Best bet is the beach just left of the entrance to Walton Backwaters... sand, so less messy than in the Orwell..... nice and flat, no rocks, and gently shelving.....
I reckon the best in the area is the sandbank in the middle of the moorings just inside the Deben. There's nowhere I'd dry out a cat for work in the Orwell
As you come down the Orwell from Ipswich just after the bridge there are some drying moorings to starboard just before the entrance to Foxs.The bottom is hard here & last year I dried out on a twin keeler & scrubbed the bottom.I have to say this was not intentional as I was up front rigging a cruising chute for an impromptu race & my crew on the helm admitted he was not watching the sounder.No excuse as all matters are the skippers fault.We listened to the Test match all day.(It was a falling tide) & 6 hours before we refloated.I did raising & lowering of arms to the boats that followed us out of Ipswich & they cheerilly waved back.By the time one came over to try & haul us off it was too late.