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Skymaster F18F c of g position

Old 06-06-2011, 01:45 AM
  #51  
Craig B.
 
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Default RE: Skymaster F18F c of g position

Hi Millsy,

Lighting system is from electrodynamics, compact and light. Have not tried full length camber change....don't think it needs it as it will land slowly enough as it is. The elevator mod is critical I reckon....have done it with all of my skymaster kits. To swing a huge stab like that off a 23mm long control arm is not a good idea, particularly when there is room for almost twice that length.

BTW, if you have dialled your dual rates right down you will not be losing resolution, only compressing it over a reduced range. If you dial down your ATV, then you are losing resolution over your final servo travel, because your are trimming off the ends of the travel. That's why the gyro manufacturers tell you to set your ATV to 100% no matter what, and reduce your servo travel by reducing your dual rates. Anyway, irrespective of any of that, it is prudent to apply the best mechanical arrangement possible.

Here is an example of what I did on my 1/6 F16 ...did the same thing on all of my other jets too and makes me a lot happier about hauling on the thing



Good luck with your F18.

Regards,

Craig.

ps. will say hi to Mike for you.

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Old 06-06-2011, 05:04 PM
  #52  
millsy14
 
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Default RE: Skymaster F18F c of g position

Cheers for that, nice bit of sheety work there, lol
You probably have done so already, but I will let Skymaster know about these mods.
Old 06-07-2011, 04:42 AM
  #53  
Craig B.
 
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Default RE: Skymaster F18F c of g position

Thanks Millsy. The extension arm in the above photo is off at an angle to compensate for the fact that the flats on the stab pivot rods were ground at different angles and I set this one up to get the ball link at the same location in relation to the pivot stab. Fixed two problems with one piece of ali!

I have not sent this to skymaster....guess I figured that my input would not really have mattered and was just happy to do my own thing. It sure makes the stabs a lot more solid with far less slop. Have done this mod on all of my skymaster jets. Feel free to let them know Millsy.

Craig.

Old 06-07-2011, 05:42 AM
  #54  
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Default RE: Skymaster F18F c of g position

I sent them an email today, also with a link to this thread.
With the resolution, that is actually what I meant, like you said. The servo resolution is at 100% but the linkage ratio amplifies the resolution, making it physically worse than what is set on the radio, which of course amplifies all the slop as well.
Old 05-18-2013, 09:04 AM
  #55  
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Default RE: Skymaster F18F c of g position

Hope you don't mind me bringing this back from a bit from in the past, but mine was shelved for a long time due to work and other factors.. I also had to replace the original right stab as the shaft was sloppy in the stab. I'll peel back the bottom and examine it, and rebuild it as a possible spare if I ever need it. I definitely think there is a serious lack of hornet threads around here lately. :-)

I have it set up with every servo linkage at the closest holes on the arms and atv's all set at 100%, and at high rates (100%) I am getting the recommended throws, so I'm pretty happy with that. Just now setting up my cg and after reviewing a lot of posts, I set it up for 130mm. I originally had set it up for twin batts, via regulators to a Smart Fly Expander board. Well, i ditched the regulators and nimh packs in favor of direct hook up with twin large capacity LiFe packs. To balance as it is here in the pic, I only needed 16.6 oz of battery on the nose. Just need a tad more to level her out. No dead weight required. The scale cockpit and pilot helped with that...nice!

Tomorrow I'm doing run ups and taxi tests to check the brakes and nose/gyro steering, etc. Hopefully to maiden later this spring/summer.

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Old 05-24-2013, 03:56 PM
  #56  
john josey
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Default RE: Skymaster F18F c of g position


ORIGINAL: Sparhawk

Hope you don't mind me bringing this back from a bit from in the past, but mine was shelved for a long time due to work and other factors.. I also had to replace the original right stab as the shaft was sloppy in the stab. I'll peel back the bottom and examine it, and rebuild it as a possible spare if I ever need it. I definitely think there is a serious lack of hornet threads around here lately. :-)

I have it set up with every servo linkage at the closest holes on the arms and atv's all set at 100%, and at high rates (100%) I am getting the recommended throws, so I'm pretty happy with that. Just now setting up my cg and after reviewing a lot of posts, I set it up for 130mm. I originally had set it up for twin batts, via regulators to a Smart Fly Expander board. Well, i ditched the regulators and nimh packs in favor of direct hook up with twin large capacity LiFe packs. To balance as it is here in the pic, I only needed 16.6 oz of battery on the nose. Just need a tad more to level her out. No dead weight required. The scale cockpit and pilot helped with that...nice!

