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-   -   1/2a Piper J3 (Video) (https://www.rcuniverse.com/forum/1-2-1-8-airplanes-70/1387821-1-2a-piper-j3-video.html)

encan 12-30-2003 06:45 AM

1/2a Piper J3 (Video)
 
Hi everyone

As some of you know i have been messing around with this plane called airboss from herr engineering. I liked the kit so much. Laser cut on them is perfect.

So i decided to try another one over this break and as a cristmas gift i bought me a 1/2 a Piper J3 cub from herr engineering again (http://www2.towerhobbies.com/cgi-bin...?&I=LXN774&P=7). I love the looks of J3's.

But i am in doubt at some points. 1) Kit recommends .049-.061 engine size for its 48 inch wingspan. Is a babe bee or a Golden bee (I think they are the same engines except the tank) going to give enough power to fly this plane. I dont need to do any aerobics. i just need to fly. 2) As far as i know scale planes are harder to fly. Is it really so hard. The first and only (so far) plane i flew was this airboss. I can say that i can fly it. At least i can land it fairly good enough to avoid breaking stuff. but how about a cub as a second plane? 3) How would be the gliding of this plane. If i use a cox engine i wont have throtle control. (actually i dont want throtle control since i dont want to add the complexity of it yet)

I bought the plane already and i will build it over the break. Building is fun. Please help me to decide wheter i want to hang it to the ceiling, or i want to have fun trying to fly it.

Happy Hollidays,
Engin

DICKEYBIRD 12-30-2003 08:09 AM

RE: 1/2a Piper J3
 
I saw matchlessaero fly his Herr Cub with a detuned Tee Dee .049 and it had PLENTY of power. He usually flew it around at 1/2 power most of the time so I'm sure a good Babe Bee would do well. Just make sure you use micro radio gear to keep the weight down.

The plane itself flew very well, no adverse "scale model" traits at all. After all, it is a semi-scale model that has had it's design parameters pushed a little to the good flying side. Just make sure you build it straight, put the CG in the correct spot and don't warp the wing when covering! (It's easy to do on open structure wings.)

Good Luck!:D

MikeSell 12-31-2003 12:13 AM

RE: 1/2a Piper J3
 
Mine was a little underpowered with a Norvel .049. I did cover it with cloth and paint it but it came out at 24 oz. It glides great and is a joy to fly. I bumped it to a .061 and am glad I did. Only flew it a couple of times this year so it only has about 15 hours in the air so far. I fly a clipped wing variant of the same plane all the time. It is just so much more fun at 42" span, no dihedral and ailerons.

BMatthews 12-31-2003 12:47 AM

RE: 1/2a Piper J3
 
Mike, I suspect the weight was your enemy. 24 oz is a bit heavy for that size of model. The Herr J3 is about the same size as the 1/2A Texaco models and while I wouldn't call them a hot aerobatic model such models will fly and climb at a fairly sporty pace provided the weight can be kept under 20 oz.

Encan, if you made it up and covered it with something light (perhaps some of the new light films) and only use clear or no dope, depending on the material, you will have a lovely and lightweight flier that will provide all the slow training that you could wish for. Perhaps go for the smaller tank initially and then switch to the Golden Bee for longer flights. Built to 18 oz there is no reason you can't even learn to do basic loops and a few other tricks. It'll need to dive a bit for speed but that's OK.

And when the engine quits if you have a bit of height you can even learn to thermal soar with it. Just don't let it get downwind at all in the glide. It doesn't take much breeze to totally halt any forward progress with these things. And they don't penetrate the wind well even with the nose down a bit either.

You managed to fly that other model in the videos just fine from what I saw so the Cub will be a piece of relaxing cake that will look fantastic in the air.

encan 01-07-2004 12:47 AM

RE: 1/2a Piper J3
 
1 Attachment(s)
Hi,

I am almost done looks good so far.

I have some questions about weight though. Without covering the wing as in the picture but include everything radio gear engine everything comes 18 oz with a cooking scale. but it is so tail heavy right now. to balance it i roughly have to put 3 oz weight to the front. and that makes 21 oz!!! i put my batary pack as close as to the engine(its right behind the firewall), behind it i put my reciever and then servos. i dont want to add 3 oz dead weight to the plane. any suggestions what could i do??

i have 2 things in my mind. 1) i could use my golden bees tank instead of babe bees plastic tank. But it would still be dead weight.
2) ive used steel wire pushrods going through pipes. and glued the pipes to the fuse. Im thinking those are heavy. but if i go with a thinner wire i am sure it will bend at some point.

