in recommended locations.
2. Wing on.
3. Motor on with muffler
4. Empty fuel tank
5. Took all recommended measurements for CG from leading edge. 3" and 3.5".
6. I used my fingers and placed them in between the CG forward and rear measurements.

My little lead weights tell me I need to add almost 4 ounces of weight to the front of this plane to balance So I'm thinking with a full tank of fuel this thing is going to be a brick.
I tried moving the Rx battery more forward to almost right behind the tank and not much difference at all.
Being that this is an ARF. Is this normal to add that much weight?
Will that much weight affect flight characteristics?
My friend who has been in this hobby for years tells me he sets the CG in all his planes with half a tank of fuel. Is this okay?
Sign up now
to remove ads between posts
Aug 14, 2012, 09:16 AM
WCB
WCB
Registered User
It's not unusual to have to add lead weight. I don't like to but sometimes you have no choice. Try using a Higley heavy prop nut on the engine or try spinner weight. Sometimes by adding 1~2 ozs. out on the end of the prop shaft will do it. A few extra ounces of weight won't be noticeable on a trainer with a lot of wing area. As far as balancing with a 1/2 tank of fuel...that might be ok as long as you never fly below 1/2 tank.
Aug 14, 2012, 10:37 AM
Registered User
Quote:
My friend who has been in this hobby for years tells me he sets the CG in all his planes with half a tank of fuel. Is this okay?
For now, balance with the tank empty. If you balance with the tank half full, when it empties at the end of the flight, the CG can end up behind where you want it to be. If you balance with it empty, you know that at the end of the flight, your CG will be about right. For a trainer, stability is your prime concern, so having a forward CG when the tank is full won't hurt.

As far as weight is concerned, don't sweat too much over that, you've got something like 4.5ft2 of wing area there, so adding 4oz will only bump the wing loading by 0.8oz/ft2 which won't make any difference.

The reason for the nose weight could be anything, from poor choice of wood, a short nose, or simply that you're using a lighter engine than the model was designed for.

Get the CG in the right place using whatever weight you need, it will be fine for a trainer like this.

Don't balance on your fingertips if you can avoid it, you can be quite a bit out as you make adjustments to your finger positions without realising, plus those 1/2" squidgy sausages aren't very accurate. Either make or buy a balancer, its easy to do, and will make your life much easier.

Cheers

Matt
Aug 14, 2012, 04:34 PM
Registered User
I generally move the battery under the fuel tank and maybe even a larger battery. In a worst case scenario, I'll bust out the servo tray and move it forward some more. There are also spinner domes (prop nut type) that can be used. But like was said, 4oz in this trainer is not a show stopper. It will handle it easily. Never balance with your tank fueled up.
Edwin
Aug 14, 2012, 06:41 PM
Registered User
jsf135pal1's Avatar
Thanks for the tips.
Sep 11, 2012, 07:51 PM
I'm a pilot, 100 yrs too late
Thermalin's Avatar
4oz is nothing reallly... Since its an ARF and there's not much you can do besides shift the battery and internal gear around which you can still do... reccommended locations is fine but if it doesnt work... move things around as suggested.

How do you plan to add the weight and where. Is it 4 oz at the very front.. say on the firewall?
Oct 10, 2017, 03:37 PM
Registered User

CG on Hobbico Superstar


I installed an OS 46AX and am using an 11 x 6 Master airscrew GF. The manual gives a CG range of between 71-89 mm. This disturbs me as I am accustomed to seeing the CG as a single point , not a range. In any event I balanced it at 80 which is about mid range. At the field it got up in the and was doing a hands off climb which was somewhat tamed by heavy use of trim. When I got home I checked the CG and it was still 80mm with batt. installed and dry tank. I rechecked the CG and it was good at 80. Before flying the "ail" lined up with the wings and "ele" with the the horiz tail. I decided to put a washer behind the top motor mount screws to see if that would help with the issue. I have yet to test this.
I was curious if other pilots have had similar experiences with this plane and what CG point they decided to use. My intuition says that my issue might suggest that since it loves to climb perhaps I should move the CG a little further back so that it becomes a little more nose heavy. Any thoughts would be very much appreciated.
Oct 10, 2017, 04:14 PM
Registered User
Trained a lot of people on the superstar 40/ tower 40 trainers. We've always balanced with a 2000ma battery under the fuel tank. And balanced on the spar. Servo tray was in the stock location. On other plane designs we moved the servo tray more forward, don't be afraid to rip out and move if you have to. Replacing pushrods is no big deal. A little weight here or there won't matter much. That flat bottom air foil has pretty good lift.
Edwin
Oct 10, 2017, 04:18 PM
Registered User
Just an FYI, when I maiden a students plane, I do a flying cg test. Take it up high, throttle at around 3/4, 45 degree dive with hands off the stick. If the dive tracks unchanged, you're good. If it wants to level off, you're tail heavy. If the dive steepens, nose heavy. This has worked for years for me. An old instructors friend I replaced at the club showed me that about 15 years ago.
Edwin
Oct 11, 2017, 11:26 PM
Registered User
Arceenut's Avatar
Deleted, duplicate post
Oct 11, 2017, 11:27 PM
Registered User
Arceenut's Avatar
Quote:
Originally Posted by cayrick
............................My intuition says that my issue might suggest that since it loves to climb perhaps I should move the CG a little further back so that it becomes a little more nose heavy. Any thoughts would be very much appreciated.
WRONG!!! move the CG (point of balance) FORWARD to make the nose heavier.
Oct 13, 2017, 08:59 PM
Registered User
I had a Tower trainer and it was nose heavy with a BB .46.
Oct 30, 2017, 02:07 PM
Registered User
Quote:
Take it up high, throttle at around 3/4, 45 degree dive with hands off the stick. If the dive tracks unchanged, you're good. If it wants to level off, you're tail heavy. If the dive steepens, nose heavy. This has worked for years for me. An old instructors friend I replaced at the club showed me that about 15 years ago.
Edwin
It has always been my understanding that just the opposite is true. A nose heavy plane will climb in a dive and tuck down if tail heavy in a dive. Thats why trainers are normally shown to be nose heavy so they will self recover if you let go of the sticks.
Oct 30, 2017, 04:06 PM
Registered User
I dont see that happening.
Edwin
Oct 31, 2017, 01:20 PM
Registered User
Well it happens. here you go. Read post #4.

https://www.rcgroups.com/forums/show...-vs-nose-heavy


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Build Log hobbico superstar 40 size wing rebuild and glow to electric conv stinger0518 Glow to Electric Conversions 7 Sep 12, 2012 12:14 AM
Discussion Hobbico Superstar .40 electric conversion torque roll Sport Planes 9 Aug 02, 2012 05:07 PM
Sold Hobbico Superstar 40 Whahoo13x Aircraft - Fuel - Airplanes (FS/W) 0 Aug 02, 2012 12:18 AM
Sold Hobbico Superstar .40 LPU cbh82v Aircraft - Fuel - Airplanes (FS/W) 1 Apr 13, 2012 08:35 PM