Cauking Help

I am building a 17 foot twin cockpit runabout. Where I’m stuck is caulking the decking. It is Mahogany planked that I have stained and have eight coats of varnish on it. Now I started to caulk it and two things are happening. The first thing is it is shrinking a lot and second is when I pull the tape off (caulk is Still soft) it is leaving little peeks and it’s rough. How do you get those beautifuly smooth white caulk line without messing up that nice varnish job??????
What type of caulk works the best?

 

I have a similar question but with regards to teak decking instead of mahogany. What caulk works well with teak?

 

Use the caulk that is made for decks. The way to get really sharp edges is to caulk and then sand.