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Skymaster F14 Tomcat

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Skymaster F14 Tomcat

Old 01-28-2016, 04:25 PM
  #1526  
FenderBean
 
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Originally Posted by EDFJim
Heads up on control horn for stabs... Blue was with the kit aluminum is JR horn .. Got a report of the blue horns bending causing a loose stab ... Pics on Facebook
I heard this last week, I have the blue horns for futaba servos, I had to tell them what servos I would be running so they could sent the correct one. Not understanding what your saying, is it a JR arm issue or both?
Old 01-28-2016, 04:36 PM
  #1527  
EDFJim
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Originally Posted by FenderBean
Jims super technical and extremely difficult center fuse stand is nice I was going to make on one like his but I have forward and aft rails on mine so I have to sit mine on foam.
Lol hey that's quality!
Old 01-28-2016, 04:41 PM
  #1528  
Zeeb
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Originally Posted by current control
gentlemen, what are you using for work stands, transport stands, for this plane.
I have a pvc stand that I am not real happy with. with ordinance this plane doesn't leave much room for any type of stand.
thinking about going high end aluminum and using my guy who does boat tops. any ideas?
Be interested to see those possibilities myself. I bought one from a gentleman who had the shop stand deal worked out but was transporting it on it's gear.

I had it shipped to my builder for some new engines and TLC. When I went to pick it up, the only thing we could come up with was foam. But that was done with none of the armaments, their mounts, the drop tanks and I even felt like the strakes needed to come off.

I'd be happy at this point if I could figure out a good solution for transporting it with just the drop tanks and strakes installed.
Old 01-28-2016, 05:36 PM
  #1529  
EDFJim
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Originally Posted by FenderBean
I heard this last week, I have the blue horns for futaba servos, I had to tell them what servos I would be running so they could sent the correct one. Not understanding what your saying, is it a JR arm issue or both?
skymaster sent me the blue horns that fit JR servos but they can twist so I got the wider JR aluminum horns that have more metal and are stronger to avoid any twist
Old 01-28-2016, 08:24 PM
  #1530  
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Originally Posted by EDFJim
skymaster sent me the blue horns that fit JR servos but they can twist so I got the wider JR aluminum horns that have more metal and are stronger to avoid any twist
Dang it Jim im an rc builder not an engineer!!! LOL okay I will looking into some better arms, I have seen someone use SWB arms in this same application.
Old 01-30-2016, 06:30 PM
  #1531  
current control
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Elevator horns bending issue...
looking at it further it would be very difficult to bend a arm
however
with great quality Chinese bolts
it is easily possible to bend the bearing support bolt leading to bending the arm
just my 2c
anyone have a good source foe titanium bolts so something very strong and not brittle?
Old 01-30-2016, 06:46 PM
  #1532  
Woketman
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McMaster-Carr????
Old 01-30-2016, 07:32 PM
  #1533  
dbsonic
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titanium's main advantage is weight over steel alloy. not so much in strength. Any SS would be a good choice.
Old 01-30-2016, 07:45 PM
  #1534  
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But there are many different steels that bolts are constructed from. Your average joe blow Home Depot fasteners are rather unknowable, tensile strength wise. In aerospace applications, we routinely use fasteners that have an Ftu (ultimate tensile strength) of 180 ksi. Those are the usual ones. There are 260 ksi fasteners available, but they are pricey!!!! Those are an alloy MP-35 or 65 or something like that. Does not come to mind right now. Could be the rum.....
Old 01-30-2016, 09:51 PM
  #1535  
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Originally Posted by current control
Elevator horns bending issue...
looking at it further it would be very difficult to bend a arm
however
with great quality Chinese bolts
it is easily possible to bend the bearing support bolt leading to bending the arm
just my 2c
anyone have a good source foe titanium bolts so something very strong and not brittle?
I was thinking the same thing, but the bolt was intact, don't ask me how found out, lol

I was the one learned it the hard way and like to share with the rest of you. I put the bolt on the outer hole of the arm thinking I would get higher leverage and resolution out at the surface and the difference of torque/resolution would offset itself had I put it elsewhere. Lesson learned, prioritize the integrity of arm is paramount....., until the next weak point is discovered, probably the bolt.

