dose any one know why challenger 40 sailboats leak at the mast?

Most sailboats with a keel-stepped mast have a tendency to leak a bit at the mast partners. It is a large hole with the constantly flexing mast through. Also, most mast extrusions have a track or grove that is part of the structure. All of this is difficult to seal against water. Also, water can intrude through mast fittings and seep out through others. You can seal the attachment points with 4200 or other marine-grade sealants.

Water will also travel from entry points at deck fittings and show up some distance from the fitting. Check all your deck fittings for good fitting to deck integrity. If necessary re-seat any that are suspect.

There are some good aftermarket products that do a very good job of sealing the partners. Boots and fillers and combinations of both.

Check with these guys: http://rigrite.com/Spars/SparParts/Mast_boots.html

They may have a specific solution for your boat.

There are generic collars and sealers available also;

Spartite is a spendy but very effective product.

http://www.spartite.com/Default.aspx?SiteID=3

A mast boot is the easiest solution to the problem, assuming the leak is coming from the mast. Water may be running down the mast's interior. Water may be coming from some unknown part of the deck and flowing towards the mast step. Suggest getting a moisture meter to check parts of the deck to see if the fibreglass core is wet.

Look around the mast for cracks, or breaks in the seal. Then if you find some re seal them. Or you just bought the biggest crap heap on the sea..j/king but at any rate. Check from underneath if at all possible for signs of breaks.

Check the track for the main sail guides some 1 might have had it apart and didn't seal it so water will follow down the track past the cover to the headliner>>>>

reseal over seal.