From beast to beauty, follow our reconstruction of a devastated Mako powerboat into a modernized beauty. TJ and Mike, two employees of Jamestown Distributors, will share their project as a sounding board for other kindred backyard/garage fiberglass boat restorers burning the midnight candle. Your comments are always welcome, be it advice, shared experience, constructive criticism or just good-humored verbal abuse.
With all the stringers laid in the hull, we had one last order of business to tidy up this installation. From outside the hull, Mike added some tie-in strips of quadraxial cloth.
To tie the stringers into the transom, Mike cut some 14 inch long quadraxial strips to size and attached them to top and 8 inch strips to sides of each stringer and stiffener. We wet out with epoxy and brush and rolled it out with laminating roller. A fourth strip saddled the tabs in place over the stringer.
Because these stringers are already quite high, adding knees to the transom is unnecessary (nor is there much room for them). We'll lock these tabs in place with one more layer of 24 oz 0°-90° inside the transom. This final layer will build up sufficient transom thickness for to carry the heavy outboard.
We had some time to spare with Scott and Mike before their ticket back to the Florida sun. In all, the stringer and stiffener installation took less than one business day to complete using the Preform system, not too shabby. We are extremely grateful for all their help and insight, and very impressed with the results.
The next day, with the epoxy cured dry to the touch, we rolled this old boat out into the light of day, the first time she'd seen the sun since the stringers were removed. She holds her shape with no sagging. Walking around inside the boat or rolling her over bumpy pavement, she feels rock solid, no more walking on eggshells.
Day two of the Prisma visit, and we're ready to finish up - this post we're installing the stringers. The previous day we completed the stiffener installation, and it cured hard by the time we returned the next morning. Those stiffeners installed fairly easy since it lay higher in the hull on the flats. Installing the stringers is more challenging; the stringers are closer to the keel, and span complex angles and turns up forward. Getting a flush fit can be a head scratcher. But we have a plan of attack.
Having Scott and Mike from Prisma onboard for this stage was an incredible boost. Their experience and expertise guided us easily through the process without sweating insignificant details. Together we dry fit the stringers to the hull.
The upsweep in the bow was problematic; it caused the stringers to bridge. For a perfect fit we'd need to shave the underside through trial and error, or trowel out some thickened bedding compound. Either option would eat up valuable time. But Scott reminded us the load is actually carried through the fiberglass not the foam. The foam core simply secures the fiberlass laminate shape from deflection, thus giving it exponentially more strength. A simple relief wedge cut out of each stringer gave a sufficient fit. It worked for this boat because the deck floats above the stringers not on them. The relief cut hinged the stringer with the bend to achieve adequate hull contact (though not perfectly flush.) We laid it out and everything looked shipshape. Mike hopped in the boat and TJ and I suited up to work the laminating table.
We're again using epoxy to glass in the stringers since the earlier stages were completed with epoxy also. (Polyester resin is the common go-to for this, but should only be used when bonding to a polyester based hull.) With temps in the 60° range, we're going with 105/206 slow mix to get the desirable work time. We passed the first sections into Mike and he set them in the hull. Notice the index marks on the transom for alignment. Mike kept a tape measure onhand to assure alignment.
This job is best done with several sets of hands. We wet out on the table, making sure the spun polyester backing (aka Trevira™ or Duraspun™) is completely saturated and the quadraxial cloth has a translucent soak of epoxy. We fed Mike a steady supply of epoxy so he could complete the wet out. He kept a laminating roller and chip brush on-hand, along with a healthy layer of gloves to peel away as needed. Where the stringers butt together, Mike covered the joint with 6" wide strips of quadraxial cloth.
Wood strapping and some old fashioned gravity helped tack these stringers in place while curing. Be sure to add a poly sheeting barrier to keep the wood from bonding to the stingers. We sat heavy 5 gallon pails atop the wood for pressure.
Where the deadrise (V) is steep, Mike drilled some drywall screws through the spacing planks into the stringer to keep them from sliding down.
With all the stringers set in and wet out, Mike stepped out of the Mako and hung the "do not disturb" as we stepped away. A few tie in strips to the transom will finish the job up. (included in next post)
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
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
measure the stringer distance. We left the full length 4' sections intact up forward and opted to shorten the aft stringer.
After marking the distance, cut the cloth face with a utility knife
Also cut the tabbing quadraxial cloth with scissors
Use a hand saw to cut foam
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.
Connect the dots from top corner to the measured distance
Again, cut first with the razor knife and peel away all attached fabric.
Finish the cut with a hand saw
The resulting angle should fit flush to the transom.
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.
Because these stringers are already quite high, adding knees to the transom is unnecessary (nor is there much room for them). We'll lock these tabs in place with one more layer of 24 oz 0°-90° inside the transom. This final layer will build up sufficient transom thickness for to carry the heavy outboard.
We had some time to spare with Scott and Mike before their ticket back to the Florida sun. In all, the stringer and stiffener installation took less than one business day to complete using the Preform system, not too shabby. We are extremely grateful for all their help and insight, and very impressed with the results.
The next day, with the epoxy cured dry to the touch, we rolled this old boat out into the light of day, the first time she'd seen the sun since the stringers were removed. She holds her shape with no sagging. Walking around inside the boat or rolling her over bumpy pavement, she feels rock solid, no more walking on eggshells.
