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A4 Skyhawk build

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Old 03-12-2012, 06:10 AM
  #76
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Default RE: A4 Skyhawk build

Alex, I think why the magnet, and he had a small air cylinder mounted in the front to pin door shut didn't work was the air flow as the door tried to close all the way prevented the door from closing far enough to get the magnets close enough to do their job. I'm going to use a larger dia cylinder to increase force, although I'm not sure I'll need it
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Old 03-12-2012, 06:31 AM
  #77
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Default RE: A4 Skyhawk build

I tried a locking cylinder too but wasn't happy I could keep the door closed enough for it to catch which is when I tried the spring/magnet combo. I've moved the geometry around since then so the ram pulls the door a little as well. I suppose I'm about 75% happy it will work. I'm not too worried as my model will be flown in white before I go to lots of effort and expense painting it so theres plenty of time to re do things without ruining the finish. Not that Ali knows it yet but he'll be doing the maiden (hopefully) I'm sure he'll find a weakness if there is one. Think I'll do the pre flight checks though

Let me know how your solution works as I may be copying it if this doesn't pan out.

Cheers, Alex
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Old 03-12-2012, 06:39 AM
  #78
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Default RE: A4 Skyhawk build

Will do, I think I'll probably be using a smaller version on the rear door also as its linkage geometry is wrong also. Pablo said that both doors were coming open inflight. Will let you know how it works out.. Thanks, Steve
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Old 03-14-2012, 02:46 PM
  #79
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Default RE: A4 Skyhawk build

I've spent more hours on this in the last week than I care to count I wouldn't mind but there's not much to show for it...

First of all I repaired the front wing tube guide and tied it into R2 with some decent ply, carbon cloth/tow, epoxy and finally the ply plate glued in with hysol.

The gear doors are just plain layup (because this was the prototype) with no detail or depth to them so I decided on some scale detail as they are large doors that hang down in full view when the gear is out. I built the detail up with plastic, not sure what type. I got it from my local craft shop on its K&S stand. Still a way to go with priming filling and rivet detail but I'm happy thus far.

I still have the rear doors to do, make a release mechanism for the drop tanks, add the lighting, install the servos, add lots of little details and thats just the wings but I'm enjoying working on something thats mine for a change


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Old 03-15-2012, 11:34 AM
  #80
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Default RE: A4 Skyhawk build

Looks great Alex.
I am waiting for my A4 from SM i hope the gear doors are scale detailed from the inside and not just plain.

Best regards
Ziv
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Old 03-16-2012, 01:07 AM
  #81
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Default RE: A4 Skyhawk build

Thanks Ziv, I'm sure yours will have detail installed at the factory. Looking forward to seeing some pictures of your model...

Cheers, Alex
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Old 06-29-2012, 12:53 AM
  #82
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Default RE: A4 Skyhawk build

Hi Guys

Ive had some emails regarding the progress of this model.

Ive been having problems with photos etc.. on this forum so you can follow its progress from here instead:

http://www.rcmf.co.uk/4um/index.php/board,320.0.html

I'll try and upload some more videos to my you tube channel as well, TLJC1

Cheers, Alex
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Old 10-23-2012, 12:45 PM
  #83
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Default RE: A4 Skyhawk build

It's been a while but the A4 is nearly ready for some paint

Phil Noel at Pinnacle Aviation is going to do the paint job so I'm looking forward to him working his magic! Hopefully he'll post his progress here. I've got a few weeks to finish it ready for the paint shop.



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Old 10-23-2012, 02:12 PM
  #84
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Default RE: A4 Skyhawk build

Hi Alex,

Can I have some pics of the internals? fuse + wings?

Thanks,
Ziv
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Old 10-24-2012, 01:10 AM
  #85
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Default RE: A4 Skyhawk build

Hi Ziv

If you need anymore let me know.

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Old 10-24-2012, 05:38 AM
  #86
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Default RE: A4 Skyhawk build

Hi Alex,

Thanks - if you can I need more pics of the interior in the front - I need to see the instalation of the front wheel system and air system.

Thanks,
Ziv
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Old 10-24-2012, 10:13 AM
  #87
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Default RE: A4 Skyhawk build

No worries...what exactly would you like to see with the air system?
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Old 10-24-2012, 11:24 AM
  #88
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Default RE: A4 Skyhawk build

Looks awesome.

Seems that the Douglas company forgot to add the fabric covering on the rudder
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Old 10-24-2012, 12:05 PM
  #89
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Default RE: A4 Skyhawk build

I need to see the install of the auxiliiary air\oil tank and the connection to the steering servo, and just some more pics of the internal.
Also - the location and posture of the fuel cells.
As for the wing gear doors - did you change the geometry? I saw that they do not hold the pressure in the air.

Thanks
Ziv
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Old 10-24-2012, 11:25 PM
  #90
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Default RE: A4 Skyhawk build

Hi Ziv

I'll take some more for you today at some point. Here's a few old photos of the equipment tray layout.