By the way the tomcat was manageable with one stab flying, difficult but manageable

Here's the flight report I wrote myself:
On its 41st flight, at Riverside field (a mostly right turn pattern field), I was doing maneuvers mostly from right to left and on the second loop at 11 o'clock (pushing hard with full throttle), I had fluttering on the stabs with good visual on the left side, quickly throttle down, (subsequent analysis - I believe the right stab was trailering by this time) stayed with it and realize I was able to level the jet (wings were forward with flaps and slats retracted and both spoilerons good, rudders 100%, stabs one sided) had very little pitch with wild pitch and roll results when pulled, but I was still able make a 180 into upwind, at one point I thought I was going to make the run way, dropped the gears, tried to slow down some more, cut power, slight pull, jet banked and pitched up violently, counter inputs and opened some throttle, sucked up gears, decided to belly in with some throttle, shut engines, and minimal damage to the airframe. I sat down to comprehend, mostly taking a slight break from 102F, all in a sudden saw black smoke, apparently engines were FODded didn't go into cool down, by the time I was out to the Tomcat with my co2, some 200 feet forward of runway and about 800 feet down range, the fire was not surrendering to my no more then 10 seconds of burst out of the extinguisher. All I could do is to take some pictures, and retreat back to the shaded canopy for it to burn down, all I was able to save were a couple of mini GSUs, lol.

$500 per flight jet, lol

Barry

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Old 01-31-2016, 06:45 AM
  #1536  
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Sorry to see that Barry!
Old 01-31-2016, 08:51 AM
  #1537  
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Originally Posted by marquisvns
I was thinking the same thing, but the bolt was intact, don't ask me how found out, lol

I was the one learned it the hard way and like to share with the rest of you. I put the bolt on the outer hole of the arm thinking I would get higher leverage and resolution out at the surface and the difference of torque/resolution would offset itself had I put it elsewhere. Lesson learned, prioritize the integrity of arm is paramount....., until the next weak point is discovered, probably the bolt.

By the way the tomcat was manageable with one stab flying, difficult but manageable

Here's the flight report I wrote myself:
On its 41st flight, at Riverside field (a mostly right turn pattern field), I was doing maneuvers mostly from right to left and on the second loop at 11 o'clock (pushing hard with full throttle), I had fluttering on the stabs with good visual on the left side, quickly throttle down, (subsequent analysis - I believe the right stab was trailering by this time) stayed with it and realize I was able to level the jet (wings were forward with flaps and slats retracted and both spoilerons good, rudders 100%, stabs one sided) had very little pitch with wild pitch and roll results when pulled, but I was still able make a 180 into upwind, at one point I thought I was going to make the run way, dropped the gears, tried to slow down some more, cut power, slight pull, jet banked and pitched up violently, counter inputs and opened some throttle, sucked up gears, decided to belly in with some throttle, shut engines, and minimal damage to the airframe. I sat down to comprehend, mostly taking a slight break from 102F, all in a sudden saw black smoke, apparently engines were FODded didn't go into cool down, by the time I was out to the Tomcat with my co2, some 200 feet forward of runway and about 800 feet down range, the fire was not surrendering to my no more then 10 seconds of burst out of the extinguisher. All I could do is to take some pictures, and retreat back to the shaded canopy for it to burn down, all I was able to save were a couple of mini GSUs, lol.

$500 per flight jet, lol

Barry


horrible, the flutter was caused from the servo going out?
Old 01-31-2016, 08:59 PM
  #1538  
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Thanks Dr. Mike!
Alkaline, no not servo but the arm, see picture.