Any suggestions??

encan 01-07-2004 09:25 PM

RE: 1/2a Piper J3
 
1 Attachment(s)
Finished but i need to work on some small details. an still have this weight problem.

matchlessaero 01-07-2004 09:40 PM

RE: 1/2a Piper J3
 
Encan, that thing looks great. You have really done a good job on it!

I am surprised that you are having a balance problem as mine balanced with absolutely no lead.....

If you do need to add lead, then go to a bigger battery pack. The weight you add might as well be useful!

Mine on a 1 3/4 oz tank with the detuned .049 actually achieved some 35 min+ flights during good weather/thermal conditions. Completed, it weighed 19 ozs with three mini (not micro) servos and a 270 mah 5 cell batt pack.

Good luck and keep us posted how it goes....

BTW, hand launch it. This airplane does not ROG well, and when you do handlaunch, do it smoothly and level with the ground. Mine prefered to get a little speed under the wings and then it would fly beautifully.

John C 01-07-2004 10:29 PM

RE: 1/2a Piper J3
 
I really hadn't thought about this until reading the above posts, but how many bays does one clip per side to make it a 'Clipped Wing' Cub'? Is this option shown on the plans? Last Clipped Wing Cub I had was a Sig 40 sized kit.

Last question, would an 074 be overkill, or just right for a clipped wing version? I'm presently flying the HOB Spacewalker with the 074.

Thanks :D

BMatthews 01-07-2004 10:59 PM

RE: 1/2a Piper J3
 
John, for an aileron version that stunts like a Cap 20 or Sukoi the 074 would be great. Just be sure to put a funky lookin' sunburst scheme on it....:D

Encan, she sure looks good in the pictures. I'm sure you can iron out the glitches and wind up with a fine model.

What size wire rods did you use? If they are 1/32 then you won't save much over that by switching it out. If they are 1/16 then you can save a bundle off that nose weight by switching to something like pull-pull string cables. The only other thing I wonder about is what did you cover it with? If the material is very heavy then ripping it off and recovering with something like So-Lite or one of the other tissue like plastic coverings would help quite a bit. Remember that one oz in the tail requires that 3 oz in the nose. If those pushrods are 1/16 wire then you can probably save about 1 1/2 of that 3 oz of nose weight. Also are your servos as far forward as you can get them. On one model I did a few years back I had much the same problem as you. Since it had a deep fuselage I mounted the servos high in the cabin area and forward under the leading edge of the wing. The receiver and battery pack then slid under the servos from behind. If your servos are mounted to the rear and they are the larger "standard" sized ones then you can help yourself a lot by redoing that part by going for the smaller 1/2A sized servos such as HS81's and moving them forward as I've described.

Another thought to help cure the heavy pushrod blues assuming you did use the heavy 1/16 wire and that long lengths of bare wire are exposed. You can try to swap out the heavier rods for some 1/32 wire. Where the wire is exposed outside of the tubes you can stiffen it up by backing it up with short lengths of bamboo shishkabob skew material bound to the wire with a few ties of thread that are fixed by dribbling on a little thin CA. Just be sure you leave enough free wire showing that it can move through it's entire motion range without the stiffeners hitting the ends of the tubing.

For next time you want to use rod and tube the idea is to make the tubing as long as you can right up to having a little sub bulkhead at the immediate rear of the servos and as close to the control horns at the tail as you can manage. Exposed lengths of 1/32 wire that are up to 1 1/2 inches long should be fine. It's stiff enough that you won't get any buckling on a slower 1/2A ship such as the J3. The idea is that the wire bound inside the tubing is supported and will not kink or buckle thanks to the support from the tube.

In the end 21 oz is about 2 or 3 oz heavier than I would like to see but in fact even at 21 it's still going to fly fine but the power off thermalling will suffer a little. If that wasn't high on your priority list anyway then don't sweat it.

PS: After looking closer at one of the pics I can see that you already have nice small servos. They aren't as far forward as the COULD be but they aren't bad. About the middle of the wing chord it seems. But I also note that the pushrods DO look quite fat so perhaps there is something to be gained there.

Also I'm assuming that you can fit the battery pack up into the nose so it's quite far foward? If not then that will help a lot. And last of all if you can mount the lead in the front of the cowling just below the crankshaft housing that'll help minimize the amount you need as it'll have more leverage. Another thought would be dummy engine cylinders that are filled with the weight you need. That would be very close to being as far forward as you can go I would think.

If you want to have a go at moving the servos forward and switching to lighter pushrods I have a couple of ideas. One of which is to switch to .045 or .050 carbon fiber rod. Carbon is very stiff and weighs next to nothing in these sizes. Just rough up the ends and epoxy on the hardware you need. I also have an idea for extending the support tubes to put them closer to the servos but that'll take a sketch to show you. If you want to try it then I'll take the time to do the sketch.

