'88 Seebold 21' I/O Partial Restoration

[IslanderVT]

Getting started on replacing the gas tank, stringers, bulkheads, and deck in this boat. Its a fast hull design with a notched transom and pad keel, and has a great running Mercruiser 260 w/ Alpha drive, so its worth the trouble to get it back in shape.

Started with a cracked gas tank, which was caused by all the wood in the stringers and bulkheads around the tank being mostly rotted. This let the hull flex too much, which twisted and cracked the tank at one of the internal baffles.

Looks like this repair can be accomplished with a single sheet of plywood over the middle of the cockpit.

Original build was all plywood, and looks like an honest attempt at building a good boat. The key downfall was foaming the gas tank in place...this allowed water to sit around the tank and rotted every piece of wood in contact with it.

Rebuild will be mostly the same as factory, except no foam around the tank. Have neoprene strips I plan to glue to the hull to make stand-offs for the new tank.

Using marine plywood because the original build was done that way, and I think I can do the whole thing with 2 4x8 sheets, so cost isn't too bad.

Did not rip out the deck all the way to the hull...left an overhang enough to put in blocking under it to form cleats for the new deck to sit on.

Current status is about 1/2 done cutting out old stringers and grinding the old fiberglass from the hull. One more day on that and I should be ready to start on new wood and glass.

Couple questions:

- Original build had an air gap under all stringers and bulkheads (see pics on 2nd & 3rd post). Zero bedding that I could find. I plan to repeat this, just using PL at the ends of the stringers, and using peanut butter to form fillets (factory skipped this altogether). It is a light hull so I suspect they were worried about hard spots.

- Stringers are 1 1/2" wide, so I plan to laminate plywood with PL. Do most folks coat it with resin before laminating, or after it is one piece?

- Originally I thought this could be a simpler epoxy repair (I thought I just had delamination on the inside of the stringers), but after further ripout it needs all under-deck wood replaced. So I will be using Polyester. I had ordered some 17oz fabric w/o mat on it for expoy. I plan to use this up by covering the top and bottom of the deck with it. Does this sound OK...17oz fabric right on top of soaked plywood for protection? I'll order 1708 for the stringers and bulkheads. I've got some 10oz fabric for a finish veil that will cover the entire deck with one piece (60" wide). Flooring will be glued Vinyl (Londeck).

Here are some pictures:
Right after tank removal/cleanuo

Rotted wood in stringers and bulkheads:

Stringers rotted to powder...and this was marine plywood:

 

[IslanderVT]

Re: '88 Seebold 21' I/O Partial Restoration

No bedding in the stringer or bulkhead pockets (this is the corner shown above with the wood removed):

Is this 1708? Not shown here, but there is mat on the back side.

Is that green color just normal Polyester? All the glass in the hull is that same green after a little grinding.

Next round of pics I'll show current effort...most of the stringers and much of the wood over it is gone now.

 

[IslanderVT]

Re: '88 Seebold 21' I/O Partial Restoration

Front bulkhead...notice air gap under it. Also no presence of bedding material even on the end of the stringer. They must have held them with a fixture while they tabbed the ends in place. Makes ripout easy...the rotten wood just fell out.

This all got ripped out yesterday...

Leaving the seat mounts...they are double-thickness plywood, so I will leave them and this will let me glass them to the new stringers making them a bit stronger.

 

[IslanderVT]

Re: '88 Seebold 21' I/O Partial Restoration

Anyone have opinions on placing the stringers with an air gap under them instead of bedding?

Final drawing is done for the gas tank. If anyone need a replacement tank for this boat, RDS Aluminum (OEM) has an updated, verified drawing on file. $500 plus shipping from RDS.

 

[IslanderVT]

Bond bare wood with PL, Poly after?

Bond bare wood with PL, Poly after?

Got almost all my grinding done this weekend (nice weather for it yesterday...upper 40's...nice to not sweat in my Tyvek suit)...now I'm on to fitting up new wood.

I'll be laminating 3/4" marine plywood into 1 1/2" thickness for all the stringers and bulkheads.

I'm planning to use PL on bare wood to bond them, then coat the bonded pair with polyester. Does anyone coat their wood with polyester before gluing it?

More pics coming soon...

 

[Woodonglass]

Re: '88 Seebold 21' I/O Partial Restoration

I'd glue em up with Titebond III instead of the PL. It'll be much easier and Stronger and will ready to glass in 24 hours instead of 72. You might check the link at the top of my signature below

 

[zool]

Re: '88 Seebold 21' I/O Partial Restoration

On my 28', the factory left a 2" gap under the center bulkhead about 5' wide on a 10' beam...that bulkhead wasnt glassed and was only resin coated the bottom 12" or so....it still looks clean and solid, the rear bulkhead/firewall was bedded and glassed on the engine side, that one needs replacement..they are 3' apart.....my stringers all all bedded and glassed, so maybe there is something to that by design.

 

[IslanderVT]

Air Gap Under Stringers/Bulkheads, Pre-wrap wood before bedding?

