1976 Cobia Tri Hull Transom Destroyed - HELP

[eavega]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

I am not about beating a dead horse over and over again, but I'm sure by this point you know you are looking at weeks and weeks of work cutting, grinding, glassing, etc. That Cobia is almost 40 years old with tons of rotted wood, faded and spider-cracked gel, and other problems. If you are truly in love with the boat and the idea of restoring it, then I wish you luck and you can stop reading this post.

You are going to be MUCH BETTER OFF trying to find a replacement hull than trying to restore this old tri-hull. I was in the same boat (pun intended) as you a few years ago. I had a 15' Chapparal tri-hull with a rotten transom, stringers, deck. Just in materials alone, I was looking at close to $2K to restore this boat to usable conditions (resin, cloth, wood, flotation foam, paint, upholstery). I was also looking at a couple of months of work with the grinding, cutting, digging out rotted wood, glassing, painting, and then restoring the interior to a usable state. My goal was really to get on the water. I was not enamored with the little Chapparal. I decided to go hunting for a donor hull that would properly fit the motor (which was in very good shape). Lucky for me we have a boat "graveyard" close to where I live. I went out there with a hammer and drill and some tools, and came across a 1976 YarCraft Yankee (15' tri-hull) that had a blown motor but was otherwise in good shape. Solid transom, solid deck. drill sample of the stringers revealed dry shavings. I picked up the hull for $250, transferred the motor, controls, and electronics from the other boat, and I was on the water in about 3 weeks. I sold that YarCraft last year for $1500 (of course by that time I had also installed a keelshield, bimini top, and added a tach and a power port to the panel). Oh, I should add that the boat "graveyard" allowed me to dump my old hull in their yard as part of the deal.

Lesson here is that you can probably find something that will get you back on the water for a lot less time and money than doing a restoration of a 70's era tri-hull.

Good luck, either way.

Rgds

Eric

 

[gilligan2032]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

I am not about beating a dead horse over and over again, but I'm sure by this point you know you are looking at weeks and weeks of work cutting, grinding, glassing, etc. That Cobia is almost 40 years old with tons of rotted wood, faded and spider-cracked gel, and other problems. If you are truly in love with the boat and the idea of restoring it, then I wish you luck and you can stop reading this post.

You are going to be MUCH BETTER OFF trying to find a replacement hull than trying to restore this old tri-hull. I was in the same boat (pun intended) as you a few years ago. I had a 15' Chapparal tri-hull with a rotten transom, stringers, deck. Just in materials alone, I was looking at close to $2K to restore this boat to usable conditions (resin, cloth, wood, flotation foam, paint, upholstery). I was also looking at a couple of months of work with the grinding, cutting, digging out rotted wood, glassing, painting, and then restoring the interior to a usable state. My goal was really to get on the water. I was not enamored with the little Chapparal. I decided to go hunting for a donor hull that would properly fit the motor (which was in very good shape). Lucky for me we have a boat "graveyard" close to where I live. I went out there with a hammer and drill and some tools, and came across a 1976 YarCraft Yankee (15' tri-hull) that had a blown motor but was otherwise in good shape. Solid transom, solid deck. drill sample of the stringers revealed dry shavings. I picked up the hull for $250, transferred the motor, controls, and electronics from the other boat, and I was on the water in about 3 weeks. I sold that YarCraft last year for $1500 (of course by that time I had also installed a keelshield, bimini top, and added a tach and a power port to the panel). Oh, I should add that the boat "graveyard" allowed me to dump my old hull in their yard as part of the deal.

Lesson here is that you can probably find something that will get you back on the water for a lot less time and money than doing a restoration of a 70's era tri-hull.

Good luck, either way.

Rgds

Eric

Eric,

I appreciate the warning, and I agree it can't be said enough. I have the tools, the workshop etc. to do the project, and would ENJOY doing it.

I have friends with boats, and own a couple kayaks which should keep me happy enough on the water in the meantime.

