cannonball200

My Feedback: (36)

John, Good afternoon!!! Have you changed out the springs in the gear? I'm just wondering how good the springs work?

Eddie of OKC

hidaven

Planejaw, where did you get that balancer and do you like it? I have the great planes one and its a PITA!

mobyal

Here it is, w/ the extra adjuster for height on it. It'll hold and balance anyhting you're strong enough to get up there, and the wings are held in a cradle.
It's expensive, but worth every nickle....

mobyal

Oops. Forgot to add that it's the EZ Balancer by Southwest Systems. Don's Hobbies out in KS has them. But the EZ Balancer website lists the dealers.

Tx_RcFlyer

My Feedback: (7)

Gonna get me one of these. Much cheaper than crashing a 1\4 scale when you think about it.

http://www.ezbalancer.com/

MetallicaJunkie

i guess battery size/weight and location have a lot to do with it... i ought to move my rx pack(life 2100) from stock location(far behind cg) all the way up to the front seat.....maybe doing that i can get rid of the weight....... out the 30+ planes i have had through out my RC flying days i have had, my cub is the 3rd or so plane that i have had to add weight to balance.... usually shifting batteries does it for me


would you happen to have a pic of how you strapped in your batts?

Planejaw

My Feedback: (53)

If I remember correctly, when you remove the front seat, you will have slots in the floor panel. I put a long piece of Velcro through that and that allows me to strap the batts in. I'll get some photos of the interior, this weekend.

Planejaw

My Feedback: (53)

Yes, MobyAl has it right. Mine is also the EZbalancer with the extensions to allow you to balance a larger aircraft (so that you can keep the landing gear off of your table).

I found mine on RCU. It is expensive, but well worth it.

Planejaw

My Feedback: (53)

Eddie,

I was one of the first that converted the springs to the #216 O-rings. My first set of springs stretched out after the first few landings, no matter how smoothly I landed. I then used some old bicycle inner-tube as bungee covers and zip-tied the ends to hold them tight. Has worked fine for a couple years now and haven't had to change the O-rings yet.

piperfan59

My Feedback: (13)

You dont need that fancy expensive balancer. All you need to do is buy some cheap scales from Harbor Freight and balance like a real aircraft crew does. They can't lift a full scale aircraft why would you. here is the formula. Just make sure that you scales can handle the total weight delivered to each landing gear point. I have been using this for years with perfect results.



This method is how I go about checking CG on a plane that weighs too much to put on a CG machine or lift.

Have the plane all assembled RTF minus fuel. Find a place where you can put the nose of the plane up against a wall. Take a level and prop up the tail wheel till the fuse is sitting level. Your gonna have to take the hatch off in most cases to set the level on.

Once the plane is sitting level, mark on the ground the two points where the main wheels are with masking tape and draw a line right where the wheels contact the tape. Then make a mark where the center of the tail wheel sits in the same manner. Its gonna be on whatever you propped the tail up with. (I use magazines)
Its also a good time to measure from the wall, how far back the recommended CG is. Save that number for later.

What you are looking for at this point is the distance to each wheel from the tip of the spinner. (which should be touching the wall at this point)
I use a long straightedge to get the distances

Lets say you come up with theses numbers:
LH main - 22 inches
RH main - 22 inches
Tail wheel - 70 inches

Now get a scale and place it under each wheel individually. You will have to re-adjust the other wheels to keep the plane sitting level. Add more magazines.
(If you have three scales you can get the weights at the same time but make sure the plane is level)
Remember to put the hatch on after you level the plane before you weigh each wheel. You gonna wind up with three weights. One for each wheel.

Lets say you come up with these numbers
LH main - 9lbs
RH main - 9lbs
tail wheel - 5lbs

Now its just a simple math problem to find where the CG sits right now on the plane.

Weight x ARM (distance) = Moment
22x9=198
22x9=198
70x5=350

Now add the total of all the moments and the total of all the weights.
Weights 9+9+5 = 23lbs
moments 198+198+350 = 746

Then divide the total moments by the total weights.
746 divided by 23 = 32.43

That number 32.43 is "in inches" how far back from the tip of the spinner to where the plane balances right now.
Compare that to the distance that you measured earlier to the recommended CG location.
If you are off one way or another adjust items then recalculate the weights. The distances (or ARM's) aren't going to change so you already have those numbers.


It may sound confusing and a lot of work but it really only takes about ten minutes to do it.

This is generally how full scale planes are balanced. You cant go lift one of them by your fingers or stick it on a CG machine.

Try it......

ZX11

Great post on W&B. It might still be easier for the small guys to use their fingers for balance. But, I like the explaination on the W&B technique. I have tracked wieght and ARM for full size airpane modifications but left it for the crew chief to calculate. Cool to finally see what all the calculations were doing. Everything was in inches from the nose.

piperfan59

My Feedback: (13)

For the landing gear bungies, the best solution is to get some small diameter bungie cord like those sold by West Marine or other marine supply for use on sale boats or other boats. I tried the local hardware store and got the IDK look. You can purchase it in bulk form from a roll. I got about 3' last time to fabricate my landing gear bungies. The typical O-ring cracks and does not last more than a few landings. You never know when they are going to split and cause the gear to colapse. [>:] The bungie cords that are covered in the in a stretch fabric that covers the fine rubber strands inside. You use simple hog rings to connect to make a loop the correct size. You want tension when installed. I am using 3/16" diameter cord looped to about 1" diameter circle. They don't break. I saw one guy using just CA to connect. I choose a more durable solution with the Hog Rings to bind. They are actually very scale as the full size. You are going to need bungie cord, hog rings and hog ring pliers to do a proper job. Will post some pix of my job. I use 6 per strut for perfect balance of stretch and support. Try it, you like it and you will look cool too.

