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Composite ARF Mig29

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Old 02-12-2019, 01:35 AM
  #576  
David Gladwin
 
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I would certainly replace the stab. Shafts as the inboard holes you show are near the bending point. Failure of these pultruded rods is unlikely in normal use, but in a flutter sutuation as I encountered, who knows ?

Replacement would be my remedy.

I changed the wing retention method. There is a blind nut mounted inside wing root rib, with a bolt inserted from the wheel well. One in each wing. It works and is easier than fiddling around finding the holes in the wing rods !

My Mig is airworthy, just waiting for some warmer weather to do some paint refinishing etc. The scale cockpit is done, just needs painting

David.
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Old 02-12-2019, 06:19 AM
  #577  
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Thanks fellas, that's kind of what I was thinking too but wasn't sure if I was overthinking it.

Originally Posted by David Gladwin View Post
I would certainly replace the stab. Shafts as the inboard holes you show are near the bending point
David, can you clarify what you mean about they are near the bending point?

How far out on the stab are others mounted? I'll search this thread for any more pics of other setups.

Now, where to get 12mm pultruded CF rod and quick...

Last edited by Auburn02; 02-12-2019 at 06:30 AM.
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Old 02-12-2019, 09:27 AM
  #578  
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Well no luck on any photos of stab undersides in this thread. If anyone can share a pic or two of their stab/tube setup to show how far out the bolts are installed, that'd be great. Likewise, any more info on the wing mounting would be appreciated - i.e. did you use a blind nut in the root rib like David, one bolt through the forward spar a bolt through each spar, what size bolts, etc.

Wish I had a dang manual for this bird.
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Old 02-12-2019, 09:30 AM
  #579  
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Originally Posted by Auburn02 View Post

Wish I had a dang manual for this bird.
the manual wasnt much help when it came to any of that stuff. I glued and bolted the stab spars into the stab and machined control horns that fit over the inboard end of the shaft to connect to the ball link and used one large servo. The suggested method of connecting servos in the manual is one of the most ghetto methods I have ever seen.
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Old 02-12-2019, 09:34 AM
  #580  
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Originally Posted by LGM Graphix View Post
the manual wasnt much help when it came to any of that stuff. I glued and bolted the stab spars into the stab and machined control horns that fit over the inboard end of the shaft to connect to the ball link and used one large servo. The suggested method of connecting servos in the manual is one of the most ghetto methods I have ever seen.
You know, I had thought about just gluing them into the stabs. I'm not sure what the original connection method was for connecting servos, but this plane does have a machined horn that slips over the inboard end of the pivot rod and secured by a bolt, ball link connecting that horn to a single servo. I really don't plan to remove the stabs for transport, so having to open up the nacelles to do it on the rare occasion I need to pull them wouldn't be the end of the world. I think you just helped make that decision for me. Still need to order some new undrilled rods though.

Thanks Jeremy!
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Old 02-12-2019, 12:50 PM
  #581  
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Originally Posted by Auburn02 View Post
You know, I had thought about just gluing them into the stabs. I'm not sure what the original connection method was for connecting servos, but this plane does have a machined horn that slips over the inboard end of the pivot rod and secured by a bolt, ball link connecting that horn to a single servo. I really don't plan to remove the stabs for transport, so having to open up the nacelles to do it on the rare occasion I need to pull them wouldn't be the end of the world. I think you just helped make that decision for me. Still need to order some new undrilled rods though.

Thanks Jeremy!
the original design used 2 servos on each stab set at awkward angles. The stab rod had 2 holes drilled and tapped with 4-40 bolts threaded into them with a nylon clevis on them that a snap link style connector hooked to as I recall. I remember looking at the design and thinking it was about the dumbest way to do things possible. Matching the 2 servos must have been a nightmare.
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Old 02-12-2019, 12:52 PM
  #582  
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Wow, that does sound awful.

