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1/6 F-105 Build Thread

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Old 09-16-2018, 08:51 AM
  #51  
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Originally Posted by Viper1GJ View Post
Yea, your correct but the holes are just the pre drilled ones. Iíll drill actual mounting holes later. I just ďtackedĒ the NG in place with existing holes so I can get it on the wheels to check main toe in and NG height for correct pitch on ground.
Thanks. Keep your eyes peeled in case I do something dumb. I can use all the help I can get.

I think Iím actually the second owner after Joe. I know he had five at one time. Not sure what he still has.
Your structure surrounding the nose gear mount makes it perfect to use carbon flex plates, similar to BVMs concept. The load that nose gear sees is very significant. Flex plates absorb a lot prior to failing.

David
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Old 09-16-2018, 09:00 AM
  #52  
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Gonna go ahead 6 months in my time travel machine: landing gear.

As I recall on Bob's videos, at BITW and other places, pneunatic gear was just not up for the task. I see the nose gear has two actuators.....perhaps it was a mod after the fact.

​​​​​​I sincerely think pneumatic is a no-go for a model this size. Saw Bob's citation gear and off the bat did not see any locking mechanisms on his sketches. Not sure if the same is true for this one. Now, rather than sending to down n lock or similar, I'd just go to servocity and get creative, but I think a good screw jack drive should do the trick (torque is so high on those!).

If I can be of help with sketckes or ideas let me know.

awesome build!
David


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Old 09-16-2018, 02:51 PM
  #53  
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Hi David,

Thanks for the advice. Do you have a sketch of how you would use the flex plates on the nose?

Yes I'm concerned about the ability of the air system to work the gear, especially in flight. The mains have to retract forward into the air stream with a large gear door acting like an air brake, plus they are heavy. It will tax any air system. I have not tested the gear with air yet. I'm sure a jack screw system would be better.

The gear I have was designed by Joe and made by John from Matrix Machine in NY. It is completely different than the gear Bob made. It does have air pressure up and down lock over center cam device like most air gear. The problem is that both cylinders must move at the same speed and time to prevent jamming the crossbar.

I don't have any machining ability. If you have some ideas, please let me know.
Thanks,
Gary

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Old 09-16-2018, 03:20 PM
  #54  
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If Matrix did the gear,then I would give them a try first. If they don't work as intended,you just have to fit one of these inside the wing or nose, and find a way to connect the end ball fitting to the landing gear shaft. They have a LOT of torque on a very small package.

I will try to sketch something for you regarding the flexplates,specially the nose.

David
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Old 09-16-2018, 04:08 PM
  #55  
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At the very least a separate air system for nose gear with a high flow valve. Not a Xicoy as theybare 100# limited. Jettronics makes a high flow up to 150#.
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Old 09-17-2018, 06:12 AM
  #56  
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I would think there is a good chance the gear will work. Double air cylinders and better geometry. Matrix does good work. As mentioned these are not the original stuff
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Old 09-17-2018, 05:06 PM
  #57  
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There is a reasonable chance the mains will work on air given enough pressure and volume. I will try that first on bench test by hooking shop compressor to see how it works. After that if there are still problems maybe a jack screw solution can work. Bob Rullie had his main gears converted by Down and Locked and I think still uses air for the nose and brakes. TBD.

I plan to take the F-105 to Super Jets South in Georgia next week for a static display and conversation piece if I can fit it in the camper somewhere. It will be after the SJS meet before any more work gets done.

Today I made a full size drawing for the pipe. I will send to Joey at J. E. T. Pipes in Ft Worth, Texas to make the 300N custom pipe. He made the one for my 1/5 F-16 and it works great.



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Old 09-17-2018, 05:09 PM
  #58  
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David, you fly with the Thunderbirds RC Club in Ft Worth?

I was there when I retired from the Air Force at the Lockheed F-16 factory in 1995 before they moved the RC field to the current location.

Gary
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Old 09-18-2018, 05:15 PM
  #59  
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Need help with stab pivot point.

I was wanting to calculate and confirm the proper place for the stab pivot point for a subsonic RC jet model. Can anyone help me with how to calculate the stab pivot point. My internet research gave me results all over the place using gliders to jets.

