catamarans sailing to windward



Can anybody help? I have a 25' Summer Twins which steadfastly refuses to sail reasonably to windward.
( I know gentlemen aren't supposed to!) I bought her last year and sailed from Hayling to Portsmouth.
She wouldn't sail close to the wind but I was expecting that from a cat. Tacking was difficult and I had
to backwind the genoa every time. After some renovation on the boat, I recently went out on the Solent
to get to know her foibles and she has definitely got some! I couldn't get anywhere near the wind and
precious little forward speed, so attempting to tack was hopeless. Downwind wasn't bad, but it all ended up
with the ignominious motoring back.
I haven't been sailing that long so I'm probably making some
fundamental errors. The renovation included new sheets, reefing lines and a new mainsail bag.