The Old Skeptic

If you fly all electric as I do, the o-rings will last as long as your plane will without degradation of any kind. The oil residue from glow and/or gas engines is what spells trouble for neoprene. But that should affect the covered strands of rubber used in bungee cord also. You just wouldn't see it as readily as you would with the o-rings.

I have one other comment to make here: If you are using JR821 servos as recommended by the manufacturer and imploy the use of the light-weight plastic servo arms that are supplied with the servo, you will be asking for trouble with a 19+ pound plane as I did the last time. Those arms will crack in time and do in your beautiful H9 (as it did my last one). There is still time if you are using them. I recommend using DuBro heavy duty arms. They will not break and you will be happy that you did that. I know, most of you are doing that already. It's just that I seem to be the last one to hear anything.

hidaven

Also, to add the skeptic.................if your using the recomended 821 servos, make sure you replace the servo arm screws with the longer ones!!! Too many issues with the shorter stock screws.

Planejaw

My Feedback: (53)

I've covered my 216 O-rings with bicycle inner-tube with zip-ties on each end. Though I run gas, I've run the O-rings in one airplane for three years with no splits, degradation, oil fouling or any problems whatsoever. With 2-4 on each strut, you can easily tell if one goes bad, your airplane will list to one side and you'll feel a much softer strut on one side. But again, I've never had to replace any yet. Keep them clean and dry and you won't have any problems.

piperfan59

My Feedback: (13)

I never saw a full scale cub with O-ring bungies. Only the type I have discribed above. If adding scale details this is one you should consider. As for cracking O-rings, you guys are running on luck. I have had Robart gears on my cubs now for 15 years and have never had a O-ring last more than one season of flying. But to each his own. The scale detail with the real bungie style is sweet. I get compliments every were I fly.

MetallicaJunkie

are your bungies exposed?
\

hidaven

Thats kinda personal......

Planejaw

My Feedback: (53)

I've also never seen a full size cub with servo arms sticking out of the wings or cylinder-head/spark plug sticking out the bottom of the cowl! I agree with you Piperfan, there are many ways to improve over the stock springs that come with the airplane. If the bungees/O-rings are covered as they should be, how does anyone know you have real bungee cords and not springs or O-rings? And, in my experience, there is no such thing as luck. If you cover your O-rings and do not let fuel/gasoline/sunlight attack them, there's no reason they should not last more than a season, but that also depends on how much you fly them. You also need to protect the O-rings from being cut by the threads on the bolts you install to attach the O-rings to. I covered my bolts with brass tubing, so the O-rings never come in contact with anything that may cut into them.

I'm building a 1/3 scale BUSA Super Cub and I very well may use the bungee method. Piperfan, do you have any photos of your installation. I think I'd like to give it a try.

cannonball200

My Feedback: (36)

Any body got a good idea on a latch to hold the window up to the wing. We had a simple one on our full scale J-3. Just a piece of bent heavy wire on a small hinge screwed to the wing rib.

Eddie

rslstft

My Feedback: (10)

Eddie,
I just sunk a small magnet (from Radio Shack) in the lower rear corner of the window hatch, re-covered it with some spare covering, and did the same on the underside of the right wing panel. It holds just fine, but of course, I don't fly with it open as I fly mine exclusively off water and don't want any spray getting into the cockpit.

FD av8r

I glued small squares of velcro to the door and wing bottom to keep the window up as desired

Daryll

cannonball200

My Feedback: (36)

Thanks for your ideas on the window holder to the wing... I will not be flying with the window open, just to keep it open on the ground, charging, for looks, etc.

Thanks,
Eddie

Planejaw

My Feedback: (53)

Four good flights on the J-3 with DLE-20. Plenty of power but not so much that it's ridiculous! Lots of one-wheel landings across the runway. This has to be the best aircraft to do that with!!

On one (standard OEM) tank of fuel, I was able to get 4, 10-minute flights, plus have enough left in the tank for the better part of a fifth. Didn't actually fly the fifth, was working on fine-tuning the engine. Had a "miss" that was occurring at mid and high throttle settings that no amount of low or high needle adjusting could eliminate. Going to replace the plug and check the ignition timing before the next flights. Other than that, the DLE-20 is a sweetheart of an engine and just sips gas!!

cannonball200

My Feedback: (36)

John,,,great news on the good flights and the dle 20 ...
I have the dle 20 in my Cub & Waco..
Waco weighs 17 & 1/4# and J-3 weighs 16 & 1/4#..
Good info...my J-3 is ready to maiden.
Thanks,
Eddie