Internal Cross beam/sleeve clearance

Hi All!
The mast extrusion will be used for the 2 cross beams of the demountable cat. If I want to demount, I need to have sleeves that will be fixed on the movable part and will slide inside the fixed extrusion part of the cross beam. The question is how much clearance should should I have between the external sleeve all and the internal extrusion part? My guess is between 0.25 to 0.5 mm(0.5 mm to 1 mm total diameter).
Thank you all!

 

I'd want to use at least four times the clearance that you mention. Set it up too tight and galvanic corrosion will weld the parts in place so that you will play hell getting the parts seperated. If your boat is a day sailor that will be taken apart every day or two, then you might use closer fits. In any case the telescoping parts will need to be kept scrupulously clean and lightly lubricated. With close fits you may also encounter problems resulting from beam distortion or the presence of even a small dent or wound in the aluminum.