Internal Blocking

Tutorial: Internal Blocking

The purpose of the internal blocking is to support the fin system, leash and vent plugs, and any tiedowns or accessories you may decide to build into your board. Internal blocking can add significant weight to the board if materials aren’t chosen carefully. Some builders use paulownia or balsa for internal blocking and some use high density EPS foam. Watertight compartments for extended touring (if desired) should be finished prior to the internal blocking. Deck hatches should have appropriate support blocking attached to the underside of the deck.

Five fin surf SUP

The photo below shows the internal blocking for a five fin surf SUP with the vent and leash set blocking. Note the notched block on the lower right of the photo which is the air path for the brass vent.

Getting the blocking “right”

Careful layout and planning will avoid time consuming and frustrating problems. Selecting the fin system, vent and leash sets you are going to use early in the process is critical to “getting it right”. I’ve found Robin Mair/Gearbox Surf to be an excellent source of information about fin placement for surf SUP’s You can also check out and

Carrying grips for SUP’s 

Carrying grips for SUP’s care be as simple and attractive as a block of wood machined to for a hand pocket. The block is glued into position along with the other internal blocking. Off the centerline grip installations suit many builders and doesn’t disrupt the integrity of the spar. The fore and aft balance point should be determined after the fin and vent/leash blocking is installed.