Last night I was developing a strategy for removing the cap. The front of the cap, which encompasses the front seats, extends all the way to the bottom of the boat. Is this typical? The cap seems heavier than I thought, and I'm not sure that I will be able to lift it off with ~6 friends. Or am I underestimating human strength?

I was thinking I could life it off with a scaffold. I already have a swingset that I built for lifting the engine off. I would just need a scaffold extending to the back of the boat to lift off the cap evenly. What do you guys think of this?

Gilligan

 

[gilligan2032]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

I am not about beating a dead horse over and over again, but I'm sure by this point you know you are looking at weeks and weeks of work cutting, grinding, glassing, etc. That Cobia is almost 40 years old with tons of rotted wood, faded and spider-cracked gel, and other problems. If you are truly in love with the boat and the idea of restoring it, then I wish you luck and you can stop reading this post.

You are going to be MUCH BETTER OFF trying to find a replacement hull than trying to restore this old tri-hull. I was in the same boat (pun intended) as you a few years ago. I had a 15' Chapparal tri-hull with a rotten transom, stringers, deck. Just in materials alone, I was looking at close to $2K to restore this boat to usable conditions (resin, cloth, wood, flotation foam, paint, upholstery). I was also looking at a couple of months of work with the grinding, cutting, digging out rotted wood, glassing, painting, and then restoring the interior to a usable state. My goal was really to get on the water. I was not enamored with the little Chapparal. I decided to go hunting for a donor hull that would properly fit the motor (which was in very good shape). Lucky for me we have a boat "graveyard" close to where I live. I went out there with a hammer and drill and some tools, and came across a 1976 YarCraft Yankee (15' tri-hull) that had a blown motor but was otherwise in good shape. Solid transom, solid deck. drill sample of the stringers revealed dry shavings. I picked up the hull for $250, transferred the motor, controls, and electronics from the other boat, and I was on the water in about 3 weeks. I sold that YarCraft last year for $1500 (of course by that time I had also installed a keelshield, bimini top, and added a tach and a power port to the panel). Oh, I should add that the boat "graveyard" allowed me to dump my old hull in their yard as part of the deal.

Lesson here is that you can probably find something that will get you back on the water for a lot less time and money than doing a restoration of a 70's era tri-hull.

Good luck, either way.

Rgds

Eric

Eric,

I appreciate the warning, and I agree it can't be said enough. I have the tools, the workshop etc. to do the project, and would ENJOY doing it.

I have friends with boats, and own a couple kayaks which should keep me happy enough on the water in the meantime.

Last night I was developing a strategy for removing the cap. The front of the cap, which encompasses the front seats, extends all the way to the bottom of the boat. Is this typical? The cap seems heavier than I thought, and I'm not sure that I will be able to lift it off with ~6 friends. Or am I underestimating human strength?

I was thinking I could life it off with a scaffold. I already have a swingset that I built for lifting the engine off. I would just need a scaffold extending to the back of the boat to lift off the cap evenly. What do you guys think of this?

This picture shows how the cap extends all the way to the feet area of the front...

Gilligan

 

[jbcurt00]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

You will need to fully support the cap (windshield & as much console carp removed as possible) as you are pulling it free. I suspect it is still attached to the lower hull &/or deck. That's why it's seems so heavy.

It is heavy, but 6 people should be able to lift a cap enough to get some supports under it, unless it's still attached to the deck:

The front of the cap, which encompasses the front seats, extends all the way to the bottom of the boat. Is this typical? The cap seems heavier than I thought, and I'm not sure that I will be able to lift it off with ~6 friends.

I was thinking I could life it off with a scaffold. I already have a swingset that I built for lifting the engine off. I would just need a scaffold extending to the back of the boat to lift off the cap evenly. What do you guys think of this?

Gilligan

MercuryMang just got his tri-hull cap removed:

You may have to do the same.