Air Gap Under Stringers/Bulkheads, Pre-wrap wood before bedding?

Looking at the ripped out stringers and bulkheads, there was zero bedding on any of them, indicating to me that it was done by design. Seebold has a lot of experience building light boats that take a pounding (their heritage is the leading supplier of O/B Champ boats), so I suspect this is/was normal practice.

I'm planning to do the rebuild by just using PL at the ends of the stringers and spacing them off 1/4" or so from the hull. I'll be adding fillets which the factory did not use....and I can see why everyone recommends them...the stringers had several air pockets and places where the 2 layers didn't lay up very well...so we'll rebuild correctly.

With the air gap under them, I'm concerned about trapped water. Does anyone put a layer of glass on stringers/bulkheads before installing them? I'm thinking a light wrap with 3/4oz CSM would be a good idea, then 2 layers of 1708 using the Hero Move from Friscoboater...pretty sure I can do a complete wrap up and over in one pass.

 

[IslanderVT]

Re: Air Gap Under Stringers/Bulkheads, Pre-wrap wood before bedding?

Re: Air Gap Under Stringers/Bulkheads, Pre-wrap wood before bedding?

One consistent area of rot in my boat was screw holes through the deck. Plain s/s screws also tend to loosen up during rough boating.

Has anyone used threaded inserts like this, instead of just screwing right into the deck?

Brass Threaded Insert, UNC Threads, 1/4"-20 Threads, 0.50" Length, 45000 psi Tensile Strength, Made In US, Pack Of 25: Amazon.com: Industrial & Scientific

I'm thinking of using these to anchor my rear bench seat.

 

[MACn89blckstng]

Re: '88 Seebold 21' I/O Partial Restoration

Very cool man! I'm just finishing up my 265 this week! Should be in the water on Sunday! Keep up the good work on her! These boats are very unique.

 

[jigngrub]

Re: '88 Seebold 21' I/O Partial Restoration

Ah yes, it's always the evil foams fault... and maybe sometimes just a bad design by the manufacturer, but never the owners fault for letting the boat be exposed to enough water to seep through the decking (and probably unsealed deck penetrations) and accumulate in the bilge by not keeping the bilge plug pulled to rot the below deck structure... never because of that!

A properly glassed in/sealed deck would never let enough water in below deck to rot anything, and it takes a very long to of constant exposure for expanding urethane foam to saturate.

Keeping your boat covered and the bilge plug pulled when the boat isn't being used eliminates water build up in the bilge that will saturate foam and rot wood... or if your boat is wet slipped, having a mooring cover and an automatic bilge pump to pump out any water that enters the bilge will also prevent the saturation and rot.

I personally don't like the looks/idea of the stringers (especially) and bulkheads (they rarely are) not being bedded in. This more than likely left a raw unsealed edge to absorb any moisture/water that was left sitting in the bilge for any length of time, and was probably one of the biggest contributors to your rot problem.

Had your decking been properly glassed in and never penetrated by fasteners for seating or whatnot, water would've never made it into the bilge via above the decking.

A properly prepped (painted to prevent galvanic corrosion) and foamed in fuel tank will last indefinitely, and the foam will actually seal the outside of the tank to prevent leaks.

If that was my boat I'd be bedding, tabbing, and glassing in all stringers and bulkheads. I'd also install expanding urethane foam between the stringers to strengthen and support the decking and hull except for a bare keel drainway. There would also be a sealed fuel cell casket with a keel drain below so water could drain and pass below it. The new fuel cell would be etched with aluminum primer and then painted with a couple coats of metal primer and completely foamed into the sealed casket.

... but hey, that's probably just me.

 

[IslanderVT]

Re: '88 Seebold 21' I/O Partial Restoration

Yup, definitely some neglect that contributed to this rot situation. Also it had a navy blue carpet that soaked up and held water, then got hot in the sun, creating a biological wonderland under the deck. I was amazed how rotten it got...much of the wood was reduced to powder! On the other hand, wood away from the foamed tank is relatively OK. No signs of rot in the engine room or bow areas...just under the deck around the tank. Access to airflow probably helped it survive.

After all this work, I will certainly have a better eye for dryness...using all the methods you describe (pulling the plug, auto bilge pump, etc). I'm putting in a 1-piece vinyl floor so that will completely seal the deck, in addition to a seamless layer of fiberglass cloth below it.

You're exactly right about the air gap under the stringers and bulkheads. I think water probably got trapped in here and contributed to the rot. It appeared to be uncoated wood....and the wood that was covered with glass seemed to not have much resin penetration...the old glass peeled right off. I'm guessing it wasn't precoated so the wood drew resin away from the interface as it soaked in.