Bipe Flyer 01-08-2004 01:30 AM

RE: 1/2a Piper J3
 
Beautiful job!

Your wing loading is about 9oz per sq ft. I wouldn't get worried, you're only 1 oz over the recommended weight. If you are really worried about it, there are a few things ou can do to save some weight. Move your tailwheel forward to the rudder hinge line and use a lighter wheel. In the past I have used a pulley out of a cassette tape. Dubro makes a Micro Tail Wheel which is very light. Replace the pushrods with 1/32 wire with Z bends on each end and a V bend near one end to adjust. It looks like you are using DuBro Super Lite wheels. DuBro Mini Lite wheels are much lighter.

P-51B 01-08-2004 12:34 PM

RE: 1/2a Piper J3
 

ORIGINAL: MikeSell

Mine was a little underpowered with a Norvel .049. I did cover it with cloth and paint it but it came out at 24 oz. It glides great and is a joy to fly. I bumped it to a .061 and am glad I did. Only flew it a couple of times this year so it only has about 15 hours in the air so far. I fly a clipped wing variant of the same plane all the time. It is just so much more fun at 42" span, no dihedral and ailerons.

How difficult was it to modify for ailerons? Seems like there isn't much wood there in looking at these photos.

encan 01-09-2004 12:24 AM

RE: 1/2a Piper J3
 
1 Attachment(s)
Thanks alot.

Mr Bruce,

I have covered it with ultracote. What is the lightest coverin material that is applied just like monocote type covering. Its just much easier to cover with those instead of tissue. Right now i really dont want to remove the covering and use another.

My servos are airtronics micro servos.

my battaries are right behind the firewall and i cant move them further. My reciever is right behind of the battary but i guess i can put them together to the front. Attached the setup.

I have used 1/16 rods. I am thinking to change them and move the servos even more forward. my LHS doenst have so much stuff and i dont think i can find carbon fiber rods in there either. Can i find these in a hardware store or am i gonna need to order them from internet??

do you think removing some balsa (opening some holes) from the rudder and elevator or even backside of the fuse and recovering them would be a good idea??

John C,

plans does not explain clipped wing version. It doesnt even explain making the ailerons. All it shows is the outline for the ailerons.


Thanks for any kind of help
Engin

Rendegade 01-09-2004 01:30 AM

RE: 1/2a Piper J3
 
My assumption would be that for anyone trying to make these modifications, they've no doubt built a few aircraft and know what needs to be done.

And as everyone says, a clipped wing version would only require a bay or two removed from the outboard edges of the wing...

Clipped wing cubs however STILL won't knife edge nicely..

Trust me on this ;)

BMatthews 01-09-2004 02:18 AM

RE: 1/2a Piper J3
 
Carbon rod in the size you would need are only available by mail order. Aerospace Composites comes to mind and I would think there are a few more places that cater to the indoor RC guys and the parkflier guys that use the carbon rod quite a bit for their outline and covering mouse ear models.

I wouldn't recomend stripping the covering YET. Fly it with the nose weight and see how you manage. It will fly and fly well. The glide will be a touch faster than it would have been if the model was lighter but it's not going to fly like a brick by any means.

And please don't forget to wrap a layer of foam rubber around that receiver. My electronics background cringes whenever I see circuitry in the path of vibrations.

Rendegade 01-09-2004 02:52 AM

RE: 1/2a Piper J3
 
Hmm, agreed, why wrap the battery pack in foam and not the rec?

encan 01-09-2004 04:04 AM

RE: 1/2a Piper J3
 
Thanks alot. i will wrap my reciever.

i will fly it on this weekend and most probably i will have some videos.

but before i try i have just one more question about prop. I have a 6x3 black prop, a 6x3 gray one and a 5x3 black. all of them says thimble drome on them. the gray one is havier than the black ones. ive been advised that when the rpm is higher engine has more power. Is it true for sure. if it is then i should go with 5x3.

which prop should i try first??

DICKEYBIRD 01-09-2004 05:51 AM

RE: 1/2a Piper J3
 
encan CF rod is available pretty cheap from Superior Balsa http://www.superiorbalsa.com/ I like the .070" stuff because you can sand one end down slightly and CA it into the little 2-56 threaded brass doohickeys and screw on a nylon mini-clevis. OR, I used to make all my pushrods from 1/8" square balsa with the wire ends attached with a wrapping of thread soaked with CA. Sometimes I had to put a support midway to minimize flexing. I think you'll find it will fly well as is though and don't worry 'bout recovering it.

The 6x3 black will probably end up being your best prop, but for the 1st flights use the 5x3 black. The 5x3 has almost the same static thrust as the 6x3 but is much less load on the engine and will make it far less needle sensitive. The plane may be a little fast with the 5x3 but a little fast is far better than too slow during early flight testing. After you have flown it long enough to be comfortable, try the 6x3 to see if you like the way it flies better. Be careful with the needle and don't get it too lean.