What I really need to know is if the pivot point in the photo below needs to be changed. Any help from the smart aero guys is appreciated.

Thanks Gary



Dimensions are approximate and do not include the rounded stab tip.

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Old 09-18-2018, 05:57 PM
  #60  
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Do you mean the MAC? if so the large model documentation on AMAs site has some info
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Old 09-18-2018, 06:12 PM
  #61  
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Hi Keith,

No its not the MAC. I know how to calculate that. I'm looking for the placement recommendations for the pivot point for flying stabs. I've seen, 20-25-27% MAC and others. Just looking for knowledge of what works from some smarter guys than me.

Thanks,
Gary
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Old 09-18-2018, 10:28 PM
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Originally Posted by Viper1GJ View Post
Hi Keith,

No its not the MAC. I know how to calculate that. I'm looking for the placement recommendations for the pivot point for flying stabs. I've seen, 20-25-27% MAC and others. Just looking for knowledge of what works from some smarter guys than me.

Thanks,
Gary

Gary,
The AMA Lma documents has their required ďpercent of macĒ for a full flying stabilator pivot point location.
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Old 09-19-2018, 06:34 AM
  #63  
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Hi Thomas,

Thanks for the AMA Info. I used that diagram to design the canards and servo system on my Sabre XLT jet a few years ago but forgot about it.

Hereís what it says: The pivot point for the control surface can be determined using the diagram below as long as the pivot point is ahead of the 25% Mean Aerodynamic Chord (MAC) point by 2%-4%.

So thatís a pivot point at 21-23% MAC. Which is better, Is that really valid, and where does the info come from other than AMA LMA document?

Thanks,
Gary
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Old 09-19-2018, 07:01 AM
  #64  
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Who has the Bob Park's Bat signal!?! Seriously, may be worth tracking a contact email down for him and getting his input.
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Old 09-19-2018, 07:04 AM
  #65  
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Now there’s a name drop from the archives!! Smart mo fo
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Old 09-19-2018, 07:57 AM
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Originally Posted by Viper1GJ View Post
Hi Thomas,

Thanks for the AMA Info. I used that diagram to design the canards and servo system on my Sabre XLT jet a few years ago but forgot about it.

Hereís what it says: The pivot point for the control surface can be determined using the diagram below as long as the pivot point is ahead of the 25% Mean Aerodynamic Chord (MAC) point by 2%-4%.

So thatís a pivot point at 21-23% MAC. Which is better, Is that really valid, and where does the info come from other than AMA LMA document?

Thanks,
Gary
Honestly i have no idea where those figures come from. Oli Nichols was doing some really well done subject matter a few years back on servo selection, linkage geometry, etc, but stopped. He would be a good source to turn to for advice.

Im in the same boat currently as i finish the Cad design and plug construction of a large T38, so whatever info you come up with, iíd be grateful to hear as well.
I currently used the Lma info and split the difference of the position range at 22% mac. I may 3D print a stab and some contraption to hang it out a car window just to see what it does. Haha
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Old 09-19-2018, 09:38 AM
  #67  
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Thomas,

I wrote Oli an email last night. He has been very helpful giving me, the novice, good advice in the past.

Your T-38 project would be great. I’ve wanted to do one for a long time. I had about 1200 hours in them back in the late 70’s before the F—16 time. I had my worst malfunction in one with a tail number of #64366. Both wing tips were corroded and delaminated and broke off under 5g. Was an exciting landing. That’s the one I want to model. What size turbine will yours use?

Gary
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Old 09-19-2018, 12:00 PM
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Originally Posted by Viper1GJ View Post
Thomas,

I wrote Oli an email last night. He has been very helpful giving me, the novice, good advice in the past.

Your T-38 project would be great. Iíve wanted to do one for a long time. I had about 1200 hours in them back in the late 70ís before the Fó16 time. I had my worst malfunction in one with a tail number of #64366. Both wing tips were corroded and delaminated and broke off under 5g. Was an exciting landing. Thatís the one I want to model. What size turbine will yours use?

Gary
Its 118Ē long, so im thinking somewhere around a K210.

