Mast: most loaded point

I am building a new mast by sleeving two stock sections together to make a single long section (about 25 feet). Is there any section of a masthead rig (no spreaders) that is less loaded, and therefore a better place to put the sleeved joint. That is, is the mast more loaded at the base, the head, or the middle - or are loads spread evenly?

The boat is a Wharram Tiki 21. The standard mast is 21' x 4" x 0.125 aluminum tube. Available stock tubes are 20', and I am increasing the mast height by about 4', so there will be a 20' stock length, plus a 5' extension joined with a sleeve.

Many thanks,
Roger

 

I would put the four foot section at the base with a substantial sleeve. That gives you extra strength where the boom and other hardware attach and keeps the weight aloft to a minimum.

 

My opinion: the higher you make the union, the better. But also make sure that the distance from the joint to the insertion points of the stays and the shrouds is as large as possible. In short: add the new portion of the mast to the top of the old one.