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Discussion Starter · #1 ·
After breaking the carbon tube spar in the flying stab of my Revolto, I decided to make the repair stronger than the original. The stock 4mm carbon tube has a thin wall and easily fractures under a twisting load, which makes it a poor choice for a flying stab spar. Everyone I know who has a Revolto has broken this tube, with only one exception. Plus there are more reports of breaking the carbon tube spar on the internet forums.

The repair starts off with a 4mm carbon tube, but with a thicker wall. The original 4mm carbon tube had a .116" hole. The replacement 4mm carbon tube has a .078" hole, so the tubing wall is considerably thicker, which should increase the overall strength.

The center section of the carbon spar gets sleeved with 5" long piece of 3/16" brass tubing. The brass tube transmits 100% of the torque force to the flying stab halves, which should eliminate any torsion fracturing of the carbon tube.

The inner tubing guides of each stab half, plus the fuselage rod bearings will need to be drilled to clear the 3/16" brass tubing. The goal for the bearings is zero friction with zero slop.

With the beefed up flying stab spar, the next weakest point was the flimsy plastic control horn. Although mine hasn't broken (yet), I've heard of several that have broken, so it's getting an upgrade. A new control horn was made from an unused part of the fiberglass hardware that's included in the Value Hobbies epp foamies. This fiberglass sheet is 1mm thick, and way stronger than the original plastic control horn. The control horn was sandwiched on both sides with a couple of prop hub adapters that fit the 3/16" brass tubing just loose enough to allow thin CA glue to wick in there. This gives plenty of surface area for the CA glue to securely bond the control horn and the prop hub adapters to the brass tubing. This area of the brass tubing was roughed up with sandpaper to further strengthen the bond.

The original method of gluing the flying stab halves to the carbon tube calls for using CA glue. This requires extreme caution to make sure the CA doesn't accidentally wick into the rod bearing and turn the flying stab into a fixed position flying stab.

This time the carbon tube was inserted into one of the flying stab halves, then a thick bead of Foam Tac was laid on top of the exposed carbon and brass tubing. Then the carbon/brass tube was spun around about a dozen times, which pulled the Foam Tac down into the slot and spread it out. Once it was dry, this stab half was inserted into the fuselage bearings, along with the new control horn and the prop hub adapters. The control horn and hub adapters were then glued with thin CA onto the brass tubing in the proper position. Finally the other stab half was slid onto the carbon tube, a thick bead of Foam Tac was laid down on the exposed carbon/brass tubing, and the stab was spun around about a dozen times to spread the glue into the slot. The stab halves were carefully aligned and jigged into place, and the Foam Tac was allowed to fully dry.

The result is a flying stab with zero torsion slop, and a much stronger spar. Plus I'm really super excited to have my Revolto flying again! :drink:
 

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And with only a few weeks away before Clinton.
 

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Nicely done! Hope my small-diameter carbon rod inserted inside the original stock carbon tube holds up for a while; if it breaks, I'll be looking for this thread again lol. How were you able to get the original tube out of the stab halves? Wish Twisted would sell you a couple stab halves for replacement, so you didn't have to gouge out the old, broken tube...
 

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Discussion Starter · #5 ·
Getting the old broken tube out of the stab halves without destroying the stabs or plastic guides took awhile. Once the plastic guides were carefully surgically removed, running an xacto blade along the remaining carbon tube allowed them to finally break free from the foam stabs. Since they were originally installed with CA, it took some time and patience.

Twisted wouldn't sell me the stab halves, and wouldn't sell me just the plastic guides. Just to get new plastic guides required buying a complete hardware package that was about $30 plus shipping. A replacement carbon rod was only a few bucks, but it will have the same problem. In the end, this way turned out better anyway, and I already had the parts in my shop.

For anybody building a Revolto (are you reading this Straightup?) I would highly suggest doing this mod from the start. If nothing else, sleeve the original tube with the brass tube to stop the torsion fracture between the stab halves.
 
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Yeah, it's kinda bullshit that they won't sell you a part that is pretty likely to get broken--far more so than a kit with a standard stab and elevator. I want the 43" Crak Yak for when my 43" Edge dies, but will definitely be reinforcing that flying stab setup when building it...
 

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Oh, for those building the Revolto, or other Twisted plane with a thin ply firewall, DON'T waste money on the aluminum or carbon firewalls. Bought the aluminum one after no more CA would wick into my thrice-busted Veloxity firewall; that was stupic, because the aluminum one just bends--good luck straightening it without removing from plane. Carbon ones look nice, but $$. On both my Revolto and 43" Edge build, I just used one layer of heavy(6oz) fiberglass cloth and finishing resin on the back of the firewall. Trimmed and sanded edges once dry. I've smacked my Edge hard enough to rip the whole motor and firewall off the plane, and still (knock on wood) haven't broken my modded firewall :)
 

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Thanks Dave and Jeff :tu:
Bookmarked for when I build my Revolto this winter :tu:
 

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I wonder if the increase in stiffness makes it fly better. Flexing cant be good,my 202 wings flex and flop now,at med speed,guess i need to stiff them up some. Rub a blue pill on them real hard. :lol: :lol:
 

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Discussion Starter · #11 ·
The brass tube added 5 grams of weight, so technically the CG got shifted back. But inflight I can't say that I noticed it, so I didn't relocate the battery.
 

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This is my pro tip for all foamy build firewalls even my 2oz crak...............

cut the nose foam off of 2 fuselage pieces at point past the plywood inset. Buy some .010-.015" fiberglass/G10 sheet stock from Mcmaster or BVM Poly Ply. glue the plywood to the center of the G10/PolyPly Sheet using Ca and and cut extended X lengths all 4 directions. Then once plywood is glued into a completed fuse you just replace the cut off foam scraps really keeps a foamy nose from getting jacked or loose.

I even have Carbon sheet free but the G10 is much stronger as it flexes with foam.



 

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I repaired a one-time broken stab half with a smaller carbon tube shoved inside the original tube. That held, but a dorking then snapped the other side off clean at the fuselage bearing. Original carbon tube too splintered to use my carbon tube-in-a-tube again, so I had to cut out the original tube. I'm using 3/16 carbon arrowshaft, which I also use for pushrods with slippery nipples. Had to drill out the fuselage bearings just a bit, and ruined one of the stab plastic capture brackets, so I cut another out of 1/32 ply. Made a new control horn out of a Dubro HD control horn, shaved down a bit. Went to glue it all together last night, and lost the original stab capture bracket somewhere in the process, so I'll cut another out of 1/32 ply and glue 'er all back together.
 

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Discussion Starter · #15 ·
Sorry to hear you broke the stab again, but glad to hear that you rebuilt it much stronger than stock. :cool:
 

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That was my point on having a break point behind wing. Say going from 1/2 to 3/8 tube 2in behind wing,with the half behind wing beefed up so break would be mid tail. Smarter guys may have better plan. Same thing happen to my mojo 25,bitch to fix,but i did much as you did. Maybe wrap tube with small wire or string at wing to back a few inches so it wants to break behind wing.
 

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That's great info Jeff. Thanks.
 

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After gathering Bro information. My anal machinist skills kicked in. Over kill but sweet and tight setup. Had to share.
Hand Wood Cosmetics Hand tool Tool
 
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