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Dumb Sunfish Foam question


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I'm fixing up an old Sunfish for my daughter.   It was rough, and waterlogged, and weighed a ton.  I've got the top and bottom halves split, and am digging out the heavy wet cruddy foam.   Originally?  It looks like the foam was installed primarily in line w/the centerline, to provide some flotation and prevent oil-canning in the middle of the deck.  It was a sloppy job.   Here's my question:   is there benefit to completely filling the hull w/foam before I glass the topsides back in place?    Second dumb question - what would be the best kind of foam to use?   My initial thoughts were to use stacked sheets of 3/4" Divinycell, filling any gaps with spray foam and shaping  to match the camber of the deck before glassing it back into place.   

I'd appreciate anyone's thoughts or "Oh no don't do that" stories. 

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Does she race?  Or do you ever intend to sell the boat?  Sunfish is a 1 design class.  I think filling it 100% with foam would not only be completely illegal, but also would make the boat CRAZY heavy.  Dry race sunfish if I remember correctly are about 120lbs.  If I had to guess, I’d say you’d be double that with foam right?  If it were me, I’d check the class rules, and put the foam back in how it was, but doing a better job then the factory did.

Did you ever find the leak?  Mine as a kid always leaked through the holes drilled for the splash guard.  It’s not hard to pop that off, seal it up and re poprivet it back on.

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41 minutes ago, sailsandsales said:

Does she race?  Or do you ever intend to sell the boat?  Sunfish is a 1 design class.  I think filling it 100% with foam would not only be completely illegal, but also would make the boat CRAZY heavy.  Dry race sunfish if I remember correctly are about 120lbs.  If I had to guess, I’d say you’d be double that with foam right?  If it were me, I’d check the class rules, and put the foam back in how it was, but doing a better job then the factory did.

Did you ever find the leak?  Mine as a kid always leaked through the holes drilled for the splash guard.  It’s not hard to pop that off, seal it up and re poprivet it back on.

1D compliance isn't a concern - I just want the boat to be light again, safe and usable.  I've cut storage cubbies fore/aft in the cockpit, got rid of the metal tube hiking straps and made a toe-well, etc.   

This particular boat leaked in several spots - hardware holes, cockpit drain, crappily repaired gunnel seam, etc.   It was cheap - it fits well on the modified jetski trailer I use to haul kayaks, and I just want to get it going while my young teenaged daughter is still exited about learning how to sail.  When she's done with it? I'll likely find someone else w/kids that want to learn, and give it to them. 

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I'd skip the foam completely.  If the oil can problem is an issue, glass in a few simple stringers.  Nothing large or fancy.  Or heavy.

It will have enough flotation to last a long time upside-down before sinking with the deck reattached.  If your cubbies are enclosed that is...

I'm in the process of converting a dumpster bound sailing dinghy to a rowboat.  Wow is it ever lighter with all the guts and foam removed. 50%?  That said, I now have zero flotation. :-/

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Since you're not sticking to one design, agreed on lightweight stringers. You have GREAT access right now. 

For flotation, take a page from the white water kayak folks, and try using simple, sturdy flotation bags... especially since you're building in storage/access cubbies.

Randii  

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It needs the foam webs to stiffen entire structure. Just stringers on deck and bottom will transfer the loads out to the next weak place that wasn't engineered to take the load, put in some sort of web to connect the skins. The foam is resilient enough to reduce hard spots that any other light web construction would have.

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I'm about to embark on this same project Ches.  This boat set me back $450 17 years ago, and endured the adventures of 2 kids who learned to sail on her. So it owes me nothing, but will be a garage fun project.

I think the original foam blocks in most of the 70s vintage sunfish (what I have) were closed cell, so the blocks aren't the problem.  It's the foam that secured the blocks in place top and bottom that soak up all the water, and can turn a 130lb hull into >200lb.  As pointed out, there are quite a number of online information sources for replacing or re-securing those blocks. And you can better anchor the deck fittings while at it.

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Before taking the hull and deck apart, cut two inspection ports in the deck and blow dry air through the interior for a few weeks.  The ESP and Urethane blow foam have 2% porosity by volume. Which means that 20 lbs of water can hide in there.   It will dry out if you set it up and give it time. Dehumidifier loops, heater# or other things all help.

SHC

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On 4/19/2019 at 11:32 AM, A guy in the Chesapeake said:

I'm fixing up an old Sunfish for my daughter.   It was rough, and waterlogged, and weighed a ton.  I've got the top and bottom halves split, and am digging out the heavy wet cruddy foam.   Originally?  It looks like the foam was installed primarily in line w/the centerline, to provide some flotation and prevent oil-canning in the middle of the deck.  It was a sloppy job.   Here's my question:   is there benefit to completely filling the hull w/foam before I glass the topsides back in place?    Second dumb question - what would be the best kind of foam to use?   My initial thoughts were to use stacked sheets of 3/4" Divinycell, filling any gaps with spray foam and shaping  to match the camber of the deck before glassing it back into place.   

I'd appreciate anyone's thoughts or "Oh no don't do that" stories. 

