Stringer Appeal

Installment XX in the chronicles of a Mako classic restoration

We are now ready to make some progress with stringers (longitudinal reinforcing beams on the hull.) The original stringers were marine plywood covered in a heavy fiberglass woven roving cloth and wet out with polyester resin. Holes called "limber holes" were cut to allow water to drain to the bilge. These vintage limber holes are a horror show. A hole saw cut through the beam left exposed wood core. Water migrated in and rotted these areas. The rotten core shows black through the fiberglass. Notice the cracked areas.

These beams bear the brunt of force when pounding through waves. Hard spots and rotted core spell failure.


To remedy this, our task is to grind these stringers off and replace with new. Rotten core has minimal strength and must be extracted. Spot repair and/or sistering in stringers supports is the easiest route with least time and expense. We're going for the gold- grind the old stringers flush, then replace with foam core stringers. We chose these pre-fabricated stringers by Prisma. Prisma Composite Preforms come in complete sections, ready to wet out. The fiberglass fabric is already bonded to the foam. Just bed in place then wet out.







To spec out the stringers, we carefully measured and snapped extensive pictures of the current hull stringers. Measurements should include:

• angle of deadrise (angle of the hull to perpendicular)
• length of each stringer
• depth of each stringer
  

We then emailed this info on to the folks at Prisma for technical consultation.


Without stringers, this boat will be loosey goosey. One concern with the upcoming phase will be to maintain hull shape. We must support the hull prior to removing the stringers to minimize distortion. Temporary braces across the gunwales and supports under the hull should maintain hull shape as best possible.

Commonly decks rest directly on hull stringers. Notice this boat has separate reinforcements for the deck, which floats above the stringers. (see 2 remaining nubs in middle) We have the option to replicate this or just mount directly on stringers.

This perspective shows the taper of stringers meeting the rise in the bow.

Thanks for joining us, and please check back for more.