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Hobby King J3 Cub Laser Kit build

Old 03-06-2014, 12:05 PM
  #76  
solentlife
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Sorry you have me confused - I am not sure I understand what you mean.

The stabiliser sits on a flat area at tail end of fuselage ... see post #16

Nigel
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Old 03-06-2014, 12:18 PM
  #77  
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sorry for my explination, i will try again. On the photo you see the rounding of the tail with balsa wood. Where is there room for the stabiliser to put it flat on the tail? Do i make an insision where i will slide it in?

In the manual, you see at the end of finishing the fuselage, 1.12 install the cover tot the tail and smooth it. So this part is the round balsa that i mean. So there is no room tot put the stabiliser flat on the end of the fuselage? This part is got me confused??
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Old 03-06-2014, 01:15 PM
  #78  
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Ok - the wedges that are glued in place to 'round and fair' in tail should actually go on AFTER stabiliser is glued in place ...

See my attached photos ...







Nigel
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Old 03-06-2014, 01:39 PM
  #79  
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These photos are helping me a lot. Thanks. Do you have a photo of installing the rear wheel as well? A million thanks!!
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Old 03-06-2014, 03:38 PM
  #80  
solentlife
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Originally Posted by oosie25 View Post
These photos are helping me a lot. Thanks. Do you have a photo of installing the rear wheel as well? A million thanks!!
The rear wheel is a personal choice ...

For a safer and less stress version for rudder :



The above puts the stress to the fuselage instead of to the rudder hinges.

On this model I chose different but wished later I hadn't ... I mounted the wheel via a wire leg into the rudder itself ... this stresses the rudder hinges ...

Nigel
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Old 08-08-2014, 10:04 AM
  #81  
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Default wing ribs?

Originally Posted by solentlife View Post
Started on the wing ... boy is this a nightmare sorting out the pictures to text ... turns out that text does NOT follow same sequence !!

Second that having used one of the wing spars for fuselage longerons ... meant I had to thin down the longeron to use as spar !!

First - cover flat surface with clear plastic ...



Then start laying out ribs and main spar. The ribs are flat bottom and this helps a lot ...



BEWARE .... there are 3 different ribs in this and they are not too clear about this ... the centre rib is the shorter of all ... This is one rib per wing at centre.
Then comes the next rib that has NO inset into the trailing edge to sheet - this one has me totally confused !!
Then #3 rib and all out to end are ribs with the cut out both sides of trailing edge to allow sheeting.

Once I figure out the rest - will post next !!

Nigel
Hi, I was wondering if you can tell why there are more ribs than there are slots in the spar? I same to have 2 extras for each half. I Understand that those that are different to the bulk go in the centre. Perhaps an extra rib for the outside of the aileron? The other?

Thanks in advance.

Oh, and thanks for this thread, I assembled the fuselage in a couple of evenings, with no dramas, thanks to this post.

Cheers, Dick
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Old 08-08-2014, 02:09 PM
  #82  
road king 97
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Originally Posted by dickw5000 View Post
Hi, I was wondering if you can tell why there are more ribs than there are slots in the spar? I same to have 2 extras for each half. I Understand that those that are different to the bulk go in the centre. Perhaps an extra rib for the outside of the aileron? The other?

Thanks in advance.

Oh, and thanks for this thread, I assembled the fuselage in a couple of evenings, with no dramas, thanks to this post.

Cheers, Dick
Iam guessing after building alot of kits but they most times double up the middle ribs or the very end ones or both. Could be the ail as you said ,sounds like the directions are lacking . I went back and looked at Nigel"s wing and could not see a double ,could have been for the mounting of the servos but not sure. joe
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Old 08-28-2014, 06:05 AM
  #83  
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oh cool you really are good
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Old 02-07-2015, 03:25 PM
  #84  
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Fitted the E-Flight Cub cowl today ..... real nice piece of work.



Just had to ease the bottom corners over the batt hatch hinge tape and firewall ...

Not too bothered about the slight different yellow !

Nigel
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Old 10-11-2015, 04:17 PM
  #85  
Norbert
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Hi,

I just started with my J-3 and really, the instructions are useless.
But no problem, fuselage went together quite fast with some improvisations.
For example I glued stripes onto the upper sides of the bulkeads to get them level with the sides. I left out the second firewall and the parts for the battery department. Later I'll do this with balsa.
Now I'll start the wings to see how it goes onto the fuselage.
At the leading edge and the root it seems to be very unclear.
I want to make it with separated wings for better handling but without dyhedral.

About the drive: I found a 50g motor with about 1200KV (measured) which gives a thrust of 720g with 14A at 10.9V on 3s2200mAh with a 8x4.5 prop.
I think that's fine because at lower amps it seems to be quite efficient.
410g at 6.2A should be enough for flying. Full power is just a bit too much for the motor (gets a bit hot) and is only for emergency.
I'll try to save weight and hope to get it into the air below 600g.
Should be possible as the fuselage is 80% finished and still below 80g.
I want the thing to be as slow and easy as possible, not like the 800g bomber you can see on YT.