MikeSell 01-09-2004 01:09 PM

RE: 1/2a Piper J3
 
"Clipped wing cubs however STILL won't knife edge nicely.. "

Mine does! Inverted loops, extended inverted flight and Knife edge just no 3D. Herr Cub 36" straight spars, 42" span, Norvel .061, Cox 5.5x4 gray. Still slows to a walk when landing.

encan 01-11-2004 04:41 PM

RE: 1/2a Piper J3
 
I flew it today. and it really flew good.

Yesterday i decided to do something about the weight and i removed those wire pushrods and made a new one out of hard balsa sticks. i guess it was 3/16" square(still havent got used to american measure units:)) it became less tail heavy but i still needed to but 1 and a half ounce lead to the front. total weight right before flyin was 21 and a half ounce.

i used 5x3 prop first. then tried 6x3. i dont know why but i iked 6x3 better.

it was a windy day. forecast said 20 - 30 mhp wind. but i flew any ways(couldnt wait). during the first flight (with 5x3) the plane was all over the place. it was scary too. second and third flights were better. plane was just hanging in the air without any forward speed even with the engine running. last landings were good but i broke that triangle plate right behind the landing gear on the first landing. but not a big deal at all.

it must be the noise of the engine or something else but i feel really relaxed and confortable as soon as the engine stops and theplane starts gliding. its funny. from the begining of the flight i pray for the engine to stop. it glided so smooth and it felt so good as it came closer and closer silently.

over all i am so satisfied and i love this hobby.

Thank you very much for those who helped me here.

PS: i have all the three videos but they are more than 30 mbs. its too much for uploading. i had a demo version of a program which cuts and converts them smaller resolutions. it is expired now so i cant use it and i cant find another program. If anybody know a way to do it i can post the videos.

LoneRanger 01-11-2004 05:01 PM

RE: 1/2a Piper J3
 
3 sugestions- use CF rod for pushrods something about using wood makes me nervous, ditch thoes HEAVY front wheels use the foam versions ya can realy save a BUNCH of Weight by doing this! another way to ditch the need for nose weight is to space out the engine foreward 1/4" can realy make a lot of difference and it may look funny but in the air you'll never notice the difference.

L.R. [8D]

Bipe Flyer 01-11-2004 05:11 PM

RE: 1/2a Piper J3
 
If it's a bit squirrely with the power on then you may have to adjust the thrust angle of the engine.

DICKEYBIRD 01-11-2004 05:17 PM

RE: 1/2a Piper J3
 
FANTASTIC encan!!! :D:D What a feeling, eh? LR's suggestion to space the engine out some is a good one. You can make a spacer behind the engine from 1/4" aluminum and you get the benefit of moving the engine forward plus the weight of the spacer.

Also, the RTF Cox "Star Wars Naboo Fighter" and possibly some other RTF's have a big, heavy steel prop nut & stud that works well to move the CG forward.

The 5x3 added some scary speed, eh? Cubs don't like high speeds! Sorry, I almost got you into trouble with that advice. I just like to go fast on early test flights to prevent stalling. Try reducing the control travel to make it more relaxing to fly. I'll bet you can't wait for a calm day, eh?

Good Job! [8D]

Rendegade 01-11-2004 09:00 PM

RE: 1/2a Piper J3
 

ORIGINAL: MikeSell

"Clipped wing cubs however STILL won't knife edge nicely.. "

Mine does! Inverted loops, extended inverted flight and Knife edge just no 3D. Herr Cub 36" straight spars, 42" span, Norvel .061, Cox 5.5x4 gray. Still slows to a walk when landing.
How? They're the most coupled aeroplane I think I've ever flown!

I could get it do do knife edge, but I was hanging on opposite aileron and a whack of down elevator to do it.

I could feel an outside snap happening if I tried too hard.

This isn't nice knife edge flight.

encan 01-13-2004 12:37 AM

RE: 1/2a Piper J3
 
Here is a short video of it.

please right click and save


http://www.geocities.com/engincansiz/en/cut.zip

Andrew 01-13-2004 08:19 AM

RE: 1/2a Piper J3
 

ORIGINAL: DICKEYBIRD

encan CF rod is available pretty cheap from Superior Balsa http://www.superiorbalsa.com/ I like the .070" stuff because you can sand one end down slightly and CA it into the little 2-56 threaded brass doohickeys and screw on a nylon mini-clevis.
I have found Goodwinds Kites to have a good selection of CF rod and tubing and to be very competitively priced.

http://www.goodwindskites.com/

Andrew


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