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| T-18 Serial 649 N587 Restoration http://t18.net/thorpforum/viewtopic.php?f=36&t=8814 |
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| Author: | Hagle347 [ Wed Feb 07, 2024 11:09 am ] |
| Post subject: | Re: T-18 Serial 649 N587 Restoration |
There are 2 items of concern on the 'bob weight'. The weight itself should be sandwiched between the angle stock. AND the part should be straight - not 'adjusted'. Both point to the collar on the stab being installed at the wrong angle. I've seen that on another Thorp I was involved with on a much smaller scale . The result of this mod will not allow you to get the full and proper angle of up and down horizontal stab movement . That also negatively affects aircraft handing. - With regards to the front spar shims....were the rear spars shimmed as well? Keep posting and asking questions - We'll get it correct! |
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| Author: | James Grahn [ Wed Feb 07, 2024 12:03 pm ] |
| Post subject: | Re: T-18 Serial 649 N587 Restoration |
I think it’s worth saving!! But I would return it to plans configuration. I’m not an engineer, but I can tell you that unintended consequences often happen with even minor mods. Those are not minor mods! Terry is right, the 510 might have been installed at the wrong angle. Not sure how to fix that. I would move the wing back to the normal position. With a fixed pitch prop, you should be right in the sweet spot of the CG. Cubes |
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| Author: | James Grahn [ Thu Feb 08, 2024 12:49 am ] |
| Post subject: | Re: T-18 Serial 649 N587 Restoration |
Awesome! You do quick work. Cubes |
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| Author: | fytrplt [ Thu Feb 08, 2024 10:17 am ] |
| Post subject: | Re: T-18 Serial 649 N587 Restoration |
A quick check of your stabilator and the placement of the 510-1 bracket may tell the tale. The 510 is to be installed 14 degrees 2 minutes slanted up from the horizontal axis of the stab. A not so uncommon mistake of the early builders was to install it at right angles to the stab. Many early builders were building ahead of John Thorp's final release of drawings. Several were being built in the Atlanta area and even had round fuselages. The fatal accident that resulted in the redesign of the horizontal tail was caused the bracket installation mistake and subsequent fix. The builder drilled out the rivets on 510-1 and correctly positioned it and redrilled the holes and re-riveted it. He essentially perforated the tube spar. A sharp pull up after a highspeed pass was all it took to fracture the spar. The spar doubler, redistributed bobweights, and the oh so important stainless steel straps on the tab were a result of this accident. If you make your way to Sun 'n Fun this year, I would be glad to meet up with you and show you my finished plane and the one I have under construction. I am based in Lakeland Florida. |
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| Author: | Rv3maker [ Sat May 11, 2024 10:55 am ] |
| Post subject: | Re: T-18 Serial 649 N587 Restoration |
PapaGolf, how is it going? Any updates? Keep us posted! I am going to start a project thread pretty soon myself . . . .let's keep each other in check! Rob |
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| Author: | PapaGolf [ Thu Jun 27, 2024 9:00 pm ] |
| Post subject: | Re: T-18 Serial 649 N587 Restoration |
RV3maker. Thanks for asking! Unfortunately my family and I were hit with a series of health issues that knocked down my ability to get the physical work done for a bit. Hopefully I’ll be able to pick up the rivet gun soon! In the meantime just for an update, the vacuum system and original instrument panel have been donated to a local High Schools budding aviation program. Some shopping and horse trading has landed me with a 10” Dynon Skyview system with the engine monitor for the Lycoming that’s still awaiting overhaul. I also picked up an efis-d10a that will make a good standby instrument. It came with the autopilot servos, although I had no plans for an AP, they’re compatible with Skyview so I guess I’ll have an AP! A Stratus ES transponder will replace the King KT76 mode C unit to fit the ADS-B out requirement. I have a stratux unit I’ve used for ads-b in. I’m going to experiment and see if it will feed the Skyview. Worst case I’ll have the data on ForeFlight for now. The only issue I have right now is what to do with the other stuff I have. I still have an ICom VHF radio, a Narco Mk12D with glide slope. And a KLN-89B IFR GPS. Oddly enough I’m considerings reusing them. I like the idea of having VOR/ILS and even though the Skyview has WAAS, the 89B is approach certified. I don’t have my instrument yet but I like the idea of being equipped in case I end up in the soup. I would eventually like to get a good navigator so I can fly a nav coupled approach but getting it flying and back through phase 1 is the priority. Engine wise, the O-360 was prop struck, 300 beyond TBO, and hasn’t been run since 2012 as best I can tell. The Carb wasn’t drained so it needs an overhaul. The dual mag is obsolete and several hundred beyond its 500 hour. The ignition harness is shot as well. That said I’ve been considering going with an EFI/electronic ignition system. I’m not excited about flyefii or system32 though. To that end, I’ve been bench testing a custom ECU with the goal of having a full sequential injection/ignition. The other two use a batch fire, wasted spark algorithm that leaves fuel sitting on the back of the intake valve and double fires every spark plug. The one that has an option for a redundant ecu apparently has a rather unnerving changeover if something happens. My sitting on the couch for 3 months design is based off the same FADEC that runs the Rolls Royce BR-710 engines on the G550s I take care of. Effectively two always on engine controls that take turns being in control monitored by a third that can vote one off the island if it starts acting stupid. So that’s the latest! I’ve taken the downtime to do all of the brain work. Drawing schematics, acquiring parts, and rebuilding the typewriter written flight manual. It’s been a lot of work but since I can’t fly right now anyways, I might as well build! I’ll keep an eye out for your project thread, always good to see what we’re all up to! |