Barry
Old 02-01-2016, 12:27 AM
  #1539  
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Hi Barry
Sorry about the F-14 that hurts, at least you know what the issue was.
Old 02-01-2016, 08:06 AM
  #1540  
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Barry, I was wondering do you know what caused the flutter? I would think the flutter itself would cause the arm to bend. The only thing bending in flight would do is cause some binding, unless it was so flimsy the arm flexing back and forth enough to cause flutter. You said you moved the bolt to the outside hole to get better resolution, my servo arm only has one whole for the bolt. Is it possible you had different servo arms than mine and Jims? Hate you lost so much money on the crash, I know people say if you have to worry about it you shouldn't be flying it but I have considered just getting rid of mine due to all the problems I have had and now things like this. I haven't been very impressed with the overall quality of this kit.
Old 02-01-2016, 09:38 AM
  #1541  
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Thanks guys, and if I told you this didn't even put a dent in my wallet or my ego, I'd either be lying or still in denial, lol

Yes Duke, at least I know what had happened and be able to share.

I would drill an inner hole if possible, otherwise, upgrade to a beefy JR arm and cut it shorter. Fender, I think the kit is good, not the easiest obviously but for the rewards of a Tomcat from its complexity and challenge was worth it and lands like a ***** cat too.
Old 02-05-2016, 09:28 PM
  #1542  
Roger Shipley
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Oh yea Barry I know only too well the entire range of emotions one goes through.........but as BV told me many years ago this hobby is not for everyone.....how true, huh ! ! !

It took me about 6 months of grief to get a replacement Hawg under way so will see you on the flight line, Roger
Old 02-05-2016, 09:45 PM
  #1543  
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Barry, I feel your pain!! ;-). Glad you were able to isolate the issue. One day I'll jump on the Tomcat horse again.

Last edited by dubd; 02-06-2016 at 04:56 PM.
Old 02-06-2016, 10:21 AM
  #1544  
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After hearing a bout Barry's incident I tested the stock arms to determine how much force it took to bend or twist the arms. I put the base of the arm assembly in a vise and used a luggage scale attached at the far end of the bearings. It took 40 lbs of pull to bend the stock arm. I then repeated the test with an "Integy" arm which started to bend at 60lbs of pull. A 50% improvement.

I also counterbalanced
the Stabilators.

I have not yet flown this arrangement.

Ill ll now try to post photos. I also had to recess the servo to allow for the thicker arms.
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Old 02-06-2016, 10:56 AM
  #1545  
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SS 40lbs is a lot, can some check me but thats higher than the stall torque on my bls 172 which is 500oz of torque. Unless I used the wrong conversion 500 oz is 31.25 lbs ? Thoughts on this
Old 02-06-2016, 11:43 AM
  #1546  
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My thoughts also. Barry recently posted that he thought the stabilator fluttered which would explain the high load. I also don't know how much flexing or elasticity the stabilator control system had with that arm. Hopefully a stronger, stiffer arm would have less. I don't think Barry's Stabilators were counterbalanced but I'm not sure.
Old 02-06-2016, 11:59 AM
  #1547  
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Have you guys done a careful mathematical assessment of the correct positon of the pivot in the Stab. It sounds that it may be a bit out and requiring too much force. No doubt Oli would help if asked nicely.

John
Old 02-06-2016, 01:49 PM
  #1548  
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As far as balancing stabs go on bigger planes I always do it now. I have never seen a plane crash because it had balanced stabs but I have seen them crash because they didn't. Also make sure you guys have tight hinges on the rudders. The one that crashed at topgun last year had rudder flutter and the vertical came off in flight before it crashed. I was looking at what was left and it had tons of play on the rudder hinges and also rudder linkage itself.
Old 02-06-2016, 02:19 PM
  #1549  
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Mine was not statically balanced, and I did a quick plot of the pivot point when I first receive the jet and was satisfied with AMA's calculation guide line, which I believe also contributed the 14's survivability when the right stab departed from its control linkage. Never mind the subsequent fire!

Steve, with your skills and statically balancing, I would expect you be able to land it on the runway and taxi back.

Barry
Old 02-06-2016, 05:58 PM
  #1550  
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Barry don't kid yourself this thing is intimidating to me as hell! I don't know if anybody could grease it in on one stabilator and spoilers. There are so many potential technical reasons for this thing to become a fireball. But as you said, it's really cool.

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