Sorry photos aren't uploading atm I'll try agian later.
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Old 10-25-2012, 10:02 AM
  #91
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Default RE: A4 Skyhawk build

.
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Old 10-25-2012, 12:21 PM
  #92
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Default RE: A4 Skyhawk build

Sonnich,
The external ribs on the A-4 rudder were applied after high frequency, low amplitude "buzz" was encountered during early flight tests with the XA4D-1 Skyhawk. The rudder surface was turned inside-out, resulting in a "tadpole section" which eliminated the problem. Vortex generators on the upper wing surface and a "sugar scoop" tail fairing were also added toreduce buffeting at certain airspeeds. These "fixes" worked and the A4D-2 version was followed by over 2950 A-4 Skyhawks which served multiple countries for their defense requirements for over 60 years.
The A-4 Skyhawk is a great aircraft to model with numerous versions and country color schemes. A-4's forever!

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Old 11-03-2012, 02:20 AM
  #93
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Default RE: A4 Skyhawk build

After a nine month wait, I've finally received my JC180RX! Thanks to Als Hobbies who provided me with excellent customer service throughout. Thanks Al...

Although it was my choice to stick with JC and not take a different turbine I do feel they handled the issues with the 180RX badly from a customer service point of view, luckily having a good dealer took away much of the frustration. I'd probably get the new Jets Munt turbines in the future...

Ive had a really busy week at work so haven't managed to take any more photos Ziv. I'll try and do it on my days off...

Cheers, Alex
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Old 11-03-2012, 01:12 PM
  #94
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Default RE: A4 Skyhawk build

This will certainly be a stunning example of an A-4. Looking forward to seeing more.

I have a Tamjets A-4 that's been flying for almost 5 years and it has been such a great plane to own and fly. I'd love to have a larger one as well. I'd really love it, if SM made a version with operable slats!!! but I appreciate the complexity of the statement when it comes to having something like that functional, strong and reliable. I feel the SM A-4 is just about big enough to make it happen, and not sure if it would be worth the weight but it would "look" stunning...
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Old 11-05-2012, 07:14 AM
  #95
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Default RE: A4 Skyhawk build

Thanks Eddie

Although the hydraulic steering was working well I've encountered a problem. The cylinder attached to the wheel started leaking letting loads of air in to the point where the nose wheel steering would have been lost if it were under load. It needs a new cylinder which Ive asked Li Kai at Skymaster to ship to me. It eventually completely popped apart which is when I found the thread was stripped. I've glued it back together which is only a temporary fix until the new cylinders arrive.

The other issue Ive discovered is the duct is the wrong size for the supplied bypass which has really pis**d me off It requires a fair bit of butchery then some glass work etc... to get it all fitting. The larger SM P200 bypass fits the duct but its so large you can't sensibly squeeze it and still get the turbine and pipe to line up etc...





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Old 11-07-2012, 12:22 PM
  #96
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Default RE: A4 Skyhawk build

I'm in the process of doing the turbine install where nothing fits


The bypass is too small in diameter for the duct. Ive had to modify the duct by cutting loads little flaps into it then adding some carbon toe pre-pregnated with 5 minute epoxy to decrease its diameter. I held a large aluminium bell mouth over the top while it set. It's now at the required diameter in a very rough state. I'll glass it all again and make it look presentable.

The Turbine rails were in the wrong position. They had to be lifted nearly 3/4 of an inch so everything lined up. I'm now left with a dry fit that all lines up and fits together so its onto tidying it all up and doing the final turbine install.

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Old 11-07-2012, 12:46 PM
  #97
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Default RE: A4 Skyhawk build

Oh no, not hydraulic steering. Seeing how hydraulic steering has worked out for the CARF A-4 and Mig-29 I'm very concerned about how ready for prime time hydraulic steering is for any hobby grade setup or anything without a full time A&P mechanic working on it!!

Looks like you are on to a fix with the bypass and engine mount alignment. But how many of these are flying right now with the hydraulic NWS ?

Looking forward to seeing more. Best of luck with the nose gear, I'm sure there is a way out of the issue. What about a custom nose leg steerable strut setup?
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Old 11-07-2012, 01:17 PM
  #98
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Default RE: A4 Skyhawk build

Hi Eddie

Yeah hydraulic NWS lol... I'm hoping the stripped thread on the cylinder was a manufacturing fault and not a consequence of its operation. Those little cylinders have to put up with very high loads. Skymaster have now sent me some more so when they arrive my first job will be disassemble them and re assemble permanently with hysol. Hopefully this wont move the problem on... Luckily its easy to get access to the NWS set up so maintenance wont be to much of an issue. I'm close to getting the model ready for engine runs so it's going to be taken to large expanse of concrete where I'll see how the steering holds up. I know theres a few out there flying, no one has mentioned a problem with the steering yet and there are few youtube videos of the models in action so hopefully it will work (fingers crossed)

Cheers
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Old 11-09-2012, 03:07 AM
  #99
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Default RE: A4 Skyhawk build

I always pressure test my tanks before installing them into the model. The seam on the smallest tank had cracked resulting in a substantial leak when under pressure. Ive re glassed its back side along with the duct.

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Old 11-16-2012, 11:14 AM
  #100
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Default RE: A4 Skyhawk build

Finally finished the turbine installation. Only a few small things to do and it will be ready to maiden. I'm hoping to fly it before it goes to paint later this month.

It's final installed and balanced weight is 35lbs8oz this includes a full CAT.

Cheers

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