So what do you think?

Best regards,
Norbert
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Old 10-11-2015, 05:40 PM
  #86  
solentlife
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Hi Norbert ... I think you will struggle to get her CoG right at such lightweight ...

Nigel
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Old 10-11-2015, 06:27 PM
  #87  
Norbert
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Hi,

I've read about this problem.
In the configuration on the first picture, the COG is at about 115mm from the tailing edge.
This is with 2200mAh just behind the firewall.
I think this equals about 33% from the leading edge (wing is about 172mm deep?).
Then there are motor and prop, the wing should be roughly balanced at the COG and here's the idea I just got:
Cut out the firewall, move the battery 20 or even 30mm into the cowling and add some "cage" from balsa around it. This should solve the COG-Problem.

At the tail it's nearly impossible to save weight by the construction. But with the linkage you can. Thin steel wire of 0.5mm, only supported by small pieces of tube here and there, at the tail just bended into a horn of 0.5mm ply. This will do the job and if it safes only a few gramm at the tail, this is several 10g at the front.

Let's see...

Best regards,
Norbert
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Old 11-10-2015, 07:06 PM
  #88  
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Hi,

Finally I'm ready for takeoff, if the weather wouldn't be so bad. And it's dark when I'm home from work.
Hopefully the weekend gets better.
I'm at 620g including the 3s 2200mAh battery.
I tried to save weight whereever I could.
E.g. I left out some ply parts (like the doubled frame at the leading edge) or replaced them by balsa.
All the battery ply, hatch and so on - left out.
The battery sits with velcro on a slide, which goes out through the firewall into the cowl. I thought I need this due to the COG issue bur the battery sits now just behind the firewall and the COG is still at 50mm from the leading edge.
About the gear I'm a bit proud of, it gives a wonderfull suspension and the weight is nothing.
Same for the tail wheel. It sits in a small tube in the fuselage and is controlled by the rudder by a 0.5mm piano wire. The small piece of plastic just prevents the gear from falling out from the fuselage.
It's just fixed with clear tape, same as the cowl and the balsa plates which hold the aileron servos.

This thing will fly really slow and that's what I wanted it to.

There are more small detail solutions, please just ask.

Best regards,
Norbert
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Old 09-23-2016, 05:17 PM
  #89  
solentlife
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Hi all .... interested to know who is still flying their J3 ?

Mine is still going ... and will get another day out tmrw ... 24 Sept. 2016 ..... not bad considering I started this thread quite a while ago ........ over 3yrs ago

Nigel
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Old 09-26-2016, 07:24 PM
  #90  
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I have owned the e-flight J-3 on floats -goldberg J-3 and Sig 1/3 scale J-3 on 4ft long floats so i had gotten burnt out on them for a while . I have plans for a easy light electrict one that i might build next year . got to take a break once in a while .lol joe
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Old 09-26-2016, 08:04 PM
  #91  
solentlife
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Here she goes ....



Nigel
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Old 03-25-2018, 03:21 AM
  #92  
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After all this time I am slowly working on mine again. I guess the cowl put me off a lot. (it doesn't take much)
I have now fibreglassed it and sanded it and just added a second coat of weave ready to sand once again.
I also made up the undercarriage so progressing slowly. When the cowl is complete I will start the wings.
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Old 03-25-2018, 06:42 AM
  #93  
solentlife
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I have various 3D additions for the cowl which I will post up once I get back home ... I'm in Dubai at present on business.

The best cowl is in fact the E-Flite cowl as that has the engine cylinders / exhaust already moulded in ...

Nigel
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Old 03-25-2018, 08:44 AM
  #94  
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I had heard about the E-Flight one but read it was no longer available. This one has turned out really good now so I am happy.
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Old 03-27-2018, 04:11 PM
  #95  
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I am very happy with how my cowl turned out, but for a scale look I wonder if this one would fit? for a FMS 1100 mm Cub US$8.50. The dummy motor looks great.
Incidentally, this Hobby King kit is now discontinued.



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Old 03-27-2018, 06:33 PM
  #96  
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The Cub and Tiger Moth kits have been revamped by the factory correcting some of the mistakes in these.

Nigel
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Old 03-27-2018, 10:00 PM
  #97  
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Mistakes? Na, that couldn't be....
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Old 01-11-2019, 05:35 AM
  #98  
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After putting it aside for sometime I have just completed the Cub kit over the Christmas break.
Thank you Nigel for sharing your experience with the build it was a huge help.
Its final weigh in is 830g with a 2200 mah Lipo.
Will post a photo when i work out how to do it.
Cheers, Matt.
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