For the rebuild, I've already coated all the new wood in resin. I'm going to rebuild with the air gap again, but I'm covering all these exposed edges with 3/4oz mat as a water barrier. The only way to completely eliminate water under stringers is to completely bed them, and then they would be rigidly connected to the hull, which on this boat I think would surely lead to crazy cracks in the exterior gelcoat....its a light build with a thin hull. So I'm leaving it with the factory design and doing a real good job sealing the wood (and I've used true Doug Fir Marine Plywood, so that should help too).

For installing the tank, I'm not going to be foaming it in. The advice I got from RDS Aluminum, and I think its also the current guidance in ABYC, is to install the tank on rubber strips that allow airflow around the tank. AYBC recommends 1/4" strips, but I'm using 3/8" for a little larger gap. This will also add some compliance for the tank as the hull flexes. The original tank cracked because it was rigidly attached to the hull and excessive flex from the rotted wood twisted it enough to crack. So the new tank has thicker aluminum, and the rubber strips have some helpful give.

What is best practice for deck penetrations? Screw holes are where much of the deck rot started. I've ordered some brass threaded inserts (see link above) which can be sealed with 5200 on installation. This will allow me to install the seats in a way that they are easily removed without compromising the deck seal. Any other tips to avoid rot around screw holes? How about "interior" screws like the ones connecting stringers to bulkheads? This is another area of maximum rot...all the wood around the screws was completely gone.

Thanks for the advice...I appreciate it!

 

[Woodonglass]

Re: '88 Seebold 21' I/O Partial Restoration

Before you install your tank, you might want to read this...
How to Install an Aluminum Fuel Tank : Boats, Yachts - Maintenance Repair and Troubleshooting

I agree about not using foam. If you coat the tank and paint it using foam Might be OK but I'm still not convinced it's the way to go. But Hey I'm just a Dumb Okie, what do I know. I don't agree with using rubber strips and If you read the link you'll see why.

 

[IslanderVT]

Re: '88 Seebold 21' I/O Partial Restoration

Thanks for the link...I think I saw that previously but good to read it again before I button things up.

You're right about rubber...I should have said Neoprene. The strips I got are 30 durometer Neoprene that I ordered from Zoro Tools (retail arm of Grainger). The AYBC guidelines recommend 40 durometer or higher, but I like the softer stuff. Its about the firmness of a pencil eraser.

RDS mentioned the same thing...rubber has galvanic corrosion issues, Neoprene does not. My only concern with Neoprene is if the 5200 will permanently glue it down.

My only divergence from their advice is to only glue the rubber strips to the hull, not to the tank (or I suppose it could be the other way around). I'd like to not rigidly attach the tank to the hull so it has a little room to accommodate hull flex, which is where the softer Neoprene is an advantage.

Here's a link to the surprisingly affordable Neoprene strips at Zoro (I have no affiliation): Rubber Sheet/Strip-Neoprene 3/8" Thick by E JAMES & CO - Rubber Sheets and Strips by Zoro Tools Industrial Supplies

 

[Woodonglass]

Re: '88 Seebold 21' I/O Partial Restoration

Thanks for the link. Good to have for my library. That's some good stuff.

 

[IslanderVT]

Re: '88 Seebold 21' I/O Partial Restoration

Glad the link is helpful. Most sites are very expensive for this stuff...Zoro seems to have a good value...and its industrial material so hopefully will last a while.

Ever see anyone use brass inserts like this in the deck instead of plain screws? Thought these might seal around the wood better but still allow for easy interior removal without water intrusion issues.

 

[Woodonglass]

Re: '88 Seebold 21' I/O Partial Restoration

What would you want to use the inserts for? Problem I forsee is with contaminates getting into the threads etc. Lots of water on the deck at all times with all kinds of crud. Not sure how they would fair under these conditions.

 

[IslanderVT]

Re: '88 Seebold 21' I/O Partial Restoration

Woodonglass...the plan for the inserts is to use them to anchor the bench seat to the deck. Original build just used screws through the deck, and there was a lot of rot around them. I'm thinking of bonding these inserts in with 5200, then I can easily remove the seat without worrying about resealing the screws every time. Haven't tried installing one yet...might not be worth the effort.

 

[IslanderVT]

Rustoleum over Unwaxed Polyester? Primer Needed?

Rustoleum over Unwaxed Polyester? Primer Needed?

Making good progress...got my stringers fully glassed in with 2 layers of 1708 last night, using the up and over hero move from Friscoboater. Seemed to work out fine, and the glass work came out way better than the factory build. Will post update pics soon....

Planning to put down a "utility grade" paint job in the bilge under the gas tank just to seal the new fiberglass.

I'm using US Composites 435 polyester resin, which is unwaxed.

Planning to use Rustoleum with hardener for the bilge paint.

Should I roll on a layer of waxed resin, or just put the Rustoleum on the tacky unwaxed surface?

Is primer needed for a paint job that will never be seen?

 

[Woodonglass]

Re: '88 Seebold 21' I/O Partial Restoration

Yep put a coat of Wax resin on. It really aids in water proofing. Yes use primer. It aids in paint adhesion. I'd use stainless T-Nuts for the seats pre-installed prior to deck going down.