Im modeling the newer C model though with the newer inlets as it provides options for better EDF power that two customers have dictated.
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Old 09-19-2018, 02:16 PM
  #69  
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Hey Gary ... the question is whether you would model it as it took off (std wing) or as it landed (clipped wing)!! LOL!

F-105 looking great! Can't wait to see it in person next week!

JS

Originally Posted by Viper1GJ View Post
Your T-38 project would be great. Iíve wanted to do one for a long time. I had about 1200 hours in them back in the late 70ís before the Fó16 time. I had my worst malfunction in one with a tail number of #64366. Both wing tips were corroded and delaminated and broke off under 5g. Was an exciting landing. Thatís the one I want to model. What size turbine will yours use
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Old 09-20-2018, 11:00 AM
  #70  
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Old 10-08-2018, 12:53 PM
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I finally got back into the shop this week after about 3 weeks out for the SJS jet meet in Georgia and family visits. Finally getting caught up on chores now so had some time today to get organized in the shop again.

I took the F-105 to SJS for a static display. We had it out for a couple of days and got lots of comments...good luck, better you than me, etc. Also got lots of good ideas from folks about how to build and fix some if the issues. Made some progress on the gear toe in fix and how to make the stabs and linkage work. Overall it was a positive experience talking to everyone and picking their brains about how to make it happen. My BVM 1/5 F-16 to the left of the F-105 flew well all week so it was a great trip and everyone had fun.

Hoping to get some more work done this week and will post more photos as time permits.
Gary











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Old 10-08-2018, 02:38 PM
  #72  
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Gary,
Thanks for bringing the Thud to SJS. Your patience and detail in working out the engineering challenges are quite apparent. Looking forward to more progress and watching the maiden at First in Flight!
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Old 10-08-2018, 04:45 PM
  #73  
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I've had to scrap the stab system that came with the kit. The stab mounts and drive mechanics were binding and did not move freely. I replaced the bearings and no help. I found the holes in the pivot arm frame were not parallel and if the frame was tightened up the pivot would bind. Next I found out quite by accident that the pendulum arm that held the stab pin was different length on the left and right sides. This made them not usable with out remaking one side.



Look carefully and you can see the stab pin on the left is higher than the one on the right because the pendulum arms are different lengths. The parts were hand made and must been made in different batches and I got a mixed pair.


Next I took some time to figure out the pivot point of the stab that came with the kit. As mentioned before I was told it was too far forward.
I used the diagram in the AMA LMA Document as a guide to figure out the MAC and then the pivot point as a % MAC of the stab. Using the diagrams below I figured the pivot was well forward of the AMA recommendations and therefore not very good in my opinion. My pivot is about 7.8% MAC. Also the pivot pin is 3/8" solid aluminum and is too small in my opinion and I don't know what it is made of but it looks like soft aluminum. What ever it is I'm not comfortable with it as is.



AMA LMA flying stab recommendation





Drawing extending root and tip chord lines


Recommended position of pivot point vs actual location of pivot point.

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Old 10-08-2018, 05:39 PM
  #74  
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Last is the stab airfoil. I asked Oli at Ultimate Jets (who has been very kind to provide me with educated advice and guidance on design and materials when I asked) about where the AMA recommendations came from and on what data were they based. He advised that the AMA recommendations would work well with an airfoil like a pure NACA 0009 where the center of pressure would be closer to the pivot point and would not move much with with changes in AOA

Oli helped me compare my stab airfoil with the NACA 0009 below and the stab airfoil is much fatter behind the pivot than it needs to be and the leading edge is more blunt and rounded. All this put the stability point and center of pressure way behind the pivot point. Oli also expressed concern with the small size and material of the pivot pin. In his opinion is the stab would fail and I should focus on making a stab with the proper airfoil, pivot point, and materials.

Ok sounds like good advice from a very smart engineer so I am now planning on rebuilding the stabs and linkage system.

One bite at at time....



Stab airfoil and leading edge deviates quite a lot from proper airfoil, pivot pin in wrong location, and pivot pin too small for the loads

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Old 10-09-2018, 03:04 AM
  #75  
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Mike,
Good to see you at SJS. Thanks for the encouragement. I got lots of good ideas from folks there. Hopefully I will make some good progress over the winter.

Gary
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