Does the frame get wet?

[stroutmail]

Curious whether a cub with floats gets wet enough that frame under covering should be checked for rust more often?

10 year old cub with rust?

[Mark Keneston]

Curious whether a cub with floats gets wet enough that frame under covering should be checked for rust more often?

10 year old cub with rust?

All tube and fabric aircraft should be checked or rust corrosion. Moisture accumulates and more if it lives outside, more still if its on floats. Just do a thorough inspection or find a knowledgeable party to do it. Does it have seaplane drain grommets in the wings, tail and fuselage belly? It should. Thanks Mark

[usjetjock]

All tube and fabric aircraft should be checked or rust corrosion. Moisture accumulates and more if it lives outside, more still if its on floats. Just do a thorough inspection or find a knowledgeable party to do it. Does it have seaplane drain grommets in the wings, tail and fuselage belly? It should. Thanks Mark

"Has there been a factory service bulletin about seaplane drain grommets?" I had a serious issue about this, because on my plane a 2015 model, there are no drain holes anywhere. Thanks USJETJOCK"

[Mark Keneston]

"Has there been a factory service bulletin about seaplane drain grommets?" I had a serious issue about this, because on my plane a 2015 model, there are no drain holes anywhere. Thanks USJETJOCK"

All airframes are subject to moisture if they are not kept in a hangar and if they are not flown regularly. All cubcrafters aircraft have limited drain holes in both the bottom tail of the fuselage, the bottom of the rudder, and a few in the trailing edge of the wings and tail feathers. Seaplane drain grommets are install on request for an extra charge. A service bulletin would not be necessary for this. You can indeed add drain grommets or even drain holes if you choose by using a smaill tip soldering iron as we do at the factory. Can you please share more info about your particular plane and the situation thus far. Maybe we can help with more info also. Thank you for reaching us.

[Helenawe]

The steel tube members of an aircraft equipped with floats should be given par*ticularly close ~xamination.

It is possible for water to enter the interior of these members, allowing rust to form on the inside of the tubes while the exterior appears to be in good condi*tion. The best way to check for this condition is to have small holes strategically drilled in the tubing.

If water is present, it will run from the holes. It is sometimes desirable to have small pieces cut from critical tube mem*bers in order to obtain positive knowledge of the condition of the tube interiors.

[ZackJones]

The steel tube members of an aircraft equipped with floats should be given par*ticularly close ~xamination.

It is possible for water to enter the interior of these members, allowing rust to form on the inside of the tubes while the exterior appears to be in good condi*tion. The best way to check for this condition is to have small holes strategically drilled in the tubing.

If water is present, it will run from the holes. It is sometimes desirable to have small pieces cut from critical tube mem*bers in order to obtain positive knowledge of the condition of the tube interiors.

Thanks so much for the tip to drill small holes - very easy and effective!

[Mark Keneston]

Water does not enter the tubes. The tubes on our planes are sealed. If you drill holes, you destroy the integrity of those tubes making the airframe unairworthy. Those would need to be re welded to be airworthy, not a good plan.

You should be able through a thorough inspection on the exterior to tell if water has been present and done damage. With drain grommets (that are clear and open) the moisture should escape. Most older Cubs show moisture and or rust at the tail post and lower longerons at the tail post. This is an annual inspection and maintenance item. Our Cubs have a powder coated airframe to help reduce rust. My J3 on floats restored in 2007 has an epoxy primed airframe and last year was the first time I noticed rust on the tail post section. I wire brushed it and primed it.

Drilling would be a very last resort.

[Andy]

Water does not enter the tubes. The tubes on our planes are sealed.

Perhaps you are unaware that several of the frame tubes have threaded holes for fasteners. These tubes are not sealed. Look at how the the belly panel and the seat pan attach to the frame tubes. There are more threaded holes in frame tubes between the instrument panel and the firewall. (Personal knowledge of my FX-3 that I maintain and inspect.)

I'm not saying that water will enter the tubes at these threaded holes but those tubes are certainly not sealed.