As long as the scaffold is sufficient & sturdy, it can be a useful platform to have around:

Well yesterday I went and got some scaffolding from a friend of mine. Six units takes me up 12 feet on both sides of the boat.....here is the scaffolding that I set up last evening. You can see a 2x4 brace on the back top posts.

After a bit more work, I had both braces in place, the winches bolted down and ropes and pulleys all rigged. I went to Northern Tool and picked up 2 600 pound winches for $15.00. I used U bolts to attache them to the scaffolding. It worked like a charm!
Winch #1.

With the winches, I was able to easily lift the cap and remove the 4x4's and lower it onto the stringer in the hull.

 

[gilligan2032]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

You will need to fully support the cap (windshield & as much console carp removed as possible) as you are pulling it free. I suspect it is still attached to the lower hull &/or deck. That's why it's seems so heavy.

It is heavy, but 6 people should be able to lift a cap enough to get some supports under it, unless it's still attached to the deck:

MercuryMang just got his tri-hull cap removed:

You may have to do the same.

As long as the scaffold is sufficient & sturdy, it can be a useful platform to have around:

Thanks jbcurt,

If it is glued, is the only option cutting the front of the cap in sections as MercuryMang did?

Gilligan

 

[jbcurt00]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

You might get away w/ just cutting them free where the vertical footwell panels meet the hull/deck:

I suspect he wanted to make sure he wasn't cutting into or near the hull, so taking it apart the way he did, helped prevent slicing the hull.

If you are careful, you might be able to just trim right along the edge of the footwell deck piece and only leave the center panel he did above, but w/out those 2 'wings' sticking up in the front.

May need to fully support the console weight to keep from cracking the gunwale at the consoles. But Mercury's consoles weren't attached to the cap. I'm pretty sure he pulled the cap 1st, then the bow structure.

 

[gilligan2032]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

Today, I successfully removed the cap, by myself, in one piece! It was quite satisfying

There was one section in the rear that gave me trouble because it was glued, but I eventually got it loose. I was lucky that the front section was not glued!

I built a scaffold out of 2x4s, that extended from my previously-built swingset so I could evenly lift off the cap. I used several straps, and eased them up one by one. Is it best to store the cap upside down? Also, there is lots of foam that is sprayed to the bottom of the cap, should I remove this?

I have a Dewalt 10amp angle grinder, a full face respirator and Tyvek suit. I bought 36grit fiber discs for grinding out the old wood/fiberglass. Is this what I should use? I got started today using my crowbar

 

[gilligan2032]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

 

[jbcurt00]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

Good work. I'd get a set of sawhorses under the cap for the duration of the hull work.

 

[Jeffm602]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

Nice progress!!

 

[madman960]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

Nice. Hope to get mine to that point soon.

Bill

 

[Woodonglass]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

No need to remove the foam from the cap. Hopefully you took a lot of measurements before cap removal. Sawhorses for Cap storage. What is the Metal Piece? 36Grit is good. If you pat yourself down with Baby Powder prior to suiting up it will seal your skin pores and REALLY help keep down the itch. Especially around your neck, Forehead, and Face. Tape your Wrists and Ankles too.

 

[gilligan2032]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

Thanks for the support!

Notice the picture just above the metal piece picture, you can see where it was bolted onto the inside of the Transom to help hold the engine. I was trying to show how rusted and brittle it was... I could break it apart with my hands!

It's amazing how rotten all this wood is. The Transom consists entirely of paper-like flakes of rotten wood. I'm just scooping it out in handfuls.

 

[gilligan2032]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

I am trying to get an idea of exactly how to go about cutting out the rest of the deck. As you can see in the picture above, the original deck is still partly covering the stringers. It is very thin fiberglass over a thin rotten layer of wood. I have an angle grinder, but have never used it and have no idea how it will handle. Before I chop my toes off, I was wondering if I should be using a saw first? A circular saw or jig saw? Or should I use a cut off disc on the grinder? There are is a whole mess of options for grinding discs and I know zero about them... do I need a metal cut off disc, or a diamond one?

