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Old Aug 26, 2010, 04:37 PM
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Si Goodchild's Avatar
Lincolnshire, UK
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Top Gun F18 Build and Mods Thread

Guys,

Thought you might be interested in my latest project. It's a Top Gun F18 which is distributed by CML here in the UK. Whilst I liked the look of this jet a lot, I was determined to upgrade the weak standard 70mm fan unit and improve the duct geometry. The ducting is actually quite smooth and progressive and the exit area is already correct at 85% of FSA, however the intake area was a huge 210% FSA which I knew would kill the top speed.

I've therefore opted for a Lander 70mm 800W fan unit which is designed to run with the 4S 3300 batteries I already have plenty of. The intakes have also been reduced in frontal area as shown in the pics.

Will post more later!
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Old Aug 27, 2010, 03:10 AM
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You are going to town there, good job I probably need to do a similar thing to my EDO F-15, if it is worth fixing after a really annoying stupid accident.
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Old Aug 27, 2010, 03:26 AM
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It needed to be done. I didn't want another disappointing mid-size EDF.
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Old Aug 27, 2010, 03:37 AM
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Hi!

You have had the same ideas about this planes ducting as I have..

I am currently thinking about getting the plane and the best deal is getting it as and ARF from Germany, but I really would like to get a kit version so I would not have to cut it totally apart to change the intakes. Any tips acquiring the plane?

Have you thought about remodelling the ducts and intakes altogether to more scalelike appearance?

If I buy this plane I will cut 5 cm of ducting off and redo it from blue foam--> I will get nice round intakes.

Anyways, very good thinking!
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Old Aug 27, 2010, 06:17 AM
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I paid 52 for the airframe plus the stock fan/motor from my local hobby store. You can get it online from CML.com but expect to pay double that plus postage. The fan/motor will soon be featuring on ebay, so it's was a bargain kit!
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Old Aug 27, 2010, 07:20 AM
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The lander motor/fan is the best ive ever used.


Just had a look at CML massively overpriced
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Old Aug 27, 2010, 07:44 AM
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Lincolnshire, UK
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Yes, the Lander fan will not be glued in and neither will the ESC. I can see that fan being swapped out for my next project: an FMS mini F16 (also from CML). Ought to be fairly brisk!

As for CML pricing for RTF jets: They ain't the cheapest, but then again I don't really rate any RTF jet except the Phase 3 F16 and and perhaps their Squall. Bargain airframe-only deals are definately the way forward.
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Old Aug 27, 2010, 08:04 AM
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Mine is in my Lander f-16 , that is one nice piece of kit for 80 delivered for the airframe i couldnt turn it down , i had the Lander fan in my f-15 for a few days to test it before putting it in its f16 home , for me it was amazingly fast, the f-16 is a bit slower and doesnt float as nicely but looks evil when its flying ( especially when its coming at you full throttle at 10 feet above the ground).

Reading this with interest , i need to do some strengthening to 2 of my jets so i want to see how the carbon turns out , plus i am attempting the same inlet duct mods on my concept-x , they too are over sized and i too am using depron to reduce that area. I belly land with mine so strengthening the underside and inlet ducts is something i need to follow up on although i will be using carbon or glass on the inside of the inlet and using a coat or two of water based clear polyurethane on the outside to protect the foam.
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Old Aug 27, 2010, 10:32 AM
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yeah I got lucky with the garbon weave: acquired a couple of square feet from an aircraft manufacturer. My first mod to an F16 belly was with the proper HYSOL epoxy, but since then I've been using bog standard 1hr epoxy which is "massaged" in to the weave whilst it's between 2 sheets of thin clear film. I then lay it in by hand whilst wearing latex gloves. The carbon is running out so I'll soon have to move over to glasscloth which I'll fix in place either with WBPU or PVA. I'll probably make up some test pieces with depron to see which approach is strongest and best.

Si
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Old Aug 27, 2010, 12:58 PM
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When rebuilding the inlet lip on my new Eurofighter, I added a piece of 1/64 ply. I should have carried it along further, stupid me. I have then glassed and poly-c'd over it. I think this makes a good tough surface to belly land on, and it can be made to bend a certain amount. If you belly land like I do on grass, the foam can still be damaged through the glass, which would probably not happen if I had used epoxy underneath. Of course this is all good if you are repainting the model!! Si, where did you get the airframe from so cheap?
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Old Aug 28, 2010, 10:27 AM
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Yeah I used 1/32 ply for the first 3 inches of the intake on my Art Tech Typhoon too. Epoxied in place then covered with thin aluminium tape has been superb fever since, with no intake damage whatsoever after 100+ flights and fast landings: she's running 4s 2200-3000 batts in lieu of the stock 3s 1600.

I got the F18 from Phil at Phil's Models. Top bloke, but he's only got a few of these left. The standard price is 70, I got mine on a 25% off day when he was thinning out his stock a bit.

http://www.dpsfineart.co.uk/phillsmodels.htm
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Old Aug 29, 2010, 03:35 AM
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Thanks Si.
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Old Sep 12, 2010, 03:42 AM
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Update on the build

Sorry for the delay, guys. Here's how the build panned-out:
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Old Sep 12, 2010, 03:50 AM
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Lincolnshire, UK
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Maiden

I fitted some tiny balsa skids to the underside of the fuselage to protect the ESC then measured the C of G (about on the aft limit) then went for a flight.

It didn't go well. The power off the hand launch was great but the jet pitched up violently and I needed all my concentration to reign it in. Fortunately there was heap of power to keep the jet flying well throughout the bucking-bronco manouevres that followed. I gained some height and trimmed out the ailerons. I also trimmed further forward but it was obvious that the C of G was too far aft and that the jet was unstable in pitch. I used the next 3 minutes of flight to try and get used to this erratic jet and practice approaches. Every approach started extra-sensitive in pitch and then got worse as I slowed. Bummer. I made a couple of attempts, all of which resulted in an abort. Again, that Lander fan really pushed the jet skywards at the slightest hint of throttle: which is nice. The final approach was steady all the way in but pitched up at 2ft up and walking pace. The jet banged down and snapped in 2.

Luckily the break was clean so the 2 halves have gone back together nicely - you can barely see the join. I've now re-configured the battery tray and that pulls the CofG forward by 10mm at least so I'll go for another test flight today. The CofG is now on the forward limit of the recommended range so we'll see.

Wish me luck!

Si
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Old Sep 12, 2010, 05:34 AM
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Looks very nice Si , sorry to hear about the maiden , but at least it is easily repairable and you should be flying again pretty quickly.

RE cofg , i wouldnt worry too much , i have on many occasions had to move the cg forward on a few jets , the factory suggested point was way off , my concept-x was 8mm off ( not much but its a smaller jet ) and my lander f16 i ended up at 98mm which i think is 12mm in front of spec.

I always maiden at the same place , a patch of abandoned ground which has very long grass, i learnt after my su-27 decided to cobra straight after hand launch lol.

Good luck on the next flight , fingers crossed
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