Powerboat question hull/deck joint. No I am not going over to the dark side.

[Hermit Scott]

The guys that own the powder coater that I use have a ski nautique ski boat. It's about 20' with a 351 inboard. It was hit by a train so he got it pretty cheap as you could imagine. He repaired to damage but the deck started cracking. He is replacing the deck with another he found. So they drilled all the rivits out and cleaned up the mating surfaces with sanders. The new deck is dry fit into place right now. They are getting ready to use adhesive all around and then drill and rivet it back together. He has some west marine 2 part epoxy adhesive that the local west marine recommended. It comes in tubes like caulk. I have never heard anyone on here using epoxy on a hull-deck joint before.

What adhesive do you recommend on this power boat? He never plans on taking it apart again, but he didn't plan on taking it apart this time.

 

[KD3PC]

most would use Plexus or 5200, and then screw or bolt it every 14-16 inches...

best of luck...
I still have 20 12" square x 2" thick concrete tiles held on to a plywood wall with 5200 dabbed in 5 places on each tile, that my kid used for lacrosse practice back in 2005....so I don't think it will come apart

 

[alexco38]

Deck to hull joint usually use Buytl tape. They need to flex for expension and never dry out. The top expands under theu heat of the Sun faster the hull which contact with water.

Not sure 5200 is a good idea??

 

[Snotter]

They won't have enough time to rivet before the epoxy kicks.

 

[Hermit Scott]

The set time is 50 minutes in a place not as hot as hell. But we are in Texas so they may have 30 minutes. The rivets are 6" apart, but they will have multiple people drilling and riveting. They may get it done in time. I was wondering if 5200 would be better or even 4200? Like mainesail says nothing is permanent on a boat.

 

[tommays]

Lot of boats with 5200

Lot of boats like Donzi do solid glass inside after bolting and it takes a really long time to take apart when the OEM steel bow tank fails

 

[Ross]

I just glassed the joint on my Islander, inside and outside. It will never leak.

edited for syntax

 

[jibes138]

Ross makes a good point

Butyl tape would eliminate any time restriction on this installation. But why not glass the joint inside and out, it will increase the stiffness of the structure and it will most likely not leak? I would be tempted to do that. I know the Amel boat family is a solid construction where the deck is integral to the hull so there is a precedent for this kind of construction. I think my kayak is all one piece as well.

 

[jibes138]

One other thing

Make sure they have drip loops on their electrical wires. Don't let them make the mistake that MaineSail made on his new panel.

 

[BobM]

Re: One other thing

My S2 seems to have butyl tape as well as through bolts. My L25 had 5200. Reminder that neither epoxy nor 5200 like UV.

 

[Ross]

Re: One other thing

The flange for the hull/deck joint was bedded in what appeared to be plumbers putty, then pop riveted and a decorative piece of tropical hardwood used to hide the mess. The only reason to not glass it in, is the damage to the gell coat.

 

[Dan H]

Here's a radical thought.....ASK THE GUYS THAT BUILT THE BOAT IN THE FIRST PLACE!

http://www.nautiques.com/

 

[Ross]

Glassing the joint is not irreversible it just requires the use of grinders to reopen the joint. The folk that built the boat used the method that required the least labor.

 

[Chris Burti]

As the owner of a couple of Nautiques, a skier and veteran of the boat manufacturing industry, I recommend the epoxy.

This ain't your daddy's average ski boat...this is a high performance watercraft and the hull/deck joint is a critical component contributing to the integrity of the hull and the added stiffness is required by the torquing forces generated during high speed maneuvers while pulling aggressive skiers.

I would also recommend a close inspection of the stringers if this is an older hull. While, Correct Craft consistently built excellent quality boats, the glass FRP encapsulated wood stringers can prove to be a weakness, particularly if the owner stored the boats with poorly ventilated covers that effectively create a steam box environment in summer promoting rot in the wood.

 

[Hermit Scott]

As the owner of a couple of Nautiques, a skier and veteran of the boat manufacturing industry, I recommend the epoxy.

This ain't your daddy's average ski boat...this is a high performance watercraft and the hull/deck joint is a critical component contributing to the integrity of the hull and the added stiffness is required by the torquing forces generated during high speed maneuvers while pulling aggressive skiers.