I went back to your build thread and the one I'm finishing now has a very similar setup to what you made. I'll get some pics up as I work through this one. Do you recall your wing attachment method, anything crazy there?
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Old 02-12-2019, 12:57 PM
  #583  
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There is a picture in this post of the control horns I made up for the stabs. There were 2 aluminum horns welded to an aluminum spacer between them that spacer was drilled and tapped and the carbon shaft drilled and tapped so when the bolt went through it locked everything into place. The horn was positioned up against the stab spar socket to keep the stabs from moving in and out as well.

http://www.rcuniverse.com/forum/10715312-post89.html
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Old 02-12-2019, 02:49 PM
  #584  
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Hi guys
can someone provide me with the part number for the correct Festo pilot valve?
thanks
John
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Old 02-13-2019, 01:48 AM
  #585  
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Originally Posted by hemi View Post
hi guys
can someone provide me with the part number for the correct festo pilot valve?
Thanks
john
hgl-m5- qs-4

You will also need PAN -R - 4 - XO high pressure, tubing.

d

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Old 02-13-2019, 01:58 AM
  #586  
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Originally Posted by Auburn02 View Post
Thanks fellas, that's kind of what I was thinking too but wasn't sure if I was overthinking it.



David, can you clarify what you mean about they are near the bending point?

How far out on the stab are others mounted? I'll search this thread for any more pics of other setups.

Now, where to get 12mm pultruded CF rod and quick...
The shaft is supprted in the stab by the tube. Inside the fuse it is also supported by another tube. At the junctioin of the tubes is where the stress from vertical flexing, /loading, of the stab. Is concentrated. As your shafts have holes drilled near here they have weakened it where it needs to be strongest.

Probability is the rod wont actually bend ( pultruded CF is very resistant to bending) but could merely snap.

Unlikely but.......

D.
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Old 02-13-2019, 05:24 AM
  #587  
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Thanks David for the quick response.

Im still waiting for my pump and valve from HP Tech but i have another question about the hydraulic system. The old system used a controller to operate the pump. Does the HP Tech pump us a controller as well. If so is it the one that came with the kit. Mine is the original unit
thanks
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Old 02-13-2019, 05:37 AM
  #588  
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My HP pump came with an electronic controller with a small pressure sensor vessel, which has an air precharge of max 10 bar.

I believe the new units are all integrated, its a complete unit and uses a brushless motor. I have had one on order for months.

I have been working on my Mig this morning. The Festo valves have held the gear totally solid with the model stood on the bench, and the air precharge , filled before Christmas is still instantly producing 10 bar as soon as it is switched on !

David.

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Old 02-13-2019, 06:25 AM
  #589  
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Originally Posted by David Gladwin View Post


The shaft is supprted in the stab by the tube. Inside the fuse it is also supported by another tube. At the junctioin of the tubes is where the stress from vertical flexing, /loading, of the stab. Is concentrated. As your shafts have holes drilled near here they have weakened it where it needs to be strongest.

Probability is the rod wont actually bend ( pultruded CF is very resistant to bending) but could merely snap.

Unlikely but.......

D.
Makes sense David, thanks again. I'll have new rods on order today, and will glue them into the stabs along with a single bolt in the further out hole as an anti-rotation pin.
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Old 02-13-2019, 08:20 AM
  #590  
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David
Thanks for the info. Good to know they can be a little slow fulfilling orders
John
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Old 02-14-2019, 06:35 AM
  #591  
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When I pulled the stab servos, they were mounted into this 1/8" layer of ply that was quite gnarled up and appears to have had the screws run in and out of it a couple hundred times as there was almost no bite left. First I added some 1/4" ply blocks to the backside of that 1/8" ply:


After that I realized that those original servos were pretty well bottomed out against the fuselage side. The new A700s were a hair taller plus I don't use the rubber grommets as the old servos had, so these will sit deeper in the mounts. Had to add an additional 1/8" ply to the front of the mounts, then mounted with #6 x 1/2" screws. The fuselage will fail around the mounts before the mounts fail.


Mocked up with the stab rod horn to verify alignment - new rods are on order from ACP Composites.
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