Skeleton Crew

Installment 28 of Project Mako Relaunch

We're ready- time to regenerate bone structure in this old Mako. Last week we kicked the project in overdrive ; we needed to laminate enough hull strength in time for a very important visit. This next phase brings in a couple of expert stringer installers. Scott Lewit and Mike Canfield will be joining us from Prisma Composite Preforms in Melbourne, FL. They're here to guide us through installing stringers.



Scott and Mike are specialists in installing foam core stringers. Prisma supplies foam core composite hull reinforcements to many of the major OM boatbuilders. This modular boatbuilding concept is drawing the attention of many recreational boat restorers like ourselves. They offer a whole line of foam core composite reinforcements to structure any composite boat. The guys arrived at the JD workshop Tuesday afternoon. By mid-day Wednesday, using their prefab components, we completely installed new stringers and stiffeners in a few hour's work. It was easy. We're sold on it's value- huge savings on time and labor.



First step is to dry fit the stringer sections to the hull. The preform hull lumber ships in 4 ft lengths, so we butted several to gauge the run. We looked foremost at the deadrise angle. The stringers come in 3 deadrise options, 15°, 18° and 26°. Ideally stringers should be perfectly perpendicular. This presents a squared horizontal top to rest the deck on. The Mako 19 is different. Instead of landing the deck on stringers, she was built with a suspended deck. A suspended deck floats above the stringers through it's own support structure. Since the deck doesn't land on the stringer, a few degrees of deadrise slop is no problem in our new stringers.



Most boats will require some deadrise angle fine tuning. Mike showed us how to square up the stringers to vertical. Option one, Prisma offers deadrise converters, angled shims the stringer sits on top of to make it plumb. The other option is to shave away foam til the stringer sits perfectly up and down. To measure the cut, simply tip the stringer until the top measures level (using a combination level) and measure the gap. Mark this height on opposite side and shave that material off. Now that you have a mark, the easy way cut this:

scribe the gap height on the longer side of stringer, the side in contact with hull

draw this height the length of the stringer

then score the fabric with a razor knife, peel away cloth tabbing

next, looking at the cross section, draw a line from mark to opposite bottom corner

cut the foam with a hand saw.

You are left with a perfectly level stringer. Shaving foam will shorten stringer height, reducing structural support, so be sure you have height to spare. If not, the angle converters are a better option.






If there is a sharp deadrise, keeping the stringers in place can pose a challenge. We cut some boards as spacers in advance. These will maintain the stringer spacing and we will suspend weight on them til cured.

Cutting the stringer to transom angle

1. measure the stringer distance. We left the full length 4' sections intact up forward and opted to shorten the aft stringer.



2. After marking the distance, cut the cloth face with a utility knife



3. Also cut the tabbing quadraxial cloth with scissors



4. Use a hand saw to cut foam



5. Place stringer against transom and measure the gap. Most transom angles will see the gap up top. Mark that measured distance on the BASE of the stringer to make the angle agree.




6. Connect the dots from top corner to the measured distance




7. Again, cut first with the razor knife and peel away all attached fabric.



8. Finish the cut with a hand saw

The resulting angle should fit flush to the transom.


All prep work complete, it was now time to wetout. We installed hull stiffeners first, and returned to the stringers next day. Prisma offers a great carbon topped hull stiffener that adds significant hull strength while adding very little weight.

We prepped the area with a light 36 grit sanding to add tooth and shake off any amine blush.

On the laminating table, TJ and I wet out each 4' piece with West System 105 and 206 Slow hardener and passed them into the boat. Mike set the stiffeners in place and chased bubbles with a roller. He kept a small batch of epoxy on hand to saturate any remaining areas. Where the stiffener pieces butted together, we overlaid tabs of quadraxial cloth.

We finished the wetout in less than an hour. We'll cap the forward ends and tab the back into transom sometime later. For now, time to let the stiffeners cure and come back tomorrow for stringers.