lesbian horse wrote:I don't think they will do high psi. Rafts only need like 1-2psi.
Yeah, there was a guy marketing that type of pump out at 3rd Ave last year. It will pump up a kite just fine. Looked like it would be relatively easy to make. Mostly PVC. I'd use aluminum tube for the shaft. I vaguely recall that it only pumps on the down stroke (which is my preference anyway). The secret is to make the plunger portion out of plastic. Then you have a thin piece of semi-rigid foam (similar to ethafoam) beneath the plunger. The foam fits more firmly to the side walls of the pump. On the down-stroke it pushes itself firmly against the plunger (forcing the air out the hose). On the up-stroke it flexes away from the plunger exposing vent holes in the plunger.
You'll also need to make a flapper valve at the hose junction. I can post pictures of how I did one if necessary.
Having said all that, I prefer the BST-12 electric. Haven't had my hands on a manual pump since.