Waterproofing a mast


does anyone have a recommendation on how to keep water out from a hollow Aluminum mast?
I’m currently using an Axis mast and after drilling the hole for the motor cables it’s of course not watertight anymore.

Is there some kind of spray foam I can fill the mast with that does not soak up water?


2k PUR foam would do it but is it really necessary? The anodization will be inside the mast too.

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I used Permatex sealant to seal where the wires enter and exit the mast. Messy but seems to work well.

This is what I used

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I did this method. Trun it upside down so the cables that go into the board face the floor and fill the first few inches at the bottom of the inside with 2 part silicone like smooth on

Do you have a photo of the technique? I’m having a little trouble visualizing what is upside down orientation :grinning:

The permatex stuff works well and is also so possible to remove and cleanup redo in case of rebuild. Its a gasket maker silicone. No leaks in my build with it.

Advantage of this is its easy to pour down the mast and also easy to remove


Thanks for the illustration.
I didn’t have that option on my Gong V2 mast as there is a rubber seal inside where your pour IN location is. In addition they use an aluminum piece that fits to the fuselage at that location that has very tight tolerance so the pour in liquid might hamper that if there was any residue.

The Axis mast is likely different so my experience may not be applicable.

I’m not sure if @t-dub-maui is after total water seal but if he is wouldn’t water get in where the motor wires enter the side of the mast with your method?

I’ve done the same with my Gong V2 mast.
The rubbers are removed easily with a pair of pointy pliers.