You can never have too many clamps in the boatshop. Every job is a little bit different, requiring some innovating clamping methods sometimes utilizing trailers or other items in the shop to accomplish your task.
There are many varieties of clamps, but the most often used in my shop are bar clamps and pipe clamps. You can purchase high end brand names like Bessey and Jorgenson or choose bargain brands like Harbor Freight. I have some of each, and the inexpensive ones hold up just fine for jobs that aren’t too demanding.
Bar clamps in the 6″ and 12″ sizes are great for holding planks to battens and frames. 12″ and larger can clamp planks to each other on edge, but the more force you apply, the more the bar tends to bend – especially the cheaper clamps.
A better choice for power clamping is the pipe clamp. I like the orange Pony brand ones, you can get significant clamping pressure with them…..if you can find something to clamp to. In one case, planking a coverboard on a bow, there was nothing to hold the lower end of the clamp, so I wheeled a GrayMarine engine over on it’s cart and used that as a solid weight to create the down pressure.
While bottom planking, if you don’t have a helper, you can use the scissor clamp method using a couple lengths of scrap mahogany. Cut an “L” piece and bolt that to one end of the mahogany. Clamp the “L” to a side frame, allowing it to stick out of the boat a little. This leaves room for the pivot of the long piece without impacting the chine. Do the same for the opposite side of the boat. Using them like a scissor, you can block and hold pressure on the first few planks, holding them down to the inner bottom. A bar clamp keeps them in plank, letting your hands free to drill and screw.
As one can see, there are never enough clamps in the shop.