Do yourself a favour and buy a Lee Valley (Veritas in Australia) plane/chisel sharpening jig, a fine-grit diamond sharpening plate and an ultra fine stone (or similar sandpaper). A little practice will produce consistently sharp edges. It is those edges which will do the most to solve all of your other planing challenges like chatter and tear out.

Stanley and others make slightly cheaper jigs which work well, but the Veritas is the best I have found for the price.

For the very hard timbers - unlikely to be used much in kayaks but common in Oz - the very steep cutting angle on HNT Gordon planes produces exceptional results. One of them may be a worthwhile investment if you have included significant amounts of serious hardwood in your boat. The best bit is they double as a scrapping plane by simply reversing the blade.

Cheers, Tony Bligh