Friday, November 29, 2013

Sunfish Foam Repair

Internal foam blocks are added to fiberglass Sunfish sailboats to provide floatation and rigidity to the hull. There are 6 blocks, 3 in the bow and 3 in the stern. 2 longer blocks are offset from centerline fore and aft, and one shorter block supports the middle bow area and the other center block is placed just aft of the storage area. All of the blocks are closed cell foam that resist water penetration and they are held in place with 2 part expanding foam. Loose blocks are a problem because the hull loses its stiffness and flexes while sailing, compromising boat speed through the water. Water saturated blocks are common problems for the fiberglass Sunfish, a boat that has saturated blocks can weigh well over 200 pounds, far beyond the average 130 pound hull weight. This weight will shift the boats balance and add weight above the waterline, that contributes to capsize, not a good situation.

When we cut out a section of Merci's damaged hull to install a blind patch, we saw that the port bow foam block had come loose and would need to be reattached to the hull and deck with new 2 part expanding foam. Had we realized this beforehand we could have known we needed to split the hull/deck seam and repaired the hull from the inside.

From Small Boat Restoration

We'll be using the new work cradle for this project, as I'll need to move it in and out of the shed.

From Small Boat Restoration 2013

From Small Boat Restoration 2013

Use a 1/8 inch drill bit to remove the trim rivet head. Don't drill all the way through the bottom of the trim.

From Small Boat Restoration 2013

Use a 2x4 to tap off the trim, the broad flat surface works well and the trim won't bend around the rivet holes.



From Small Boat Restoration 2013

Start the split with an exacto knife, you'll be able to see the seam between the deck and the hull. After the split is started, you can slide in a putty knife to continue the split.

From Small Boat Restoration 2013

From Small Boat Restoration 2013

For foam block work, split the hull down the side to abeam the forward edge of the cockpit. You'll have to split the hull down both sides if you are doing both long blocks. If you are just doing one side, you'll still have to split the other side about 3 feet so there is enough slack to open the hull. Here is the inside of Merci, you can she she took on a little mud during one of the hurricanes and it sat inside for a while, staining the blocks. Eventually it dried and now there is about 4 pounds of dirt in the hull. You can also see the hole in the bow from where the bow handle ripped off, and the broken fiberglass hangar that used to hold the bow handle backer block. The center bow block is loose also. The interesting find is the padeye in the forward part of the bow, I'm going to guess that they used this at the factory to move the hull around until the deck was attached.
17 Apr 2014 Edit: This padeye was used to pull the hull out of the mold, according to Howie Picard, ALCORT employee 1960-1978.

From Small Boat Restoration 2013

From Small Boat Restoration 2013

Here is the removed center bow block.

From Small Boat Restoration 2013

From Small Boat Restoration 2013

Here is the port bow block.

From Small Boat Restoration 2013

From Small Boat Restoration 2013

Here is the failed expanding foam that was supposed to hold the blocks in place.

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Rinsed out the hull, here is a shot of the missing halyard cleat backer block and the damaged keel area that needs to be repaired. Also the halyard block backer is gone.

From Small Boat Restoration 2013

From Small Boat Restoration 2013

From Small Boat Restoration 2013

2 part, 2 pound expanding foam from Fibre Glast is suitable for marine applications. The foam mixes in equal parts, part A and part B. Mix the foam for about 1 minute, you might feel it getting warm or see it starting to expand. If so, TIME TO POUR!. Test out a small batch first, and keep in mind it expands 30 times the original volume.
Tape a paint stick to a cup to reach remote areas. Small plastic cups will come in handy for each small batch.

From SBR 2013

There is a lot of discussion on whether to pour the top or bottom of a block first. I would pour the area hardest to get to first, then work your way out of the boat. Once you pour you must clamp the hull while that batch expands and dries, 15-30 minutes, then open it back up, pour a little more, clamp, repeat. I poured the first small batch around the bottom of the starboard bow block. It looks lumpy because we pushed it under the block with a paint stick while it was expanding.

From SBR 2013

Tape the port bow block into place with a few pieces of blue painters tape, the foam will push it out of the way as it expands. Pour the bottom aft end first, it should run under the block and start expanding. Clamp the deck and let dry. To access the aft ends of the bow blocks, it might be helpful to add an INSPECTION PORT behind the splashguard.

From SBR 2013

The gap between the deck and the top of the block might be quite small. There are several options, I mixed up a batch of foam, poured it into a quart size ziploc bag, cut off a corner and squeezed foam out of the bag into the gap. Other options are to pour the top first, but it will stick to the deck and create challenges to pour the bottom. The block could also be moved back so that the gap is a little bigger on the top or bottom. Don't worry, the foam WILL expand to 30 times its volume and fill the gap!

From SBR 2013

Small cups worked great for this job, I used several of them

From SBR 2013

Lay out clamps in preparation to epoxy the seam, 30-50 will be needed.

From SBR 2013

Small strips of fiberglass cloth are cut, about an inch wide, enough to fill the seam.

From SBR 2013

Sand the inside of the deck and hull to improve adhesion.

From SBR 2013

The fiberglass cloth strips are saturated with epoxy resin and laid inside the seam. For tight areas close to where the seam is not split, fill a syringe with resin and inject it into the seam. Test a batch of resin first to know how much time you have to work with each batch. And grab a helper!

From SBR 2013

Add paint sticks along the edge, align the deck and hull and start clamping. The wood strips help spread out the clamp pressure.

From SBR 2013

Add all the clamps and let the epoxy dry for 24 hours. Once dry remove the clamps and sand off any epoxy residue.

From SBR 2013

Remove the clamps and sand the seam.

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LEAK TEST the hull.

Reinstall ALUMINUM TRIM.

Finish INSPECTION PORT installation.

From SBR 2013


Tools:
Xacto knife, putty knife, hammer, drill, drill bit, hand clamps, rivets, rivet guns, scissors

Materials:
Fibre Glast 2 part 2 pound expanding foam, paint sticks, disposable cups, sand paper, fiberglass cloth 4-6 oz, epoxy or polyester resin and hardener, tape

FMI:
Tips and technical advice:
Fibre Glast: http://www.fibreglast.com/
Facebook: Small Boat Restoration
Sailing Forum Sunfish: http://sailingforums.com/categories/the-sunfish-forum.20
Small Boat Restoration blog: http://smallboatrestoration.blogspot.com
Yahoo Sunfish_Sailor: http://groups.yahoo.com/group/sunfish_sailor

New Sunfish:
Laser Performance: http://na.laserperformance.com/sunfish/home


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