Tomorrow I'm doing run ups and taxi tests to check the brakes and nose/gyro steering, etc. Hopefully to maiden later this spring/summer.

Nice timing.....I'm just about to order the 'F' model in the next week or so. I've been told it's an 8 week wait from time of purchase so that should give me time to get the funds together for the engine.My plan is to get it built and flown before the end of the year to set me up nicely for next season and i'll also be taking on-board the suggestions and comments made by the guy's that have flown these things and hopefully it will be a pain-free-ride.Anyway, keep us posted on how your getting on.cheers john
Old 09-30-2013, 01:45 AM
  #57  
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Hi Guys,

Any recent updates on skymaster F18F build up and flights? I will get mine in a couple of weeks i assume and although i found some threads they are old by 6-7 years and was wondering if skymaster has made any changes to recommendations from people in this thread and if anybody purchased one in 2013 and has flown it so we can share any info that at least is recent and maybe more valid.
Old 06-24-2014, 03:43 PM
  #58  
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Hi Guys, thanks for the encouraging dialog. I don't normally post, but I nearly lost a pair of boxers and an F-18F in Blue Angel colors a few hours ago. My friend in Houston has the same bird (different colors) and our setup is identical, his flys very well. On my first flight, the plane rotated and went pure vertical on rotation. The manual (as you're aware) states that a CG between 160 and 140 is "ok"...so I moved the CG from 155 up to 141. Flight two, same exact personality....rotation and uncommanded pitch to vertical. The pitch was so sensitive that I flew the balance of the flight using elevator trim only. What a wild ride. Even with a stable approach, I had a poor landing and am writing John for parts prices. What a day... I'm glad I'm not the only one with this event - been flying RC 40 years, and my garage of Skymaster planes all fly awesome. Take care - be safe out there.
Old 06-24-2014, 05:13 PM
  #59  
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Yes,shifting the cg back will help rotation,.. In Basimps video you can watch him kicking quikly and returning back to almost neutral position almost at once on takeoff.. not everybody can do this ! Taking off with flaps like Ravill and many people also recommends turns this takeoffs into a non-issue. even with a less sensitive, aft CG.

I also remembered a thread of a F-18 doing the "jump" from a pilot of singapore from some years ago.. impressive pictures and a good save:

http://www.rcuniverse.com/forum/rc-j...l-takeoff.html

This was written before Dr.Honda maiden jet flight.(!)
Old 06-25-2014, 01:31 AM
  #60  
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Originally Posted by mitch767
Hi Guys, thanks for the encouraging dialog. I don't normally post, but I nearly lost a pair of boxers and an F-18F in Blue Angel colors a few hours ago. My friend in Houston has the same bird (different colors) and our setup is identical, his flys very well. On my first flight, the plane rotated and went pure vertical on rotation. The manual (as you're aware) states that a CG between 160 and 140 is "ok"...so I moved the CG from 155 up to 141. Flight two, same exact personality....rotation and uncommanded pitch to vertical. The pitch was so sensitive that I flew the balance of the flight using elevator trim only. What a wild ride. Even with a stable approach, I had a poor landing and am writing John for parts prices. What a day... I'm glad I'm not the only one with this event - been flying RC 40 years, and my garage of Skymaster planes all fly awesome. Take care - be safe out there.
I would think you need to move your COG forward not backward if you have an issue with your elevator being too sensitive as long as the throws are set the same as your friends. So you Really have 2 issues, the vertical takeoff is a different issue.

Check to see if your friends has a different AoA when its sitting on the ground. From what I found with my Feibao F18F if it has a negative AoA on the ground when it builds up speed it tends to push the nose down on takeoff which means you have to use a fair bit of elevator to make it unstick which generally causes the F18 to take off at a high angle, most R/C F18 pilots suggest a fair amount of flap on take off. Plus you actually hold elevator in until it builds up speed on the ground and the nose becomes lighter then relax the elevator a little. You can try adding a spacer plate between the front retract and mount to increase the AoA slightly as well.

Hope it helps.
Old 06-25-2014, 10:13 AM
  #61  
basimpsn
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Originally Posted by mitch767
Hi Guys, thanks for the encouraging dialog. I don't normally post, but I nearly lost a pair of boxers and an F-18F in Blue Angel colors a few hours ago. My friend in Houston has the same bird (different colors) and our setup is identical, his flys very well. On my first flight, the plane rotated and went pure vertical on rotation. The manual (as you're aware) states that a CG between 160 and 140 is "ok"...so I moved the CG from 155 up to 141. Flight two, same exact personality....rotation and uncommanded pitch to vertical. The pitch was so sensitive that I flew the balance of the flight using elevator trim only. What a wild ride. Even with a stable approach, I had a poor landing and am writing John for parts prices. What a day... I'm glad I'm not the only one with this event - been flying RC 40 years, and my garage of Skymaster planes all fly awesome. Take care - be safe out there.


