louisut Posted September 9, 2019 Report Share Posted September 9, 2019 (edited) Earlier this year I joined a Mooney Rocket partnership, though only recently have I begun flying it. The performance is phenomenal, especially compared to the Piper Cherokees I came from. As part of my checkout, I flew a 900nm trip in an afternoon and cruised easily in the O2 levels--something unimaginable to me only a few months ago. With the Pipers, I was very involved with the maintenance, and I've continued to be involved with the Mooney. We've had several large mx issues since I've joined, and though I'm fortunate to work with an A&P who is both meticulous and communicative, his time is limited, and so I'm hoping the collective experience of MSers will fill in my knowledge gaps. The latest issue is with the engine truss. One of the beams close to the turbo was corroded. If I understand correctly, the heat of the turbo corroded the paint, which opened the truss to additional corrosion. It's been cleaned off, but there's some question whether that section needs to be replaced completely. My A&P has contacted Rocket Engineering to see whether we're still within guidelines of AC 43.13-1B (where a 10% reduction in material is acceptable). In the meantime, I'm looking to learn more about it, how to avoid it, etc... in general, anyone else's experience with this. Thanks! Edited September 10, 2019 by louisut Quote Link to comment Share on other sites More sharing options...
Yetti Posted September 9, 2019 Report Share Posted September 9, 2019 what ought steel wool did you use to polish it out? Quote Link to comment Share on other sites More sharing options...
carusoam Posted September 9, 2019 Report Share Posted September 9, 2019 Welcome aboard Louis. Great pics to start with. and... by the way... Paint doesn't corrode... but it can be heat sensitive... The challenge with putting an insulator on there it is hard to inspect the covered part... Rocket Engineering May have a solution for a heat shield in that area... Having an engine mount serviced or rebuilt is pretty easy... there is a service for that... The pain is removing the engine, then putting it back... As Yetti may have implied... putting scratches in a metal surface opens it up to stress related cracks and further crack propagation... Always follow proper procedures... don’t guess... That device is holding up hundreds of pounds, and holding onto hundreds of horses. It’s not just bicycle tubing... going 20mph... This is only PP thoughts... I sent out an engine mount to be prepped, inspected, and painted once... don’t be afraid to do something similar... it is important. Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Yetti Posted September 9, 2019 Report Share Posted September 9, 2019 Just got through reading the SB208 for cabin tubing. 10. If a tube has ex te rior sur face cor ro sion that can not be pol ished smooth with “00steel wool” or can not be pol ished out within 10% of wall thick ness in lo cal ized ar easwith the cor ro sion cu mu la tive length not to ex ceed 10% of the to tal length of thetube, and the cu mu la tive cor ro sion not to ex ceed 25% of the cir cum fer ence of this10% of the tube length. Re fer toFig ure S.B. M20- 208-2 for ta ble of Part Num bers vs. Out side Tube Di ame ter (O.D.)and mini mum wall thick ness for re place ment tubes Then they give dimensions for each tubing. I would start there. http://www.mooney201.de/files/M20-208B.pdf @carusoam said there are shops that will fix yours up with a nice painted one. Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted September 9, 2019 Report Share Posted September 9, 2019 You could insulate it by wrapping it with header wrap than lock wire to hold it in place. You should remove it for inspection at annual and replace it with new. One roll should last about 10 years. You could also try fire sleeve put on the same way. The header tape will take a higher temperature then fire sleeve. The fire sleeve looks more aircrafty. Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted September 9, 2019 Report Share Posted September 9, 2019 You need to defer to Rocket for ICA on that engine mount, not Mooney. 1 Quote Link to comment Share on other sites More sharing options...
louisut Posted September 9, 2019 Author Report Share Posted September 9, 2019 (edited) I'm not sure what he used to get the corrosion out. He said it was deep; you can see the gap compared to the ruler in the first pic. The wall thickness is what we're trying to find out now. He's contacted Rocket so it should in compliance with their ICAs, if any. If it's outside guidelines, the obvious option would be to send the truss out for overhaul. It'd be expensive, but that's the benefit of a four-way partnership I guess. The second option may be to have a metalworker replace that section in situ. While I'm not opposed to this, I'd be more comfortable about it if someone had done it before. If it turns out to be good as-is, I want to make sure we maintain it properly so that it'll last at least until the next overhaul. Edited September 9, 2019 by louisut Quote Link to comment Share on other sites More sharing options...
carusoam Posted September 9, 2019 Report Share Posted September 9, 2019 You may be able to find proper methods of measuring the tube thickness... In some cases a steel(?) ball is sent inside the pipe and the measuring is done from the outside..? An example of a welding service.... https://awi-ami.com/service-information https://awi-ami.com/aircraft/mooney/m20.html They also rebuild exhaust systems... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
kortopates Posted September 9, 2019 Report Share Posted September 9, 2019 That sure looks like its worn well beyond the limits of 10% of the thickness of the tube which is .065" thick on a my Mooney K model, but you'll have to verify what the thickness of the tubing used by Rocket in case its different. But if the wear is say .01" now, you know there is no hope. Its not terribly expensive to repair the mount, its the labor to pull off the engine and put it back on; probably with new lord mounts that get's pricey. But avoiding this is straight forward, keeping the tubes covered with paint by cleaning up rust and exhaust leak damage at every annual and touching up with paint etc. I also use aluminum tape to protect it at the engine mounts location area where mine got the most heat damage previously. 3 Quote Link to comment Share on other sites More sharing options...
Yooper Rocketman Posted September 9, 2019 Report Share Posted September 9, 2019 This is what I used on mine for 18 years, changing it out every couple years and reinspecting the tube. I made sure I had a good layer of paint on it before installing the tape too. https://www.aircraftspruce.com/catalog/appages/alum_foil.php?clickkey=72494 Tom (Prior 1800 hour, 18 year Rocket owner) 2 Quote Link to comment Share on other sites More sharing options...
louisut Posted September 10, 2019 Author Report Share Posted September 10, 2019 (edited) For posterity, Rocket Engineering indicated that the tubing in the truss is 0.058", and so the 0.015" already removed is definitely outside the 10% guideline. Our A&P is bringing in a welder to fabricate and repair the affected section. Rocket has signed off on this plan. Overhauling the truss starts at $11k ($4k for the truss + 80 hours labor to r&r the engine), so we're starting small first. Edited September 10, 2019 by louisut 2 Quote Link to comment Share on other sites More sharing options...
philiplane Posted September 10, 2019 Report Share Posted September 10, 2019 This is well within the capability of any A&P familiar with 4130 tube repairs. AC43-13 has guidance for fabricating and welding an overlay type reinforcement. 1 Quote Link to comment Share on other sites More sharing options...
M20F Posted September 24, 2019 Report Share Posted September 24, 2019 On 9/9/2019 at 11:47 PM, louisut said: + 80 hours labor to r&r the engine), so we're starting small first. 80hrs to pull and replace the engine seems exceptionally high to me. 3 Quote Link to comment Share on other sites More sharing options...
louisut Posted September 26, 2019 Author Report Share Posted September 26, 2019 (edited) The weld repair went well. The rest of the frame was cleaned up and the whole thing repainted. Next time it's out we're going to investigate ceramic powdercoat. I believe the split sleeve splice process is the same for any tubing repair. Attached are some pics of the progress. Should be better than new now. before: Edited September 26, 2019 by louisut Quote Link to comment Share on other sites More sharing options...
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