Right now I have these two types...

DEWALT DW8302 4-Inch by 5/8-Inch 60 Grit Zirconia Angle Grinder Flap Disc

DEWALT DARB1G0305 4.5-Inch AO Fiber Resin Disc 36G 5-pack

I also own a dremel tool, jig saw, and circular saw. Do I need a Sawzall?

 

[jbcurt00]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

No one tool is best for EVERY job. I wouldn't recommend the jigsaw for demo, as it's hard to be positive you aren't anywhere near the hull on the back side of the deck.

A circular saw will do large areas but it won't get up close to the hull because of the base plate, BUT you can set the blade depth to 1/8-1/16" less then the thickness of the fiberglass & deck (5/8"+/- usually) and cut fairly large squares of decking out fairly quick & w/out a HUGE plume of fiberglass dust. It'll throw fg dust, but not nearly as bad as a cutting or sanding disc/wheel on a grinder, IMHO.

Using a circ saw, you'd leave a lip around the edge of the hull.

But given the current state of things:

You don't have much (if any) large areas left to remove.

A grinder w/ a metal cutting disc (fiber based, & cheap, but don't last very long) or a diamond cutoff disc (metal, last a long time, expensive) will likely be best for bulk demo of what you currently have left to do. A sanding disc or flap wheel to smooth surfaces & remove the last traces of tabbing & fg lips left from material removal by other means.

A sawzall might be used to cut stringers free, but w/out seeing yours, a grinder & cutting disc might work better. Or at least less likely to cut stuff you don't intend/want to.

A firm grip and some time w/ the grinder in your hand is your best way to get familiar w/ it. Have you ever used a router? A grinder 'feels' similar when you turn it on. Just like most power tools, turn it on, let it rev up to speed & slowly apply it to the work surface. Note the arrow on the blade guard. It should be pointing the way the blade is turning when in use. And which way it will be throwing the FG dust.

If using fiberous wheels, be careful not to stress or tweak the blade while it's in use. They do fracture & at 20K+rpms the flying debris is hazardous.

 

[Woodonglass]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

I'd say your first order of business would be to remove all loose debris. Get her cleaned out! Rip out everything you can by hand first then post pics so we can see what's left. We can then give a better assessment of what tools would best suit the demo.

 

[gilligan2032]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

I looked at buying sawhorses for the cap, but they are expensive! I decided to use some 2x4s that I already had, along with some cinderblocks. Good thing there is no home owner's association in my neighborhood, because my driveway is pretty redneck right now.

I'm on the east coast, and we just got SNOW!

I used the snow day to clean out the debris, and get some good pictures. I used my crowbar, hands, and shopvac. I'm loving this 3M full face respirator I bought!

The inside skin of the transom is rather damaged, should I just remove it totally? What tool would you guys use to cut it out (if that's what I should do)?

 

[gilligan2032]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

Notice the hole in the gunwhale, it is apparently filled with green foam... not wood! Is this normal?

I screwed 2x4s into the sides of the boat where there were already holes for the cap. Then I used these boards to ratchet the boat together using those straps. This is my current anti-warping strategy. Any good?

 

[gilligan2032]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

The only parts of the transom that aren't total mushy rotten wood, are the very top sides. What's going to be the best removal strategy?

Finally, I drilled into the stringers, and the wood shavings that came out were rather dark and rotten looking. I guess there is no surprise there... (picture below)

In this picture I was comparing the stringer shavings to shavings from a dry 2x4. Quite a difference... (picture below)

I tremendously appreciate you guys helping me on this project! I'm already enjoying it.

 

[jbcurt00]

Re: 1976 Cobia Tri Hull Transom Destroyed - HELP

I'm in the middle of something else, but YES green foam in that box channel at the hull/gunwale/deck joint is 1 of the ways they meet upright & level flotation regs. NOT unusual. Foam = lite weight & glass box made a hull stiffener too.

By any means necessary, yes remove the INNER transom glass skin