Are you using the same engine power as your friend?...if less.. you might have a modified your AOA from the nose gear.
Old 06-25-2014, 10:16 AM
  #62  
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Originally Posted by erbroens
In Basimps video you can watch him kicking quikly and returning back to almost neutral position almost at once on takeoff.. not everybody can do this ! Taking off
I need to watch that again
Old 06-25-2014, 10:21 AM
  #63  
ravill
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Originally Posted by erbroens
Yes,shifting the cg back will help rotation,.. In Basimps video you can watch him kicking quikly and returning back to almost neutral position almost at once on takeoff.. not everybody can do this ! Taking off with flaps like Ravill and many people also recommends turns this takeoffs into a non-issue. even with a less sensitive, aft CG.

I also remembered a thread of a F-18 doing the "jump" from a pilot of singapore from some years ago.. impressive pictures and a good save:

http://www.rcuniverse.com/forum/rc-j...l-takeoff.html

This was written before Dr.Honda maiden jet flight.(!)
Wow, what great pics of that vertical take off. You can even see the exhaust plume just flying out of the nozzles!

Flaps, flaps, flaps!!

Hornets "may" need a positive AOA for take off, but they absolutely NEED LOTS of flap for a smooth take off.

I know there are some people (Jetnuno, is one of them I think?) who says a superhornet was his first jet and he doesn't use flaps for take off, but let me assure you, those people are the VAST minority.

Use lots of flaps for take off, you'll be fine!
Old 06-25-2014, 10:31 AM
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Thanks guys - I can honestly say that my 18F did the same vertical takeoff. My CG is 141, and I use 22mm of flaps for departure. I need to wait for John to send parts, but in the meantime, I'm going to add some shim to the nose gear so that we have a positive AOA for takeoff. I'm so glad that God gave me another chance to fly the 18F...I flew the bird on elevator trim...so glad to have a bird to repair: it could have been a lot worse! Thanks guys, and continued success in all you do!
Old 06-25-2014, 10:39 AM
  #65  
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After discussing the cg with Michel (Chile SM dealer), he said that a 130mm is a good place to start. Watch his videos on SM's website and judge for yourself. USE full flaps!

Dan
Old 06-25-2014, 12:01 PM
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Mitch, 22mm is just not enough. You need 35-45 degrees. Trust us.
Old 06-26-2014, 01:25 AM
  #67  
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Guys, been thru all the same stuff on my SM F18-F. I posted on this previously, aka millsy144. Definately things that will help to alleviate the vertical leaping t/off were-

Lengthening elevator arms to reduce servo slop and resolution. Standard arms are way too short.
Raising nose by lengthening noseleg with packing, and fit heavier springs into shock strut.
With a long enough runway, and as long as nose is sitting high, model will rotate by itself.
Technique of feeding in elevator gradually, until nose starts to lift, then release elevator as soon as model starts to pitch up.

I dont have a massive flap setting for t/off config. Basic flight physics tell you that high flap settings=high drag, not desireable during a takeoff.

If you look at pics and videos of the fullsize counterpart, they actually use a rudder reflex-in mix on takeoff and landing. Possibily, due to the same issues with trailing link landing gear.
Old 06-26-2014, 06:46 AM
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Yes, this is another solution, having the jet sitting in the ground in a AoA that let it break ground without rotation when the appropiate speed is reached. And you are right too, the rudder reflex-in is for helping pitch up trim at low speeds without using the tailerons.

About basic flight physics, seems that the F-18 defies them... when appropiately powered the F-18 doesn´t care about the extra drag. :-)

https://www.youtube.com/watch?v=2rgWyKLQe00
Old 06-27-2014, 03:56 PM
  #69  
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I guess this guy didn't have enough flaps or positive AOA for takeoff.......


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Old 07-01-2014, 12:20 AM
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Haha, yer. I think it's also called inertia!
Old 01-22-2015, 05:19 PM
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Im looking for any orange and white military color scheme pics for my F18, any help would be appreciated! Thx!
Old 01-22-2015, 05:22 PM
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drottman300
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neep pics from all angles! thx!
Old 01-22-2015, 06:54 PM
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The China Lake Scheme is my Personal Favorite Orange and White


Here's a link to Airliners.net ... Happy Flying!

http://www.airliners.net/search/phot...471j2297585j10
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