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| Author: | James Grahn [ Mon Sep 08, 2025 11:21 am ] |
| Post subject: | Re: T-18 Serial 649 N587 Restoration |
I guess on that angled bracket is that it was used to lower the tunnel between the seats. It would be enlightening to see that tunnel. Cubes |
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| Author: | PapaGolf [ Wed Oct 28, 2026 2:31 am ] |
| Post subject: | Re: T-18 Serial 649 N587 Restoration |
Dear Diary, It took me way too long to dig through and figure all of this out but I think I'm at the end of the deviation list! I totally missed your post, Sorry Cubes! I was having significant difficulty visualizing things from the plans but finally came to the conclusion that yes the changes to the pitch control mechanism were likely to reduce the height of the tunnel. I have yet to determine how the change in ratios affect stabilator control but I'll get there eventually. Findings: (thus far) 1. Arm on the stabilator horn is approximately .75 inches short. 2. The Walking Beam is... different... and shorter by almost an inch from the upper to lower pivot points 3. The pitch pushrod is correct on the aft end, but the forward fitting was angled down as previously pictured. 4. The Stabilator Counterweight was angled up and mounted crosswise to compensate for the pushrod being raised. 5. The Control Sticks Sweep back and up like a helicopter cyclic, still not sure how thats going to fit. 6. Builder had modded cessna rudder pedals and brake cylinders to fit. The cockpit floor was not to print either to match the rudder pedals. 7. There was a Custom 10 Gallon Fiberglass tank which was removed by the previous owner to go back with a plans drawn tank. 8. Fuel tank mounts were changed accordingly. 9. Baggage Compartment Top was opened up at some point. Al angle was added to stiffen the area post mod. I like the openness but still need to eval the structure and go back to plan or call it good. It was flying like that but I have no idea how long, there are no entries in the logs about it but the added pieces do not appear to be "period correct" for the original builder. 10. Firewall at some point found 12 volts from the battery feed. Found a hole blown in it that was covered with red RTV and a piece of aluminum. 11. The wing is shimmed aft 3/8's of an inch. The wing fittings are of the correct dimension, still trying to determine if the forward or aft bulkhead is to blame. 12. Inertia Reels for the shoulder belts were screwed into the underside of the deck with no reinforcement. I couldn't imagine them holding up in an accident... 13. Panel was moved aft 5 inches but thats fairly common, it had a full steam gauge IFR setup. 14. The Roll Bar was not modded and is of original design. 15. Engine Camshaft aft lobe has a chip in the tip, caught right before failure! 16. #3 cylinder rocker boss cracked. 17. Landing gear has minor surface corrosion, hopefully a strip and some dye penetrant will confirm its all good. 18. Minor surface Corrosion on the web of the spar around the mounting holes. I think that will buff out though... All the big chonks could definitely use a surface pad and some fresh primer... Still need to borescope the stab for the previously mentioned CherryMax and Jo-Bolts holding the 510 bracket in place. Data sheets say they are technically stronger than AD rivets, just want to make sure there is no corrosion in there. Another issue is the builder installed an O-290, the Dataplate says O-290, the registry say O-290, the engine would say O-360-A1F6D if it had a dataplate. Also, the engine came with a CS prop. It had a strike on a taxi light and was removed, crank dialed good, and the owner went back with a wooden FP Sterba. My understanding is engines and props need paperwork filed to update the registration and airworthiness. Obviously that doesn't matter much now but something I may have to address before it flys again. To my understanding if you change engines or props there should be paperwork filed with the FAA and a phase 1 flyout performed. Nothing in the logbooks indicate that occured. All that to say, I think it would have been easier to start from scratch! I definitely haven't given up yet but boy has it been hard to keep going. I've been plagued with knee issues so hobbies, let alone flying, have gotten away from me. This did give me the time I needed for solid headscratching and a true audit of what I have sitting in front of me. The good side, I managed to get some great deals on avionics, Thus far there are two 10" skyview panels, one ADAHRS, Engine monitor, an AP control head and 3 servos, 2020 and 250 GPS sensors(2020 for ADS-B position) and Stratus ES transponder that are itching to fly! If it ever flys, its gonna be sweet.... |
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| Author: | Ryan Allen [ Thu Oct 29, 2026 6:05 pm ] |
| Post subject: | Re: T-18 Serial 649 N587 Restoration |
Someone once told me building (or rebuilding in your case) is a test of perseverance. You can do it. Keep at it. |
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