Look for soft spongy timber anywhere that fresh water can get in. Cabin sides, where the cabin side meet the deck, deck edge behind rubbing strips. Dynel is good for keeping the hull dry from the outside but if fresh water gets inside anywhere the timber could be like weetbix in milk.

Dynal is only there to increase thickness on the barrier coat ie usually epoxy to keep the water out
it has no real strength so any cracks means timber underneath is moving
which often means water in timber or can be timber not stiff enough hence movements
where cabin side join deck and cockpit floors often cracks due to movement not water

Aside from the construction. A dynel-sheathed, or any, timber boat would not be an ideal first boat versus a plastic fantastic. My 2c.

Check out the Defiance Thread in here and check the pics

ltimber boat sheathed in dynal and epoxy

As mentioned earlier there's stacks of GRP boats on The market and cheap.
A lot of carvel planked boats have been fibre glassed,( layed up with chopped matt and resin of your choice) that lessens the maintaince at the expense of adding more weight. But that's not Dynal that's more for cold moulded or ply, abrasion resistance and as Lydia said adding to the water proofing membrane thickness