How's your Sunfish project going?  Your post inspired me to get mine underway. 

Last night I reached the point of opening the foredeck section of my early-70s Sunfish.  The original 3 styro blocks are waterlogged along with the fastening foam.  I know some people advocate drying them out, but who wants to waste weeks of time (and any electrical costs on heaters and the like) in order to save 50-year-old styrofoam?  I'm going to spend the $90 and install new styro blocks.  Also replace the rotten wood backing for the deck fittings with pieces of scrap hardwood.  

Of all the links to fixing waterlogged Sunfish hulls, I've found this one to be the most comprehensive:   http://kb.sunfishforum.com/images/Flotation_Blocks.pdf

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  • 2 months later...

Well - I did something stupid yesterday. Finally got some time and weather to do some more on the Sunfish.  Had it up on the sawhorses, happily cutting away, and my neighbor's pig got loose and startled me.  I turned, hit the boat, knocked it off the stands, and split the hull.   I am beginning to think I've spent as much on this as I intend to, and that it might be sawzall time, and time to look for a better hull to use my rigging on...  

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27 minutes ago, xbtaylor said:

" my neighbor's pig got loose"

 

Who among us hasn't had this happen?

Yeah but I wasn't holding a sawsall at the time!

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His wife has 3 of the PITA little Pot Belly fuggers.  Pigs ain't pets - and from what I read, the little Potbelly variants don't taste very good so I can't even enjoy turning them into sausage.   To the Sunfish?   Some friend at a lake just north of here wrecked their mast last weekend, so I'm gonna donate this boat's mast, boom, sail, rudder and centerboard to them, and we have an open invitation to use their Sunfish as we like.  My daughter tutors their youngest son, so that oughta work out nicely. 

I wonder if PotBelly pigs will eat fiberglass chunks covered w/peanut butter? 

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Chesapeake: I'd sawzall the sunfish. As others have stated, the foam is both for flotation and structural integrity of the hull. Usually two portholes (inspection ports) are fine on aluminum rail boats. One between the daggerboard trunk and splash rail and the other back at the transom, by the mainsheet bridle.

The forward hole gets you access to the inside of the daggerboard trunk and mast step. Aft hole gets you rudder bracket, mainsheet bridle fasteners and (depending on how you do it) access for aft hiking strap fasteners. 

Once you split a hull you open up a huge can of worms. Once you start hacking out foam you have basically destroyed the boat. Look for another hull. You'll spend more in spray foam cans than a new hull. When you get the new hull bring it into your garage or down into your basement with dehumidifier, cut your portholes and let it sit over the winter. Come back in the spring and fix the spots where factory foam has delamed from hull, re-glass around the daggerboard trunk, mast step and install blocks under mainsheet bridle fasteners. That'll be a solid boat. 

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  • 1 year later...

After leaving my old sunfish hull in the garage for nearly two years, I turned my attention back to it, and realized that the foam inside the hull is dry and also still fastened firmly in place. So all I need to do is chase leaks, fix and re-bed where necessary.   I am adding 2 deck hatches to access the hull fore and aft, and I want to beef up strategic places inside (under fittings, maybe around the mast step and centerboard slot).

My question is - for strengthening/leak-proofing those strategic areas, should I put a layer of epoxy on those areas on the inside?  Or go in with resin & cloth?  Any other advice?

And no, I'm not going to sawzall the hull. This is going to be a "fun" restoration project for January and February evenings after work. When it's done I will sand and re-paint it. One goal of the project is to get more hands-on experience with fiberglass and paint work so I can do better-quality DIYs on the 'big boat.'

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  • 1 month later...

The sunfish is a great project to get your feet wet on glassing and refurbing a boat.   I have used epoxy for almost all of my professional life and all of my amatuer boat building life.  That said, the sunfish doesn't require West's best.   While you can use west to fill holes and bond backers to the hull for hardware you can easily use cheaper polyester or vinylester resins.  In fact the ester based products are probably more compatible with the original layup of the hull you have.   

The resources referenced in this thread are all helpful.  the sunfish forum is great and the foam block article very helpful even if you aren't replacing them.   Its very helpful in making the splashguard waterproof knowing where those blocks are and how to get around them.  Same for working on the rudder system, etc.   Beware....some of the hard ware is screwed into wood blocks that may have become unbonded from the deck, take one screw out at a time to rebed and rescrew hardware.  Its easier than having to cut deckplate holes all over the boat....ask me how I know.

 

Good Luck!

 

 

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  • 4 weeks later...

So now I am preparing to sand and paint the old sunfish. It has very small cracks/crazing on the deck. They aren't big enough (and are too numerous) to dremel out. I was considering just using 100-120 grit paper on the oscillating sander, then using something like Total Boat's 2-part high build primer before painting it.  I think I still have a can of Interlux Brightside white that I could use as a top coat.  Is this a reasonable way to deal with the small cracking? The boat's not worth a lot, obviously, but I'd like a reasonably nice finish on it without too many hours invested.  After this it will be big-boat maintenance time.

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