I would also recommend a close inspection of the stringers if this is an older hull. While, Correct Craft consistently built excellent quality boats, the glass FRP encapsulated wood stringers can prove to be a weakness, particularly if the owner stored the boats with poorly ventilated covers that effectively create a steam box environment in summer promoting rot in the wood.

What do we look for as far as inspecting the stringers? Are we just seeing if there is any softness or rot to them?

 

[tommays]

Well

Last summer we had to gut are 1977 Correct Craft as ALL the wood strigers (4) had reached the liquid wood stage

It will show up the worst on the motor mounts

 

[Ross]

What do we look for as far as inspecting the stringers? Are we just seeing if there is any softness or rot to them?

When I have a hard shell and suspect a damaged interior on wood . Whether it be wrapped with fiberglass or is suspected of termite damage, I inspect with an 1/8 inch drill, if the interior is bad it will be like drilling into a box of breakfast cereal.

 

[Chris Burti]

What do we look for as far as inspecting the stringers? Are we just seeing if there is any softness or rot to them?

This is just a brief outline. If you are experienced in boat repair, it will be sufficient to point you in the right direction. If not, get a pro (preferably one who is knowledgeable about and understands the engineering of tournament ski boats) to help...stringers are an essential structural component and not to be treated lightly.

You can access most of the length of the stringers by removing the engine cover and pulling up the floor panel aft of it. Then, visually inspect the stringers looking for cracks or peeling glass in the layup. You are most likely to find problems, if they exist, where the aluminum engine bed is bolted through them and under the forward seats. Stick an ice pick or narrow sharp pocket knife in any cracks...any appreciable penetration is a bad sign if you hear any hollow sounds when the stringers are thumped with a small hammer/screw driver handle etc., it is a bad sign.

If you find or suspect rot after this examination, remove a flap of the glass with a dremel tool for several inches beyond the questionable area. If you find rot, you can rarely fix it as a localized repair because you are almost certainly not going to find all the rot in the stringers and it spreads like an infection. If it is really is only a localized defect, cut out the rot to clean dry wood, epoxy a wood plug in the hole, epoxy the flap back in place and add a layer of glass cloth/epoxy layup to seal the cut.

If you need to replace the stringers, try to use high density foam instead of wood if you can get it. Use epoxy, not resin, grind the whole bottom clean and use the engine bed to locate the stringers when you tack them into place. Nautiques have an inch of glass in the bottom and most of them are worth the effort to restore properly.

 

[Hermit Scott]

why is there so much water intrusion in these boats in the stringers? Is the design such that there is a lot of water sitting on the engine mounts? How is the water getting in there?

 

[Chris Burti]

why is there so much water intrusion in these boats in the stringers? Is the design such that there is a lot of water sitting on the engine mounts? How is the water getting in there?

It's a ski boat...every time I drag my fat, wet....ummm...let's just say that every time we pull the plug when loading it on the trailer we dump about 5-10 gallons of water. We also still use graphite packing in the drive and rudder shaft logs and that lets in a substantial amount of water when running hard (and it is run very hard when we ski). In the attached picture, I'm driving (you can see my hat) and the Admiral is slowing down to make a cut after passing the boat (social security hasn't slowed her down much). And we are considered the old weenies in the family...well I am anyway. It is not unheard of to get a little careless with the throttle and dive the bow through a wake when picking up a fallen skier and taking the wake over the windshield...a dry Ski Nautique is like a dry Hobie cat...it's simply not being used...

These are direct drive inboards and the engine bed is set as low as possible to both keep the center of gravity of the massive cast iron V-8 low, but also to keep the shaft angle as low as possible as well. This puts the mounting hardware in water often enough.

However, it isn't the water in the boat that is the problem nearly so much as the water in the air. Stringer rot isn't universal and boats kept uncovered in garages and boathouses are much less likely to suffer from rot than boats that are kept under unventilated covers sitting in the sun. High temps, high humidity and lack of ventilation are an excellent breeding ground for wood rot in encapsulated stringers and transoms. Since the Ski Nautique doesn't have an outboard hanging off the back, transom problems are rare. But, dropping the hammer on a 245 HP V-8 every time you pull up a skier imparts tremendous torque to the bolts in the stringers. Since the holes are not properly isolated from the wood (at least in my 1981 model, I can't fairly speak to the newer ones), water will tend to get in.