Found this tip on an IBM website. If you want to convert all http requests to https requests (useful for secure-ish sites), use the following snippet in your .htaccess file:
RewriteEngine on
RewriteCond %{SERVER_PORT} =80
RewriteRule ^(.*) https://%{SERVER_NAME}%{REQUEST_URI}
Found this tip at : http://www-1.ibm.com/support/docview.wss?rs=177&context=SSEQTJ&uid=swg21114864