Legal to Fly a J-Model without Wheel Covers?

[A64Pilot]

Be sure to electrically isolate the part from the aluminum, Carbon fiber in contact with aluminum will cause galvanic corrosion, then be sure you put anti-chafe tape between this part and the wing as carbon fiber can really chafe into aluminum badly.

I’d recommend fiberglass myself, as there is no requirement for excessive strength fiberglass will be fine and not have the corrosion issues and while it won’t be as strong there won’t be much weight difference. I know Carbon fiber looks cool naked and marketing people have really sold it, but it has downsides on aircraft

https://www.corrosionpedia.com/galvanic-corrosion-of-metals-connected-to-carbon-fiber-reinforced-polymers/2/1556

[A64Pilot]

On 12/21/2024 at 6:38 PM, PT20J said:

I don't know what would be required but Don Maxwell told me he put them on some J-bar airplane (maybe an F, don't remember) and the air loads were so great it was really hard to raise the gear.

School in Tx that I got my Commercial in 30 years or so ago had removed the lower fairings, I asked why as the school prohibited the Mooney’s from landing on anything but pavement. I was told it was for maintenance reasons, so I went and asked the Maintenance chief, he said that the factory had told him these AT aircraft as trainers had of course abnormally high gear cycling and the loads imparted on the gear from the doors caused wear. Maybe it was BS who knows, maybe the real reason was they didn’t want to R&R them for tires and brakes but the wear claim seemed logical to me.

That’s why now on my Mooney I don’t drop the gear until I’m in the white arc, it just seems reducing the strain is worth it.

Anyway when I changed tires I left them off and at the slower speeds I fly didn’t notice any difference, but I put them back on anyway.

[MooneyAcolyte]

Be sure to electrically isolate the part from the aluminum, Carbon fiber in contact with aluminum will cause galvanic corrosion, then be sure you put anti-chafe tape between this part and the wing as carbon fiber can really chafe into aluminum badly.
I’d recommend fiberglass myself, as there is no requirement for excessive strength fiberglass will be fine and not have the corrosion issues and while it won’t be as strong there won’t be much weight difference. I know Carbon fiber looks cool naked and marketing people have really sold it, but it has downsides on aircraft
https://www.corrosionpedia.com/galvanic-corrosion-of-metals-connected-to-carbon-fiber-reinforced-polymers/2/1556

Thanks, A64pilot. I‘ve been thinking about this and there is an excellent video on the topic by the people who build the DarkArrow:

Since the wheel covers are bolted on with steel bolts, all I’ll have to do is making sure no metal-carbon contact exists where the holes are drilled. That can be done by an extra layer of resin.


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[A64Pilot]

13 hours ago, MooneyAcolyte said:

Thanks, A64pilot. I‘ve been thinking about this and there is an excellent video on the topic by the people who build the DarkArrow:

 

Since the wheel covers are bolted on with steel bolts, all I’ll have to do is making sure no metal-carbon contact exists where the holes are drilled. That can be done by an extra layer of resin.


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Mine when retracted chafe against the wing and have metal to metal contact, that might could be handled by teflon anti chafe tape which probably ought to be there anyway.

On boats we would use plastic washer for bolts and often cut shims from a milk jug if the carbon touched aluminum as insulators.

Deal is just be sure they are isolated, the corrosion is surpassingly aggressive if not.

[MooneyAcolyte]

16 hours ago, A64Pilot said:

Mine when retracted chafe against the wing and have metal to metal contact, that might could be handled by teflon anti chafe tape which probably ought to be there anyway.

On boats we would use plastic washer for bolts and often cut shims from a milk jug if the carbon touched aluminum as insulators.

Deal is just be sure they are isolated, the corrosion is surpassingly aggressive if not.

Thanks for sharing your thoughts. I am now convinced that I underestimated the chafe-problem. So, here is my approach: the contact areas will ALL get an extra resin layer, I will clear-coat the whole part, AND I will add anti-chafe teflon tape. If all goes well, I will be able to install the carbon covers before the summer. I will report here on any galvanic corrosion problems that show up before the end of the year.

In general, I am very grateful for the community discussion here, which can only help to improve the product. My next report will be on the quality of the port-side outer shell after resin infusion.

[A64Pilot]

I think the chafe problem can be very effectively mitigated by teflon tape, however it has to be replaced when it comes off, some I’ve had stay on over year even when oil soaked (nose gear door area) and some in clean areas come off in a month.

What seems to help is throughly clean the area with acetone, I think it also softens the paint, then apply the tape with pressure getting it very warm with a heat gun.

I’ve considered bonding teflon tape to thin VHB tape and bonding the VHB to the airplane but haven't. 

There is no galvanic corrosion problem with fiberglass 

[MooneyAcolyte]

Alright, the first part is done (starboard, before finishing, see pictures). Quality-wise, I am now about 90% there (some minor cosmetic flaws in the weave on the visible side and some "dry" spots on the edges, ~1mm misalignment of the inner and outer part). Tomorrow, I'll make a fit-check on the airplane, but am not very confident. Here's what I've learned:

1.) 4 layers of 250g/m^2 for each side (inner and outer) = 8 layers total is too thick (~2-3 mm) to mimic the aluminium sheet metal part, so I have to reduce to 4 layers total

2.) Even small misalignment when bonding the inner and outer shell leads to undesirable distortions of the final part.

I will make a better run with these lessons learned. It takes a bit longer, but I am confident, it is worth it.

 

 

[Slick Nick]

This is what the prototype process is all about! Learning what works and what doesn't. Great work so far!

[EricJ]

That looks like good progress!

 

[MooneyAcolyte]

Fit check successful.


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[Slick Nick]

Well done mate! 

[MooneyAcolyte]

So, this is my final post on this topic. Today, I took the fitted carbon fibre wheel covers (officially "mid gear doors") for a test flight and found them to perform exactly like the originals - only they look pretty. I attach pictures of extended, half retracted, and retracted configuration during climb and cruise for the port and starboard sides. 
Thank you all for the valuable insights. In particular, the risk of galvanic corrosion was one that I otherwise would have overlooked.  In general: if you find it acceptable in your regulatory framework (like it is in EASA PART-ML), don't be shy to go for owner-manufactured parts. I did spend more than the $1400 I would have paid to replace my ONE cracked one with a 3rd-party part, but now I have two and they are quite nice.
'nuf said, here're the pictures.
 
 

[Slick Nick]

Those look great in my opinion, and you should really be proud of the work you put in! Well done!